Cytokines-adhesion molecules-invasive proteinases. The missing paracrine/autocrine link in embryonic implantation?

Abstract

How implantation is regulated and brought about remains an enigma. The objective of the present review is to propose a hypothetical model based on our actual knowledge of the role of cytokines, adhesion molecules and invasive proteinases in the adhesion and invasion phases of embryonic implantation. For the purpose of clarity we will describe first what is known about the presence of these molecules in the endometrium and embryo in animal models and their relevance in embryonic implantation. Secondly, since human implantation is unique the presence of these factors in the human endometrium and embryo and their possible clinical relevance is considered separately. Finally, the link between cytokines, adhesion molecules and invasive proteinases as well as their endocrine/paracrine/autocrine regulation is put forward as a possible model that could lead us to a better understanding of the implantation process in humans.

Full text

Molecular Human Reproduction vol.2 no.6 pp. 405-424, 1996
Cytokines-adhesion molecules-invasive proteinases. The missing
paracrine/autocrine link in embryonic implantation?
Carlos Simdn1-3, Maria Jose Gimeno1, Amparo Mercader1, Ana Frances1, Juan Garcia Velasco1,
Jose Remohi1, Mary Lake Polan2 and Antonio Pellicer1
1lnstituto Valenciano de Infertilidad (IVI), and Department of Pediatrics, Obstetrics and Gynecology, Valencia University
School of Medicine, Guardia Civil 23, 46020 Valencia, Spain and 2Department of Gynecology and Obstetrics, Stanford
University Medical Center, Stanford, CA, USA
^o whom correspondence should be addressed
How implantation is regulated and brought about remains an enigma. The objective of the present review is
to propose a hypothetical model based on our actual knowledge of the role of cytokines, adhesion molecules
and invasive proteinases in the adhesion and invasion phases of embryonic implantation. For the purpose of
clarity we will describe first what is known about the presence of these molecules in the endometrium and
embryo in animal models and their relevance in embryonic implantation. Secondly, since human implantation
is unique the presence of these factors in the human endometrium and embryo and their possible clinical
relevance is considered separately. Finally, the link between cytokines, adhesion molecules and invasive
proteinases as well as their endocrine/paracrine/autocrine regulation is put forward as a possible model that
could lead us to a better understanding of the implantation process in humans.
Key words: adhesion molecules/cytokines/implantation/proteinases
Introduction
Implantation is a progressive local tissue remodelling process.
The crucial role of steroid hormones in preparing the endo-
metrium for successful embryonic implantation is beyond any
doubt. However, it is becoming increasingly apparent that
another group of bioregulatory molecules (cytokines, adhesion
molecules and invasive proteinases) also play an essential role
in this process. Steroid hormones may initiate a cascade
of molecular events through these local paracrine/autocrine
effectors which account for the molecular mechanisms of this
enigmatic process.
Basic research on implantation is of great interest to clini-
cians.
Currently, embryonic implantation is the major factor
limiting or allowing fertility in humans. Therefore, the clinical
application of this basic knowledge is needed urgently.
Implantation is a complex process composed of a series of
developmental phases: apposition, adhesion and invasion. The
blastocyst and maternal endometrium must undergo an exquis-
ite dialogue during the so-called implantation window which
allows them to complete the implantation process. In the
human, it is suggested that this period begins about luteinizing
hormone (LH) day + 6 and is complete by LH day + 10
(Johannisson, 1991). Apposition, or orientation of the blasto-
cyst within the lumen of the uterus, starts on day + 6 when
the human blastocyst is 300-400 nm in diameter and the
uterine lumen is minimal due to the suction of endometrial fluid
by the pynopods (Enders, 1981). Adhesion of the blastocyst is
a progressive phenomenon that ties the embryo to the lumenal
epithelium and is the primary event initiating invasion in
mammals (Enders, 1981). Invasion is a self-controlled proteo-
lytic process that allows the embryonic trophoblast to penetrate
© European Society for Human Reproduction and Embryology
deep into the maternal decidua invading the endometrial spiral
arteries (Blankenship, 1993).
Trophoblast-endometrial adhesion phase/
cytokines
Cytokines are regulatory peptides or glycoproteins that can be
produced by virtually every nucleated cell type in the body
and they have pleiotrophic regulatory effects on haematopoietic
and many other cell types. Unlike hormones, cytokines usually
act as intercellular (paracrine) and/or intracellular (autocrine)
signals in local tissue, only occasionally spilling over into the
circulation to act as endocrine mediators (for review, see
Vilcek and Le, 1991). Human endometrium is an active site
of cytokine production and action (for review, see Tabibzadeh,
1991) and the embryo is able to communicate with the
endometrium using the same cytokine receptor language (for
review, see Chard, 1995; Sim6n et al, 1995b; 1995c;
Tabibzadeh and Babaknia, 1995a).
Here we focus on what is known about the role of three
different cytokines involved in the attachment or adhesion
phase of the implantation process. So far, the expression in
maternal endometrium of three major cytokines appears to be
essential for implantation (Figure 1). Mutations in the maternal
colony-stimulating factor-1 (CSF-1) gene in the osteopetrotic
mutant mouse compromise implantation (Pollard et al, 1991).
Also,
blastocyst implantation depends on the uterine expression
of leukaemia inhibitory factor (LIF) in mice (Stewart et al,
1992),
demonstrated by the transgenic mouse model. Finally,
our group reported that blockade of endometrial interleukin-1
receptor type I (IL-1R tl) by its natural antagonist interleukin-
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C.Simon et al.
OSTEOPETROTIC HOMOLOGOUS MOUSE (op/op)
(Pollard
etal.
1991)
TRANSGENIC MICE FOR UF GENE
(Stewart et al. 1992)
IL-1ra PREVENTS EMBRYONIC IMPLANTATION
IN MICE
(Simon
etal.
1994)
Figure 1. Diagram of the different strategies performed in order to
demonstrate the involvement of colony stimulating factor
(CSF)-1,
leukemia inhibitory factor (LIF) and interleukin (IL)-l in the
implantation process in mice. Mutations in the maternal CSF-1
gene in the osteopetrotic mutant mouse compromise implantation.
Blastocyst implantation depends on the uterine expression of LIF in
mice demonstrated by the transgenic mouse model. Blockade of
endometrial interleukin-1 receptor type I (IL-1R tl) by its natural
antagonist interleukin-1 receptor antagonist (LL-lra) prevents
implantation in mice.
1 receptor antagonist (IL-lra) prevents implantation in mice
(Simon etal., 1994a).
Colony stimulating factor-1
CSF-1,
also known as macrophage colony stimulating factor,
is a glycoprotein with a molecular weight of 50-70 kDa
synthesized from a 2.3 kb mRNA. CSF-1 was originally
described as a growth factor that stimulates the proliferation
and differentiation of the mononuclear phagocytic lineage;
however, its role in the implantation process has been clearly
demonstrated in the osteopetrotic (op/op) mouse (Pollard
et al, 1991).
In mice prior to implantation, in-situ hybridization studies
have demonstrated that
CSF-1
mRNA is confined to the uterine
epithelium (Arceci et al, 1989). During the oestrous cycle,
CSF-1 mRNA is elevated in the uterus (Sanford et al., 1992).
Also,
uterine CSF-1 concentration is elevated ~5-fold at
implantation (Bartocci et al, 1986; Pollard et al, 1987; Arceci
etal, 1989) reaching a peak > 100-fold by day 15 of pregnancy
(Arceci et al, 1989). This cytokine is also detected in the
embryo acting on the local embryonic cell population. Embryos
homozygous for the op mutation, which entirely lack
CSF-1,
develop abnormal skeletons even in heterozygous uteri (Pollard
et al, 1987).
The target cells for this cytokine, as defined by the expression
of
CSF-1
receptor (CSF-1R) mRNA, are both the embryo and
the maternal endometrium. CSF-1R mRNA is synthesized by
zygotic transcription and this pattern persists in the embryo
until implantation (Arceci et al, 1992) when CSF-1R mRNA
can be found at the ectoplacental cone and trophoblast (Arceci
et al, 1989). After implantation there is a gradation of
expression in different trophoblastic populations (Arceci et al,
1989;
Regenstreif and Rossant, 1989). The maternal decidua
surrounding the implanting embryo displays high levels of
CSF-1R mRNA (Arceci et al, 1989, 1992; Regenstreif and
Rossant, 1989). Later on, CSF-1R expression is restricted at
lower levels to the decidua basalis (Arceci et al, 1989;
Regenstreif and Rossant, 1989). Hence, CSF-1 expression in
the mouse uterus is co-incident with receptor expression in
the embryo.
Pollard et al. (1991) demonstrated the relevance of CSF-1
in implantation by the detailed study of the reproductive
behaviour of mice carrying out an inactivating mutation in the
5'-region of the CSF-1 gene. Animals homologous for this
recessive mutation, named osteopetrotic (op/op) mice, have
complete absence of systemic CSF-1 and CSF-1 mRNA is not
detected in the uterus or placenta of these animals at any stage
of pregnancy. These animals are toothless and have multiple
skeletal defects including osteopetrosis; they have a diminished
number of macrophages and are infertile. These authors propose
that CSF-1 produced by the uterine epithelium interacts with
CSF-1R present on the trophoectoderm and this dialogue
may promote blastocyst attachment. The osteopetrotic (op/op)
mutant mice have both a lower rate of implantation and fetal
viability. In these animals, both problems can be restored to
normal by administration of exogenous
CSF-1.
Interestingly,
Tartakovsky et al. (1991) demonstrated that administration of
CSF-1 to normal mice during the pre-implantation period
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Cytokines-adhesion molecules-invasive proteinases
IL1-R tl
IL-1 ra
LIF
UFR
CSF-1
CSF-1 R
IL1-R II
IL-1 ra
LJF
LIFR
CSF-1
CSF-1R
^^^^ human endometnum
' ' '•* * human emtxyo
Figure 2. Cytokines and cytokine receptors in human endometrium and preimplantation embryonic development.
inhibits implantation and reduces fetal survival. This para-
doxical effect may be due to the administration of CSF-1 at
the incorrect time and/or concentration.
Humans
A similar pattern of expression of CSF-1 is detected in the
human uterus and preimplantation embryo (Figure 2). CSF-1
mRNA encoding secreted and cell surface forms of
CSF-1
are
expressed in the uterine epithelium (Kauma et al, 1991;
Pampfer et al, 1991; Daiter et al, 1992). Furthermore, CSF-
1 mRNA and protein increase in the secretory endometrium
compared with the proliferative endometrium (Kauma et al,
1991),
reaching a peak during the first trimester of pregnancy
(Daiter et al, 1992). These results are consistent with the
reported CSF-1 mRNA expression in decidual cells in culture
(Hatayama et al, 1994; Kariya et al, 1994). CSF-1 is also
synthesized in both cyto- and intermediate trophoblast in the
first trimester and villous mesenchymal cells in the second
and third trimester (Daiter et al, 1992; Kanzaki et al, 1992).
The human preimplantation embryo presents a similar pat-
tern of CSF-1 R mRNA expression to that described for
the mouse embryo (Hawes et al, 1993) (Figure 2). After
fertilization, this oocytic mRNA is degraded to be re-synthe-
sized by zygotic transcription at the late 2-cell stage and
persists until implantation. In humans,
CSF-1 R
mRNA is also
detected in decidua from pregnant women and trophoblast
(Kauma et al, 1991; Pampfer et al, 1991; Cheung et al,
1992;
Jokhi et al, 1993; Garcia-Lloret et al, 1994). In
human trophoblast, higher levels of expression are found
in syncytiotrophoblast compared to cytotrophoblast (Pampfer
et al, 1991; Jokhi et al, 1993). Later on, in term placenta the
expression of
CSF-1 R
mRNA is restricted to syncytiotropho-
blast and Hofbauer cells (Pampfer et al, 1991; Jokhi et al,
1993).
Leukemia inhibitory factor (LIF)
LIF is a polypeptide that was described and purified, based on
its ability to induce the differentiation and suppress the
clonogenicity of the murine/monocytic leukaemia cell line,
Ml (Tartakovsky et al, 1991). Recently, it has become evident
that LIF is a pleiotropic cytokine which regulates proliferation
and in-vitro differentiation of cells from haematopoietic,
embryonic, neural, osteoblastic and endothelial lineages (Hilton
et al, 1988). In addition, this cytokine has an important role
in the implantation process.
LIF is expressed in both the pregnant uterus and the
blastocyst during the peri-implantation period. Bhatt et al
(1991) demonstrated that LIF is expressed in mouse uterine
endometrial glands, at increasing concentrations on the fourth
day of pregnancy (implantation occurs late on day 4). Further-
more, uterine LIF expression is under maternal control as
demonstrated by the same pattern of LIF expression in the
absence of implanting embryos in pseudopregnant animals
(Bhatt et al, 1991) or by the absence of uterine LIF expression
in cases of delayed implantation by either ovariectomy or
the suckling stimulus when blastocysts are floating in the
endometrial cavity (Bhatt et al, 1991). Also, LIF transcripts
have been found in the preimplantation embryo (Conquet and
Brulet, 1990; Murray et al, 1990; Bhatt et al, 1991).
Embryonic stem (ES) cells and embryonic carcinoma (EC)
cells display a number (200-330) of high-affinity LIF receptors
per cell (Williams et al, 1988), and recombinant LIF can
maintain totipotent ES cell lines that retain the potential to
form chimaeric mice (Williams et al, 1988).
Stewart et
al.
(1992) demonstrated conclusively that transient
maternal expression of
LIF
in mice is essential for implantation.
The gene encoding LIF was mutated, resulting in animals with
a truncated LIF protein lacking the carboxyterminal 81 amino
acids,
including the last nine that are essential for its biological
activity. Homozygous females lacking a functional LJF gene
are fertile, but their blastocysts fail to attach and do not develop.
However, the blastocysts are viable and when transferred to
wild-type pseudopregnant recipients, they can implant and
develop to term. These studies demonstrate that maternal
expression of LIF is essential for successful implantation. To
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C.Sim6n et al.
further prove this theory, Stewart et al. (1992) overcame the
LIF deficiency in transgenic animals with exogenous LIF.
These authors implanted a micro-osmotic pump that delivers
recombinant LIF in the peritoneal cavity of homozygous
females. Pumps were implanted at day 3 of pregnancy and
these animals had observable implantation sites at day 6 of
pregnancy.
Humans
In human endometrium (Figure 2), LIF is expressed throughout
the menstrual cycle with a significant increase in the LIF
mRNA (Charnock-Jones et al, 1994; Arid et al, 1995) and
protein concentrations (Charnock-Jones et al, 1994) in the
mid- and late-secretory phase samples. Northern blot analysis
of endometrial glandular and stromal cells (Arici et al,
1995) and quantitative polymerase chain reaction (PCR) from
epithelial and stromal fractions of the endometrium (Kojima
et al, 1994) demonstrated that expression of LIF mRNA is
more abundant in the epithelial fraction. These findings are
consistent with the detection of LIF protein primarily in the
glandular epithelium in the secretory endometrium (Charnock-
Jones et al, 1994). Interestingly, steroid hormones (oestradiol
and progesterone) do not have any regulatory effects on LIF
mRNA expression or protein production by endometrial cells
in culture (Arici et al, 1995). However, IL-1, tumour necrosis
factor (TNF)-a, platelet-derived growth factor (PDGF),
epidermal growth factor (EGF) and transforming growth factor
(TGF)-a are potent inducers of LIF expression in endometrial
stromal cells in a concentration- and time-dependent manner,
whereas interferon-y inhibited LIF expression induced by these
cytokines (Arici et al, 1995). LIF mRNA is also present in
decidua (Arici et al, 1995) and placenta (Kojima et al, 1994)
of the first trimester of pregnancy but concentrations were
lower than those found in the secretory phase (Arici et al,
1995).
These findings taken together indicate that endometrial
LIF expression is not dependent on the presence of pregnancy
and is under maternal control. At the feto-maternal interface,
only cytotrophoblasts are positively stained by the anti-LIF
monoclonal antibody (Sawai et al, 1995). Furthermore, LIF
induces human chorionic gonadotrophin (HCG) production by
trophoblasts in the first trimester (Sawai et al, 1995).
