Enrichment of cardiac ECM proteins. (A) Our previously published 3-step ECM extraction method for cardiac tissue is based on decellularization and ensures enrichment and detection of ECM proteins. The image shows a decellularized heart after prolonged SDS perfusion. The ECM is solubilized by GuHCl and analysed using proteomics. (B) Smaller species display higher levels of cardiac cellularity as measured by the ratio of 3 members of different ECM protein classes and the cardiac-specific troponin T (TNNT2, y-axis). (C) Proteins identified in murine hearts using the Texas 3-step66 extraction method compared to those identified by our previously published method (see Drozdov et al.61). Most proteins are identified by both methods. Unlike the Texas 3-step method, our ‘English Quickstep’ method did not include an analysis of the remaining pellet after GuHCl extraction.