SUN CARE
Protecting keratinocytes stem cells from UVA harm
Laurie Canel - Gattefossé ABSTRACT
Eco-designed and sustainably sourced active ingredient, Solastemis™ acts at the heart of the epidermis mechanics by protecting the DNA of keratinocytes from lesions induced by UVA radiation and by boosting endogenous DNA repair capacity. Doing so, it preserves the stem cells of the epidermis, thus ensuring proper homeostasis for the skin’s first line of defence. Beyond epidermis, it also offers a shield for the extra-cellular matrix by protecting key proteins (collagen, elastin) from degradation induced by solar exposure. Photoageing-associated symptoms are visibly corrected versus placebo: wrinkles and skin microrelief are significantly improved. The skin complexion appears brighter, more even and healthier.
As humans are faced with more extreme conditions due to climate change, the need for skin protection has become predominant in the beauty sector. The status of the skin itself is changing: it is considered as an organ in interaction with its surroundings and ever more challenging environment. The role of skin as a barrier against external nasties is now clearly understood. This can be seen with the more preventative approach to beauty and skincare, such as everyday use of SPF, the rising interest in dermocosmetics and the growing preference for pharmacy brands. These are clear signs of a consumer shift from skin care to skin health care. Eco-designed and truly natural active
ingredient, Solastemis™ is part of this movement. It is designed with the objective to ensure the health and longevity of the skin by protecting its cellular integrity against UV-induced aggressions, especially those of UVA. This ingredient was awarded the bronze for Best Active Ingredient at in-cosmetics Global 2022 in Paris.
Comparing UVB and UVA impacts on skin A physical barrier between the inside and the outside, the skin is one of the most responsive organs to external aggressions, particularly to UV (Ultraviolet) radiation. Among all environmental factors responsible
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for extrinsic ageing, repeated sun exposure is the most significant and photoageing is the major consequence; 80% of extrinsic ageing is photoageing. Photoaged skins feature a set of typical
modifications: wrinkles and fine lines, altered microrelief and coarse skin, lack of luminosity and pigmentary disorders. Among the different types of UV, UVB
rays have long time been considered more genotoxic than UVA.1
They are known to
severely damage epidermis, causing local inflammation and sunburn, and to penetrate to the heart of cells - right down to the DNA. Their role in the generation of photoproducts and direct DNA lesions is clearly established. Due to its capacity to penetrate deeper
layers of the skin, the concern with UVA was mainly related to structural alterations of the dermis through the breakdown of collagen and elastin networks amongst others. Yet a multitude of scientific publications has shown evidence that UVA radiation is not as innocuous as previously thought. Indeed, its abundance at the Earth’s surface
is undeniable: UVA rays are more than 20 times abundant in sun radiation than UVB, making it an external aggressor not to be neglected.2 Furthermore, as it penetrates further into the skin, it passes the epidermis and reaches the dermis, with damage described on both layers.
stress level in the skin and generates oxidative DNA lesions.3
It also dramatically increases the oxidative Finally, endogenous DNA repair
systems are overwhelmed by overexposure to UVA.4 More precisely, research show that UVA
is very likely to induce DNA lesions in the epidermal basal layer, which hosts the keratinocytes stem cells.5 The epidermis is a living epithelium,
composed of 90% keratinocytes arranged in layers, renewing on average every three weeks. Yet only a specific population of keratinocytes can proliferate and initiate the cell renewal process, which are named keratinocyte stem cells and considered the ‘mother’ cells of the epidermis. The integrity of these epidermal stem cells
and their protection against environmental aggressors are key to ensure the long-term function and health of the epidermis.
Research on UVA impacts on epidermal stem cells In recent years, Gattefossé’s skin biology team has partnered with a research group specialised in the study of genotoxic stress to study the effects of UVA radiation on keratinocyte stem cells. It was discovered keratinocyte stem cells benefit from very efficient DNA protection and
October 2022 PERSONAL CARE
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