Research On Embryonic Porcine Skin Precursor Xenotransplantation

Skin, the biggest organ of human body, assume the responsibility of protection, immunological regulation, metabolism and body temperature modulation, etc. The serious injury of local skin can be repaired by transplantation of autologous full-thickness skin, free skin flap and pedicle skin flap favoring restoration of integrate structure and function. Because of the lack of the autologous skin, autologous microskin grafting combined with large alloskin might be able to repair the wound quickly and save the patients'life but still leave many problems that can seriously influence the life quality not solved in the extensive deep burn and truma patients, in which the mechanical strength and elasticity of the neoregenerative skin tissue are far worse than the normal skin and the unavoidale scar emerge after convalescence. Recent research demonstrated that embryonic porcine precursor tissue or organ (i.e.liver, kidney, pancreas and spleen) at certain gestational age can develop into mature and functional tissue or organ without teratoma formation. What about the embryonic porcine skin precursor?In order to overcome these obstacles in large scale burn and trauma, such as the source of wound covering material and wound healing quality, in our study, we focus on the growth and development of the embryonic porcine skin precursor graft from five different gestational ages. With the help of convenient and effective xenotransplantation model, we observe the characteristics of the convalescent wound and the histomorphous and the structure of the neoregenerative tissue after transplanting to nude mouse and evaluate the tumorigenesis of the graft and the growth potential after transplantation. The results and conclusions are summarized as follows:1. In our research, we compared the following three transplantation models using the embryonic porcine skin precursor harvested at precise E(embryonic day)56. It is proved the model that the graft microgranules onto the dorsal full-thickness defect covering by xenogenous skin is the most convenient and effective xenotransplantation model. a. dorsal wound model: The wound involving upper- tunica muscularis was made on the center of the nude mouse dorsum, then transplanted with the graft granule suspension and finally covered with human cadaver skin.b. dorsal hypodermis model: The wound involving upper muscular fasciae was made horizontally on the center of the nude mouse dorsum, then transplanted with the stamp-like graft and finally sutured.c. auricle hypodermis model: The graft granule suspension was injected into the ear auricle hypodermis via subcutaneous puncture.The results of the first and the third model were evaluated using double-sample t test. The grafts in all the three models could develop into double-layer skin tissue with epidermis and dermis. Appendages such as hair follicles, sebaceous glands and sweat glands were seen in the first two models while sweat glands were not observed in the last model. Our data also demonstrated that growth potential of the grafts in the dorsal wound model was higher than that of the auricle hypodermis model.2. We systematically studied the growth state and tumorigenesis posttransplantation of embryonic porcine skin precursors from different gestational ages (E35, E42, E56, E70, E91). Embryonic porcine skin precursors from five precise gestational ages, were prepared as microgranules and then implanted onto wound surfaces of full-thickness skin defect, followed by xenoskin covering for protection. The neoregenerative tissue was performed biopsy in the 6th and 12th week after transplantation to study histomorphous and tumorigenesis. Melanin staining and immunofluorescence were performed to identify the tissue origin. The size of the neoregenerative tissue recorded in the 12th week was analyzed by mono-factor variance analysis to evaluate the growth potential. Our data strongly indicated that skin precursors from five different gestational ages could grow and develop into the"integrate"skin and the optimal time for embryonic porcine skin precursor xenotransplantation is around E56.a. The results showed that all skin precursors could grow and develop into the"integrate"skin, which consists of epidermis, dermis and appendages including hairs, hair follicles, sebaceous glands and sweat glands.b. Skin precursors obtained at E42 exhibited the maximal growth potential—the average size of neoregenerative tissue from E42 was 47.1 mm2 (L×W), while the average size of neoregenerative tissue from E35, E56, E71 and E91 was 18.4, 31.7, 20.1 and 6.5 mm2 respectively.c. Melanin staining and immunofluorescence were performed to identify the tissue origin.d. Orderly arranged collagen fibers and rete ridges were observed obviously in the neoregenerative tissue.e. No teratoma was detected in neoregenerative tissue from E56 and later gestational ages.Conclusion: The embryonic porcine skin precursor from E56 showed high growth potential and could develop into the"integrate"skin including hair follicles, sebaceous glands and sweat glands without teratoma formation. The optimal time for embryonic porcine skin precursor xenotransplantation is around E56.