Microbial symbiosis with the innate immune defense system of the skin

Exosomes and Exosome-Mimetics for Atopic Dermatitis Therapy

BACKGROUND

Exosomes and exosome mimetics are used as alternatives to cell therapy. They have shown potential in treating skin disorders by fortifying the skin barrier, mediating angiogenesis, and regulating the immune response while minimizing side effects. Currently, numerous studies have applied exosome therapy to treat atopic dermatitis (AD) caused by a weakened skin barrier and chronic inflammation. Research on exosomes and exosome mimetics represents a promising avenue for tissue regeneration, potentially paving the way for new therapeutic options. However, the efficacy of the therapy remains poorly understood. Also, the potential of exosome mimetics as alternatives to exosomes in skin therapy remains underexplored.

METHODS

Here, we reviewed the pathological features and current therapies of AD. Next, we reviewed the application of exosomes and exosome mimetics in regenerative medicine. Finally, we highlighted the therapeutic effects of exosomes based on their cell source and assessed whether exosome mimetics are viable alternatives.

RESULTS AND CONCLUSION

Exosome therapy may treat AD due to its skin regenerative properties, and exosome mimetics may offer an equally effective yet more efficient alternative. Research on exosomes and exosome mimetics represents a promising avenue for tissue regeneration, potentially paving the way for new therapeutic options.

Cutaneous T cell immunity

The skin is the primary barrier against environmental insults, safeguarding the body from mechanical, chemical and pathogenic threats. The frequent exposure of the skin to environmental challenges requires an immune response that incorporates a sophisticated combination of defenses. Tissue-resident lymphocytes are pivotal for skin immunity, working in tandem with commensal bacteria to maintain immune surveillance and homeostasis, as well as participating in the pathogenesis of several skin diseases. Indeed, it has been estimated that the human skin harbors nearly twice as many T cells as found in the circulation. Effective treatment of skin diseases and new therapy development require a thorough understanding of the complex interactions among skin tissue, immune cells and the microbiota, which together regulate the skin's immune balance. This Review explores the latest developments and understanding of this critical barrier organ, with a specific focus on the role of skin-resident T cells.

Streptococcus mutans-derived extracellular vesicles promote skin wound healing via tRNA cargo

BACKGROUND

The human oral cavity harbors a diverse microbiota, including Streptococcus species. Oral mucosal wounds heal rapidly, although the exact cause remains unclear. This study investigates the impact of Streptococcus mutans-derived extracellular vesicles (Sm EVs) on wound healing in both oral mucosal organoids and mouse skin. To explore whether microbial EV RNA cargo influences wound healing, RNA sequences from Sm EVs were identified, and the most abundant sequences were synthesized into oligomers and encapsulated in E. coli EVs (Ec EVs) for further in vivo testing. We assessed the role of Toll-like receptor 3 (TLR3) in the wound healing mechanism in TLR3 knockout (KO) mice.

RESULTS

Sm EVs significantly enhanced cell proliferation and migration in oral mucosa, with enhanced focal adhesion complex formation. Sm EVs improved wound healing in mouse dorsal skin compared to PBS controls. RNA sequencing revealed that bacterial tRNAs, particularly the tRNA-Met variant (Oligo 1), were the most abundant RNAs in Sm EVs. Ec EVs carrying Oligo 1 produced similar wound healing effects to Sm EVs in mucosal organoids and mouse dorsal skin. However, in TLR3 knockout mice, Oligo 1 did not improve wound healing.

CONCLUSIONS

This study highlights the role of Sm EVs, particularly their tRNA variants, in promoting skin wound healing through a TLR3-dependent mechanism. These findings suggest that EVs from oral commensal bacteria may offer therapeutic potential for chronic, non-healing skin wounds.

Unveiling the interplay among skin microbiota, cytokines, and T2DM: an insightful Mendelian randomization study

BACKGROUND

Previous observational studies have indicated a correlation between the skin microbiome and Type 2 diabetes (T2DM). It is hypothesized that this causal relationship may be influenced by inflammatory responses. However, these factors as determinants of T2DM remain largely unexplored.

METHOD

This study incorporated data from the GWAS database on the skin microbiome, 91 types of inflammatory cytokines, and T2DM. We employed two-sample MR and multivariable MR methods to assess the correlation between the skin microbiome and T2DM, and to investigate whether this correlation is affected by inflammatory cytokines.

RESULTS

The results of the two-sample MR analysis indicate that within the skin microbiome, genetically predicted genus: Acinetobacter, class: Alphaproteobacteria, genus: Bacteroides, ASV005[Propionibacterium granulosum], and ASV072[Rothia mucilaginosa] are associated with an increased risk of T2DM, while phylum: Proteobacteria, genus: Enhydrobacter, family: Clostridiales, ASV006[Staphylococcus hominis] serve as protective factors against T2DM. Among the inflammatory cytokines, levels of Macrophage colony-stimulating factor 1, Tumor necrosis factor receptor superfamily member 9, Urokinase-type plasminogen activator, and C-C motif chemokine 28 are associated with an increased risk of T2DM. Multivariable MR analysis further revealed that Macrophage colony-stimulating factor 1 levels act as a mediating factor between ASV072[Rothia mucilaginosa] and T2DM.

CONCLUSION

In this study, we found a connection between the skin microbiome and T2DM, with inflammatory cytokines playing a key role in this relationship. This research helps us better understand this complex link and shows that addressing inflammation is important for preventing and treating diabetes. This could greatly benefit public health by reducing the impact of diabetes and its complications. Our results suggest that future studies should explore the specific biological interactions between the skin microbiome and diabetes to develop more effective risk management and treatment strategies from a microbial perspective.

Efficacy and Safety of Topical Compound Heparin Sodium Allantoin Gel (Main Components: Onion Extract Quercetin) for the Treatment of Rosacea

BACKGROUND

The management of papulopustular rosacea presents a significant clinical challenge. Anti-inflammatory and vasoconstrictive treatments are ineffective in the rapid amelioration of the dryness, burning, and itching caused by skin barrier damage in patients with papulopustular rosacea.

AIMS

To assess the efficacy and safety of the topical application of compound heparin sodium allantoin gel to treat rosacea.

METHODS

Eighty-two patients participated in this randomized, prospective, single-center, and controlled trial. The Clinician Erythema Assessment score, Investigator Global Assessment score, transepidermal water loss, and skin hydration were evaluated at 0, 2, 4, 8, and 12 weeks. Rosacea-specific quality of life score, itching, dryness, burning, Global Aesthetic Improvement Scale, and Patient Self-Assessment grades were also assessed.

RESULTS

Compared with the traditional therapy group, the 8-week and 12-week topical application of compound heparin sodium allantoin gel to treat rosacea significantly decreased Clinician Erythema Assessment/Investigator Global Assessment grades, burning and itching grades, and rosacea-specific quality of life scores. Compound heparin sodium allantoin gel significantly improved the skin barrier with hydration and significantly decreased trans-epidermal water loss. For patients with Demodex infestation, externally applied compound heparin sodium allantoin gel was associated with better rosacea treatment outcomes and improved skin barrier function than externally applied hyaluronic acid. This may be attributable to the inhibition of abnormal demodex, improved skin barrier, and repair of minor skin wounds.

CONCLUSIONS

Compound heparin sodium allantoin gel effectively improved facial erythema, alleviated ithching and burning sensations, and improved patients' quality of life.

TRAIL REGISTRATION

ClinicalTrials.gov identifier: ChiCTR2400087948.

Association of the skin microbiome with the biomechanical scar properties in patients with burns

BACKGROUND AND OBJECTIVES

Skin microbiome dysbiosis can cause skin barrier dysfunction and stimulate scar property change. Skin barrier disruption post-burn injury leads to an imbalance in skin microbe diversity and distribution. We aimed to examine the changes in the skin microbiome of re-epithelialized burn scars.

MATERIAL AND METHODS

Twenty three patients were enrolled between January 2020 and July 2022. Twenty-six (13 Scar 1, immediately after complete wound healing; and 13 Scar 2, 3 months after complete wound healing) of seventy-eight scar skin samples (39 Scar 1 and 39 scar 2) qualified for analysis. Microbial community analysis was performed. Biomechanical scar properties of each patient and their correlation with skin microbiome were investigated.

