Congenital heart defects are present in 8 of 1000 newborns and palliative surgical therapy has increased survival. Despite improved outcomes, many children develop reduced cardiac function and heart failure requiring transplantation. Human cardiac progenitor cell (hCPC) therapy has potential to repair the pediatric myocardium through release of reparative factors, but therapy suffers from limited hCPC retention and functionality. Decellularized cardiac extracellular matrix hydrogel (cECM) improves heart function in animals, and human trials are ongoing. In the present study, a 3D bioprinted patch containing cECM for delivery of pediatric hCPCs is developed. Cardiac patches are printed with bioinks composed of cECM, hCPCs, and gelatin methacrylate (GelMA). GelMA-cECM bioinks print uniformly with a homogeneous distribution of cECM and hCPCs. hCPCs maintain >75% viability and incorporation of cECM within patches results in a 30-fold increase in cardiogenic gene expression of hCPCs compared to hCPCs grown in pure GelMA patches. Conditioned media from GelMA-cECM patches show increased angiogenic potential (>2-fold) over GelMA alone as seen by improved endothelial cell tube formation. Finally, patches are retained on rat hearts and show vascularization over 14 days in vivo. This work shows the successful bioprinting and implementation of cECM-hCPC patches for potential use in repairing damaged myocardium.

Congenital heart disease is the number one cause of birth defect-related death because it often leads to right ventricular heart failure (RVHF). One promising avenue to combat this RVHF is the use of cardiac patches composed of stem cells and scaffolds. Herein, we demonstrate a reparative cardiac patch by combining neonatal or child c-kit+  progenitor cells (CPCs) with a scaffold composed of electrospun polycaprolactone nanofibers. We examined different parameters of the patch, including the alignment, composition, and surface properties of the nanofibers, as well as the age of the CPCs. The patch based on uniaxially aligned nanofibers successfully aligned the CPCs. With the inclusion of gelatin in the nanofiber matrix and/or coating of fibronectin on the surface of the nanofibers, the metabolism of both neonatal and child CPCs was generally enhanced. The conditioned media collected from both patches based on aligned and random nanofibers could reduce the fibrotic gene expression in rat cardiac fibroblasts, following stimulation with transforming growth factor β. Furthermore, the conditioned media collected from the nanofiber-based patches could lead to the formation of tubes of human umbilical vein endothelial cells, indicating the pro-angiogenic capability of the patch. Taken together, the electrospun nanofiber-based patches are a suitable delivery vehicle for CPCs and can confer reparative benefit through anti-fibrotic and pro-angiogenic paracrine signaling.

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