Efficacy Of Low Fluence Fractional Q-Swich Rubystar Laser And Topical Tranexamic Acid Treatment Of Pigmentation Of Brownish Guinea Pig Model

Objective:Fractional Q-Swich RubyStar Laser (QSRL) has been successfully applied in the treatment of pigmentation disorder. Tranexamic acid treatment of pigmentary diseases has been widely used, but the combind fractional QSRL with tranexamic acid treatment has not been reported. Our research adopts the Q-switched Ruby Laser fractional mode combined topical tranexamic acid,to investigate the effectiveness and safety of and topical tranexamic acid (TXA) on narrow band ultraviolet B(NB-UVB)-induced pigmentation in Guinea pigs. Value the changes of general evaluation, melanin cells, melanin particles expression, prove the validity of this method in treatment of pigmentation disease and its possible mechanism.Methods:10healthy guinea pigs (clean animal) to develop experimental models, female, aged1month to2month.Tan skin exposured to NB-UVB light, exposure dose based on minimal erythema dose (MED) from the preliminary experimental result for900mJ/cm2,1times a week, a total of3times, total dose2700mJ/cm2.Separate uniform pigmentation skin into four groups:Group A:No treatment.Group B:Topical tranexamic acid treatment:Tranexamic acid diluted to5ml/50ml,then infltrated dressing banded it to skin,kept the concentration for3days,1times a week,a total of2timesGroup C:Fractional QSRL with Tranexamic acid treatment:Spot diameter7.1mm, the fluence2.5J/cm2, scanned it for once, after laser treatment,tranexamic acid diluted to5ml/50ml,then infltrated dressing banded it to skin,kept the concentration for3days.1week treatment, a total of2times.Group D:Fractional QSRL treatment:Spot diameter7.1mm, the fluence2.5J/cm2, scanned it for once,1week intervals,a total of2times.Apply visual estimation pigment、melanocyte staining (Imokawa method) and melanin granules staining (Masson-Fontana) to observe the changes of melanophore and melanin granules respectively.Results:1Pigmentation changesAfter completion of NB-UVB irradiation, the pigmentation of irradiation areas changed to hyperpigmentation, uniform and stable.Group A:No treatment group:Hyperpigmentation has decreased than the model, but to the normal skin tissue, it was still heavy.Group B:Topical Tranexamic acid treatment:Hyperpigmentation has decreased than the model, but to the normal skin tissue, it was still heavy.Group C:Fractional QSRL irradiation combined tranexamic acid treatment:Pigmentation significantly reduced compared with model skin, similar to normal skin tissues.Group D:Fractional QSRL treatment:Pigmentation reduced significantly compared with model skin, similar to normal skin tissues.2Melanin cell changes2.1Morphological changeNormal skin melanocytes are poles, minority is multipolar dendritic protrusions, cell body is long and narrow,after NB-UVB irradiation, the melanocytes’body grew and truned round,dendritic protrusions increased.After fractional QSRL treatment, melanocyte body getting smaller than before, dendrites reduced. No treatment group and tranexamic acid treatment group the melanocytes’form had no obvious change.2.2Number changesAfter completion of NB-UVB exposure, exposured area melanocytes number increased obviously than normal skin.Group A:No treatment group:melanin cell number has decreased compare with the model, but with the normal skin tissue, numbers are still increasing.Group B:Tranexamic acid topical treatment:Melanin cell number is decreased than the model, the number is still increasing than the normal skin tissue.Group C:Fractional QSRL irradiation combined tranexamic acid treatment:The melanin cell number decreased significantly compared with the model. The number is more than normal skin tissues.Group D:Fractional QSRL treatment:The melanin cell number decreased significantly compared with the model,the number is more than normal skin tissues.3Melanin granules changesMelanin granules of normal skin is seen in basal cell and stratum spinosum occasional, after NB-UVB irradiation, model area melanin particles significantly increased, melanin particles and more melanin capcan be found full-thickness densely of epidermisGroup A:No treatment group:Part of skin’s melanin granules decrease than the model, just basal cell and stratum spinosum visible continuous melanin particles strip, part is still the hole epidermal layer with the black pigment particles.Group B:Tranexamic acid topical treatment:Part of skin’s melanin granules decrease than the model, just basal cell and stratum spinosum visible continuous melanin particles strip, part is still the hole epidermal layer with the black pigment particles.Group C:Fractional QSRL irradiation combined tranexamic acid treatment:2weeks after treatment, melanin granules reduced significantly than the model, it’s decreased too compared with normal skin. But after4weeks, gradually restored, and close to normal skin.Group D:Fractional QSRL treatment:2weeks after treatment, melanin granules reduce significantly than the model, compared with normal skin,it’s decreased,But after4weeks, the melanin granules gradually restored, and close to normal skin.By analasying the statistic of pigmentation scores、melanocyte numbers、 melanin area and epdermal area ratio, low fluence fractional QSRL treat pigmentation effectively (P<0.05). Topical tranexamic acid treatment is uneffective to pigmentation(P>0.05). Combined fractional QSRL and tranexamic not superior to fractional QSRL alone (P>0.05).Conculsion:1Low fluence fractional QSRL is a safe and effective treatment of NB UVB induced guinea pigs’pigmentation,maybe it plays a role by reducing the melanocyte melanin particles.It did not see obvious recurrence for a month follow-up.2Tranexamic acid topical treatment of pigmentation is invalid to change the melanin cell and melanin corpuscle3Both joint action needs further research to explore.