Telocytes in female reproductive system (human and animal)

Telocytes: current methods of research, challenges and future perspectives

Telocytes (TCs) are CD34-positive interstitial cells that have long cytoplasmic projections, called telopodes; they have been identified in several organs and in various species. These cells establish a complex communication network between different stromal and epithelial cell types, and there is growing evidence that they play a key role in physiology and pathology. In many tissues, TC network impairment has been implicated in the onset and progression of pathological conditions, which makes the study of TCs of great interest for the development of novel therapies. In this review, we summarise the main methods involved in the characterisation of these cells as well as their inherent difficulties and then discuss the functional assays that are used to uncover the role of TCs in normal and pathological conditions, from the most traditional to the most recent. Furthermore, we provide future perspectives in the study of TCs, especially regarding the establishment of more precise markers, commercial lineages and means for drug delivery and genetic editing that directly target TCs.

Histological study of telocytes in mice intrauterine adhesion model and their positive effect on mesenchymal stem cells in vitro

Intrauterine adhesions (IUA), the main cause of secondary infertility in women, result from irreversible fibrotic repair of the endometrium due to inflammation or human factors, accompanied by disruptions in the repair function of endometrial stem cells. This significantly impacts the physical and mental health of women in their childbearing years. Telocytes (TCs), a distinctive type of interstitial cells found in various tissues and organs, play diverse repair functions due to their unique spatial structure. In this study, we conduct the inaugural exploration of the changes in TCs in IUA disease and their potential impact on the function of stem cells. Our results show that in vivo, through double immunofluorescence staining (CD34+/Vimentin+; CD34+/CD31-), as endometrial fibrosis deepens, the number of TCs gradually decreases, telopodes shorten, and the three-dimensional structure becomes disrupted in the mouse IUA mode. In vitro, TCs can promote the proliferation and cycle of bone mesenchymal stem cells (BMSCs) by promoting the Wnt/β-catenin signaling pathway, which were inhibited using XAV939. TCs can promote the migrated ability of BMSCs and contribute to the repair of stem cells during endometrial injury. In addition, TCs can inhibit the apoptosis of BMSCs through the Bcl-2/Bax pathway. In conclusion, our study demonstrates, for the first time, the resistance role of TCs in IUA disease, shedding light on their potential involvement in endometrial repair through the modulation of stem cell function.

Toward understanding the role of the interstitial tissue architects: Possible functions of telocytes in the male gonad

Telocytes represent a relatively recently discovered population of interstitial cells with a unique morphological structure that distinguishes them from other neighboring cells. Through their long protrusions extending from the cell body, telocytes create microenvironments via tissue compartmentalization and create homo- and hetero-cellular junctions. These establish a three-dimensional network enabling the maintenance of interstitial compartment homeostasis through regulation of extracellular matrix organization and activity, structural support, paracrine and juxtracrine communication, immunomodulation, immune surveillance, cell survival, and apoptosis. The presence of telocytes has also been confirmed in testicular interstitial tissue of many species of animals. The objective of this review is to summarize recent findings on telocytes in the male gonad, on which conclusions have been deduced that indicate the involvement of telocytes in maintaining the cytoarchitecture of the testicular interstitial tissue, in the processes of spermatogenesis and steroidogenesis, and photoperiod-mediated changes in the testes in seasonally reproductive animals.

Unveiling Cellular Diversity in the Buffalo Corneal Stroma: Insights into Telocytes and Keratocytes Using Light Microscope, Transmission Electron Microscope, and Immunofluorescence Analysis

Telocytes and keratocytes are important cells that maintain the structure and function of the cornea. The buffalo cornea, known for its resilience in harsh conditions, has not been extensively studied regarding the presence and role of telocytes and keratocytes. We used light microscopy, transmission electron microscopy (TEM), and immunofluorescence assays with platelet-derived growth factor receptor alpha (PDGFRα), CD34, and Vimentin markers to investigate their expression and localization in the cornea. TEM analysis confirmed the presence of spindle-shaped keratocytes with intercellular connections, while telocytes exhibited small spindle-shaped bodies with long, thin branches connecting to corneal keratocytes. Immunofluorescence findings showed that CD34 was more abundant near the endothelium, Vimentin was prominently expressed near the epithelium, and PDGFRα was uniformly distributed throughout the corneal stroma. Co-expression of CD34 and Vimentin, PDGFRα and Vimentin, as well as CD34 and PDGFRα, was observed in keratocytes and telocytes within the stroma, indicating the potential presence of mesenchymal cells. These results suggest the involvement of telocytes and keratocytes in corneal wound healing, transparency maintenance, and homeostasis. The co-expression of these markers highlights the critical role of telocytes and keratocytes in regulating corneal physiological functions, further enhancing our understanding of corneal biology in the buffalo model.

