Improvement On Vascularization Of The Acellular Xeno-dermis And Transplantation Of The Composite Skin Recombined In Vitro

Improvement on vascularization of the acellular xeno-dermis and transplantation of the composite skin recombined in vitro Background Closure of full-thickness skin defects is important to the treatment of patients with burn,traumatic injury,chronic skin ulcer or hyperthopic scar. The present approach is grafting autologous skin,which often results in heavy pigmentation and scarring in donor sites,and the amount of skin obtained by this method is limited for patients with large area skin injuries.The technique of skin tissue engineering has been a new method to provide adequate skin grafts and improve wound healing quality. Preparing the demial replacement and reconstituting the composite skin in vitro is the two main aspects of skin tissue engineering.The dermal substitutes grafted with an overlying thin autologous skin could exhibit an excellent cosmetic appearance and function of wound closure.On the other hand,the composite skin recombined in vitro could provide large amount of skin grafts for patients with extensive skin loss. The development of dermal replacement is particular crncial to skin tissue engmeering.Various dennal analogs such as Integra,Alloderm,Dermagraft et a! have been developed and used as dermal template to cover full-thickness wounds successfully.The dermal replacement grafted with thin autologous skin could shorten healing time of donor sites.The recipient sites have improved cosmesis and function with less pigrnentation,wound contraction and better durability. However,these dermal substitutes derived from allogeneic skin have limited sources as well as slow vascularization or poor survival grafted siniutaneously with autografls.Therefore,development of economical dermal replacement with good quality is necessary for the management of burn patients. The composite skin recombined in vitro could serve as a source of skin grafts.The artificial skin comprised of autologous keratinocytes cultured in vitro and porous collagen sponge membrane has been grafted onto the excised burn wounds.However,there is some question such as the long culture time,low antibacterial capacity and poor take rate that restricts the use of skin equivalent.The proposed key reasons include poor diffusion of nutrients,lack of ready-formed capillary network and slow neovascularization.The datum have shown that the most likely mechanism for skin graft survival is diffusion of nutrients, followed by inosculation of the recipient bed capillaries to the severed ends of the graft vessels and neovascularization.It is difficult for the nutrients in plasma to pass through the Alloderm,a acellular allo-dermal matrix,because it is lack of effective niicroholes responsible for the diffusion of liquid.On the other hand,the composite skin does not contain capillaries.So epidermis could not take enough nutrition until the establishment of capillary vascular flow during weeks 1 to 2 postgraft,all these lead to the graft slough and dead.Therefore it is essential for the composite skin survival to nurture the keratinocytes seeded on the surface of dermal substitute. In recent years,the study on skin tissue engineering at home has been made and is still in progress.The acellular derma] matrix(ADM) has been prepared,but the same question is low take rate.It's reported about the reconstitution of composite skin that allogeneic keratinocytes seeded on the surface of collagen matrix grafted onto the bum wounds after excision of eschar.Allogeneic cells would be rejected in the end inspite of low a...