Morphological Evidence of Telocytes in Skeletal Muscle Interstitium of Exercised and Sedentary Rodents

Telocytes of the male reproductive system: dynamic tissue organizers

Telocytes are CD34+ interstitial cells that have long cytoplasmic projections (called telopodes), and have been detected in several organs, including those of the male reproductive system. In this brief review we evaluate the role of telocytes in tissue organization of the different organs of the male reproductive system in which these cells were studied. In general terms, telocytes act in the tissue organization through networks of telopodes that separate the epithelia from the stroma, as well as dividing the stroma into different compartments. In addition to this contribution to the structural integrity, there is direct and indirect evidence that such "walls" formed by telocytes also compartmentalize paracrine factors that they or other cells produce, which have a direct impact on morphogenesis and the maintenance of organ cell differentiation, as well as on their normal physiology. Moreover, alterations in telocytes and telopode networks are correlated with pathological conditions in the male reproductive system, in response to profound changes in structural organization of the organs, in inflammation, hyperplasia and cancer. Further studies are necessary to evaluate the molecular pathways telocytes employ in different contexts of physiology and disease.

Morphological identification and distribution comparison of telocytes in pituitary gland between normal and cryptorchid yaks

BACKGROUND

Telocytes (TCs) is a novel type of interstitial cells in many mammals organs, which participate in the organizational metabolism, mechanical support, immunomodulation and other aspects. The aim of this study was to explore the organizational chemical characteristics of TCs in pituitary gland and their changes in cryptorchid yaks.

METHODS

Transmission electron microscopy (TEM), toluidine blue staining, immunofluorescence, qRT-PCR, and Western blotting may enable us to understand TCs distribution characteristics and biological functions.

RESULT

TEM confirmed the presence of TCs in the pituitary gland with small bodies and moniliform telopodes (Tps). The Tps extending out from the cell body to the peri-sinusoidal vessels spaces, the number of Tps is closely related to the morphology of the nucleus. The most obvious changes of TCs in the pituitary gland of cryptorchid yaks is the Tps are relatively shorter and decreased secretory vesicles. H.E. and toluidine blue staining revealed that TCs not only distributed between the sinusoidal blood vessels and the glandular cell clusters, but also present on the surface of vascular endothelial cells. The co-expression of TCs biomarkers, such as Vimentin/CD34, CD117/CD34 and α-SMA/CD34, were evaluated by immunofluorescence to further determine the phenotypic characteristics of TCs. Besides, we analyzed the mRNA and protein expression of these biomarkers to determine the characteristics of TCs changes and possible biological roles. Both the mRNA and protein expression of CD117 were significantly higher in the pituitary gland of cryptorchid yaks than in the normal (p < 0.01), the protein expression of CD34 in the cryptorchid yaks was significantly higher than the normal (p < 0.01). There were no significant difference in mRNA expression of Vimentin and α-SMA (p>0.05), while the protein expression were significantly increased in the normal yaks (p < 0.05).

CONCLUSIONS

In summary, this study reports for the first time that the biological characteristics of TCs in yak pituitary gland. Although there is no significant change in the distribution characteristics, the changes in biological features of TCs in cryptorchid yaks are clear, suggesting that TCs participated in alteration in the local microenvironment of the pituitary gland. Therefore, our study provides clues for further investigating the role of TCs in the pituitary gland during the occurrence of cryptorchidism in yaks.

Morphological characteristics and distribution identification of telocytes in Tibetan sheep testis and epididymis

Telocytes (TCs) are a type of stromal cell discovered in the various organs of different animals and have many potential functions, including angiogenesis, signalling, and substance transport. However, the TCs have not been detected in the testis or epididymis of Tibetan sheep. This study investigated the position, characteristics, and distribution of TCs in the testis and epididymis of Tibetan sheep using transmission electron microscopy (TEM), toluidine blue staining, immunohistochemistry, and double immunofluorescence to elucidate their possible functions. TEM revealed that TCs were often found near basement membranes and capillaries and were characterised by large nuclei, elongated cytoplasmic protrusions, and many secretory vesicles. We also observed via toluidine staining that TCs were present near basement membrane and interstitial capillaries. Immunohistochemistry and double immunofluorescence revealed the positive expression of CD117, vimentin, platelet derived growth factor receptor α(PDGFRα), PDGFRα + CD117, and PDGFRα + vimentin in TCs. Additionally, we inferred that TCs participates in the formation of the blood-testis and blood-epididymis barriers, as well as in material transport and a stable microenvironment. This study presents the first evidence of the presence of TCs near the basement membrane and blood vessels in the testis and epididymis of Tibetan sheep. These findings provide new insights into the function of TCs in the reproductive systems of plateau animals.

