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Comparative Study of Interstitial Cells of Cajal
Abstract
The cells present in the alimentary canal, contacting both nerve endings and smooth muscle cells and named interstitial cells of Cajal, show different ultrastructural features. A comparative study has been performed in order to see if these differences can be related to the animal species studied or to the interstitial cell localizations inside the muscle wall of the various levels of the alimentary canal or to their contacts with other cells. Only mammals were considered, and rat, mouse, hedgehog and man have been studied. All the localizations where interstitial cells of Cajal have usually been found were considered: esophagus (body and lower sphincter), stomach (gastric extent of the lower esophageal sphincter, fundus and corpus), small intestine and colon. From this comparison a correlation was found between the morphology and the location of interstitial cells. On the contrary, the morphological differences existing between animal species do not seem to be that consistent. Moreover, the number of contacts between interstitial cells and between these and smooth muscle cells and nerve endings varies according to the interstitial cell location and morphology. It is concluded that the chain nerve endings----interstitial cells of Cajal----smooth muscle cells is not morphologically identical at each gastrointestinal level, and this finding is considered very important in interpreting the role played by the interstitial cells of Cajal in gastrointestinal motility.
... The presence of ICC-SMP ( Fig. 9) has been documented previously in the mouse (Faussone-Pellegrini 1985, 1987a, 1987bRumessen 1994) and the present study confirms these descriptions. X-gal deposits in ICC-SMP were not always seen, and they were often weak (Fig. 9). ...
... As in the mouse colon, ICC-SMP in these species show predominately myoid ultrastructural features. The ultrastructural features of ICC-MP have not been systematically described in mice before (Faussone-Pellegrini 1987a), and ICC-SS and ICC-CM have never been characterized by electron microscopy. They have a more fibroblast-like ultrastructure than ICC-SMP, corresponding to descriptions in rats and rabbits (Faussone-Pellegrini 1987a;Komuro 1982). ...
... The ultrastructural features of ICC-MP have not been systematically described in mice before (Faussone-Pellegrini 1987a), and ICC-SS and ICC-CM have never been characterized by electron microscopy. They have a more fibroblast-like ultrastructure than ICC-SMP, corresponding to descriptions in rats and rabbits (Faussone-Pellegrini 1987a;Komuro 1982). Similarly, ICC-MP in the mouse small intestine have less pronounced myoid ultrastructural features in comparison with ICC in the deep muscular plexus (Thuneberg 1982;Rumessen et al. 1982;Rumessen 1994). ...
The roles of the interstitial cells of Cajal in the stomach and intestine are becoming increasingly clear. Interstitial cells of Cajal in the colon are less well known, however. We studied the development and distribution of the interstitial cells of Cajal in the mouse colon, using the tyrosine kinase receptor Kit as a marker. Sections and whole mounts were studied by confocal microscopy after double immunofluorescence with specific antibodies. The ultrastructure of Kit-expressing cells was examined by electron microcopy in Kit
W-lacz
/+ transgenic mice, which carry the lacz gene inserted in place of the first exon of the Kit gene. In the subserosa, the interstitial cells of Cajal formed a two-dimensional plexus. In the myenteric area, the interstitial cells of Cajal formed a dense plexus that gradually merged with the interstitial cells of Cajal in the outer half of the circular muscle. The inner half of the circular layer was devoid of interstitial cells of Cajal whereas in the submuscular region the interstitial cells of Cajal formed a two-dimensional plexus. Tertiary nerves with various chemical codings closely followed interstitial cell of Cajal processes. By electron microscopy, Kit-expressing cells in the outer parts of the musculature had scattered caveolae, inconspicuous basal lamina and numerous mitochondria, whereas in the submuscular region they had more pronounced myoid features. Kit-expressing cells in the mouse colon are identifiable as interstitial cells of Cajal by their ultrastructure. The interstitial cells of Cajal in the mouse colon mature postnatally. They are organized into a characteristic plexus, close to the nerves with various chemical codings.
... f No c-kit-positive cells can be seen in the centre of the denervated region; 70 days after BAC treatment. Bars 50 μm (a-f) features of these cells (Faussone-Pellegrini 1987a, 1992Faussone-Pellegrini and Thuneberg 1999;Komuro 1999): an oval nucleus, a moderately electron-dense cytoplasm, small cisternae of both the rough (RER) and smooth (SER) endoplasmic reticulum, a small Golgi apparatus, and several mitochondria (Fig. 2a,c). These cells were in contact with each other and with both nerve endings and smooth muscle cells. ...
... Moreover, similar to the mouse ICC-MP, these cells exhibit peg-and-socket contacts with the smooth muscle cells (Faussone-Pellegrini and Thuneberg 1999). Therefore, in adulthood, new ICC seem to differentiate and acquire some of their typical features after contacting nerve endings, presumably via the same mechanism as that occurring during fetal life (Faussone-Pellegrini 1985, 1987a. The observation that reinnervation is accompanied by the appearance of cells that have fibroblast-like features and that progressively make contact with nerve endings and smooth muscle cells is in accord with the finding that, during embryonic life, the interaction between undifferentiated cells and nerve endings is a condition for their differentiation into ICC (Faussone-Pellegrini 1985, 1987aFaussone-Pellegrini et al. 1996;Sanders et al. 1999). ...
... Therefore, in adulthood, new ICC seem to differentiate and acquire some of their typical features after contacting nerve endings, presumably via the same mechanism as that occurring during fetal life (Faussone-Pellegrini 1985, 1987a. The observation that reinnervation is accompanied by the appearance of cells that have fibroblast-like features and that progressively make contact with nerve endings and smooth muscle cells is in accord with the finding that, during embryonic life, the interaction between undifferentiated cells and nerve endings is a condition for their differentiation into ICC (Faussone-Pellegrini 1985, 1987aFaussone-Pellegrini et al. 1996;Sanders et al. 1999). However, the absence of c-kit positivity for at least up to 70 days after BAC treatment indicates that these ICC have not maturated fully. ...
Ablation of the myenteric plexus in mouse colon with the detergent benzalkonium chloride (BAC) is followed by considerable recovery of the nerves, indicating that this plexus is capable of regeneration and has plasticity. Interstitial cells of Cajal (ICC) are closely associated with enteric nerves, and the acquisition and maintenance of their adult phenotype are nerve-dependent. Little is known about the regenerative processes of ICC or about the possible dependence of these processes on neurons. To address these questions, we ablated the myenteric plexus in the mouse colon with BAC and followed changes in the adjacent ICC (ICC-MP) from day 2 to day 70 after treatment, by using c-kit-immunohistochemistry and electron microscopy. In the untreated area, c-kit-positive cells and ICC-MP with normal ultrastructural features were always present. The region partially affected by BAC contained some c-kit-positive cells, and either normal or vacuolated ICC-MP were observed by electron microscopy. Moreover, at days 60-70, ICC-MP with particularly extended rough endoplasmic reticulum were present in this area. In the treated area, either denervated or reinnervated, c-kit-positive cells were always absent. By day 14 after BAC treatment, nerve fibers had started to grow back into the treated region and, in the reinnervated area, cells with fibroblast-like features appeared and were seen to contact both nerve endings and smooth muscle cells and to acquire some typical ICC features. Thus, ICC are vulnerable to external insult but appear to have some ability to regenerate.
... ICC reached its historical renaissance with the analyses of Thuneberg, who hypothesized that ICC act as intestinal pacemakers and participate in the transmission of impulses to the intestinal musculature, a transmission analogous to that in the heart muscle. Some researchers have provided abundant evidence that ICC are implicated in the generation of slow waves that act as an electrical basis for pacemaking functions (3). Today, ICC are given a central place in research studies aimed at understanding gastrointestinal contractions and elucidating the pathogenesis of various motility disorders. ...
... In the stomach, ICC are more numerous in the corpus and the antrum than in the fundus. They have been observed within the muscle layers, especially the circular ones, appearing as long cells parallel to the longitudinal axis of the muscle bundle, but failing to group on the submucous margin, except as single, scattered cells (3,8). Around the myenteric plexus ICC form a thick network of ramified cells surrounding ganglial cells. ...
The paper reviews the present-day knowledge on the origin, location, morphology, function, and identification of interstitial cells of Cajal (ICC). ICC include several types of mesenchymal cells, spindle-shaped or stellate, found within the musculature of the gastrointestinal tract. Some types of ICC act as pacemakers of the intestinal musculature, while others are implicated in the modulation of enteric neurotransmission. Current methods for ICC identification rely on a combination of ultrastructural characteristics as defined by transmission electron microscopy and immunohistochemical analyses with antibodies to the Kit receptor. ICC play a crucial role in the regular intestinal activity, which is the reason why changes in these cells may lead to various intestinal disorders.
