Ultrastructural Characteristics of Placental Telocytes

Distribution and morphologic characterization of telocytes in rat ovary and uterus: insights from ultrastructural and immunohistochemical analysis

Telocytes (TCs) are characterized by a small oval-shaped cell body with long prolongations that are called telopods (Tps). PDGFR-β and c-kit markers may assist for the immunohistochemical identification of TCs; however, by these means they cannot be identified with absolute specificity. Transmission electron microscopy (TEM) is considered as a gold standard method for TCs observation. Studies on TCs in the female reproductive system are limited, and there is a lack of awareness regarding TCs in rat ovaries. We aimed to demonstrate the existence and morphology of TCs in rat ovaries, alongside previously studied TCs in rat uteri. Thus, ovaries and uteri from young adult Sprague-Dawley female rats (n = 8) with regular estrous cycles were collected. Then, left ovaries and uteri were proccessed for TEM analysis, while the right ones were used for immunohistochemistry. As a result, TCs were seen throughout the rat's ovarian stroma with their characteristic cell bodies, Tps, podomes (Pds) and podomers (Pdms). Tps were situated within the thecal layer of the follicles, surrounding the corpus luteum and blood vessels. Ovarian TCs were recognized to have relationship with other TCs/stromal cells. Subsequently, TCs were seen in stroma of endometrium with surrounding blood vessels and uterine glands, myometrium and perimetrium in rat uteri. There was also no statistical significance between the number of c-kit+ and PDGFR-β+ telocyte-like cells in both rat ovarian (p = 0.137) and endometrial stroma (p = 0.450). Further investigation of the roles and functions of TCs in the female reproductive system is needed.

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.

Telocytes in the Myocardium of Children with Congenital Heart Disease Tetralogy of Fallot

Telocytes, a new type of interstitial stem cells with long thin processes that form a three-dimensional network around cardiomyocytes, vessels, and nerve fibers were described in the myocardium of children with tetralogy of Fallot. Two types of morphologically different telocytes, spindle-shaped and rounded, were identified. Contacts of telocytes with stem cells and interstitial macrophages were found. Telocytes were more common in the immature myocardium, where the assembly of myofibrils in cardiomyocytes was not completed and small Ki-67⁺ cardiomyocyte progenitor cells were present. Telocytes expressed immunohistochemical markers CD117, vimentin, CD34, and CD44. Localization and ultrastructural characteristics of telocytes suggested their participation in stem cell differentiation, coordination of neoangiogenesis, and paracrine regulation of all components of the interstitium.

Ultrastructural and Immunohistochemical Features of Telocytes in Placental Villi in Preeclampsia

A new cell type, interstitial Cajal-like cell (ICLC), was recently described in different organs. The name was recently changed to telocytes (TCs), and their typical thin, long processes have been named telopodes (Tp). TCs regulate the contractile activity of smooth muscle cells and play a role in regulating vessel contractions. Although the placenta is not an innervated organ, we believe that TCs are present in the placenta. We studied placenta samples from physiological pregnancies and in different variants of preeclampsia (PE). We examined these samples using light microscopy of semi-thin sections, transmission electron microscopy, and immunohistochemistry. Immunohistochemical examination was performed with primary antibodies to CD34, CD117, SMA, and vimentin, and TMEM16a (DOG-1), the latter was used for the diagnosis of gastrointestinal stromal tumours (GIST) consisting of TCs. We have identified a heterogenetic population of ТСs in term placentas, as these cell types differed in their localization, immunophenotype and ultrastructural characteristics. We assume TMEM16a could be used as the marker for identification of TCs. In PE we have revealed telocyte-like cells with ultrastructural signs of fibrocytes (significant process thickening and the granular endoplasmic reticulum content was increased) and a loss of TMEM16a immunohistochemical staining.