Abstract 19973: Decellularized Extracellular Matrix Exhibits Reduced Stiffness and Immature Collagen Deposition in a Mouse Model of Left Heart Failure

Abstract

The extracellular matrix (ECM) is a major determinant of myocardial mechanics in heart failure. Existing methods to evaluate ECM composition are limited. Our objective was to perform a non-destructive microstructural and mechanical analysis of de-cellularized ECM in a mouse model of left ventricular (LV) failure.Methods and Results: Wild-type mice were subjected to 8 weeks of trans-aortic constriction (TAC; n=6) and compared to sham operated controls (Sham; n=5). Compared to sham, TAC mice had increased LV and lung weights, increased LV end-diastolic pressure (4±2 vs 25±5 mmHg, p<0.01) and reduced dP/dT (8249±596 vs 4786±984 mmHg/sec, p<0.01). LV collagen abundance by picrosirius red staining was higher in TAC mice (1±0.1 vs 35±12%, p<0.05) and Type I collagen mRNA and protein levels were increased by 80-fold and 2-fold, respectively (p<0.05 for both). Using non-linear optical microscopy, collagen fiber organization, content and cross-linking were quantified from decellularized sections of the LV free wall. Using cumulative second harmonic generation (SHG), a trend to higher total collagen content per tissue volume was observed in TAC mice (0.02±0.01 vs 0.05±0.3, p=0.09). Two photon excited fluorescence within SHG positive voxels was used to measure cross-linking per collagen fiber. Compared to sham, reduced cross-linking was observed in TAC mice (0.2 ±0.1 vs. 0.11±0.04, p=0.02). Next, using tensile mechanical testing no difference in average ECM stiffness (elastic modulus) was observed between groups (31±15 vs 24±7, sham vs TAC, p=0.19). Conclusions: This is the first mechanical analysis of decellularized ECM in a murine model of LV failure. Despite increased Type I collagen mRNA, protein and histologic fibrosis after TAC, the ECM composition analysis showed reduced collagen cross-linking suggestive of functionally immature collagen deposition. Functional maturation of the ECM may be an important target of therapy for heart failure.