... Several studies on fetal rats showed that there were abnormal innervations of neural plexus in anorectum in ARMs. [10,11] It is noteworthy that despite advances in surgical treatments, voluntary bowel control is frequently poor, with high rates of fecal incontinence and chronic constipation after all types of reconstructive surgery. [12][13][14] To evaluate for defects in neuromuscular architecture in the distal rectum of patients with ARM, we performed histomorphologic, IHC, and Western blot analysis. ...
It remains controversial whether the distal rectal pouch should be either resected or used for reconstruction in anorectoplasty for the treatment of anorectal malformations (ARMs). Hence the aim of this study was to investigate whether ARMs were associated with a global neuromuscular maldevelopment of the terminal rectum specimens.
There were 36 cases of ARMs (25 recto-bulbar fistula and 11 recto-prostatic fistula) and 10 healthy controls. The hematoxylin and eosin and Masson trichrome stain were used to conduct the histologic examination. The immunohistochemistry (IHC) and Western blot were conducted to analyze the neuron-specific enolase (NSE), S-100 protein, interstitial cells of Cajal marker (C-kit) within the rectal specimens in control group and ARM group.
The most frequently observed histologic findings in mucosa were inflammation, congestion, eroded, and hemorrhage in the ARM cases. Submucosal inflammation and congestion were the most common submucosal findings in the ARM cases. Disrupted muscularis propria was observed in 60% of ARM cases. Mature ganglionic cells were reduced and muscularis propria showed reduced and patchy positivity for NSE, S-100, and C-kit protein in ARM group compared to that in control group according to IHC. Western blotting showed the expression levels of NSE, S-100, and C-kit were lower in the ARM group than that in the control group (P < .01).
Histopathologic and IHC findings suggest that the distal rectal pouch has distinct defects in the neuromusculature. So it suggested that ARMs are abnormally developed tissue and need to be resected for better functional outcomes of the remaining gut.
... A u t h o r C o p y distinctive types of pericytes, or are TCs to be recruited as pericytes (Goritz et al., 2011, Suciu et al., 2012). Various research was performed before the TC definition in 2010 (Popescu and Faussone-Pellegrini, 2010), and several reports identified esophageal ICCs (Pellegrini and Cortesini, 1985a, 1985b, 1986 Faussone-Pellegrini, 1987; Berezin et al., 1994; Burns et al., 1997; Rumessen et al., 2001; Zarate et al., 2006; Huizinga et al., 2008; Radenkovic et al., 2010), but not esophageal cells to be later considered TCs. Several studies on esophageal ICCs illustrate the findings by presenting cells with Tp -actually esophageal TCs. ...
Telocytes (TCs) are actually defined as being stromal cells with specific long and thin prolongations, called telopodes (Tp). They were positively identified in various tissues up to now. We report here for the first time the presence of TCs in the structure of esophagus. Such cells were identified under transmission electron microscopy (TEM) in esophageal samples of Wistar rats (N=5) and were found beneath the basal epithelial layer, in submucosa, closely related to smooth as well as striated muscular fibers, and also in adventitia. They were closely related to mast cells, macrophages, and microvessels. Hybrid morphologies of stromal cells processes were found: cytoplasmic processes continued distally in a telopodial fashion. Telopodes alone may not be enough for a safe diagnostic of TCs in TEM; a larger set of specific standards (such as the telopodial emergence, and the sizes of the cell body and telopodes) should be considered to differentiate TCs to various species of fibroblasts. The morphological and ultrastructural specific features should make the difference between TCs and interstitial cells of Cajal in the digestive tract.
... Caveolae [1] are plasma membrane flask(omega)-shaped invaginations present in many cell types [2][3][4]. These structures are particularly prominent in the interstitial cells of Cajal (ICC), the gut pacemaker cells [5][6][7][8][9], and in the smooth muscle cells (SMC) [10,11], but their role is not fully understood yet. In the early 1970s, caveolae were proposed as sites of excitation-contraction cou-pling in visceral SMC [11][12][13] and currently it is acknowledged the role of caveolae in smooth muscle Ca 2ϩ homeostasis [14] as sites for calcium entry and storage [15,16]. ...
Caveolin (Cav)-1 is an integral membrane protein of caveolae playing a crucial role in various signal transduction pathways. Caveolae represent the sites for calcium entry and storage especially in smooth muscle cells (SMC) and interstitial cells of Cajal (ICC). Cav-1(-/-) mice lack caveolae and show abnormalities in pacing and contractile activity of the small intestine. Presently, we investigated, by transmission electron microscopy (TEM) and immunohistochemistry, whether the absence of Cav-1 in Cav-1(-/-) mouse small intestine affects ICC, SMC and neuronal morphology, the expression of NK1 and NK2 receptors, and of Ano1 (also called Dog1 or TMEM16A), an essential molecule for slow wave activity in gastrointestinal muscles. ICC were also labelled with c-Kit and tachykinergic neurons with Substance P (SP). In Cav-1(-/-) mice: (i) ICC were Ano1-negative but maintained c-Kit expression, (ii) NK1 and NK2 receptor immunoreactivity was more intense and, in the SMC, mainly intracytoplasmatic, (iii) SP-immunoreactivity was significantly reduced. Under TEM: (i) ICC, SMC and telocytes lacked typical caveolae but had few and large flask-shaped vesicles we called large-sized caveolae; (ii) SMC and ICC contained an extraordinary high number of mitochondria, (iii) neurons were unchanged. To maintain intestinal motility, loss of caveolae and reduced calcium availability in Cav-1-knockout mice seem to be balanced by a highly increased number of mitochondria in ICC and SMC. Loss of Ano-1 expression, decrease of SP content and consequently overexpression of NK receptors suggest that all these molecules are Cav-1-associated proteins.
... The presence of cells which fall in the category of irregularly shaped with processes have so far been confirmed in every tissue which contains smooth muscle cells, apart from airway smooth muscle (oesophagus [8,9], stomach [10,11], small intestine [12,13], colon [14,15], ureter [16,17], urinary bladder [18,19,20,21,22], urethra [23,24,25,26,27], arteries [28,29,30,31], veins [32,33,34,35], lymphatic vessels [36], uterus [37,38], Fallopian tubes [39], prostate [40,41], and vas deferens [42]). Cells of similar morphology have also been described in the heart muscle [43], close to cardiomyocytes, in both atria [44,45] and ventricles [46], suggesting their presence throughout the cardiovascular system. ...
Blood vessels are made up of several distinct cell types. Although it was originally thought that the tunica media of blood vessels was composed of a homogeneous population of fully differentiated smooth muscle cells, more recent data suggest the existence of multiple smooth muscle cell subpopulations in the vascular wall. One of the cell types contributing to this heterogeneity is the novel, irregularly shaped, noncontractile cell with thin processes, termed interstitial cell, found in the tunica media of both veins and arteries. While the principal role of interstitial cells in veins seems to be pacemaking, the role of arterial interstitial cells is less clear. This review summarises the knowledge of the functional and structural properties of vascular interstitial cells accumulated so far, offers hypotheses on their physiological role, and proposes directions for future research.
... They might be taken as fibroblast cells which have become differentiated, depending on their relationships with the surrounding cellular microenvironment (Komuro 1990). Although previous authors have concluded that there exist no ICCs in the longitudinal and circular muscle layers of the human colon (Christensen and Rick 1987; Faussone-Pellegrini 1987; Rumessen 1994), the present data show the existence of c-kit ICs in both of these muscle layers as well as in the septa, in line with other previous studies (Hagger et al. 1997; Torihashi et al. 1999). Here we have shown, in addition, that c-kit ICs are frequently inserted between the nerve fibers and the muscle cells, with which they establish membrane appositions . ...
C-kit immunocytochemistry was performed on ultrathin sections of human distal colon. Our attention was focused on relationships between c-kit immunoreactive interstitial cells (c-kit ICs) and muscular cells and nervous elements located in the external muscular layers of the colonic wall. C-kit ICs established membrane apposition with both nerve fibers and smooth muscle cells of, respectively, the longitudinal and circular muscle layers, the myenteric area, and the extremus submucosus plexus. C-kit ICs also surrounded the external submucosus plexus and established membrane appositions with nerve elements located inside the myenteric ganglia. These membrane appositions were observed either at the level of the c-kit IC bodies or at that of their cytoplasmic processes. In some cases, membrane appositions were observed concomitantly between the c-kit ICs, nerve fibers, and smooth muscle cells. In all the regions studied, the c-kit ICs were also found to be located in the close vicinity of blood vessels and to have established close contacts with non-immunoreactive fibroblast-like cells. The results of the present study shed essential light on the relationships of c-kit ICs with the neighboring muscle cells and nerve elements, and confirm that the intercalated c-kit ICs well fit with the so-called "interstitial cells of Cajal".
