József Jászai's research while affiliated with Technische Universität Dresden and other places

Reprod Med Biol. 2023;22:e12544. | 1 of 4 https://doi.org/10.1002/rmb2.12544 wileyonlinelibrary.com/journal/rmb 1 | INTRODUC TI ON Matsukuma and colleagues have recently reported that Prominin-1 deletion results in spermatogenic impairment, sperm morphological defects, and infertility in mice. 1 Prominin-1 (alias CD133) has been, for more than two decades, the subject of intensive research in various organ systems due to its expression in stem (cancer stem) cells. This pentaspan transmembrane glycoprotein (≈120 kDa) localizes specifically in highly curved membranes as in microvilli and cilia of diverse epithelial cells and in other types of protrusions of non-epithelial cells. It regulates the organization and/or dynamics of such membrane protrusions via its interactions with membrane lipids and cytoplasmic proteins. 2 | E XPRE SS I ON OF PROMININ-1 IN MALE REPRODUC TIVE SYS TEMS We reported, in 2004, its expression in murine testes and epididy-mides. 2 Using immunohistochemistry and electron microscopy, we demonstrated that Prominin-1 was concentrated in the stereocilia of the apical surface of principal cells lining the epididymal epithe-lium, all along the duct with the exception of the initial segment (see Table 1). Prominin-1 was also found on the tails of developing spermatozoa associated with contorted testis seminiferous tubules, suggesting that this molecule may play a role in spermiogenesis (the final stage of spermatogenesis), in line with its preferential subcel-lular localization in membrane protrusions. 2 Several splice variants of Prominin-1 with alternative C-termini were characterized, exhibiting lower molecular weights and differential glycosylation compared with the 120-kDa kidney form originally identified. This means that, depending on the antibody used, the full spectrum of Prominin-1 variants may not be detected, notably in the reproductive system (Table 1). 2 Prominin-1 variants with different molecular weights are indeed differentially expressed in ductuli efferentes and the epididymal tract, 2 and only a 100-kDa form of Prominin-1 harboring a truncated cytoplasmic C-terminus appears in the testis. 2,3 The relation of these alternative C-termini with differential function of Prominin-1 in these tissues remains to be experimentally addressed. Prominin-1 transcripts were later mapped in the luminal zone of the contorted seminiferous tubules containing spermatids and in the epididymal duct by in situ hybridization (Table 1). 4 Matsukuma and colleagues confirmed this last observation by β-galactosidase staining of heterozygote animals of a knock-in mouse model carrying the LacZ gene in the Prom1 locus. 1 Strikingly, while neither Prominin-1 transcript expression 4 nor LacZ staining 1 were detected in the basal portion of seminiferous tubules containing actively dividing sper-matogonia, the immunodetection in the latter study contradicted Abstract The contribution of Prominin-1 (aka CD133) to male fertility has recently been (re) investigated, with contradictory results. Early findings, essential for deciphering its role, have unfortunately been neglected. Here, the authors present what is currently known about its expression in the male reproductive system of rodents and men so that its involvement in male fertility can be reexamined and discussed in the light of these elements. K E Y W O R D S CD133, prominin-1, reproductive system, sperm cell

Low‐density lipoprotein (LDL) apheresis is effective and safe for patients with diabetes, proteinuria, and dyslipidemia. Diabetes mellitus is accompanied by ocular microvascular complications like retinal neovascularization or diabetic macular edema. These are leading causes of blindness and can be mediated by abnormal vessel growth and increased vascular permeability due to elevated levels of vascular endothelial growth factor (VEGF) in diabetic patients. In this study, we established methods to study the expression of different VEGF isoforms in human retinal and endothelial cells. The VEGF‐A165a isoform is much higher expressed in retinal cells, compared to endothelial cells. Stimulation with glyoxal as a model of oxidative stress under diabetic conditions lead to a pronounced induction of VEGF‐A165a in human retinal and endothelial cells. These data suggest that diabetes and oxidative stress induce VEGF‐A isoforms which could be relevant in regulating the ingrowths of novel blood vessels into the retina in diabetic patients.

