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The microbiome, as a community of microorganisms and their structural elements, genomes, metabolites/signal molecules, has been shown to play an important role in human health, with significant beneficial applications for gut health. Skin microbiome has emerged as a new field with high potential to develop disruptive solutions to manage skin health and disease. Despite an incomplete toolbox for skin microbiome analyses, much progress has been made towards functional dissection of microbiomes and host-microbiome interactions. A standardized and robust investigation of the skin microbiome is necessary to provide accurate microbial information and set the base for a successful translation of innovations in the dermo-cosmetic field. This review provides an overview of how the landscape of skin microbiome research has evolved from method development (multi-omics/data-based analytical approaches) to the discovery and development of novel microbiome-derived ingredients. Moreover, it provides a summary of the latest findings on interactions between the microbiomes (gut and skin) and skin health/disease. Solutions derived from these two paths are used to develop novel microbiome-based ingredients or solutions acting on skin homeostasis are proposed. The most promising skin and gut-derived microbiome interventional strategies are presented, along with regulatory, safety, industrial, and technical challenges related to a successful translation of these microbiome-based concepts/technologies in the dermo-cosmetic industry.

The movement of melanosomes, dense melanin-containing organelles, within human melanocytes is actin-dependent and mediated through the formation of a Rab27a-Slac2-a-myosin Va (MyoVa) protein complex. We previously showed that only the melanocyte-specific exon F isoforms of MyoVa are involved in melanosome transport to the dendrite extremities. Here, we investigate siRNA to downregulate the exon F-containing isoforms of MyoVa in primary human melanocytes. Efficient and specific knockdown of the MyoVa exon F isofoms were shown at both mRNA and protein levels. Further, a stable shRNA against the MyoVa exon F isoforms was prepared by using a lentiviral system to improve and confirm the silencing effect in hard-to-transfect melanocyte cells. Immunofluorescence microscopy shows that knockdown of the exon F isoforms results in blockade of intramelanocytic melanosome transport due to the inability to form the Rab27a-Slac2-a-MyoVa tripartite complex. Interestingly, the observed phenotypic effect (that is, perinuclear accumulation of melanosomes) is the same as that seen in melanocytes from patients with human Griscelli syndrome causing abnormal pigmentation. We conclude that our siRNA-based strategy provides a previously unreported tool to block the intracellular melanosome movement in primary human melanocytes and may become an innovative drug to treat hyperpigmentation.

Recent studies indicate that IL-1α functions intracellularly in pathways independent of its cell surface receptors by translocating to the nucleus and regulating transcription. Similarly, the chromatin-associated protein HMGB1 acts as both a nuclear factor and a secreted proinflammatory cytokine. Here, we show that IL-33, an IL-1-like cytokine that signals via the IL-1 receptor-related protein ST2 and induces T helper type 2-associated cytokines, is an endothelium-derived, chromatin-associated nuclear factor with transcriptional repressor properties. We found that IL-33 is identical to NF-HEV, a nuclear factor preferentially expressed in high endothelial venules (HEV), that we previously characterized. Accordingly, in situ hybridization demonstrated that endothelial cells constitute a major source of IL-33 mRNA in chronically inflamed tissues from patients with rheumatoid arthritis and Crohn's disease. Immunostaining with three distinct antisera, directed against the N-terminal part and IL-1-like C-terminal domain, revealed that IL-33 is a heterochromatin-associated nuclear factor in HEV endothelial cells in vivo . Association of IL-33 with heterochromatin was also observed in human and mouse cells under living conditions. In addition, colocalization of IL-33 with mitotic chromatin was noted. Nuclear localization, heterochromatin-association, and targeting to mitotic chromosomes were all found to be mediated by an evolutionarily conserved homeodomain-like helix–turn–helix motif within the IL-33 N-terminal part. Finally, IL-33 was found to possess transcriptional repressor properties, associated with the homeodomain-like helix–turn–helix motif. Together, these data suggest that, similarly to IL1α and HMGB1, IL-33 is a dual function protein that may function as both a proinflammatory cytokine and an intracellular nuclear factor with transcriptional regulatory properties.