Reverse transcription (RT)-PCR from human blastocysts
shows the presence of LIF receptor mRNA (Chamock-Jones
et al, 1994) suggesting that they may be capable of responding
to LIF stimulus at the appropriate timing for implantation.
The interleukin-1 system
IL-1 is a family of peptides comprised of
IL-1
a (159 amino
acids),
IL-ip (153 amino acids) and an inhibitor, IL-1 receptor
antagonist (TL-lra), a 152 amino acid peptide which shows a
striking similarity to
IL-1
a and IL-lp molecules (for review
see Dinarello, 1988). Two IL-1 receptors have been identified
and characterized: IL-1R type I (IL-1R tl) (Sims et al, 1988)
and IL-1R type II (IL-1R tU) (Horuk & McCubrey, 1989).
The available information indicates that IL-1 R til is not
functional and IL-1 signalling occurs exclusively via type I
receptors (Sims et al, 1993). IL-1R tl recognizes both ligands,
IL-1 a and IL-ip, and triggers similar responses in target cells
(Dower et al, 1986). IL-lra binds to the same receptor,
408
preventing many physiological responses attributed to IL-1R
tl activation in vitro and in vivo, such as prostaglandin (PG)
E2 induction and collagenase production by preventing signal
transduction of IL-1R tl (Cominelli et al, 1990; Hannum
et al, 1990; Ohlsson et al, 1990).
In mouse endometrium, IL-1P and
IL-1
a have been localized
at the mRNA level to endometrial macrophages and endothelial
cells (Tackacs et al, 1988). Furthermore, IL-ip and IL-lot
mRNAs and IL-1 bioactivity in the peri-implantation uterus
are known to increase from day 3 of pregnancy and peak
between days 4 and 5 in the presence (De et al, 1993) or in
the absence of embryos in the endometrial cavity (Choudhuri
and Wood, 1993) suggesting that maternal endometrial IL-1
is hormonally regulated regardless of the presence of embryos.
IL-1 is released by mouse placental macrophages (Flynn
et al, 1982; Flynn, 1984). More recently IL-ip staining has
been localized in mouse placenta (Sim6n et al, 1994a).
Immunoreactive IL-ip and
IL-1
a are also present in the
placenta of viviparous reptiles such as Chalcides calchides
(Paulesuef a/., 1995).
Immunoreactive IL-1R tl is located in mouse endometrial
lumenal epithelium with increased intensity in the peri-
implantation period (Sim6n et al, 1994a). After implantation,
IL-1R tl is present in both maternal decidua and placenta
(Sim6n et al, 1994a).
To test the hypothesis that blocking IL-1R tl prevents
implantation, we blocked IL-1R tl signal transduction in the
mouse with its antagonist human recombinant IL-lra (Sim6n
et al, 1994a). In the mouse and human, IL-1 actions such as
hypoglycaemia, induction of interleukin-6 (IL-6), and cortico-
sterone production can be blocked in vivo by administration
of IL-lra (Mengozzi et al, 1991). Pregnant mare's serum
gonadotrophin (PMSG)/HCG-stimulated 12 week old B6C3F-
1 females were injected i.p. with 20 \ig of recombinant human
IL-lra (rh IL-lra) every 12 h beginning on pregnancy day 3
until day 9 and were then killed 12 h after the last injection.
Pregnancy rates, as assessed by the presence of implantation
sites in either uterine horn were: non-injected 58.8% (10 out
of 17); buffer-injected 73.7% (14 out of 19); rh IL-lra injected
6.7% (one out of
15).
To
eliminate the possibility that pregnancy
failure was due to a toxic effect of rh IL-lra on preimplantation
embryonic development, 2-cell mouse embryos from the same
group of animals used for in-vivo experiments were cultured
with increasing concentrations of rh IL-lra for 3 days, as
previously described (Sim6n et al, 1992). After 72 h in culture
the percentage of 2-cell mouse embryos reaching the blastocyst
stage was 85.7% (0 ug/ml), 91.6% (1 ^g/ml), 94.4% (50 u,g/
ml),
96% (100 Ug/ml) and 85.2% (200 |ig/ml) respectively,
suggesting that rhlL-lra is not toxic to preimplantation murine
embryonic development. To investigate the effect of the rh
IL-lra on blastocyst hatching, trophoblast outgrowth and
migration, we further cultured these blastocysts for 5 days on
fibronectin-coated plates (Sherman, 1988). Outgrowth and
migration were demonstrated to be similar in the presence or
absence of rh IL-lra. Finally, a morphological longitudinal
study was carried out to determine the progress of embryonic
implantation in the mouse between pregnancy days 4-9 in
control, untreated animals compared with rh IL-lra-treated
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Cytokines-adhesion molecules-invasive proteinases
animals. As shown in Figure 3, at day 4 in the normal
pregnancy the free blastocyst is located within the lumen of
the uterus (Figure 3A). By days 7 and 9 (Figures 3C and E
respectively) the mouse embryo is completely implanted in
the stroma. In the IL-lra treated animals, the free blastocyst
is also within the uterus by day 4. (Figure 3B). By day 7 the
embryo has neither attached nor implanted (Figure 3D). By
day 9, the histological findings in the only pregnant mouse
injected with rh IL-1 ra revealed the existence of intact glandular
epithelium with a stromal decidual reaction beneath them and
degenerated trophoblastic cells in the uterine lumen; attachment
is not documented and no stromally implanted embryos were
found (see Figure 3F).
Humans
In human endometrium (Figure 2), IL-ip mRNA expression
appears in the mid-luteal phase (Kauma et al, 1990). IL-1P and
IL-la have been localized at the protein level to endometrial
macrophages and endothelial cells (Simon et al, 1993a),
although their presence has also been reported to be ubiquit-
ousely present in epithelium, stroma and endothelial cells
(Tabibzadeh and Sun, 1992b).
EL-1 receptor type I (IL-1R tl) is expressed at the mRNA
level in the human endometrium throughout the menstrual
cycle, reaching maximal concentrations in the early and late
luteal phases (Sim6n et al, 1993b). More specifically, IL-1R
tl mRNA is expressed in the human endometrial epithelium,
at increased levels during the luteal phase (Sim6n et al,
1993a). These endometrial epithelial cells exhibit IL-1 binding
sites (Tabibzadeh et al, 1990), and immunoreactive IL-1R tl
(Sim6n et al, 1993a).
It has been demonstrated in vitro that IL-1 can exert some
endometrial functions including the induction of IL-6 secretion
by human endometrial stromal cells (Tabibzadeh et al, 1989),
the stimulation of PGE2 production (Tabibzadeh et al, 1990;
Sim6n et al, 1994a) and the induction of IL-6 production by
endometrial epithelial cells in culture (Laird et al, 1994).
Nonetheless, IL-1 inhibits in-vitro decidualization of human
endometrial stromal cells as measured by progesterone-stimu-
lated prolactin production in a dose-dependent manner (Kariya
et al, 1991; Inoue et al, 1994) and cAMP-mediated prolactin
production (Inoue et al, 1994). Also, IL-1 is able to inhibit
the synthesis and release of renin from human decidual cells
(Jikihara et al, 1995). Unlike its action in fibroblasts which
proliferate when exposed to IL-1 (Raines et al, 1989), this
cytokine is a potent inhibitor of normal human endometrial
stromal cell growth (van Le et al, 1992), suggesting that its
action may contribute to the homeostasis in normal endo-
metrium. Indeed, the secretion of IL-la by endometrial epithe-
lial cells induces PGE2 and PGF^ secretion by endometrial
stromal cells in vitro (Jacobs and Carson, 1993). Therefore the
presence, tissue-specific localization, cycle-dependent changes
and functions of the IL-1 system in the human endometrium
indicate a putative autocrine/paracrine/intracrine action which
may be relevant for decidualization and implantation.
Although the selective localization of IL-lra in eutopic
endometrium has already been described (Tabibzadeh and Sun,
1992b; Sahakian et al, 1993), in order to complete our
understanding of the entire endometrial IL-1 system in humans,
we have investigated the immunohistochemical distribution
of interleukin-1 receptor antagonist (IL-lra) in the human
endometrium throughout the menstrual cycle (Sim6n et al,
1995a). Immunoreactive IL-lra was present throughout the
entire menstrual cycle, located primarily in the endometrial
epithelium. However, IL-lra staining was significantly higher
during follicular phase in comparison to early and mid-late
luteal phases. RT-PCR from cultured stromal and glandular
cells shows that these cells express the intracellular form of
IL-lra (ic IL-lra). Our results demonstrate the regulated
presence of the ic IL-lra in the human endometrium (Sim6n
et al, 1995a).
Production and secretion of IL-1 by human embryos is still
under discussion. Several authors have detected the presence
of bioactive and/or immunoreactive IL-la and IL-ip during
in-vitro fertilization (TVF) in embryo-conditioned media from
day 1 and day 2 by the human preimplantation embryo (Zolti
et al, 1991; Sheth et al, 1991; Barafiao et al, 1992; Tarlatzis
et al, 1994; Austgulen et al, 1995) whereas other authors
have failed to detect any measurable amounts of IL-la in
human embryo growth media (Hardy et al, 1993; Seifer
et al, 1993). Some authors indicate that IL-la concentrations
decrease on the second day of culture compared with the first
day (Sheth et al, 1991; Austgulen et al, 1995), whereas
Tarlatzis et al. (1994) have shown an increase in the IL-la
concentrations at day 2. No direct correlation has been found
between IL-la production by the human embryo and embry-
onic quality (Austgulen et al, 1995). However, several authors
have proposed that high concentrations of IL-la and IL-ip
(>60 pg/ml and >80 pg/ml respectively) in media from
cultured embryos correlate with successful implantation in
patients undergoing IVF (Sheth et al, 1991; Baraflao et al,
1992;
Tarlatzis et al, 1994).
To address this issue, we have localized the complete IL-1
system at the protein level in the human embryo and we have
investigated factors influencing the secretion of this cytokine
during embryonic development (De los Santos et al, 1996).
Immunostaining for IL-ip, IL-ra and IL-1 R tl was confirmed
in oocytes and embryos in all preimplantational developmental
stages. IL-la and FL-ip were absent in conditioned media of
cultured embryos under routine IVF conditions as well as in
embryos co-cultured with human endometrial stromal cells
(ESC).
However, when single human embryos were co-cultured
with human endometrial epithelial cells (EEC), two different
populations of embryos were observed: IL-1 producers (n =
13) (IL-la, 1.5 ± 0.6 pg/ml; IL-ip, 7.1 ± 1.8 pg/ml; EL-lra,
87.9 ± 37.5 pg/ml) and IL-1 non-producers (n = 10) (0/0/0).
Interestingly, embryos cultured with EEC-conditioned medium
alone showed similar IL-1 producer and IL-1 non-producer
populations (De los Santos et al, 19%). These results demon-
strate the presence of the complete IL-1 system in the human
embryo. It is noteworthy that the selective release of
IL-1
only
when embryos were co-cultured with EEC or EEC-conditioned
media indicates an obligate role of the endometrial epithelium
in the regulation of the embryonic IL-1 system.
The immunolocalization of the IL-1 system in early human
implantation sites (Hu et al, 1992; Simon et al, 1994b)
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C.Simon et al.
CONTROL NON-INJECTEDIL-lra INJECTED
Figure 3. Morphological study of the progress of blastocyst implantation in mouse pregnancy in control untreated (A, C, E) versus rh IL-
lra treated animals (B, D, F). (A) Day 4 normal pregnancy; longitudinal section of a free blastocyst surrounded by enlarged uterine lumenal
epithelial cells [haematoxylin/eosin (H & E), original magnification X400]. (B) Day 4 pregnant animals injected with rh IL-lra; cross-
section of a free blastocyst. Notice the surrounding epithelium is not enlarged as observed with normal pregnancy (H & E X400). (C)
Uterus of day 7 normal pregnant mouse; longitudinal section through embryo and decidual mass demonstrating complete stromal
implantation (H & E X400). (D) Uterus of day 7 pregnant mouse, rh IL-lra injected; notice that the blastocysts are still free and neither
attachment nor invasion is documented (H & E X400). (E) Uterus of day 9 normal pregnant mouse; longitudinal section through stromally
implanted embryo and decidual mass (H & E X200). (F) Uterus of day 9 pregnancy, rh IL-lra injected mouse; stromal decidual reaction
(arrows) with intact glandular epithelium and degenerated trophoblastic cells in the uterine lumen (arrowhead) can be observed; implantation
did not occur in this animal (H & E X800). (Reproduced with permission from Simon et al, 1994a.)
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Cytokines-adhesion molecules-invasive proteinases
reveals that immunostaining for IL-1R tl is present in the
syncytiotrophoblast, and hyperplastic endometrial glands in
the maternal decidua. Immunoreactive IL-1(5 was present in the
villous cytotrophoblast and syncytiotrophoblast, intermediate
trophoblast, and maternal stromal decidual
cells.
IL-1
ra staining
was observed in the glandular endometrium of the maternal
decidua and in isolated cells located inside the chorionic villi,
in the intervillous space, and maternal decidua. These results
show the shared presence in maternal and embryonic tissues
of this receptor-agonist-antagonist system during early human
implantation, supporting an autocrine/paracrine role for the
IL-1 system in human implantation.
The immunolocalization of IL-1R tl in the syncytiotropho-
blast (ST) is in agreement with the demonstrated stimulatory
effect of IL-1 on HCG release from human first trimester
trophoblast cells in culture (Yagel et al, 1989; Masuhiro et al,
1991;
Steelee et ai, 1992). This relationship further suggests
that IL-1 may exert paracrine/autocrine regulatory effects on
HCG secretion by the stimulation of
IL-1 R
tl located in ST.
Further inhibitory experiments are needed to clarify this point.
Finally, a clinical study in normal human subjects injected
with human recombinant IL-lra has shown that increasing
plasma concentrations of IL-lra to 25-30 ng/ml caused no
symptoms or changes in vital signs, and did not alter white-
cell counts or routine biochemical and endocrinologic findings
(Granowitz et al, 1992). This, as well as the fact that these
elevated IL-lra plasma concentrations had no deleterious
effects on immune response (Granowitz et al, 1992), opens the
possibility of a specific, immune anti-implantation technology.
Trophoblast-endometrial adhesion and invasion
phases/adhesion molecules
Adhesion molecules are proteins involved in cell-surface-
mediated processes essential for normal morphogenesis and
for the maintenance of tissue integrity in multicellular organ-
isms.
Cell binding to the extracellular matrix triggers signals
that greatly influence behaviour patterns of migration, prolifera-
tion and differentiation. The available information indicates
that the most relevant trophoblast-uterine adhesion molecules
are:
integrins heterodimers, selectins and proteoglycans. The
primary function of integrins is to mediate the cellular binding
to extracellular matrix (ECM) proteins by means of specialized
cell attachment sites such as the tripeptide sequence Arg-Gly-
Asp (tripeptide RGD) which is the target sequence for the
integrin binding (Ruoslahti and Pierschbacher, 1987). Evidence
for the role of
the
RGD sequence is derived from the fabrication
of smaller fragments of ECM proteins which can promote
cell adhesion, or from the construction of synthetic peptides
containing the RGD sequence that will also compete with
ECM proteins for their receptors (Burrows et al., 1995).
The selectins are the most recently identified family of cell
adhesion molecules (Vestweber, 1992). Three members of this
family have been identified: L- (homing receptor), E- (ELAM
or endothelial leukocyte adhesion molecule) and P-selectins
(GMP 140, granule membrane protein of molecular weight
140 kDa or PADGEM, platelet activation-dependent granule
external membrane protein) which are all involved in the initial
adhesion of leukocytes to endothelial cells (for details see
Lasky, 1992). All three selectins have an extracellular domain,
a transmembrane segment and a cytoplasmic tail. The extra-
cellular domain structure contains a lectin-binding domain, an
epidermal growth factor (EGF)
motif,
and several complement-
ary regulatory sequence repeats (Bevilaqua et al, 1989;
Springer, 1990, Lasky, 1992). The trisaccharide sialic acid
(NeuNAc), galactose (Gal) and fucose (Fuc) have been shown
to be critical for ligand binding of E-, P- and L-selectins (Berg
et ai, 1991). It appears that this carbohydrate recognition may
be analogous to the binding of integrin to the RGD sequence.
