Orientation and composition of collagen fibers within the scar after myocadial lesion in rat fetuses

This study was undertaken to examine orientation and composition of collagen fibers within the myocardial scar after mechanical injury in 16-day-old rat fetuses and in adult male rats. Measurements were performed from 7 to 40 days after lesion. Angles of fiber bundles relative to the longitudinal axis of wound channel were measured and were analyzed with circular statistic techniques. Proportion of collagen types I and III was determined when studying sections stained with picrosirius red under polarized light. In adult myocardium fibers of collagen type I were abundant and longitudinally aligned, the lesion developed into a mature scar. Fetal scar contained thinner fibers, which did not display a homogeneous distribution. This suggests that fetal scar is immature, its mechanical strength is less and that fetal myocardium shows incomplete repair.