A Comparative Biomechanical Investigation of Porcine Neonatal and Adult Left Ventricular Tissues

Abstract

A current trend in cardiac muscle regeneration and repair is to recreate the biophysical and biomechanical environment of the neonatal hearts, which has been shown to promote cardiac regeneration. This translational need requires thorough understanding of the biomechanical properties of the neonatal hearts. In this study, we aim to (i) characterize the dynamic viscoelastic properties of the neonatal porcine left ventricular (LV) muscle and compare with the adult tissue behavior using a rheometer; (ii) perform histological assessment to identify the cellular and extracellular (ECM) microstructures that contribute to the observed biomechanical differences, and (iii) develop a light sheet imaging protocol to visualize the 3D ECM networks of both the neonatal and adult LV muscles. We found that the dynamic viscoelastic properties of the neonatal porcine LV muscle tissues were drastically different from the adult LV muscle tissues. The adult LV muscle tissues had much greater storage modulus (G’) and larger loss modulus (G”) than the neonatal LV muscle tissues in the range of frequency sweep. When compared with the adult LV, the histology of neonatal LV muscle showed less organized immature heart muscle fibers, a lower amount of collagen network, and a higher amount of proteoglycans, which were likely the underlying contributors of the unique viscoelastic properties of the neonatal heart muscles. Lastly, we have developed a tissue preparation and imaging protocol that was able to capture 3D ECM fiber orientation and alignment for both the neonatal and adult heart muscles.