The reduction of oxygen occurring as a result of advanced vascular diseases poses severe clinical problems including massive cell death and resultant tissue loss. Compared to pharmacological methods of therapeutic angiogenesis, cell-based strategies represent a direct approach to generate a capillary network. Endothelial colony forming cells (ECFCs) are a subpopulation of endothelial progenitor cells that exhibit robust angiogenic potential under hypoxic conditions and can form functional vascular networks in vivo. Adipose- derived stem cells (ASCs) are a promising cell population for promoting angiogenesis and potentially stabilizing new vessels. However, the success of cell-based therapies is limited by rapid cell death due to apoptosis upon implanting cells into ischemic tissue environments, dramatically reducing the number of cells available to participate in vasculogenesis. Additionally, recent data suggest that cells derived from older donors are more vulnerable to apoptosis than those from younger donors, potentially compromising the effectiveness of autologous cell-based approaches for tissue repair in the ever-growing aging population. Lysophosphatidic acid (LPA) is a platelet-derived lipid growth factor present within the serum and is required for angiogenesis in vivo. Additionally, LPA promotes the survival and viability of progenitor cells within pro-apoptotic microenvironments in vitro. Our central hypothesis is that localized and sustained presentation of LPA will be an effective agent to inhibit apoptosis in implanted cells, thus enabling prolonged secretion of trophic factors from cells and supporting the survival of vessel-forming cells. The rationale for this project is that it will provide new insights into the role of the oxygen microenvironment and how progenitor cells participate in tissue repair, and yield new approaches for enhancing the efficacy of tissue repair with cells from aged donors.
Aim 1. Determine the anti-apoptotic and proangiogenic effect of sustained LPA release on co-cultures of human ECFCs and ASCs within fibrin gels. The ability of localized LPA release to inhibit apoptosis in hypoxic and serum-reduced conditions will be assessed, and the resulting vasculogenic response to these stimuli will be quantified.
Aim 2. Determine the capacity of ASCs derived from aged donors and ECFCs to resist apoptosis and enhance vascularization when co-implanted on LPA-eluting materials into a murine ischemic hind limb model. The proposed research is innovative because it examines a novel approach for addressing the loss of cells implanted for neovascularization while investigating the role of multiple stimuli on vessel formation critical for the clinical translation and realization of these approaches. We will elucidate the contributions of LPA delivery on extending the viability of ASCs from older donors when implanted into an ischemic tissue site characteristic of advanced vascular disease. Collectively, this research will provide a novel approach for enhancing the efficacy of implanted cells for cell-based therapies for tissue repair, wound healing, and emerging applications in tissue engineering and regenerative medicine.
The development of new approaches to enhance cell viability and function upon implantation will greatly improve the quality of life for those who suffer from advanced vascular disease or non-healing tissue defects. We seek to determine if the localized presentation of a phospholipid can inhibit apoptosis in implanted vessel- forming cells, thereby resulting in prolonged survival and enhanced neovascularization.
