Multifaceted amelioration of cutaneous photoageing by (0.3%) retinol

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. Retinol 0.3% and 1% 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% was better tolerated than 1% retinol, with fewer and milder adverse events reported (χ2 (1) = 23.97; P < 0.001).

CONCLUSIONS: This study suggests that 1% retinol 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.