Study On Enhanced Angiogensis Of Artificial Dermal Scaffold Combined With Angiogenin

Tissue engineered skin provides a promising therapy for patients suffered from severe skin loss, where autologous skin transplantation is usually limited duo to the great shortage of donor site. However, when compared to autologous skin, tissue engineered dermis today is out of vascular network and slow of the body's spontaneous biologic response, including angiogenesis, following transplantation. Split-thickness skin autografts vascularize by a combination of processes, including inosculation and neovascularization. Inosculation is the anastomosis of capillaries in the wound bed to the ends of severed vessels in the dermis of split-thickness grafts, and this is the primary mechanism of early graft vascularization. Neovascularization is the growth of new capillaries from the wound bed into the graft, and this process occurs later. Grafting of split-thickness human skin on to mice indicated that host endothelial cells did not appear in dermal capillaries of the graft for at least 1 week. Tissue engineered dermis takes longer than autografts for angiogenesis because it occurs through the process of neovascularization alone, and this contributes to failure of cultured skin grafts by more time for reperfusion, ischemia, and nutrient deprivation of grafted cells.In tissue development after transplantation the transport of nutrients initially depend on diffusion only. The cells apart from blood vessels with more than approximately 0.2mm usually can not keep survival because of oxygen deprivation and limitation of other nutrients. Therefore, it is important to help the body exerting its natural mechanisms for angiogenesis and enhancing blood vessels ingrowth. Several strategies are presently under investigation to induce angiogenesis. These strategies involve transplantation of various cell types (such as endothelial cells and fibroblasts) into the ischaemic site and the delivery of recombinant angiogenic agents through direct protein administration or gene transfer. Among these, the direct use of angiogenic growth factors is the most popular for its convenience and security. Growth factors are very important agents in controlling cell growth, inducing proliferation, stimulating cell migration and invasion and maintaining cell survival. However, using growth factors has a major limitation due to the rapid degradation of these proteins in vivo, while the host vessels' exposure time to the growth factors is one of several crucial issues that must be addressed to promote angiogenesis. Using controlled and localized growth factor delivery system to deliver specific growth factor(s) offers the potential to promote angiogenesis at a specific site. Recently, various growth factors have been applied to promote angiogenesis. However, it is a new attempt for angiogenin (ANG) to be used in engineered dermis. ANG is a 14k-Da single-chain protein first isolated from tumor-conditioned culture medium and circulates in normal human plasma. It is a potent inducer of angiogenesis for that as low as 1 ng ANG is active in vivo. We have previously reported the preparation of a novel collagen/ chitosan porous scaffold possessing excellent biocompatibility. In present study, the collagen/ chitosan porous scaffold was heparinized to fabricate a growth factor, ANG, delivery system. ANG was applied to dermal tissue engineering for the first time to achieve a rapid and well-vascularizeddermal substitute.ObjectiveTo fabricate a dermal scaffold capable of controlled release of angiogenin to achieve a rapid and well-vascularized dermal substitute. To study the controlled release behavior of angiogenin from the scaffod in vitro and the enhanced angiogenesis of the dermal scaffold combined with angiogenin in vivo.Materials and MethodsCollagen/ chitosan porous scaffolds for skin tissue engineering were fabricated by freeze-drying method and heparinized using N-(3-dimethylaminopropyl) -N-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS). The morphology of the scaffolds was studied by scanning electron microscopy. The angiogenin-combined dermal porous s...