The Experimental Study Of The Hypertrophic Scar On Rabbit Ear Treated By Fractional CO₂ Laser And Collagenase

Objective:To study the treatment of hypertrophic scar of rabbit ears by fractional CO₂ laser and collagenase,observe the morphologic and histological changes of hypertrophic scar in rabbit ear,analysis the changes of collagen and chondroitin sulfate in the scar tissue,analyze the collagen degradation process after fractional CO₂ laser treatment of hypertrophic scars,investigate the effect of fractional CO₂ laser on collagen and its outsourced coiling chondroitin sulfate in hypertrophic scar.To provide a theoretical basis for the clinical use of fractional CO₂laser in the treatment of hypertrophic scar.Methods:First of all,selected 12 New Zealand rabbits,making rabbit ear hypertrophic scar model,the hypertrophic scar model were randomly divided into four groups（24 in each group）:collagenase treatment group（group A）,laser treatment group（group B）,laser combined with collagenase treatment group（group C）and the control group of scar（group D）scar,four hypertrophic scar models were obtained in each side of the rabbit ear,which were 96 in total.When the scars were stable,on the first day use the fractional CO₂ laser to process the groups B and C（DeepFX:Energy:15mJ,frequency:300Hz,Shape:2,Size:8,Pules:1,Density:5%）,applying moist burn ointment to smear the wound after treatment.The groups A and C were injected of collagenase in seventh days（Each cicatricial was injected with 100U/ml bacterial collagenase saline solution 0.5ml,that is 50U）.The specimens were collected in 1st,3rd,5th,7th weeks after treatment,each specimen immediately divides into two,and part of it immediately fixed in 10%formaldehyde,paraffin embedded preservation,then the specimens were stained and sliced according to the method of HE staining and compound staining（alcian blue and eosin staining composite,the same below）methods.According to the HE staining specimens to observe the tissue changes of hypertrophic scar,according to the compound staining to observe the changes of chondroitin sulfate and used the image analysis software to measure the content of chondroitin sulfate,the remaining specimen were measured the content of hydroxyproline content by the ELISA kit,analyze the collagen degradation after fractional CO₂ laser and collagenase treatment of hypertrophic scars.The collected experimental data were analyzed by SPSS 21.0.Results:1.General observation:The model of scars were gradually stabilized after a month,four groups of rabbit ears wound healed and form hypertrophic scar with the Characteristic of hard,red,and bulging skin.After treatment,the three groups of A,B and C were thinner than the group D,and the scars of groups B and C were soft texture and the color fades.There was no obvious change in the scars of group D.2.Histopathological observation:HE staining showed the dermis of hypertrophic scar was significantly higher than the surrounding normal skin thickening when modeling successful,and showed a large amount of fibroblasts and collagen tissue,superficial collagen distribute irregular or whorled,deep collagen distribute stripe,part of capillaries and infiltration of inflammatory cells.The collagen of the groups B and C arranged more ordered,fibroblasts and capillary reduced after treatment,while group A only collagen thickness becomes small,no significant changes in group D.Compound staining showed a large number of collagen fibers in the hypertrophic scar,disorderly arrangement,wrapped around the visible light blue of chondroitin sulfate when modeling successful,the groups B and C showed the collagen fibers gradually become orderly,the blue chondroitin sulfate which surrounded the collagen fibers gradually decreased after treatment.There was no significant change in chondroitin sulfate in groups A and D before and after treatment.The image analysis showed that the chondroitin sulfate of groups B and the C were less than before the treatment.The two groups were compared with the D group,the difference was statistically significant（P<0.05）,but there was no significant change in the A group and the D group,and there was no significant difference between the A group and the D group（P>0.05）.3.Hydroxyproline content changes:By using ELISA kit,the contents of hydroxyproline in the groups A,B and C decreased after treatment,the change of the group D was not obvious.The difference of the three groups was statistically significant（P<0.05）compared with the group D,and the two groups of B and C were respectively compared with the A group,and the extent of collagen reduction was greater,the difference was statistically significant（P<0.05）.Conclusion:1.The content of chondroitin sulfate in hypertrophic scars decreased significantly after the treatment of fractional CO₂ laser.It indicated that fractional CO₂ laser could destroy the chondroitin sulfate surrounded by collagen.2.In the experiment,the effect of promoting collagen degradation in the group of laser combined with collagenase more than that in the collagenase injection group,the analysis may be that the laser cracked the chondroitin sulfate outsourced by the collagen,making the laser fully contact with the collagen fibers,and thus promoting the degradation of collagen.3.In the experiment,the detection indexes of the CO₂ laser combined with collagenase group were not better than that of the simple laser treatment group,which were different from the previous experiments.The possible reasons were the experimental design error,and the CO₂laser itself had a strong effect on the collagen degradation.