The vitamin A ester retinyl propionate has a unique metabolic profile and higher retinoid-related bioactivity over retinol and retinyl palmitate in human skin models.

Human skin is exposed daily to environmental stressors, which cause acute damage and inflammation. Over time, this leads to morphological and visual appearance changes associated with premature ageing. Topical vitamin A derivatives such as retinol (ROL), retinyl palmitate (RPalm) and retinyl propionate (RP) have been used to reverse these changes and improve the appearance of skin. This study investigated a stoichiometric comparison of these retinoids using in vitro and ex vivo skin models. Skin biopsies were treated topically to compare skin penetration and metabolism. Treated keratinocytes were evaluated for transcriptomics profiling and hyaluronic acid (HA) synthesis and treated 3D epidermal skin equivalents were stained for epidermal thickness, Ki67 and filaggrin. A retinoic acid receptor-alpha (RARα) reporter cell line was used to compare retinoid activation levels. Results from ex vivo skin found that RP and ROL have higher penetration levels compared with RPalm. RP is metabolized primarily into ROL in the viable epidermis and dermis whereas ROL is esterified into RPalm and metabolized into the inactive retinoid 14-hydroxy-4,14-retro-retinol (14-HRR). RP treatment yielded higher RARα activation and HA synthesis levels than ROL whereas RPalm had a null effect. In keratinocytes, RP and ROL stimulated similar gene expression patterns and pathway theme profiles. In conclusion, RP and ROL show a similar response directionality whereas RPalm response was inconsistent. Additionally, RP has a consistently higher magnitude of response compared with ROL or RPalm.

In Vitro Penetration of Petrolatum in Stratum Corneum from Bodywash Formulation.

Petrolatum is a mixture of hydrocarbons that is widely used as a moisturizer. It is incorporated in bodywash formulations to help hydrate and maintain healthy skin appearance. The aim of this study was to investigate skin deposition and penetration of petrolatum from an experimental bodywash system consisting of petrolatum in vitro. Experiments were performed using cadaver split-thickness skin and Franz diffusion cells. Radiolabeled 14C-dotriacontane (C32-alkane) was used as a model permeant for petrolatum. The bodywash was applied on the skin and subsequently rinsed. At predetermined time points, the skin was wiped to remove the residual material on the surface, and tape-stripping was performed. Petrolatum was observed to deposit from the bodywash when applied on split-thickness skin with simulated rinsing. Petrolatum then penetrated into the stratum corneum and was detected at the depth of 12 tape-stripping and in the epidermis. The bodywash formulation could provide significant deposition and penetration of petrolatum into the stratum corneum at 1-72 hours postapplication.