Effects of Intense Pulsed Light and Ultraviolet A on Metalloproteinases and Extracellular Matrix Expression in Human Skin

OBJECTIVE: The aim of this study was to evaluate the effects of intense pulsed light (IPL) and ultraviolet A (UVA) irradiation on the expression of matrix metalloproteases (MMPs), tissue inhibitor of metalloproteinase 1 (TIMP-1), and extracellular matrix (ECM) in human skin, and to confirm the relative mechanism. BACKGROUND DATA: IPL has been widely used to treat photoaged skin but the underlying mechanism remains unknown. METHODS: Human buttock skin was irradiated by repetitive suberythemal doses of UVA and therapeutic doses of IPL. Skin biopsies were taken and the protein/mRNA expression of MMP-1, -3, -9, and -12 and TIMP-1 was examined by immunohistochemistry, image analysis, and real-time quantitative polymerase chain reaction (qRT-PCR). RESULTS: Compared with normal control skin, both IPL and UVA irradiation induced a general elevation of MMP-1, -3, -9, and -12 and TIMP-1 at protein/mRNA levels, with some differences in the MMP expression patterns, e.g., a remarkable increase of MMP-1, -3, and -12 in UVA-exposed skin, while lower MMP-1, -3, and -12 (p < 0.01, p < 0.01, p < 0.01) but higher MMP-9 (p < 0.05) levels in IPL-irradiated skin. Meanwhile, increased collagen I fibers (p < 0.05) were observed in IPL-irradiated skin, whereas fragments of elastic fibers were found in UVA-exposed skin. CONCLUSION: These findings demonstrated that IPL has similar effects on the expression of MMPs/TIMP-1 in human skin to UVA, but the expression pattern differed from that in UVA-exposed skin, which may account for IPL's photorejuvenation effects.