| Objective: To observe the effects of Q-switched Nd:YAG laser(wavelength 1064 nm,hereinafter referred to as Q-1064nm)on thermal injury and pigmentation in skin tissue of pigmented guinea pigs treated with cold compress at different temperatures.By observing the changes of molecular mechanism,the significance of different cold compress temperature on skin protection after laser surgery was preliminarily explored,which provided guidance and certain theoretical basis for clinical treatment of skin pigment-related diseases after laser treatment.Methods: 10 brown and yellow guinea pigs were selected as experimental objects.The areas of brown and yellow hair on the back of guinea pigs were selected to remove the hair and expose the skin.The pigmentation was induced by exposure to the bare skin of the guinea pig back by using(narrow band ultraviolet,B)NB-UVB(irradiation parameter:0.9J/cm,once a week).A total dose of 2.7J/cm was given to each guinea pig for three weeks.After the color sink was formed,the area was treated with Q-1064 nm laser.The energy density was 5.0J/cm and the light spot diameter was 4 mm.After treatment with Q-1064 nm laser,each guinea pig was divided into three regions from left to right and randomly divided into three groups.The 0? group was 0? ice for 20 min immediately after laser therapy.The8? group was immediate 8? cold compress 20 min after laser therapy.In the control group,no treatment was given after laser therapy.All treatment was performed at room temperature(20-23?).Before and after the formation of pigmentation,immediately,1 week and 2 weeks after the laser treatment of skin cooling,the skin tissue was taken immediately,1 week and 2 weeks.Gross changes in the skin of guinea pigs were observed with the naked eye,the samples were stained with HE staining,Fontana-Masson staining,heat shock protein 70(HSP 70)and ?-melanocyte stimulating hormone(?-MSH)immunohistochemical staining.To evaluate the changes of tissue structure,HSP70,melanin granules and ?-MSH expression in guinea pigs after skin cooling after laser treatment.Results:The skin changes of guinea pigs were observed with naked eye.The skin of guinea pigs was dark brown after NB-UVB irradiation and the color distribution was uniform.After immediate cold compress of Q-1064 nm laser therapy,the skin color of the 3 groups was slightly red.A small amount of erythema was found in the skin tissue of the control group.There was no obvious erythema in the 0 ? group and 8 ? group,and the degree of redness was lighter than that of the control group.The exfoliated area of callus in 0?group and 8?group was larger than that in control group at 1 week.At2 weeks,the skin color of 0? group and 8? group was lighter than that of the control group,and the skin color was closer to the normal skin color.1 cold compress and thermal damage repair1.1 HE tissue sections observed by he staining showed that the cells in the control group were disordered at 1 week,and some of the cells were vacuole-like,which could not distinguish the epidermis cells from each other.Red blood cell overflow and inflammatory cell infiltration could be seen in the tissue.The cells of 0? group and 8? group were arranged more neatly than that of the control group,and the epidermal hierarchy could be distinguished.Inflammatory cell infiltration was observed in 0? group and 8? group,but no red blood cells were found in 0? group and 8? group.After 2 weeks of treatment,tissue cell arrangement,red blood cell overflowthe,the number and distribution of inflammatory cells in skin tissue were improved as compared with those in 1 week after treatment.The cells in skin tissue of 0 ? group and 8 ? group were arranged neatly,a small number of inflammatory cells were found,and no red blood cells were found.The number of inflammatory cells in the control group was more than that in the 0 ? group and 8 ?group,and a small amount of red blood cells could be seen in the control group.1.2 Immunohistochemical staining showed that the expression of HSP 70 in0 ? group and 8 ? group was lower than that in control group at 1 and 2weeks,and the difference was statistically significant(P<0.05).There was no difference between 0? group and 8? group at 1 week(P>0.05),but the expression level in 8? group was higher than that in 0? group at 2 weeks(P<0.05).There was interaction between time and group.2 Cold compress and pigmentation changes2.1 F-M staining showed that the amount of melanin granules in exposed skin of guinea pigs after ultraviolet irradiation was significantly higher than that before irradiation,and the content of melanin particles was significantly different before and after ultraviolet irradiation(P < 0.05).After 2 weeks of cold compress,the expression of melanin granules in the 3 groups was lower than that in the first week.The expression of melanin granules in 8? group and 0? group was significantly lower than that in control group(P<0.05).The expression levels in 8? group were significantly lower than that in 0?group(P<0.05).2.2 The expression of ?-MSH by immunohistochemical staining showed the same trend as that of melanin granules.At 1 week,2 weeks after cold compress,the expression of ?-MSH in 8? group and 0? group was lower than that in control group(P < 0.05),and the expression of ?-MSH in 8 ?group was lower than that in 0? group at the same time(P<0.05).Conclusions:1.Immediate contact skin cooling after Q-1064 nm laser treatment of pigmented skin can reduce the thermal injury caused by laser therapy and promote the repair of injured tissue.2.After the treatment of pigmented skin diseases with Q-1064 nm laser,immediate contact skin cooling could reduce epidermal melanin,which has the effect of synergistic laser to reduce pigmentation.3.The effect of 8? cold compress was better than 0? ice compress onskin protection of pigmented skin diseases treated by Q-1064 nm laser. |
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