The Treatment Effect Of Negative Pressure Wound Therapy(NPWT) On Hypertrophic Scar In Rabbit Ears

Part Ⅰ The effect of Negative Pressure Wound Therapy(NPWT)on formation of hypertrophic scar in rabbit ears Objective:To establish an animal model of hypertrophic scar in rabbit ears and study the effect of negative pressure wound therapy(NPWT)on wound healing and hypertrophic scarring.Method:Six New Zealand white rabbits,numbered 1～6 randomly,were selected to design and form a single round wound with a diameter of 2cm on the ventral sides of rabbit ears.The self-matching study was used,NPWT group:The left rabbit ear wounds were treated with NPWT with negative pressure of-125 mm Hg(-17 k Pa)in a continuous mode for 8 hours per day.After continuous treatment for 7 days,all wounds were covered with vaseline gauze,bandaged with gauze,and replaced every other day until the wound healed;Control group(traditional dressing group):The right rabbit ear wounds were covered with vaseline gauze,bandaged with Anduofu gauze,and changed medicine every other day until the wound healed.At postwounding day 8,the conditions(the secretion,edema and blood circulation)of wound surface were observed to evaluate inflammatory reaction.The time of wound healing was determined by the total shedding of the crust of the wound.At postwounding day42,Vancouver scar scoring(VSS)method was used to evaluate the degree of scar hyperplasia.All specimens were cut and stained with hematoxylin-eosin staining(HE staining),Masson staining,picric acid-sirius red staining and immunohistochemistry.The scar thickness,collagen type-Ⅰ/Ⅲ(COL-I/III),α-smooth muscle actin(α-SMA)and cysteine aspastic acid-specific protease-3(Caspase-3)protein expression of two groups were analyzed and detected by combining with image-pro plus 6.0 software.Western-Blot was used to detect the content of transforming growth factor-β1(TGF-β1)protein and α-SMA protein in scar tissue of two groups.The datas were analyzed by SPSS 13.0 statistical software and paired t-test,with P<0.05 as the difference.Result:At postwounding day 8,The condition of wound surface in NPWT group had dry and clean,with less secretion,light edema and good blood supply,while the control group still had more secretion on the wound surface,edema did not completely disappear,color was pale and gray,and blood supply was slightly poor.Therefore,The inflammatory reaction of wound in NPWT group was lighter than control group.The times of wound healing in NPWT group were 22.500±3.728 days,lower than30.000±5.215 days in control group(P<0.05).The degrees of scar hyperplasia(VSS)in NPWT group were 5.500±1.643,lower than 9.500±1.049 in control group(P<0.05).The scar tissue thicknesses in NPWT group were 604.480±97.492 um,lower than 895.653±79.605 um in control group(P<0.05).The COL-I contents of scar in NPWT group were 6.642±2.609%,lower than 12.249±4.305% in controlgroup(P<0.05).The COL-Ⅲ contents of scar in NPWT group were9.535±3.099%,higher than 5.305±2.493% in control group(P>0.05).The contents of fibroblast with α-SMA in NPWT group were 4.238±0.526%,lower than13.164±1.317% in control group(P<0.05).The α-SMA contents of scar in NPWT group were 0.932±0.297,lower than 1.650±0.391 in control group(P<0.05).The Caspase-3 contents of scar in NPWT group were 4.567±2.580%,higher than3.391±1.94% in control group(P>0.05).The TGF-β1 contents of scar in NPWT group were 0.981±0.082,lower than 1.982±0.261 in control group(P<0.05).Conclusion:NPWT can promote wound healing and reduce the formation of hypertrophic scar.NPWT can reduce the formation of hypertrophic scar by inhibiting the production of TGF-β1 and reducing the differentiation of fibroblasts into myofibroblasts.Part Ⅱ The treatment observation of negative pressure wound therapy(NPWT) on hypertrophic scar in rabbit ears Objective:To establish an animal model of hypertrophic scar in rabbit ears and observe the treatment effect of NPWT on hypertrophic scar for exploring new treatment method of hyperrophic scar.Method:Six New Zealand white rabbits,numbered 7 ～ 12 randomly,were designed and formed a single round wound with a diameter of 2cm on the ventral sides of rabbitears respectively.Wound surfaces were covered with vaseline gauze,bandaged with Andofu gauze,and changed medicine every other day until the wound healed.Hypertrophic scar model of rabbit ears were established at postwounding day30 and VSS was used to evaluate binaural hypertrophic scar.the self-matching study was used,NPWT group:The right rabbit ear scars were treated with NPWT(the method was the same as part Ⅰ)for 7 days;Control group(positive pressure group):The left rabbit ear scars were wrapped with multi-layer gauze bandage for 7 days.After the animals have been disposed of,continue to be fed in the original environment,and regularly taken photos.After NPWT treatment day 6,VSS was used to evaluate scar conditions.Bilateral scar tissues were taken and sectioned for HE staining,Masson staining,picric acid-Sirius red staining and immunohistochemistry.The scar thickness,COL-I/III,α-SMA and Caspase-3 protein expression of two groups were analyzed and detected by combining with image-pro plus 6.0 software.Western-Blot was used to detect the content of TGF-β1 protein and α-SMA protein in scar tissue of two groups.The datas were analyzed by SPSS 13.0 statistical software and paired t-test,with P<0.05 as the difference.Result:At postwounding day 30,wound surfaces of two groups were completely healed.The scar formation of two groups was similar,the scar color was bright red,slightly higher than the normal skin surface,the central bulge was not obvious,and the texture was soft.VSS-1 of scar:NPWT group was 6.170±1.169,control group was6.667±1.211.The difference was not statistically significant(P>0.05).After NPWTtreatment day 6,the scar hyperplasia degrees in NPWT group was lower than control group.VSS-2 of Scar:NPWT group was 5.500±1.225,control group was8.667±1.506,The differences was statistically significant(P<0.05).The thicknesses of scar tissue in NPWT group were 305.161±86.839 um,lower than 652.080±221.237 um in control group(P<0.05).The COL-I contents of scar in NPWT group were5.537±1.316%,lower than 12.471±4.847% in control group(p<0.05).The COL-Ⅲcontents of scar in NPWT group were 6.836±3.025%,higher than 4.444±1.898% in control groups(p<0.05).The α-SMA contents of scar in NPWT group were1.428±0.427,lower than 1.777±0.374 in control group(P>0.05).The Caspase-3contents of scar in NPWT group were 5.286±0.833%,higher than 2.597±0.847% in control group(P<0.05).The TGF-β1 contents of scar in NPWT group were1.315±0.338,lower than 1.637±0.374 in control group(P>0.05).Conclusion:NPWT have a positive treatment effect on hypertrophic scar,and its effect mainly is related to promoting the apoptosis of fibroblasts.