Immunohistochemical characterization of telocytes in ratuterus in different reproductive states

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.

Role of Uterine Telocytes During Pregnancy

Endometrial remolding and angiogenesis are critical events that occur during pregnancy in order to establish uteroplacental vascular communication. This study investigated the role of uterine telocytes (TCs) in pregnancy. We analyzed the distribution of TCs and morphological changes in the endometrium of the gravid rabbit uterus at different stages of pregnancy: after ovulation, pre-implantation (day 7), post-implantation (days 8 and 9), and mid-pregnancy (day 14) and late (days 21–28) pregnancy. TCs gradually increased with the progression of pregnancy. They had distinctive telopodes (TPs) and podoms, with intranucleolar chromatin. The TCs established contact with decidual cells, growing a glandular epithelium, blood vessels, and immune cells, such as lymphocytes, neutrophils, and macrophages. The TCs underwent morphological changes at the post-implantation phase. They acquired thick and voluminous TPs, formed an extensive three-dimensional (3D) labyrinth at mid-pregnancy, and exhibited irregular-shaped nuclei and a dilated rough endoplasmic reticulum at late pregnancy. They also acquired a convoluted contour-formed complex network. Scanning electron microscopy (SEM) showed an extensive 3D network in the endometrium, forming a condensed sheath at late pregnancy. Transmission electron microscopy and SEM detected fenestrated TPs, and TCs were identified by CD34 and vascular endothelial growth factor expression. TCs also expressed matrix metalloproteinase-9 and transforming growth factor beta-1. Results suggested that TCs might play an essential role in maternal placenta formation, especially decidualization, regulation of uterine gland development, and neovascularization of maternal uterine blood vessels.

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).

Telocytes in the Female Reproductive System: Up-to-Date Knowledge, Challenges and Possible Clinical Applications

From their initial description in 2005 to this day, telocytes (TCs) have been described in the ovary, uterine tubes, uterus, vagina, mammary gland, and placenta. Their morphological features, immunophenotype, physiological functions, and roles in disease have been thoroughly documented in both animal models and human subjects. TCs, with their extremely long cytoplasmic processes called telopodes, play a pivotal role in the morphological and functional interconnection of all the components of the interstitial compartment, but also with constituents of the parenchyma. Although there is no specific immunohistochemical marker for their identification, the most cited are CD 117, CD 34, platelet-derived growth factor receptor (PDGFR), vimentin, and specific markers typical for the female reproductive system (FRS)—estrogen and progesterone receptors (ER and PR). This immunophenotype provides important clues to their physiological roles. Their main functions include the regulation of hormone-dependent processes, intercellular signaling, immune surveillance, microenvironmental maintenance, and the nursing of stem cells. In a situation where TCs are functionally or morphologically decimated, many disease entities may develop, including premature ovarian failure, endometriosis, ectopic pregnancy, infertility, preeclampsia, or even breast cancer. The common denominator of many of these conditions is that their etiopathogenesis is either partially known or completely obscure. Even though the exact role of TCs in these conditions is yet to be revealed, multiple lines of research indicate that their future clinical application may enrich diagnostic-therapeutic strategies of countless conditions. TCs are also heavily debated in terms of their possible use in regenerative medicine and tissue engineering. Some of the concepts related to TC research are strongly substantiated by experimental data, while others are highly speculative. Only future research endeavors will clearly distinguish dead-end lines of research from genuine contributions to the field.

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.

Distribution of estrogen receptor in the rabbit cervix during pregnancy with special reference to stromal elements: an immunohistochemical study

The estrogen plays a critical role during pregnancy through their receptors. Although the rabbit is one of the most important lab animal estrogen receptor alpha (ERA) localization on basic cells, newly discovered cells including telocyte and neuroendocrine cells, vascular compartments and interstitium during pregnancy not been described. At 0 day pregnancy, the most prominent immunoreactivity was moderate to ERA and observed on the ciliated cells, secretory cells, blood plasma, and interstitium. The smooth muscles and the endothelial cells showed mild immunoreactivity to ERA. Lymphocytes only exhibited strong immunoreactivity to ERA. At 7 days pregnancy moderate immunoreactivity to ERA observed on ciliated cells, secretory cells, smooth muscles, interstitium, and lymphocytes. Strong immunoreactivity to ERA detected on endothelial cells and blood plasma. At 14 days of pregnancy, the most prominent immunoreactivity was strong and detected on ciliated cells, smooth muscles, lymphocytes, and interstitium. Moderate immunoreactivity detected on endothelial cells and blood plasma. Secretory cells only exhibited mild immunoreactivity to ERA. At 21 days of pregnancy, the immunoreactivity to ERA ranged between mild on ciliated cells, smooth muscles, blood plasma and interstitium and negative on secretory cells, endothelial cells and lymphocytes. Our results indicated that the frequency and intensity of ERA immunostaining in the rabbit cervix varied on different structural compartments of the cervix during different pregnancy stages.

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).

