Fabrication And Experimental Study Of A Dermal Substitute Loaded With Angiogenin

Since its development by Yannas and Burke in 1980,artificial dermis has been used as a dermal regeneration template and has become an effective method for the treatment of full-thickness skin defects resulting from severe burns and injuries. However,compared with split-thickness skin autografts,artificial dermis lacks a vascular network and the body's spontaneous biological responses,including angiogenesis,are slow following transplantation.Angiogenesis of artificial dermis takes longer time than that of autografts because it occurs through the process of neovascularization alone.During this avascular period,low resistance to infection is obviously a clinical problem.Therefore,it is important to help the body exert its natural angiogenic mechanisms and to enhance blood vessel infiltration.Angiogenin (ANG)is a potent,blood vessel-inducing protein.A rapid and well-vascularized dermal substitute may be achieved by using a controlled release system,which can deliver ANG into the transplanted tissues.In this study,a porous collagen/chitosan scaffold was fabricated and heparinized using EDC(N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide)and NHS (N-hydroxysuccinimide)with a freeze-drying method.The morphology,swelling ratio and in vitro degradation of the scaffolds was studied.Using radioiodine labeling,the effect of heparin on the binding of angiogenin to the scaffold was studied.The release of angiogenin from the heparinized scaffold was investigated using a radioiodine labeling method and/or an ELISA method.The scaffolds loaded with or without angiogenin were embedded subcutaneously on dorsal surface of the New Zealand rabbit ears.And In vivo angiogenesis of the scaffold was then studied.Using a rat one-step skin transplantation model,the percentage of surviving graft area 2 weeks after grafting,the percent original wound area,the histological changes of the grafts, the angiogenesis of the transplanted tissue and the tissue response of the scaffold were evaluated to test the possibility of heparinized porous collagen/chitosan scaffold loaded with ANG to be used as a dermal regeneration template.The results showed that the scaffolds possess three-dimensional porous structures and their mean pore sizes increase upon EDC/NHS crosslinking.The heparinized scaffolds also have an enough water-absorbing ability and high ability to resist in vitro biodegradation,as well as a high binding ability to ANG.In vitro,angiogenin was released from the heparinized scaffold in a controlled manner.The presence of angiogenin enhanced the angiogenesis of the heparinized scaffold after subcutaneous implantation into rabbits.The one-step skin transplantation experiment showed that heparinized porous collagen/chitosan scaffold loaded with ANG has low antigenicity, rapid angiogenesis ability and the effect of dermal regeneration template,among which the rapid angiogenesis ability is the most important factor.In conclusion,the heparinized porous collagen/chitosan scaffold loaded with ANG fabricated here is a potential candidate for ideal dermal substitute that can be well clicically used in furore.