Current status and challenges in uterine myometrial tissue engineering

The uterus undergoes significant modifications throughout pregnancy to support embryo development and fetal growth. However, conditions like fibroids, adenomyosis, cysts, and C-section scarring can cause myometrial damage. The importance of the uterus and the challenges associated with myometrial damage, and the need for alternative approaches are discussed in this review. The review also explores the recent studies in tissue engineering, which involve principles of combining cells, scaffolds, and signaling molecules to create functional uterine tissues. It focuses on two key approaches in uterine tissue engineering: scaffold technique using decellularized, natural, and synthetic polymer and 3D bioprinting. These techniques create supportive structures for cell growth and tissue formation. Current treatment options for myometrial damage have limitations, leading to the exploration of regenerative medicine and integrative therapies. The review emphasizes the potential benefits of tissue engineering, including more effective and less invasive treatment options for myometrial damage. The challenges of developing biocompatible materials and optimizing cell growth and differentiation are discussed. In conclusion, uterine tissue engineering holds promise for myometrial regeneration and the treatment of related conditions. This review highlights the scientific advancements in the field and underscores the potential of tissue engineering as a viable approach. By addressing the limitations of current treatments, tissue engineering offers new possibilities for improving reproductive health and restoring uterine functionality. Future research shall focus on overcoming challenges and refining tissue engineering strategies to advance the field and provide effective solutions for myometrial damage and associated disorders.

Involvement of small leucine-rich proteoglycans and telocytes in thin and thick human endometrium: immunohistochemical and ultrastructural examination

Thin endometrium, defined as an endometrial thickness of less than 7 mm during the late follicular phase, is a common cause of frequent cancelation of embryo transfers or recurrent implantation failure during assisted reproductive treatment. Small proteoglycans regulate intracellular signaling cascades by bridging other matrix molecules and tissue elements, affecting cell proliferation, adhesion, migration, and cytokine concentration. The aim of the study is to investigate the role of small leucine-rich proteoglycans in the pathogenesis of thin and thick human endometrium and their differences from normal endometrium in terms of fine structure properties. Normal, thin, and thick endometrial samples were collected, and small leucine-rich proteoglycans (SLRPs), decorin, lumican, biglycan, and fibromodulin immunoreactivities were comparatively analyzed immunohistochemically. The data were compared statistically. Moreover, ultrastructural differences among the groups were evaluated by transmission electron microscopy. The immunoreactivities of decorin, lumican, and biglycan were higher in the thin endometrial glandular epithelium and stroma compared to the normal and thick endometrium (p < .001). Fibromodulin immunoreactivity was also higher in the thin endometrial glandular epithelium than in the normal and thick endometrium (p < .001). However, there was no statistical difference in the stroma among the groups. Ultrastructural features were not profoundly different among cases. Telocytes, however, were not seen in the thin endometrium in contrast to normal and thin endometrial tissues. These findings suggest a possible role of changes in proteoglycan levels in the pathogenesis of thin endometrium.

Immunohistochemical and ultrastructural identification of telocytes in the lamina propria of human vaginal mucosa

Since their relatively recent discovery, telocytes (TCs) have been described as peculiar cells strategically positioned in the stromal tissue component of multiple organ systems of the mammalian body including female reproductive organs (i.e., ovary, uterine tube, and uterus). Nevertheless, current knowledge of TCs in the vagina is very limited. The present study was therefore undertaken to investigate the existence and characteristics of TCs in the stromal tissue of human vaginal mucosa by means of immunohistochemistry, immunofluorescence confocal microscopy, and transmission electron microscopy. In the vaginal lamina propria, TCs were first identified by CD34 immunohistochemistry that revealed the presence of CD34+ stromal cells arranged in networks, especially around blood vessels. Double immunofluorescence confocal microscopy allowed to precisely distinguish the perivascular networks of CD34+ stromal cells lacking CD31 immunoreactivity from adjacent CD31+ microvessels. All the perivascular networks of TCs/CD34+ stromal cells situated in the vaginal lamina propria coexpressed platelet-derived growth factor receptor α, which strengthened their identification as TCs. Instead, vaginal mucosal TCs were immunophenotypically negative for c-kit/CD117. The ultrastructural examination confirmed the presence of TCs, namely stromal cells with characteristic cytoplasmic processes (i.e., telopodes) forming labyrinthine networks around blood vessels and releasing extracellular vesicles. Together, our morphological findings provide the first comprehensive demonstration that TCs reside in the human vaginal lamina propria, thus paving the way for further investigation of their putative functions in vaginal mucosal homeostasis and pathophysiology.

Pathophysiological Implications of Interstitial Cajal-like Cells (ICC-like) in Uterus: A Comparative Study with Gastrointestinal ICCs

The main function of interstitial cells of Cajal (ICCs) is to regulate gastrointestinal peristalsis by acting as a "pacemaker" cell by generating spontaneous slow electrical waves. In 2005, electron microscopy revealed a cell type similar to ICCs (ICC-like) outside the gastrointestinal tract, with contractile activity and c-Kit+ immunohistochemistry shared with ICCs. Among the locations where ICC-like cells have been observed, it is in the uterus where they have a significant functional and pathophysiological role. These cells are involved in obstetric phenomena of contractile action, such as ascending sperm transport, embryo implantation, pregnancy, delivery, and the expulsion of menstrual debris. Within the pathophysiology related to these cells, we find obstetric alterations such as recurrent miscarriages, premature deliveries, abolition of uterine contractions, and failures of embryo implantation, in addition to other common conditions in the fertile age, such as endometriosis and leiomyoma.

