3D Microbiotic Skin Models and Metagenomics to Understand and Modulate Skin Colonization and Infection
Historically, keratinocytes cells in monolayer were used to study interaction between the skin and its microorganisms. These studies have provided answers about many aspects of bacterial attachment to cells and about the innate immune response activated by keratinocytes upon encountering bacteria or fungi. To know more about these interactions, we developed several incremental methods including a novel three-dimensional organotypichuman skin culture model. At first,we developed in-tuboco-cultures of up to 4 species from ATCC: S. aureus, S. epidermidis, S. hominis and P. acnes and we used Q-PCR for their identification and quantification. This method allowed us to evaluate the microorganisms’ relative growth and their interactions between each other. With these observations, we were able to select active ingredients favoring the growth of commensal bacteria (S.epidermidis and S. hominis) to the detriment of pathogenic bacteria (S. aureus and P.acnes). To study skin and microorganism interactions, we developed internally new microbiotic 2D and 3D skin models. Microbiotic 2D skin models were composed of differentiated keratinocytes, sebocytesor monocytes cultured with different microorganisms (Staphylococci, Propionibacterium,yeast). Microbiotic 3D skin models were composed of primary human fibroblasts and keratinocytes grown with S. aureus or P. acnes combined or not with S. epidermidis. The active ingredients were systemically or topically applied. In these models, parameters such as germ adhesion, growth, first step of biofilm formation and skin reactions were evaluated between 1 to 3 days.
Thanks to these 3D microbiotic models, we were able to identify active ingredients having different efficiency profiles. For example: decreasing the global microbial load, specifically inhibiting P. acnes, or decreasing P. acnes while increasing S. epidermidis, for a healthier balanced skin flora. Developing a dedicated microbiotic skin engineering platform enables us to illustrate how the bacteria could interact with each other within relevant interaction with skin cells. In order to get closer to physiological conditions these 3D models will
be improved using new ATCC species or some species involved in diverse skin dysbiosis and swabbed from panelists. Moreover, additional inflammatory stresses will be associated to mimic dysbiotic skin environment and select more potent ingredients.