... We were able to identify two networks of ICC associated with AP and the SMP. This distribution is very similar to those described in other species, including humans (8,23), dogs (1,2), and mice (7). The ICC-SMP network was not present in the preparations devoid of submucosa. ...
Intracellular microelectrodes and organ bath techniques were used to study spontaneous cyclic electrical and mechanical activity in the rat colon. Electron microscopy and immunohistochemical studies showed two major populations of interstitial cells of Cajal (ICC): one associated with Auerbach's plexus (ICC-AP) and one with the submuscular plexus (ICC-SMP). The ICC-SMP network partly adhered to the submucosa when removed and was generally strongly damaged after separation of musculature and submucosa. Similarly, longitudinal muscle removal severely damaged AP. Two electrical and mechanical activity patterns were recorded: pattern A, low-frequency (0.5--1.5 cycles/min), high-amplitude oscillations; and pattern B, high-frequency (13--15 cycles/min), low-amplitude oscillations. Pattern A was recorded in preparations with intact AP but absent in those without intact AP. Pattern B was recorded in preparations with intact SMP but was absent in those lacking SMP. With full-thickness strips, the superimposed patterns A and B were recorded in circular muscle. When longitudinal muscle mechanical activity was recorded, only pattern A was present. We conclude that two pacemakers regulate rat colonic cyclic activity: the ICC-SMP network (responsible for cyclic slow waves and small-amplitude contractions) and the ICC-AP network (which may drive the cyclic depolarizations responsible for high-amplitude contractions). This is the first report showing consistent slow wave activity in the rodent colon.
... Morphological and physiological studies have demonstrated the importance of the tight synaptic connections formed by ICC-IM as mediators of excitatory J Physiol 564.2 and inhibitory enteric motor neurotransmission in the gastric fundus and antrum, and in the lower oesophageal and pyloric sphincters (Burns et al. 1996;Ward et al. 1998Ward et al. , 2000Becket et al. 2002Becket et al. , 2003Suzuki et al. 2003). Similar morphological relationships exist between enteric motor nerve terminals and ICC-IM in the small intestine (termed ICC-DMP) and colon in a variety of species including man (Thuneberg, 1982;Faussone-Pellegrini, 1987;Rumessen et al. 1992Rumessen et al. , 1993Torihashi et al. 1993;Wang et al. 2000Wang et al. , 2003a. Functional immunohistochemical studies of produced an IJP that was followed by phase advancement and an increase in the duration of the slow wave immediately following EFS. ...
Intramuscular interstitial cells of Cajal (ICC-IM) play a critical role in enteric neural regulation of the circular muscle layer in the stomach, but no studies have been performed on the longitudinal layer. Kit immunohistochemistry was used to examine ICC-IM in the longitudinal muscle layer of the murine corpus and antrum, and it revealed marked heterogeneity in the distribution of ICC-IM in longitudinal muscles. In the corpus, ICC-IM were found along the greater curvature near the fundus. ICC-IM decreased in density in the circumferential axis toward the lesser curvature and in the longitudinal axis toward the antrum. ICC-IM were absent from the longitudinal layer of the antrum. Double labelling with markers for specific classes of enteric motor neurones revealed that cholinergic and nitrergic motor neurones formed close contacts with ICC-IM in the corpus but not in the antrum. Enteric nerve stimulation evoked prominent cholinergic excitatory and nitrergic inhibitory responses in longitudinal muscles of the corpus, but not in the antrum of wild-type animals. Cholinergic and nitrergic nerves were also present in W/W(V) mice, but functional innervation of the longitudinal muscle layer by these nerves in the corpus and antrum were absent. The data show that cholinergic and nitrergic neurotransmission only occurs in the gastric longitudinal layer in regions where ICC-IM are present. In regions, such as the corpus, where ICC-IM are common, robust neural responses are present, but the reduced density of ICC-IM near the lesser curvature and in the distal stomach leads to reduced neural regulation in these gastric regions.
... Briefly, ICC can be identified among all other cell types present in an interstitial position between nerve fibres and smooth muscle cells by the following ultrastructural characteristics: bundles of filaments, mainly intermediate filaments, everywhere distributed; several microtubules; an extended smooth endoplasmic reticulum (SER); few ribosomes and a variable number of cisternae of rough endoplasmic reticulum; a large Golgi apparatus; many mitochondria and caveolae; presence of a basal lamina, although discontinuous [8,16,24]. Nevertheless, ICC at various locations within the gastrointestinal tract and in different species have their own set of EM criteria for their identification [7,[24][25][26]. Thuneberg [5] and Komuro [27] have always pointed out and Rumessen and Vanderwinden [16] recently stated that "most ICC, defined by transmission electron microscopy, will belong in a spectrum ranging from cell types very similar to smooth muscle cells ("myoid cells") to cell types on the other end of the spectrum with ultrastructural features hardly distinguishable from classic description of fibroblasts ("fibroblast-like" or "fibroid" cells")". ...
Santiago Ramon y Cajal observed a special cell type that appeared to function as endstructures of the intrinsic nervous system in several organs. These cells were structurally and functionally further characterized in the gut musculature and named interstitial cells of Cajal (ICC). In recent years, interstitial cells have been identified in the vasculature, urinary tract, glands and other organs. Their morphologies and functions are just beginning to be clarified. It is likely that amongst them, subtypes will be discovered that warrant the classification of interstitial cells of Cajal. This "point of view" continues the discussion on the criteria that should be used to identify ICC outside the musculature of the gut.
... These highly branched cells occur in networks associated with the muscular plexuses of the enteric nervous system. Both in humans and laboratory mammals, ICC have a characteristic intramural distribution specific to the different regions of the gut and species-variations in structure and staining have also been reported [1][2][3][4][5][6][7][8][9][10][11][12]. Consequently, several ICC sub-types have been identified. ...
The so-called interstitial cells of Cajal (ICC) are distributed throughout the muscle coat of the alimentary tract with characteristic intramural location and species-variations in structure and staining. Several ICC sub-types have been identified: ICC-DMP, ICC-MP, ICC-IM, ICC-SM. Gut motility is regulated by ICC and each sub-type is responsible for the electrical activities typical of each gut region and/or muscle layer. The interstitial position of the ICC between nerve endings and smooth muscle cells has been extensively considered. Some of these nerve endings contain tachykinins. Three distinct tachykinin receptors (NK1r, NK2r and NK3r) have been demonstrated by molecular biology. Each of them binds with different affinities to a series of tachykinins (SP, NKA and NKB). In the ileum, SP-immunoreactive (SP-IR) nerve fibers form a rich plexus at the deep muscular plexus (DMP), distributed around SP-negative cells, and ICC-DMP intensely express the SP-preferred receptor NK1r; conversely a faint NK1r-IR is detected on the ICC-MP and mainly after receptor internalization was induced by agonists. ICC-IM are never stained in laboratory mammals, while those of the human antrum are NK1r- IR. RT-PCR conducted on isolated ileal ICC-MP and gastric ICC-IM showed that these cells express NK1r and NK3r. Colonic ICC, except those in humans, do not express NK1r-IR, at least in resting conditions. Outside the gut, NK1r-IR cells were seen in the arterial wall and exocrine pancreas. In the mouse gut only, NK1r-IR is present in non-neuronal cells located within the intestinal villi, so-called myoid cells, which are c-kit-negative and alpha-smooth muscle actin-positive. Immunohistochemistry and functional studies confirmed that ICC receive input from SP-IR terminals, with differences between ICC sub-types. In the rat, very early after birth, NK1r is expressed by the ICC-DMP and SP by the related nerve varicosities. Studies on pathological conditions are few and those on mutant strains practically absent. It has only been reported that in the inflamed ileum of rats the NK1r-IR ICC-DMP disappear and that at the peak of inflammatory conditions ICC-MP are NK1r-IR. In the ileum of mice with a mutation in the W locus, ICC-DMP were seen to express c-kit-IR but not NK1-IR, and SP-IR innervation seems unchanged. In summary, there are distinct ICC populations, each of them under a different tachykininergic control and, likely, having different functions. Further studies are recommended at the aim of understanding ICC involvement in modulating/transmitting tachykininergic inputs.
