Neoinnervation and neovascularization of acellular pericardial-derived scaffolds in myocardial infarcts

Engineered bioimplants for cardiac repair require functional vascularization and innervation for proper integration with the surrounding myocardium. The aim of this work was to study nerve sprouting and neovascularization in an acellular pericardial-derived scaffold used as a myocardial bioimplant. To this end, 17 swine were submitted to a myocardial infarction followed by implantation of a decellularized human pericardial-derived scaffold. After 30 days, animals were sacrificed and hearts were analyzed with hematoxylin/eosin and Masson's and Gallego's modified trichrome staining. Immunohistochemistry was carried out to detect nerve fibers within the cardiac bioimplant by using βIII tubulin and S100 labeling. Isolectin B4, smooth muscle actin, CD31, von Willebrand factor, cardiac troponin I, and elastin antibodies were used to study scaffold vascularization. Transmission electron microscopy was performed to confirm the presence of vascular and nervous ultrastructures. Left ventricular ejection fraction (LVEF), cardiac output (CO), stroke volume, end-diastolic volume, end-systolic volume, end-diastolic wall mass, and infarct size were assessed by using magnetic resonance imaging (MRI). Newly formed nerve fibers composed of several amyelinated axons as the afferent nerve endings of the heart were identified by immunohistochemistry. Additionally, neovessel formation occurred spontaneously as small and large isolectin B4-positive blood vessels within the scaffold. In summary, this study demonstrates for the first time the neoformation of vessels and nerves in cell-free cardiac scaffolds applied over infarcted tissue. Moreover, MRI analysis showed a significant improvement in LVEF (P = 0.03) and CO (P = 0.01) and a 43 % decrease in infarct size (P = 0.007).