Mechanical Micronization Of Lipoaspirates Combined With Fractional CO₂ Laser For Treating Hypertrophic Scars

Objective:The purpose of this study was to investigate the efficacy and mechanism of stromal vascular fraction gel（SVF-gel）combined with fractional CO₂ laser in the treatment of hypertrophic scar,and to provide a theoretical basis for the clinical use of the two methods.Methods:Four adult female New Zealand rabbits were selected to establish a rabbit ear hypertrophic scar model.Briefly:after anesthesia,a 5.5cm X 1.5cm wound was made on the ventral side of the rabbit ears under aseptic conditions.4 weeks later,the wound healed and red humps were visible,scar and normal skin were stained with HE to identify hypertrophic scar model.Another 14 rabbits were taken to prepare rabbit SVF-gel.Briefly:under aseptic conditions after anesthesia,the bilateral inguinal fat pad was obtained,washed,shredded,centrifuged,repeatedly pushed,centrifuged again,and the bottom layer was collected as the rabbit SVF-gel.A total of 48 scar models were prepared from 24 rabbits,and randomly divided into four groups with 12 in each group:combined group（SVF-gel plus fractional CO₂laser group）,SVF-gel group,fractional CO₂ laser group and control group.Scar photos were taken with digital camera before treatment,4,8 and 12 weeks after treatment,and changes in scar appearance were observed.At the 4th and 12th week after treatment,scar tissue was taken for HE staining,and the expression of adipogenic signal PPAR-γand C/EBP-αm RNA and protein was further studied.variance was used to analyze the results.Results:1.A rabbit ear hypertrophic scar model was successfully established,and HE staining showed that the rabbit ear scar dermis was significantly thicker than the normal skin,and the difference was statistically significant（P<0.01）.2.The changes of scar appearance were recorded by digital camera at different time points.At the 4th week,compared with the control group and the laser group,the combined group and the SVF-gel group,the scar became flat,the texture became soft,and the volume decreased;At the 8th week,the area of scar hyperplasia in each group was further reduced,and the improvement was most obvious in the combination group;At the12th week,the texture,thickness,and color of the scar were most similar to normal skin in the combination group,while stiff and clearly raised scars were still visible in the control group.3.HE staining showed that at the 4th week,the dermis in the control group was flat,reticular,and inflammatory cell infiltration,but the inflammation in the combination group and SVF-gel group was relatively mild;at the 12th week,the thickness of the dermis in the combination group was the thinnest.Inflammatory cell infiltration was the least,and the skin structure level was clearer,but the control group hardly improved.4.Masson staining showed that the collagen arrangement of the combination group and SVF-gel group was more orderly than that of the laser group and the control group at the 4th week（P<0.05）;at the 12th week,the collagen arrangement of the combination group was the loosest and regular,while the control group still had dense and disordered collagen fibers（P<0.05）.5.Immunohistochemical staining of type I collagen showed that the combination group was weakly positive for type I collagen staining,while the control group was strongly positive for type I collagen staining.The expression of type I collagen in the combination group was significantly lower than that in the SVF-gel group,the laser group and the control group（P<0.05）.6.Perilipin immunofluorescence staining showed that the combination group had the strongest positive expression of perilipin,followed by the SVF-gel group and the laser group,the control group had the lowest positive expression,and the difference was statistically significant（P<0.05）.The results of qPCR and western blot showed that the m RNA and protein expression levels of C/EBP-αand PPAR-γin the combined group were significantly higher than other three groups,and the expression level of control group was the lowest,which was statistically significant（P<0.05）.Conclusion:SVF-gel transplantation combined with fractional CO₂ laser treatment can antagonize the formation of hypertrophic scars,and the mechanism may be related to the promotion of adipogenesis in scar and remodeling extracellular matrix.