Protective effects of adipose-derived stem cells against UVB-induced skin pigmentation

Background: Hyperpigmentation, mainly following UV-irradiation, can cause major cosmetic concerns. Human adipose tissue-derived stem cells (ASCs) have been reported to serve as whitening agents through a paracrine effect. However, there have been few reports on the direct effects of ASCs on skin pigmentation following UVB-irradiation. Methods: To evaluate the effect of ASCs on UVB-irradiated mouse skin, UVB-irradiation alone was applied to one side of the backs of mice (melanin-processing hairless mouse, HRM-2) as a control, and UVB-irradiation plus injection of ASCs was applied to the contralateral side. Skin pigmentation and histology were evaluated and the number of DOPA-positive melanocytes in the mouse skin was counted. The absolute value of Delta L* via a colorimeter was measured to evaluate the degree of skin pigmentation. The effects of ASCs on the melanogenic activities of mouse skin were examined by measuring the tyrosinase activity and the melanin contents in the epidermis of the mouse skin. Results: Skin pigmentation was suppressed in the ASC-injected side. Moreover, the change in skin thickness following UVB irradiation was reduced in the ASC-injected side. The number of DOPA-positive melanocytes in the ASC-injected side (139 +/- 18 cells/mm(2)) was significantly lower than that in the control side (239 +/- 48 cells/mm(2)). The tyrosinase activity (67.4 +/- 9.8% of that of the control side) and melanin content (63.4 +/- 5.7% of that of the control side) of the ASC-injected side were also significantly reduced. Conclusions: Collectively, these results suggest that ASCs injected subcutaneously into the backs of mice can attenuate tanning following UVB-irradiation, through suppression of tyrosinase activity.