| Background: The wound of diabetes mellitus(DM)has the characteristics of complex pathogenesis and high disability rate.The poor curative effect,the long course of the disease,the high cost of treatment and other factors have caused a huge burden on the family and society.Puerarin,a Chinese medicine extract of pueraria root,has the effects of lowering blood sugar,anti-inflammatory,antioxidant,repairing nerves and improving circulation.It is also the first Chinese medicine substance that can form hydrogels naturally.It can fully retain pharmacological activity and has the potential to be a new dressing to promote wound healing.Objective: To explore the effect of puerarin hydrogel on skin wound healing and vascular formation in DM rats.Methods: 1.Establishment of DM rat model: 45 SPF SD rats were fed with 1week of standard feed and continuously fed high-glucolipid diet.1% streptozotocin was injected intraperitoneally and tail vein blood glucose was measured at day 7.If blood glucose value was 16.7 mmol/L,polydipsia,polyphagia and polyuria were considered as successful in DM rats.2.Preparation of puerarin hydrogel: Electronic scale accurately weighed puerarin powder 10.0 mg and placed it in 1 m L PBS.Heat the alcohol lamp to 100℃until puerarin powder is completely dissolved.1% puerarin hydrogel can be formed by cooling at room temperature for 5-10 min.2% and 4% puerarin hydrogels were prepared by the same method.3.Establishment and grouping of DM wound model: 36 DM rats were anesthetized by intraperitoneal injection of 6.0 m L/kg 1% sodium pentobarbital solution.Use electric shear to carefully remove back hair.A circular wound with a diameter of 2.0 cm was designed and cut to the muscle layer according to the marks.The whole skin layer was removed with tissue scissors.They were divided into control group,1% puerarin group,2% puerarin group and 4% puerarin group according to random number table method.The wound of control group was treated with PBS wet compress,while puerarin group was treated with puerarin hydrogel of different concentrations applied with sterile cotton swabs.The coating thickness should be about 2.0mm once a day for 14 consecutive days,and the coating scope should be at least 2.0mm beyond the wound edge.The coating should be covered with sterile gauze and properly fixed.4.Observation of wound healing and calculation of wound healing rate:Observe whether there is obvious bleeding,contamination or infection during wound healing.The photos were taken on days 3,7 and 14.Image pro plus 6.0 software was used to measure the wound area.The wound area of each group was averaged at the same time point.The wound healing rate was calculated according to the formula "wound healing rate =(initial wound area-actual wound area)/initial wound area ×100%".5.Histological examination: On the 3rd,7th and 14 th day,3 rats from each group were cut close to the wound edge of the back of the rats to the muscular layer,and the wound tissue was completely cut.Store tissue blocks in 4%paraformaldehyde solution or-80 ℃ refrigerator as needed.Glucose content in wound tissue was measured by oxidase method.Histological changes of the wound were observed by HE and Masson staining.Vascular endothelial cell growth factor(VEGF)and CD31 were stained by immunohistochemistry.Integrated optical density(IOD)and microvascular density(MVD)were calculated using Image pro plus 6.0 software after taking pictures under the microscope.Western Blot Semi-quantitative was used to detect the expression of VEGF protein in wound tissues of each group.6.Statistical processing and image analysis: SPSS 26.0 software was used for data statistical processing.Image pro plus 6.0 software is used for image analysis and calculation.Measurement data such as body weight,blood glucose,tissue glucose content,wound healing rate,collagen fiber area,IOD and MVD were expressed by (?)±s.F test was used for comparison between groups.LSD method was used for comparison between groups.Bilateral P < 0.05 was considered statistically significant.Results: 1.Weight and blood sugar:There was no statistical difference in initial body weight and blood glucose in each group(P>0.05).The trend of body weight after the DM wound was not different from the control group,the weight growth slowed down in the first week,and the weight decreased slowly in the second week(P>0.05).The blood glucose values of each puerarin group were not statistically different from the control group(P>0.05),and all showed small fluctuations within two weeks(fluctuation range was no more than 3.0 mmol/L).Body weight changes and blood glucose levels in the 4% puerarin group were not significantly different from the remaining low-concentration puerarin group(P>0.05).2.Wound healing: The wound surface of each group decreased gradually with time.Compared with the control group,puerarin groups formed fresh granulation tissue earlier and healed significantly faster(P<0.05).Compared with other low concentration puerarin groups,4% puerarin group had the highest healing rate at all time points(P<0.05).3.Measurement of glucose content in wound tissue: There was no statistical difference in glucose content between wound tissue before and after each puerarin hydrogel treatment and the control group(P>0.05).The glucose content of wound tissue was not changed among puerarin groups(P>0.05).4.Histological change: The results of HE and Masson staining showed that no blood vessels or collagen fibers were formed in the control group on the 3rd day,while the puerarin groups had initial capillary formation and collagen fibers were sparse.The capillary formation was more obvious in 4% puerarin group,but the structure of tube wall was immature.On the 7th day,blood vessel formation was still difficult in the control group,and collagen fibers were sparse.There were different degrees of thin-wall capillary formation and collagen fiber distribution in puerarin groups,among which 1% and 2% puerarin groups showed new capillaries,but the wall structure was not regular.4% puerarin group showed an early trend of vascular remodeling,the tube wall thickened and tended to be regular,and collagen fibers were abundant.On the 14 th day,a small number of thin-walled capillaries were formed in the control group,with irregular lumen and slightly denser collagen.The number of capillaries in puerarin groups increased,and there were some late healing changes such as lumen stenosis,tube wall thickening and collagen fiber richness.The healing trend of 4% puerarin group was the most obvious.5.Immunohistochemical staining of VEGF and CD31: Over time,the IOD and MVD of VEGF increased gradually in each group.The IOD and MVD of VEGF increased significantly in puerarin groups(P<0.05).Compared with other low concentration puerarin groups,the IOD and MVD of VEGF in 4% puerarin group were the highest at the same time point(P<0.05).6.Western blot semi-quantitative detection of VEGF protein expression: On days 3 and 7,VEGF protein expression in the 1% puerarin group was not significantly different from the control group(P>0.05).The protein expression of VEGF in 2% and 4% puerarin groups was higher than that in control group(P<0.05).The protein expression of VEGF in 4% puerarin group was higher than that in other low concentration puerarin groups(P<0.05).On day 14,the protein expression of VEGF in puerarin groups was higher than that in control group(P<0.05).VEGF protein expression in 4% puerarin group was higher than that in other low concentration puerarin groups(P<0.05).Conclusion: Puerarine hydrogel promoted the expression of VEGF and CD31 in DM wound tissue in a concentration-dependent manner,induced the formation of microvessels,promoted the deposition of collagen fibers in the wound tissue,and thus promoted the healing of DM wound. |
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