Abstract 368: Biomechanical Properties of Scar ECM: from the Acute to Chronic Stages of Myocardial Infarction

Introduction: Myocardial infarction (MI) affects more than 8 million Americans, causing massive heart cell death and heart function decrease. To better understand the scar biomechanics, we characterized the mechanical properties of pure scar ECM, obtained by decellularizing the MI tissues. Materials and Methods: Infarcted rat hearts were generated by a permanent left coronary artery ligation (PLCAL) and harvested at 15 min, 1, 2, and 4 weeks (per acute to chronic stages of MI)(N = 6 each). Scar ECM were obtained by decellularizing the infarcted hearts in 0.1% sodium dodecyl sulfate (SDS) solution for 3 weeks. Scar ECM specimens were trimmed into square shape, and then subjected to biaxial testing with one edge aligned with the circumferential direction and the other edge aligned with the longitudinal direction of the rat heart. After 10 cycle preconditioning, an equibiaxial tension protocol of T circ : T rad = 30:30 N/m was performed to capture the tissue biaxial behavior. Results and Discussion: Scar ECM 15 minutes through 4 weeks post infarction showed a stiffening biaxial behavior along with the time (Fig.1). The decrease of extensibility along longitudinal direction was more noticeable than circumferential direction, which led to a decrease in degree of anisotropy. Conclusions: Scar ECM biomechanics showed a stiffening behavior with a marked reduction in extensibility (longitudinal) with time. This change in biomechanical properties can be correlated to the collagen structure changes with progression of MI. Knowledge of the structural-mechanical relationship of scar ECM will help us understand MI progression and help formulate regenerative therapies.