Dermatological and cosmetics fields have recently started to focus on the human skin microbiome and microbiota, since the skin microbiota is involved in the health and dysbiosis of the skin ecosystem. Amongst the skin microorganisms, Staphylococcus epidermidis and Cutibacterium acnes, both commensal bacteria, appear as skin microbiota sentinels. These sentinels have a key role in the skin ecosystem since they protect and prevent microbiota disequilibrium by fighting pathogens and participate in skin homeostasis through the production of beneficial bacterial metabolites. These bacteria adapt to changing skin microenvironments and can shift to being opportunistic pathogens, forming biofilms, and thus are involved in common skin dysbiosis, such as acne or atopic dermatitis. The current evaluation methods for cosmetic active ingredient development are discussed targeting these two sentinels with their assets and limits. After identification of these objectives, research of the active cosmetic ingredients and products that maintain and promote these commensal metabolisms, or reduce their pathogenic forms, are now the new challenges of the skincare industry in correlation with the constant development of adapted evaluation methods.

Ulva sp. is known to be a source of bioactive compounds such as ulvans, but their biological activity on human dermal fibroblast extracellular matrix (ECM) is poorly reported. In this work, the regulation of ECM has been investigated for the first time at both proteomic and transcriptomic levels in normal human skin dermal fibroblasts, after 48 h of incubation with poly- and oligosaccharide fractions from Ulva sp. obtained after enzyme-assisted extraction and depolymerization. Cell proliferation enhancement (up to +68%) without exhibiting any cytotoxic effect on fibroblasts was demonstrated at 50 and 1000 µg/mL by both fractions. At the proteomic level, polysaccharide fractions at 1000 µg/mL enhanced the most the synthesis of glycosaminoglycans (GAGs, up to +57%), total collagen, especially types I (up to +217%) and III, as well as the synthesis and activity of MMP-1 (Matrix Metalloproteinase-1, up to +309%). In contrast, oligosaccharide fractions had no effect on GAGs synthesis but exhibited similarities for collagens and MMP-1 regulation. At the transcriptomic level, the decrease of COL1A1 and COL1A2 expression, and increase of COL3A1 and MMP-1 expression, confirmed the modulation of ECM metabolism by both fractions. Our research emphasizes that poly- and oligosaccharide Ulva sp. fractions exhibit interesting biological activities and supports their potential use in the area of skin renewal for anti-aging dermo-cosmetic applications.

Data on fractionation and depolymerization of the matrix ulvan polysaccharides, and studies on the biological activities on skin cells, are very scarce. In this work, crude ulvans were produced by using EAE (enzyme-assisted extraction) and compared to maceration (an established procedure). After different fractionation procedures—ethanolic precipitation, dialysis, or ammonium sulfate precipitation—the biochemical composition showed that EAE led to an increased content in ulvans. Coupling EAE to sulfate ammonium precipitation led to protein enrichment. Oligosaccharides were obtained by using radical depolymerization by H₂O₂ and ion-exchange resin depolymerization. Sulfate groups were partially cleaved during these chemical treatments. The potential bioactivity of the fractions was assessed using a lipoxygenase inhibition assay for anti-inflammatory activity and a WST-1 assay for human dermal fibroblast viability and proliferation. All ulvans extracts, poly- and oligosaccharidic fractions from EAE, expanded the fibroblast proliferation rate up to 62%. Our research emphasizes the potential use of poly- and oligosaccharidic fractions of Ulva sp. for further development in cosmetic applications.

Ulva sp. is known to be a source of bioactive compounds such as ulvans, but to date, their biological activity on skin commensal and/or opportunistic pathogen bacteria has not been reported. In this study, the effects of poly- and oligosaccharide fractions produced by enzyme-assisted extraction and depolymerization were investigated, for the first time in vitro, on cutaneous bacteria: Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes. At 1000 μg/mL, poly- and oligosaccharide fractions did not affect the growth of the bacteria regarding their generation time. Polysaccharide Ulva sp. fractions at 1000 μg/mL did not alter the bacterial biofilm formation, while oligosaccharide fractions modified S. epidermidis and C. acnes biofilm structures. None of the fractions at 1000 μg/mL significantly modified the cytotoxic potential of S. epidermidis and S. aureus towards keratinocytes. However, poly- and oligosaccharide fractions at 1000 μg/mL induced a decrease in the inflammatory potential of both acneic and non-acneic C. acnes strains on keratinocytes of up to 39.8%; the strongest and most significant effect occurred when the bacteria were grown in the presence of polysaccharide fractions. Our research shows that poly- and oligosaccharide Ulva sp. fractions present notable biological activities on cutaneous bacteria, especially towards C. acnes acneic and non-acneic strains, which supports their potential use for dermo-cosmetic applications.

Les ulvanes sont des polysaccharides matriciels sulfatés constitutifs de la paroi de l’algue verte Ulva sp.. Bien que proliférative et quantitativement disponible, Ulva sp. est peu valorisée avec des applications dans des domaines à faible valeur ajoutée. Ce projet de thèse a pour objectif la production de fractions enrichies en ulvanes et en oligo-ulvanes dans le but d’évaluer leurs propriétés biologiques sur le système cutané. Les fractions d’ulvanes ont été produites par macération et extraction assistée par enzyme suivie de différents procédés de purification : précipitation éthanolique et dialyse. Des dépolymérisations radicalaire et acide ont permis d’obtenir des fractions d’oligo-ulvanes. Ces fractions d’ulvanes et d’oligo-ulvanes stimulent la prolifération de fibroblastes dermiques humains. Une augmentation de la synthèse protéique de composants matriciels dont les collagènes de type I et III, et les glycosaminoglycanes a été mise en évidence. Les fractions stimulent également l’expression, la synthèse et l’activité enzymatique de MMP-1. Au niveau du microbiote cutané, ces fractions n’altèrent pas la croissance des bactéries commensales S. epidermidis, S. aureus et C. acnes, mais peuvent modifier la formation de biofilm. Les fractions d’ulvanes et d’oligo-ulvanes diminuent également le potentiel inflammatoire des kératinocytes HaCaT induit par C. acnes. Ainsi, les travaux ont démontré que les fractions d’ulvanes et d’oligo-ulvanes présentent des activités biologiques prometteuses pour des applications dermo-cosmétiques dans le cadre de stratégies de réparation tissulaire, anti-vieillissement, ou anti-inflammatoire, dans le respect du microbiote commensal cutané.