Anti-Vascular Endothelial Growth Factor (VEGF) agents are the first-line treatment for retinal neovascular diseases, which represent the most prevalent causes of acquired vision loss world-wide. VEGF-Trap (Aflibercept, AFL), a recombinant decoy receptor recognizing ligands of both VEGFR-1 and -2, was recently reported to be highly efficient in improving visual acuity and preserving retinal anatomy in individuals affected by diabetic macular edema. However, the precise molecular and cell biological mechanisms underlying the beneficial effects of this novel tool have yet to be elucidated. Using the mouse oxygen-induced retinopathy (OIR) model as a surrogate of retinopathies with sterile post-ischemic inflammation, such as late proliferative diabetic retinopathy (PDR), retinopathy of prematurity (ROP), and diabetic macular edema (DME), we provide evidence that AFL modulates inflammation in response to hypoxia by regulating the morphology of microglial cells, a parameter commonly used as a proxy for changes in their activation state. We show that AFL administration during the hypoxic period of OIR leads to an increased number of ramified Iba1+ microglial cells/macrophages while subsequently limiting the accumulation of these cells in particular retinal layers. Our results suggest that, beyond its well-documented beneficial effects on microvascular regeneration, AFL might exert important modulatory effects on post-ischemic retinal inflammation.

Ischemic retinal dystrophies are leading causes of acquired vision loss. Although the dysregulated expression of the hypoxia-responsive VEGF-A is a major driver of ischemic retinopathies, implication of additional VEGF-family members in their pathogenesis has led to the development of multivalent anti-angiogenic tools. Designed as a decoy receptor for all ligands of VEGFR1 and VEGFR2, Aflibercept is a potent anti-angiogenic agent. Notwithstanding, the molecular mechanisms mediating Aflibercept’s efficacy remain only partially understood. Here, we used the oxygen-induced retinopathy (OIR) mouse as a model system of pathological retinal vascularization to investigate the transcriptional response of the murine retina to hypoxia and of the OIR retina to Aflibercept. While OIR severely impaired transcriptional changes normally ensuing during retinal development, analysis of gene expression patterns hinted at alterations in leukocyte recruitment during the recovery phase of the OIR protocol. Moreover, the levels of Angiopoietin-2, a major player in the progression of diabetic retinopathy, were elevated in OIR tissues and consistently downregulated by Aflibercept. Notably, GO term, KEGG pathway enrichment, and expression dynamics analyses revealed that, beyond regulating angiogenic processes, Aflibercept also modulated inflammation and supported synaptic transmission. Altogether, our findings delineate novel mechanisms potentially underlying Aflibercept’s efficacy against ischemic retinopathies.

Prominins (proms) are transmembrane glycoproteins conserved throughout the animal kingdom. They are associated with plasma membrane protrusions, such as primary cilia, as well as extracellular vesicles derived thereof. Primary cilia host numerous signaling pathways affected in diseases known as ciliopathies. Human PROM1 (CD133) is detected in both somatic and cancer stem cells and is also expressed in terminally differentiated epithelial and photoreceptor cells. Genetic mutations in the PROM1 gene result in retinal degeneration by impairing the proper formation of the outer segment of photoreceptors, a modified cilium. Here, we investigated the impact of proms on two distinct examples of ciliogenesis. First, we demonstrate that the overexpression of a dominant-negative mutant variant of human PROM1 (i.e. mutation Y819F/Y828F) significantly decreases ciliary length in Madin–Darby canine kidney cells. These results contrast strongly to the previously observed enhancing effect of wild-type PROM1 on ciliary length. Mechanistically, the mutation impeded the interaction of PROM1 with ADP-ribosylation factor-like protein 13B, a key regulator of ciliary length. Second, we observed that in vivo knockdown of prom3 in zebrafish alters the number and length of monocilia in the Kupffer’s vesicle, resulting in molecular and anatomical defects in the left–right asymmetry. These distinct loss-of-function approaches in two biological systems reveal that prom proteins are critical for the integrity and function of cilia. Our data provide new insights in ciliogenesis and might be of particular interest for investigations of the etiologies of ciliopathies.