The main ligands recognized by selectins are: (i) sialyl
lewis\
this carbohydrate is recognized by E- and P-selectins
(Tiemeyer et al, 1991; Polley et al, 1991; Dejana et al,
1992;
Foxall et al, 1992; Lasky, 1992); (ii) sialyl lewisa, this
polysaccharide has ligand activity for E-selectin. Both the
sialyl lewis" and sialyl lewis' carbohydrates have sequence
recognition and many conformational similarities (Berg
etal, 1991).
The function of selectins is to mediate cellular recognition
of carbohydrate ligands. Their distribution is mainly in haema-
topoietic or vascular endothelial cells. Surface membranes also
have proteoglycans, including syndecan and CD44 molecules
as mediators of ECM recognition (Cannistra et ai, 1993).
The immunoglobulin superfamily (Ig-SF) encompass a vari-
ety of molecules that share a common structural feature. This
consists of 70-110 amino acids organized into 7-9 P-pleated
sheets. Each unit is stabilized by permanent disulphide bridges
formed between two of the strands (Albelda, 1993). Most
members of the Ig-SF are involved in cell-cell recognition
(Williams et ai, 1988) and include: (i) molecules that function
in cellular immunity (major histocompatibility antigens, CD4,
CD8,
the T cell receptor); (ii) neural development (neural
cell adhesion molecule (NCAM); (iii) leukocyte trafficking
[intercellular adhesion molecule (ICAM-1), vascular cellular
adhesion molecule (VCAM-1), platelet endothelial cellular
adhesion molecule (PECAM-1)]; (iv) signal transduction
[colony-stimulating factor-1 receptor (CSF-1R), platelet-
derived growth factor receptor (PDGF-R)].
Integrins are one of the most relevant families of adhesion
molecules in embryo development and implantation and they
will be the main topic of this section. Integrins are membrane
glycoproteins composed of two subunits (a and (3) forming
homologous groups. The similarity at the amino acid sequence
level between the a and p* subunits is 40-50% (Ruoslahti,
1991a). Both integrin subunits have a large extracellular
domain, a transmembrane segment and a cytoplasmic tail. The
integrin cytoplasmic domain interacts with components of the
cytoskeleton allowing integrins to provide a link between the
cytoskeleton and the extracellular matrix (Hynes, 1987; Hynes,
1992;
Sastry et al, 1993). All the a-subunits contain a
segment that probably contributes to the divalent cation-
binding properties of these subunits. Divalent cations are
essential for receptor function (for details see Hynes et al,
1992).
A total of 15 a- and 8 fi-integrin subunits are known.
These subunits are associated forming different heterodimer
complexes (Figure 4). The diversity of integrins is further
411
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C.Simbn et al.
B7 a4 o5 a$
a
ax ~~~~^~ f»
M
2 aL
Figure 4. There are three main groups of integrins with a
predominant subunit in each one: a^ P, and f^. The combination
of two subunits make a heterodimer (integrin). The possible
combinations are indicated by lines.
extended because a single cc-subunit can pair with more than
one P-subunit. This property provides cells with a number of
possibilities of recognizing different adhesive substrates, a^
(OE
chain is also called
OH
„ a]EL) and (X4P7 are the most
recently described integrins in intercellular binding; their
expression is restricted to leukocytes (Tiisala et al, 1995) and
is relevant in lymphocyte rolling and attachment (Berlin
et al, 1995).
The tripeptide RGD is the recognition site for many of the
integrins binding to extracellular matrix (Pierschbacher and
Ruoslahti, 1984; Hynes, 1992; KUhn and Eble, 1994). The RGD
sequence is also the cell recognition trigger for fibronectin,
vitronectin, collagens, fibrinogen, von Willebrand factor, osteo-
pontin, bone sialoprotein I, thrombospondin, tenascin, laminin
and entactin (Ruoslahti and Pierschbacher, 1987; Ruoslahti,
1991b). The specificity of recognition for each integrin depends
upon flanking RGD sequences that are not identical, resulting
in different conformations of the protein (Ruoslahti, 1991a).
Besides the RGD sequence, other binding sites have also been
identified, such as the EILDV sequence which is the target
sequence for the (X4P7 integrin (Ruegg et al, 1992).
The existence of an integrin-mediated signal transduction
pathway involves the protein lppl25 Focal Adhesion Kinase'
(Juliano and Haskill,
1993;
Schaller and Parsons 1994; Burrows
et al, 1995). Studies on OvP3 and o^ps in adenovirus infection
indicate that action is through a viral coat protein called a
penton base containing five RGD units. This work suggests
that in addition to their main function of attachment, integrins
may function as receptors for internalization (Wickham et al.,
1993;
Taskin et al, 1994). The main ligand species recognized
by integrins are (see Table I):
Fibronectin
Fibronectin is recognized by
OJPI
(Pytela et al, 1985),
CX4P1;
(X3P1 (Wayner and Carter, 1987; Hemler, 1990), O^P, (Vogel
et al, 1990), 0^3 (Ruoslahti, 1991b), afa (Ruegg et al,
1992;
Postigo et al, 1993) and anbp3; OvP6 (Ruoslahti et al,
1994),
OvPg (Weinacker, et al, 1994).
Collagen
The collagen binding integrins are
(X1P1;
a3Pi
(Wayner and
Carter, 1987; Staatz et al, 1989; Ignatius et al, 1990) and
cc2Pi (Elices & Hemler, 1989; Languino etal, 1989; Kirchhofer
et al, 1990) . There are many RGD sequences in collagens,
but most of the collagen-mediated cell attachments are not
RGD-dependent.
VHronectin
Integrins that bind to vitronectin are
OvP3
(Pytela et al, 1985b),
(Pytela et al, 1986), O^P, (Bodary and McLean, 1990),
(Smith et al, 1990) and Ovp6 (Sheppard et al, 1990).
b exists on macrophages (Krissansen et al, 1990) and
OvPuon the surface of embryonic fibroblasts (Bates etal, 1991).
The Oy-subunit binds to vitronectin, osteopontin, bone alalo-
protein I, fibrinogen, von Willebrand's factor and thrombospon-
din (Cheresh, 1987; Reinholt et al, 1990). Each of these
molecules has an RGD sequence. This subunit also shows
some affinity for fibronectin (Pytela et al, 1985a; Smith et al,
1990).
Immunoprecipitation studies with antibodies raised
against the Oy subunit indicate that OvPi complex is the
predominant vitronectin receptor (Bodary and McLean, 1990).
Laminin
Laminin is a protein with three subunits (A, Bl and B2).
There are six integrins that bind to laminin; CX|P|, a2pi, a3p:,
OeP,,
a7Pi
and 0^4 (Lotz et al, 1990), o^P, being the main
laminin receptor (Sorokin et al, 1990).
Tenascin
The main integrin that binds to tenascin is OC9P1 (Yokosaki
et al, 1994).
Fibrinogen
Four integrins are associated with fibrinogen:
1991b), 0^2 (Nishimura et al, 1994), a
(Ruoslahti et al, 1994).
(Ruoslahti,
and allbP3
Von Willebrand's Factor
This factor is recognized by rxvp3 (Ruoslahti, 1991b) and
(Ruoslahti et al, 1994).
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Cytokines-adhesion molecules-invasive proteinases
Table I. Integnn
Receptors
ligands and
Ligands
FN
their receptors
Col VNLNTNFbvWFOpbs-1ccc3biFXICAMVCAM
OlPl
o,p.
+ + + +
FN = fibronectin; Col = collagen; VN = vitronectin; LN = laminin; Tn = tenascin; Fb = fibrinogen; vWF = von Willebrand Factor, Op = osteopontin;
bs-1 = bone sia!oprotein-l; ccc3bi = complement component c3bi; FX = factor X; ICAM = intercellular adhesion molecule; VACM = vascular cellular
adhesion molecule.
Osteopontin and bone sialoprotein-1
OvP3 is the integnn associated with these ligands (Ruoslahti,
1991b).
Complement component C3bi and Factor X (FX)
a&t (Nishimura et al, 1994) and aMp2 (Ruoslahti et al,
1994) bind to C3bi, while aMP2 bm<k to FX (Ruoslahti
etal, 1994).
Intercellular adhesion molecules (ICAM)
aMP2 recognizes ICAM-1 and aj^ recognizes ICAM-1 and
ICAM-2 (Ruoslahti et al, 1994).
Vascular cell adhesion molecules (VCAM)
OC4P7 and OtP, (Laudanna et al, 1996) can bind to VCAM-1
(Ruoslahti etal, 1994).
There are integrins without known specific adhesion sub-
strates, such as the fjtgPi heterodimer (Bossy et al, 1991)
which binds to basal lamina in chicken.
Other molecules involved in cell adhesion include cadherins.
These molecules are calcium-dependent transmembrane glyco-
proteins responsible for cytoskeletal organization that mediate
adhesion between cells that express the same cadherin (homo-
phylic cell-cell interaction) (Takeichi, 1988). Three types of
cadherin have been described: E- (also called
Arc-1,
uvo-
morulin and cell-CAM 120/80), P- and N-cadherin (Takeichi,
1991).
E-cadherin is expressed in proliferating epithelial cells
derived from the ectoderm and endoderm, the P-cadherins
found primarily in placenta and epithelium and the N-cadherins
present in adult neural tissues and muscle (for detail see
Albelda, 1993).
Adhesion molecules in the human endometrium
During the menstrual cycle (Figure 5) a2, a3, (X5, a« (Lessey
etal, 1992; 1994a; 1995; Tabibzadeh, 1992), p4 (Lessey etal,
1992;
1994a; Lessey and Castelbaum, 1995),
Ov
and P, (Lessey
et al, 1994a; Lessey and Castelbaum, 1995) are expressed in
the proliferative endometrium, specifically in the epithelial
endometrium. In the stromal component, 05, 0^ (Lessey et al,
1992,1994a; Tabibzadeh, 1992; Lessey and Castelbaum, 1995),
Ov, p3 (Lessey et al, 1992, 1994a; Lessey and Castelbaum,
1995),
04, Pi (Tabibzadeh, 1992; Lessey et al, 1994a; Lessey
and Castelbaum, 1995) and a,, a3 (Lessey et al, 1994a;
Lessey and Castelbaum, 1995) are present.
In the secretory phase (Figure 5) a,, a2, a3, 0^,
(Xy,
p3 p4,
(Lessey et al, 1992, 1994a; Lessey and Castelbaum, 1995),
Pi (Tabibzadeh, 1992; Lessey et al, 1994a; Lessey and
Castelbaum, 1995), 04 (Lessey et al, 1994a; Lessey and
Castelbaum, 1995) and 05 (Tabibzadeh, 1992; Lessey et al,
1994a) are present at the epithelial endometrium. The following
adhesion molecules have been described in the stromal com-
partment: CX|, cc3, (X),
CC5,
Oft, Oy, p|, P3 (Lessey et al, 1992,
1994a; Tabibzadeh, 1992; Lessey and Castelbaum, 1995).
A loss of normal 0CvP3 expression is associated with endo-
metriosis, and defective endometrial P3 expression has been
found in nulliparous women with documented pelvic endo-
metriosis (Lessey et al, 1994b). Unexplained infertility may be
associated with unrecognized endometnosis and/or abnormal
receptivity. In patients with unexplained infertility, alterations
in the endometrial integrin pattern have also been identified
(Lessey et al, 1994b).
E- and P-cadherin expression was found in the glandular
epithelium throughout the menstrual cycle and no changes
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C.Simdn et
al.
al
a2
a3
a4
a5
a6
av
PI
P3
P4
Human endometrfal epithelial cefis
Early
P
phase
Md
P
phase
Late
P
plus*
Early
S
phase
Md
S
ph>M
Lite
S
phase
•*^™
BHMa:
Human endometnal stromal cells
Early
p
phase
Md
P
phase
Late
P
phase
Early
S
phasa
Md
S
phasa
Late
S
phasa
Figure 5. Cell adhesion molecules expression on human endometnum throughout the menstrual cycle.
P=
proliferative,
S=
secretory.
were demonstrated
in
patients with endometriosis
(van der
Linden
et al,
1995). Endometrial changes
in the
secretory
phase result
in
decidualization. This occurs
in
the presence of
ot|Pi, ct3Pi integrins (Korhonen et
al,
1991). Decidual stromal
cells also secrete
a
thick layer
of
pericellular laminin, which
is probably hormonally controlled
and
coincident with
implantation (Loke et
al,
1989). Type VI collagen is present as
a dense microfibrillar network in the stroma of preimplantation
endometrium
but is no
longer detectable
in
first trimester
decidua (Mylona
et al,
1995).
Adhesion molecules
in
embryonic development
Laminin
is the
first extracellular matrix (ECM) component
to
be expressed
by the
developing mammalian embryo (Martin
and Timpl, 1987), and has been shown to mediate cell adhesion,
migration, proliferation, outgrowth and cellular differentiation
(Edgar
et al,
1984; Aumailley et
al,
1987; Martin and Timpl,
1987;
Klein
et al,
1988; Goodman
et al,
1989; Panayotou
et
al,
1989; Vukicevic
et al,
1990).
In mouse embryonic stem
(ES)
cells,
the
major laminin
receptor
is the
integrin
ot^fij.
The c^
subunit exists
in two
forms
(C^A
and o^B),
with structurally-distinct cytoplasmic
domains derived from alternative mRNA splicing. Mouse
ES
cells express exclusively o^P, isoform
in the
undifferentiated
pluripotent state. Upon differentiation, they begin
to
express
also
the cc^
isoform (Cooper
et al,
1991). During
the
acquisition
of
attachment properties
to
ECM
by
mouse blasto-
cysts,
(X7P1
laminin receptor is up-regulated (Sutherland
et al,
1993;
Cross
et al,
1994)
at
the time that uterine stroma cells
increase their expression
of
laminin
and
collagen (Wewer
et
al,
1985).
E-cadherin, another cell adhesion molecule,
is
present
in
the mouse blastocyst
but
absent
in the
trophoblast outgrowth
(Hyafil
et al,
1981; Damjanov
et al,
1986).
The
immuno-
globulin NCAM
is
expressed
in the
mouse oocyte, down-
regulated during cytotrophoblast outgrowth in vitro and absent
by
the
day after implantation (Kimber
et al,
1994).
In the human oocyte and preimplantation embryo 05 and
P,
subunits are present (Figure 6) (Fusi etal, 1992; Turpeenniemi-
Hujanen
et al,
1992). Campbell
et al
(1995b) showed that
414
Preimplantation Embryos
Oocyte
Fertilize d
undivided
H
w
w
I
2
Cell
4
Cell
1
T
8
Cell
•
Morula
:
Blast
cc1
a2
a3
a4
a5
a6
av
aL
P1
P2
(53
P4
p5
P7
E-cadherin
P-cadherin
ICAM-1
NCAM
VCAM-1
L-selectin
a4p1
a5p1
avp3
Figure 6. Cell adhesion molecules expression on human oocytes
and embryos during the preimplantation development
P=
proliferative,
S=
secretory.
a3, o^, Pi, p3, p4 and p5 were consistently expressed throughout
the preimplantation period, whereas
0C2, (X4,
a^
P2 and P7 were
present in human oocytes
only.
These authors also demonstrated
that E-cadherin
and
three members
of the
immunoglobulin
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Cytokines-adhesion molecules-invasive proteinases
Table II. Integrin subuniis
Integrins Decidua
in human placenta] tissues
Syncytio-
trophoblastVillous
stroma cells
12 3
Villous
trophoblast
1 2 3
Intermediate
trophoblastVillous
capillary
endothelia
a,
a-.
a*
Pi
P3
P4
Desmin
++*
++*
+
*
+ +
*
+
*
+ +
*
- = absent; + = weakly positive; ++ = positive; * = basally polarized expression.
superfamily
(ICAM-1,
NCAM and VCAM-1) were present in
oocytes and early embryos but not at the blastocyst stage.
Furthermore L-selectin was present in oocytes but not in
the embryo during preimplantation development in villous
placenta, perhaps due to down-regulation following activation
of the embryonic genome. This suggests that it might function
in carbohydrate recognition during oogenesis or fertilization.
CD44, a cell surface proteoglycan, is present on the oocyte
and embryo but it is absent in postimplantation trophoblast
(Campbell etai, 1995a). The cytokine osteopontin (Eta-1) has
been found to be a protein ligand of CD44, which induces
cellular chemotaxis in vitro after binding (Weber et al, 1996).
