Effect Of Long-pulsed 1064 Nm Nd:YAG Laser On Hypertrophic Scar In Rabbit Model

Objective: Conservative treatments have been advocated for early hyperplastic hypertrophic scars, including pharmacotherapy (topical and intralesional corticosteroids, interferon, 5-fluorouracil), pressure therapy, silicone cream or gel application, radiation therapy and laser therapy. Unfortunately, all the treatments modalities had side-effects, and lasers therapy had been shown to be effective, less injuries, less adverse effects, lasers therapy became one of preferred treatments. The Pulsed Dye Laser were blood vessels targeted laser, they used in treat human hypertrophic scar for a long time and they were effected, but they have some limitations like pigment alteration, less penetration. The 1064nm Nd:YAG laser heated the blood vessel more slowly, had greater skin penetration(>5mm) and absorption by melanin located in the epidermis is relatively low that could avoid the vessel blasting, developing purpura and dyspigmentation.Currently, the long pulsed 1064nm Nd:YAG laser used to treat different vascular lesions. We suspected that long pulsed 1064nm Nd:YAG laser can also block the blood vessel of early hypertrophic scar, inhibit fibroblasts proliferation and collagen hyperplasia, then promote early hypertrophic scar shrink. The objective of our study is to investigate the effect of Long-pulsed 1064nm Nd:YAG laser in treating hypertrophic scars of rabbit ears.Methods:Ten new Zealand White rabbits (half of male, half of female ,weighting 2.0-2.5 kg) were made animal models of hypertrophic scars. All surgical operations were performed under aseptic conditions and ketamine/xylasine (0.2 ml/kg intramuscular) anesthesia. Four 1.5-cm square dermal ulcer wounds were created on the ventral surface of each ear with remove of the perichondrium. Nothing was applied to the wounds and they were covered by sterile gauze for one day. On the seven day of postoperative day we abscised the scab. On the twenty fifth to twenty eighth of postoperative day, 74 wounds developed hypertrophic scar successfully.The left ears of rabbits were treatment group that received long-pulsed 1064nm Nd:YAG laser treatment and the right ears were the control group that received no special treatment. 4 weeks after laser treatment, we observed the erythema and texture of the scars and Color-Doppler was used to measure the thickness of the scars. Then the scars were harvested for histological staining and immunohistochemistry staining. The capillaries, fibroblasts and collagen fibers were observed in histopathologic examinations and biochemical studies.Results: Compared with the control group, the scar redness, texture of treatment group had improved. The mean scar thickness values of treatment group was 0.3089cm compare to 0.2137㎝ of the control group, t value = 5.72,P< 000.1<0.05, the difference was significant, the scar of treatment group was thinner than the control group. The mean quantity of capillaries of treatment group was 68.056/mm2 compare to 38.333mm2 of the control group, t value = 4.93, P< 000.1<0.05, the difference was significant, the quantity of capillaries in the treatment group was lower than the control group. The mean amount of fibroblasts in the treatment group was 355.000/mm2 compare to 166.940/mm2 of the control group, t value =13.36, P< 000.1<0.05, the difference was significant, the density of fibroblasts in the treatment group was lower than the control group. The laser treatment group was observed to possess a more organized, loosened collagen structure compare to control group in Masson stain.Conclusions:1 Long-pulsed 1064nm Nd:YAG laser can improve the color, thickness and texture of hypertrophic scar. The color gradually fades, the thickness became thinner, the texture became softer. 2 Long-pulsed 1064nm Nd:YAG laser can block the blood vessel of the early hypertrophic scar .3 After Long-pulsed 1064nm Nd:YAG laser treatment, the density of fibroblasts decreased, the collagen fiber became regular and looser.4 Long-pulsed 1064nm Nd:YAG laser may promote scars shrink.It provides a new treatment option for early hypertrophic scar.