Experimental Study On The Treatment Of Hypertrophic Scars Using Fractional Er: YAG Laser-assisted Interferon Delivery

Objective1. To verify the efficacy of Fractional Er: YAG Laser-assisted Interferon Delivery onhypertrophic scars in the rabbit ear model.2. To observe the changes of the apoptosis rate of fibroblasts after treatment and detectthe changes of cytokine VEGF, MMP-1, TGF-β1and collagen type I in scar tissue. Toexplore the mechanisms of Fractional Er: YAG Laser-assisted Interferon Delivery forhypertrophic scars and provide a theoretical basis for the efficacy of the treatment ofhypertrophic scars.Methods1. Forty healthy adult New Zealand white rabbits were used to establish animal model forhypertrophic scars. Six9mm diameter round wounds on the ventral of rabbits ears weremade with local anesthesia, full-thickness skin along with perichondrium was removed andcartilage was kept. Hypertrophic scars were shaped after28days.2. Scars were divided into three groups randomly. The treatment groups were treated withIFNα-2b by conductivity meter for10minutes after Fractional Er: YAG Laser. The controlgroups were treated with Fractional Er: YAG Laser, and the blank control groups werewithout treatment.3. Thickness of scars was measured for Hypertrophic Index calculating and the scarspecimen was cut off on the1st,3rd,7th,14th,30th day after the treatment. Thepathological changes of scar tissue were observed after HE staining. The changes ofapoptosis rate were detected with TUNEL. The changes of VEGF and MMP-1expressionwere detected with immunohistochemical method, and the changes of VEGF, MMP-1, TGF-β1and collagen type I mRNA expression were detected with Real-time PCR.Results1. General observation: The hard and red hypertrophic scars were formed gradually after28days. The bleeding on the MTZ area was observed immediately after laser therapy. Thecolor of scars in the treatment group became darker than the control group at moment andon the1st,3rd days after interferon therapy. Gradually the color of Scars became lighterboth in the treatment group and the control group form the7th day after therapy.Hypertrophic Index decreased in the treatment group was lower than that in the controlgroup, and the scars were softened and smoothened from the14th and the30th day aftertherapy. The scars in the treatment group disappeared and that in the control group nearlyflatten. The color, texture and height of scars showed no significant change during30daysafter therapy in the blank control group.2. HE staining shows that compared with the control group, erythrocyte extravasationwere found farther apart form MTZ organization in the treatment group on the moment andthe1st day after therapy. The number of blood vessels decreased both in the treatmentgroup and in the control group after therapy. Compared with the control group, the numberof blood vessels decreased more obvious on the1st,3rd and7th days after therapy. Thenumber of fibroblasts gradually reduced and collagen gradually became parallel in thetreatment group and in the control group after therapy.3. TUNEL detection of fibroblast apoptosis rate shows that apoptotic cells were found inkeratinocytes, fibroblasts and endothelial cells. The apoptosis rate gradually increased andreached a peak on the7th days after therapy in the treatment group and the control group,and was significantly higher than in the blank control group (P <0.01). The apoptosis ratewas higher in the treatment group than in the control group on the1st and3rd day aftertherapy (P <0.01). A large number of apoptotic cells were found in the blank control groupon the30th day after therapy.4. The protein and mRNA expression of VEGF: Immunohistochemical results showed that the VEGF positive rate gradually decreased form the7th day after therapy, and thepositive rate in the treatment group and in the control group was lower than that in theblank control group on the7th,14th and30th day after therapy（P<0.01). The positive ratein the treatment group was lower than that in the control group on the7th, and14th daysafter therapy（P<0.05). Real-time PCR results showed that VEGF mRNA expression levelsdecreased gradually both in the treatment group and in the control group from the7th dayafter therapy and were lower than those in the blank control group on the7th,14th and30th days after therapy, while the levels in the treatment group were lower than that in thecontrol group.5. The protein and mRNA expression of MMP-1: Immunohistochemical results showedthat the MMP-1positive rate increased gradually and peaked at the7th day after therapy.The positive rates in the treatment group and in the control group were higher than those inthe blank control group. The positive rates in the treatment group were higher than in thecontrol group. Real-time PCR results showed that the expression levels of MMP-1mRNAincreased gradually and peaked at the7th day after therapy. The level showed nosignificant change in the blank control group. The levels in the treatment group werehigher than those in the control group and in the blank control group (P <0.01). The levelsin the control group were higher than those in the blank control group (P <0.01).6. The expression of TGF-β1mRNA: Real-time PCR results showed that the expressionlevels of TGF-β1mRNA decreased gradually in the treatment group and in the controlgroup after therapy. The levels in the treatment group were lower than those in the controlgroup and in the blank control group (P <0.01). The levels in the control group were lowerthan those in the blank control group on the3rd,7th,14th and30th days after therapy (P<0.01).The levels showed no significant change in the blank control group.7. The expression of collagen type I mRNA: Real-time PCR results showed that theexpression levels of collagen type I mRNA decreased gradually in the treatment group andin the control group, which were lower than those in the blank control group after therapy(P <0.01). The levels in the treatment group were lower than those in the control group on the3rd,7th,14th and30th days after therapy (P <0.05). The level showed no significantchange in the blank control group.Conclusions1. Fractional Er: YAG laser-assisted interferon delivery would quickly promotehypertrophic scars soften and subsided. It was a more effective method than fractional Er:YAG laser for the treatment of hypertrophic scars.2. Fractional Er: YAG laser can promote fibroblasts apoptosis in scars and the apoptosisrate was increased significantly after laser-assisted percutaneous absorption of IFN.3. Fractional Er: YAG laser can reduce the secretion and expression of VEGF inhypertrophic scar and the level of VEGF decreased more significantly after laser-assistedpercutaneous absorption of IFN. It’s may be one of the mechanisms for treatment ofhypertrophic scars.4. Fractional Er: YAG laser-assisted interferon delivery can decrease the expression ofTGF-β1and increase the expression of MMP-1and reduce the level of collagen type I inrabbit ear hypertrophic scar tissue, which may be one of the mechanisms for the treatmentof hypertrophic scars.