RESULTS

The α-diversity of the scarred skin microbiome increased with time (Shannon's index, p = 0.029; Simpson's index, p = 0.009). The linear discriminant analysis effect size results showed that Bacteroides abundance decreased in scars after 3 months, whereas Campylobacter and Cutibacterium abundance increased. Campylobacter and Cutibacterium negatively and positively correlated with the final distensibility gross and biological elasticity, respectively. These results were consistent with the changes in the biomechanical properties of scars.

CONCLUSION

The scar skin microbial communities in patients with burns changed with biomechanical scar properties over time, and specific skin microorganisms correlated with biomechanical scar dynamics at the genus level.

Skin microbiome and dermatologic disorders

Human skin acts as a physical barrier to prevent the entry of pathogenic microbes while simultaneously providing a home for commensal bacteria and fungi. Microbiome sequencing studies have demonstrated the unappreciated diversity and selectivity of these microbes. Functional studies have demonstrated the impact of specific strains to tune the immune system, sculpt the microbial community, provide colonization resistance, and promote epidermal barrier integrity. Recent studies have integrated the microbiome, immunity, and tissue integrity to understand their interplay in common disorders such as atopic dermatitis. In this Review, we explore microbiome shifts associated with cutaneous disorders with an eye toward how the microbiome can be mined to identify new therapeutic opportunities.

Antimicrobial Peptides Against Arboviruses: Mechanisms, Challenges, and Future Directions

This review delves into the potential of antimicrobial peptides (AMPs) as promising candidates for combating arboviruses, focusing on their mechanisms of antiviral activity, challenges, and future directions. AMPs have shown promise in preventing arbovirus attachment to host cells, inducing interferon production, and targeting multiple viral stages, illustrating their multifaceted impact on arbovirus infections. Structural elucidation of AMP-viral complexes is explored to deepen the understanding of molecular determinants governing viral neutralization, paving the way for structure-guided design. Furthermore, this review highlights the potential of AMP-based combination therapies to create synergistic effects that enhance overall treatment outcomes while minimizing the likelihood of resistance development. Challenges such as susceptibility to proteases, toxicity, and scalable production are discussed alongside strategies to address these limitations. Additionally, the expanding applications of AMPs as vaccine adjuvants and antiviral delivery systems are emphasized, underscoring their versatility beyond direct antiviral functions.

Exploring shared mechanisms between ulcerative colitis and psoriasis and predicting therapeutic natural compounds through bioinformatics and molecular docking

Introduction

Previous studies have suggested a potential correlation between psoriasis (PS) and ulcerative colitis (UC). However, studies exploring the shared mechanisms of both diseases remain limited. Current treatments primarily involve using immunosuppressive drugs, which can lead to potential side effects and drug resistance. Traditional Chinese medicine has demonstrated favorable efficacy in treating UC and PS with fewer side effects. This study aims to elucidate the shared biological mechanisms underlying UC and PS and to predict natural compounds effective for treating both disorders.

Method

We collected and validated differentially expressed genes associated with UC and PS from the Gene Expression Omnibus database. A protein-protein interaction network was constructed using the STRING database, aiding in identifying core targets. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases were utilized to analyze the functions and genomic enrichment of the identified core targets. The CIBERSORT method was employed to assess the correlation of core targets with immune cells. Compounds with potential therapeutic values were selected from the Coremine and TCMSP databases, and their therapeutic efficacy was predicted via molecular docking.

Results

In UC and PS, 20 common core targets were identified, with matrix metalloproteinase 9 (MMP9), matrix metalloproteinase 1 (MMP1), cluster of differentiation 274 (CD274), C-X-C motif chemokine ligand 10 (CXCL10), and topoisomerase II alpha (TOP2A) emerging as the most relevant targets shared between both conditions. Elevated levels of macrophages and dendritic cells were observed in UC and PS, with CXCL10 exhibiting the closest association with macrophages. UC and PS shared common signaling pathways, including IL-17, TNF, and chemokine signaling pathways, among others. Molecular docking revealed that quercetin, baicalen, irisolidone, rutaecarpine, epigallocatechin-3-gallate, and others held potential as natural compounds for treating both disorders.

Conclusion

MMP9, MMP1, and CXCL10, central mediators in the inflammatory pathways of UC and PS, establish a shared mechanism by triggering cytokine and chemokine activation, leading to tissue damage and positioning them as promising therapeutic targets for both conditions. Compounds such as quercetin, luteolin, irisolidone, rutaecarpine, and so on may be key drugs for treating both conditions. These findings suggest the potential advancement of therapeutic strategies and the enhancement of patient care by exploring shared mechanisms and predicting promising natural compounds for treating UC and PS.

Oral tranexamic acid treats papulopustular rosacea by improving the skin barrier

BACKGROUND

Papulopustular rosacea (PPR) is a chronic inflammatory disease with a significant impact on facial aesthetics. An impaired skin barrier is an important factor in the development and exacerbation of PPR. Tranexamic acid (TXA) has immune regulatory and anti-inflammatory effects, inhibits angiogenesis and endothelial hyperplasia, and promotes skin barrier repair.

AIMS

We investigated the efficacy and safety of oral TXA for PPR treatment.

PATIENTS/METHODS

In total, 70 patients were randomly assigned to receive traditional therapy plus oral TXA or traditional therapy alone for 8 weeks, with a 4-week follow-up period. The subjective improvement in rosacea was assessed using the clinical erythema assessment (CEA), investigator's global assessment (IGA), patient self-assessment (PSA) score, rosacea-specific quality of life (RQoL) score, and global aesthetic improvement score (GAIS). An objective improvement in rosacea was assessed using skin hydration, trans-epidermal water loss (TEWL), clinical photography, and an eight spectrum facial imager.

RESULTS

CEA/IGA/PSA, dryness, and RQoL scores were significantly lower and GAIS was higher in the TXA group than in the traditional therapy group. Furthermore, oral TXA significantly improved skin barrier function, increased skin hydration, and decreased TEWL, with no significant side effects. Notably, we observed better outcomes and a greater improvement in skin barrier function with TXA treatment in patients with dry-type rosacea than in patients with oily skin.

CONCLUSIONS

The addition of oral TXA to traditional therapy can lead to rapid and effective improvements in PPR, which may be attributed to improvements in skin barrier function.

The Human Skin Microbiome in Health: CME Part 1

Human skin is home to a myriad of microorganisms, including bacteria, viruses, fungi, and mites, many of which are considered commensal microbes that aid in maintaining the overall homeostasis or steady-state condition of the skin and contribute to skin health. Our understanding of the complexities of the skin's interaction with its microorganisms is evolving. This knowledge is based primarily on in vitro and animal studies, and more work is needed to understand how this knowledge relates to humans. Here, we introduce the concept of the skin microbiome and discuss skin microbial ecology, some intrinsic factors with potential influence on the human skin microbiome, and possible microbiome-host interactions. The second article of this two-part CME series describes how microbiome alterations may be associated with skin disease, how medications can affect the microbiome, and what microbiome-based therapies are under investigation.

Composition and diversity of 16S rRNA based skin bacterial microbiome in healthy horses

Characterization of microbiota structure on the skin of healthy horses is important for further development of modulation strategies to ensure optimal bacterial composition for physiological processes. This requirement is also supported by the relatively high incidence of dermatological diseases in horses and thus the need to manage them therapeutically. The taxonomic analysis of skin samples (n = 30) from five different body parts of clinically healthy Shetlands ponies females (neck, back, abdomen, pastern, muzzle) kept under homogeneous conditions (in open stalls with paddock, feed with dry hay, green grass ad libitum and granulated feed) was performed using amplification of V3-V4 region of the 16S rRNA gene. Results indicate that bacteria associated with healthy equine skin represent 18 phyla, 29 classes and 119 families. The most abundant phyla were Proteobacteria (30.8 ± 9.1%) followed by Actinobacteriota (20.4 ± 7.6%), Firmicutes (19.5 ± 10.1%), Bacteroidota (8.5 ± 5.0%) and Deinococcota (7.2 ± 14.8%). Among 229 genera identified, Corynebacterium (7.4 ± 6.5%) was the most abundant genus in skin sites of horses, followed by Deinococcus (7.1 ± 14.9%) and Macrococcus (5.0 ± 8.2%). Indices for the richness and diversity of species within bacterial populations for five regions of horses skin revealed no significant variations observed for species richness (Chao1, p-value 0.2001) but significant result for species evenness (Shannon, p-value 0.0049) with maximum on the neck and minimum on the back skin site. The clustering was seen across samples from different skin sites but also across samples collected from individual horses.

