Electron microscopy study of left ventricular cardiomyocytes in adult rats born preterm

BACKGROUND: Preterm birth is a risk factor for the early development of cardiovascular diseases. To date, based on the results of clinical studies, it is impossible to get a notion of the ultrastructural features of cardiomyocytes in adolescents and adults born prematurely. In this regard, it is relevant to conduct an experiment aimed at studying the effect of preterm birth on the ultrastructure of cardiomyocytes in the late postnatal period of ontogenesis. AIM: to study the ultrastructure of left ventricular cardiomyocytes in 24-hour premature rats on the 180th day of the postnatal period of ontogenesis. METHODS: The study was conducted on full-term (n=4, pregnancy duration 22 days) and preterm (n=4, pregnancy duration 21 days) male Wistar rats. Preterm labor was induced by mifepristone injection to pregnant rats. Preterm and full-term offspring were removed from the experiment on the 180th day of the postnatal period of ontogenesis. Fragments of the left ventricle of the heart of preterm and full-term rats were used for ultrastructural studies of cardiomyocytes (transmission electron microscopy). Electron microphotographs of longitudinal sections of contractile cardiomyocytes used to determination of the relative areas of the nucleus, cytoplasm, myofibrils, and mitochondria. RESULTS: The structure of cardiomyocytes of preterm and full-term rats on the 180th day of the postnatal period is fundamentally similar. However, the relative area of the nuclei of cardiomyocytes in preterm rats is lower, and the relative area of the cytoplasm is higher than in full-term animals. Exclusively in the cytoplasm of preterm rats, perinuclear swelling of the cytoplasm, thinning of myofibrils, as well as signs of mitochondrial damage or dysfunction, such as destruction of mitochondrial membranes, concentric organization of mitochondrial cristae, dissociation of mitochondrial clusters, are observed. CONCLUSION: Preterm birth has long-lasting effects on cardiomyocyte ultrastructure. The observed ultrastructural changes indicate a disturbance in energy production in the cardiomyocytes of preterm rats in the late postnatal period of ontogenesis.