Each year as cardiovascular disease continues to be one of the leading causes of death world wide, new treatment options are researched daily. For those whose cardiovascular disease progresses to end-stage heart failure, the gold standard remains transplantation. Those awaiting transplant however, far outweighs the available donor organs. One such potential to alleviate the donor shortage are decellularized cardiac scaffolds. These acellular scaffolds retain the native extracellular matrix and larger order branched vasculature. Retention of the native extracellular matrix creates an environment that is most optimal to support cell survival and differentiation. However, during the decellularization process the smaller microvasculature is mostly lost. The oxygen diffusion limitation in the body is around ~200 microns, and since the vast majority of tissues in the body are vascularized and accordingly need vascular supplies to remain viable, attention is turned to creating an environment that will increase the vascularization of said scaffolds. In order to increase said microvascular content, my dissertation study is focused on utilizing three angiogenic growth factors, Vascular endothelial growth factor A (VEGF-A), Platelet derived growth factor ?? and Angiopoietin 1 and creating a collagenous based system to deliver these growth factors to decellularized scaffolds and encourage vascular growth at a higher rate than would be seen otherwise. First, a model in vitro system was created to simulate the decellularized scaffold environment for testing the growth factor delivery system. This was done by using a 3D decellularized extracellular matrix hydrogel derived from porcine left ventricles, and cross- linked genipin. The gels were then characterized, and were seen to be able to support cell survival, proliferation, and even encourage trans-differentiation of human adipose derived stem cells towards a cardiac lineage. Then, research was focused on the testing of the growth factor release within a collagenous matrix. Release was found to mimic a pattern similar to in vivo angiogenesis over the course of 22 days. Analysis of angiogenic machinery, specifically the endothelial cell lumen formation complex, showed that critical lumen formation components were either upregulated or similar to controls, evidence that the presence of the growth factors do not aberrantly affect cellular behavior. Finally, endothelial cells were either seeded within the collagenous delivery system or on top of, that was then formed on top of the dECM hydrogels. Cells that had been encapsulated within the collagen invaded deeper into the dECM hydrogels faster than their control counterparts. The research done here provided the groundwork that this collagenous angiogenic growth factor delivery system may be used one day to increase the rate at which microvasculature can form deceullarized scaffolds.