The telocytes relationship with satellite cells: Extracellular vesicles mediate the myotendinous junction remodeling

The peripheral nerve injury (PNI) affects the morphology of the whole locomotor apparatus, which can reach the myotendinous junction (MTJ) interface. In the injury condition, the skeletal muscle satellite cells (SC) are triggered, activated, and proliferated to repair their structure, and in the MTJ, the telocytes (TC) are associated to support the interface with the need for remodeling; in that way, these cells can be associated with SC. The study aimed to describe the SC and TC relationship after PNI at the MTJ. Sixteen adult Wistar rats were divided into Control Group (C, n = 8) and PNI Group (PNI, n = 8), PNI was performed by the constriction of the sciatic nerve. The samples were processed for transmission electron microscopy and immunostaining analysis. In the C group was evidenced the arrangement of sarcoplasmic evaginations and invaginations, the support collagen layer with a TC inside it, and an SC through vesicles internally and externally to then. In the PNI group were observed the disarrangement of invaginations and evaginations and sarcomeres degradation at MTJ, as the disposition of telopodes adjacent and in contact to the SC with extracellular vesicles and exosomes in a characterized paracrine activity. These findings can determine a link between the TCs and the SCs at the MTJ remodeling. RESEARCH HIGHLIGHTS: Peripheral nerve injury promotes the myotendinous junction (MTJ) remodeling. The telocytes (TC) and the satellite cells (SC) are present at the myotendinous interface. TC mediated the SC activity at MTJ.

Advances in regenerative rehabilitation in the rehabilitation of musculoskeletal injuries

In the rapidly advancing field of regenerative medicine, relying solely on cell transplantation alone may be insufficient for achieving functional recovery, and rehabilitation before and after transplantation is crucial. Regenerative rehabilitation functions by synergizing the therapeutic effects of regeneration and rehabilitation to maximize tissue regeneration and patient function. We used the keywords "regenerative rehabilitation" to search across the database for published works; this review discusses the development of regenerative rehabilitation for the treatment of musculoskeletal injuries. Rehabilitation has become a crucial component of regenerative medicine because it can enhance patients' functional activity and facilitate their early return to society. Experimental data increasingly demonstrates that rehabilitation interventions support the regeneration of transplanted tissues.

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.

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.

Telocytes response to cardiac growth induced by resistance exercise training and endurance exercise training in adult male rats

Telocytes are interstitial cells found in different tissues, including cardiac stem cell niches. The purpose of this study was to investigate the response of the telocytes to the cardiac growth that occurs in response to resistance and endurance exercise trainings using rats distributed into control, endurance, and resistance training groups. Results revealed that the ratio of heart weight to body weight, cardiomycyte number, cardiomyocyte area, thickness of the left ventricular wall were significantly higher in the training groups compared to the control group. We observed increment in the cardiomyocytes surface area and thickness of the left ventricular wall in the resistance-training group than endurance-training group. We conclude that both resistance and endurance exercise trainings will lead to an increased number of cardiac telocytes, consequently, promote activity of the cardiac stem cells, and results in physiological cardiac growth, and this response does not seem to depend on the type of exercise.

Muscle-derived exosomes and exercise in cancer prevention

There are a lot of evidences on the beneficial effects mediated by exercise on the prevention of not communicable diseases (NCDs) including different type of cancer. The production of circulating exerkines transported in exosomes represents a novel pathway activated by exercise. However, the biological mechanisms that could explain the role of exosomes in cancer prevention have been not fully elucidated. The aim of this mini-review is to provide an update on the biological mechanisms bringing the release of muscle-derived exosomes during exercise and cancer prevention.

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.

