Functional Stem Cell-Based Tissue Engineered Vascular Grafts for High-Risk Donor Populations

Despite the significant progress made in the field of tissue engineered vascular grafts (TEVG), there still exist a number of barriers that inhibit the clinical translation of many TEVG designs. This is illustrated by the high number of pre-clinical evaluations, but limited number of clinically tested grafts. The goal of this dissertation was to identify the most paramount of these barriers and address them in the adipose-derived mesenchymal stem cell (AD-MSC)-based TEVG previously developed within the laboratory of Dr. David Vorp. First, as many pre-clinical investigations that fail to assess cells derived from clinical populations who would routinely require a TEVG therapy, AD-MSCs from two prominent clinical populations – diabetics and elderly were evaluated. Utilizing both in vitro and in vivo approaches to identify altered functions with regards to TEVG maturation and patency, it was shown that diabetic patients in particular produce TEVGs that readily occlude via thrombosis. Additionally, decreased fibrinolytic activity was shown to be one altered pathway contributing to the pro-thrombotic phenotype. Second, as many approaches are practically limited by extensive fabrication times, a freshly-derived adipose-derived cell population – the stromal vascular fraction (SVF) – was utilized to fabricate TEVGs. This was compared to donor-matched culture expanded AD-MSCs to demonstrate the use of a new cell source free from the necessity of culture expansion. The results of this study showed similar in vitro and in vivo functionality of both cell populations in the context of TEVG applications. Finally, a cell-free alternative TEVG design was proposed with a proof of concept study that is alleviated from either barrier. A novel technology – termed as “artificial stem cells” – was developed that combines the stem cell secreted products with a microsphere-based delivery system to replace the in vivo cellular activity of AD-MSCs. Together, the work of this dissertation advanced the field of stem cell-based TEVGs by investigating the use of cells clinically realistic populations and proposing novel cell sources (SVF and artificial) to practical barriers to propel TEVGs towards clinical translation