Skin Microbiome Modulation & Cosmetics

Beerse, Belgium, November 9, 2022:

The skin is the largest organ and the outermost interface between the body and its environment. It is a protective envelope, our first defense against extrinsic factors that can alter the body functions. It harbors an important microbial ecosystem, made of billions of resident commensal microorganisms. It is an ecological unit where human host and microbial cells interact, work together to perform key functions.

Note: skin microbiome definitions in the context of cosmetics can be found in our October 2022 review.

Human-Microbiome coevolution

Humans have coevolved with microbial communities over hundreds of thousands of years[i]. By coevolving with the host, these communities have shaped our phenotypes. Through the process of natural selection, mutations led to evolutionary adaptations to environmental conditions and increased fitness in these environments. This coevolution took place in all body niches, such as skin, oral, and vaginal mucosa, and gastrointestinal tract, with the key difference being in the set of the microbial communities involved in each one.

Skin microbiome and microbiota

The skin microbiome is a complex and dynamic ecosystem containing microbial communities, mostly composed of bacteria with fungi, viruses, and archaea at a lower rate. Microorganisms colonize the stratum corneum of the epidermis, skin appendages such as sweat, sebaceous glands and hair follicles (figure 1). The composition of the skin microbiota varies according to body sites that constitute diverse ecological niches: moist, dry, and sebaceous. Highly represented in the microbiota is Cutibacterium acnes, but especially in the sebum-rich sebaceous sites (face and forehead, scalp, back, chest) representing over 95% (up to 10 bacteria/cm2)[i],[ii]. Our microbial cohabitants are major participants in shaping and maintaining essential physiological processes. E.g. the skin microbiota is crucial to the skin barrier function, which provides protection against pathogens, tunes immune responses, and fortifies the epithelium[iii].

Skin microbiota and high strain diversity

The development of next generation sequencing technologies combined with steep decrease in price and time has allowed for the continuously growing number of studies of the microbial community with an unprecedented depth and resolution. It provided new insights into the skin microbiota composition and stressed the importance of strain level differences. Not all the strains are equal! The raised awareness of beneficial aspects of the commensal microbiota has led to a reevaluation of some of the bacterial members. E.g. paradigm shift on the view of Cutibacterium acnes that has changed dramatically. Advances in deep sequencing technologies have revealed the high strain diversity of C. acnes with three subspecies and six main phylotypes: subspecies acnes (comprising phylotypes IA1, IA2, IB, IC), subspecies defendes (phylotype II), and subspecies elongatum (phylotype III)[i]. To date, about 113 single locus sequence typing (SLST) types have been described. It permitted the identification of many C. acnes beneficial phylotype/strains that fulfills important roles as sentinel of the microbiome for skin homeostasis and health[ii].

Skin health and dysbiosis

The skin state results from intrinsic and extrinsic factors. It is the resulting outcome from the collective effect of the host (genetics, gender, age, lifestyle), the exposome (environmental exposures, e.g. UV radiation), and the skin microbiota (figure 2). Several lines of evidence suggest microbial diversity as key for skin health whereas skin conditions are associated with a decrease in diversity rather than a species proliferation. E.g. a decrease in the diversity between C. acnes six phylotypes, rather than its proliferation, has been associated with acne progression[i].

The natural balance of the skin microbiota can be altered by external factors, such as increasingly developing environmental stressors (e.g. pollution), exposition to UV radiation, or the repeated use of cosmetics with anti-microbial activity, that can result in a variety of skin conditions (figure 3).

Skin microbiome modulation

As we learn more about the skin microbiota composition, the high strain diversity, and their critical contributions to skin health, we are moving away from a simplistic view about “bad guys” species that we need to get rid of and going towards a more specific process with selected strains for a targeted modulation of the skin microbiome composition. It represents a powerful approach to address more effectively many skin concerns and dysbiotic conditions. Selecting the right strains of a particular species in a genetically diverse library and/or their derived-components is the smart strategy to obtaining a perfectly suited way for a given application and desired benefits. Skin microbiome modulators comprises three categories: probiotics, postbiotics, and prebiotics (figure 4). For optimal efficacy in the modulation of the skin microbiome, it is highly recommended to use one of the species naturally found on the skin. Topical application of cosmetics containing skin microbiome modulators is an innovative and effective approach to skin health.

About S-Biomedic

S-Biomedic is a life-science company at the forefront of skin-microbiome research and commercialization, harnessing the power of true skin microbiome commensals. Working with the skin as nature intended it!

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