Identification and protective role of CD34+ stromal cells/telocytes in experimental autoimmune encephalomyelitis (EAE) mouse spleen

Experimental autoimmune encephalomyelitis (EAE) is a classical animal model of human multiple sclerosis (MS) that is most commonly used to study the neuropathology and therapeutic effects of the disease. Telocytes (TCs) are a specialized type of interstitial or mesenchymal cell first identified by Popescu in various tissues and organs. However, the existence, distribution and role of CD34⁺ stromal cells (SCs)/TCs in the EAE-induced mouse spleen remain to be elucidated. We conducted immunohistochemistry, immunofluorescence (double staining for CD34 and c-kit, vimentin, F4/80, CD163, Nanog, Sca-1, CD31 or tryptase) and transmission electron microscopy experiments to investigate the existence, distribution and role of CD34⁺ SCs/TCs in the EAE-induced mouse spleen. Interestingly, immunohistochemistry, double-immunofluorescence, and transmission electron microscopy results revealed that CD34⁺ SCs/TCs were significantly upregulated in the EAE mouse spleen. Immunohistochemical or double-immunofluorescence staining of CD34⁺ SCs/TCs showed positive expression for CD34, c-kit, vimentin, CD34/vimentin, c-kit/vimentin and CD34/c-kit, and negative expression for CD31 and tryptase. Transmission electron microscopy (TEM) results demonstrated that CD34⁺ SCs/TCs established close connections with lymphocytes, reticular cells, macrophages, endothelial cells and erythrocytes. Furthermore, we also found that M1 (F4/80) or M2 (CD163) macrophages, and haematopoietic, pluripotent stem cells were markedly increased in EAE mice. Our results suggest that CD34⁺ SCs/TCs are abundant and may play a contributing role in modulating the immune response, recruiting macrophages and proliferation of haematopoietic and pluripotent stem cells following injury to promote tissue repair and regeneration in EAE mouse spleens. This suggests that their transplantation combined with stem cells might represent a promising therapeutic target for the treatment and prevention of multiple autoimmune and chronic inflammatory disorders.

Morphological and histochemical identification of telocytes in adult yak epididymis

Telocytes (TCs) are a newly discovered type of mesenchymal cell that are closely related to the tissue's internal environment. The study aimed to investigate the morphological identification of TCs in the epididymis of adult yak and their role in the local microenvironment. In this study, transmission electron microscopy (TEM), scanning electron microscopy, immunofluorescence, qRT-PCR, and western blotting were used to analyze the cell morphology of TCs. The results showed that there are two types of TCs in the epididymal stroma of yak by TEM; one type is distributed around the capillaries with full cell bodies, longer TPs, and a large number of secretory vesicles; the other is distributed outside the basement membrane with irregularly long, striped, large nuclei and short telopodes (TPs). In addition, these TCs formed complex TC cell networks through TPs with epididymal interstitial capillaries and basal fibroblasts. TCs often appear near the capillaries and basement membrane by special staining. The surface markers of TCs (CD34, vimentin, and CD117) were positively expressed in the epididymal stroma and epithelium by immunohistochemistry, and immunofluorescence co-expression of vimentin + CD34 and CD117 + CD34 was observed on the surface of TCs. The trends in the mRNA and protein expression of TCs surface markers revealed expression was highest in the caput epididymis. In summary, this is first report of TCs in the epididymis of yak, and two phenotypes of TCs were observed. The existence and distribution characteristics of TCs in the epididymis of plateau yaks provide important clues for further study of the adaptation to reproductive function in the plateau.

Microbiota metabolites in the female reproductive system: Focused on the short-chain fatty acids

Several disorders have been linked to modifications in the gut microbial imbalance, intestinal epithelium, and host immune system. In this regard, microbiota derived short-chain fatty acids (SCFAs) play a key function in the regulation of histone deacetylases (HDACs), which affect modulation of immunity and regulation of inflammatory responses in the intestine and other organs. Studies examining the metabolites produced by polymicrobial bacterial vaginosis (BV) states and Lactobacillus-dominated microbiota have noted a dramatic reduction of lactic acid and a shift toward SCFA synthesis. Along with higher levels of SCFAs, acetate is typically the main metabolite in the cervicovaginal fluid of women with symptomatic bacterial vaginosis. The fact that SCFAs made by the vaginal microbiota have been shown to exhibit antibacterial and immune-modulating properties suggests that they may have promise as indicators of disease and/or disease susceptibility. In this review, we overview and summarize the current findings on the detrimental or protective roles of microbiota metabolites especially SCFAs in the health and disease of the female reproductive system.

Telocytes and endometriosis

Endometriosis involving the presence and growth of glands and stroma outside the uterine cavity is a common, inflammatory, benign gynecologic disease. Nevertheless, no single theory can exactly account for the pathogenesis of endometriosis. Telocytes, a kind of novel mesenchymal cells, have been suggested to be crucial in promoting angiogenesis and increasing the activity of endometrial interstitial cells and inflammatory cells. Given above roles, telocytes may be considered as the possible pathogenesis of endometriosis. We reviewed the current literature on telocytes. The following aspects were considered: (A) the telocytes' typical characteristics, function, and morphological changes in endometriosis; (B) the potential role of telocytes in endometriosis by impacting the inflammation, invasion, and angiogenesis; (C) telocytes as the potential treatment options for endometriosis.

The Mechanism of Wnt Pathway Regulated by Telocytes to Promote the Regeneration and Repair of Intrauterine Adhesions

Background

Telocytes (TCs), a novel interstitial cell type in the reproductive tract, participating in pathophysiology of intrauterine adhesions (IUA). This study further investigates the hypothesis that TCs, a source of Wnt, promote the regeneration and repair of IUA.

