Wrinkles: what are the effects of retinol on skin aging?

Retinol belongs to the retinoid family, which are derivatives of vitamin A, such as retinoic acid and retinal. The retinol molecule was first isolated in 1931 by Swiss chemist Paul KARRER, from mackerel liver oil. The first study using tretinoin, the biologically activated form of retinoids, to treat acne was published in 1943. The effectiveness of this compound on signs of aging was demonstrated in the 1980s by American dermatologist Albert KLIGMAN. However, tretinoin is among the substances banned in cosmetic products according to European Regulation due to its potential irritant. This active ingredient is only available on prescription to treat severe to moderate acne. Retinol, which needs to be converted into retinoic acid in the skin to be active, is better tolerated. It is therefore authorized in cosmetics up to 0.3% in non-rinsed products.

The effectiveness of retinol and retinoids in general on skin aging has been demonstrated in numerous studies, both in vitro and in vivo. One notable study was conducted by KAWARA and his team in 2009 with 30 women averaging 50 years old. For eight weeks, these volunteers applied a cream based on retinol and collagen. A significant reduction in wrinkles was observed, particularly around the eye area, as shown in the photos below, while no side effects were reported. This is an opportunity to remind that retinol can be beneficial for the eye area, provided of course that a product suitable for this sensitive area is used.

This study is far from being an isolated case. Other research conducted by ERKIERT-POLGUJ and his team focused on formulations with 0.3% and 0.5% of retinol. For twelve weeks, 37 volunteers showing signs of photoaging applied one of the two treatments to each side of their face. Various skin parameters, such as wrinkle visibility and hyperpigmentation, were evaluated throughout the study. At the end of the twelve weeks, a significant improvement in these various parameters, not statistically different between the two retinol percentages, was observed. The results are presented in the following table. Photos of the participants were also taken before and after the study, visually demonstrating the improvement in skin quality.

One can cite the study conducted by MAJMUDAR and his team, which involved 41 women aged 35 to 55 years. These women applied a serum with 0.1% retinol every other day for two weeks, then daily for ten weeks. At the end of the twelve weeks, an average increase of 46.28% in the thickness of the epidermis was observed using confocal microscopy analysis. Furthermore, a wrinkle reduction was observed as early as four weeks, with a reduction of 58.68% in the cheeks and 27.93% around the eyes. After 12 weeks, the wrinkles on the cheeks had decreased by 63.74% and those around the eyes had decreased by 38.74%.

While the effectiveness of retinol on wrinkles and fine lines is widely acknowledged, it is crucial to exercise patience and wait several weeks to a few months before observing the initial results.

Once converted into retinoic acid, the retinol operates on multiple levels to prevent wrinkles and diminish those already present on the skin's surface. Many of its tissue effects are mediated by its interaction with cellular receptors, such as the cellular retinoic acid-binding proteins (CRABP) of types I and II. Retinoic acid also interacts with retinoic acid receptors (RAR) and retinoid X receptors (RXR). By activating these receptors, this molecule triggers a cascade of cellular signals that regulate the expression of various genes, some of which are involved in the differentiation of keratinocytes. In doing so, retinol induces several biological effects beneficial for combating skin aging.

• Retinol causes an increase in the thickness of the epidermis.

  As we age, the epidermis thins and both cellular renewal and keratinocyte proliferation slow down. This loss of skin tissue promotes the appearance of wrinkles on the skin's surface. By stimulating the proliferation and differentiation of keratinocytes, retinol limits epidermal atrophy, thus slowing the formation of wrinkles and fine lines.

• Retinol inhibits the breakdown of collagen and elastin.

  Collagen and elastin are two key proteins in the connective tissue that makes up the dermis. They are responsible for the flexibility, firmness, and elasticity of the skin. Unfortunately, over time, they are broken down by enzymes called matrix metalloproteinases (MMP), specifically by collagenase and elastase. When applied topically, retinol inhibits the activity of these enzymes, thus protecting the support fibers of the dermis. Additionally, it stimulates the synthesis of type 1 collagen in the dermis.

• Retinol counteracts the damage caused by free radicals.

  The free radicals are highly reactive unstable molecules that degrade the body's healthy cells and proteins, accelerating its aging process. They are generated by all sorts of factors, the most common being pollution, UV rays, and cigarette smoke. Thanks to the double bonds present in its chemical structure, retinol neutralizes free radicals and thus blocks their harmful effects on the skin.

• Retinol combats pigmentation spots.

  The emergence of brown spots is linked to skin aging and/or exposure to external aggressions, such as pollution and UV rays. As a reminder, hyperpigmentation is defined as a disruption in the pigmentation process : melanin, the pigment responsible for the natural coloration of the skin, is overproduced in certain areas, leading to the appearance of brown spots that disrupt the uniformity of the complexion. By accelerating cell renewal, retinoids, such as retinol, allow for the quicker removal of corneocytes overloaded with melanin. Another supposed mechanism of retinoids: they would inhibit the expression of tyrosinase, an enzyme essential for the conversion of tyrosine into melanin, and those of the TRP-1 and TRP-2 proteins, thus interrupting the production of melanin.

• KAFI & al. Improvement of naturally aged skin with vitamin a (retinol). Archives of Dermatology (2007).

• KAWARA S. & al. Evaluation of anti-wrinkle effects of a novel cosmetic containing retinol using the guideline of the Japan Cosmetic Industry Association. The Journal of Dermatology (2009).

• MAJMUDAR G. & al. A comparative study of the effects of retinol and retinoic acid on histological, molecular, and clinical properties of human skin. Journal of Cosmetic Dermatology (2015).

• GUAN T. & al. Molecular basis of retinol anti-aging properties in naturally aged human skin in vivo. International Journal of Cosmetic Science (2016).

• ERKIERT-POLGUJ A. & al. A Clinical Anti-Ageing Comparative Study of 0.3 and 0.5% Retinol Serums: A Clinically Controlled Trial. Skin Pharmacology and Physiology (2020).

• LANGTON A. & al. Retinoids in the treatment of photoageing: A histological study of topical retinoid efficacy in black skin. Journal of the European Academy of Dermatology and Venereology (2024).