Experimental Study Of Matrix Metalloproteinase-1（MMP-1） Activity And Hydroxyproline Content After Ultrapulsed Fractional CO₂Laser Treatment In Hypertrophic Scar Of Rabbit Ear

ObjectiveTo observed the changes about the activity of MMP-1and the content ofhydroxyprline-free after the treatment of ultrapulsed fractional CO2laser in hypertrophicof rabbit ears.To explore the collagen degradation after ultrapulsed fractional CO2lasertreatment. To provide the effective evidence of hypertrophic scar treated by ultrapulsedfractional CO2laser and to find the evidence of increasing collagen catabolism afterfractional treatment.MethodsDivided rabbits into three groups:①laser treatment group: scars only treated byfractional CO2laser;②the control group of hypertrophic scar: no treatment aftermodeling;③normal skin group: autologous rabbit ear ventral skin. On the28thday aftermodeling, the hypertrophic scars in laser treatment group were treated by fractional CO2laser. In the1st,2nd,3rd,4thand5thweeks after treatment, hypertrophic scars or rabbit earventral skin of12rabbits in each group were biopsy.ResultsAfter the treatment of fractional CO2laser, the activity of MMP-1in hypertrophicscar increased gradually, but lower than normal skin, higher than the control group ofhypertrophic scar(P<0.001). The MMP-1activity in the control group of hypertrophicscar decreased significantly with time-bound. The MMP-1activity in laser treatmentgroup increased significantly compared with the control group (P<0.001), peaked at the3rdweek, then the activity of MMP-1decreased. At the5thweek, the activity of MMP-1was still higher than the control group (P<0.001).The content of free hydroxyproline was constant with time-bound in the normal skingroup. And the contents of free Hydroxyproline in the control group reduced withtime-bound, and at the5thweek, the content of free Hydroxyproline was no significantlydifferent with the normal skin group(P>0.05). The content of free Hydroxyproline in thelaser treatment group were increased with time-bound, peaked in the3rdweeks after treatment, then the content was decreased. The content of combined Hydroxyproline innormal group was constant with time-bound. While the content of combinedHydroxyproline in the control group was decressed with time-bound, but it’s decreasedvery slow. At the1stweek, the content of combined Hydroxyproline in control group was3times more than normal group. The content of combined Hydroxyproline in lasertreatment group after treated by ultrapulsed fractional CO2laser was significantlydecreased. In the5thweek, the content of combined Hydroxyproline in laser treatmentgroup was1.5times more than normal group.Conclusion1. Ultrapulsed fractional CO2laser treatment can promote the activity of MMP-1and thecollagen dagradation in hypertrophic, increase collagen degradation and the contentof free Hydroxyproline, decrease the content of collagen.2. One of the mechanisms of fractional CO2laser on treating hypertrophic scars is thethermal decomposition of this treatment can release MMP-1from scar fibroblasts aswell as the controllable thermal injury of this treatment can promote the activity ofMMP-1, increase collagen degradation and the content of free Hydroxyproline,decrease the content of collagen.