Abstract
BACKGROUND: Preterm birth is a risk factor for the early development of cardiovascular diseases. Thus far, based on the results of clinical studies, the ultrastructural features of cardiomyocytes in adolescents and adults born prematurely can be identified. Thus, experiments aimed at studying the effects of preterm birth on the ultrastructure of cardiomyocytes in the late postnatal period of ontogenesis are relevant. AIM: To identify the ultrastructural features of left ventricular cardiomyocytes in preterm adult rats. MATERIALS AND 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 day 180 of the postnatal period of ontogenesis. Fragments of the left ventricle of the heart of preterm and full-term rats were used for the ultrastructural studies of the cardiomyocytes (electron transmission microscopy). Electron microphotographs of longitudinal sections of contractile cardiomyocytes were used to determine the relative areas of the nucleus, cytoplasm, myofibrils, and mitochondria. RESULTS: The structure of the cardiomyocytes of preterm and full-term rats on postnatal day 180 was fundamentally similar. However, the relative area of the nuclei of cardiomyocytes in preterm rats was lower (p=0.02), and the relative area of the cytoplasm was higher (p=0.02) than that in full-term animals. Exclusively, in the cytoplasm of preterm rats, perinuclear swelling of the cytoplasm, thinning of myofibrils, and signs of mitochondrial damage, such as destruction of mitochondrial membranes, concentric organization of mitochondrial cristae, and dissociation of mitochondrial clusters, were observed. CONCLUSION: Preterm birth has chronic negative effects on the ultrastructure of cardiomyocytes. The observed ultrastructural changes lead to the disruption of energy production in the cardiomyocytes in the late postnatal period of ontogenesis of preterm rats.
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