Retinol and skin ageing.

This study is far from being an isolated case. Other research undertaken by ERKIERT-POLGUJ and his team have focused on formulations with 0.3% and 0.5% of retinol. Over 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 table below. 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 between 35 and 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 reduction in wrinkles 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 reduced by 38.74%.

While the efficacy 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 several 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 notably involved in the differentiation of keratinocytes. In doing so, retinol induces several biological effects beneficial for combating skin ageing.

• 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 restricts the breakdown of collagen and elastin.

  The collagen and elastin are two key proteins in the connective tissue that makes up the dermis. They are responsible for the suppleness, firmness, and elasticity of the skin. Unfortunately, over time, they are degraded 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 fibres of the dermis. Moreover, 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 ageing process. They are generated by all sorts of factors, the most common being pollution, UV rays, and smoking. Thanks to the double bonds present in its chemical structure, retinol neutralises free radicals and thus blocks their harmful effects on the skin.

• Retinol combats pigmentation spots.

  The emergence of brown spots is linked to skin ageing 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 colouration 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.