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Ultraviolet ��UV�� irradiation has harmful effects on human skin. Photoaging is currently considered as a primary harmful effect of chronic solar UV exposure. UV irradiation can induce increased expression of certain members of the matrix metalloproteinase ��MMP�� family, which in turn degrade dermal collagen and other extracellular matrix ��ECM�� proteins, then lead to the disruption of normal architecture of skin connective tissue followed by the impairment of skin function and aging of skin. Tissue inhibitors of metalloproteinases��TIMPs�� are considered as the specific endogenous inhibitor of matrix metalloproteinases ��MMPs��, and participate in the regulation of MMP activity. The balance between MMPs and TIMPs plays an important role in the occurrence and development of skin aging.