Time-dependent changes of decorin in the infarct zone after experimentallyinduced myocardial infarction in rats: Comparison with biglycan

Decorin, a small dermatan sulphate proteoglycan, has been postulated to int eract with other components of the extracellular matrix. We examined time-d ependent changes of decorin in the infarct zone after experimentally induce d myocardial infarction in rats by Northern blotting, in situ hybridization , and immunohistochemistry. The expression of decorin mRNA was compared to that of biglycan mRNA. Northern blotting demonstrated that the decorin mRNA expression was not increased in the infarct zone on day 2, while increased biglycan mRNA was observed at that time (average 3.1-fold increase). Decor in mRNA expression was increased on day 7, and reached a peak (average 2.2- fold increase) around day 14. Biglycan mRNA expression also reached a peak level around day 14 (average 13.3-fold increase). In situ hybridization rev ealed that mRNA signals for decorin did not appear in the infarct zone on d ay 2, while biglycan mRNA signals were observed. Decorin mRNA signals were observed in spindle-shaped mesenchymal cells in the infarct peripheral zone on day 7. The decorin mRNA signals appeared later than those of biglycan. Immunopositive staining for decorin was observed in the infarct zone on day 7. The present results demonstrated a time-dependent increase in decorin m RNA expression in mesenchymal cells in the infarct zone in rats. Decorin mR NA appeared later and was increased to a lower extent in the infarct zone t han biglycan mRNA.