Minute-to-minute behavior of the alimentary tract reflects the integrated functioning of the gut's musculature, secretory glands and blood–lymphatic vasculature. Activity of the three effector systems to generate functionally effective patterns of behavior, which are adaptive for differing digestive states, is organized and coordinated by the enteric nervous system (i.e., the brain-in-the-gut). The heuristic model for the enteric nervous system (ENS) is the same as for all integrative nervous systems, whether in vertebrate or invertebrate animals. Like other integrative nervous systems, such as the spinal cord and brain stem, the ENS functions with sensory neurons, interneurons and motor neurons. That the gut does not work without the ENS can be made as an absolute statement. This is apparent in its absence in terminal regions of the large intestine in Hirschsprung's disease in humans and animals where it is reflected by dysfunctional motility, failure of defecation and proximal fecal compaction ...
The suburothelium has received renewed interest because of its role in sensing bladder fullness. Various studies evaluated suburothelial myofibroblasts (MFs), interstitial cells (ICs), interstitial Cajal cells (ICCs) or telocytes (TCs), which resulted in inconsistencies in terminology and difficulties in understanding the suburothelial structure. In order to elucidate these issues, the use of electron microscopy seems to be an ideal choice. It was hypothesized that the cell population of the suburothelial band is heterogeneous in an attempt to clarify the above-mentioned inconsistencies. The suburothelial ICs of the bladder were evaluated by immunohistochemistry (IHC) and transmission electron microscopy (TEM). Bladder samples from 6 Wistar rats were used for IHC and TEM studies and human bladder autopsy samples were used for IHC. Desmin labeled only the detrusor muscle, while all the myoid structures of the bladder wall were positive for α-smooth muscle actin (SMA). A distinctive α-SMA-positive suburothelial layer was identified. A layered structure of the immediate suburothelial band was detected using TEM: (1) the inner suburothelial layer consisted of fibroblasts equipped for matrix synthesis; (2) the middle suburothelial layer consisted of smooth muscle cells (SMCs) and myoid ICCs, and (3) the outer suburothelial layer consisted of ICs with TC morphology, building a distinctive network. In conclusion, the suburothelial layer consists of distinctive types of ICs but not MFs. The myoid layer, with SMCs and ICCs, which could be considered identical to the α-SMA-positive cells in the suburothelial band, seems the best-equipped layer for pacemaking and signaling. Noteworthy, the network of ICs also seems suitable for stromal signaling. © 2014 S. Karger AG, Basel.
Currently, much information is provided regarding the presence and the roles in tissue regeneration of stem cell niches residing in post-natal dental pulp. So far, three types of adult stem cells have been isolated from dental pulp. Correct evaluation of these cells is important in order to determine their potential use in clinical fields. The present study aims to review the origins and immunophenotype of these cells. The particularities of interstitial cells of the stem cell niches are also debated.
This review examines recent evidence from structural and functional studies that interstitial cells of Cajal (ICC) play a major role in control of gastrointestinal function. These cells, identified to date only by their structural and somewhat selective staining characteristics, form networks in the region of the myentehc plexus and in or adjacent to circular muscle. Those in circular muscle are often coupled to one another and to smooth muscle cells by gap junctions and are closely innervated by a high proportion of enteric nerves, especially those containing vasoactive intestinal polypeptide (VIP). ICC in the myenteric plexus often have no visible connections by gap junctions to smooth muscle. There is a growing body of evidence from study of small intestine and colon that these cells are either the pacemakers or provide clocks for the pacemaking function of the gut (vahously known as slow waves, pacesetter potentials or control potentials). Additional evidence suggests that they may play a role in neurotransmission of non-adrenergic, non-cholinergic inhibitory activity. This review summarizes our current understanding and attempts to point the way for future research.
This chapter provides an overview of the functions of nitric oxide (NO) in the gastrointestinal tract (GIT) in adult and developing animals and humans. NO is produced by nitric oxide synthase (NOS) and by nonenzymatic pathways. In the gastrointestinal tract (GIT) of adults, the majority of NO-producing neurons are localized in the myenteric plexus where they act as inhibitory inter and motoneurons. NO plays a role as a neurotransmitter in the enteric nervous system (ENS). NO is involved in non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmission in the GIT. The nitrergic innervation is important for the growth, maturation, and proper function of the GIT as the inhibition of cNOS causes severe impairment of gastrointestinal function. The occurrence of NOS-positive cells in a variety of organs (CNS, respiratory system, and GIT) is higher at the prenatal stage of development than at other times suggesting that NO is also important for the development of these organs in addition to its importance for foetal and postnatal development of the mammalian GIT. The distribution of nitrergic neurons in the GIT in fetuses, growing and adult animals, and humans is discussed. The chapter reviews interstitial cells of Cajal (ICC) that refer to the connection of ICC with nitrergic neurons, the involvement of ICC in NO production, and neurotransmission involving nitrergic neurons. The actions of NO and the distribution of nitrergic neurons in the GIT of growing animals is presented, and some other aspects of the role of NO in the development of the GIT are discussed.
Kit is a marker for interstitial cells of Cajal (ICC). ICCs interact with enteric neurons and are essential for gastrointestinal motility. The roles of neural crest-derived cells, neurons, Kit, and Kit ligand (KL) in ICC development were analyzed. ICC development lagged behind that of neurons and smooth muscle. Although mRNA encoding Kit and KL was detected at E11, Kit-immunoreactive ICCs did not appear until E12 in foregut and E14 in terminal hindgut. Transcripts of Kit and KL and Kit-immunoreactive cells were found in aganglionic gut from ls/ls and c-ret −/− mice. ICCs also developed in crest-free cultures of ls/ls terminal colon. ICCs appeared in cultures of noncrest- but not those of crest-derived cells isolated from the fetal bowel by immunoselection with antibodies to p75NTR. KL immunoreactivity was coincident in cells with neuronal or smooth muscle markers. The development of ICCs in cultures of mixed cells dissociated from the fetal gut was dependent on plating density. No ICCs appeared at ≤80,000 cells/ml, but many cells, including filamentous ICCs, appeared at ≥200,000 cells/ml. Exogenous KL partially substituted for a high plating density. These data support the ideas that mammalian ICCs are neither derived from the neural crest nor developmentally dependent on neurons. ICC differentiation/survival requires KL, which can be provided by neurons or cells in a smooth muscle lineage. Neurons may be needed for development of myenteric ICCs and the mature ICC network. J. Neurosci. Res. 59:384–401, 2000 © 2000 Wiley-Liss, Inc.
The role of interstitial cells of Cajal (ICC) is difficult to determine because these cells are not easily identified by light microscopy, and there are no compounds available to specifically lesion ICC. Ultrastructural studies have shown an abundance of mitochondria in ICC. Therefore, we have used rhodamine 123, a fluorescent dye that is specifically accumulated by mitochondria, to identify ICC in canine proximal colon. This technique provided good discrimination between ICC and smooth muscle cells, but enteric neurons were labeled with rhodamine 123. This compound has cytotoxic properties in some cells. Therefore, we treated intact muscle strips with rhodamine 123 while recording intracellular electrical activity from circular muscle cells. Uptake of rhodamine 123 by ICC was associated with an alteration in electrical rhythmicity. These data suggest that rhodamine 123 may be a useful tool for visualizing and perhaps chemically lesioning ICC.
An extensive cellular network becomes visible over the myenteric plexus of the rat after removal of the overlying tissues under the scanning electron microscope. The cells are mainly stellate and have many slender processes via which they interconnect. They form a three-dimensional network and are closely associated with the ganglia and nerve bundles, and also extend over the smooth muscle cells. They are considered to correspond to the interstitial cells of Cajal because of their peculiar arrangement and their topography. Transmission electron-microscopic evidence demonstrates that the majority of those cells have features of fibroblasts. Gap junctions and intermediate junctions are observed between these fibroblast-like cells, and also between them and smooth muscle cells. Examination of serial thin sections reveals that single fibroblast-like interstitial cells connect to both circular and longitudinal muscle cells via gap junctions. It is suggested that the network of interstitial cells conducts electrical signals.
The ultrastructure of the wild-type (+/+) mice small intestine was compared with c-kit mutant (W/Wν) mice which only have few interstitial cells of Cajal (ICC) associated with Auerbach’s plexus, in order to elucidate whether the specialized membrane contacts are general features of so-called fibroblast-like cells that are widely distributed in the tunica muscularis of the alimentary tract. Fibroblast-like cells in the Auerbach region were found in approximately equal number in W/Wν mice as in +/+ mice, while ICC associated with Auerbach’s plexus (ICC-AP) could not be demonstrated in W/Wν mice in the present investigation. Fibroblast-like cells were characterized by cytoplasm of moderate to high electron density, well developed rough endoplasmic reticulum and nuclei with thick peripheral accumulations of heterochromatin. There were no basal lamina and caveolae along the cell membrane. It was observed that single fibroblast-like cells formed probable small gap junctions with muscle cells of both circular and longitudinal layers. Fibroblast-like cells with the same features were also observed in the region of the deep muscular plexus in both +/+ and W/Wν mice. The present observation, together with our previous studies on rats and guinea-pigs, suggest the common presence of gap junctions or gap junction-like structures on fibroblast-like cells in the gastrointestinal musculature and their involvement in the regulatory system of gastrointestinal motility by passing electrical or molecular signals to influence the state of muscle tonus.