Methods

RNA sequencing datasets of IUA patient (GSE160633) and mouse intestine mesenchymal cells (GSE94072) in GEO database were analyzed for differentially expressed genes (DEGs), and quantitative real-time PCR (qRT-PCR) measured indicated gene expression in TC-educated endometrial stromal cells (ESCs) and noneducated ESCs and verified the results of data mining from GEO database.

Results

The expression levels of Wnt genes were downregulated in IUA compared to the control and were upregulated in TCs. In particular, the changes of Wnt5a expression level were the most significant (logFC = 4.0314 and adjusted P value = 0.0023), and the relative Wnt5a expression level was remarkably higher in TC-educated ESCs than noneducated ESCs verified by qRT-PCR (P = 0.0027).

Conclusions

TCs may enhance the regeneration and repair of IUA through the Wnt signaling pathway.

Oviductal Oxygen Homeostasis in Patients with Uterine Myoma: Correlation between Hypoxia and Telocytes

Oxygen balance is crucial for angiogenesis, immunity, and tissue repair. The human oviduct is essential for reproductive function, and any imbalance in homeostasis leads to fertility disturbances and might be a reason for ectopic pregnancy development. Uterine myoma is a widespread benign tumour, which is often accompanied by infertility. Telocytes have been discussed in the contexts of motility, fibrosis development, and angiogenesis. We observed the oviducts from patients with and without uterine myoma, comparing the expression of HIF-1, HO, VEGF and its receptor, NOS, oestrogen, and progesterone receptors by immunolabeling. The myometrial and oviductal telocytes were also compared in both groups. Biochemical analyses were conducted for FSH, LH, AMH, sFlt, oestrogen, and progesterone in blood samples. Patients with uterine myoma have different expressions of sex steroid receptors and an increased number of telocytes. The decreasing VEFG expression was compensated by the rise in the HIF-1 and NOS expression. Blood biochemical analyses revealed a higher progesterone level and lower AMH in patients with uterine myoma. No differences in sFlt, FSH, and LF were observed. Uterine myoma impacts oviduct oxygen homeostasis and might cause fertility disturbances (uterine and oviductal infertility factors).

Identification of PDGFRα+ cells in uterine fibroids - link between angiogenesis and uterine telocytes

INTRODUCTION

Telocytes (TCs), also called interstitial Cajal-like cells (ICLC), CD34+ cells or PDGFRα+ cells (platelet-derived growth factor receptor α positive cells), a new type of cell of mesenchymal origin, were described over one decade ago. The unique nature of these cells still deserves attention from the scientific community. Telocytes make homo- and heterocellular contact with myocytes, immunocytes and nerves, have their own immunohistochemical and secretome profiles and thus might regulate local regenerative processes including angiogenesis and fibrosis. The aim of our study was to observe the missing link between angiogenesis and telocytes in leiomyoma, the most common benign tumors affecting women of reproductive age.

MATERIAL AND METHODS

We observed uterine tissue samples from leiomyoma, adjacent myometrium and unchanged tissue from patients with leiomyoma and control subjects using routine histology, histochemistry, immunofluorescence (CD117, CD31, CD34, PDGFRα, tryptase, sFlt-1) and image analysis methods.

RESULTS

The decline of the telocyte density in the foci of fibroids correlated with poor vascularization inside the leiomyoma. Moreover, the expression of sFlt-1 (anti-angiogenic-related factor) significantly increased inside a fibroid. In leiomyoma the decrease of telocyte and blood micro-vessel density was accompanied by prevalence of collagen deposits, unlike the unchanged myometrium.

CONCLUSIONS

Our results demonstrate TCs in human uterine fibroids and highlight their possible involvement in the pathogenesis of myometrial pathology in the context of angiogenesis.

Telocytes in the Tumor Microenvironment

There are several theories explaining the communication between cells in the context of tumor development. Over the years, interactions between normal and transformed cells have been observed. Generally, all types of cells make equal contributions to the formation of the tumor microenvironment - a location of primary oncogenesis. To date, several studies have reported the role of telocytes in cancer development, and many publications have emphasized the direct and indirect involvement of telocytes in angiogenesis; signaling through the secretion of extracellular vesicles, growth factors, and bioactive molecules; fibrosis development and extracellular matrix production; tissue repair and regeneration; and immune responses. Considering the main components of the tumor microenvironment, we will discuss the features of telocytes and their possible involvement in local tissue homeostasis.

Functional state of the myometrium of rats under chronic in vivo effect of nanostructured ZnO and ТіО2 materials