Mesenchymal stem cell therapy using Pal-KTTKS-enriched carboxylated cellulose improves burn wound in rat model

Despite the great progress in developing wound dressings, delayed wound closure still remains a global challenge. Thus, developing novel wound dressings and employing advanced strategies, including tissue engineering, are urgently desired. The carboxylated cellulose was developed through the in situ synthesis method and further reinforced by incorporating pal-KTTKS to stimulate collagen synthesis and improve wound healing. The developed composites supported cell adhesion and proliferation and showed good biocompatibility. To boost wound-healing performance, adipose-derived mesenchymal stem cells (MSC) were seeded on the pal-KTTKS-enriched composites to be implanted in a rat model of burn wound healing. Healthy male rats were randomly divided into four groups and wound-healing performance of Vaseline gauze (control), carboxylated cellulose (CBC), pal-KTTKS-enriched CBC (KTTKS-CBC), and MSCs seeded on the KTTKS-CBC composites (MSC-KTTKS-CBC) were evaluated on days 3, 7, and 14 post-implantation. In each group, the designed therapeutic dressings were renewed every 5 days to increase wound-healing performance. We found that KTTKS-CBC and MSC-KTTKS-CBC composites exhibited significantly better wound healing capability, as evidenced by significantly alleviated inflammation, increased collagen deposition, improved angiogenesis, and considerably accelerated wound closure. Nevertheless, the best wound-healing performance was observed in the MSC-KTTKS-CBC groups among all four groups. This research suggests that the MSC-KTTKS-CBC composite offers a great deal of promise as a wound dressing to enhance wound regeneration and expedite wound closure in the clinic.

Facial Skin Microbiome Composition and Functional Shift with Aging

The change in the skin microbiome as individuals age is only partially known. To provide a better understanding of the impact of aging, whole-genome sequencing analysis was performed on facial skin swabs of 100 healthy female Caucasian volunteers grouped by age and wrinkle grade. Volunteers' metadata were collected through questionnaires and non-invasive biophysical measurements. A simple model and a biological statistical model were used to show the difference in skin microbiota composition between the two age groups. Taxonomic and non-metric multidimensional scaling analysis showed that the skin microbiome was more diverse in the older group (≥55 yo). There was also a significant decrease in Actinobacteria, namely in Cutibacterium acnes, and an increase in Corynebacterium kroppenstedtii. Some Streptococcus and Staphylococcus species belonging to the Firmicutes phylum and species belonging to the Proteobacteria phylum increased. In the 18-35 yo younger group, the microbiome was characterized by a significantly higher proportion of Cutibacterium acnes and Lactobacillus, most strikingly, Lactobacillus crispatus. The functional analysis using GO terms revealed that the young group has a higher significant expression of genes involved in biological and metabolic processes and in innate skin microbiome protection. The better comprehension of age-related impacts observed will later support the investigation of skin microbiome implications in antiaging protection.

Interleukin-1 family cytokines at the crossroads of microbiome regulation in barrier health and disease

Recent advances in understanding how the microbiome can influence both the physiology and the pathogenesis of disease in humans have highlighted the importance of gaining a deeper insight into the complexities of the host-microbial dialogue. In tandem with this progress, has been a greater understanding of the biological pathways which regulate both homeostasis and inflammation at barrier tissue sites, such as the skin and the gut. In this regard, the Interleukin-1 family of cytokines, which can be segregated into IL-1, IL-18 and IL-36 subfamilies, have emerged as important custodians of barrier health and immunity. With established roles as orchestrators of various inflammatory diseases in both the skin and intestine, it is now becoming clear that IL-1 family cytokine activity is not only directly influenced by external microbes, but can also play important roles in shaping the composition of the microbiome at barrier sites. This review explores the current knowledge surrounding the evidence that places these cytokines as key mediators at the interface between the microbiome and human health and disease at the skin and intestinal barrier tissues.

Acne microbiome: From phyla to phylotypes

Acne vulgaris is a chronic inflammatory skin disease with a complex pathogenesis. Traditionally, the primary pathophysiologic factors in acne have been thought to be: (1) altered sebum production, (2) inflammation, (3) excess keratinization and (4) colonization with the commensal Cutibacterium acnes. However, the role of C. acnes has been unclear, since virtually all adults have C. acnes on their skin yet not all develop acne. In recent years, understanding of the role of C. acnes has expanded. It is still acknowledged to have an important place in acne pathogenesis, but evidence suggests that an imbalance of individual C. acnes phylotypes and an alteration of the skin microbiome trigger acne. In addition, it is now believed that Staphylococcus epidermidis is also an actor in acne development. Together, C. acnes and S. epidermidis maintain and regulate homeostasis of the skin microbiota. Antibiotics, which have long been a staple of acne therapy, induce cutaneous dysbiosis. This finding, together with the long-standing public health edict to spare antibiotic use when possible, highlights the need for a change in acne management strategies. One fertile direction of study for new approaches involves dermocosmetic products that can support epidermal barrier function and have a positive effect on the skin microbiome.

Human interleukin-36γ plays a crucial role in cytokine induction during Sporothrix brasiliensis and S. schenckii infection in keratinocytes and PBMCs

Cytokines of the interleukin (IL)-1 superfamily including the different IL-36 isoforms, have been reported as mediators of acute and chronic inflammation in human skin diseases, such as psoriasis. Here, we demonstrated for the first time that Sporothrix schenckii and S. brasiliensis, the fungi that cause subcutaneous infection sporotrichosis, can induce the expression of IL-36α, IL-36γ and IL-36Ra in human keratinocytes and primary peripheral blood mononuclear cells (PBMCs). Specifically, IL-36γ was differentially expressed by keratinocytes stimulated with Sporothrix yeasts when compared to the commensal microorganism Staphylococcus epidermidis. The exposure of keratinocytes to 24 h or 7-days culture supernatant of PBMCs stimulated with Sporothrix induced higher IL-36γ production compared to direct stimulation of keratinocytes with the live fungus. We identified that IL-36γ mRNA expression in keratinocytes is increased in the presence of IL-17, TNF, IL-1β and IL-1α and these cytokines may act synergistically to maintain IL-36γ production. Lastly, using a cohort of 164 healthy individuals, we showed that individuals carrying variants of the IL36G gene (rs11690399 and rs11683399) exhibit increased IL-36γ production as well as increased innate cytokine production after Sporothrix exposure. Importantly, stimulation of PBMCs with recombinant IL-36γ increased the production of IL-1β and IL-6, while IL-36Ra were able to decrease the concentration of these cytokines. Our findings contribute to the understanding of the pathogenesis of sporotrichosis and suggest that IL-36γ may be involved in maintaining the cytokine loop that leads to tissue destruction by exacerbating the immune response in sporotrichosis. Of high interest, we present the IL-36 signalling pathway as a potential new therapeutic target.