Adhesion molecules in trophoblast invasion
Once the blastocyst has traversed the basal membrane, the
migration of first trimester invasive trophoblast in vitro requires
the expression of a5 and p, integrins. This migration is
stimulated by insulin-like growth factor-II (IGF-II) and IGFBP-
1 (through interactions with the RGD binding site of the a5
and Pi integrin) and can be inhibited by transforming growth
factor-P (TGF-P) (Irving and Lala, 1995). Bischof et al (1995)
have shown that the extravillous cytotrophoblast expressing
the o^-subunit represents the invasive population of cells
(elevated secretion of gelatinase and reduced secretion of
fibronectin) and when expression of the a5 -subunit is turned
on, invasive behaviour ceases concomitant with reduced secre-
tion of gelatinase and elevated secretion of fibronectin.
In the intermediate trophoblast there is a remarkable change
in the expression of integrins (Table II). 0^4 disappears
(Korhonen et al., 1991; Damsky et al., 1992; Campbell et al.,
1995b) perhaps because there is a reduction of 0^ and complete
loss of P4 in the distal part of the intermediate trophoblast
resulting in a down-regulation of a$4 and an up-regulation
of
OC5P1
(fibronectin receptor), a,Pi and
a3Pi
(Korhonen et al.,
1991;
Damsky et al, 1992; Burrows et al, 1993; Cross et al,
1994;
Bischof et al, 1995).
Korhonen et al. (1991) studied the distribution of
(Xi-O^,
(Xv,
Pi,
P3 and p4 integrin subunits in the first and second trimesters
and term human placenta (Table II). These authors have shown
that in the villous stromal cells only desmin and ct|Pi are
present in the first trimester placenta with decreasing expression
of this integrin in the third trimester. In the villous trophoblast,
OGP4
(receptor for laminin) is present with basally polarized
expression in the first, second and third trimester placenta, and
oc3p|
is present in the second and third trimester (Korhonen
et al, 1991). In the endothelium of villous capillary, apO^,
Ov, Pi, P3 and p4-subunits are present with the otiPi complex
being the most prominent integrin (Korhonen et al, 1991).
The relevance of adhesion molecules to trophoblast invasion
is demonstrated by several lines of research. Firstly, expression
of a6p4 and a,p| integrins by cytotrophoblasts in pre-eclampsia
is abnormal (Zhou et al, 1993). Secondly, E- and P-selectins
have been localized to vascular endothelial cells in human
decidua where they are important for adhesion between endo-
vascular trophoblast and decidual endothelial cells (Tortosa
et al, 1993). Decidual endothelial cells also express VCAM-
1,
ICAM-1 (Tortosa et al, 1993), ICAM-2 e ICAM-3 (Lasky,
1992).
There were no differences in E-selectin, VCAM-1,
ICAM-1-2-3 and PEC AM-1 in either immunostaining or
mRNA expression, in placentae from pregnancies complicated
by pre-eclampsia and intrauterine growth retardation when
compared with normal pregnancies (Lyall et al, 1995).
Trophoblast-endometrial invasion phase/pro-
teinases
The next step in the implantation process is the penetration of
the blastocyst deep into the endometrial stroma. By 8 days
after ovulation the blastocyst is embedded in the stroma and
the site of entry is covered by fibrin over which the epithelial
cells grow. For those species with invasive implantation, the
basement membrane is the first barrier that must be breached.
Trophoblast further invades the stromal compartment and then
penetrates the maternal blood vessels. Tight regulation of this
process is required to prevent pathological invasion, as occurs
in placenta accreta or in pre-eclampsia (Zhou et al, 1993).
This action is mediated by several classes of proteinase
that degrade the extracellular matrix (ECM) including serine
proteases, metalloproteinases and collagenases (Alexander and
Werb,
1991).
Serine proteases
Urokinase-type (uPA) and tissue-type (tPA) plasminogen activ-
ators are serine proteases that catalyse the conversion of
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C.Simdn et al.
plasminogen to plasmin, with a broad proteolytic activity
capable of a direct action on the degradation of
the
extracellular
matrix (Dano et al, 1985). The uPA proteolytic cascade is
involved in cell adhesion, cell migration and is the most
relevant PA in embryonic implantation. On the other hand,
tPA is involved basically in the process of fibrinolysis (Hart
and Rehemtulla, 1988). uPA activity is mediated by binding
to cell membrane high affinity receptors (Blasi et al, 1994).
Plasminogen activators are inhibited by complexing primarily
with PA inhibitors-1 (PAI-1) and -2 (PAI-2) which serve to
control their activity (Schleef et al, 1988). uPA is synthesized
as an inactive single-chain proenzyme of 50 kDa (pro-uPA)
that can be stored or secreted (Ploug et al, 1991).
It has been suggested that uPA produced by mouse tropho-
blast giant cells plays an important role in the implantation of
blastocyst into the rodent uterus (Sappino et al, 1989).
Strickland et al. (1976) reported the presence of plasminogen
activators in the trophoblast of 6-day mouse embryos (when
the trophoblast invasion of the endometrial stroma begins).
Protease inhibitors, including PAI, added to mouse blastocysts
cultured on decidual cell monolayers reduced both trophoblast
attachment and outgrowth (Kubo et al, 1981). However,
embryos lacking a functional uPA gene implanted normally
(Carmeliet et al, 1994). This circumstance does not rule out
the role of these proteases in embryonic implantation. Indeed,
mice with combined homozygous deficiency of tPA and uPA
proteases were less fertile than either wild-type mice or mice
with deficiency of a single protease. This example further
suggests that Mother Nature must provide a mechanism of
redundancy in order to guarantee the survival of the species.
Thus,
the knockout model must not be taken as the ultimate
gold standard to prove whether or not a single molecule
mediates one complex physiological action. A new approach
to this problem is the recent development of the tissue-specific
knockouts by which it is possible to inactivate one gene in
the target tissue, thus avoiding systemic gene inactivation.
Serine proteases in the human
PA activity of human endometrial tissue in vivo increases
during the proliferative phase, reaches a maximum at midcycle
and is low in the secretory phase (Casslen and Astedt, 1981,
1983).
This variation is mainly due to the regulation of u-PA
and rather than t-PA (Casslen and Astedt, 1983). Specifically,
the up-regulation of
the
inhibitor of PAI-1 induced by progester-
one results in a decreased stroma] cell PA activity (Casslen
et al, 1995; Schatz et al, 1995). Indeed, intense PAI-1
activity is localized to the decidual cells in human secretory
endometrium (Lockwood et al, 1994).
During invasion, trophoblastic cells possess invasive and
migratory properties that have been related to their plasminogen
activator activity (Strickland et al, 1976). Human cytotropho-
blast produces uPA, and its secretion is up-regulated by cAMP.
In vitro, this activity is expressed primarily during the first 24
h of culture and decreases thereafter (Queenan et al, 1987).
In addition, Hofmann et al. (1994) identified immunoreactive
uPA on the cell surface and microvilli of invasive trophoblasts.
High-affinity receptors for uPA have been reported in first-
trimester trophoblasL Only those cells whose expressed uPA
416
receptor is occupied with uPA have invasive properties
(Ossowski et al, 1991; Quax et al, 1991). The expression of
these receptors on the trophoblast may represent a possible
mechanism which facilitates the remodelling of maternal
uterine vasculature and placental development (Zini et al,
1992).
The presence of mRNA for PAI-1 and PAI-2 was demon-
strated in cultured trophoblast from term placenta (Feinberg
et al, 1987). Immunohistochemical experiments demonstrated
a moderate or intense
PAI-1
staining of the syncytiotrophoblast,
similar to results which were obtained in vitro (Hofmann et al,
1994).
Therefore, the presence of immunoreactive uPA, PAI-
1 and PAI-2 in early human implantation sites, and the finding
of the uPA receptor on trophoblast suggest that the effect and
control of uPA activity during implantation is governed at the
level of the plasma membrane of the trophoblast.
Trophoblast invasion is a self-controlled event. Three putat-
ive mechanisms which may restrain trophoblast invasiveness
have been proposed. Firstly, HCG decreases protease activity
in vitro by direct competitive inhibition of urokinase activity
in a dose-dependent manner, and thereby reduces trophoblast
invasion with no effect upon trophoblast attachment to the
basement membrane. Interestingly, even at high HCG concen-
trations trophoblast invasion is not completely inhibited, indic-
ating that other regulators are involved in this process (Yagel
et al, 1993). Secondly, in human decidua, Graham and Lala
(1991) demonstrated that human trophoblast invasiveness is
inhibited by conditioned media from decidual cell cultures
in vitro. Furthermore, the extrapolation of these results to
peri-implantation events suggests that, under progesterone
regulation, decidual cell-derived PAI-1 may restrain blastocyst
invasion into the stroma by inhibition of trophoblast-associated
uPA (Schatz and Lockwood, 1993; Casslen et al, 1995; Schatz
et al, 1995). Finally, the low density lipoprotein receptor-
related protein (LRP) is a large plasma protein of 4525 amino
acids that has also been implicated in the receptor-mediated
endocytosis of different proteins. This molecule has been
purified as a 39 kDa protein (Strickland et al, 1991) which is
synthesized as a precursor (Herz et al, 1990) and is sub-
sequently cleaved into two subunits. The studies presented by
Herz et al (1992) demonstrate that LRP is required for
the early development of the mouse embryo. LRP mediates
internalization of receptor-protease-inhibitor complexes,
allowing free protease receptors to recycle to the cell surface
where they can again bind active enzymes. Blastocysts which
were homozygous for an LRP defect failed to develop into
embryos, apparently because of a failure to invade the uterus
for implantation. To determine whether this homozygous LRP
defect interferes with embryogenesis, embryos obtained from
heterozygous matings were analysed and found to include
those which were homozygous LRP-deficient. They demon-
strated that LRP is not essential during preimplantation devel-
opment but is important for implantation.
Metalloproteinases
The matrix metalloproteinases (MMPs) are a family of zinc-
dependent endopeptidases possessing proteolytic activities
against several components of the extracellular matrix
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Cytokines-adhesion molecules-invasive proteinases
(Matrisian, 1990). These endopeptidases are secreted as inact-
ive pro-enzymes (zymogens) which become activated on
removal of the amino-terminal propeptide (Van Wart and
Birkedal-Hansen, 1990). Activated enzymes are able to digest
the extracellular matrices. According to their substrate specifi-
city, the family is composed of three groups: collagenases,
gelatinases and stromelysins. Collagenases include MMP-1
and MMP-8 and can digest collagen types I, n, m, VII and
X. Gelatinases digest collagen type IV and denatured collagen.
Stromelysins degrade fibronectin, laminin, collagens IV, V and
VTI as well as proteoglycans.
Several metalloproteinase inhibitors, named as tissue inhib-
itor of metalloproteinases (TTMP)-l, TTMP-2 and TTMP-3,
control the activity of the metalloproteinases. TIMP-1 is a
glycoprotein with a molecular mass of 28.5 kDa which
is decreased to a 20 kDa molecule after deglycosylation
(Carmichael et ai, 1986). The secreted protein consists of 184
amino acids with six disulphide bonds and two glycosylation
sites bearing TV-linked oligosaccharides (Stricklin and Welgus,
1983;
Shimonovitz et ai, 1994). TTMP-2 is a non-glycosylated
protein of 21 kDa (Stetler-Stevenson et ai, 1989). TIMP-1
and TTMP-2 form stable and non-covalent complexes with
target metalloproteinases. Both have been cloned (Docherty
et ai, 1985; Carmichael et al., 1986; Boone et al., 1990;
Stetler-Stevenson et al., 1990). Their homology is only 41%
(Stetler-Stevenson et ai, 1989) but the cysteine residues that
form six disulphide bonds are completely conserved. However,
their immunological cross-reactivity appears minimal: anti-
TTMP-1 does not precipitate TTMP-2 (Herron et ai, 1986).
TTMP-1 interacts preferentially with the 92-kDa type IV
procollagenase and TTMP-2 with the 72-kDa type IV procolla-
genase (Goldberg et ai, 1989; Howard et ai, 1991a,b). Ward
et al. (1991) showed that TTMP-1 is more active against 72-
kDa type IV collagenase and TIMP-2 against 92-kDa type IV
collagenase. Both TTMP-1 and -2 inhibit the conversions of
95 kDa and 72 kDa type IV procollagenases and pro-stromely-
sin into lower molecular-mass forms and have biochemically
similar inhibitory action. Several studies suggest that TTMP-1
is a physiological inhibitor of metalloproteinases. The addition
of anti-TTMP-1 immunoglobulin G to cultured chondrocytes
results in the degradation of collagen because of the disruption
of TTMP-1-mediated collagenase inhibition (Thomson et ai,
1987).
The addition of TIMP-1 to cultured B16 melanoma
cells interferes with invasion of basement membranes by
these cells (Mignatti et ai, 1986; 1989). Reduced TTMP-1
concentrations in cells transfected with antisense TTMP-1
mRNA result in increased invasiveness (Khokha et ai, 1989).
This suggests that the regulation of TTMP-1 expression and
activity may play an important role in the regulation of
proteolysis.
The significance of type IV collagenase in the implantation
process and trophoblast invasion is crucial. The implanting
blastocyst penetrates the epithelium to reach the basement
membrane. Type IV collagen is the major protein component
of the basal membrane. In vitro, the secretion of type IV
collagenase is related to the process of implantation, suggesting
that its invasive properties are responsible for the ability of the
embryo to traverse the uterine basal membrane (Turpeenniemi-
Hujanen et ai, 1992). Type IV collagen is also one of the
main structures of the uterine extracellular matrix at the
fetomaternal interface (Emonard et ai, 1990; Alexander and
Werb,
1991). In vitro, results obtained by Shimonovitz et al.
(1994) revealed that first-trimester trophoblast cells are mark-
edly more invasive than those from third-trimester trophoblast.
These researchers observed a significant, time-dependent accu-
mulation of 72 and 92 kDa type IV collagenase in the
conditioned medium from first-trimester trophoblast. In the
third-trimester trophoblast the accumulation of 92 kDa type
IV collagenase was time-dependent, although only insignificant
amounts of 72 kDa were detected in the media. These results
support the observation made in vivo that invasiveness is more
pronounced in trophoblast cells of early pregnancy.
Cytokines-adhesion molecules-invasive pro-
teinases hypothesis
The dialogue between implanting blastocyst and uterus is
crucial to the implantation process. Our problem is to unravel
this apparently complicated language in order to understand
the physiology and pathology of the implantation process
which is the 'sine qua non' to maintain the survival of the
species. However, Mother Nature teaches us that potentially
simple mechanisms with built-in redundancy are more effective
than complicated schemata for important physiological pro-
cesses. Data indicated in the present review suggest that
steroid hormones act systemically in the preparation of the
endometrium for implantation thus establishing 'the implanta-
tion window'. These actions are not only endocrine through
specific steroid receptors but also modulate paracrine/autocrine
effectors such as cytokines, adhesion molecules and invasive
proteinases.
Expression of cytokines is honmonally-regulated. The uterine
synthesis of CSF-1 appears to be regulated by the synergistic
action of 17-p* oestradiol and progesterone (Pollard et ai,
1987).
LIF expression in the reproductive cycle coincides with
elevated levels of oestrogen, or can be induced by a single
injection of oestrogen suggesting that uterine LIF expression
may be under oestrogen control. In mice, endometrial IL-1 is
hormonally regulated regardless of the presence of embryos
(Choudhuri and Wood 1993; De et ai, 1993). In humans,
progesterone, EGF and FL-ip up-regulate the expression of
IL-1R tl mRNA in endometrial stromal cells (ESC) (Sim6n
et ai, 1994a, 1994c).
Not only are cytokines hormonally driven, but they also
regulate each other in a cascade process, which provides
'redundancy' to the system. IL-1 has regulatory effects on
CSF-1 and LIF in several systems. IL-ip stimulates both CSF-
1 mRNA expression and CSF-1 protein secretion in villous
core mesenchymal fibroblasts (Harty and Kauma, 1992), and
in bone marrow stromal cells (Yang et ai, 1988). On the other
hand,
IL-1
a up-regulation of LIF has also been reported in
several mesenchymal cell populations (Lubbert et ai, 1991)
including bone marrow cells (Wetzler et ai, 1991) and synovial
fibroblast-like cells (Hamilton et ai, 1993). Indeed, IL-1
induces mRNA coding for LIF in cultured ganglia, and LIF
induced by
IL-1
may ultimately be responsible for the induction
417
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C.Simbn et al.
