Experimental Study Of The Effects Of Fractional CO₂ Laser And Pulsed Dye Laser Combined With Triamcinolone On Hypertrophic Scar In Rabbit Ears

Objective:Through fractional CO₂ laser and 595nm pulse dye laser combined with triamcinolone injection to treat rabbit ear hypertrophic scar model,the morphological and histological changes of scar after treatment was observed,Collagen volume fraction and microvascular density were measured after treatment,then analysis the correlation of the collagen volume fraction and density of blood vessels.Finally,the efficacy of laser combined with triamcinolone injection was evaluated,try to find better treatment options and provide theoretical basis for hypertrophic scar treatment in clinical.Methods:1.Using ten New Zealand white rabbits as objects,rabbit hypertrophic scar models were made,and 80 hypertrophic scar models were obtained.They were randomly divided into 4 groups:control group,laser group,combined group,injection group,each group of 20 Scar models.2.The control group received no treatment;the laser group:first treated with 595nm pulsed dye laser（energy 10J/cm²,spot size 7mm,pulse width 20ms）;then the fractional CO₂ laser（Deep FX:energy 40mJ,frequency:300Hz,shape:2,size:8,pulse:1pass,Density:5%）;comb ined group:first treated with pulsed dye laser（595nm）and then treat the scar with Deep FX,finally,corticosteroids were injected into lesion.injection group:corticosteroids were injected into the lesi on（100ul）.3.Specimen collection:The morphological changes of hypertrophic scars in rabbit ears were followed and recorded.partial lesion tissues were taken at 7thday,14^thh day,28^thh day,and 2 months after treatment,and the specimens were preserved by paraffin embedding.4.Effect evaluation:HE staining was used to observe the histological changes;Masson staining was used to observe the expression of collagen,and the collagen volume fraction was measured;CD31staining was used to observe the changes in the number of micro-vessels,and the micro-vessel density was measured.5.SPSS 25.0 software was used to analyze the data.The measurement data was described as mean±standard deviation（χ±s）.One-way ANOVA was used to show the differences between the groups.The LSD posthoc test was used to compare the groups.Collagen volume fraction and microvessel density were analyzed by Pearson correlation coefficient.P<0.05 indicated that the difference was statistically signi ficant.Results:1.Overall observation:28 days after modeling,all rabbit ear wounds healed completely,producing hypertrophic scars that were red,hard,and higher than the normal skin nearby.After the treatment was completed,the scar thickness of the laser group and the combined group was significantly thinned,the texture was softened,the red gradually became lighter,and the color of the surrounding skin gradually approached.In the injection group,the scar thickness became thinner,the texture became softer,and the color became lighter.In the combined group,the thickness of the scar was thinner than that of the laser group and the injection group.In the control group,the hypertrophic state of the scar was not effectively improved.2.Routine histopathological observation:After HE staining,micro scopic observation showed that the hyperplastic scar dermis layer in the control group became thicker,and a large number of fibroblasts were accumulated.The collagen was dense and disorderly arranged,swirling or nodular,and capillary.Angioplasty,infiltration of some inflammatory cells,and disappearance of skin appendages.After treatment,the laser group,the combined group,and the injection group all recovered.The laser group and the combined group showed reconstruction of the dermal papilla;the histological changes of scars in the control group were not obvious.3.Masson staining observation:Image observation is the same as HE staining.Comparison of CVF:The expression of CVF in hypertrophic scar tissue was reduced in each group.The CVF values at 7 days and 2months in each group were compared.The difference between the laser group,the combined group,and the injection group was statistically significant（P<0.05）.),The control group was not statistically significant（P>0.05）;further CVF values were compared between the two groups at2 months after treatment,the combined group<laser group<injection group,and the P value between each group was statistically significant Significance（P<0.05）.4.CD31 staining observation:After treatment,the micro-vessel density in each group of hypertrophic scar tissue decreased.Comparing the MVD values at day 7 and 2 months in each group,the laser group,combination group,and injection group were statistically significant（P<0.05）,while the control group was not statistically significant（P>0.05）.The MVD values were compared between the two groups at 2 months after treatment.The combined group was less than the laser group and the injection group,but the P value between the combined group and the laser group was not statistically significant（P>0.05）.The P value between the injection group and the injection group was statistically significant（P<0.05）.5.The Pearson correlation coefficient analysis was r=0.972.It can be considered that there is a positive correlation between the collagen content and the number of micro-vessels.Conclusions:1.The combined method can reduce the number of fibroblasts,promote the normalization of collagen density and arrangement,reduce collagen volume fraction and microvascular density,and the curative effect is better than other method.2.There is a positive correlation between collagen content and micro-vessel density in hypertrophic scars.During the treatment,simultaneously inhibiting the proliferating blood vessels can improve the therapeutic effectiveness.