| Background:Currently,wound repair is one of the most difficult problems that still bothers surgeons in traumatic orthopedics.With the accelerating of social rhythm and the aging of population,there has emerged a rising trend in the incidence and complexity of the wound.In recent years,a variety of new biomaterials for wound treatment are emerging in an endless stream.Many new ideas and new ways have been brought to solve the complicated wound healing problems.However,there is still no consensus that the treating protocol can be formed as will as a multicenter-clinical trial can be carried out.Studies have shown that stem cell-based tissue engineered skin has achieved remarkable results in promoting wound repair.However,stem cells are mostly derived from bone mesenchymal stem cells,adipose derived stem cells,embryonic derived stem cells and the pain can not be effectively avoided in the process of stem cell extraction.What's worse,those therapies are usually cost and the scope of treatment are also limited.In addition,some allogeneic stem cells as well as embryonic stem cells still exist some ethical controversy.In recent years,a method of extracting stem cells from urine has received wide attention and intrest.This kind of urine-derived stem cells(USCs)fully possesses the ability of regeneration and differentiation as well as the tissue repairation.What's more,the extraction method of USCs is painless and simple with a nearly unlimited source.It can not only continuously provide customized materials for tissue repair,but also can completely avoid any pain to patients.With the development of stem cell transplantation,more and more researchers have reached a consensus that the repair function of stem cells is more affected by their own paracrine effect on the recipient cells at the transplantation site.This proposal will inevitably require researchers to switch their stem cell transplantation ideas.Which means that we should turn from a local perspective that treats stem cells just as a substitute for damaged tissue,to a global perspective that treats the stem cells and the recipient cells as a whole.To this end,we applied a biomaterial-silicate bioglass(bioglass,BG),the previous studies have confirmed that this bioactive material can greatly enhance the paracrine effect of stem cells.But it remains unknown whether this effect is also present between USCs and skin receptor cells.Therefore,we constructed a model of cell co-culture between the two.USCs were transplanted to the wound bed after being activated by BG ions in vitro.Through the research above all,we tried to explore a new method of transplanting USCs for the treatment of wounds.In addition to focus on the cellular aspect of the wound,we also need to focuse on the outside barrier of the wound.Because the most prominent function of the wound is working as the barrier between the body and the outside.Hydrogel is a water-based dispersion medium with a grid-like cross-linked polymers,there are many common hydrogels have already been applied in clinic such as hyaluronic acid,fibrin glue,chitosan,etc.Although the traditional hydrogel has a good biocompatibility,but the biggest flaw of those hydrogels is the difficulty of effective and lasting integration with the wound.In this study,a new phototriggered Imine Crosslink(PIC)with excellent biocompatibility and tremendous tissue integrity was used as a carrier of platelet-rich plasma(PRP)extracted from human umbilical cord blood.We attempt to construct a new type of hydrogel that binds tightly to the surface of the wound and provides both a barrier to the wound and a resource of sustained released growth factors.The purpose of our research is to provide a new strategy and method for wound repairation from the inside out.Methods1.Firstly,the optional concentration of BG ion which showed the best induced effect on USCs was detected,through the determination of various growth factors in co-culture mediums and the states of USCs.Furthermore,indirect and direct co-culture models of USCs and endothelial cells and fibroblasts were constructed,and then the direct co-culture models involving those three kinds of cells were constructed.Finally,the effect of BG ion on the paracrine effect between USCs and recipient cells was evaluated by measuring the gene expression and protein synthesis in the co-culture system.2.Firstly,USCs were cultured with BG ion in vitro for three days.Then,USCs were transplanted on the wound of nude mice.Finally,the repair effect of USCs was evaluated by histological staining and immunohistochemical staining,after that the relative repair mechanism was speculated.3.The fresh umbilical cord blood PRP was extracted by two-step method.And then PRP were mixed with a new hydrogel in a certain propartion,which active ingredient is hyaluronic acid(HA)modified with photosensitive group o-Nitrobenzyl alcohol(NB),at last the target hydrogel were composited(HNPRP).The physical and chemical properties of HNPRP were assessed through fluid mechanics test,scanning electron microscopy,long-term sustained release of loading growth factor,and the cell scratch test.Furthermore,the repair function of HNPRP was tested on the model of refractory wounds in diabetic rats which were induced by streptozocin(STZ).The repair ability and mechanism of HNPRP on the refractory wounds were explored by means of wound histological staining and immunofluorescence staining.Result:1.BG ion can significantly improve the paracrine effect between the USCs and the skin receptor cells:(1)BG ion got the best activation effect on the USCs at the dilution ratio of 1/128;(2)Among the co-culture system of USCs-endothelial cells,BG ion could increase the expression of KDR,VEGF,VE-cad in endothelial cells;(3)Among the co-culture system of USCs,the expression of Collagen-1,fibronectin and ?-SMA in fibroblasts could be enhanced.(4)Among the three cell co-culture systems,the presence of BG ion also enhanced the expression of KDR,VEGF and VE-cad in endothelial cells as well as enhanced the synthesis of Collagen-1 and fibronectin in fibroblasts.2.BG ion can significantly improve the wound healing ability of USCs through the following mechanisms: USCs activated by BG ions can significantly enhance the viability of endothelial cells and fibroblasts through paracrine effect,then the blood supply and the deposition of collagen in wound bed are increasing,and the wound healing is accelerated ultimately.3.HNPRP can effectively release growth factors and significantly promote the repair of wounds in diabetic rats:(1)HNPRP can effectively release growth factors for up to 28 days;(2)HNPRP showed the ideal swellability and biocompatibility which were advantages of wound healing:(3)HNPRP could promote epithelial migration,angiogenesis and maturation in the wound as well as the secretion of collagen fibers in granulation tissue.Conclusion:1.BG ion can significantly improve the paracrine effect between urinary stem cells and skin receptor cells.Thereby enhancing endothelial cell angiogenesis and promoting fibroblast matrix protein synthesis and secretion.2.USCs activated by BG ion can significantly promote wound healing in nude mice.The mechanism is that urinary stem cells transplanted to the periphery of the wound after activation can effectively increase the activity of wound endothelial cells and fibroblasts,thereby improving the blood supply to the wound,increasing the deposition of structural proteins in the granulation tissue,and ultimately significantly promoting the repairation of wound in nude mice.3.HNPRP is an ideal material for wound repair.Its repair mechanism is effective in slow release of growth factors and can promote wound epithelial migration,angiogenesis and maturation as well as the secretion of collagen fibers in granulation tissue. |
PDF Full Text Request