Effects Of A Low Dose Of Insulin And Hsp90α In Diabetic Wound Healing

High morbidity of chronic skin wound increases steadily in diabetic patients. Thehealing of such wounds is usually delayed or non-healed leading to not only health risksfor the patients but also heavy economic burdens to both families and societies. So far, thepathogenesis of diabetic wound is not fully understood and there is a lack of effectivetreatments for this refractory disease. Studies on animal models showed that application ofinsulin could significantly shorten the healing time of acute and chronic wounds. But thespecific mechanisms are not clear. It also found that cells could secrete Hsp90α under thecondition of hypoxia, and the extracellular Hsp90α could promote the migration ofkeratinocytes and fibroblasts to accelerate the wound healing although the mechanisminvolved needs further investigation.To analyze the therapeutic effect and potential mechanism of the low dose of insulinand Hsp90α on diabetic wound, the present study utilize high-carbohydrates-fat diet and alow dose of STZ to induce rat diabetic status and full-thickness skin excisional woundswere made on the back of rats thereafter. The diabetes rats were randomly divided and thewounds were treated by: non-treatment (group A), vaseline gauze (group B), low doseinsulin (group C), Hsp90α (group D), and combination of low dose insulin and Hsp90α(group E). Identical wounds were also made on non-diabetic rats (group O) and notreatment was given for this group as that in group A. Wound healing time, rates, changesin wound morphology and microvessel density were evaluated by wound tracing,histopathological studies on H&E or anti-CD31antibody stained tissue sections,respectively. Wound tissue expressions of VEGF、TGF-β1、IGF-1、TNF-α and IL-1weredetermined by real time PCR. Results showed that diabetic SD rat model was successfully established by feedingwith high-carbohydrates-fat for4weeks followed by three intraperitoneal injections ofstreptozotocin at a dose of25mg/kg. The time for complete wound reepithelialization ingroup O was16.4±1.5dyas whereas that in other groups were35.5±0.9days (group A),31.4±1.2days (group B),25.3±1.8days (group C),25.6±1.4days (group D) and20.3±1.4days (group E) respectively. The healing times of groups C, D and E were significantlydecreased relative to that of groups A and B (P<0.05) although longer than that of group O.In comparison with group A, the healing rates in groups B, C, D and E increasedsignificantly (P<0.05) and the maximal increase was found in group E. Microscopicobservation on HE stained sections showed that the treatments in groups C, D and Eincreased reepithelialization, decreased the infiltration of inflammatory cells, increasedfibroblast proliferation and neovascularization than that in groups A and B. Again, themost significant differences were found in the treatment of group E among theseevaluations. Compared with groups A and B, Masson stained sections showed that thecollegan arrangement and formation of neo-vessels were improved in groups C and Dwhile the most siginificant improvements were observed in group E, though the extent ofimprovements were not as marked as that in group O. In addition, the expressions ofVEGF, TGF-β1, IGF-1, TNF-α, IL-1and microvessel density were upregulated andincreased significantly in groups C, D and E relative to that in groups A and B (P<0.05).The results demonstrated that a high-carbohydrates-fat diet in combination of lowdose STZ can induce stable type2diabetic status in rat model and wound healing processwas delayed in these diabetic rats. The topical utilization of either low dose insulin orHsp90α enhanced the reepithelialization, fibrosis and vascularization of the diabeticwound tissues and accelerated chronic wound healing, without interference with fast bloodglucose. The possible mechanisms associated with the up-regulations of VEGF, TGF-β1,IGF-1, TNF-α and IL-1. The combination of low dose insulin and Hsp90α achieved betterresults than each of the individual treatment.