Changes in extracellular collagen matrix alter myocardial systolic performance

The purpose of this study was to test the hypothesis that acute disruption of fibrillar collagen will decrease myocardial systolic performance without changing cardiomyocyte contractility. Isolated papillary muscles were treated either with plasmin (0.64 U/ml, 240 min) or untreated and served as same animal control. Plasmin treatment caused matrix metalloproteinase activation and collagen degradation as measured by gelatin zymography, hydroxyproline assays, and scanning electron microscopy. Plasmin caused a significant decrease in myocardial systolic performance. Isotonic shortening extent and isometric developed tension decreased from 0.17 +/- 0.01 muscle length (ML) and 45 +/- 4 mN/mm(2) in untreated muscles to 0.09 +/- 0.01 ML and 36 +/- 3 mN/mm(2) in treated muscles (P < 0.05). However, plasmin treatment (0.64 U/ml, 240 min) did not alter shortening extent or velocity in isolated cardiomyocytes. Acute disruption of the fibrillar collagen network caused a decrease in myocardial systolic performance without changing cardiomyocyte contractility. These data support the hypothesis that fibrillar collagen facilitates transduction of cardiomyocyte contraction into myocardial force development and helps to maintain normal myocardial systolic performance.