ADHESIONINVASION
HORMONESHORMONES
Figure 7. Schematic diagram of the cytokines-adhesion molecules-invasive proteinases hypothesis. Adhesion: cytokines controlled at the
endocrine (hormonal) and paracrine/autocrine (cytokines and growth factors) levels may start the mutual recognition of implanting blastocyst
and endometrium and may also serve as the link in the regulation of adhesion molecules that provide the physical contact between embryo
and uterus. Invasion: invasive proteinases have a close connection with adhesion molecules and they are regulated by hormones, growth
factors and cytokines.
by IL-1 of substance P in these culture conditions (Shadiak
et al, 1993). In human endometrial stromal cells, EL-ip is a
potent inducer of LIF expression (Arid et al., 1995).
Studies on cadherins (van der Linden et al, 1995) in
human endometrium suggest a minor role for oestradiol and
progesterone in the regulation of these cell adhesion molecules.
Interestingly steroid hormones, specifically progesterone,
appear to regulate integrin expression (Castelbaum et al., 1995)
in human endometrium. Autocrine/paracrine factors including
cytokines and growth factors are increasingly implicated in
modulation and regulation of cell adhesion molecules. In MG-
63 human osteosarcoma cells, EL-ip modulates the Pi integrin
subunit and its associated a-subunits (Dedhar, 1989). EL-lp
increases mRNA activity of a2, (Xj and 0^, while down-
regulating (X4 activity (Miliam et al, 1991). In the same
cell line, IL-ip and TNF-a control the expression of a,Pi
heterodimer (Santala and Heino, 1991). In human endothelial
cells,
IL-ip modulates o^pi expression (Defilippi et al, 1992).
IL-ip,
TNF-a and interferon-y (EFN-y) induce the expression
of
ICAM-1,
E-selectins and VCAM-1 at the level of both
mRNA and protein in endothelial cells (Pober et al, 1986;
Bevilacqua et al, 1989; Osborn et al., 1989; Tabibzadeh et al,
1994).
The role of IL-ip modulation of adhesion molecules is
also evident in the stimulation of adhesion to the human
pulmonary artery smooth muscle cells (Wang et al., 1995). In
response to basic fibroblast growth factor (bFGF) human
endothelial cells increase their expression of a2Pi,
(X3P1,
(X5P1,
OePi, 0^4 and avP5 and down-regulate <X|Pi and otvP3
(Tabibzadeh etal, 1995). Transforming growth factor-P (TGF-
P) also alters specific integrin expression in many cell types
(Ignotz and Massague, 1987; Heino and Massague, 1989b,
Heino et al, 1989; Ignotz et al, 1989; Sheppard et al, 1992;
Yokosaki et al., 1994).
PAI-1,
which is the major physiological
inhibitor of uPA, binds to vitronectin as an integrated part of
the ECM (Andreasen et aL, 1990).
Proteinases are also regulated by the action of hormones,
cytokines and growth factors. Progesterone and oestradiol-
17p regulate collagenolysis in uterine cervical fibroblast by
increasing the production of
TEMP
and decreasing the produc-
tion of tissue collagenase and stromelysin (Sato et al., 1991).
The action of progesterone on TTMP production was also
shown to be more effective than that of 17P oestradiol. The
increased production of TTMP is associated with an increase
in the steady-state concentration of TIMP mRNA; however,
the increase in TTMP mRNA is less than the increase in TEMP
protein, suggesting that steroids are able to affect the translation
and/or the stability of TIMP mRNA (Sato et al, 1991).
PAI-1,
which is the major physiological inhibitor of uPA,
is regulated by cytokines and growth factors. EL-1 increases
PAI-1 expression in both endothelial (Emmeis et al, 1986)
and hepatocyte cells (de Boer et al, 1991). TNF increases the
production of PAI in human endothelial cells in vitro (van
Hinsberghero/., 1988), and the expression of PAI-1 is regulated
by epidermal growth factor (EGF) in hepatocyte cells (Lucore
et al, 1988). Hepatocyte growth factor (HGF) stimulates dose-
and time-dependent expression of PAI-1 in human hepatocyte
cells;
however, this effect does not occur in endothelial cells
(Wojta et al, 1994).
Metalloproteinases and their inhibitors are regulated by
growth factors and cytokines such as epidermal growth factor
(EGF),
basic fibroblast growth factor (bFGF), transforming
growth factor-pi (TGF-Pl), interleukin-1 (TL-1) and tumour
necrosis factor-a (TNF-a). These act to determine the balance
between proMMP-1 and TTMP-1 (Murphy et al, 1985;
Edwards et al, 1987; Ito et al., 1990; MacNaul et al, 1990;
Overall et al, 1991). In primary cultures of rat hepatocytes,
the expression of secreted TTMP-1 protein can be up-regulated
by EL-ip, EL-6 and EL-11 and is inhibited by the synthetic
glucocorticoid dexamethasone (Roeb et al, 1994).
TGFP-1 is the main candidate responsible for cytokine
418
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Cytokines-adhesion molecules-invasive proteinases
control of trophoblast invasiveness. TGF|3-1 is expressed in
human decidua (Graham et al., 1992) and is capable of
stimulating TIMP-1 expression in fibroblasts, and it has been
shown to inhibit the expression of stromelysin (Matrisian,
1990).
However, transgenic animals carrying the defective
TGFfJ-1 gene are bale to implant normally and develop to
term (Shull et al., 1992).
The first stage of this hypothesis (Figure 7) is that cytokines
(CSF-1,
LIF and IL-1) and their specific receptors, being
properly distributed throughout endometrium and embryo and
adequately controlled at the endocrine (hormonal) and para-
crine/autocrine (cytokines and growth factors) levels, initiate
the mutual recognition of implanting blastocyst and endomet-
rium. Cytokines and growth factors may also serve as the
link in the regulation of molecules (referred to as adhesion
molecules) that provide the physical contact between embryo
and uterus. The mechanism by which IL-1 may be involved
in embryonic attachment remains to be elucidated. However,
the potent ability of
IL-1
to induce the adherence of neutrophils
to endothelial cells has already been demonstrated (Schleimer
and Rutledge, 1986). Indeed, the inhibition of human endo-
thelial cell adhesiveness for human neutrophils and eosinophils
is an established bioassay for rh IL-lra activity (Carter et al,
1990).
Finally, invasive proteinases are closely inter-related
with adhesion molecules and are regulated by hormones,
growth factors and cytokines. This provides a connection
which, although possibly merely circumstancial, may lead us
to a better understanding of the implantation process.
References
Albelda, S.M. (1993) Role of intcgnns and other cell adhesion molecules in
tumor progression and metastasis. Lab. Invest., 68, 4-17.
Alexander, CM. and Werb, Z. (1991) Extracellular matrix degradation. In
Hay, E.D. (ed.). Cell Biologv of Extracellular Matrix. Plenum Press, New
York, pp. 255-302.
Andreasen, P., Georg, B., Lund, L. el al. (1990) Plasminogen activator
inhibitors: hormonally regulated serpins. Mol. Cell. Endocrinol., 68, 1-19.
Arceci, RJ., Shanahan, R, Stanley, E.R. et al. (1989) The temporal expression
and location of colony stimulating factor-1 (CSF-I) and the receptor in the
female reproductive tract are consistent with CSF-I regulated placental
development. Proc. Nad.
Acad.
Sci. USA.. 86, 8818-8822.
Arceci, R.J., Pampfer, S. and Pollard, J.W. (1992) Expression of CSF-l/c-fms
and SF/c-kit mRNA during preimplantation mouse development
Dev.
Bioi,
151,
1-8.
Arid, A., Engin, O., Attar, E. et al. (1995) Modulation of leukemia inhibitory
factor gene expression and protein biosynthesis in human endometrium.
J. Clin. Endocrin. Metab., 80, 1908-1915.
Aumailley, M., Nurcombe, V., Edgar, D. et al. (1987) The cellular interactions
of laminin fragments. J. Biol. Chem., 262, 11532-11538.
Austgulen, R., Amtzen, KJ., Vatten, LJ. et al. (1995) Detection of cytokines
(interleukin-l, interleukin-6, transforming growth factor-P) and soluble
tumor necrosis factor receptors in embryo culture fluids during in-vitro
fertilization. Hum.
Reprod.,
10, 171-176.
Baraflao, R.I., Piazza. A., Rumi, L. etal. (1992) Predictive value of interleukin-
Ib in supernatant^ of human embryo culture. (Abstr.) Fenil. Sterii, 58
(Suppl.), 0-007.
Bartocci, A., Pollard, J.W. and Stanley. E.R. (1986) Regulation of colony-
stimulating factor I during pregnancy. J. Exp. Med., 164,
956-961.
Bates,
R.C., Rankin, LM., Lucas, CM. et al. (1991) Individual embryonic
fibroblasts express multiple p chains in association with the c^ integrin
subuniL Loss of p3 expression with cell confluence. J.Biol.Chem., 266,
18593-18599.
Berg, E.. Robinson. M.. Mansson. E. et al. (1991) A caibohydrate domain
common to both sialyl le a and sialyl le x is recognized by the endothelial cell
leukocyte adhesion molecule
ELAM-1.
J. Biol Chem.. 266, 14869-14879.
Berlin. C. Bargatze, R.F., Campbell. JJ. et al. (1995) 04 integrins mediate
lymphocyte attachment and rolling under physiologic flow. Cell, 80,
413-422.
Bevilaqua. M.P., Stengelin. S.. Gimbrone, M.A. et al.. (1989) Endothelial
leukocyte adhesion molecule I: an inducible receptor for neutrophils related
to complement regulatory proteins and lectins. Science, 243, 1160-1164.
Bhatt. H.. Brunei, LJ. and Stewart, C.L. (1991) Uterine expression of leukemia
inhibitory factor coincides with the onset of blastocyst implantation. Proc.
Natl.
Acad.
Sci. USA., 88, 11408-11412.
Bischof,
P.. Haenggeli, L. and Campana, A. (1995) Gelatinase and oncofetal
fibronectin secretion arc dependent upon integrin expression in human
cytotrophoblast. Mol. Hum.
Reprod.,
1, see Hum.
Reprod.,
10, 734-742.
Blankenship. T.N., Enders, A.C. and King, B.F. (1993) Trophoblastic invasion
and development of uteroplacental arteries in the macaque.
Immunohistochemical localization of cytokeratins, desmin, type IV
collagen, laminin and fibronectin. Cell Tissue Res., 212, Ill-lit.
Blasi, F., Conese, M., Moller, L.B. et al. (1994) The urokinase receptor
structure, regulation and inhibitor-mediated intemalization. Fibrinolvsis, 8,
182-188.
Bodary, S.C and McLean, J.W. (1990) The integrin (5, subunit associates
with the vitronectin receptor
Oy
subunit to form a novel vitronectin receptor
in a human embryonic kidney cell line. J. Biol. Chem., 265, 5938-5941.
Boone, T.C, Johnson, MJ., de Clerck, Y.A. et al. (1990) cDNA cloning and
expression of a metalloproteinase inhibitor related to tissue inhibitor of
metalloproteinases. Proc. Natl.
Acad.
Sci. USA, 87, 2800-2804.
Bossy, B., Bossy-Wetzel, E. and Reichardt, L.F. (1991) Characterization of
the integnn cc8 subunit: a new integrin prassociated subunit, which is
prominently expressed on axons and on cells in contact with basal laminae
in chick embryos. EMBO J., 10, 2375-2385.
Burrows, T.D., King, A. and Loke Y.W. (1993) Expression of integrins by
human trophoblast and differential adhesion to laminin or fibronectin. Hum.
Reprod.,
8, 475-84.
Burrows, T.D., King, A., Smith, S.K et
al.
(1995) Human trophoblast adhesion
to matrix proteins: inhibition and signal transduction. Hum.
Reprod,
10,
2489-2500.
Campbell, S., Swann, H.R., Aplin, J.D. et al. (1995a) CD44 is expressed
throughout preimplantation human embryo development. Hum.
Reprod.,
10,
425-430.
Campbell, S., Swann, H.R.,
Seif,
M.W. et al. (1995b) Cell adhesion molecules
on the oocyte and preimplantation human embryo. Mol. Hum.
Reprod.,
1,
see Hum.
Reprod.,
10, 1571-1578.
Cannistra, S.A., Kansas, G.S.,
Niloff,
J. et al. (1993) Binding of ovarian
cancer cells to peritoneal mesothelium in vitro is partly mediated by
CD44H. Cancer Res., 53, 3830-3838.
Carmeliet, P., Schoonjans, L., Kieckens, L. et al. (1994) Physiological
consequences of loss of plasminogen activator gene function in mice.
Nature, 368, 419-424.
Carmichael, D.F., Sommer, A., Thompson, R.C. etal. (1986) Primary structure
and cDNA cloning of human fibroblast collagenase inhibitor Proc. Natl.
Acad.
Sci. USA, 83, 2407-2411.
Carter, D.B., Deibel, M.R., Dunn, CJ. et. al. (1990) Purification, cloning,
expression and biological characterization of an interleukin-l receptor
antagonist. Nature, 344, 633-638.
Casslen, B. and Astedt, B. (1981) Fibrinolytic activity of human uterine fluid.
Ada Obstet. Gynecol.
Scand.,
60, 55-58.
Casslin, B. and Astedt, B. (1983) Occurrence of both urokinase and tissue
plasminogen activator in the human endometrium. Contraception, 28,
553-564.
Cassten, B., Nordengren, J., Gustavsson, B. et al. (1995) Progesterone
stimulates degradation of urokinase plasminogen activator (u-PA) in
endometrial stromal cells by increasing its inhibitor and surface expression
of the u-PA receptor. J. Clin. Endocrinol. Metab., 80, 2776-2784.
Castelbaum, AJ., Sawin, S.W., Bellardo, LJ. et al. (1995) Endometrial
integrin expression in women exposed to diethylstilbestrol in uiero. Fenil.
Sterii, 63, 1217-1221.
Chard, T. (1995) Cytokines in implantation. Hum.
Reprod.
Update, 1,385-3%.
Chamock-Jones, D., Sharkey, A., Fenwick, P. el at. (1994) Leukaemia
inhibitory factor mRNA concentration peaks in human endometrium at the
time of implantation and the blastocyst contains mRNA for the receptor at
this time. J.
Reprod.
Fenil., 101, 421-426.419
by guest on July 24, 2011molehr.oxfordjournals.orgDownloaded from

C.Simbn et al.
Cheresh, D.A. (1987) Human endothelia] cells synthesize and express an Arg-
Gly-Asp directed adhesion receptor involved in attachment to fibrinogen
and von Willebrand factor. Proc. Nail.
Acad.
Sci. USA, 84, 6471-6475.
Cheung, A.N.Y., Srivastava, G., Pittaluga, S. et al. (1992) Expression of c-
myc and c-fms oncogcnes in trophoblastic cells in hydatidiform mole and
normal human placenta. J. Clin. Palhoi, 3, 204—207.
Choudhuri, R. and Wood, G.W. (1993) Production of
interleukin-1,
interleukin-
6 and tumor necrosis factor alpha in the uterus of pseudopregnant mice.
Biol.
Reprod.,
49, 596-603.
Cominelli, F, Nast, C.C., Clark, B.D. et al. (1990) Interleukin-1 (IL-1) gene
expression, synthesis, and effect of specific IL-1 receptor blockade in rabbit
immune complex colitis. J. Clin. Invest., 86,
972-981.
Conquet, F and Brulet,
P.
(1990) Development expression of myeloid leukemia
inhibitory factor gene in preimplantalion blastocyst and in extraembryonic
tissue of mouse embryos. Mol. Cell. Biol., 10, 3801-3805.
Cooper, H.M., Tamura, R.N. and Quaranta, V. (1991) The major laminin
receptor of mouse embryonic stem cells is a novel isoform of the o^pi
integnn. J. Cell. Biol., 115, 843-50.
Cross,
J.C., Werb, Z. and Fisher, SJ. (1994) Implantation and the placenta:
key pieces of the development puzzle. Science, 266, 1508-1517.
