| BACKGROUND:Diabetes is a global chronic disease.As one of its common complications,diabetic refractory ulcer is a major public health problem with high morbidity,high mortality and huge medical costs,which is easy to cause a heavy burden on the society.In recent years,both clinical and animal studies have shown that mesenchymal stem cells can promote wound healing in diabetic ulcers,but stem cell transplantation is faced with difficulties such as easy removal in situ,low efficiency of transplantation,and possible systemic risk.The new idea is that the use of exosomes derived from mesenchymal stem cells can effectively avoid the risks associated with stem cell transplantation and have the same or even better effect than that of stem cell transplantation.Some results showed that the application of hydrogels as scaffolds could provide suitable carriers for exosomes,which could be effectively applied to the target wound surface.Pluronic F127 is a polyoxylated polypropylene triblock polymer with unique temperature-sensitive properties that can be converted from a liquid state to a porous three-dimensional gel state at a certain concentration and temperature.It has good biocompatibility and has been used in drug delivery,composite material production and other fields.In this study,STZ induced diabetic rats were selected as subjects and Pluronic F127 hydrogel was used to load umbilical mesenchymal stem cell exosomes into the complex repair environment of diabetic wound surface to observe its effect on wound neovascularization and wound healing.METHODS:Exosomes in the supernatant of umbilical cord mesenchymal stem cell were extracted by extraction kit and identified through conventional transmission electron microscopy,NanoSight,and western blot.The exosomes were combined with Pluronic F127 gel at a concentration of 24%to prepare the hUCMSC-exos/PF-127 complex.The SD rat model of type 1 diabetes was established to make two symmetrical full-thickness skin incisions with a diameter of 10mm on its back.Incisions were randomly divided into four groups and treated with the corresponding treatments:1)hUCMSC-exos/PF-127 group:100 μg hUCMSC-exos dissolved in 100 μl Pluronic F127 hydrogel(24%);2)hUCMSC-exos group:100 μg hUCMSC-exos dissolved in 100 μl PBS;3)PF-127 hydrogel group:100 μl PF-127 hydrogel(24%);and 4)Control group:100 μl PBS.To better explore the mechanisms of tissue repairment,we did research on the treatment effects of the four differnent materials on the formation of new granulation tissue,angiogenesis,cellular proliferation.RESULTS:We extracted hUCMSC-exos using the extraction kit and identified the hUCMSC-exos successfully.The results showed that hUCMSC-exos showed a typical "saucer-like" structure and expressed exosome surface markers.Besides,44.4%of the particles were within the size range of 30 nm to 150 nm.At the 14th day after the treatment,the wound healing rate of hUCMSC-exos/PF-127 group was(97.8± 1.8)%,significantly higher than the other three groups(P=0.000).Immunohistochemisty results showed that the number of vessels in hUCMSC-exos/PF-127 group and hUCMSC-exos group was more abundant than that in PF-127 group and PBS control group at 7 days after treatment.The MVD in hUCMSC-exos/PF-127 group was 23.7±6.7 at 14 days after surgery,significantly higher than that in hUCMSC-exos group,which is 17.8±5.4(P=0.000).RT-PCR results also showed that the levels of VEGF and TGFβ-lin the experimental group were up-regulated on the 7th and 14th days after treatment(P<0.05).CONCLUSIONS:The efficient delivery of hUCMSC-exos in PF-127 gel could maintain exosomes’ ability for which diabetic wound healing could be promoted.Thus,this biomaterial-based exosome therapy may be a new therapeutic approach for cutaneous regeneration of chronic wounds. |
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