SEQUENTIAL-CHANGES IN THE DISTRIBUTION OF TYPE-I AND TYPE-III COLLAGENS IN THE INFARCT ZONE - IMMUNOHISTOCHEMICAL STUDY OF EXPERIMENTAL MYOCARDIAL-INFARCTION IN THE RAT

Aim: Ventricular remodeling following acute myocardial infarction is an important factor in prognosis. The healing process, involving changes in type I and III collagens, is one of the major factors in remodelling. We therefore examined sequential changes in type I and III collagens after experimental myocardial infarction. Materials and methods: Hearts were excised from 1 day to 10 weeks after permanent left coronary ligation in rats. Immunohistochemical staining with a polyclonal antibody to each collagen was performed by the avidin-biotin-peroxidase method. Results: Type I collagen initially appeared in the peripheral zone of the infarct from 3 days after ligation, the extent of staining gradually increasing until it reached a maximal level on days 21-28, after which the distribution remained unchanged. Type III collagen appeared in the peripheral zone of the infarct from 3 days after ligation; the extent of staining reached the maximal level after 11-28 days, after which a slight decrease in the distribution was observed, although the staining did not entirely disappear. Conclusions: Type I collagen was a major factor in collagen matrix formation, especially in the relatively late phase. Type III collagen, however, contributed particularly to collagen matrix formation in the relatively early phase. This study improves current understanding of the time-dependent alterations in type I and III collagens involved in the healing process after coronary artery occlusion.