This study was carried out to compare the density of the interstitial cells of Cajal (ICCs) in the bowel wall of children with Hirschsprung's disease (HD), anorectal malformations (ARM) and normal controls in Trinidad and Tobago.
Segments of bowel wall excised from eight children with HD, three controls and two children with ARM were immunostained with c-Kit primary antibody. Cells with features of ICCs were counted.
All three controls and the two children with ARM had dense distribution of ICCs. Most children (6/8; 75%) with HD had markedly reduced counts in aganglionic bowel. Two (25%) also had a decrease in ganglionic bowel. Possible influences were patient age and gender and the level of bowel sectioned.
Analysis of this sample suggests that immunostaining for c-Kit positive cells might be a useful screening test in the assessment of bowel motility disorders. The possible effects of age, gender and the level of bowel sampled await determination.
The aim of this ultrastructural study was to examine the human detrusor for interstitial cells of Cajal (ICC)-like cells (ICC-L) by conventional transmission electron microscopy (TEM) and immuno-transmission electron microscopy (I-TEM) with antibodies directed towards CD117 and CD34. Two main types of interstitial cells were identified by TEM: ICC-L and fibroblast-like cells (FLC). ICC-L were bipolar with slender (0.04 microm) flattened dendritic-like processes, frequently forming a branching labyrinth network. Caveolae and short membrane-associated dense bands were present. Mitochondria, rough endoplasmic reticulum and Golgi apparatus were observed in the cell somata and cytoplasmic processes. Intermediate filaments were abundant but no thick filaments were found. ICC-L were interconnected by close appositions, gap junctions and peg-and-socket junctions (PSJ) but no specialised contacts to smooth muscle or nerves were apparent. FLC were characterised by abundant rough endoplasmic reticulum but no caveolae or membrane-associated dense bands were observed; gap junctions and PSJ were absent and intermediate filaments were rare. By I-TEM, CD34 gold immunolabelling was present in long cytoplasmic processes corresponding to ICC-L between muscle fascicles but CD117 gold immunolabelling was negative. Thus, ICC-like cells are present in the human detrusor. They are CD34-immunoreactive and have a myoid ultrastructure clearly distinguishable from fibroblast-like cells. ICC-L may be analogous to interstitial cells of Cajal in the gut.
Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine were studied by electron microscopy, and three-dimensional cell models were reconstructed from serial ultrathin sections with a computer graphic system. Three types of cells were recognized. The first type was similar in shape to smooth muscle cells, but did not contain an organized contractile apparatus. Many large gap junctions comprising about 4% of the cell surface were present; they connected cells of the first type to each other, to the second type of cell and to smooth muscle cells of the outer circular layer. The second type of cell had a well-demarcated cell body with long slender processes and was characterized by a large amount of glycogen comprising about 9% of the cell volume. The third type of cell was similar to fibroblasts, and contained well-developed Golgi apparatus and rough endoplasmic reticulum. Some of these fibroblast-like cells (a possible subtype) formed small gap junctions. All three types of cells showed close relationships with nerve varicosities. This cellular network consisting of gap-junction-rich cells, glycogen-rich cells and smooth muscle cells may be involved in the pacemaking activity of intestinal movement.
These studies test the hypothesis that the generation of colonic slow waves can be modulated by stimulation of intrinsic enteric nerves and attempt to identify a neurotransmitter that may be responsible for this change in slow-wave activity. Isolated segments from the mid-colon of the cat generated regular, continuous slow waves at 6.5 +/- 1.1 cpm. Activation of the intrinsic nerves by electrical field stimulation transiently reduced the rate of slow-wave generation to 4.7 +/- 0.7 cpm (P less than 0.001). The response to electrical stimulation was blocked by tetrodotoxin and alpha-chymotrypsin. The following antagonists were not effective in blocking the response: atropine, hexamethonium, phenoxybenzamine, propranolol, methysergide, naloxone, or imidazole. Vasoactive intestinal polypeptide (5 x 10(-7) M) decreased slow wave frequency to 4.5 +/- 0.4 cpm. Vasoactive intestinal polypeptide (VIP) fragment 10-28 inhibited the effect of electrical field stimulation but also decreased the slow-wave frequency. VIP-immunoreactive nerves were much more abundant in the plexus submucosus extremus than in the circular muscle of the muscularis externa. Thus, pacemakers for colonic slow waves may be modulated by intrinsic colonic nerves, and vasoactive intestinal polypeptide may be the neurotransmitter responsible for this modulation.
Slow oscillations of the membrane potential difference of circular smooth muscle cells of the colon, slow waves, arise at the interface between the submucosa and muscularis externa of the colon. These studies test the hypothesis that the generation of slow waves in the circular muscle layer of the colon of the cat is dependent upon an intact interface between the submucosa and muscularis externa. Electrical recordings were made from 3 types of tissue preparations from the proximal colon: (a) submucosa and muscularis externa intact, (b) submucosa isolated from the circular muscle, and (c) muscularis externa isolated from the submucosa. The cellular make-up of each tissue was determined by the osmic acid-zinc iodide method (Champy-Maillet), and the Masson's trichrome stain. Continuous slow waves were recorded from intact tissues. Removal of the submucosa abolished slow waves from the underlying muscularis externa. Either irregular electrical transients or waxing and waning slow wave-like activity were recorded from the isolated submucosa. Submucosal tissues removed from the muscularis externa contained no circular smooth muscle, but did contain elements of the plexus submucosus extremus.
There is experimental evidence suggesting that the interstitial cells of Cajal are essential for rhythmic slow waves of the smooth muscle layers of the mammalian small intestine. Different investigators have identified them variously as modified neurons, glia, fibroblasts or modified smooth muscle cells. Since histological categorization bears on understanding their function, we have examined the immunoreactivity of the myenteric plexus of the rat small intestine, paying special attention to the cell type identified as Thuneberg's Type I-ICC. Polyclonal and monoclonal antisera directed against 4 intermediate filament proteins: neurofilament protein, glial fibrillary acidic protein, vimentin and desmin were used. In addition, antisera directed against neuron-specific enolase, substance P and vasoactive intestinal polypeptide were also tested for reactivity. Type I-ICCs were immunonegative to all the antisera directed against intermediate filament proteins and neuropeptides. However, some Type I-ICCs were immunopositive to antisera against neuron-specific enolase. On the basis of these results and the distribution of immunoreactivities to these kinds of antisera in other tissues, we suggest that Type I-ICCs are distinct from typical myenteric neurons, from glia, from fibroblasts and from smooth muscle fibers. Staining with antiserum against neuron-specific enolase suggests a relation to some type of neuron.
This study has demonstrated that cells stained using the zinc iodide-osmic acid (ZIO) method have the same fine structural features as those of fibroblasts. They have a well developed Golgi apparatus, granular endoplasmic reticulum and many mitochondria. They have no basal lamina. They are distributed in association with the deep muscular plexus, within the outer circular muscle layer and in the space between the circular and longitudinal muscle layers. Since this staining method is believed to co-stain nerves and interstitial cells of Cajal, we concluded that these ZIO-positive, fibroblast-like cells represent at least some, if not all, of the interstitial cells which appeared in the original description by Cajal.
This study was performed to assess the repetitive phasic mechanical and (or) electrical activity of the muscle from different regions of the human gastroesophageal junction (GEJ). Muscle strips from the circular and longitudinal layers of the gastric fundus and esophagus and of the clasp and sling components of the GEJ were obtained from surgical specimens and prepared for in vitro recording of contractile or electrical activity. Phasic contractions occurred in all regions except the longitudinal muscle of the gastric fundus and that overlying the sling. Robust phasic activity (2.6 +/- 0.6 min-1) was most frequent (92% of specimens) in longitudinal muscle overlying the clasp, arising spontaneously in 67%. Stretch or carbachol stimulation increased the frequency of these contractions. Transmural electrical stimulation produced a transient cessation of phasic activity. Electrical recording showed slow waves with superimposed spiking coinciding with phasic contractions. These activities were unaltered by 1 microM atropine or 1 microM tetrodotoxin, but inhibited by 2 microM verapamil. In conclusion, several muscles of the human esophagus and GEJ manifest repetitive contractions in vitro, particularly the longitudinal muscle overlying the clasp muscle fibers. These oscillations are due to electrical slow waves, can potentially be modulated by intrinsic nerves, and may play a role in the intermittent phasic contractions of lower esophageal sphincter pressure in vivo.
