| ObjectiveAfter Intense pulsed light irradiation cavia cobaya skin, to evaluate the histological change of skin with HE stains; to evaluate the collagen fiber change with nitroxanthic acid stains; to quantitative analysis of hydroxyproline content. Confirm mechanism of action for Intense pulsed light on sun-damaged human skin.MethodsSelected 15 cavia cobayas. Each of back skin was divided into irradiation areas and non-irradiation areas randomly. Treatment parameters were 640-1200nm wavelength, single-stacked pulse with fluences of 30J/cm~2, pulse duration 5 milliseconds. At day 1, 8, 15, 30 and 45 after irradiation. Skin specimens were respectively taken at irradiation areas and non-irradiation areas, sizes were 5mm×5mm×3mm. To evaluate the histological change of skin with HE stains; to evaluate the collagen fiber change with nitroxanthic acid stains; to quantitative analysis of hydroxyproline content.ResultsMacroscopic observation: At day 1 after irradiation, there were three cavia cobaya irradiation areas occurring transient erythema, which lasted for 2 days. There were no hyperpigmentation, no purpura, no blister, no swelling and so on. From the day 15 after irradiation, irradiation areas skins became smooth and exquisite, non-irradiation areas skins were no marked change.Our results revealed that HE stains at irradiation areas at day 1 after irradiation, structure of epidermis layers were integrated, the appearance of epidermis and dennis junction was integrity, there was no inflammatory infiltrate at papillary layer of dermis, the structure of hair follicles were normal. The number and appearance of blood vessels were normal, endotheliocytes were no swelling. At day 8 after irradiation, the number of melanocytes at basal layer decreased, dermal depth was increased, there were no neutrophils infiltrated in the dermis, the number of fibroblasts were increased. At day 15, 30 and 45 after irradiation, the number of fibroblasts were increased. The fibroblast cytoblasts were larger and well-stacked. Collagen fibers at the irradiation areas were lined up in order and intensive. The histology of non-irradiation areas were no changed.At day 1 after irradiation, nitroxanthic acid stains showed that the appearance of collagen fibers at irradiation areas and non-irradiation areas were no significant difference. At day 8 after irradiation, collagen fibers at irradiation areas were much more intensive than at non-irradiation areas. The number of fibroblasts at irradiation areas became larger and larger. At day 15, 30 and 45 after irradiation, the number of fibroblasts at irradiation areas were much larger than non-irradiation area. There were orderly-arranged collagenous fibers.Hydroxyproline content assaying: The contents of hydroxyproline at irradiation areas at day 8 after irradiation (10.50±3.35ug/mg) were much more than day 1 (6.72±5.65ug/mg), but much less than day 15 after irradiation (21.03±11.51ug/mg). At irradiation areas, from day 1 to day 15 after irradiation the hydroxyproline contents were gradually increasing. From day 30 and day 45 after irradiation, the hydroxyproline contents were gradually decreasing. But at day 45 after irradiation the hydroxyproline contents were also much more than day 1 after irradiation. Time effective showed that as the time went on, the contents of hydroxyproline at irradiation areas changed. There was significance difference (F=3.364, P＜0.05). Hydroxyproline contents of the irradiation areas were more than non-irradiation areas, the difference was significance difference (F=34.254, p＜0.001).ConclusionIntense pulsed light could induce fibroblast proliferation, collagen formation and increased. It achieved clinical improvement and skin rejuvenation. In addition, the effect of intense pulsed light on sun-damaged human skin was time limited, It provided a theoretical basis of mechanism, course of therapy and interval time for Intense pulsed light on sun-damaged human skin. |
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