Microbially competent 3D skin: a test system that reveals insight into host–microbe interactions and their potential toxicological impact

Abstract

The skin`s microbiome is predominantly commensalic, harbouring a metabolic potential far exceeding that of its host. While there is clear evidence that bacteria-dependent metabolism of pollutants modulates the toxicity for the host there is still a lack of models for investigating causality of microbiome-associated pathophysiology or toxicity. We now report on a biologically characterised microbial–skin tissue co-culture that allows studying microbe–host interactions for extended periods of time in situ. The system is based on a commercially available 3D skin model. In a proof-of-concept, this model was colonised with single and mixed cultures of two selected skin commensals. Two different methods were used to quantify the bacteria on the surface of the skin models. While Micrococcus luteus established a stable microbial–skin tissue co-culture, Pseudomonas oleovorans maintained slow continuous growth over the 8-day cultivation period. A detailed skin transcriptome analysis showed bacterial colonisation leading to up to 3318 significant changes. Additionally, FACS, ELISA and Western blot analyses were carried out to analyse secretion of cytokines and growth factors. Changes found in colonised skin varied depending on the bacterial species used and comprised immunomodulatory functions, such as secretion of IL-1α/β, Il-6, antimicrobial peptides and increased gene transcription of IL-10 and TLR2. The colonisation also influenced the secretion of growth factors such as VFGFA and FGF2. Notably, many of these changes have already previously been associated with the presence of skin commensals. Concomitantly, the model gained first insights on the microbiome’s influence on skin xenobiotic metabolism (i.e., CYP1A1, CYP1B1 and CYP2D6) and olfactory receptor expression. The system provides urgently needed experimental access for assessing the toxicological impact of microbiome-associated xenobiotic metabolism in situ.

A mixed community of skin microbiome representatives influences cutaneous processes more than individual members

“…To accomplish this, we use microbial isolates from healthy human skin and three-dimensional human skin equivalents. The human skin equivalents, like germ-free mouse models, allow for carefully controlled studies of skinmicroorganism interactions, [36] but they additionally support the study of human-specific tissues and microorganisms [37][38][39][40][41]. We studied microbiome representatives from species and genera that commonly reside in the aerobic environments of the skin surface-Staphylococcus epidermidis, Streptococcus luteciae, Bacillus sp., Roseomonas mucosa, Paenibacillus sp., Micrococcus luteus, Corynebacterium sp., and Acinetobacter lwoffi [5].…”

Commensal-Related Changes in the Epidermal Barrier Function Lead to Alterations in the Benzo[ a ]Pyrene Metabolite Profile and Its Distribution in 3D Skin

“…The aim of the study was to investigate the effects of commensal skin colonization on B[ a ]P-metabolism in situ using a microbially competent 3D skin model ( 31 ). The model was colonized with two previously isolated skin commensals, namely, Micrococcus luteus 1B and Pseudomonas oleovorans 1C ( 26 , 27 ).…”

“…At best, the microbiota is considered a systemic compartment when toxicity is tested in vivo . However, this does not consider the high species specificity of microbiota, nor does it acknowledge that even without this species specificity the microbiotas of laboratory animals are strongly impacted by the artificial environments the animals are housed in and thus are hardly representative ( 31 ). In the context of risk assessment of xenobiotic exposure, this not only is scientifically unsatisfying but also carries a true risk of missing relevant health effects.…”

“…The reason for this is commensal species specificity together with a lack of suitable model systems. We therefore recently reported the development of a new commensal 3D skin model ( 31 ). We have now applied this model to investigate commensal B[ a ]P-metabolism and its potential toxicologically relevant effects in situ .…”

Looking For Polycyclic Aromatic Hydrocarbon Metabolizing Microorganisms In The Oral Cavity of Smokers

“…Differences in the assay may contribute to the ndings as Sawada et al used Benzo[a]pyrene as the sole carbon source in the selection, while in this study a mixture of 5 PAHs was used. Nevertheless, it is apparent that PAH metabolizers are more ready isolatable from skin than the oral cavity, suggesting a low level of PAH metabolizing microbes in the oral environment 45 . One might speculate that oral niches for bacteria are less hospitable to PAH metabolizing microbes than those of the skin.…”