The ultrastructure of canine distal esophagus was studied focusing on interstitial cells of Cajal (ICC) and their relationships to nerves and muscle. The distal esophagus consisted of two muscle layers composed of intertwining skeletal and smooth muscle bundles. The ICC formed an interconnecting network and were an integral part of these structures. The ICC communicated with one another and with adjacent smooth muscle cells through numerous gap junctions. The morphology of individual ICC resembled that observed in other gut regions. All interstitial cells were densely innervated. The highest density of ICC, just proximal to the lower esophageal sphincter, coincided with the previously reported highest incidence of occurrence of electrical slow wave type action potentials. Examination of a large number of structural associations of ICC led us to conclude that in the distal esophagus, two networks of ICC and nerves exist, one associated with the inner muscle layer, another associated with the outer muscle layer. These networks are not sheet-like structures, such as the network of ICC in the myenteric plexus or deep muscular plexus of the small intestine, but are three dimensional and are interspersed throughout both muscle layers. The networks do not extend into Auerbach's plexus. The main branches of the networks run along the long axis of the esophagus and seem ideally suited to facilitate communication in this direction. These observations suggest that esophageal interstitial cells are structurally organized in such a manner that they may play a role in pacemaking and neural control of esophageal motility.
The ultrastructure and immunocytochemistry of interstitial cells (ICs) in the canine proximal colon were investigated. Three types of ICs were found within the tunica muscularis. (1) ICs were located along the submucosal surface of the circular muscle (IC-SM). These cells shared many features of smooth muscle cells, including myosin thick filaments and immunoreactivity to smooth muscle gamma actin, myosin light chain, and calponin antibodies. IC-SM were clearly different from smooth muscle cells in that contractile filaments were less abundant and intermediate filaments consisted of vimentin instead of desmin. (2) ICs in the region of the myenteric plexus (IC-MY) were similar to IC-SM, but these cells had no thick filaments or immunoreactivity to smooth muscle gamma actin or calponin antibodies. (3) The fine structures and immunoreactivity of ICs within the muscle layers (IC-BU) were similar to IC-MY, but IC-BU lacked a definite basal lamina and membrane caveolae. IC-BU and IC-MY were both immunopositive for vimentin. Since all ICs were immunopositive for vimentin, vimentin antibodies may be a useful tool for distinguishing between ICs and smooth muscle cells. Each class of ICs was closely associated with nerve fibers, made specialized contacts with smooth muscle cells, and formed multicellular networks. A combination of ultrastructural and immunocytochemical techniques helps the identification and classification of ICs by revealing the fine structures and determining the "chemical coding" of each class of ICs.
The location of neuronal nitric oxide synthase-immunoreactivity (NOS-IR) in whole mount preparations of muscularis externa of rat ileum was determined by using pre-embedding electron microscope immunocytochemistry. Several neurons, nerve fibers and nerve endings in the myenteric plexus (MP) and nerve endings within the muscle layers were found to be NOS-IR. These nerve endings were especially numerous in the deep muscular plexus (DMP) and much closer to interstitial cells of Cajal (ICC) than to smooth muscle cells. Some of the ICC-MP were NOS-IR. These findings indicate that ICC-MP are apparently able to produce NO and ICC-DMP are the ileal ICC type very richly innervated by the NO releasing nerves.
The substance P (SP)-containing nerves at the deep (DMP) and myenteric (MP) plexuses and the related interstitial cells of Cajal (ICC-DMP and ICC-MP) were immunohistochemically studied in rat and guinea-pig ileum. All the ICC expressed SP-preferred receptor NK1r: the ICC-DMP showed an intense and the ICC-MP a faint NK1r-immunoreactivity(IR). c-kit-labeling confirmed that they were ICC. The SP-IR nerves at the DMP were significantly more numerous in the guinea-pig than in the rat, and more numerous than those at the MP in both animal species. All the ICC-DMP in the guinea-pig and half of them in the rat were close to SP-IR nerves. The ICC-MP were rarely near to SP-IR nerves in either species. The SP-innervation shows interspecies differences at the DMP that imply a different tachykinergic control of the local ICC.
This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.
The shape, distribution, and ultrastructural features of interstitial cells of Cajal (ICC) of different tissue layers and organs of the rat and guinea-pig digestive tract were described and compared with the corresponding cells in other species including mice, dogs, and humans, as reported in the literature. By light microscopy, the best marker for ICC appeared to be immunoreactivity for c-Kit. Ultrastructurally, ICC were characterized by the presence of many mitochondria, bundles of intermediate filaments, and gap junctions, which linked ICC with each other. However, ICC were morphologically heterogeneous and had particular features, depending on their tissue and organ location and species. ICC in the deep muscular plexus of the small intestine and in the submuscular plexus of the colon were the most like smooth muscle cells, and had a distinct basal lamina and numerous caveolae. In contrast, ICC of Auerbach's plexus at all levels of the gastrointestinal tract were the least like smooth muscle cells. They most closely resembled unremarkable fibroblasts. ICC within the circular muscle layer were intermediate in form. In addition to the tissue specificity, some organ and species specificity could be distinguished. The structural differences between ICC may be determined by their microenvironment, including the effects of mechanical force, type of nerve supply, and spacial relationship with smooth muscle cells.
The interstitial cell of Cajal, abbreviated ICC, is a specific cell type with a characteristic distribution in the smooth muscle wall throughout the alimentary tract in humans and laboratory mammals. The number of publications relating to ICC is rapidly increasing and demonstrate a rich variation in the structure and organization of these cells. This variation is species-, region-, and location-dependent. We have chosen to define a "reference ICC," basically the ICC in the murine small intestine, as a platform for discussion of variability. The growing field of ICC markers for light and electron microscopy is reviewed. Although there is a rapidly increasing number of approaches applicable to bright field and fluorescence microscopy, the location of markers by electron microscopy still suffers from inadequate preservation of ultrastructural detail. Finally, we summarize evidence related to ICC ultrastructure under conditions differing from those of the normal, adult individual (during differentiation, in pathological conditions, transplants, mutants, and in cell culture).
This review is a portrayal of the evolution of ideas involving the interstitial cells of Cajal in changing disguises as dull fibroblasts, not very exciting Schwann cells, or perhaps quite important, though primitive neurons. However, today unmasked (we believe), they reveal themselves as myoid cells, a role that, judging by current interest, is far more exciting than former ones. Close to 500 publications from 1860-1999 have contributed to the discussion in one way or the other. This literature contains a wealth of correct observations but obviously also wrong interpretations, which are seen as a result of too blind a belief in specificities of visualization methods, combined with a desire to interpret even the hidden detail. It has been my objective to attempt to trace the origins of viable ideas, and I have therefore focused on relatively few authors. The most recent development from 1980 until today is so well covered by easily accessible reviews that I have resorted to a mere, but hopefully complete, list of them. Modern ICC'ists have so far been caught in the external muscle of the gut and kept their hands off its internal affairs. However, while working my way through the literature it struck me that a number of recent studies may provide the elements of a plausible model for the villous contraction mechanism. In the present context, an important point is that the very first published interstitial "neurons" from Cajal's hand-of the intestinal villus, 1889-may achieve new significance as a possible correlate to the regulatory ICC of the intestinal muscularis. Partly to make this point, I have taken the liberty of giving a short account of recent results from our lab.
Kit is a marker for interstitial cells of Cajal (ICC). ICCs interact with enteric neurons and are essential for gastrointestinal motility. The roles of neural crest-derived cells, neurons, Kit, and Kit ligand (KL) in ICC development were analyzed. ICC development lagged behind that of neurons and smooth muscle. Although mRNA encoding Kit and KL was detected at E11, Kit-immunoreactive ICCs did not appear until E12 in foregut and E14 in terminal hindgut. Transcripts of Kit and KL and Kit-immunoreactive cells were found in aganglionic gut from ls/ls and c-ret -/- mice. ICCs also developed in crest-free cultures of ls/ls terminal colon. ICCs appeared in cultures of noncrest- but not those of crest-derived cells isolated from the fetal bowel by immunoselection with antibodies to p75(NTR). KL immunoreactivity was coincident in cells with neuronal or smooth muscle markers. The development of ICCs in cultures of mixed cells dissociated from the fetal gut was dependent on plating density. No ICCs appeared at </=80,000 cells/ml, but many cells, including filamentous ICCs, appeared at >/=200,000 cells/ml. Exogenous KL partially substituted for a high plating density. These data support the ideas that mammalian ICCs are neither derived from the neural crest nor developmentally dependent on neurons. ICC differentiation/survival requires KL, which can be provided by neurons or cells in a smooth muscle lineage. Neurons may be needed for development of myenteric ICCs and the mature ICC network.
