Multifaceted amelioration of cutaneous photoageing by (0.3%) retinol
Kieran T. Mellody, Eleanor Bradley, Bezaleel Mambwe, L. Cotterell, Orsolya Kiss, Poonam Halai, Zeena Loftus, Mike Bell, Tamara Griffiths, C.E.M. Griffiths, Rachel Watson
Abstract
Abstract Background Although retinol skin care products improve the appearance of photoaged skin, there is a need for an effective retinol concentration that provides skin benefits without irritation. Objective To compare the efficacy of topical 0.1%, 0.3% and 1% retinol in remodelling the cutaneous architecture in an in vivo experimental patch test study, and to determine tolerance of the most effective formulations when used in a daily in‐use escalation study. Methods For the patch test study, retinol products were applied under occlusion, to the extensor forearm of photoaged volunteers ( n = 5; age range 66–84 years), and 3 mm skin biopsies obtained after 12 days. Effects of different retinol concentrations, and a vehicle control, on key epidermal and dermal biomarkers of cellular proliferation and dermal remodelling were compared to untreated baseline. Separately, participants ( n = 218) recorded their tolerance to 0.3% or 1% retinol over a six‐week, approved regimen, which gradually increased the facial applications to once nightly. Results Retinol treatment induced a stepwise increase in epidermal thickness and induced the expression of stratum corneum proteins, filaggrin and KPRP. 0.3% retinol and 1% retinol were comparably effective at inducing keratinocyte proliferation in the epidermis, whilst reducing e‐cadherin expression. Fibrillin‐rich microfibril deposition was increased following treatment with 0.3% and 1% retinol ( p < 0.01); other dermal components remained unaltered (e.g., fibronectin, collagen fibrils, elastin), and no evidence of local inflammation was detected. The in‐use study found that 0.3% retinol was better tolerated than 1% retinol, with fewer and milder adverse events reported (χ 2 (1) = 23.97; p < 0.001). Conclusions This study suggests that 1% and 0.3% retinol concentrations were similarly effective at remodelling photodamaged skin in an in vivo model of long‐term use. Use of 0.3% retinol in the escalation study was associated with fewer adverse reactions when applied daily. Hence, 0.3% retinol may be better tolerated than 1% retinol, thereby allowing longer‐term topical application.