Telocytes heterogeneity: From cellular morphology to functional evidence

Telocytes (TCs), located ubiquitously in the internal organs of vertebrates, are a heterogeneous, recently described, cell population of the stromal space. Characterized by lengthy cytoplasmic extensions that can reach tens of microns and are called telopodes (Tps), TCs are difficult to see using conventional microscopes. It was the electron microscopy which led to their first identification and Popescu's team the first responsible for the reconstructions indicating TCs 'organization' in a three-dimensional (3D) network that is believed to be accountable for the complex roles of TCs. Gradually, it became increasingly evident that TCs are difficult to characterize in terms of immunophenotype and that their phenotype is different depending on the location and needs of the tissue at one time. This review discusses the growing body of evidence accumulated since TCs were discovered and highlights how the complex interplay between TCs and stem cells might be of importance for tissue engineering and regenerative medicine.

Identification and potential role of telocytes in human uterine leiomyoma

Background

Telocytes are specialized interstitial tissue cell type. Our aim is to characterize telocytes in human uterine leiomyoma (ULM) and its adjacent myometrium (Myo-F) as well as normal myometrium (Myo-N).

Methods

ULMs and Myo-F tissues were taken from hysterectomy specimens done to treat symptomatic uterine fibroids (N = 20). Myo-N is isolated from hysterectomies done on ULM- free uteri for other benign indications (N = 15).

Telocytes were detected using immunohistochemistry to detect c-Kit (CD-117), as a surface marker expressed on telocytes, and electron microscopic examination to identify telocytes characteristic ultrastructure. Cellular count and electron microscopic features of telocytes in each of the studied tissues were compared.

Results

Telocytes could be detected in ULMs, Myo-F and Myo-N using c-KIT immunostaining. Electron microscopy confirmed the presence of telocytes in the three types of tissues identifying their characteristic features including small triangular or fusiform cell bodies with extensive cellular prolongations. ULM telocytes showed ultrastructural features suggestive of high cellular activities. Cell counts of ULM telocytes (3.35 ± 0.39) were significantly higher (P value = 0.00039) than that of Myo-F (1.39 ± 0.13). Myo-N (2.6 ± 0.36) contained higher telocyte numbers than Myo-F (1.39 ± 0.13), but the difference did not reach statistical significance (P value = 0.19).

Conclusions

Telocytes are detected in higher numbers and activity in ULMs than Myo-F or Myo-N. In ULMs, telocytes can work as a hormonal sensors for stem cells, provide scaffold for newly formed myocytes, or control important downstream signaling pathways.

Telocytes in female reproductive system (human and animal)

Telocytes (TCs) are a newly discovered type of cell with numerous functions. They have been found in a large variety of organs: heart (endo‐, myo‐, epi‐ and pericardium, myocardial sleeves, heart valves); digestive tract and annex glands (oesophagus, stomach, duodenum, jejunum, liver, gallbladder, salivary gland, exocrine pancreas); respiratory system (trachea and lungs); urinary system (kidney, renal pelvis, ureters, bladder, urethra); female reproductive system (uterus, Fallopian tube, placenta, mammary gland); vasculature (blood vessels, thoracic duct); serous membranes (mesentery and pleura); and other organs (skeletal muscle, meninges and choroid plexus, neuromuscular spindles, fascia lata, skin, eye, prostate, bone marrow). Likewise, TCs are widely distributed in vertebrates (fish, reptiles, birds, mammals, including human). This review summarizes particular features of TCs in the female reproductive system, emphasizing their involvement in physiological and pathophysiological processes.

Immunohistochemistry of Telocytes in the Uterus and Fallopian Tubes

The seminal work of Popescu and colleagues first demonstrated the existence of a new cell type - the telocytes. We were among the first who reported the presence of such cells in the female genital tract and performed TEM examinations, as well as immunohistochemical staining in the attempt to find a specific marker. Telocytes from rat and from the human uterus and from human fallopian tube were extensively investigated initially by comparison with interstitial cells of Cajal. Progress in telocyte research led to the identification of different subtypes suggestive for a heterogeneous telocyte population which can even coexist in the same location. As a consequence, the functions of TCs are still elusive and can be considered a versatile phenomenon that depends on a variety of conditions, including signal reception and transmission of information via extracellular vesicles or by direct intercellular contact.

Uterine Telocytes: A Review of Current Knowledge

Telocytes (TCs), a novel cell type, are briefly defined as interstitial cells with telopodes (Tps). However, a specific immunocytochemical marker has not yet been found; therefore, electron microscopy is currently the only accurate method for identifying TCs. TCs are considered to have a mesenchymal origin. Recently proteomic analysis, microarray-based gene expression analysis, and the micro-RNA signature clearly showed that TCs are different from fibroblasts, mesenchymal stem cells, and endothelial cells. The dynamics of Tps were also revealed, and some electrophysiological properties of TCs were described (such as membrane capacitance, input resistance, membrane resting potential, and absence of action potentials correlated with different ionic currents characteristics), which can be used to distinguish uterine TCs from smooth muscle cells (SMCs). Here, we briefly present the most recent findings on the characteristics of TCs and their functions in human pregnant and nonpregnant uteri.