| Objective:The Q switch 1064 nm neodymium-doped yttrium aluminum garnet laser(Nd: YAG)has been widely used in treating coffee spots,sunburn spots,freckles,chloasma,moles of ota and other skin pigmentation diseases.In clinical practice,it has been observed that Epidermal growth factor(EGF)gel has a certain effect on laser treatment of pigmentation,but the specific mechanism is rarely reported.In this study,a Q-switched 1064 nm Nd: YAG laser(Nd: YAG)combined with Epidermal growth factor(EGF)gel for local topical application was used to treat skin pigmentation in the brown-yellow area on the back of guinea pigs caused by narrow spectrum ultraviolet(NB-UVB).To investigate the inhibitory effect of QS1064nmNd: YAG laser therapy combined with external gel containing epidermal growth factor on UVB-induced skin pigmentation in guinea pigs.Methods:10 healthy guinea pigs(clean grade)were selected,which were female,200-250 g by weight,1-2 months by age.Hair area on the back of guinea pigs with rown color was depilated to expose the skin.Narrow band ultraviolet(NB-UVB)was used to irradiate the skin,and the focal length should be adjusted to make the two red indicators coincide before irradiation.The dose of irradiation was based on the minimal erythema dose(MED)of the preliminary experimental results,i.e.900mJ/cm2,1 time per week,3 times in total,with a total dose of 2700mJ/cm2.The skin in the modeling area was divided into three groups after the successful establishment of the models where we take the head orientation of each guinea pig as the top,and the skin was divided into three groups of A,B and C from left to right with different treatment.Group A: The middle area was blank control group A without treatment after successful modeling.Group B: The left area treated with EGF-free gel was placebo control B: Q switch 1064nmNd: YAG laser irradiation,with spot diameter of 4mm and energy density of 2.0J/cm2.The gel was scanned once.The placebo gel without EGF was uniformly applied to the area of group B immediately after laser treatment with thickness of about 2mm Once a day for ten days.Group C: The area on the right was treated as the experimental group C: Q switch 1064nmNd: YAG combined with EGF gel: Q switch 1064nmNd: YAG laser irradiation,spot diameter of 4 mm,energy density of 2.0 J/cm2,scanned once,and the EGF gel was uniformly applied to the area of group C immediately after the laser treatment with the thickness was about 2mm Once a day for ten days.The general assessment of pigmentation was taken by photography before and after modeling with laser irradiation of Q switch 1064nmNd: YAG for 2 and 4 weeks in each group.Pathological sections were made to observe the epidermal pigmentation,melanin particle synthesis and c-kit protein expression via melanin particle staining(Fontana-Masson silver staining)and stem cell factor receptor(c-kit)immunohistochemical staining for investigate the inhibitory effect of QS1064nmNd: YAG combined with topical EGF-containing gel on UVB-induced pigmentation in guinea pig skin.Results1.Changes of skin pigmentation were observed by naked eyesThe skin in the irradiation area on the back of guinea pigs became significantly darker,while the pigmentation was evenly and stably distributed after NB-UVB irradiation,.Group A: Untreated group: Slightly decreased skin color was observed in group A at 2 and 4 weeks after treatment,but more pigmentation was still observed in normal skin tissues.Group B: Placebo group: Observed skin color at 2 and 4 weeks after treatment was significantly reduced compared with group after modeling,which was similar to the color of normal skin tissue.Group C: EGF experimental group: Skin pigmentation was observed to be significantly decreased at 2 and 4 weeks after treatment compared with group after modeling,while there was no significant difference observed between the two groups compared with normal skin color.2.Melanin granule changesFontana-Masson silver staining method showed that the content of black particles in guinea pig skin was significantly increased after NB-UVB irradiation,and the content difference of melanin particles before and after modeling was statistically significant(P<0.05).At week 2 and 4 after treatment,the content of melanin particles in group B and group C was significantly lower than that in group A during the same period,and the difference was statistically significant(P<0.05).At 2 weeks after treatment,the content of melanin particles in group C was slightly lower than that in group B,but the difference was not statistically significant(P>0.05).At week 4,the content of melanin particles in group C was lower than that in group B,and the difference was statistically significant(P<0.05).The content of melanin granules in the skin of each group at different time was compared at week 2 and week 4 after treatment,and the difference between the two groups was statistically significant(P<0.05).There is an interaction between time and block factors.3.Changes in c-kit protein expression levelAfter NB-UVB irradiation,the expression intensity of c-kit in guinea pig skin was significantly enhanced,and the expression level was significantly increased.The difference in c-kit expression before and after modeling was statistically significant(P<0.05).At week 2 and 4 after treatment,c-kit expression in group B and group C was significantly lower than that in group A during the same period,and the difference was statistically significant(P<0.05).At 2 weeks after treatment,c-kit expression in group C was slightly lower than that in group B,but the difference was not statistically significant(P>0.05).At week 4,c-kit expression in group C was lower than that in group B,and the difference was statistically significant(P<0.05).Conclusion:1.It is confirmed that QS1064nmNd:YAG has an effective effect on UVB-induced pigmentation of guinea pig skin.2.External use of epidermal growth factor-containing gel can improve the efficacy of QS1064nmNd: YAG laser in the treatment of UVB-induced skin pigmentation in guinea pigs.3.The mechanism of reduction of skin pigmentation with external use of recombinant human epidermal growth factor gel may be related to the decreased expression of c-kit in guinea pig skin after Q switch 1064nmNd:YAG treatment,thereby inhibiting the maturation of melanocytes and the synthesis of melanin particles. |
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