The Changes Of Apoptosis Rate Of Fibroblasts And VEGF Secretion After The Treatment Of Fractional CO₂laser On Hypertrophic Scars Model In Rabbit Ear

Objective：1.To prove the efficacy of fractional CO₂laser on hypertrophic scars in the rabbitear model.2. To analyse the changes of the apoptosis rate of fibroblasts and VEGF secretionafter the treatment of fractional CO₂laser on hypertrophic scars in the rabbit earmodel.To explain the efficacy of fractional CO₂laser in treating hypertrophic scars.Methods：1. Establish the hypertrophic scar models on rabbit ear in20rabbits. Five squarewounds（1×1cm）with whole-skin and perichondrium defect with interval of1cm oneach ventral side with local anesthesia，kept the cartilage,the wounds were exposedand changed the iodine on wound once a day.Hypertrophic scars were observed withinthree weeks.2.One side was set as the treatment group of fractional CO₂laser while the other side asthe control group randomly.The treatment group were treated with fractional CO₂laser（DeepFX,fluence:20.0mJ,frequency:300Hz,Shape:2,Size:10,Pulses:2,Density:5%）after epithelialization（three weeks after the surgery）,the control group got no specialtreatment. Reserve two rabbits without doing anything.3.Take photos on day1,3,7,14,28after the laser treatment group got the lasertreatment and cut off the scar specimen. HE dying show the patten, density of thefibroblasts, capillary hyperplasia and collagen arrangement. To detect the the chang ofthe fibroblasts apoptosis rate with TUNEL and the chang of VEGF with ElivisionTMplus immunohistochemical method.Save two rabbits without tests after the lasertreatment and observe the wound healing process.Results: 15rabbits were survived from the experiment.The epithelization time of the woundswas3weeks,and gained150hypertrophic scars.1.General observation: The color and luster of scar became lighter after the lasertreatment one week later, the thickness reduced and the scars became smoother. Itneeded about50.90±2.28days that the scar became thinner and smoother in thetreatment group while it needed69.00±2.10days in the control group.2. The changes of scar tissue structures: The hypertrophic scar was about3-4timesthicker than the normal skin under microscope.Plenty of fibroblasts and microvesselswere observed,thick and tight collagen fibers were seen in the superficial layer ofdermis with an irregular arrangement. From the14days after the laser treatment, thefibroblasts, microvessels and collagen fibers observed to decrease obviously.3. The detection of fibroblast apoptosis rate with TUNEL.:The apoptotic cells wereobserved in fibroblasts, keratin cells and endothelial cells. The apoptotic cells weregradually increasing in hypertrophic scars in the control group, but the apoptotic cellsin treatment group were much more than the control group,and increased after thelaser treatmen immediately（P＜0.05）.4.The changes of VEGF expression：The VEGF in hypertrophic scars decreasedobviously after the laser treatment for7,14,28days comparing to the control group（P＜0.05）.VEGF began to decrease obviously on day28in the control group.Conclusion：1.The fractional CO₂laser can promote the hypertrophic scars become soft andsmooth on rabbit ear.2. The treatment of fractional CO₂laser on hypertrophic scars in the rabbit earmodel can promote fibroblast apoptosis, decreasing the expression of VEGF.3.One of the mechanism of fractional CO₂laser on treating hypertrophic scarsin the rabbit ear model perhaps is promote fibroblast apoptosis, decrease the expression of VEGF.