The specificities of the structure and blood supply of the uterus facilitate a considerable accumulation of nanosized xenobiotics, including nanoparticles of metal oxides, in its tissues. Numerous in vitro and in vivo experiments demonstrated that nanoparticles of metal oxides (ZnO and TiO2) have significant cytotoxic activity, caused by oxidative stress induction. However, there is no information about the impact of these nanomaterials on the functional state of the myometrium under chronic exposure on the organism. Tenzometric methods and mechanokinetic analysis were used in our work to investigate the contractile activity of the myometrium of non-pregnant rats. The contractile activity was either spontaneous or induced by oxytocin (the uterotonic hormone) and acetylcholine (the agonist of muscarinic choline receptors) under chronic peroral intake of the ZnO and TiO2 aqueous nanocolloids into the organism. It was found that after burdening of rats with ZnO and ТіО2 aqueous nanocolloids there were no changes in the pacemaker-dependent mechanisms forming the frequency of spontaneous contractions in the myometrium, but there was a considerably induced increase in the AU index of contractions. It was shown that during the oxytocin-induced excitation of the myometrium under both chronic and short-term burdening of the rats with ZnO and TiO2 aqueous nanocolloids, the mechanisms that regulate the intracellular concentration of Ca2+ ions are the target for the nanomaterials. When the rats were burdened with ZnO aqueous nanocolloids for 6 months, during cholinergic excitation there was hyperstimulation of both M3-receptor-dependent mechanisms of Са2+ ions intake via the potential-governed Са2+-channels of L-type into the smooth muscles of the myometrium, and M2-receptor-dependent mechanisms, controlling the intracellular concentration of these cations. Thus, the regularities and mechanisms of the change in the functioning of uterine smooth muscles under chronic intake of the ZnO and TiO2 aqueous nanocolloids were determined in this study.

Oviductal Telocytes in Patients with Uterine Myoma

Tubal factor infertility occurs in 30–35% of infertile pairs and may be caused by impaired muscular contractility and ciliary beating as well as immunological imbalance and chronic inflammation. Newly discovered telocytes (TCs) have a wide palette of features, which play a role in oviduct physiology. We have observed tissue samples from human fallopian tubes in patients with and without uterine myoma by immunolabelling. According to the immunohistochemical co-expression of markers, it has been determined that TCs are engaged in a wide range of physiological processes, including local innervation, sensitivity to hypoxia, regulation of calcium, and sex steroid hormones balances. Due to the proximity of NOS- and ChAT-positive nerve fibers and the expression of ion channels markers, tubal TCs might be considered conductor cells. Additionally, their integration in contractions and cilia physiology in the context of fertility has been revealed. We have observed the difference in telocytes expression in the human oviduct between groups of patients and attempted to describe this population of cells specifically in the case of infertility development, a clinically relevant avenue for further studies.

Telocytes of the male urogenital system: Interrelationships, possible functions, and pathological implications

The male urogenital system is composed of the reproductive system and the urinary tract; they have an interconnected embryonic development and share one of their anatomical components, the urethra. This system has a highly complex physiology deeply interconnected with the circulatory and nervous systems, as well as being capable of adapting to environmental variations; it also undergoes changes with aging and, in the case of the reproductive system, with seasonality. The stroma is an essential component in this physiological plasticity and its complexity has increased with the description in the last decade of a new cell type, the telocyte. Several studies have demonstrated the presence of telocytes in the organs of the male urogenital system and other systems; however, their exact function is not yet known. The present review addresses current knowledge about telocytes in the urogenital system in terms of their locations, interrelationships, possible functions and pathological implications. It has been found that telocytes in the urogenital system possibly have a leading role in stromal tissue organization/maintenance, in addition to participation in stem cell niches and an association with the immune system, as well as specific functions in the urogenital system, lipid synthesis in the testes, erythropoiesis in the kidneys and the micturition reflex in the bladder. There is also evidence that telocytes are involved in pathologies in the kidneys, urethra, bladder, prostate, and testes.

Telocytes Enhances M1 Differentiation and Phagocytosis While Inhibits Mitochondria-Mediated Apoptosis Via Activation of NF-κB in Macrophages

Telocytes (TCs), which are a recently discovered interstitial cell type present in various organs and tissues, perform multiple biological functions and participate in extensive crosstalk with neighboring cells. Endometriosis (EMs) is a gynecological disease characterized by the presence of viable endometrial debris and impaired macrophage phagocytosis in the peritoneal environment. Here, CD34/vimentin-positive TCs were co-cultured with RAW264.7 cells in vitro. M1/M2 differentiation-related markers were detected; phagocytosis, energy metabolism, proliferation, apoptosis, and pathway mechanisms were studied; and the mitochondrial membrane potential (ΔΨm) was measured. Furthermore, in an EMs mouse model, the differentiation of macrophages in response to treatment with TC-conditioned medium (TCM) in vivo was studied. The results showed that upon in vitro co-culture with TCM, RAW264.7 cells differentiated more toward the M1 phenotype with enhancement of phagocytosis, increase in energy metabolism and proliferation owing to reduced the loss of ΔΨm, and suppression of dexamethasone-induced apoptosis. Further, along with the activation of NF-κB, Bcl-2 and Bcl-xl, the expression of Bax, cleaved-caspase9, and cleaved-caspase3 reduced in RAW264.7 cells. In addition, the M1 subtype was found to be the dominant phenotype among tissue and peritoneal macrophages in the EMs model subjected to in vivo TCM treatment. In conclusion, TCs enhanced M1 differentiation and phagocytosis while inhibiting apoptosis via the activation of NF-κB in macrophages, which potentially inhibited the onset of EMs. Our findings provide a potential research target and the scope for developing a promising therapeutic strategy for EMs.

