Update: Mechanisms of Topical Retinoids in Acne

Topical retinoids are the cornerstone of current acne management due to their actions on multiple facets of acne pathophysiology. Retinoids are a family of compounds that structurally and functionally resemble vitamin A, an essential nutrient with a key role in cellular growth and differentiation. In the skin, retinoids exert their effects by binding retinoic acid receptors (RARs) in the cell nucleus with subsequent regulation of gene transcription. There are three subtypes of RARs, and the topical retinoids currently approved for acne have differing receptor binding profiles which may translate to clinical differences, since the specific RAR subtypes activated dictate the biological response of target cells. The activity of a retinoid depends on cellular transport, receptor-binding pattern and affinity, and the genes activated. This review discusses physiologic pathways in skin that are affected by topical retinoids during acne therapy, with a focus on new data from trifarotene, a retinoid which is highly selective for the RAR-y receptor. Recently, bioinformatic data comparing gene expression in acne lesions treated with trifarotene versus spontaneously resolving acne lesions showed that trifarotene significantly modulates 67 genes that do not appear in the spontaneously resolving lesion. These genes are involved in cellular migration, activation of adaptive immunity, inflammation, and matrix reorganization. Expression of these trifarotene-regulated genes after treatment and in an active lesion occurred in opposite directions, providing clues to the molecular and genetic response to trifarotene in resolving acne.