Daiter, E., Pampfer, S., Yeung, Y.G. et al. (1992) Expression of colony
stimulating factor-1 (CSF-1) in the human uterus and placenta. J. Clin.
Endocrinol. Metab., 74, 850-858.
Damjanov, I., Damjanov, A. and Damsky, C.H. (1986) Developmentally
regulated expression of the cell-cell adhesion glycoprotein cell-cam 120/
80 in pen-implantation mouse embryos and extraembryonic membranes.
Dev. Biol, 116, 194-202.
Damsky C.H., Fitzgerald M.L. and Fisher SJ. (1992) Distribution patterns of
extracellular matrix components and adhesion receptors are intricately
modulated during first trimester cytotrophoblast differentiation along the
invasive pathway, in vivo. J. Clin. Invest., 89, 210-222.
Dano,
K., Andrcasen, P.A., Grondahl-Hansen, J. et al. (1985) Plasminogen
activators, tissue degradation and cancer. Adv. Cancer Res., 44, 139-266.
De M., Sanford, T.R. and Wood, G.W. (1993) Expression of interleukin I,
interleukin 6 and tumor necrosis factor a in mouse uterus during the pen-
implantation period of pregnancy. J.
Reprod.
Fertil., 97, 83-89.
de Boer, J.P., Abbink, JJ., Brouwer, M.C. et al. (1991) PAI-I synthesis in the
human hepatoma cell line HepG2 is increased by cytokines- evidence that
the liver contributes to acute phase behaviour of
PAI-1.
Thromb. Haemost.,
65,
1881.
De los Santos, M.J., Mercader, A., Frances, A. et al. (1996) Immunoreactive
human embryonic interleukin-1 system and endometrial factors regulating
their secretion during embryonic development. Biol.
Reprod.,
54, 563-574.
Dedhar, S. (1989) Regulation of expression of the cell adhesion receptors,
integrins, by recombinant human interleukin-1P in human osteosarcoma
cells:
inhibition of cell proliferation and stimulation of alkaline phosphatase
activity. / Cell. Physioi, 138, 291-299.
Defilippi, P., Silengo, L. and Tarone, G. (1992) o^Pi Integrin (aminin receptor)
is down-regulated by tumor necrosis factor a and interleukin-1P in human
endothelial cells. /. Biol. Chem., 261, 18303-18307.
Dejana, E, Martin-Padura, I., Laauri, D. et al. (1992) Endothelial leukocyte
adhesion molecule-1 dependent adhesion of colon carcinoma cells to
vascular endothelium is inhibited by an antibody to Lewis fucosylated type
I carbohydrate chain. Lab. Invest., 66, 324-330.
Dinarello, C.A. (1988) Biology of interleukin 1. FASEB J., 1, 108-115.
Docherty, AJ.R, Lyons, A., Smith, BJ. et al. (1985) Sequence of human
tissue inhibitor of metalloproteinases and its identity to erythroid-
potentiating activity. Nature, 318, 66-69.
Dower, S.K., Kronheim, S.R., Hopp, T.P. et. al. (1986) The cell surface
receptors for interleukin-1 a and interleukin-1 P are identical. Nature, 324,
266-8.
Edgar, D., Timpl. R. and Thoenen, H. (1984) The heparin binding domain of
laminin is responsible for its effects on neurite outgrowth and neuronal
survival. EMBO J., 3, 1463-1468.
Edwards, D.R., Murphy, G.. Reynolds. JJ. et al. (1987) Transforming growth
factor P modulates the expression of collagenase and metalloproteinase
inhibitor. EMBO J., 6, 1899-1904.
Edwards, R.G. (1994) Implantation, interception and contraception. In
Edwards, R.G. (ed.). New Concepts in Fertility Control. Oxford University
Press,
Oxford, p. 73.
Edwards, R.G. (1995) Physiological and molecular aspects of human
implantation. In Simon. C. and Pellicer, A. (eds), Implantation Markers.
Oxford University Press, Oxford, p. I.
Elices, MJ. and Hemler, M.E. (1989)The human integrin VLA-2 isacollagen
receptor on some cells and a collagen/laminin receptor on others. Proc.
Natl.
Acad.
Sci. USA, 86, 9906-9910.
Emmeis, JJ. and Kooistra, T. (1986) IL-1 and lipopolysaccharide induce an
inhibitor of tissue-type plasminogen activator in vivo and in cultured
endothelial cells. J. Exp. Med., 163, 11260.
Emonard, H., Christiane, Y., Smet, M., et al. (1990) Type IV and interstitial
collagenolytic activities in normal and malignant cells are specifically
regulated by the extracellular matrix. Inv. Melast., 10, 170-177.
Enders, A. (1981) Embryo implantation, with emphasis on the rhesus monkey
and the human. Reproduction, 5, 163-167.
Feinberg, R.F., Kao, L.C., Haimowitz, J.E. et al. (1987) Plasminogen activator
inhibitors types 1 and 2 in human trophoblast. Lab. Invest., 61, 20-26.
Flynn, A. (1984) Stimulation of interleukin-1 production from placenta!
monocytes. Lym. Res., 3, 1-5.
Flynn, A., Fmke, J.H. and Hilfiker, M.L. (1982) Placenta! mononuclear
phagocytes as a source of interleukin-1. Science, 218, 475—477.
Foxall, C, Watson, S.R., Dowbenko, A. et al. (1992) The three members of
the selectin receptor family recognize a common carbohydrate epitope, the
sialyl Lewis x oligosaccharide. J. Cell Biol., 117, 895.
Fusi, F.M., Vignalli, M., Busaca, M. et al. (1992) Evidence for the presence
of an integrin on the oolemma of unfertilised human oocytes. Mol.
Reprod.
Dev., 31, 215-222.
Garria-Lloret, M.I., Mornsh, D.W., Wegmann, T.G. et
al.
(1994) Demonstration
of functional cytokine-placental interactions: CSF-1 and GM-CSF stimulate
human cytotrophoblast differentiation and peptide hormone secretion. Exp.
Cell. Res., 214, 46-54.
Goldberg, G.I., Manner, B.L., Grant, G.A. et al. (1989) Human 72-kilodalton
type IV collagenase forms a complex with a tissue inhibitor of
metalloproteases designated TIMP-2. Proc. Natl.
Acad.
Sci. USA, 86,
8207-8211.
Goodman, S.L., Rise, G. and von der Mark, K. (1989) The E8 subfragment
of laminin promotes locomotion of myoblast over extracellular matrix. J.
Cell. Biol., 109, 799-809.
Graham, C.H. and Lala, P.K. (1991) Mechanism of control of trophoblast
invasion in situ. J. Cell. Physioi., 148, 228-234.
Graham, C. H., Lysiak, JJ., McCrae, K.R. et al. (1992) Location of
transforming growth factor-P at the human fetal-maternal interface: role in
trophoblast growth and differentiation. Biol
Reprod.,
46, 561-572.
Granowitz, E.V., Porat, R., Mier, J.W., et al. (1992) Pharmacokinetics, safety
and immunomodulatory effects of human recombinant interleukin-1 receptor
antagonist in healthy humans. Cytokine, 4, 353-360.
Hamilton, J.A., Waring, P.M. and Filonzi, E.L. (1993) Induction of leukemia
inhibitory factor in human synovial fibroblasts by IL-1 and TNF-cc.
J. Immunol., 150, 1496-1502.
Hannum, C.H., Wilcox, CJ., Arend, W.P. et. al. (1990) Interleukin-1 receptor
antagonist activity of a human interleukin-1 inhibitor. Nature, 343, 336—40.
Hardy, R.I., Anderson, DJ. and Hill, J.A. (1993) Lack of correlation between
interleukin-1-alpha in preimplantation culture media and pregnancy
outcome. (Abstr.) Fertil. Steril., 61 (Suppl.), 0-139.
Hart, D.A. and Rehemtulla. A. (1988) Plasminogen activators and their
inhibitors: regulators of extracellular proteolysis and cell function. Comp.
Biochcm. Physioi, 90B, 691-708.
Harty, J.R. and Kauma,S.W. (1992) Interleukin-P stimulates colony stimulating
factor-1 production in placental villous core mesenchymal cells. J. Clin.
Endocrinol. Metab.. 75, 947-950.
Hatayama, H., Kanazaki, H., Iwai, M. et al. (1994) Progesterone enhances
macrophage colony-stimulating factor production in human endometrial
stromal cells in vitro. Endocrinology, 135, 1921-1927.
Hawes, S., Thomas, M., Paton, A. et al. (1993) The detection of mRNA for
the receptor of colony stimulating factor (c-fms) in human oocytes and
preimplantation embryos. J.
Reprod.
Fertil., 12 (Abstract series), 7.
Heino, J., Ignotz, R.A.. Hemler. M.E. et
al.
(1989) Regulation of cell adhesion
receptors by transforming growth factor-p. Concomitant regulation of
integrins that share a common pi subunit. J. Biol. Chem., 264, 380-388.
Heino, J. and Massague, J. (1989) Transforming growth factor-P switches the
pattern of integrins expressed in MG-63 human osteosarcoma cells and
causes a selective loss of cell adhesion to laminin. J. Biol. Chem., 264,
21806-21811.
Hemler. M.E. (1990) VLA proteins in the integrin family: structures, functions
and their role on leukocytes. Ann. Rev. Immunol, 8, 365-400.
Herron, G.S., Banda, MJ., Clark, EJ. et al. (1986) Secretion of
metalloproteinases by stimulated capillary endothelial cells II. Expression
of collagenase and stromelysin activities is regulated by endogenous
inhibitors. Biol Chem., 261, 2814-2818.
420
by guest on July 24, 2011molehr.oxfordjournals.orgDownloaded from

Cytokines-adhesion molecules-invasive proteinases
Herz. J.. Kowal, R.C., Goldstein, J.L. et al. (1990) Proteolytic processing of
the 600 kDa low density lipoprotein receptor related protein (LRP) occurs
in a trans-Golgi compartment. EMBO J., 9, 1769-1776.
Herz, J., Clouthier. D.E. and Hammer, R.E. (1992) LDL receptor-related
protein internalizes and degrades uPA-PAI-1 complexes and is essential for
embryo implantation. Cell, 71,
411-421.
Hilton, DJ., Nicola, D.A. and
Metcalf,
D. (1988) Purification of a munrte
leukemia inhibitory factor from Krebs ascites cells. Anal. Biochem., 173,
359-367.
Hofmann, G.E., Glatstein, I., Schatz et al. (1994) Immunohistochemical
localization of urokinase-type plasminogen activator inhibitors 1 and 2 in
early human implantation sites. Am. J. Obstet. Gvnecol, 170, 671-676.
Horuk, R. and McCubrey, J.A (1989) The IL-1 receptor in Raji human B-
lymphoma cells. Molecular characterization and evidence for receptor-
mediated activation of gene expression. Biochem. J., 260, 657-63.
Howard, E.W., Bullen, E.C. and Banda, MJ. (1991a) Preferential inhibition
of 72 and 92 KDa gelatinases by tissue inhibitor of metalloproteinases-2.
J. Biol. Chem., 266, 13070-13075.
Howard, E.W., Bullen, E.C. and Banda, MJ. (1991b) Regulation of the
autoactivation of human 72-kDa progelatinase by tissue inhibitor of
metalloproteinases. J. Biol. Chem., 266, 13064-13069.
Hu, X.L., Yang,
Y.
and Hunt, J.S. (1992) Differential distribution of interleukin-
la and interleukin-ip proteins in human placentas. J.
Reprod.
Immunol.,
22,
257-268.
Hyafil, F, Babinet, C. and Jacob, F. (1981) Cell-cell interactions in early
embryogenesis: a molecular approach to the role of calcium. Cell, 26,
447^(54.
Hynes, R O. (1987) Integrins: a family of cell surface receptors. Cell, 48,
549-554.
Hynes, R.O. (1992) Integrins: versatility, modulation, and signaling in cell
adhesion. Cell, 69, 11-25.
Ignatius, MJ., Large, T.H., Houde, M. el al. (1990) Molecular cloning of the
rat integrin cti-subunit: a receptor for laminin and collagen. J. Cell. Biol.,
Ill,
709-720.
Inoue, T., Kanzaki, H., Iwai, M. el al. (1994) Tumor necrosis factor a inhibits
in-vitro decidualization of human endometrial stromal cells. Hum.
Reprod.,
9,2411-2417.
Ignotz, R.A. and Massague, J. (1987) Cell adhesion protein receptors as
targets for transforming growth factor-P action. Cell, 51, 189—197.
Ignotz, R.A., Heino, J. and Massague, J. (1989) Regulation of cell adhesion
receptors by transforming growth factor-p. Regulation of vitronectin
receptor and
LFA-1.
J. Biol. Chem., 264, 389-392.
Irving, J.A. and Lala, P.V. (1995) Functional role of cell surface integrins on
human trophoblast cell migration: regulation by TGF-p, IGF-II and IGFBP-
1.
Exp. Cell Res., 217, 419^27.
Ito,
A., Sato, T., Iga, T. el al. (1990) Tumor necrosis factor bifunctionally
regulates matrix metalloproteinases and tissue inhibitor of
metalloproteinases production by human fibroblasts. FEBS
Lett.,
269,93-95.
Jacobs, A.L. and Carson, D.D. (1993) Uterine epithelial cell secretion of
interleukin-la induces prostaglandin E2 (PGEj) and PGF2, secretion by
uterine stromal cells in vitro. Endocrinology, 132, 300-308.
Jikihara, H., Poisner, A.M. and Handwerger, S. (1995) Tumor necrosis factor-
cc and interleukin-ip inhibit the synthesis and release of rcnin from human
decidual cells. J. Clin. Endocrinol. Metab., 79, 195-199.
Johannisson, E. (1991) Morphological and histochemical factors related to
implantation. Bailliere's Clin. Obstet. Gynecol., 5, 191-209.
Jokhi, P.P., Chumbley, G., King, A. et al. (1993) Expression of the colony
stimulating factor-1 receptor (c-fms product) by cells at the human
uteroplacental interface. Lab. Invest., 68, 308-320.
Juliano, R.L. and Haskill, S. (1993) Signal transduction from the extracellular
matrix. J. Cell. Biol., 120, 577-585.
Kanzaki, H., Yui, J., Iwai, M. et al. (1992) The expression and localization
of mRNA for colony-stimulating factor (CSF-1) in human term placenta.
Hum.
Reprod.,
7, 563-567.
Kariya, M., Kanzaki, H., Hanamura, T. et al. (1994) Progesterone-dependent
secretion of macrophage colony-stimulating factor by human endometrial
stromal cells of nonpregnant uterus in culture. J. Clin. Endocrinol. Metab.,
79,
86-90.
Kariya, M., Kanzaki, H., Takakura, K. et al. (1991) Interleukin-1 inhibits
in vitro decidualization of human endometrial stromaJ cells. J. Clin.
Endocrinol. Metab., 73, 1170-1174.
Kauma, S., Matt, D., Strom. S. et al (1990) Interleukin-ip (IL-IP), human
leukocyte antigen HLA-DR a, and transforming growth factor-p (TGF-p)
expression in endometrium, placenta and placenta] membranes. Am. J.
Obstet. Gynecol, 163, 1430-1437.
Kauma, S.W., Aukerman, S.L.. Eierman. D. el al. (1991) Colony-stimulating
factor-1 and c-fms expression in human endometrial tissues and placenta
during the menstrual cycle and early pregnancy. J. Clin. Endocrinol. Metab.,
73,746-751.
Khokha, R., Waterhouse, P., Yagel, S. et al. (1989) Antisense RNA-induced
reduction in murine TIMP levels confers oncogenicity on Swiss 3T3 cells.
Science. 243, 947-950.
Kimber, SJ., Bentley, J., Ciemerych, M. et al. (1994) Expression of N-CAM
in fertilised pre- and peri-implantation and parthenogenetically activated
mouse embryos.
Eur.
J. Cell Biol, 63, 102-113.
Kirchhofer, D., Languino, L.R., Ruoslahti, E. et al. (1990) (J2P1 integrins
from different cell types show different binding specificities. J. Biol. Chem.,
265,615-618.
Klein, G., Langegger, R., Timpl, R. et al. (1988) Role of laminin A chain in
the development of epithelial cell polarity. Cell, 55,
331-341.
