Differential expression of alpha 1, alpha 3 and alpha 5 integrin subunits in acute and chronic stages of myocardial infarction in rats

Objective: Anchoring cardiac myocytes to extracellular matrix, which is med iated mainly by integrins on their surfaces, is important for maintaining t he architecture of myocardial tissues and transmitting mechanical force. We evaluated the expression of alpha integrin subunits on myocytes and the ac cumulation of interstitial collagen and fibronectin at acute and chronic st ages after myocardial infarction. Methods: Myocardial infarction was induce d by ligation of left coronary arteries in rats. The expression of alpha 1, alpha 3 and alpha 5 integrin subunits, and accumulation of collagen and fi bronectin were analyzed with immunohistochemistry or sirius-red staining. R esults: In hearts without infarction, moderate expression of the alpha 3 su bunit and only slight expression of the alpha 5 subunit were observed on my ocytes. In the first week after infarction, the alpha 1 subunit, collagen a nd fibronectin were increased only in the peri-infarcted area, while the al pha 5 subunit was increased both in peri-infarcted and non-infarcted areas. At day 42, the expression of the alpha 1 subunit and collagen were still i ncreased, although the alpha 5 subunit and fibronectin were decreased. The expression of the alpha 3 subunit was not altered throughout the experiment al period. Conclusion: These data suggest that integrin subunits play an im portant role in healing and remodeling processes after myocardial infarctio n. (C) 1999 Elsevier Science B.V. All rights reserved.