Importance: Topical formulations of tretinoin precursors (retinol and its ester derivatives) are widely available over the counter and may offer similar clinical benefits to those of tretinoin for treatment of photoaging. However, which of the many purported molecular effects of retinoids most strongly drives clinical improvements in tretinoin-treated skin remains unclear.
Objectives: To evaluate the clinical efficacy of topical tretinoin precursors (TTP) vs tretinoin (RA) in treating moderate to severe facial photodamage and to identify potential biomarkers that correlate with clinical efficacy.
Design, setting, and participants: This randomized, double-blind, single-center, parallel-arm study of 24 patients with moderate to severe facial photodamage was conducted at an academic referral center from November 2010 to December 2011, with data analysis performed from January 2012 to December 2021.
Interventions: Daily topical application of 0.02% RA or 1.1% TTP formulation containing retinol, retinyl acetate, and retinyl palmitate for 24 weeks.
Main outcomes and measures: Photoaging and tolerability were assessed by dermatologist evaluations and patient-reported outcomes. Target gene expression was assessed by real-time quantitative polymerase chain reaction of biopsied tissue from treated areas.
Results: A total of 20 White women were ultimately analyzed (9 randomized to TTP, 11 randomized to RA). At week 24, there was no significant difference in Griffiths photoaging scores among patients receiving TTP vs RA (median, 4 vs 5) (TTP - RA difference: -1; 95% CI, -2 to 1; P = .27). Treatment with TTP was associated with erythema 6 times less frequently than RA (11% vs 64%) (TTP - RA difference: -0.53; 95% CI, -0.88 to -0.17; P = .01). Target gene analysis showed significant CRABP2 messenger RNA (mRNA) induction (confirming retinoic acid receptor signaling) but no significant changes in procollagen I or MMP1/3/9 mRNA in TTP-treated samples. Instead, MMP2 mRNA, which encodes a type IV collagenase, was significantly reduced in TTP-treated samples (week 24 - baseline mRNA difference: -5; 96% CI, -33 to 1.6; P = .02), and changes in MMP2 were strongly correlated with changes in fine wrinkles (r = 0.54; 95% CI, 0.12 to 0.80; P = .01). Interestingly, patients with severe baseline wrinkles exhibited greater improvements (r = -0.74; 95% CI, -0.89 to -0.43; P < .001). This trend was mirrored in MMP2 mRNA, with initial expression strongly predicting subsequent changes (r = -0.78; 95% CI, -0.89 to -0.43; P < .001).
Conclusions and relevance: In this randomized clinical trial, there was no significant difference in efficacy between this particular formulation of TTP and tretinoin 0.02%. However, the results of these mechanistic studies highlight MMP2 as a possible mediator of retinoid efficacy in photoaging.
Trial registration: ClinicalTrials.gov Identifier: NCT01283464.