Kojima, K., Kanzaki, H., Iwai, M. et al. (1994) Expression of leukemia
inhibitory factor in human endometrium and placenta. Biol.
Reprod.,
50,
882-887.
Korhonen, M., Ylanne, J., Laitinen, L. et al. (1991) Distribution of the apO^
integrin subunits in human developing and term placenta. Lab. Invest., 65,
347-56.
Krissansen, G.W., Elliot, MJ., Lucas, CM. et al. (1990) Identification of a
novel uitegnn p subunit expressed on cultured monocytes (macrophages).
Evidence that one a subunit can associate with multiple P subunits. J. Biol.
Chem.,
265, 823-830.
Kubo, H., Spindle, A. and Pedersen, R.A. (1981) Inhibition of mouse blastocyst
attachment and outgrowth by protease inhibitors. J. Exp. Zool, 216,
445-451.
KUhn and Eble (1994) The structural basis of integrin-ligand interactions.
Trends Cell Biol, 4,
256-261.
Laird, S.M., Tuckerman, E., Li, T.C. et al. (1994) Stimulation of endometrial
ephithelial cell interleukin 6 production by interleukin 1 and placenta]
protein 14. Hum.
Reprod.,
9, 1339-1343.
Languino, L.R., Gehlsen, K.R., Wayner, E. et al. (1989) Endothelial cells use
OC2P1 integrin as a laminin receptor. J. Cell. Biol, 109, 2455-2462.
Lasky, L.A (1992) Selectins: Interpreters of cell-specific carbohydrate
information during inflammation. Science, 258, 964-969.
Laudanna, C, Campbell, J J. and Butcher, E.C. (1996) Role of chemoattractant-
activated leukocyte adhesion through integrins. Science, 271,
Lessey, B.A. and Castelbaum, AJ. (1995) Integrins in the endometrium.
Reprod.
Med. Rev., 4, 43-58.
Lessey, B.A., Damjanovich, L., Coutifaris, C. et al. (1992) Integrin adhesion
molecules in the human endometrium. Correlation with the normal and
abnormal menstrual cycle. J. Clin, Invest., 90, 188-195.
Lessey, B.A., Castelbaum, AJ., Buck, C.A. et al. (1994a) Further
characterization of endometrial integrins during the menstrual cycle and in
pregnancy. Fertil. Steril, 62, 497-506.
Lessey, B.A., Castelbaum, AJ., Sawin et al. (1994b) Aberrant integnn
expression in the endometnum of women with endometriosis. J. Clin.
Endocrinol. Metab., 79, 643-649.
Lyall, F, Greeer, I.A., Boswell, et al. (1995) Expression of cell adhesion
molecules in placentae from pregnancies complicated by pre-eclampsia and
intrauterine growth retardation. Placenta, 16, 579-587.
Lockwood, C J., Knkun, G., Papp, C. et
al.
(1994) The role of progestationally
regulated stromal cell tissue factor, and type-1 plasminogen activator
inhibitor (PAI-1) in endometrial hemostasis and menstruation. Ann, N.Y.
Acad.
Sci, 734, 57-79.
Loke, Y.W., Gardner, L., Burland, K. et al. (1989) Laminin in human
trophoblast-decidua interaction. Hum.
Reprod.,
4, 457—463.
Lotz, M.M., Korzelius, C.A. and Mercurio, A.M. (1990) Human colon
carcinoma cells use multiple receptors to adhere to laminin: Involvement
of 0(^4 and
o2Pi
integrins. Cell. Reg., 1, 249-257.
Lubbert, M., Mantovani, L., Lindeman, A. etal. (1991) Expression of leukemia
inhibitory factor is regulated in human mesenchymal cells. Leukemia, 5,
361-365.
Lucore, C.L., Fujii, S., Wun, T.C. et al. (1988) Regulation of the expression
of Type 1 plasminogen activator inhibitor in HepG2 cells by epidermal
growth factor. J. Biol. Chem., 263, 15848.
Martin, G.R. and Timpl, R. (1987) Laminin and other basement membrane
components. Ann. Rev. Cell Biol, 3, 57-85.
Masuhiro, JC, Matsuzaki, N., Nishino, E. et al (1991) Trophoblasl-derived
interleukin-1 (IL-1) stimulates the release of human chorionic gonadotrophin
by activating IL-6 and IL-6 receptor system in first trimester human
trophoblasts. J. Clin. Endocrinol Metab., 72,
594-601.
421
by guest on July 24, 2011molehr.oxfordjournals.orgDownloaded from

C.Simdn of al.
Matrisian, L.M. (1990) Melalloproteinases and their inhibitors in matrix
remodeling. Trends Genet., 6, 121-125.
McNaul, K.L., Chartrain, N., Lark, M. et al. (1990) Discordinate expression
of stromelysin, collagenase and tissue inhibitor of metalloproteinases-l in
rheumatoid human synovia! fibroblasts. J. Biol. Chem., 265, 17238-17245.
Mengozzi, M., Bertini, R., Sironi, M. et al. (1991) Inhibition by interleukin-
1 receptor antagonist of in vivo activities of interleukin-1 in mice. Lvm.
Cyt. Res., 10, 405-07.
Mignatti, P., Robbins, E. and Rifkin, D.B. (1986) Tumor invasion through the
human amniotic membrane: requirement for a proteinase cascade. Cell, 47,
Mignatti, P., Tsuboi, R., Robbins, E. et al. (1989) In vitro angiogenesis on the
human amniotic membrane: requirement for basic fibroblast growth factor-
induced proteinases. J. Celt. Biol., 108, 671-682.
Miliam. S.B., Magnuson, V.L., Steffensen, B. et al. (1991) IL-ip and
prostaglandins regulate integrin mRNA expression. /. Cell. Physiol., 149,
173-183.
Mylona, P, Kielty, CM, Hoyland, J.A et al. (1995) Expression of type VI
collagen mRNA in human endometrium. J.
Reprod.
Fenil. in press.
Murphy, G., Reynolds, JJ. and Werb, Z. (1985) Biosynthesis of tissue inhibitor
of metalloproteinases by human fibroblast in culture. J. Biol. Chem., 260,
3079-83.
Murray, R., Lee, F. and Chiu, C.P. (1990) The genes for leukemia inhibitory
factor and interleukin-6 are expressed in mouse blastocyst prior to the
onset of hemopoiesis. Mol. Cell. Biol., 10, 4953-4956.
Nishimura, S.L., Sheppard, D. and Pytela, R. (1994) Integrin c^Pg. Interaction
with vitronectin and functional divergence of the Pg cytoplasmic domain.
J. Biol. Chem., 269, 28708-28715.
Ohlsson, K., BjOrk, P., Bergenfeldt, M et al. (1990) Interleukin-I receptor
antagonist reduces mortality from endotoxin shock. Nature, 348, 550-552.
Osbom, L., Hession, C, Tizard, R. et al. (1989) Direct expression cloning of
vascular cell adhesion molecule 1, a cytokine-induced endothelial protein
that binds lymphocytes. Cell, 59, 1203-1211.
Ossowski, L., Clunie. G., Masucci, M.T. et al. (1991) In vivo paracrine
interaction between urokinase and its receptor; effect on tumor cell invasion.
J. Cell Biol., 115, 1107-1112.
Overall, CM., Wrana, J.L. and Sodek, J. (1991) Transcriptional and post-
transcriptional regulation of 72-kDa gelatinase/type IV collagenase by
transforming growth factor pi in human fibroblast. J. Biol. Chem., 266,
14064-14071.
Pampfer, S., Tabibzadeh, S., Chuan, F.-C. et al. (1991) Expression of colony-
stimulating factor-1 (CSF-I) messenger RNA in human endometrial glands
during the menstrua] cycle: Molecular cloning of a novel transcript that
predicts a cell surface from of
CSF-1.
Mol. Endocnnol., 5, 1931-1938.
Panayotou, G., End, P., Aumailley, M. et al. (1989) Domains of laminin with
growth factor activity. Cell, 56,
93-101.
Paulesu, L., Romagnoli, R., Marchetti, M. et al. (1995) Cytokines in the
viviparous reproduction of squamata reptiles: Interleukin-I a (IL-la) and
IL-ip in placental structures of a skink. Placenta, 16, 193-206
Pierschbacher, M.D. and Ruoslahti, E. (1984) The cell attachment activity of
fibronectin can be duplicated by small fragments of the molecule. Nature,
309,
30-33.
Ploug, M., Behrendt, N., Lober, D. et al. (1991) Protein structure and
membrane anchorage of
the
cellular receptor for urokinase-type plasminogen
activator. Semin. Thromb. Hemost.. 17, 183-193.
Pober, J.S., Gimbrone. Jr M.A.. Lapierre, L.A. et al. (1986) Overlapping
patterns of activation of human endothelial cells by interleukin I, tumor
necrosis factor and immune interferon. J. Immunol.. 137, 1893-1896.
Pollard, J.W., Bartocci, A., Arceci, R. et al. (1987) Apparent role of the
macrophage growth factor, CSF-I, in placental development Nature, 330,
484-^86.
Pollard, J.W., Hunt, J.S., Wiktor-Jedrzejczak. W. et al. (1991) A pregnancy
defect in the osteopetrotic (op/op) mouse demonstrates the requirement for
CSF-I in female fertility. Dev. Biol., 148, 273-83.
Policy, MJ. Phillips, M.L., Wayner, E. et
al.
(1991) CD62 and endothelial cell-
leukocyte adhesion molecule I(ELAM-1) recognize the same carbohydrate
ligand, sialyl Lewis x. Proc. Natl.
Acad.
Sci. USA, 88, 10327.
Postigo. A.A.. Sanchez-Mateos. P.. Lazarovits, A.I. et al. (1993) a$j integrin
mediates B cell binding to fibronectin and vascular cell adhesion molecule-
1.
Expression and function of a4 integrins on human B lymphocytes. J.
Immunol.. 151, 2471-2483.
Pytela, R., Pierschbacher, M.D. and Ruoslahti, E (1985a) Identification and
isolation of a 140 kilodalton cell surface glycoprotein with properties of a
fibronectin receptor. Cell, 40, 191-198.
Pytela, R., Pierschbacher, M.D. and Ruoslahti. E (1985b) A 125/115 Kd cell
surface receptor specific for vitronectin interacts with the arg-gly-asp
adhesion sequence derived from fibrinectin. Proc. Natl.
Acad.
Sci. USA.
82,
5766-5770.
Quax, P.H.A., Pedersen, N., Masucci. M.T. et al. (1991) Complementation
between urokinase-producing and receptor-producing cells in extracellular
matrix degradation. Cell. Reg.. 2, 793-803.
Queenan, J.T.. Kao, L.C., Arboleda, CE. et al. (1987) III. Regulation
of urokinase type plasminogen activator production by cultured human
cytotrophoblast. J. Biol. Chem., 262, 10903-10906.
Raines, E.W.. Dower, and S.K and Ross, R. (1989) Interleukin-I mitogenic
activity for fibroblasts and smooth muscle cells is due to PDFD-AA.
Science, 243, 393-6.
Regenstreif, LJ. and Rossant, J. (1989) Expression of the c-fms proto-
oncogene and of the cytokine. CSF-I, during mouse embryogenesis. Dev.
Biol., 133, 284-294.
Reinholt, F.P., Hultenby, K., Oldberg, A. et al. (1990) Osteopontin - a possible
anchor for osteoclasts to bone. Proc. Natl
Acad.
Sci. USA, 87, 4473-4475.
Roeb,
E., Graeve, L., Mullberg, J. et al. (1994) TIMP-I protein expression is
stimulated by IL-ip and IL-6 in primary rat hepatocytes. FEBS Lett.. 349,
45-49.
Ruegg C, Postigo A.A., Sikorski E.E. et al. (1992) Role of integrin a,py
<X»Pp
in lymphocyte adherence for fibronectin an VCAM-1 and in homotypic
cell clustering. J. Cell. Biol., 117, 179-189.
Ruoslahti, E. (1991a) Integnns as receptors for extracellular matrix. In Hay.
E.D. (ed.), Cell Biology of Extracellular Matnx. Plenum Press, New York,
p.
343.
Ruoslahti, E. (1991b) Integrins. J. Clin. Invest.. 87, 1-5.
Ruoslahti, E. and Pierschbacher, M.D. (1987) New perspectives in cell
adhesion: RGD and integrins. Science, 238, 491-497.
Ruoslahu, E., Noble, N.A., Kagami, S. et al. (1994) Integrins. Kidnev Int.,
45 (Suppl. 44), S17-S22.
Sahakian, V, Anners, J., Haskill. S. et al. (1993) Selective localization of
interleukin-1 receptor antagonist in eutopic endometrium and endometnotic
implants. Fertil. Steril., 60, 276-279
Sanford, T.R., De, M.and Wood, G.W. (1992) Expression of colony-stimulating
factors and inflammatory cytokines in the uterus of
CD I
mice during days
I to 3 of pregnancy. J.
Reprod.
Fertil., 94, 213-220.
Santala, P. and Heino. J. (1991) Regulation of integrin-type cell adhesion
receptors by cytokines. J. Biol. Chem., 266, 23505-23509.
Sappino, A.P., Huarte, J., Belin, D. et al. (1989) Plasminogen activators in
tissue remodeling and invasion: mRNA localization in mouse ovaries and
implanting embryos. /. Cell. Biol., 109, 2471-2479.
Sastry. S.K and Horwitz, A.F. (1993) Integnn cytoplasmic domains: mediators
of cytoskeletal linkages and extra- and intracellular initiated transmembrane
signaling. Curr. Opin. Cell Biol., 5,
819-831.
Sato.
T, Ito, A.. Mori, Y. et al. (1991) Hormonal regulation of collagenolysis
in uterine cervical fibroblasts. Modulation of synthesis of procollagenase,
prostromelysin and tissue inhibitor of metalloproteinases by progesterone
and oestradiol-17p. Biochem. J., 275, 645-650.
Sawai. K., Matsuzaki. N.. Kameda, T. et al. (1995) Leukemia inhibitory factor
produced at the fetomatemal interface stimulates chononic gonadotropin
production: its possible implication during pregnancy, including
implantation period. J. Clin. Endocrinol. Metab., 80, 1449-1456.
Schaller and Parson. (1994) Focal adhesion kinase: an integnn-linked protein
tyrosine kinase. Trends Cell Biol.. 3, 258-262.
Schatz, F. and Lockwood, CJ. (1993) Progestin regulation of plasminogen
activator inhibitor type I in primary cultures of endometrial stromal and
decidual cells. J. Clin. Endocrinol. Metab., 77, 621-625.
Schatz, F.. Aigner, S., Papp. C. et al. (1995) Plasminogen activator activity
during decidualization of human endometrial stromal cells is regulated
by plasminogen activator inhibitor I. J. Clin. Endocrinol. Metab.. 80,
2504-2510.
Schleef.
R.R., Wagner. N.V. and
Loskutoff.
DJ. (1988) Detection of both
type 1 and type 2 plasminogen activator inhibitors in human cells. J. Cell.
Physiol.. 134, 269-274.
Schleimer.
R.P.
and Rutledge, B.K. (1986) Cultured human vascular endothelial
cells acquire adhesiveness for neutrophils after stimulation with interleukin
I. endotoxin, and tumor promoting phorbol diesters. J. Immunol.. 136,
649-654.
Seifer, D.B., Romero, R.. Berlinsky. D. et al. (1993) Absence of cytokine
production by preimplantation human embryos. In 40th Annual Meeting
Society for Gynecological Investigation, p. 320.
Shadiak. A.M.. Hart, R.P.. Carlson. CD. et al. (1993) Interleukin-1 induces
422
by guest on July 24, 2011molehr.oxfordjournals.orgDownloaded from

Cytokines-adhesion molecules-invasive proteinases
substance P in sympathetic ganglia through the induction of leukemia
inhibitory factor (LIF). J. Neurosci.. 13, 2601-2609.
Shcppard. D.. Rozzo. C. Staarr. L. et
al.
(1990) Complete ammo acid sequence
of a novel integrin P subunit (P^ identified in epithelial cells using the
polymerase chain reaction. J. Biol. Chem.. 265, 11502-11507.
Sheppard. D.. Cohen. D.S.. Wang. A. et al. (1992) Transforming growth factor
p differentially regulates expression of integrin subunits in guinea pigs
airway epithelial cells. J. Biol. Chem.. 267, 17409-17414.
