New, innovative biological materials, that promote healing and prevent thrombosis, are in high demand to improve a variety of extracellular matrix (ECM) products ranging from wound dressings to vascular products. Considering the aging population and a sharp rise in the incidence of diabetes and obesity worldwide, the increase in chronic wound treatment exacerbates this burden. In the United States alone, chronic wounds affect over 6 million patients with annual costs exceeding 25 billion. A second substantial market opportunity is to develop vascular conduits that resist thrombosis and remain patent. Thrombosis is the leading cause of failure in vascular grafts. Traditional approaches to maintain graft patency involve delivery of anti-platelet agents or coverage of the luminal surface by endothelial cells to minimize platelet activation. Mice deficient in thrombospondin 2 (Tsp2-/-) have a profound wound healing advantage and significantly reduced thrombosis in animal models of tissue or vascular graft. These unique properties of TSP2-null ECM support its potential uses as a pro-angiogenic, non-thrombogenic treatment for wound therapies or in vascular applications. We propose to meet this need by production of TSP2-/- swine as a reliable source of TSP2-null ECM. Compared to rodents, swine have much greater genetic, anatomic, and physiological similarity to humans, offering an opportunity to produce vascular conduits that are of the correct size and non-branching length for human vascular surgeries. We hypothesize these animals will have enhanced wound healing characteristics and that biological scaffold materials derived from these animals will promote angiogenesis, provide elevated levels of growth and regulatory factors, and critically, inhibit thrombosis. Wound treatment therapies produced from TSP2-null and wild-type (WT) pig ECM will be assessed in WT pigs at 3-4 months of age by histology and immunohistochemistry to quantify healing rates, cell density, ECM deposition, vascularization, growth factors, and metalloproteinase (MMP) differences of healing excisional skin wounds. In addition, decellularized ECM from both TSP2-/- and WT pigs will be prepared and evaluated in vitro for the ability to support fibroblast and endothelial cell interactions and inhibit platelet aggregation. Finally, small diameter arteries will be harvested from TSP2-/- and WT pigs, decellularized and analyzed for their abilities to reduce platelet aggregation in vitro and in vivo in a previously developed rat graft model. If the role of TSP2 is conserved in swine, TSP2-null pigs will demonstrate increases in angiogenesis, levels of vascular endothelial growth factor (VEGF), and MMP-2 and MMP-9 concentrations in the ECM, and reduced thrombosis. These factors will lead to far superior starting material for creation of decellularized biomaterials that will improve the quality of life for millions and have substantial market potential.
The acute shortage of human tissues for the use in surgical applications has prompted significant research into the use of animal tissue as a key alternative to meet these needs. The thrombospondin 2 (TSP2-/-) pig that we propose to develop could revolutionize this initiative allowing for the development of new approaches for effective treatment of wounds in diabetic, burn victims, or other high-risk patients increasing healing rates and reducing instances of chronic wounds. We will also assess of the feasibility of using TSP2-/- pigs as a source for small caliber vascular conduit that resists thrombosis. This elusive medical device is considered, the ?Holy Grail? of vascular surgery.