Understanding Type 3 Innate Lymphoid Cells and Crosstalk with the Microbiota: A Skin Connection

Innate lymphoid cells (ILCs) are a diverse population of lymphocytes classified into natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and ILCregs, broadly following the cytokine secretion and transcription factor profiles of classical T cell subsets. Nonetheless, the ILC lineage does not have rearranged antigen-specific receptors and possesses distinct characteristics. ILCs are found in barrier tissues such as the skin, lungs, and intestines, where they play a role between acquired immune cells and myeloid cells. Within the skin, ILCs are activated by the microbiota and, in turn, may influence the microbiome composition and modulate immune function through cytokine secretion or direct cellular interactions. In particular, ILC3s provide epithelial protection against extracellular bacteria. However, the mechanism by which these cells modulate skin health and homeostasis in response to microbiome changes is unclear. To better understand how ILC3s function against microbiota perturbations in the skin, we propose a role for these cells in response to Cutibacterium acnes, a predominant commensal bacterium linked to the inflammatory skin condition, acne vulgaris. In this article, we review current evidence describing the role of ILC3s in the skin and suggest functional roles by drawing parallels with ILC3s from other organs. We emphasize the limited understanding and knowledge gaps of ILC3s in the skin and discuss the potential impact of ILC3-microbiota crosstalk in select skin diseases. Exploring the dialogue between the microbiota and ILC3s may lead to novel strategies to ameliorate skin immunity.

Proteins extracted from pearl oyster (Pinctada martensii) with efficient accelerated wound healing in vitro through promoting cell proliferation, migration, and collagen formation

Ethnopharmacological relevance

Pearl oyster (Pinctada martensii) is used in Chinese traditional medicine use in photoprotective, anti-inflammatory, and wound treatment.Aim of the study: This study explored whether the mucus protein of Pearl oyster (protein of Pinctada martensii, PMP) affects human skin fibroblast (HSF) proliferation, migration, collagen-related gene expression related to collagen formation, and in vivo healing effects.

Materials and methods

The PMP component was analyzed by LC-MS/MS. The cell viability was evaluated using a CCK-8 kit. The expression genes were measured by reverse transcription polymerase chain reaction. A full-thickness excisional wounding model in Sprague-Dawley (SD) rats was used to test the repairing effect of PMP in vivo, and Hematoxylin-Eosin (H&E) and Masson's Trichrome staining were applied to evaluate skin structure.

Results

The components of PMP were identified using LC-MS/MS proteomics, and a total of 3023 proteins were detected. The results of PMP-treated HSF showed that PMP effectively promoted cell proliferation by 1.6-fold and cell migration by 1.5-fold at a concentration of 1 mg/mL. Additionally, PMP treatment up-regulated the expression levels of collagen-related genes COL1A1, COL3A1, and MMP-1 in fibroblasts. Furthermore, PMP was applied in the therapy of full-thickness excisional wounds in rats. The results demonstrated that PMP significantly accelerated wound healing time, resulted in the recovery of dermal and epithelial thickness, and stimulated collagen regeneration. The regenerated skin closely resembled the structure of normal skin.

Conclusions

These findings provide solid evidence supporting the potential of PMP as a promising candidate for the treatment of skin wounds.

Innovative Approaches for Maintaining and Enhancing Skin Health and Managing Skin Diseases through Microbiome-Targeted Strategies

The skin microbiome is crucial in maintaining skin health, and its disruption is associated with various skin diseases. Prebiotics are non-digestible fibers and compounds found in certain foods that promote the activity and growth of beneficial bacteria in the gut or skin. On the other hand, live microorganisms, known as probiotics, benefit in sustaining healthy conditions when consumed in reasonable quantities. They differ from postbiotics, which are by-product compounds from bacteria that release the same effects as their parent bacteria. The human skin microbiome is vital when it comes to maintaining skin health and preventing a variety of dermatological conditions. This review explores novel strategies that use microbiome-targeted treatments to maintain and enhance overall skin health while managing various skin disorders. It is important to understand the dynamic relationship between these beneficial microorganisms and the diverse microbial communities present on the skin to create effective strategies for using probiotics on the skin. This understanding can help optimize formulations and treatment regimens for improved outcomes in skincare, particularly in developing solutions for various skin problems.

Longitudinal study of the interplay between the skin barrier and facial microbiome over 1 year

Skin is a diverse ecosystem that provides a habitat for microorganisms. The skin condition and the skin microbiome interact each other under diverse environmental conditions. This study was conducted on 10 study participants for a one-year, from September 2020 to August 2021, to investigate the variability of skin microbiome and skin biophysical parameters [TEWL, hydration, and elasticity (R5)] according to season, and to understand the interplay between skin microbiome and skin characteristics. We identified that Cutibacterium, Corynebacterium, Staphyloccocus, unclassified genus within Neisseriaceae, and Streptococcus were major skin microbial taxa at the genus level, and fluctuated with the seasons. Cutibacterium was more abundant in winter, while Corynebacterium, Staphylococcus, and Streptococcus were more abundant in summer. Notably, Cutibacterium and skin barrier parameter, TEWL, exhibited a co-decreasing pattern from winter to summer and showed a significant association between Cutibacterium and TEWL. Furthermore, functional profiling using KEGG provided clues on the impact of Cutibacterium on the host skin barrier. This study enhances our understanding of the skin microbiome and its interplay with skin characteristics and highlights the importance of seasonal dynamics in shaping skin microbial composition.

Cross-alteration of murine skin and tick microbiome concomitant with pathogen transmission after Ixodes ricinus bite

BACKGROUND

Ticks are major vectors of diseases affecting humans such as Lyme disease or domestic animals such as anaplasmosis. Cross-alteration of the vertebrate host skin microbiome and the tick microbiome may be essential during the process of tick feeding and for the mechanism of pathogen transmission. However, it has been poorly investigated.

METHODS

We used mice bitten by field-collected ticks (nymphs and adult ticks) in different experimental conditions to investigate, by 16S rRNA gene metabarcoding, the impact of blood feeding on both the mouse skin microbiome and the tick microbiome. We also investigated by PCR and 16S rRNA gene metabarcoding, the diversity of microorganisms transmitted to the host during the process of tick bite at the skin interface and the dissemination of the pathogen in host tissues (blood, heart, and spleen).

RESULTS

Most of the commensal bacteria present in the skin of control mice were replaced during the blood-feeding process by bacteria originating from the ticks. The microbiome of the ticks was also impacted by the blood feeding. Several pathogens including tick-borne pathogens (Borrelia/Borreliella, Anaplasma, Neoehrlichia, Rickettsia) and opportunistic bacteria (Williamsia) were transmitted to the skin microbiome and some of them disseminated to the blood or spleen of the mice. In the different experiments of this study, skin microbiome alteration and Borrelia/Borreliella transmission were different depending on the tick stages (nymphs or adult female ticks).

CONCLUSIONS

Host skin microbiome at the bite site was deeply impacted by the tick bite, to an extent which suggests a role in the tick feeding, in the pathogen transmission, and a potentially important impact on the skin physiopathology. The diversified taxonomic profiles of the tick microbiome were also modified by the blood feeding. Video Abstract.

Common superficial and deep cutaneous bacterial infections in domestic animals: A review

The skin covers the external surface of animals, and it is constantly exposed to and inhabited by different microorganisms, including bacteria. Alterations in the skin barrier allow commensal and/or pathogenic bacteria to proliferate and penetrate deep into the lower layers of the skin. Being the first barrier to the external environment, the skin is prone to injuries, allowing the penetration of microorganisms that may lead to severe deep infections. Companion animals, especially dogs, are prone to bacterial infections, often secondary to allergic dermatitis. When environmental conditions are unfavorable, horses, cattle, sheep, and goats can develop superficial infections, such as those caused by Dermatophilus congolensis. Deep inflammation is commonly caused by Mycobacterium spp., which results in granulomatous to pyogranulomatous dermatitis and panniculitis. Likewise, bacteria such as Nocardia spp. and Actinomyces spp. can cause deep pyogranulomatous inflammation. Bacteria that lead to deep necrotizing lesions (eg, necrotizing fasciitis/flesh-eating bacteria) can be severe and even result in death. This review includes an overview of the most common cutaneous bacterial infections of domestic animals, highlighting the main features and histologic morphology of the bacteria, cutaneous structures involved, and the type of inflammatory infiltrates.