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that results in areas of dry, itchy skin. Several cultivation-dependent and -independent studies have identified changes in the composition of microbial communities in these affected areas over time and when compared to healthy control individuals. However, how these communities vary on affected and unaffected skin of the same individual, and how these communities respond to emollient treatment, remains poorly understood. Here we characterized the microbial communities associated with affected and unaffected skin of 49 patients with AD before and after emollient treatment using high-throughput sequencing of the 16S rRNA gene. We found that microbial diversity and community composition was different between affected and unaffected skin of AD patients prior to treatment. Differences were driven primarily by the overabundance of Staphylococcus species on affected skin and a corresponding decrease in bacterial diversity. After 84-days of emollient treatment, the clinical symptoms of AD improved in 72% of the study population. Microbial communities associated with affected skin of these treatment responders more closely resembled unaffected skin after treatment as indicated by increased overall diversity and a decrease in the abundance of Staphylococcus species. Interestingly, Stenotrophomonas species were significantly more abundant in the communities of 'responders', suggesting a possible role in restoration of the skin microbiome in patients with AD. We demonstrated that the comparison of affected and unaffected skin from the same individual provides deeper insight into the bacterial communities involved in the skin dysbiosis associated with AD. These data support the importance of emollients in the management of AD although future studies should explore how emollients and other treatments help to restore skin dysbioses.

The cellular binding, uptake, and intracellular distribution of structured double-stranded phosphodiester oligonucleotides (decoys) have been examined in T lymphocytes using fluorescein-labeled molecules. Intracellular localization of hairpin and dumbbell decoys was similar to that of single-stranded oligonucleotides. At short incubation times, oligonucleotides were localized only in cytoplasmic vesicles, whereas at longer times, they were also found in the nucleus. Cellular uptake was dependent on temperature, time, and extracellular concentration. Oligonucleotide efflux was similar for all types of molecules and was very rapid (t1/2 = 10-15 minutes). These results imply that phosphodiester double-stranded oligonucleotides can enter cellular compartments of interest for their potential biologic function and, thus, provide a potential tool to control gene transcription.

We recently cloned a novel human nuclear factor (designated THAP1) from postcapillary venule endothelial cells (ECs) that contains a DNA-binding THAP domain, shared with zebrafish E2F6 and several Caenorhabditis elegans proteins interacting genetically with retinoblastoma gene product (pRB). Here, we show that THAP1 is a physiologic regulator of EC proliferation and cell-cycle progression, 2 essential processes for angiogenesis. Retroviral-mediated gene transfer of THAP1 into primary human ECs inhibited proliferation, and large-scale expression profiling with microarrays revealed that THAP1-mediated growth inhibition is due to coordinated repression of pRB/E2F cell-cycle target genes. Silencing of endogenous THAP1 through RNA interference similarly inhibited EC proliferation and G1/S cell-cycle progression, and resulted in down-regulation of several pRB/E2F cell-cycle target genes, including RRM1, a gene required for S-phase DNA synthesis. Chromatin immunoprecipitation assays in proliferating ECs showed that endogenous THAP1 associates in vivo with a consensus THAP1-binding site found in the RRM1 promoter, indicating that RRM1 is a direct transcriptional target of THAP1. The similar phenotypes observed after THAP1 overexpression and silencing suggest that an optimal range of THAP1 expression is essential for EC proliferation. Together, these data provide the first links in mammals among THAP proteins, cell proliferation, and pRB/E2F cell-cycle pathways.

