Increase in the expression of biglycan mRNA expression Co-localized closely with that of type I collagen mRNA 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), specifically collagens. We hypothesized that biglycan messenger ribonucleic acid (mRNA) is increased in the myocardial infarct zone. Biglycan mRNA expression after acute myocardial infarction (AMI) in rats was determined with the use of Northern blotting and in situ hybridization, and its expression pattern was compared to that of type I collagen mRNA [alpha1(I) collagen]. The left coronary artery was ligated in male Sprague-Dawley rats, and the hearts were excised on days 2 and 7. The 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, respectively, compared to the sham-operated hearts. The in situ hybridization revealed intense signals for both biglycan and alpha1(I) collagen mRNA on day 2 in the spindle-shaped mesenchymal cells located between the surviving myocytes in the infarct peripheral zone. On day 7, biglycan mRNA signals were observed in the interior of the infarct around the infarct granulation tissue, a distribution that was essentially the same as that of alpha1(I) collagen. These results demonstrated that the increases in the infarct biglycan mRNA expression produced by mesenchymal cells (presumably myofibroblasts and fibroblasts) was closely co-localized with that of type I collagen mRNA, indicating that biglycan contributes to the infarct healing processes.