Skin microbiota secretomes modulate cutaneous innate immunity against Borrelia burgdorferi s.s

In Lyme borreliosis, the skin constitutes a major interface for the host, the bacteria and the tick. Skin immunity is provided by specialized immune cells but also by the resident cells: the keratinocytes and the fibroblasts. Discoveries on the role of the microbiome in the modulation of skin inflammation and immunity have reinforced the potential importance of the skin in vector-borne diseases. In this study, we analyzed in vitro the interaction of human primary keratinocytes and fibroblasts with Borrelia burgdorferi sensu stricto N40 in presence or absence of bacterial commensal supernatants. We aimed to highlight the role of resident skin cells and skin microbiome on the inflammation induced by B. burgdorferi s.s.. The secretomes of Staphylococcus epidermidis, Corynebacterium striatum and Cutibacterium acnes showed an overall increase in the expression of IL-8, CXCL1, MCP-1 and SOD-2 by fibroblasts, and of IL-8, CXCL1, MCP-1 and hBD-2 in the undifferentiated keratinocytes. Commensal bacteria showed a repressive effect on the expression of IL-8, CXCL1 and MCP-1 by differentiated keratinocytes. Besides the inflammatory effect observed in the presence of Borrelia on all cell types, the cutaneous microbiome appears to promote a rapid innate response of resident skin cells during the onset of Borrelia infection.

Antibacterial and anti-corona virus (229E) activity of Nigella sativa oil combined with photodynamic therapy based on methylene blue in wound infection: in vitro and in vivo study

Microbial skin infections, antibiotic resistance, and poor wound healing are major problems, and new treatments are needed. Our study targeted solving this problem with Nigella sativa (NS) oil and photodynamic therapy based on methylene blue (MB-PDT). Antibacterial activity and minimum inhibitory concentration (MIC) were determined via agar well diffusion assay and broth microdilution, respectively. Transmission electron microscopy (TEM) proved deformations in Staphylococcus aureus ATCC 6538. Gas chromatography-mass spectrometry identified useful compounds that were suggested to be responsible for the potency of the oil. NS oil was tested as an antivirus against low pathogenic coronavirus (229E). Therapies examined, MB-PDT, NS, and MB-PDT + NS oil, to accelerate wound healing. The antibacterial efficacy against S. aureus was promising, with a MIC of 12.5% and TEM showing injured cells treated with NS oil. This oil inhibited 229E virus up to 42.85% and 32.14%. All tested therapies were successful in accelerating wound healing. The most successful was combined therapy (MB-PDT + NS oil), with a faster healing time. The combined therapy (MB-PDT + NS oil) reduced bacterial counts, which may be a key factor in accelerating wound healing. Skin wound histology was investigated; blood hematology and biochemical analysis did not change significantly after the safe combination treatment. A combination treatment could facilitate healing in a simple and inexpensive way in the future. Based on the results of the in vitro and in vivo studies, it was determined that NS oil had antibacterial and anti-corona virus activity when used in conjunction with photodynamic treatment based on methylene blue to treat wound infections.

The influence of dietary patterns on skin bacterial diversity, composition, and co-occurrence relationships at forearm and neck sites of healthy Korean adults

AIMS

Diet and nutrition are important aspects of skin physiology and health. However, the influence of diet on the bacterial flora of different skin sites is not well understood. Therefore, we investigated the relationship between dietary patterns (DPs) and skin bacterial flora on the forearm (a dry site) and the neck (a sebaceous site) of healthy Korean adults.

METHODS AND RESULTS

In metagenomics analysis, Shannon and Simpson indices were higher on the forearm than on the neck and were negatively correlated with the two dominant species, Cutibacterium acnes and Staphylococcus epidermidis, on two skin sites. In addition, the Simpson index of the forearm was positively associated with DP1 (characterized by a high intake of vegetables, mushrooms, meat, fish and shellfish, seaweed, and fat and oil), while that on the neck was negatively associated with DP2 (characterized by a high intake of fast food). A high intake of DP1 was associated with a lower abundance of dominant species, including C. acnes, and higher degrees of the co-occurrence network, whereas a high intake of DP2 was associated with the opposite pattern.

CONCLUSIONS

Specific diets may impact both skin bacterial diversity and composition, as well as the co-occurrence of bacteria, which may vary across different skin sites.

Microbiome dysbiosis occurred in hypertrophic scars is dominated by S. aureus colonization

Background

The mechanisms of hypertrophic scar formation and its tissue inflammation remain unknown.

Methods

We collected 33 hypertrophic scar (HS) and 36 normal skin (NS) tissues, and detected the tissue inflammation and bacteria using HE staining, Gram staining, and transmission electronic microscopy (TEM), in situ hybridization and immunohistochemistry for MCP-1, TNF-α, IL-6 and IL-8. In addition, the samples were assayed by 16S rRNA sequencing to investigate the microbiota diversity in HS, and the correlation between the microbiota and the indices of Vancouver Scar Scale(VSS)score.

Results

HE staining showed that a dramatically increased number of inflammatory cells accumulated in HS compared with NS, and an enhanced number of bacteria colonies was found in HS by Gram staining, even individual bacteria could be clearly observed by TEM. In situ hybridization demonstrated that the bacteria and inflammation cells co-localized in the HS tissues, and immunohistochemistry indicated the expression of MCP-1, TNF-α, IL-6, and IL-8 were significantly upregulated in HS than that in NS. In addition, there was a significantly different microbiota composition between HS and NS. At the phylum level, Firmicutes was significantly higher in HS than NS. At the genus level, S. aureus was the dominant species, which was significantly higher in HS than NS, and was strongly correlated with VSS indices.

Conclusion

Microbiome dysbiosis, dominated by S. aureus, occurred in HS formation, which is correlated with chronic inflammation and scar formation, targeting the microbiome dysbiosis is perhaps a supplementary way for future scar management.

Metagenomic insights into the effects of cosmetics containing complex polysaccharides on the composition of skin microbiota in females

Introduction

The use of cosmetics has become a habit for women. However, their influence on the microbial diversity of the skin has rarely been studied.

Methods

Herein, the effect of cosmetics containing complex polysaccharides on the skin bacterial microbiota of female forehead and cheek areas was analyzed. Eighty volunteers were recruited and split into two groups (40 people each); one group was treated with cosmetics containing complex polysaccharides and the other with basic cream for 28 days. Skin samples were collected using sterilized cotton swabs, and 16S rDNA high-throughput sequencing was used to analyze the changes in skin bacterial microbiota composition before and after the intervention.

Results and discussion

A total of twenty-four phyla were detected in the forehead and cheek skin samples of 80 volunteers, the top three of which were Proteobacteria, Firmicutes, and Actinobacteria. The main genera of the forehead skin bacterial microbiota were Cutibacterium (11.1%), Acinetobacter (10.4%), Enterococcus (8.9%), Ralstonia (8.8%), and Staphylococcus (8.7%), while those of the cheek skin bacterial microbiota were Staphylococcus (20.0%), Ralstonia (8.7%), Propionibacterium (7.9%), Acinetobacter (7.2%), and Bifidobacterium (6.0%). Compared with basic cream, the use of cosmetics containing complex polysaccharides significantly increased the relative abundance of Staphylococcus and Bacillus in the forehead and cheek and reduced the relative abundance of Propionibacterium and Bifidobacterium. Thus, cosmetics containing complex polysaccharides could modify the composition of skin bacterial microbiota, which may help to maintain stable conditions of the skin.

Fish collagen peptides' modulating effect on human skin microbiota against pathogenic Staphylococcus aureus

Aim: The current research aims to design effective strategies to enhance the body's immune system against pathogenic bacteria. Methods: Skin commensals were isolated, identified and cultured in fish collagen peptides (FCPs). Results: After culturing in FCP, the skin commensals were used in a dose-dependent manner for Staphylococcus aureus in a dual-culture test, which showed significant growth inhibition of the pathogenic bacteria, which concluded that FCP induced the immune defense system of skin microbiota against pathogenic strains. Conclusion: Results have validated that fish collagen peptide plays a vital role in the growth of selected human skin flora and induces more defensive immunity against pathogenic S. aureus bacteria in dual-culture experimentation.

