MMP1 and familial dilated cardiomyopathy: Therefore, the aim of the present study was to investigate the associations between circulating markers of collagen deposition (PICP), collagen cross-linking (CITP:MMP-1), and histological collagen volume fraction (CVF) with cardiac function parameters, and to evaluate whether collagen cross-linking and degradation biomarkers further improve risk stratification in DCM patients.