Experimental Study Of The Effect Of Fractional CO₂ Laser Combined With Pulsed Dye Laser On Hypertrophic Scar Of Rabbit Ears

Objective:The Fractional CO₂ laser combined with pulsed fuel laser was used to treat rabbit ear hypertrophic scar models.The morphological and histological changes of rabbit ear hypertrophic scars were observed.The expression changes of CD31 and VEGF under different treatment conditions were compared.The outcome of rabbit ear hypertrophic scars was discussed.It provides a theoretical basis for the clinical use of the synergistic effect of the Fractional CO₂ laser and pulsed dye laser to effectively inhibit scar hyperplasia and initiate skin regeneration in situ.Method:1.Ten New Zealand big eared rabbits were used to make rabbit ear hypertrophic scar models.A total of 80 hypertrophic scar models were obtained and randomly divided into groups:control?Group A?,Fractional CO₂ laser?Group B?,pulse dye laser?Group C?,combined?Group D?,20in each group,and normal skin group?Group E?.2.Fractional CO₂ laser treatment?Deep Fx:Fluence:15mJ,Frequency:300Hz,Shape:2,Size:8,Pulse:1,Density:5%?:B and D groups are given Fractional CO₂ laser treatment,A and C groups will not be treated.3.Pulse dye laser?Energy 9J/cm2,light spot 7mm,pulse width3ms,dynamic cooling equipment 20ms spray?:C and D groups are treated with pulse dye laser,A and B groups are not treated.4.Collection of specimens:Observe the general morphological changes of hypertrophic scars in rabbit ears in each group,and cut off small pieces of tissue in the lesion area on the 3rd,7th,14th,21st,and28th days after treatment,and store them in paraffin.5.Evaluate the effects of each group:stain the hypertrophic scar by HE staining,and then observe its histological changes;observe the collagen expression and blood vessel distribution in the hypertrophic scar by Masson staining;immunohistochemical method to determine the CD31 content in the scar Detect and observe the change of CD31expression;Western blot to detect the expression of VEGF protein in scars.6.The experimental data were analyzed by SPSS20.0 software:the data are all measurement data,the data are expressed as mean value±standard deviation,the comparison between groups is compared using single factor analysis of variance,and the indexes between groups are further compared using the LSD method.the comparison of the count data rate was performed by X² test,according to the standard of?=0.05,and the difference was statistical significance,P<0.05.Result:1.General observation:28 days after modeling,rabbit ears in all groups healed completely and formed hypertrophic scars with red,hard,and protruding protrusions.After treatment,the scars in group A still maintained a significant hypertrophic state;the proliferative nature of the two groups was B and C.The scar gradually atrophied,the scar volume became smaller,flattened and softened,and the color became lighter;the thickness of group D increased,and then became thinner,the texture became softer,and the color became lighter.2.Conventional histopathological observation:Microscopic observation after HE staining shows that the dermal layer of hypertrophic scars is thickened,and there are abundant fibroblasts,capillary proliferation,partial inflammatory cell infiltration,dense collagen,disordered arrangement,nodular or Spiral arrangement,the skin appendages disappeared.After treatment,the hypertrophic scars in groups B,C,and D all changed to normal skin to varying degrees,collagen arrangement tended to be neat,and the number of fibroblasts decreased.Among them,the results under group D were the closest to normal skin.The improvement in group A was not significant.3.Masson staining observation:Microscopic observation showed that collagen fibers in group A were stained light blue,arranged densely and irregularly,with a large number of fibroblasts distributed,microangiogenesis increased,and density increased;After treatment,the content of collagen fibers in the hypertrophic scars of groups B,C,and D decreased,and the arrangement tended to be horizontal,the number of fibroblasts decreased,and the degree of vascular proliferation was reduced to varying degrees.4.Immunohistochemical staining observation:The expression of CD31?brown particles?in vascular endothelial cells was increased in the hypertrophic scar tissue of group A.After treatment,the expression of CD31 in the hypertrophic scar tissues of groups B,C,and D was significantly reduced.CDMV-labeled Micro-vessel Density?MVD?was used to count the MVD values of each group.The experimental groups were compared with group A,P_A-B<0.05,P_A-C<0.05,P_A-D<0.05,the differences were statistically significant.5.Western blotting:7 days after treatment,the expression of VEGF in the hypertrophic scar tissue of the three groups B,C,and D was significantly reduced,and the P_B,P_C,and P_D were less than 0.05,and the difference was statistical significance.The results of the three groups were compared with the group A after 28 days of treatment.P_A-B<0.05,P_A-C<0.05,P_A-D<0.01,and the difference was statistical significance.The degree of decline was Group D>C>B.Conclusions:1.After treating hypertrophic scars with Fractional CO₂laser and pulse dye laser,it can more effectively improve the number of fibroblasts,collagen morphology,density,and arrangement;inhibit the proliferation of blood vessels,reduce inflammatory cell infiltration,and reduce CD31 and VEGF expression.The effect of Fractional CO₂ laser combined with pulsed dye laser treatment is better than that of Fractional CO₂ laser or pulsed dye laser alone.2.Pulsed dye laser can reduce the formation of hypertrophic scars by targeting its developing microvasculature.3.Two kinds of laser selective photothermal action on their respective target substrates?target tissues?,which are highly targeted.The two types of laser simultaneous treatment have a synergistic effect,which is conducive to the regeneration and repair of scars as a whole.