Increased expression of connective tissue growth factor in the infarct zone of experimentally induced myocardial infarction in rats

Connective tissue growth factor (CTGF), a 36- to 38-kDa peptide, is selecti vely induced by transforming growth factor-beta and has been suggested to c ontribute to tissue repair. To test the hypothesis that CTGF is expressed i n myocardial infarct tissue following acute myocardial infarction (AMI), we examined CTGF expression after AMI was experimentally induced in rats. Myo cardial infarction was induced by left coronary artery ligation in male Spr ague-Dawley rats. Northern blotting demonstrated that the CTGF mRNA express ion on days 2, 7 and 14 was increased by 6-, 23- and 8-fold, respectively, compared to that in the pre-ligation hearts. In situ hybridization revealed CTGF mRNA signals on day 2 in myocytes in the infarct marginal zone and sp indle-shaped mesenchymal cells (presumably myofibroblasts and fibroblasts) located between surviving myocytes in the infarct peripheral zone. On day 7 , the signals were observed in the inner lesion of the infarct around infar ct granulation tissue. Western blotting demonstrated that the CTGF protein expression on days 2, 7 and 14 was increased compared to the pre-ligation h earts. Immunopositive staining for CTGF was observed in the inner lesion of the infarct tissue on day 7. In conclusion, the findings demonstrated the increased expression of: CTGF in the infarct tissue. Myocytes in the infarc t marginal zone and spindle-shaped mesenchymal cells (presumably myofibrobl asts and fibroblasts) were the cells responsible for CTGF production. (C) 1 998 Academic Press.