Objective To identify and characterize which endothelial heparan sulfate proteoglycans (HSPGs) bind the chemokine CXCL8 (interleukin-8) in human rheumatoid arthritis (RA) and nonrheumatoid synovia. Method CXCL8 binding to endothelial HSPGs in RA and nonrheumatoid synovia was determined by heparinase treatment followed by an in situ binding assay and autoradiography. Endothelial HSPGs were characterized by immunohistochemical analysis and quantitative reverse transcriptase–polymerase chain reaction (RT-PCR). Phosphatidyinositol-specific phospholipase C (PI-PLC) and antibodies to HSPGs were used in in situ binding experiments to identify which HSPGs bound CXCL8. Results The expression of heparan sulfate on microvascular endothelial cells was demonstrated in RA and nonrheumatoid synovia. Using antibodies to syndecan-1–4 and glypican-1, -3, and -4, the selective expression of syndecan-3 by endothelial cells was detected in RA and nonrheumatoid synovia. In addition, RT-PCR showed the presence of syndecan-3 messenger RNA in endothelial cells extracted from RA and nonrheumatoid synovia. 125I-CXCL8 bound to venular endothelial cells; treatment with heparinases I and III significantly reduced this binding in RA but not nonrheumatoid synovia. 125I-CXCL8 binding was not reduced after treatment with PI-PLC, which cleaves glycosyl phosphatidylinositol linkages, suggesting that CXCL8 did not bind to glypicans. Treatment of synovia with a syndecan-3 antibody reduced CXCL8 binding to RA but not nonrheumatoid endothelial cells; however, no reduction in binding was observed with syndecan-2 or glypican-4 antibodies. Conclusion Our results show the selective induction of a CXCL8 binding site on endothelial syndecan-3 in RA synovium. This site may be involved in leukocyte trafficking into RA synovial tissue.

Endothelial cells play a central role in chronic inflammation: for example, they express adhesion molecules and present chemokines leading to enhanced leukocyte recruitment into tissues. Numerous markers of endothelial cells have been reported but there has been a lack of comparative data on their specificity. The present study compared the specificity of seven endothelial cell markers in the rheumatoid synovium and the colon of patients with Crohn's disease. These markers were: the sulphated epitope MECA-79, the Duffy antigen receptor for chemokines (DARC), von Willebrand factor, CD31 (PECAM-1), CD34, CD105 (endoglin) and CD146. MECA-79, DARC and von Willebrand factor showed a specific endothelial cell distribution. MECA-79, which recognizes sulphated ligands for leukocyte adhesion receptor L-selectin (CD62L), was selective for a subset of venules in highly inflamed tissue and was present in rheumatoid but not control osteoarthritic synovia. DARC was also specific for venules but had a more widespread distribution than MECA-79, and was present in rheumatoid and control synovia. The other markers all labelled endothelial cells in venules, arterioles and capillaries. However, they also localized to other cell types. For example, CD34 stained fibroblasts, CD146 was expressed by the pericytes and smooth muscle cells of vessel walls and CD31 and CD105 labelled a broad range of cell types.

Endothelial cells are active participants in chronic inflammatory diseases. These cells undergo phenotypic changes that can be characterised as activated, angiogenic, apoptotic and leaky. In the present review, these phenotypes are described in the context of human rheumatoid arthritis as the disease example. Endothelial cells become activated in rheumatoid arthritis pathophysiology, expressing adhesion molecules and presenting chemokines, leading to leukocyte migration from the blood into the tissue. Endothelial cell permeability increases, leading to oedema formation and swelling of the joints. These cells proliferate as part of the angiogenic response and there is also a net increase in the turnover of endothelial cells since the number of apoptotic endothelial cells increases. The endothelium expresses various cytokines, cytokine receptors and proteases that are involved in angiogenesis, proliferation and tissue degradation. Associated with these mechanisms is a change in the spectrum of genes expressed, some of which are relatively endothelial specific and others are widely expressed by other cells in the synovium. Better knowledge of molecular and functional changes occurring in endothelial cells during chronic inflammation may lead to the development of endothelium-targeted therapies for rheumatoid arthritis and other chronic inflammatory diseases.