Immunohistochemical analysis of matrix metalloproteinase-9 and tissue inhibitor of matrix metalloproteinase-1 expression in the myocardium of rats in the early postnatal period on preterm birth modeling

Preterm birth shortens the duration of the prenatal period of development of the fetus and disrupts the natural morphogenesis of fetal organs. The study of tissue and cellular reactions in the myocardium of preterm born children is impossible due to the invasiveness of the procedure, therefore experimental studies are in demand. The aim of the study was to carry-out immunohistochemical analysis of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in the left ventricle myocardium of preterm rats from the 1st to the 14th day of the postnatal period. Material and methods. The objects of the study were the hearts of full-term (n=15) and preterm (n=15) male Wistar rats. Hearts were fixed in buffered (pH 7.4) 10% formalin solution. The material was embedded in paraffin. MMP-9 and TIMP-1 were detected on sections using the immunohistochemical indirect peroxidase method with antibodies. The intensity of the immunohistochemical reaction was assessed semi-quantitatively (in points). The obtained data were processed using nonparametric statistics methods. Results. No differences were found in the localization of MMP-9- and TIMP-1-positive staining in the myocardium of preterm and full-term animals. In preterm rats on the 7th day of the postnatal period, the intensity of staining for both MMP-9 and TIMP-1 was reduced. On the 14th day of the postnatal period in the myocardium of preterm rats an increase in the intensity of the immunohistochemical reaction to MMP-9 was observed against the background of a low-intensity reaction to TIMP-1. Conclusion. The results of the study indicate a possible increase in the effects of MMP-9 in the myocardium of preterm animals on the 14th day of the postnatal period. Imbalance of MMP-9 and TIMP-1 may contribute to left ventricular myocardial remodeling in preterm animals.