Reperfusion accelerates the distribution of type I and III collagen messenger RNA expression after acute myocardial infarction: in situ hybridization in experimental infarction in rats.

BACKGROUND

The effects of reperfusion on the time-dependent appearance and distribution of type I and III collagen messenger RNA (mRNA) expression had not hitherto been examined.

OBJECTIVE

To compare the sequential changes in the extent of distribution of type I and III collagen mRNA expression in reperfused infarct hearts of rats with those in unreperfused infarct hearts.

METHODS

Using an experimental rat model of infarction, we examined type I and III collagen mRNA expression with specific rat pro alpha 1 (I) and human pro alpha 1 (III) collagen riboprobes by in-situ hybridization. Reperfusion was established after a 2 h coronary ligation that produced complete necrosis of the myocytes.

RESULTS

Positive signals both for alpha 1 (I) and for alpha 1 (III) collagen mRNA appeared in the infarct peripheral zone 12 h after coronary ligation both of the reperfused and of unreperfused hearts. The spread of signal into the infarct central zone occurred 1-2 days earlier for the reperfused hearts than it did for the unreperfused hearts. The difference between the distributions of signals for the reperfused and unreperfused hearts became obscure on day 14. No notable difference between the extents of signal distribution for alpha 1 (I) and alpha 1 (III) collagen mRNA was obtained. We observed intense signals from spindle-shaped mesenchymal cells (myofibroblasts and fibroblasts) located between surviving myocytes in the marginal zone of the infarct. No myocyte exhibited signals both for alpha 1 (I) and for alpha 1 (III) collagen mRNA.

CONCLUSION

In the present study, using in-situ hybridization, we demonstrated that reperfusion accelerates the distribution of expression both of alpha 1 (I) and of alpha 1 (III) collagen mRNA in the infarct zone after acute myocardial infarction in rats.