Identification of CD34+/PGDFRα+ Valve Interstitial Cells (VICs) in Human Aortic Valves: Association of Their Abundance, Morphology and Spatial Organization with Early Calcific Remodeling

Aortic valve interstitial cells (VICs) constitute a heterogeneous population involved in the maintenance of unique valvular architecture, ensuring proper hemodynamic function but also engaged in valve degeneration. Recently, cells similar to telocytes/interstitial Cajal-like cells described in various organs were found in heart valves. The aim of this study was to examine the density, distribution, and spatial organization of a VIC subset co-expressing CD34 and PDGFRα in normal aortic valves and to investigate if these cells are associated with the occurrence of early signs of valve calcific remodeling. We examined 28 human aortic valves obtained upon autopsy. General valve morphology and the early signs of degeneration were assessed histochemically. The studied VICs were identified by immunofluorescence (CD34, PDGFRα, vimentin), and their number in standardized parts and layers of the valves was evaluated. In order to show the complex three-dimensional structure of CD34+/PDGFRα+ VICs, whole-mount specimens were imaged by confocal microscopy, and subsequently rendered using the Imaris (Bitplane AG, Zürich, Switzerland) software. CD34+/PDGFRα+ VICs were found in all examined valves, showing significant differences in the number, distribution within valve tissue, spatial organization, and morphology (spherical/oval without projections; numerous short projections; long, branching, occasionally moniliform projections). Such a complex morphology was associated with the younger age of the subjects, and these VICs were more frequent in the spongiosa layer of the valve. Both the number and percentage of CD34+/PDGFRα+ VICs were inversely correlated with the age of the subjects. Valves with histochemical signs of early calcification contained a lower number of CD34+/PDGFRα+ cells. They were less numerous in proximal parts of the cusps, i.e., areas prone to calcification. The results suggest that normal aortic valves contain a subpopulation of CD34+/PDGFRα+ VICs, which might be involved in the maintenance of local microenvironment resisting to pathologic remodeling. Their reduced number in older age could limit the self-regenerative properties of the valve stroma.

Telocytes enhanced in vitro decidualization and mesenchymal-epithelial transition in endometrial stromal cells via Wnt/β-catenin signaling pathway

Decidualization of endometrial stromal cells (ESCs) is essential for preparing endometrium for embryo implantation. Telocytes (TCs), a novel type of interstitial cell, exist in the female reproductive tract and participate in the pathophysiology of diseases. This study further investigates the hypothesis that TCs, a source of Wnt, modulates decidualization and MET in ESCs. We had observed differential expression of Wnt ligands in primary mice ESCs and TCs by qPCR. TCM-induced decidualization and MET was assessed in ESCs. Changes in markers for decidualization (cyclin-D3, desmin, d/tPRP), stromal cells (N-cadherin), epithelial cells (E-cadherin), and the Wnt/β-catenin pathway (β-catenin, FOXO1) were quantified by western blot and RT-PCR. β-catenin knockdown in ESCs decreased the degree of TCM-induced decidualization and MET, with significantly reversed expression profiles (P < 0.05). This is the first study to show that TCs can enhance decidualization and MET in ESCs through the Wnt/β-catenin signaling-pathway. Therefore, we describe a promising cell therapy for gynecological conditions and related reproductive problems associated with defective decidualization.

Morphological and immunophenotypic characterization of perivascular interstitial cells in human glioma: Telocytes, pericytes, and mixed immunophenotypes

Telocytes (Tcs) and pericytes (Pcs) are two types of perivascular interstitial cell known to be widespread in various organs and tissues, including the brain. We postulated that Tcs and Pcs may be involved in glioblastoma (GBM) neovascularization.

Telocytes constitute a widespread interstitial meshwork in the lamina propria and underlying striated muscle of human tongue

Telocytes have recently emerged as unique interstitial cells defined by their extremely long, thin and moniliform prolongations termed telopodes. Despite growing evidence that these cells consistently reside in the stromal compartment of various organs from human beings, studies dealing with telocytes in structures of the oral cavity are scarce. Hence, the present morphologic study was undertaken to explore for the first time the presence and specific localization of telocytes within tissues of the normal human tongue, a complex muscular organ whose main functions include taste, speech, and food manipulation in the oral cavity. Telocytes were initially identified by CD34 immunostaining and confirmed by CD34/PDGFRα double immunofluorescence and transmission electron microscopy. CD34+/PDGFRα+ telocytes were organized in interstitial meshworks either in the tongue lamina propria or in the underlying striated muscle. Lingual telocytes were immunonegative for CD31, c-kit and α-SMA. Telopodes were finely distributed throughout the stromal space and concentrated beneath the lingual epithelium and around CD31+ vessels, skeletal muscle bundles/fibers, and intramuscular nerves and ganglia. They also enveloped salivary gland units outside the α-SMA+ myoepithelial cells and delimited lymphoid aggregates. These findings establish telocytes as a previously overlooked interstitial cell population worth investigating further in the setting of human tongue pathophysiology.

The Autonomic Innervation and Uterine Telocyte Interplay in Leiomyoma Formation

The autonomic innervation of the uterus is involved in multiple pathophysiological processes in both humans and animals. Pathological conditions such as adenomyosis or inflammatory pelvic disease are usually accompanied by significant alterations in uterine innervation. In the current study, we focused on autonomic innervation of uterine fibroids, the identification of recently described interstitial cells, telocytes, and the possible interplay between these structures. In this work, uterine telocytes were identified by immunopositivity for c-kit, CD34, and PDGFRα. Nerves were revealed by immunolabeling for neuronal markers: protein gene product PGP 9.5, inducible nitric oxide synthase (iNOS), choline acetyltransferase (ChAT), and tyrosine hydroxylase (TH). The gross organization of myometrial tissue has been analyzed by routine histology. The results demonstrated that the density of iNOS and ChAT-immunopositive neurons in the uterine fibroids was higher than that in the control samples. The density of telocytes in the fibrosis foci was lower than that in the normal myometrium. Our results suggest that autonomic innervation and telocytes are involved in the microenvironment imbalance characteristic of uterine leiomyoma. Since NOS-positive nerves play an important role in oxidative stress modulation, they might lead to a decrease in the number of telocytes, which are crucial components in the pathogenesis of leiomyoma formation.