Delimiting CD34+ Stromal Cells/Telocytes Are Resident Mesenchymal Cells That Participate in Neovessel Formation in Skin Kaposi Sarcoma

Kaposi sarcoma (KS) is an angioproliferative lesion in which two main KS cell sources are currently sustained: endothelial cells (ECs) and mesenchymal/stromal cells. Our objective is to establish the tissue location, characteristics and transdifferentiation steps to the KS cells of the latter. For this purpose, we studied specimens of 49 cases of cutaneous KS using immunochemistry and confocal and electron microscopy. The results showed that delimiting CD34+ stromal cells/Telocytes (CD34+SCs/TCs) in the external layer of the pre-existing blood vessels and around skin appendages form small convergent lumens, express markers for ECs of blood and lymphatic vessels, share ultrastructural characteristics with ECs and participate in the origin of two main types of neovessels, the evolution of which gives rise to lymphangiomatous or spindle-cell patterns-the substrate of the main KS histopathological variants. Intraluminal folds and pillars (papillae) are formed in the neovessels, which suggests they increase by vessel splitting (intussusceptive angiogenesis and intussusceptive lymphangiogenesis). In conclusion, delimiting CD34+SCs/TCs are mesenchymal/stromal cells that can transdifferentiate into KS ECs, participating in the formation of two types of neovessels. The subsequent growth of the latter involves intussusceptive mechanisms, originating several KS variants. These findings are of histogenic, clinical and therapeutic interest.

How Physical Activity Affects Knee Cartilage and a Standard Intervention Procedure for an Exercise Program: A Systematic Review

(1) Background: Cartilage degeneration with the natural aging process and the role of physical activity on cartilage wellness is still not clear. The objective of the present review was to understand how different physical activity interventions affect the cartilage and to propose a Standard Operating Procedure for an exercise program to maintain knee joint health; (2) Methods: Articles were collected on three different electronic databases and screened against the eligibility criteria. Results were collected in tables and the main outcomes were discussed narratively; (3) Results: A total of 24 studies have been included after the screening process and aerobic, strength, flexibility, postural balance, and mobility interventions were detected. Different protocols and types of interventions were adopted by the authors; (4) Conclusions: Physical activity interventions have mainly positive outcomes on cartilage structure, but the protocols adopted are different and various. A Standard Operating Procedure has been proposed for a physical intervention focalized on cartilage wellness that could be adopted as an intervention in the clinical setting. Furthermore, the creation of a standardized protocol wants to help scientific research to move in the same direction.

Myotendinous Junction: Exercise Protocols Can Positively Influence Their Development in Rats

The myotendinous junction (MTJ) is an interface that different stimuli alter their morphology. One of the main stimuli to promote alterations in the MTJ morphology is physical exercise. The present study aimed to investigate the morphology and molecular MTJ adaptations of biceps brachii muscle in adult Wistar rats submitted to different ladder-based protocols. Forty Wistar rats (90 days old) were divided into four groups: Sedentary (S), Climbing (C), Overload Climbing (OC), Climbing, and Overload Climbing (COC). The results of light microscopy demonstrated the cell and collagen tissue reorganization in the experimental groups. The sarcomeres lengths of different regions showed a particular development according to the specific protocols. The sarcoplasmic invaginations and evaginations demonstrated positive increases that promoted the myotendinous interface development. In the extracellular matrix, the structures presented an increase principally in the COC group. Finally, the immunofluorescence analysis showed the telocytes disposition adjacent to the MTJ region in all experimental groups, revealing their network organization. Thus, we concluded that the different protocols contributed to the morphological adaptations with beneficial effects in distinct ways of tissue and cellular development and can be used as a model for MTJ remodeling to future proteomic and genetic analysis.

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 inside of the peripheral nervous system - a 3D endoneurial network and putative role in cell communication

In this paper, we developed the hypothesis concerning the reasons to assimilate endoneurial fibroblast-like dendritic phenotype [shortly termed endoneurial dendritic cells (EDCs)] to the endoneurial telocytes (TCs). We reviewed the literature concerning EDCs status and report our observations on ultrastructure and some immune electron microscopic aspects of the cutaneous peripheral nerves. Our data demonstrate that EDCs long time considered as fibroblasts or fibroblast-like, with an ovoidal nucleus and one or more moniliform cell extensions [telopodes (Tps)], which perform homocellular junctions, also able to shed extracellular microvesicles can be assimilated to TC phenotype. Sometimes, small profiles of basement membrane accompany to some extent Tps. Altogether data resulted from scientific literature and our results strength the conclusion EDCs are really TCs inside of the peripheral nervous system. The inner three-dimensional (3D) network of endoneurial TCs by their homo- and heterocellular communications appears as a genuine cell-to-cell communication system inside of each peripheral nerve.