Time course of collagen and decorin changes in rat cardiac and skeletal muscle post-MI

We examined the temporal relationship between messages (type I and type III mRNAs) for the principal fibrillar procollagens and subsequent collagen ac cretion, cross-linking, and decorin expression in the left ventricle (LV) p ostmyocardial infarction (post-MI). We sought to determine 1) what role the proteoglycan decorin plays in extracellular matrix (ECM) remodeling known to take place as a consequence of MI and 2) the extent skeletal muscle ECM is altered early post-MI. Therefore, after surgically induced production of small- to moderate-sized infarcts (similar to 20% of LV mass), extent and time course of ECM remodeling was evaluated in remaining viable LV free wal l and in slow- [soleus (SOL)] and fast-twitch [gastrocnemius (GAST)] skelet al muscles. Decorin, collagen, and hydroxylysylpyridinium cross-link concen trations and alpha1(I) (type I) and alpha1(III) (type III) procollagen mRNA s were measured in LVs from noninfarcted controls and at 72 h, 1, 2, 5, and 13 wk post-MI. These same data were collected in SOL and GAST muscles at a ll time points except 13 wk. Type I procollagen mRNA increased at both 72-h and 1-wk time points in LVs. Type III procollagen mRNA was elevated at 1 w k, returning to baseline by 2 wk post-MI. Collagen concentration was signif icantly increased by 1 wk, more than doubled by 5 wk, and was elevated 129% by 13 wk in the remaining viable LV. LV decorin expression was unaltered a t early time points, but increased 38% at 5 wk post-MI and doubled by 13 wk post-MI. In skeletal muscle, procollagen mRNAs were transiently altered in SOL and GAST muscles without any demonstrable effect on the measured ECM p arameters. This study reports, for the first time, the upregulation time co urse of decorin and its relationship to increased HP cross-linking and accu mulation of collagen in viable myocardium post-MI.