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 a n important factor in prognosis. The healing process, involving change s in type I and III collagens, is one of the major factors in remodell ing. We therefore examined sequential changes in type I and III collag ens after experimental myocardial infarction. Materials and methods: H earts were excised from 1 day to 10 weeks after permanent left coronar y ligation in rats. Immunohistochemical staining with a polyclonal ant ibody to each collagen was performed by the avidin-biotin-peroxidase m ethod. Results: Type I collagen initially appeared in the peripheral z one of the infarct from 3 days after ligation, the extent of staining gradually increasing until it reached a maximal level on days 21-28, a fter which the distribution remained unchanged. Type III collagen appe ared in the peripheral zone of the infarct from 3 days after ligation; the extent of staining reached the maximal level after 11-28 days, af ter 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 re latively late phase. Type III collagen, however, contributed particula rly to collagen matrix formation in the relatively early phase. This s tudy improves current understanding of the time-dependent alterations in type I and III collagens involved in the healing process after coro nary artery occlusion.