Telocytes enhanced the proliferation, adhesion and motility of endometrial stromal cells as mediated by the ERK pathway in vitro

Telocytes (TCs) is special interstitial cell that have recently been identified in the female reproductive system. Endometriosis (EMs) is a benign gynecological disease whose etiology is still not fully clear. Implantation and proliferation of endometrial stromal cells (ESCs) out of the uterus are essential processes in the development of EMs. Herein, we investigate the in vitro changes of ESCs when cocultured with TCs, and the potential mechanisms involved. The current results demonstrated that, vimentin-positive/pan cytokeratin-negative ESCs, and TCs with a characteristic structure and immunophenotype (CD34/vimentin double-positive) were successfully isolated and harvested. Morphologically, direct cell-to-cell contacts were observed between TCs and ESCs. Quantitatively, TCs treatment clearly promotes the viability of ESCs, enhances cell cycle progression at G2/M phase and upregulates p-ERK1/2 and cyclin-D3 (all P < 0.05). Functionally, ESCs educated by TCs displayed significantly enhanced adhesion ability and accelerated invasion and migration capacity (all P < 0.05). However, no significant changes were found in the rate of apoptosis and in the expression of AKT signaling pathway proteins in TCs-educated ESCs (both P > 0.05). Therefore, TCs treatment obviously enhanced the in vitro motile and invasive capacity of ESCs, which were mediated by the ERK-cyclin-D3 signaling pathway, likely through direct intercellular contacts and/or juxta-paracrine effects; signaling through this axis therefore increased the likelihood of EMs. The enhanced functions of TCs-educated ESCs not only contribute to a deeper understanding of TCs, but also highlight a new concept regarding the physiopathology and therapy of EMs and associated impaired reproductive function.

Reappraising the microscopic anatomy of human testis: identification of telocyte networks in the peritubular and intertubular stromal space

Telocytes are a recently described stromal cell type widely distributed in various organs including the female and male reproductive systems. This study was aimed to investigate for the first time the existence, distribution and characteristics of telocytes in normal human testis by an integrated morphological approach (immunohistochemistry, immunofluorescence and transmission electron microscopy). We found that telocytes displaying typical long and moniliform prolongations and coexpressing CD34 and PDGFRα formed networks in the outer layer of peritubular tissue and around Leydig cells and vessels in the intertubular stroma. Testicular telocytes were immunophenotypically negative for CD31, c-kit/CD117 as well as α-SMA, thus making them clearly distinguishable from myoid cells/myofibroblasts located in the inner layer of peritubular tissue. Transmission electron microscopy confirmed the presence of cells ultrastructurally identifiable as telocytes (i.e. cells with telopodes alternating podomers and podoms) in the aforementioned locations. Intercellular contacts between neighboring telocytes and telopodes were observed throughout the testicular stromal compartment. Telopodes intimately surrounded and often established close contacts with peritubular myoid cells/myofibroblasts, Leydig cells and vessels. Extracellular vesicles were also frequently detected near telopodes. In summary, we demonstrated that telocytes are a previously neglected stromal component of human testis with potential implications in tissue homeostasis deserving further investigation.

Genetic Variation at Chromosome 2q13 and Its Potential Influence on Endometriosis Susceptibility Through Effects on the IL-1 Family

Endometriosis is characterized by the growth of epithelial and stromal cells outside the uterine cavity. It has a complex etiology and affects ∼10% of reproductive age women. It is accompanied by a chronic inflammatory response with substantial evidence to indicate genetic susceptibility. The causal genes and their pathways leading to endometriosis, however, are still unknown. Recently, genomewide association studies on endometriosis identified 14 genomic risk loci in women of European and Japanese ancestry. It is becoming increasingly clear that these risk regions are intergenic and thus contribute to disease susceptibility through regulatory mechanisms, most likely mediated through regulation of genes within a restricted distance from the risk variants. One endometriosis risk locus has been detected at chromosome 2q13 within an inflammatory-rich region of gene transcripts and thus may play a role in the inflammation component of the disease. We carried out detailed analysis of the genomic region 250 kb on either side of sentinel SNP rs10167914 and identified 21 transcripts which contained 6 interleukin (IL)-1 family genes, 3 previously reported coding genes that have a relationship to inflammation, 4 novel coding, or pseudogenes, and 8 noncoding RNA transcripts. Through an extensive literature search, we examined the roles these genes and their resultant proteins play in endometriosis pathogenesis. The results suggest alteration in the expression the IL-1 family transcripts either alone or as a complex milieu could have a significant influence on endometriosis and should be prioritized for future study on the implications of inflammation on endometriotic lesions.

