[Role of telocytes in the heart in health and diseases]

The Reaction of Myocardial Capillaries to Crystalloid Cardioplegia of Different Durations in Patients with Valvular Pathology and Coronary Heart Disease

The aim. To study the morphological manifestations of the response of the myocardial capillaries to cardioplegia in patients with valvular defects and coronary heart disease. Materials and methods. Morphological research of operative and sectional material was carried out. Myocardium fragments for microscopical study were obtained from patients at different stages of an open-heart surgery and patients who died at the stage of conservative treatment without surgical intervention. Similar samples of the myocardium of a healthy young man who died from injuries incompatible with life were studied as a control. For electron microscopy study, samples of myocardium were taken from patients at the 185th minute of perfusion. Results. Histological preparations of the myocardium showed pronounced diffuse hypertrophy of cardiomyocytes (CMCs), sometimes at the stage of decompensation (perinuclear edema, loss of myofibrils, apoptosis). This transformation of CMCs was obviously related to their functional overload caused by combined defects of the mitral and aortic valves. Changes in muscle fibers were accompanied by interstitial and perinuclear fibrosis. In the pool of coronary arteries affected by atherosclerosis, signs of small focal coronary fibrosis were visible, as well as rough post-infarction scars in 3 patients. All the patients had signs of acute hypoxic damage to the myocardium in the form of CMCs shortening and interstitial edema. Conclusions. In patients with combined defects of the aortic and mitral valves of the heart with coronary artery disease, the phenomena of myocardial fibrosis prevail. Heart valve disease combined with coronary heart disease lead to the development of both alterative and compensatory-adaptiveprocesses in the vessels of the microcirculatory bed. The greatest loss of vital organelles in small vessels is observed at 185 min after administration of cardioplegic solution, irreversible changes develop 3 h after perfusion.

Evaluation of the Plasticity of Novel Regulatory Cells-Telocytes-in the Gonad of the Male Chinese Soft-Shelled Turtle (Pelodiscus sinensis) Associated with Seasonal Reproductive Activity

Telocyte (TC)—a new type of interstitial cell with long telopodes, can form cellular junctions with various tissues or cells to participate in the regulation of multitudes of physiological activities and diseases. This study aimed to characterize the morphology, molecular features, and potential functions of hormone regulation in Chinese soft-shelled turtle (Pelodiscus sinensis) testis TCs at different reproductive stages by histological evaluation, immunohistochemistry (IHC), immunofluorescence (IF), and transmission electron microscopy. During hibernation, TCs were widely distributed in the interstitial tissue. In contrast, during reproductive activity, TCs were noted to be in close proximity with peritubular myoid cells surrounding the seminiferous tubule. Moreover, formed cell–cell junctions were observed between TCs and PTMs. The results of IHC and IF showed that the immunophenotype of testicular TCs in hibernating Chinese soft-shelled turtles is CD34+Vimentin−, while the reproductive telopodes (Tps) show low expression of vimentin. The androgen receptor is expressed in Tps of TCs of testis during hibernation. Our results showed also that TCs in seasonal breeding animals regulate the activity of neighboring cells by releasing extracellular microvesicles (EXMVs), thus influencing the activity of spermatogenesis and steroidogenesis. Consideration of our novel and interesting results indicate that the whole area warrants further research.

Telocytes and Atrial Fibrillation: From Basic Research to Clinical Practice

The emergence of new research methods makes it possible to study the tissue, structural, cellular, and molecular causes of atrial fibrillation (AF). Recently, the role of interstitial telocyte cells in the pathogenesis of AF has been actively discussed. Telocytes are a special type of interstitial cells identified in many organs and tissues, including the heart. The roles of telocytes in the myocardium are diverse: they have pacemaker activity, and carry out structural and coordination communication between cells. The ability of these cells to change the speed of the electrical pulse in the atrial and ventricular myocardium has been proven. Telocytes form "atypical" connections with almost all types of cells in the human heart, which collects them in an integrated network. Using electron microscopy, it was found that interstitial cells have different types of connections in the network and can integrate "information" from the vascular and nervous systems, interstitial, immune system, stem cells, progenitor cells, and contractile cardiomyocytes. Currently, the results of studies have been obtained that prove both positive and negative effects of telocytes on the occurrence of various diseases of the cardiovascular system. The role of telocytes in AF arrhythmogenesis remains a subject of discussion. The unique properties of telocytes in providing intercellular contacts, transmitting genetic information, and their ability to regenerate heart tissue are undoubtedly the most promising areas of modern cardiology. There is evidence of both direct and indirect effects of telocytes on the electrophysiological properties of the myocardium. There is no doubt that the development of this area opens up new therapeutic targets for the prevention and treatment of AF.

Myocardial Telocyte-Like Cells: A Review Including New Evidence

Telocytes (TCs) are a controversial cell type characterized by the presence of a particular kind of prolongations, known as telopodes, which are long, thin, and moniliform. A number of attempts has been made to establish the molecular phenotype of cardiac TCs (i.e., expression of c-kit, CD34, vimentin, PDGRFα, PDGRFβ, etc.). We designed an immunohistochemical study involving cardiac tissue samples obtained from 10 cadavers with the aim of determining whether there are TC-like interstitial cells that populate the interstitial space other than the mural microvascular cells. We applied the markers for CD31, CD34, PDGRFα, CD117/c-kit, and α-smooth muscle actin (α-SMA). We found that, in relation to two-dimensional cuts, the endothelial tubes could be misidentified as TC-like cells, the difference being the positive identification of endothelial lumina. Moreover, we found that cardiac pericytes express PDGRFα, CD117/c-kit, and α-SMA, and that they could also be misidentified as TCs when using light microscopy. We reviewed the respective values of the previously identified markers for achieving a clear-cut identification of cardiac TCs, highlighting the critical lack of specificity.