Research On Molecular Mechanism Of Wound Healing During The Initial Stage Of Antler Regeneration

Skin wounds cannot be healed through tissue regeneration in human.Scarification is the outcome of cutaneous wound healing under normal conditions.Although considerable effort has been expended in this field,scar-less healing has not been achieved satisfactorily.The lack of a good model of scar-free healing has contributed to this undesirable situation.Deer antlers are the only mammalian organs capable of complete renewal.In the process of antler regeneration,the skin can be effectively repaired and completely regenerated.So,it provides an excellent model for us to study how to achieve regenerative repair in skin in natural.In this study,we investigated the healing process of pedicle wound during the initial stage of antler regeneration in morphological,histological,cellular and molecular levels.Firstly,we analyzed the pedicle wound healing process with full-thickness excisional cutaneous(FTE)wounds in rat as control.Our results showed that the huge wounds were healed rapidly without fibrosis,including regeneration of skin appendages,such as hair follicles.The process of hair follicle regeneration during wound healing of pedicle wounds was similar to that of hair follicle development in embryo.Our results convincingly demonstrate that wounds over the pedicle preceded a regenerative healing process.Secondly,the tissue events characteristic of regenerative wound healing of pedicle was investigated.The results showed that compared to the scar healing in rats,regenerative healing of the pedicle wound exhibited a weaker inflammatory response,lack of myofibroblast induction and higher ratios of Col III/Col I,TGF-?3/TGF-? 1,and MMP2/TIMP2.Ultimately,the regenerative wound healing program resulted in the near-perfect restoration of pedicle skin.Thirdly,considering the above dates,a recurring question has been whether it is the intrinsic attribute of pedicle for its ability to achieve wound heal with tissue regeneration,or acquired? Research has reported that antler regeneration is a process completely dependent on antler stem cells(i.e.,pedicle periosteal cells).Therefore,we speculated that it is the presence of ASCs that induces pedicle wound repair towards regenerative outcomes.To test the attractive hypothesis,we performed histological examination of healing tissue of ectopic pedicle wounds,which formed by periosteal transplantation experiments.Results showed that the ectopic pedicle wounds perfectly healed as well as the wounds in situ,including regeneration of the hair follicles and sebaceous glands.Deer forehead skin can normally form only scar tissue when wounded,but in this case,it acquired the regenerative ability of wound healing when it became associated with the event of antler regeneration.Thus,our data support our hypothesis that it is the periosteal cells,that is the ASC,that fully underpin regenerative wound healing of pedicle.These findings lead to the question of species-specificity of the response.Might the ASCs themselves promote regenerative wound healing in the rat(or other mammalian species)? To address this issue,we examined the effects of ASCs on cutaneous wound healing in a rat FTE wound model,and found that systemically injected ASCs effectively promoted regenerative healing in rodents.In order to explore the molecular mechanism,we tested the effect of ASCs on wound healing in vitro.The results showed that ASCs significantly promoted the dermal fibroblasts proliferation,migration,inhibited differentiation into myofibroblasts and increased the TGF-?3/TGF-?1 ratio through paracrine effect.Therefore,ASCs may promote the regenerative wound healing by inducing the transformation of fibroblasts to fetal fibroblasts.Overall,the evidence is that ASCs may have a profound therapeutic potential in promoting tissue regeneration and preventing scar formation.In addition,we investigated the activation process of pedicle periosteum(PP)tissue in the initial stage of antler regeneration,using RNA sequencing(RNA-seq)and bio-informatics analysis.The results showed that the activation process of PP is regulated by pathways including cell cycle,bone formation and fatty acid metabolism,and androgen may mediate this process via calcium signaling pathway and AP-1 proteins such as c-Fos and c-Jun.We believe our findings have laid the foundation for revealing the molecular mechanism of antler regeneration,which provides new perspectives and therapeutic approaches for regenerative medicine and oncological therapy.