The feline skin microbiome: interrelationship between health and disease

PRACTICAL RELEVANCE

As with other species, the skin microbiome of cats has been assessed over the past few years utilizing modern technologies. This has resulted in the identification of many more bacterial and fungal organisms compared with what had been recorded historically on the skin in various states of health and disease using culture-based studies. This information is expanding the knowledge of how microbial communities are impacted by various changes in the skin health of cats. More specifically, how these microbial communities change in the face of health and disease, and how various therapeutic interventions affect the cutaneous microbiome, lends a greater understanding of disease pathogenesis and provides a growing area of research for correcting dysbiosis and improving feline skin health.

EVIDENCE BASE

Most studies on the feline skin microbiome thus far have been descriptive in nature. These provide a framework for the next level of investigations on how various states of health and disease impact the products produced by the cutaneous microbiome (ie, the cutaneous metabolome), as well as how targeted interventions may promote the restoration of balance.

AIMS

This review aims to summarize what is currently known about the feline cutaneous microbiome and its clinical implications. The role of the skin microbiome in health and disease, the current state of research in this area and the potential for future studies to produce targeted interventions for cats are a particular focus.

TIME Is Ticking for Cervical Cancer

Cervical cancer (CC) is a major health problem among reproductive-age females and comprises a leading cause of cancer-related deaths. Human papillomavirus (HPV) is the major risk factor associated with CC incidence. However, lifestyle is also a critical factor in CC pathogenesis. Despite HPV vaccination introduction, the incidence of CC is increasing worldwide. Therefore, it becomes critical to understand the CC tumor immune microenvironment (TIME) to develop immune cell-based vaccination and immunotherapeutic approaches. The current article discusses the immune environment in the normal cervix of adult females and its role in HPV infection. The subsequent sections discuss the alteration of different immune cells comprising CC TIME and their targeting as future therapeutic approaches.

Oral and Topical Probiotics and Postbiotics in Skincare and Dermatological Therapy: A Concise Review

The skin microbiota is a pivotal contributor to the maintenance of skin homeostasis by protecting it from harmful pathogens and regulating the immune system. An imbalance in the skin microbiota can lead to pathological conditions such as eczema, psoriasis, and acne. The balance of the skin microbiota components can be disrupted by different elements and dynamics such as changes in pH levels, exposure to environmental toxins, and the use of certain skincare products. Some research suggests that certain probiotic strains and their metabolites (postbiotics) may provide benefits such as improving the skin barrier function, reducing inflammation, and improving the appearance of acne-prone or eczema-prone skin. Consequently, in recent years probiotics and postbiotics have become a popular ingredient in skincare products. Moreover, it was demonstrated that skin health can be influenced by the skin-gut axis, and imbalances in the gut microbiome caused by poor diet, stress, or the use of antibiotics can lead to skin conditions. In this way, products that improve gut microbiota balance have been gaining attention from cosmetic and pharmaceutical companies. The present review will focus on the crosstalk between the SM and the host, and its effects on health and diseases.

Skin barrier immunology from early life to adulthood

Our skin has a unique barrier function, which is imperative for the body's protection against external pathogens and environmental insults. Although interacting closely and sharing many similarities with key mucosal barrier sites, such as the gut and the lung, the skin also provides protection for internal tissues and organs and has a distinct lipid and chemical composition. Skin immunity develops over time and is influenced by a multiplicity of different factors, including lifestyle, genetics, and environmental exposures. Alterations in early life skin immune and structural development may have long-term consequences for skin health. In this review, we summarize the current knowledge on cutaneous barrier and immune development from early life to adulthood, with an overview of skin physiology and immune responses. We specifically highlight the influence of the skin microenvironment and other host intrinsic, host extrinsic (e.g. skin microbiome), and environmental factors on early life cutaneous immunity.

Recent advances in understanding inflammatory acne: Deciphering the relationship between Cutibacterium acnes and Th17 inflammatory pathway

Acne vulgaris is a common chronic inflammatory skin disease of the pilosebaceous units. Four factors contribute to acne: hyperseborrhea and dysseborrhea, follicular hyperkeratinisation, skin microbiome dysbiosis and local immuno-inflammation. Recent key studies have highlighted a better understanding of the important role of Cutibacterium acnes (C. acnes) in the development of acne. Three major findings in the last decade include: (1) the ability of C. acnes to self-organize in a biofilm associated with a more virulent activity, (2) the loss of the C. acnes phylotype diversity and (3) the central role of the Th17 pathway in acne inflammation. Indeed, there is a close link between C. acnes and the activation of the Th17 immuno-inflammatory pathway at the initiation of acne development. These mechanisms are directly linked to the loss of C. acnes phylotype diversity during acne, with a predominance of the pro-pathogenic phylotype IA1. This specifically contributes to the induction of the Th17-mediated immuno-inflammatory response involving skin cells, such as keratinocytes, monocytes and sebocytes. These advancements have led to new insights into the underlying mechanisms which can be harnessed to develop novel treatments and diagnostic biomarkers. A major disadvantage of traditional treatment with topical antibiotics is that they induce cutaneous dysbiosis and antimicrobial resistance. Thus, future treatments would no longer aim to 'kill' C. acnes, but to maintain the skin microbiota balance allowing for tissue homeostasis, specifically, the restoration of C. acnes phylotype diversity. Here, we provide an overview of some of the key processes involved in the pathogenesis of acne, with a focus on the prominent role of C. acnes and the Th17-inflammatory pathways involved.

Comparative Analysis of the Symbiotic Microbiota in the Chinese Mitten Crab (Eriocheir sinensis): Microbial Structure, Co-Occurrence Patterns, and Predictive Functions

Symbiotic microorganisms in the digestive and circulatory systems are found in various crustaceans, and their essential roles in crustacean health, nutrition, and disease have attracted considerable interest. Although the intestinal microbiota of the Chinese mitten crab (Eriocheir sinensis) has been extensively studied, information on the symbiotic microbiota at various sites of this aquatic economic species, particularly the hepatopancreas and hemolymph, is lacking. This study aimed to comprehensively characterize the hemolymph, hepatopancreas, and intestinal microbiota of Chinese mitten crab through the high-throughput sequencing of the 16S rRNA gene. Results showed no significant difference in microbial diversity between the hemolymph and hepatopancreas (Welch t-test; p > 0.05), but their microbial diversity was significantly higher than that in the intestine (p < 0.05). Distinct differences were found in the structure, composition, and predicted function of the symbiotic microbiota at these sites. At the phylum level, the hemolymph and hepatopancreas microbiota were dominated by Proteobacteria, Firmicutes, and Acidobacteriota, followed by Bacteroidota and Actinobacteriota, whereas the gut microbiota was mainly composed of Firmicutes, Proteobacteria, and Bacteroidota. At the genus level, Candidatus Hepatoplasma, Shewanella, and Aeromonas were dominant in the hepatopancreas; Candidatus Bacilloplasma, Roseimarinus, and Vibrio were dominant in the intestine; Enterobacter, norank_Vicinamibacterales, and Pseudomonas were relatively high-abundance genera in the hemolymph. The composition and abundance of symbiotic microbiota in the hemolymph and hepatopancreas were extremely similar (p > 0.05), and no significant difference in functional prediction was found (p > 0.05). Comparing the hemolymph in the intestine and hepatopancreas, the hemolymph had lower variation in bacterial composition among individuals, having a more uniform abundance of major bacterial taxa, a smaller coefficient of variation, and the highest proportion of shared genera. Network complexity varied greatly among the three sites. The hepatopancreas microbiota was the most complex, followed by the hemolymph microbiota, and the intestinal microbiota had the simplest network. This study revealed the taxonomic and functional characteristics of the hemolymph, hepatopancreas, and gut microbiota in Chinese mitten crab. The results expanded our understanding of the symbiotic microbiota in crustaceans, providing potential indicators for assessing the health status of Chinese mitten crab.

