Marisa Meloni, has presented  the more recent experimental findings generated in the  Skin Microbiome Research Unit at VitroScreen  at the last IFSCC congress in Milan

The presentation titled “New insights on skin responses to UV: the contribution of skin associated microbiome” has given new insights on this almost unexplored topic.

Reconstructed Living Human Skin models colonized with bacteria mimic the real site where the interaction skin-microbiome occurs and allow to identify the mechanisms by which microbiome regulates skin response to the environment and, most importantly,   the defense and adaptive mechanisms. The microbiome role in sun protection is almost unknown, previously  not published data have shown that Epidermis model colonized with S.epidermidis and irradiated (2 MED)  compared to  uncolonized control has :

• inhibited NF?B translocation and the associated oxidative stress;
• induced a reduction of sunburn cells and melanosome maturation
• significantly modulated the  b-defensin 2 expression levels.

These results have inspired a new research study conducted on a pigmented epidermis model ( RHPE phototype IV)  colonized with the 3 different  bacteria: S.epidermidis ATCC 12228 a commensal strain, S.aureus ATCC 33591MRSA a pathogens,  and C.acnes ATCC 11828 -Type II mostly associated with health skin.

The experimental design was based on RHPE colonized and irradiated with 2 MED corresponding to a very weak UV stress for a phototype IV. The read out were performed 24h after irradiation. The bacterial load on the epidermal surface was unaffected by the UV radiation in the case of C.acnes and S.aureus  while the S.epidermidis viable count  was reduced. Skin and associated microbiome have a strong symbiotic relationship based on a continuous crosstalk between the 2 populations during our lives. The role of bacteria is unlimited and changes over time according to skin conditions and the environment: it is a complex community determining molecular, metabolic and immune-mediated responses.

Given the deep variability of the microbial population inhabiting the skin layers, the proposed in vitro approach on 3D human skin tissues colonized with a single strain seems to be relevant to identify  the role of any single actor. Globally, the results quantified in this research project have underlined a higher sensitivity (stronger inflammatory response, deeper pigmentation, oxidative stress, immunosuppression) to the UV in absence of associated microbiota, thus confirming a fundamental and almost unknown protective role in sun protection.

 

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