Retinal hypoxia triggers abnormal vessel growth and microvascular hyper‐permeability in ischemic retinopathies. Whereas vascular endothelial growth factor A (VEGF‐A) inhibitors significantly hinder disease progression, their benefits to retinal neurons remain poorly understood. Similar to humans, oxygen‐induced retinopathy (OIR) mice exhibit severe retinal microvascular malformations and profound neuronal dysfunction. OIR mice are thus a phenocopy of human retinopathy of prematurity, and a proxy for investigating advanced stages of proliferative diabetic retinopathy. Hence, the OIR model offers an excellent platform for assessing morpho‐functional responses of the ischemic retina to anti‐angiogenic therapies. Using this model, we investigated the retinal responses to VEGF‐Trap (Aflibercept), an anti‐angiogenic agent recognizing ligands of VEGF receptors 1 and 2 that possesses regulatory approval for the treatment of neovascular age‐related macular degeneration, macular edema secondary to retinal vein occlusion and diabetic macular edema. Our results indicate that Aflibercept not only reduces the severity of retinal microvascular aberrations but also significantly improves neuroretinal function. Aflibercept administration significantly enhanced light‐responsiveness, as revealed by electroretinographic examinations, and led to increased numbers of dopaminergic amacrine cells. Additionally, retinal transcriptional profiling revealed the concerted regulation of both angiogenic and neuronal targets, including transcripts encoding subunits of transmitter receptors relevant to amacrine cell function. Thus, Aflibercept represents a promising therapeutic alternative for the treatment of further progressive ischemic retinal neurovasculopathies beyond the set of disease conditions for which it has regulatory approval. image Cover Image for this issue: doi: 10.1111/jnc.14743.

Excessive abnormal angiogenesis plays a pivotal role in tumor progression and is a hallmark of solid tumors. This process is driven by an imbalance between pro- and anti-angiogenic factors dominated by the tissue hypoxia-triggered overproduction of vascular endothelial growth factor (VEGF). VEGF-mediated signaling has quickly become one of the most promising anti-angiogenic therapeutic targets in oncology. Nevertheless, the clinical efficacy of this approach is severely limited in certain tumor types or shows only transient efficacy in patients. Acquired or intrinsic therapy resistance associated with anti-VEGF monotherapeutic approaches indicates the necessity of a paradigm change when targeting neoangiogenesis in solid tumors. In this context, the elaboration of the conceptual framework of “vessel normalization” might be a promising approach to increase the efficacy of anti-angiogenic therapies and the survival rates of patients. Indeed, the promotion of vessel maturation instead of regressing tumors by vaso-obliteration could result in reduced tumor hypoxia and improved drug delivery. The implementation of such anti-angiogenic strategies, however, faces several pitfalls due to the potential involvement of multiple pro-angiogenic factors and modulatory effects of the innate and adaptive immune system. Thus, effective treatments bypassing relapses associated with anti-VEGF monotherapies or breaking the intrinsic therapy resistance of solid tumors might use combination therapies or agents with a multimodal mode of action. This review enumerates some of the current approaches and possible future directions of treating solid tumors by targeting neovascularization.

This chapter introduces the basic biology of CD133 (alias prominin-1), a cholesterol-binding pentaspan membrane glycoprotein that has gained enormous interest in the stem cell field. As a cell surface antigen, CD133 has become a prominent marker used for the prospective isolation and characterization of cells with stem cell properties in neural development and adult brain as well as in cancer. Beyond its application as a new biological tool for tissue engineering and regenerative therapy, CD133 has highlighted new aspects of the visual system because mutations in the PROM1 gene cause retinal pathologies. Here, we will summarize the essentials regarding the basic molecular and cellular biology of CD133 necessary for the proper evaluation of its detection in a given cell population under physiological or pathological conditions with a special focus on the neural system across species.

Kusaba et al. provide additional evidence using genetic lineage analysis that epithelial cell dedifferentiation is responsible for repair of proximal tubules after injury in mouse (1). These data challenge the hypothesis of the implication of scattered stem cells in such a process or highlight a potential distinction between rodent and human. To substantiate their conclusion, the authors evaluated the expression of stem/progenitor (S/P) markers among which is CD133 (prominin-1), a cell surface antigen whose value in identifying S/P cells in various organs and neoplastic tissues is the subject of intense investigations. Beside S/P cells, it is documented that CD133 is expressed at the apical membrane of polarized cells found in numerous mouse and human terminally differentiated epithelia, notably kidney proximal tubules (2, 3) (see below). Kusaba et al. (1) surprisingly did not investigate the actual status of the CD133 protein, but instead let their work rely solely on PCR. However, the detection of CD133 transcripts, which may appear as different splice variants, is not necessarily correlated with the expression of its protein product (4). Moreover, the forward primer listed in this study (1) is not specific for CD133; it therefore remains to be determined whether CD133 transcripts are up-regulated in mouse tubular epithelia after injury, and it might be interesting to dissect the expression of CD133 variants within the nephron to see if one (or several) of them is specifically associated with tubular cell repair.