The role of retinoids in the prevention and repair of aged and photoaged skin

Retinoids, either naturally occurring or synthetic, are defined by their ab ility to bind nuclear retinoid receptors of the steroid/thyroid superfamily . Their protean but key function in physiology is control of cellular proli feration and differentiation. Topical retinoids, namely tretinoin, have bee n proven to prevent and repair clinical features of photoageing; these proc esses are facilitated by an ability to prevent loss of collagen from, and s timulate new collagen formation in, the papillary dermis of sun-exposed ski n. Emerging evidence indicates that intrinsic, chronological ageing of the skin shares several mechanistic features with photoageing. Indeed aged skin is characterized by retinoid sensitivity and is probably reparable by appl ication of topical retinoids.