In spite of a claim by KOBAYASHI (1990) that they do not correspond to the cells originally depicted by CAJAL, a particular category of fibroblast-like cells have been identified in the gut by electron microscopy (FAUSSONE-PELLEGRINI, 1977;THUNEBERG, 1980) and by immunohistochemistry for Kit protein (MAEDA et al., 1992) under the term of the “interstitial cells of Cajal (ICC)”. Generating electrical slow waves, the ICC are intercalated between the intramural neurons and the effector smooth muscular cells, to form a gastroenteric pacemaker system.
ICC at the level of the myenteric plexus (IC-MY) are multipolar cells forming a reticular network. The network of IC-MY which is believed to be the origin of electrical slow waves is morphologically independent from but associated with the myenteric plexus. On the other hand, intramuscular ICC (IC-IM) usually have spindle-shaped contours arranged in parallel with the bulk smooth muscle cells. Associated with nerve bundles and blood vessels, the IC-IM possess receptors for neurotransmitters and such circulating hormones as cholecystokinin, suggesting their roles in neuro-muscular and hormone-muscular transmissions. In addition, gap junctions connect the IC-MY and IC-IM, thereby realizing the electrically synchronized integrity of ICC as a pacemaker system in the gut. The smooth muscle cells are also coupled with ICC via gap junctions, and the functional unit thus formed enables rhythmically synchronized contractions and relaxations.
It has recently been found that a lack of Kit-expressing cells may induce hyper-contractility of the tunica muscularis in vivo, whereas a decrease in Kit expression within the muscle wall causes dysmotility-like symptoms in vivo. The pacemaker system in the gut thus seems to play a critical role in the maintenance of both moderate and normal motility of the digestive tract. A loss of Kit positive cells has been detected in several diseases with an impaired motor activity, including diabetic gastroenteropathy. Pathogenesis of these diseases is thought to be accounted for by impaired slow waves and neuromuscular transmissions; a pacemaker disorder may possibly induce a dysmotility-like symptom called ‘gastroenteric arrhythmia’.
A knowledge of the structure and function of the ICC and the pacemaker system provides a basis for clarifying the normal mechanism and the pathophysiology of motility in the digestive tract.
Vagal intramuscular arrays are mechanoreceptors that innervate smooth muscle fibers and intramuscular interstitial cells of Cajal of the proximal GI tract. C-Kit mutant mice that lack intramuscular interstitial cells of Cajal also lack intramuscular arrays. Mice mutant for steel factor, the ligand for the c-Kit receptor, were studied to extend and validate these previous findings and to characterize associated changes in food intake. Injections of wheat germ agglutinin-horseradish peroxidase and of dextran into the nodose ganglion were employed to label intramuscular arrays and intraganglionic laminar endings, the other vagal mechanoreceptors found in the gut wall. These two receptor types were inventoried in wholemounts of the stomach and duodenum using a standardized sampling and quantification regime. Steel mutants exhibited a paucity of normal intramuscular arrays and lacked intramuscular interstitial cells of Cajal in the forestomach, whereas their intraganglionic laminar endings appeared normal in number, distribution, and morphology. These observations suggest that intramuscular array losses in steel and c-Kit mutants are specific and result from the elimination of the intramuscular interstitial cells of Cajal, the effect common to both mutations, not from interactions peculiar to background strains or non-specific effects. Double-labeling analyses of intramuscular arrays and intramuscular interstitial cells of Cajal reinforced the hypothesis based on previous findings in the c-Kit mice that these interstitial cells have a trophic effect on intramuscular array development and/or maintenance. Finally, meal pattern analyses revealed decreased meal size and increased meal frequency in steel mutants, with normal daily intake. These alterations suggest short-term feeding controls are affected by the loss of intramuscular arrays and/or intramuscular interstitial cells of Cajal, though long-term controls are unimpaired.
Expression of the receptor tyrosine kinase KIT on cells referred to as interstitial cells of Cajal (ICC) has been instrumental during the past decade in the tremendous interest in cells in the interstitium of the smooth muscle layers of the digestive tract. ICC generate the pacemaker component (electrical slow waves of depolarization) of the smooth musculature and are involved in neurotransmission. By integration of ICC functions, substantial progress has been made in our understanding of the neuromuscular control of gastrointestinal motility, opening novel therapeutic perspectives. In this article, the ultrastructure and light microscopic morphology, as well as the functions and the development of ICC and of neighboring fibroblast-like cells (FLC), are critically reviewed. Directions for future research are considered and a unifying concept of mesenchymal cells, either KIT positive (the "ICC") or KIT negative "non-Cajal" (including the FLC and possibly also other cell types) cell types in the interstitium of the smooth musculature of the gastrointestinal tract, is proposed. Furthermore, evidence is accumulating to suggest that, as postulated by Santiago Ramon y Cajal, the concept of interstitial cells is not likely to be restricted to the gastrointestinal musculature.
At least two populations of c-kit positive interstitial cells of Cajal (ICC) lie in the gastric wall, one located at the myenteric plexus level has a pace-making function and the other located intramuscularly is intermediary in the neurotransmission and regenerates the slow waves. Both of these ICC sub-types express full-length dystrophin. Mdx mice, an animal model lacking in full-length dystrophin and used to study Duchenne muscular dystrophy (DMD), show gastric dismotilities. The aim of the present study was to verify in mdx mice whether: (i) gastric ICC undergo morphological changes, through immunohistochemical and ultrastructural analyses; and (ii) there are alterations in the electrical activity, using intracellular recording technique. In control mice, ICC sub-types showed heterogeneous ultrastructural features, either intramuscularly or at the myenteric plexus level. In mdx mice, all of the ICC sub-types underwent important changes: coated vesicles were significantly more numerous and caveolae significantly fewer than in control; moreover, cytoskeleton and smooth endoplasmic reticulum were reduced and mitochondria enlarged. c-Kit-positivity and integrity of the ICC networks were maintained. In the circular muscle of normal mice slow waves, which consisted of initial and secondary components, occurred with a regular frequency. In mdx mice, slow waves occurred in a highly dysrhythmic fashion and they lacked a secondary component. We conclude that the lack of the full-length dystrophin is associated with ultrastructural modifications of gastric ICC, most of which can be interpreted as signs of new membrane formation and altered Ca(2+) handling, and with defective generation and regeneration of slow wave activity.
Interstitial cells of Cajal (ICC) are distributed throughout the gastrointestinal muscle coat with a region-specific location, and are considered to be pace-maker and/or mediators of neurotransmission. Little is known about their shape, size, distribution and relationships with excitatory and inhibitory nerves in human stomach. With this aim, we labeled the ICC, using c-Kit immunohistochemistry, followed by a quantitative analysis to evaluate the distribution and area occupied by these cells in the circular and longitudinal muscle layers and at the myenteric plexus level in the human fundus, corpus and antrum. Furthermore, by NADPH-d histochemistry and substance P (SP) immunohistochemistry, we labeled and quantified nitric oxide (NO)-producing and SP-containing nerves and evidenced their relationships with the ICC in these three gastric regions. In the fundus, the ICC appeared as bipolar cells and in the corpus and antrum they mainly appeared as multipolar cells, with highly ramified processes. The networks formed by ICC differed in the three gastric regions. The ICC number was significantly higher and cell area smaller in the fundus compared to the corpus and antrum. The area occupied by the ICC was significantly higher at the myenteric plexus level compared with circular and longitudinal muscle layers. Everywhere, NADPH-d-positive nerves were more numerous than SP-positive ones. Both kinds of fibers were closely apposed to the ICC in the corpus and antrum. In conclusion, in the human stomach, the ICC have region-specific shape, size and distribution and in the corpus and antrum have close contact with both inhibitory and excitatory nerves. Presumably, as suggested for laboratory mammals, these differences are in relationship with the motor activities peculiar to each gastric area.
