INCREASE IN THE EXPRESSION OF BIGLYCAN MESSENGER-RNA EXPRESSION CO-LOCALIZED CLOSELY WITH THAT OF TYPE-I COLLAGEN MESSENGER-RNA IN THE INFARCT ZONE AFTER EXPERIMENTALLY-INDUCED MYOCARDIAL-INFARCTION IN RATS

Biglycan, a small dermatan sulphate proteoglycan, has been postulated to interact with other components of the extracellular matrix (ECM), s pecifically collagens. We hypothesized that biglycan messenger ribonuc leic acid (mRNA) is increased in the myocardial infarct zone. Biglycan mRNA expression after acute myocardial infarction (AMI) in rats was d etermined with the use of Northern blotting and in situ hybridization, and its expression pattern was compared to that of type I collagen mR NA [alpha(1)(I) collagen]. The left coronary artery was ligated in mal e Sprague-Dawley rats, and the hearts were excised on days 2 and 7, Th e Northern blot analysis demonstrated that expression of biglycan mRNA in the infarct on days 2 and 7 were 4.0- and 6.8-fold higher, respect ively, compared to the sham-operated hearts. The in situ hybridization revealed intense signals for both biglycan and alpha(1)(I) collagen m RNA on day 2 in the spindle-shaped mesenchymal cells located between t he surviving myocytes in the infarct peripheral zone. On day 7, biglyc an mRNA signals were observed in the interior of the infarct around th e infarct granulation tissue, a distribution that was essentially the same as that of alpha(1)(I) collagen. These results demonstrated that the increases in the infarct biglycan mRNA expression produced by mese nchymal cells (presumably myofibroblasts and fibroblasts) was closely co-localized with that of type I collagen mRNA, indicating that biglyc an contributes to the infarct healing processes. (C) 1998 Academic Pre ss