Nanoparticles for Topical Application in the Treatment of Skin Dysfunctions-An Overview of Dermo-Cosmetic and Dermatological Products

Nanomaterials (NM) arouse interest in various fields of science and industry due to their composition-tunable properties and the ease of modification. They appear currently as components of many consumer products such as sunscreen, dressings, sports clothes, surface-cleaning agents, computer devices, paints, as well as pharmaceutical and cosmetics formulations. The use of NPs in products for topical applications improves the permeation/penetration of the bioactive compounds into deeper layers of the skin, providing a depot effect with sustained drug release and specific cellular and subcellular targeting. Nanocarriers provide advances in dermatology and systemic treatments. Examples are a non-invasive method of vaccination, advanced diagnostic techniques, and transdermal drug delivery. The mechanism of action of NPs, efficiency of skin penetration, and potential threat to human health are still open and not fully explained. This review gives a brief outline of the latest nanotechnology achievements in products used in topical applications to prevent and treat skin diseases. We highlighted aspects such as the penetration of NPs through the skin (influence of physical-chemical properties of NPs, the experimental models for skin penetration, methods applied to improve the penetration of NPs through the skin, and methods applied to investigate the skin penetration by NPs). The review summarizes various therapies using NPs to diagnose and treat skin diseases (melanoma, acne, alopecia, vitiligo, psoriasis) and anti-aging and UV-protectant nano-cosmetics.

Analysis of cutaneous bacterial microbiota of Thai patients with seborrheic dermatitis

Seborrheic dermatitis (SD) is a chronic inflammatory skin condition that occurs in body areas that contain profuse sebaceous glands. Skin microbiota are diverse across ethnic groups and its dysbiosis has been implicated in the pathogenesis of SD. Here, we reported the contribution of cutaneous bacterial microbiota to SD in the Thai population. Healthy individuals and patients with scalp SD were recruited into the study. Normal skin, scalp skin lesion (SL) and non-lesion sites (SNL) samples were collected using a tape stripping method and next-generation sequencing of 16S rRNA for microbiome analysis. Although bacterial diversity in all sample groups was not statistically different, a population of bacteria commonly found on skin of scalp showed signs of dysbiosis. Apart from the reduction of Corynebacterium spp., SD-specific microbiota was dominated by Firmicutes at taxa level and Pseudomonas spp., Staphylococcus spp. and Micrococcus spp. at genus level. The dysbiosis of the skin microbiota in SD was specifically described as an alteration of bacteria populations commonly found on scalp skin, implying that managing and controlling the cutaneous bacterial microbiome can alleviate and prevent SD and pave the way for the development of new SD treatments.

Cobamide Sharing Is Predicted in the Human Skin Microbiome

The skin microbiome is a key player in human health, with diverse functions ranging from defense against pathogens to education of the immune system. While recent studies have begun to shed light on the valuable role that skin microorganisms have in maintaining the skin barrier, a detailed understanding of the complex interactions that shape healthy skin microbial communities is limited. Cobamides, the vitamin B₁₂ class of cofactor, are essential for organisms across the tree of life. Because this vitamin is only produced by a limited fraction of prokaryotes, cobamide sharing is predicted to mediate community dynamics within microbial communities. Here, we provide the first large-scale metagenomic assessment of cobamide biosynthesis and utilization in the skin microbiome. We show that while numerous and diverse taxa across the major bacterial phyla on the skin encode cobamide-dependent enzymes, relatively few species encode de novo cobamide biosynthesis. We show that cobamide producers and users are integrated into the network structure of microbial communities across the different microenvironments of the skin and that changes in microbiome community structure and diversity are associated with the abundance of cobamide producers in the Corynebacterium genus, for both healthy and diseased skin states. Finally, we find that de novo cobamide biosynthesis is enriched only in Corynebacterium species associated with hosts, including those prevalent on human skin. We confirm that the cofactor is produced in excess through quantification of cobamide production by human skin-associated species isolated in the laboratory. Taken together, our results reveal the potential for cobamide sharing within skin microbial communities, which we hypothesize mediates microbiome community dynamics and host interactions. IMPORTANCE The skin microbiome is essential for maintaining skin health and function. However, the microbial interactions that dictate microbiome structure, stability, and function are not well understood. Here, we investigate the biosynthesis and use of cobamides, a cofactor needed by many organisms but only produced by select prokaryotes, within the human skin microbiome. We found that while a large proportion of skin taxa encode cobamide-dependent enzymes, only a select few encode de novo cobamide biosynthesis. Further, the abundance of cobamide-producing Corynebacterium species is associated with skin microbiome diversity and structure, and within this genus, de novo biosynthesis is enriched in host-associated species compared to environment-associated species. These findings identify cobamides as a potential mediator of skin microbiome dynamics and skin health.

Ecological Processes and Human Behavior Provide a Framework for Studying the Skin Microbial Metacommunity

Metacommunity theory dictates that a microbial community is supported both by local ecological processes and the dispersal of microbes between neighboring communities. Studies that apply this perspective to human-associated microbial communities are thus far limited to the gut microbiome. Yet, the skin serves as the primary barrier between the body and the external environment, suggesting frequent opportunities for microbial dispersal to the variable microbial communities that are housed across skin sites. This paper applies metacommunity theory to understand the dispersal of microbes to the skin from the physical and social environment, as well as between different skin sites on an individual's body. This includes highlighting the role of human behavior in driving microbial dispersal, as well as shaping physiological properties of skin that underscore local microbial community dynamics. By leveraging data from research on the skin microbiomes of amphibians and other animals, this paper provides recommendations for future research on the skin microbial metacommunity, including generating testable predictions about the ecological underpinnings of the skin microbiome.

Wnt-activating human skin organoid model of atopic dermatitis induced by Staphylococcus aureus and its protective effects by Cutibacterium acnes

A recently developed human PSC-derived skin organoid model has opened up new avenues for studying skin development, diseases, and regeneration. The current model has limitations since the generated organoids are enclosed, circular aggregates with an inside-out morphology with unintended off-target development of cartilage. Here, we first demonstrated that Wnt signaling activation resulted in larger organoids without off-target cartilage. We optimized further using an air-liquid interface (ALI) culture method to recapitulate structural features representative of human skin tissue. Finally, we used the ALI-skin organoid platform to model atopic dermatitis by Staphylococcus aureus (SA) colonization and infection. SA infection led to a disrupted skin barrier and increased production of epidermal- and dermal-derived inflammatory cytokines. Additionally, we found that pre-treatment with Cutibacterium acnes had a protective effect on SA-infected organoids. Thus, this ALI-skin organoid platform may be a useful tool for modeling human skin diseases and evaluating the efficacy of novel therapeutics.

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Wnt signaling activation results in larger organoids without off-target cartilage

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Air-liquid interface culture is used to recapitulate human skin tissue structure

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S. aureus infection damaged the skin barrier and elevated inflammatory cytokines

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Pre-treated Cutibacterium acnes had a protective effect on Staphylococcus aureus-infected organoids

Dual photothermal nanocomposites for drug-resistant infectious wound management

Management of antibiotic-resistant bacteria-induced skin infections for rapid healing remains a critical clinical challenge. Photothermal therapy, which uses mediated hyperthermia to combat such problems, has recently been recognised as a promising approach to take. In this study, bacterial cellulose-based photothermal membranes were designed and developed to combat bacterial infections and promote rapid wound healing. Polydopamine was incorporated into gold nanoparticles to produce superior dual-photothermal behaviour. The in vitro antibacterial efficacy of the prepared composite membranes against S. aureus, E. coli and methicillin-resistant Staphylococcus aureus (MRSA) could reach 99% under near-infrared (NIR) irradiation. In addition, the synthesised nanocomposite exhibited good biocompatibility in vitro as demonstrated by a cell survival ratio of >85%. The effectiveness of the composite membranes on wound healing was further investigated in a murine model of MRSA-infected wounds, focusing on the effect of photothermal temperature. According to the detailed therapeutic mechanism study undertaken, the composite membranes cause bacterial killing initially and promote the transition from the inflammatory phase to proliferation by suppressing pro-inflammatory cytokine production, promoting collagen deposition, and stimulating angiogenesis. Considering their remarkable effectiveness and facile fabrication process, it is expected that these novel materials could serve as competitive multifunctional dressings in the management of infectious wounds and accelerate the regeneration of damaged tissues related to abnormal immune responses.