Cajal in 1889 described a network of anastomosing interstitial cells in the gut muscle coat and hypothesized that they were accessory primitive neurons exerting a direct regulatory effect on smooth muscle contraction. Reticularists (among them Golgi) sustained that this net was not an assembly of individual cells but a true syncytium and the foremost dissidents, such as Kolliker and Dogiel, declared they were connective tissue cells. Keith, the discoverer of the sino-atrial node, suggested that these cells "constitute a pacemaker system of the intestinal muscle". In the period 1925-1960, there were papers still discussing the role and nature of the interstitial cells. The majority of these papers, however, reflect the fight between neuronists and reticularists. Around 1960, the reality of the neurons was established by ultrastructural evidence and interstitial cells degraded to fibroblasts or Schwann cells. By 1970, electron microscopists began to pay attention to these cells (from now named ICC). Among them, I myself concluded that ICC have smooth muscle features and might well be pacemaker cells. In this period, vital methylene-blue staining followed by electron microscopy firmly identified the ICC as myoid cells and the zinc iodide-osmic acid method, used to stain neurons, was also excellent for ICC and, when applied for electron microscopy, confirmed the identity of these cells. In the meantime different ICC populations were found in the gut muscle coat with region-specific location and region-specific features. By 1980, ICC, revealing themselves as myoid cells, a nature far more exciting than former ones, underwent to a booming interest and also physiologists began to study them. At present, it has been proved that one population, distributed throughout the entire gut, plays a pacemaker role; a second population, located intramuscularly in the stomach, is involved in neurotransmission, and a third population, specific of the small intestine, is part of the intestinal stretch receptor. By 1980 up to day, the differentiating steps of these cells were studied and factors implied in their maturation during foetal life and in the maintenance of their differentiated state in adulthood were identified. There has been also a rapidly evolving knowledge of specific molecules which are expressed on ICC, some of which useful for ICC identification under light- and electron microscope with a relative facility, some functionally implicated in neurotransmission and others in metabolic pathways strictly related to specific ICC behaviours. The more recent studies are considering the possibility of an ICC plasticity, transdifferentiation and apoptosis, especially in view of a direct implication of these cells in certain disorders of gut motility. Perspectives for future research are mainly concerning ICC alterations in gastrointestinal diseases.
A gene located on the X chromosome is responsible for the transcription of several mRNA and related dystrophin isoforms. Lack or truncated expression of the 427-kDa, full-length isoform in skeletal muscle results in Duchenne muscular dystrophy (DMD). Patients with DMD, as well as mdx mice, a mutant strain also lacking this isoform, show gastrointestinal dismotilities. The present aim was to identify the cell types that express full-length dystrophin in the gastrointestinal tract. An immunohistochemical study was performed using an antibody specific for this isoform, and double labelings were made for interstitial cells of Cajal (ICC) identification and to verify whether all neurons express full-length dystrophin. Three different fixation procedures were used. The results showed that ICC, enteric neurons, and smooth muscle and myoid cells expressed full-length dystrophin. In ICC and neurons, dystrophin-immunoreactive patches were irregularly distributed at the cell contour and within the cytoplasm. In smooth muscle and myoid cells, regularly spaced dystrophin-immunoreactive bars were located along the cell contour. Labeling intensity varied according to fixation procedure. The different subcellular distributions of dystrophin immunoreactivity might reflect diverse roles played by full-length isoforms in each cell type. Dystrophin loss in cells involved in gastrointestinal motility might explain the gastrointestinal symptomatology affecting DMD patients and mdx mice.
An experimental study was performed to investigate the effects of amnio-allantoic fluid exchange and intrauterine bicarbonate treatment on intestinal damage and interstitial cells of Cajal (ICC) in gastroschisis.
Thirteen-day-old fertilized chick eggs were randomly allocated into 4 groups as control, gastroschisis, gastroschisis + amnio-allantoic fluid exchange, and gastroschisis + bicarbonate treatment groups. In the treatment groups, amnio-allantoic exchange and bicarbonate treatments were performed for 3 days, after creating gastroschisis. Specimens were processed for hematoxylin-eosin and c-kit immunohistochemistry on the 18th day of incubation, after macroscopic examination. The intestines were evaluated with light microscopy for the presence of mucosal congestion and muscular and serosal edema. Mean muscular thickness and density of ICC were measured.
Mean muscular thickness significantly increased in the gastroschisis group when compared with control and treatment groups. Labeling intensity, morphology, and localization of the ICC were similar in all groups. Mean ICC density significantly decreased in the gastroschisis group when compared with the control group (P < .01), and it significantly increased after amnio-allantoic fluid exchange treatment (P < .01).
The decrease in ICC density encountered in damaged intestinal loops in gastroschisis was prevented with intrauterine treatment. The beneficial effects of amniotic exchange on intestinal motility may depend on both prevention of intestinal damage and preservation of ICC density and function. The density of ICC might be a reliable numeric parameter both to predict intestinal motility disorders in gastroschisis and to compare the effectiveness of intrauterine treatment methods.
This study highlights the importance of interstitial cells of Cajal (ICs) in gastrointestinal disease. Human research is already considering IC pathologies but in veterinary research IC pathologies are rarely studied. Nevertheless, recent studies of ICs show a growing interest in the pathophysiology of gastrointestinal diseases and emphasize the consideration of this cell type in the pathophysiology of veterinary gastrointestinal malfunctions.
The structural relationship of nerve, muscle, and interstitial cells of Cajal in circular muscle of the lesser curvature of the dog stomach (corpus) has been studied. This muscle has also been characterized functionally. Muscle cells are arranged in bundles and are interconnected by numerous gap junctions averaging 30 per 100 cross-sectioned muscle cells, and leading to an estimate that each cell has about 200 gap junctions. No other smooth muscle studied to date has such a high density of gap junctions. Nerve varicosities, mostly containing a predominance of small agranular vesicles with some containing a predominance of large granular vesicles, are located outside muscle bundles, usually in small- to medium-sized bundles. Very few nerves containing small granular vesicles, presumably adrenergic, were found in agreement with functional studies. A substantial number of damaged nerve profiles was also found, perhaps contributing to the loss of nerve-dependent responses present in vivo, but absent in vitro. Interstitial cells of Cajal were rare in this tissue, about 1 per 1000 cross-sectioned muscle cells. When present, they often made gap junction contact with smooth muscle and were closely innervated. The findings of a structural basis for very tight coupling between cells, the absence of a structural basis for direct neural control over motor function, and other findings have implications for the control of contractions in this muscle.
A layer of muscle cells consisting of 1–3 rows is present on the inner part of the circular layer of mouse colon. These muscle cells are thinner, with a denser cytoplasm and more caveolae than those of the main portion of the circular layer. A connective interstice divides the two parts of the circular layer and is occupied by a nerve plexus rich in varicosities. Groups of cells, identified as interstitial cells of Cajal, and a nerve plexus rich in varicosities are located on the border between the innermost circular layer and the tela submucosa. The interstitial cells have many cytological features in common with muscle cells (caveolae, basal lamina, thin filaments, smooth endoplasmic reticulum, glycogen particles) and touch each other and the nerve endings frequently and the muscle cells of the innermost layer rarely.Copyright © 1985 S. Karger AG, Basel
Field stimulation with pulses of 0.5 or 5 ms relaxed isolated strips of lower esophageal sphincter (LES) of the opossum; only responses to 0.5-ms pulses were inhibited by tetrodotoxin. Black widow spider venom prevented relaxation to both stimuli; thus both stimuli may release nonadrenergic inhibitory mediator. Isoproterenol, but not PGEs or ATP, was a consistent relaxant of LES. PGF2alpha (approximately 1 microgram/ml) and stable endoperoxides (approximately 10 ng/ml) stimulated LES muscle. Doses of indomethacin (IDM) or 5,8,11,14-eicosatetraynoic acid (ETA), which inhibited contractions to arachidonic acid increased then abolished LES tone, inhibited relaxations to 5-ms pulses and less effectively to 0.5-ms pulses. Inhibition of relaxation preceded loss of tone. Tone could be restored by carbachol, PGEs, or PGF2alpha and relaxation after IDM but not ETA was also restored. Prostaglandins may participate in functioning of nonadrenergic inhibitory nerves and in maintaining sphincter tone. Cells that did not appear to be smooth muscle were in gap junction contact with smooth muscles and closely apposed to nerves with small agranular vesicles. A role for these structures, which are postulated to be interstitial cells, in tetrodotoxin-insensitive prostaglandin-related release of nonadrenergic inhibitory mediator was proposed.
The muscular coat of human small intestine is constituted by a 'special' layer, by the main component of the circular layer, by the region between the circular and the longitudinal layers and by the longitudinal layer. The 'special' layer is made up of the innermost 4-6 rows of muscle cells of the circular layer and is separated from the main component of the circular layer by a space in which an abundant connective tissue and numerous nerve fibers rich in nerve endings are located. Cells identified as interstitial cells of Cajal are located inside the 'special' layer, the space between it and the main component of the circular layer and in the region between the circular and the longitudinal layers. In this region small bundles of obliquely orientated muscle cells, apparently bridging the circular to the longitudinal layer, are found.