¹Department of Dermatology, University of Michigan Medical School, Ann Arbor, Michigan, USA

Correspondence: Dr Gary J. Fisher, Department of Dermatology, University of Michigan Medical School, 1301 Catherine, Medical Science I, Room 6447, Ann Arbor, Michigan 48109-0609, USA. E-mail: dianemch@umich.edu

²Authors contributed equally to this manuscript

Received 14 November 2008; Accepted 8 January 2009.

Abstract

UV radiation from the sun impacts skin health adversely through complex, multiple molecular pathways. Premature skin aging (photoaging) is among the most widely appreciated harmful effects of chronic exposure to solar UV radiation. Extensive damage to the dermal connective tissue is a hallmark of photoaged skin. Disruption of the normal architecture of skin connective tissue impairs skin function and causes it to look aged. UV irradiation induces expression of certain members of the matrix metalloproteinase (MMP) family, which degrade collagen and other extracellular matrix proteins that comprise the dermal connective tissue. Although the critical role of MMPs in photoaging is undeniable, important questions remain. This article summarizes our current understanding of the role of MMPs in the photoaging process and presents new data that (1) describe the expression and regulation by UV irradiation of all members of the MMP family in human skin in vivo and (2) quantify the relative contributions of epidermis and dermis to the expression of UV irradiation-induced MMPs in human skin in vivo.