Skin Injury Activates a Rapid TRPV1-Dependent Antiviral Protein Response

The skin serves as the interface between the body and the environment and plays a fundamental role in innate antimicrobial host immunity. Antiviral proteins (AVPs) are part of the innate host defense system and provide protection against viral pathogens. How breach of the skin barrier influences innate AVP production remains largely unknown. In this study, we characterized the induction and regulation of AVPs after skin injury and identified a key role of TRPV1 in this process. Transcriptional and phenotypic profiling of cutaneous wounds revealed that skin injury induces high levels of AVPs in both mice and humans. Remarkably, pharmacologic and genetic ablation of TRPV1-mediated nociception abrogated the induction of AVPs, including Oas2, Oasl2, and Isg15 after skin injury in mice. Conversely, stimulation of TRPV1 nociceptors was sufficient to induce AVP production involving the CD301b+ cells‒IL-27‒mediated signaling pathway. Using IL-27 receptor‒knockout mice, we show that IL-27 signaling is required in the induction of AVPs after skin injury. Finally, loss of TRPV1 signaling leads to increased viral infectivity of herpes simplex virus. Together, our data indicate that TRPV1 signaling ensures skin antiviral competence on wounding.

Immune checkpoint inhibitors unleash pathogenic immune responses against the microbiota

Immune checkpoint inhibitors (ICIs) are essential components of the cancer therapeutic armamentarium. While ICIs have demonstrated remarkable clinical responses, they can be accompanied by immune-related adverse events (irAEs). These inflammatory side effects are of unclear etiology and impact virtually all organ systems, with the most common being sites colonized by the microbiota such as the skin and gastrointestinal tract. Here, we establish a mouse model of commensal bacteria-driven skin irAEs and demonstrate that immune checkpoint inhibition unleashes commensal-specific inflammatory T cell responses. These aberrant responses were dependent on production of IL-17 by commensal-specific T cells and induced pathology that recapitulated the cutaneous inflammation seen in patients treated with ICIs. Importantly, aberrant T cell responses unleashed by ICIs were sufficient to perpetuate inflammatory memory responses to the microbiota months following the cessation of treatment. Altogether, we have established a mouse model of skin irAEs and reveal that ICIs unleash aberrant immune responses against skin commensals, with long-lasting inflammatory consequences.

Clinical Translation of Microbiome Research in Alopecia Areata: A New Perspective?

The continuous research advances in the microbiome field is changing clinicians’ points of view about the involvement of the microbiome in human health and disease, including autoimmune diseases such as alopecia areata (AA). Both gut and cutaneous dysbiosis have been considered to play roles in alopecia areata. A new approach is currently possible owing also to the use of omic techniques for studying the role of the microbiome in the disease by the deep understanding of microorganisms involved in the dysbiosis as well as of the pathways involved. These findings suggest the possibility to adopt a topical approach using either cosmetics or medical devices, to modulate or control, for example, the growth of overexpressed species using specific bacteriocins or postbiotics or with pH control. This will favour at the same time the growth of beneficial bacteria which, in turn, can impact positively both the structure of the scalp ecosystem on the host’s response to internal and external offenders. This approach, together with a “systemic” one, via oral supplementation, diet, or faecal transplantation, makes a reliable translation of microbiome research in clinical practice and should be taken into consideration every time alopecia areata is considered by a clinician.

Towards Understanding the Lymph Node Response to Skin Infection with Saprophytic Staphylococcus epidermidis

In individuals with lymphedema, diabetic foot, or other diseases, infections with saprophytes are common. The response of major cell subpopulations in the draining lymph nodes to skin infection with Staphylococcus epidermidis was assessed using the rat model. After massive subepidermal infection, a cytometric evaluation showed an increase in cytotoxic and helper T lymphocytes and major subpopulations of the innate immune response. Three weeks later, signs of inflammation reduction with an increase in the content of memory T helper lymphocytes and effector memory T cytotoxic lymphocytes were observed. After skin re-infection, a rapid response of cytotoxic, helper, and memory T lymphocytes, memory B lymphocytes and plasmablasts, and macrophages was detected. In addition, a reduction in the number of naïve B lymphocytes, activated MHC class II+ cells, and some cells of the innate immune system was observed. T regulatory lymphocyte response after the initial and secondary S. epidermidis skin infection was not detected. The morphometric evaluation showed significant changes in the main cell subpopulations in each functional zone of the node and then confirmed the efficient elimination of the administered antigen, as evidenced by the observations on day 28. Notably, after re-infection, the cellular response did not exceed the level after the initial infection and was reduced in many cell subpopulations. Understanding how the lymph nodes eliminate S. epidermidis can provide valuable insights into creating immunological therapies against infections with saprophytes.

The Gut-Skin Microbiota Axis and Its Role in Diabetic Wound Healing-A Review Based on Current Literature

Diabetic foot ulcers (DFU) are a growing concern worldwide as they pose complications in routine clinical practices such as diagnosis and management. Bacterial interactions on the skin surface are vital to the pathophysiology of DFU and may control delayed wound healing. The microbiota from our skin directly regulates cutaneous health and disease by interacting with the numerous cells involved in the wound healing mechanism. Commensal microbiota, in particular, interact with wound-repairing skin cells to enhance barrier regeneration. The observed microbes in DFU include Staphylococcus, Streptococcus, Corynebacterium, Pseudomonas, and several anaerobes. Skin commensal microbes, namely S. epidermidis, can regulate the gamma delta T cells and induce Perforin-2 expression. The increased expression of Perforin-2 by skin cells destroyed S. aureus within the cells, facilitating wound healing. Possible crosstalk between the human commensal microbiome and different cell types involved in cutaneous wound healing promotes the immune response and helps to maintain the barrier function in humans. Wound healing is a highly well-coordinated, complex mechanism; it can be devastating if interrupted. Skin microbiomes are being studied in relation to the gut-skin axis along with their effects on dermatologic conditions. The gut-skin axis illustrates the connection wherein the gut can impact skin health due to its immunological and metabolic properties. The precise mechanism underlying gut-skin microbial interactions is still unidentified, but the immune and endocrine systems are likely to be involved. Next-generation sequencing and the development of bioinformatics pipelines may considerably improve the understanding of the microbiome-skin axis involved in diabetic wound healing in a much more sophisticated way. We endeavor to shed light on the importance of these pathways in the pathomechanisms of the most prevalent inflammatory conditions including the diabetes wound healing, as well as how probiotics may intervene in the gut-skin axis.

Mammalian Epidermis: A Compendium of Lipid Functionality

Mammalian epidermis is a striking example of the role of lipids in tissue biology. In this stratified epithelium, highly specialized structures are formed that leverage the hydrophobic properties of lipids to form an impermeable barrier and protect the humid internal environment of the body from the dry outside. This is achieved through tightly regulated lipid synthesis that generates the molecular species unique to the tissue. Beyond their fundamental structural role, lipids are involved in the active protection of the body from external insults. Lipid species present on the surface of the body possess antimicrobial activity and directly contribute to shaping the commensal microbiota. Lipids belonging to a variety of classes are also involved in the signaling events that modulate the immune responses to environmental stress as well as differentiation of the epidermal keratinocytes themselves. Recently, high-resolution methods are beginning to provide evidence for the involvement of newly identified specific lipid molecules in the regulation of epidermal homeostasis. In this review we give an overview of the wide range of biological functions of mammalian epidermal lipids.

Skin-ny deeping: Uncovering immune cell behavior and function through imaging techniques

As the largest organ of the body, the skin is a key barrier tissue with specialized structures where ongoing immune surveillance is critical for protecting the body from external insults. The innate immune system acts as first-responders in a coordinated manner to react to injury or infections, and recent developments in intravital imaging techniques have made it possible to delineate dynamic immune cell responses in a spatiotemporal manner. We review here key studies involved in understanding neutrophil, dendritic cell and macrophage behavior in skin and further discuss how this knowledge collectively highlights the importance of interactions and cellular functions in a systems biology manner. Furthermore, we will review emerging imaging technologies such as high-content proteomic screening, spatial transcriptomics and three-dimensional volumetric imaging and how these techniques can be integrated to provide a systems overview of the immune system that will further our current knowledge and lead to potential exciting discoveries in the upcoming decades.