in responses to UV: a preliminary understanding of microbiome role by Vitroscreen

The skin and its microbiome have a strong symbiotic relationship in a continuous cross-talk, which influences both counterparts’ behavior. Within exogenous factor influencing skin conditions, UV light plays a major role interacting with the physical and functional skin barrier unit through effects on both host cells and the skin microbiota. UV rays can alter integrity, metabolic and immune-mediated responses of the skin causing important modifications on skin appearance (hyper-pigmentation and photo-ageing) but also on skin health as inflammatory and immunological status.

Today, in the microbiome “era”, it is recognized that biologically relevant UVA and UVB rays interact not only with skin’s cells but also with bacteria and yeasts that inhabit skin and its appendages: it seems important to have a different approach to UV-mediated responses taking into account the contribution of microbiota and its evolutionary modifications. Considering the complexity of the individual components of skin microbiota and the biological diversity, a pre-clinical approach on 3D human skin models appears relevant to gain basic and mechanistic knowledge on this triple and new biological interaction.

Within this framework, in our laboratory we are currently investigating the effects of UV light on viable and fully differentiated skin models colonized with S. aureus, S. epidermidis and C. Acnes (either virulent and commensal strain) as relevant components of the microbiota community and their effects on the host by a multiple endpoint approach after UV-light induced damages. We are using two different skin models (RHE-epidermis including Type III melanocytes and full thickness models).

As expected, colonized tissues respond differently to UV exposure compared to not colonized and irradiated models: a delayed NFkB nuclear translocation, reduced oxidative stress, reduction of sunburn cells and melanin production, modulation of b-defensin 2 expression levels have been reported in presence of S.epidermidis. These results underline a higher skin sensitivity (stronger inflammatory response, deeper pigmentation and oxidative stress) to the UV in absence of associated microbiota thus confirming a fundamental but almost unknow protective role of microbiome towards UV exposure. Furthermore, the results derived after the topical application of reference probiotic strains, such as L. rhamnosus, on colonized tissue models have contributed to understand which mechanisms of skin innate response are activated by this type of actives to protect the host by UV exposure, demonstrating the applicability of the colonized 3D models for basic research and efficacy studies.

So far we have been able:

To identify a role of bacteria representative of microbiota community (the most abundant and supported by clinical findings) against UV light induced damages.
To understand basic mechanisms by which they could play a protective, rebalancing, detrimental role on skin under UV.
To develop a simplified but biologically relevant pre-clinical model for photo-biology investigations for R&D.
To validate in Vitro biological responses by confirming available in Vivo literature data.

Read the complete article: FOCUS#2 Solar Testing – Skinobs