An in vitro investigation of telocytes-educated macrophages: morphology, heterocellular junctions, apoptosis and invasion analysis

BACKGROUND

Telocytes (TCs), a recently discovered novel type of interstitial cells, were also found in a wide variety of human and mammalian reproductive organs/tissues, including uterus, oviduct and placenta. Previously, we demonstrated that TCs-conditioned media was capable of activating peritoneal macrophages (pMACs) through paracrine effects. This study investigates the hypothesis that direct interaction of TCs with pMACs will also play a significant role in immunoregulation of pMACs.

METHODS

TCs and pMACs were derived from the uterus and intraperitoneal cavity of female BALB/c mice, respectively. TCs were identified by immunofluorescence and then co-cultured directly with pMACs for 24 h without added cytokines, to observe the in vitro biological behavior of pMACs. We used histochemical staining to study morphology and mitochondrial metabolism of pMACs, scanning electron microscopy to study heterocellular junctions, flow cytometry to investigate mitochondrial membrane potential (ΔΨm) and apoptosis, and transwell chambers to study invasion ability. Student-t test was used accordingly.

RESULTS

Presently, TCs with typical structure and immunophenotype of double CD-34-positive/vimentin-positive were successfully isolated. pMACs co-cultured with TCs showed obviously morphological activation, with enhanced energy metabolism (P < 0.05). Meanwhile, direct physical cell-to-cell interaction promoted the development of heterocellular junctions between TCs and pMACs. Furthermore, TCs treatment markedly reduced the depletion of ΔΨm in co-cultured pMACs (all P < 0.05), and inhibited their apoptosis (P < 0.05). Functionally, pMACs co-cultured with TCs showed enhanced invasion ability (P < 0.05).

CONCLUSIONS

Direct physical cell-to-cell interaction promoted the development of heterocellular junctions between TCs and pMACs, presumably responsible for the observed novel efficient way of pMACs activation via mitochondrial signaling pathway. TCs-educated pMACs might be a promising way to restore the defective immunosurveillance in endometriosis (EMs), led to the enhanced treatment efficacy of EMs in a simple and clinically feasible fashion.

Recently discovered interstitial cells "telocytes" as players in the pathogenesis of uterine leiomyomas

Uterine telocytes are interstitial cells characterized by a very long cytoplasmic prolongations, which form a 3D network, functionally integrating a wide variety of different cells. Leiomyomas (uterine fibroids) are benign tumors, which pose a huge threat concerning various health problems in women affected by this condition. The exact cause of leiomyomas development is, however, still largely unknown. Therefore, in an attempt to clarify their etiology, we performed an immunohistochemical characterization of telocytes in leiomyomas as well as in normal myometrium. Tissue samples of intramural leiomyomas from 26 women (age 46.26 ± 11.07) were immunohistochemically stained for the expression of c-kit (CD117) antigen, one of the markers of telocytes. C-kit (CD117) antigen is useful for a routine immunohistochemical identification of uterine telocytes in histological sections of myometrium. In normal, healthy myometrium the c-kit positive telocytes occupy approximately 2.2% of the area of a tissue slide, contrasting with no detectable c-kit positive cells within leiomyomas. As telocytes are thought to be key players in the regulation of tissue homoeostasis, our data suggest that uterine telocyte loss may have important implications in the pathogenesis of leiomyomas. In addition, we supposed to summarize three hypotheses on the association of the cells telocytes loss within the myometrium and formation of leiomyomas. These hypotheses include the loss of telocytes' functions as "sex hormone sensors" and regulators of smooth muscle cells cycle; the role of telocytes as progenitor cells for the development of leiomyomas; and the hypothesis of decreased angiogenesis after telocytes' loss with subsequent hypoxia (as a key factor for leiomyomas development).

Biliary Polyunsaturated Fatty Acids and Telocytes in Gallstone Disease

It has been reported that intake of ω-3 polyunsaturated fatty acids (PUFAs) reduces the risk of coronary heart disease. It also influences bile composition, decreasing biliary cholesterol saturation in the bile of patients with gallstones. In addition to bile composition disturbances, gallbladder hypomotility must be a cofactor in the pathogenesis of cholelithiasis, as it leads to the prolonged nucleation phase. Our current knowledge about gallbladder motility has been enhanced by the study of a population of newly described interstitial (stromal) cells-telocytes (TCs). The purpose of this study was to determine whether TC loss, reported by our team recently, might be related to bile lithogenicity, expressed as cholesterol saturation index or the difference in biliary PUFA profiles in patients who suffer from cholecystolithiasis and those not affected by this disease. We determined biliary lipid composition including the fatty acid composition of the phospholipid species in bile. Thus, we investigated whether differences in biliary fatty acid profiles (ω-3 PUFA and ω-6 PUFA) in gallbladder bile may influence its lithogenicity and the quantity of TCs within the gallbladder wall. We conclude that the altered PUFA concentrations in the gallbladder bile, with elevation of ω-6 PUFA, constitute important factors influencing TC density in the gallbladder wall, being one of the possible pathophysiological components for the gallstone disease development. This study established that altered bile composition in patients with cholelithiasis may influence TC quantity within the gallbladder muscle, and we concluded that reduction in TC number may be a consequence of the supersaturated bile toxicity, while some other bile components (ω-3 PUFA, glycocholic, and taurocholic acids) may exert protective effects on TC and thus possibly influence the mechanisms regulating gallbladder and extrahepatic bile duct motility. Thus, ω-3 PUFA may represent a possible option to prevent formation of cholesterol gallstones.