Sherman. M.I. (1988) Methods in Mammalian Reproduction. In Daniels, J.C.
Jr.. (ed.). New York. Academic Press, pp. 247-257.
Sheth. K.V.. Roca. G.L.. Al-Sedairy. S.T. el
al.
(1991) Prediction of successful
embryo implantation by measuring interleukin-1-alpha and immuno-
suppressive factors) in preimplantation embryo culture fluid. Fenil. Sterii,
55,
952-957.
Shimonovitz. S.. Hurwitz. A.. Dushnik, M el al. (1994) Developmental
regulation of the expression of 72 and 92 Kd type IV collagenases in
human trophoblast: a possible mechanism for control of trophoblast
invasion. Am. J. Obst. Gynecol.. 171, 832-838.
Shull, M.. Ormsby, I., Kier, A.B.. et al. (1992) Targeted disruption of the
mouse TGF-pl gene results in multifocal inflammatory disease. Nature,
359,
693-699.
Sim6n. C, Gomez, E.. Mir, A. et
al.
(1992) Glucocorticoid treatment decreases
sera embryotoxicity in endometriosis patients. Fertil. Sterii., 58, 284-289.
Simon. C. Piquette, G., Frances, A. et al. (1993a) Localization of mterleukin-
1 type I receptor and interleukin-1 beta in human endometnum throughout
the menstrua] cycle. J. Clin. Endocrinol. Metab., 77, 549-555.
Sim6n, C, Piquette, G.N., Frances, A. et al. (1993b) Interleukin-1 type
I receptor messenger ribonucleic acid (mRNA) expression in human
endometnum throughout the menstrua] cycle. Fertil. Sterii., 59, 791-796.
Sim6n, C, Frances, A, Piquette, G.N. et al. (1994a) Embryonic implantation
in mice is blocked by Interleukin-1 receptor antagonist (IL-Ira).
Endocrinology, 134,521-528.
Sim6n, C, Frances, A., Piquette. G.N. et al. (1994b) Interleukin-1 system in
the matemo-trophoblast unit in human implantation: immunohistochemical
evidence for autocrine/paracnne function. J. Clin. Endocnnol. Metab., 78,
847-854.
Sim6n, C, Piquette, G.N., Frances, A. et
al.
(1994c) The effect of Interleukin-
I beta (IL-lp) on the regulation of IL-I Receptor type I and IL-I beta
messenger ribonucleic acid (mRNA) levels and protein expression in
cultured human endometrial stromal and glandular
cells.
J. Clin. Endocrinol.
Metab., 78, 675-682.
Simon, C, Frances, A., Yon Lee, B. et al. (1995a) ImmunohistochemicaJ
localization, identification and regulation of the Interleukin-1 receptor
antagonist in the human endometrium. Mol. Hum.
Reprod.,
1, see Hum.
Reprod.,
10, 2472-2477.
Sim6n, C, Frances, A., Pellicer, A. et al. (1995b) Cytokines in Implantation.
Semtn.
Reprod.
Endocrinol., 13,
142-151.
Simon, C, Pellicer, A., and Polan, M.L. et al. (1995c) Interleukin-1 system
crosstalk between embryo and endometrium in implantation. Hum.
Reprod.,
10 (Suppl. 2), 43-54.
Sims,
J.E., March, C.J., Cosman, D. et al. (1988) cDNA expression cloning
of the 1L-1 receptor, a member of
the
immunoglobulin superfamily. Sci>ncr,
241,
585-9.
Sims,
J.E., Gayle, M.A., Slack, J.L. et al. (1993) Interleukin-1 signalling
occurs exclusively via the type I Receptor. Proc. Natl.
Acad.
Sci. USA, 90,
6155-6159
Smith, J.W., Vestal, DJ., Irwin, S.V. el al. (1990) Purification and functional
characterization of integrin (XyPj. An adhesion receptor for vitronectin. J.
Biol. Chem., 265, 11008-11013.
Sorokin. L., Sonnenberg, A., Aumailley, M. el al. (1990) Recognition of the
laminin E8 cell-binding site by an integrin possessing the
OLf,
subunit is
essential for epithelial polarization in developing kidney tubules. J. Cell.
Biol.. Ill, 1265-1273.
Springer, T.A. (1990) Adhesion receptors of the immune system. Nature, 346,
425^133.
Staatz, W.D.. Raipara, S.M., Wayner, E.A. et al. (1989) The membrane
glycoprotein la-Ilia (VLA-2) complex mediates the Mg++ dependent
adhesion of platelets to collagen. J. Cell. Biol., 108, 1917-1924.
Steelee, G.L., Currie, W.D., Leung, E. et al. (1992) Rapid stimulation of
human chorionic gonadotropin secretion by interleukin-ip from perifused
first trimester trophoblast. J. Clin. Endocrinol. Metab.. 75, 783-788.
Stetler-Stevenson, W.G., Krutzsch, H.C. and Liotta, L.A. (1989) Tissue
inhibitor of metalloproteinase (TIMP-2). A new member of the
metalloproteinase inhibitor family. /. Biol. Chem., 264, 17374-17378.
Stetler-Stevenson. W.G.. Brown, P.D.. Onisto, M. el
al.
(1989) Tissue inhibitor
of metalloproteinases-2 (TIMP-2) mRNA expression in tumor cell lines
and human tumor tissues. J. Biol. Chem.. 265, 13933-13938.
Stewart, C.L.. Kaspar. P.. Brunei. L.J. et al. (1992) Blastocyst implantation
depends on maternal expression of leukaemia inhibitory factor. Nature,
359,
76-79.
Strickland. S.. Reich. E. and Sherman. M.I. (1976) Plasminogen activator
in early embryogenesis: enzyme production by trophoblast and parietal
endoderm. Cell. 9, 231-240.
Strickland, D.K., Ashcom. J.D. Williams, S. et al. (1991) Primary structure
of a2-macroglobulin receptor-associated protein. J. Biol. Chem., 266,
13364-13369.
Stricklin, G.P. and Welgus. H.G. (1983) Human skin fibroblast collagenase
inhibitor. Purification and biochemical characterization. J. Biol. Chem.,
258,
12252-12258.
Sutherland, A.E., Calarco. P.G. and Damsky, C.H. (1993) Developmental
regulation of integrin expression at the time of implantation in the mouse
embryo. Development, 119, 1175-1186.
Tabibzadeh. S. (1991) Human endometrium: an active site of cytokine
production and action.
Endocr.
Rev., 12, 272-290.
Tabibzadeh, S. (1992) Patterns of expression of integrin molecules in human
endometrium throughout the menstrual cycle. Hum.
Reprod.,
7, 876-882.
Tabibzadeh, S. and Babaknia, A. (1995) The signals and molecular pathways
involved in implantation, a symbiotic interaction between blastocyst and
endometrium involving adhesion and tissue invasion. Mol. Hum.
Reprod.,
1,
see Hum.
Reprod.,
10, 1579-1602.
Tabibzadeh, S. and Sun, X.Z. (1992) Cytokine expression in human
endometrium throughout the menstrual cycle. Hum.
Reprod..
7, 1214—1221.
Tabibzadeh, S., Santhanam, U., Schgal, P.B. et al. (1989) Cytokine-induced
production of IFN-p2/IL-6 by freshly explanted human endometnal stromaJ
cells modulation by l7P-estradiol. J. Immunol., 142, 3134-3139.
Tabibzadeh, S., Kaffka, K.L., Satyaswaroop, P.G. et al. (1990) Interleukin-1
(IL-1) regulation of human endometrial function: presence of
IL-1
receptor
correlates with IL-1 -stimulated prostaglandin E2 production. J. Clin.
Endocrinol. Metab., 70, 1000-1006.
Tabibzadeh, S., Kong, Q.F. and Babaknia, A (1994) Expression of adhesion
molecules in human endometrial vasculature throughout the menstrual
cycle. J. Clin. Endocrinol. Metab., 79, 1024-1032.
Tabibzadeh, S., Zupi, E., Babaknia, A. et al. (1995) Site and menstrual cycle-
dependent expression of proteins of the tumor necrosis factor (TNF)
receptor family, and a BCL-2 oncoprotein and phase-specific production
of TNFa in human endometrium. Hum.
Reprod.,
10, 277-286.
Tackacs, L., Kavacs, EJ., Smith, M.R. et al. (1988) Detection of IL-la and
IL-ip gene expression by in situ hybridization. Tissue localization of IL-1
mRNA in the normal C57BL/6 mouse. J. Immunol., 141, 3081-3094.
Takeichi, M. (1988) The cadhenns: cell-cell adhesion molecules controlling
animal morphogenesis. Development, 102, 639-655.
Takeichi, M. (1991) Cadherin cell adhesion receptors as a morphogenetic
regulator. Science, 251, 1451-1455.
Tarlatzis, B.C., Bili, H., Daniilidis, M. et al. (1994) Interleukin production by
human preimplantation embryos (Abstr.) Feriil. Sterii., 63 (Suppl.), 0-165.
Tartakovsky, B., Goldstein, O. and Brosh, N. (1991) Colony stimulating
factor-l blocks early pregnancy in mice. Biol.
Reprod.,
44, 906-912.
Taskin, O., Brown, R.W., Young, D.C. et al. (1994) High doses of oral
contraceptives do not alter endometrial aj and 0^3 integrins in the late
implantation window. Fenil. Sterii., 61, 850-855.
Thomson. B.M., Atkinson, SJ., Reynolds, JJ. et al. (1987) Degradation
of type I collagen films by mouse osteoblast is stimulated by 1,25
dihydroxyvitamin D3 and inhibited by human recombinant TIMP (tissue
inhibitor of metalloproteinases). Biochem. Biophys. Res. Commun., 148,
596-602.
Tiemeyer, M. et al. (1991) Carbohydrate ligands for endothelial-leukocyte
adhesion molecule 1. Proc. Nail.
Acad.
Sci USA. 88, 1138.
Tiisala, S., Paavonen, T. and Renkonen, R. (1995) CI4P7 and 0^7 integrins
associated with intraepithelial and mucosal homing, are expressed on
macrophages. Eur. J. Immunol., 25, 411—417.
Tortosa, C. G., Vargas, M L., Cimara, M. et al. (1993) Expression of adhesion
molecules by endothelia] cells of early human decidua.
Virchows
Archiv A.
Paihol. Anal.. 423, 287-290.
Turpeenniemi-Hujanen, T, Ronnberg, L., Kauppila, A. et al. (1992) Laminin
in the human embryo implantation: analogy to the invasion by malignant
cells.
Fertil. Sterii., 58, 105-113.
van der Linden, PJ.Q., de
Goeij,
A.F.P.M., Dunselman, G.AJ. et al. (1995)
Expression of cadherins and integrins in human endometrium throughout
the menstrual cycle. Fertil. Sterii, 63, 1210-1216.
423
by guest on July 24, 2011molehr.oxfordjournals.orgDownloaded from

C.Sim6n et al.
van Hinsbergh, V.W.M., Kooistra, T., van der Berg, E.A. et al. (1988) TNF
increases the production of PAI in human endothelial cells in vitro and in
rats in vivo.
Blood,
72, 1467.
van Le, L., Oh, S-T., Anners, J.A. et al. (1992) Interleukin-l inhibits growth
of normal human endometrial stromal cells. Obstet. Gynecol., 80,405-409.
van Wart, H.E. and Birkedal-Hansen, H. (1990) The cysteine switch: a principle
of regulation of metalloproteinase activity with potential applicability to
the entire matrix metalloproteinase gene family. Proc. Nail. Acad Sci.
USA,
87, 5578-5582.
Vestweber, D. (1992) Selectins: cell surface lectins which mediate the binding
of leukocytes to endothelial cells. Semin. Cell Bioi, 3, 211-220.
Vilcek, J. and Le, J. (1991) Immunology of cytokines: an introduction. In
Thompson, A. (ed.). The Cytokine Handbook. Academic Press Inc., San
Diego, pp. 1-18.
Vogel, B.E., Tarone, G., Giancotti, EG. et al. (1990) A novel fibrine receptor
with an unexpected subunit composition (OyPi). J. Biol. Chem., 265,
5934-5937.
Vukicevic, S., Luyten, F.P., Kleinman, H.K. et al. (1990) Differentiation of
canalicular cell processes in bone cells by basement membrane matrix
components: regulation by discrete domains of laminin. Cell, 63, 437^*45.
Wang, X., Feuerstein, GZ, Gu, J-L. et al. (1995) Interleukin-1 p induces
expression of adhesion molecules in human vascular smooth muscle cells
and enhances adhesion of leukocytes to smooth muscle cells.
Atherosclerosis, 115, 89-98.
Ward, R.V., Hembry, R.M., Reynolds, JJ. et al. (1991) The purification of
tissue inhibitor of metalloproteinases-2 from its 72 kDa progelatinase
complex. Biochem. J., 278, 179-187.
Wayner, E.A. and Carter, W.G. (1987) Identification of multiple cell adhesion
receptors for lagen and fibronectin in human fibrosarcoma cells possessing
unique a and common P units. J. Cell. Bioi, 195, 1873-1884.
Weber, G.F, Ashkar, S., Glimcher, MJ. etal. (1996) Receptor-ligand interaction
between CD44 and osteopontin (Eta-1). Science, 271, 509-512.
Weinacker, A., Chen, A., Agrez, M. et al. (1994) Role of the integrin a^
in cell attachment to fibronectin. Heterologous expression of intact and
secreted forms of the receptor. J. Biol. Chem., 269, 6940-6948.
Wetzler, M., Talpaz, M., Lowe, D.G. et al. (1991) Constitutive expression of
leukemia inhibitory factor RNA by human stromal cells and modulation
by IL-1, TNF-a, and TGF-p. Exp. Hematol., 19,
347-351.
Wewer, U., Faber, M., Liotta, L. et al. (1985) Immunochemical and
ultrastructural assessment of the nature of the pericellular basement
membrane of human decidual cells. Lab. Invest., 53, 624-633.
Wickham, TJ., Mathias, P., Cheresh, D.A. et al. (1993) Integrins Ovfo and
(X5P3 promote adenovirus intemalization but not virus attachment. Cell, 73,
309-319.
Williams, R.L., Hilton, DJ., Pease, S. et al. (1988) Myeloid leukaemia
inhibitory factor maintains the developmental potential of embryonic stem
cells.
Nature, 336, 684-687.
Wojta, J., Nakamura, T., Fabry, A. et al. (1994) Hepatocyte Growth Factor
stimulates expression of plasminogen activator inhibitor type 1 and Tissue
factor in HepG2 Cells.
Blood,
84, 151-157.
Yagel, S., Lala, P.K., Powell, W.A. et at. (1989) Interleukin-l stimulates
human chorionic gonadotropin secretion by first trimester human
trophoblast. J. Clin. Endocrinol. Metab., 68, 992-995.
Yagel, S., Geva, T.E., Solomon, H. et al. (1993) High levels of chorionic
gonadotropin retard first trimester trophoblast invasion in
vitro
by decreasing
urokinase plasminogen activator and collagenase activities. J. Clin.
Endocrinol. Metab., 77, 1506-1511.
Yang, Y.C., Tsai, S., Wong, G.G. et al. (1988) Intcrleukin-1 regulation of
hematopoietic growth factor production by human stromal fibroblasts.
J. Cell. PhysioL, 134, 292-296.
Yokosaki, Y., Palmer, E.L., Prieto, A.L. et al. (1994) The integrin a,p,
mediates cell attachment to a non-RGD site in the third fibronectin type
III repeat of tenascin. J. Biol. Chem., 269, 26691-26696.
Zhou. Y, Damsky, C.H., Chiu, K. et al (1993) Preeclampsia is associated
with abnormal expression of adhesion molecules by invasive
cytotrophoblasts. /. Clin. Invest., 91, 950-960.
Zini, J.M., Murray, S.C., Graham. C.H., et al. (1992) Characterization of
urokinase receptor expression by human placenta! trophoblast.
Blood.
79,
2917-2929.
Zolti, M., Ben-Rafael, Z., Meirom, R. et al. (1991) Cytokines involvement in
oocytes and early embryos. Fertil. Steril, 56, 265-272.
Received on December 13, 1995; accepted on March 20, 1996
424
by guest on July 24, 2011molehr.oxfordjournals.orgDownloaded from