A novel non-contact communication between human keratinocytes and T cells: Exosomes derived from keratinocytes support superantigen-induced proliferation of resting T cells

Keratinocyte-derived extracellular vesicles induce macrophage polarization toward an M1-like phenotype

Multiple reports have shown an effect of keratinocyte-derived extracellular vesicles (EVs) on keratinocytes and other cell types. However, the contribution of keratinocyte-derived EVs under physiological and pathological conditions is not fully elucidated. Therefore, whether there is an effect of EVs on macrophages in cervical cancer (CC) is also unknown. Here, we evaluated the effect of tumor and non-tumor keratinocyte-derived EVs on the polarization of peripheral blood mononuclear cells (PBMCs)-derived macrophages and THP-1 cell line. Flow cytometric evaluation of macrophages cultured in the presence of keratinocyte-derived EVs mainly indicated an increase in classical activation markers CD80 and CD86 (M1 phenotype) and little or no modification of alternative activation markers (M2 phenotype). ELISA evaluation of macrophage supernatants revealed an increase in the secretion of proinflammatory cytokines such as IL-1β and IL-6. On the other hand, TGF-β was not significantly modified and only EVs derived from non-cancerous keratinocytes induced a significant increase in IL-10. The expression levels of transcripts associated with the M1 phenotype were also evaluated by qRT-PCR with similar results to ELISA for TGF-β and IL-10; but also an increase in the expression of HLA-DRα and TNF-α was observed, and no statistically significant changes in ARG1. The ROS production was also evaluated and this increase mainly in macrophages treated with CC keratinocytes-derived EVs. So, our results suggest that the uptake of EVs derived from released by non-tumor and cervical cancer keratinocytes promotes in macrophages their polarization to an M1-like phenotype.

Roles for Exosomes in the Pathogenesis, Drug Delivery and Therapy of Psoriasis

Psoriasis is a chronic, recurrent and inflammatory skin disease. Although conventional immunosuppressants can ameliorate psoriatic symptoms, it tends to relapse over time. Previous studies have shown that exosomes from both immune and non-immune cells participate in psoriatic immunopathology. The biologically active cargoes in exosomes accelerate psoriasis progression by altering gene profiles and signaling pathways of neighboring cells. On the other hand, exosomes can be utilized as drug delivery platforms for psoriasis treatment. Especially, engineered exosomes may serve as drug delivery systems for effective delivery of proteins, nucleic acids or other drugs due to their low immunogenicity, good stability and ability to fuse with target cells. Therefore, investigation into the mechanisms underlying intercellular communications mediated by exosomes in skin lesions likely helps design drugs for therapy of psoriasis. In this review, we have summarized recent advances in the biogenesis of exosomes and their potential roles in the pathogenesis and treatment of psoriasis and further discussed their challenges and future directions in psoriasis treatment. In particular, this review highlights the immunoregulatory function of exosomes derived from immune or non-immune cells and exosome-based therapeutic applications in psoriasis, including their drug delivery systems. Thus, this review may help accelerate applications of exosomes for drug delivery and treatment of psoriasis.

Keratinocytes stimulate MAIT cells to produce granzyme B via MR1 and cytokines in oral lichen planus

OBJECTIVE

Oral lichen planus (OLP) is a chronic inflammatory disease characterized by a dense T-cell infiltration and the degeneration of basal keratinocytes. The potential functions of mucosal associated invariant T (MAIT) cells in OLP have been analyzed in our previous study. Keratinocytes under proinflammatory conditions have been demonstrated to activate T cells. This study was aimed to investigate how keratinocytes stimulate MAIT cells in OLP, and to explore the role of activated MAIT cells on keratinocytes.

METHODS AND RESULTS

Increased MAIT cells and higher activation marker CD69 were detected in OLP lesions by flow cytometry. The enhanced expression of MHC class I-like molecule (MR1) required for MAIT cell activation in the epithelial layer of OLP lesions was determined by immunohistochemistry. Keratinocytes treated by 5-A-RU prodrug and lipopolysaccharide, respectively, exhibited higher expression of MR1 and secretion of IL-18. In direct coculture systems consisting of keratinocytes and peripheral blood mononuclear cells, both 5-A-RU prodrug-pretreated keratinocytes and lipopolysaccharide-pretreated keratinocytes activated MAIT cells to secrete granzyme B, contributing to elevated keratinocyte apoptosis.

CONCLUSIONS

Keratinocytes were capable to activate MAIT cells via MR1 and cytokines in OLP, and granzyme B produced by activated MAIT cells intensified keratinocyte apoptosis, engaging in the pathogenesis of OLP.

Exosome-derived microRNAs: emerging players in vitiligo

Exosome-derived microRNAs (miRNAs) are biomacromolecules and nanoscale extracellular vesicles originating from intracellular compartments that are secreted by most cells into the extracellular space. This review examines the formation and function of exosomal miRNAs in biological information transfer, explores the pathogenesis of vitiligo, and highlights the relationship between exosomal miRNAs and vitiligo. The aim is to deepen the understanding of how exosomal miRNAs influence immune imbalance, oxidative stress damage, melanocyte-keratinocyte interactions, and melanogenesis disorders in the development of vitiligo. This enhanced understanding may contribute to the development of potential diagnostic and therapeutic options for vitiligo.

The implications of exosomes in psoriasis: disease: emerging as new diagnostic markers and therapeutic targets

As the largest human organ, the skin is continuously exposed to various external and internal triggers that affect body homeostasis. Psoriasis is a persistent inflammatory skin condition that has a major bearing on patients' physiological functioning as well as their mental well-being. It is an autoimmune disorder and has been the focus of extensive research efforts in recent years. Cells secrete exosomes into the environment surrounding them, which comprises a lipid bilayer. The movement of cellular components like microRNAs, mRNAs, DNA, lipids, metabolites, and cell-surface proteins is mediated by exosomes. Exosomes are crucial for inducing communication between cells. There has been extensive study of exosomes, both preclinical and clinical, looking at their potential role in autoimmune diseases. Besides the role that they play in the body's basic processes, exosomes are also considered an increasingly essential part as diagnostic and therapeutic agents. In the following article, we conduct a literature review of current studies related to molecular and structural aspects of exosomes. We emphasis on the function of exosomes in pathogenesis, as well as the possibility of their usage in medicinal applications and as biomarkers.

Keratinocyte-derived small extracellular vesicles supply antigens for CD1a-resticted T cells and promote their type 2 bias in the context of filaggrin insufficiency

Introduction

Exosome-enriched small extracellular vesicles (sEVs) are nanosized organelles known to participate in long distance communication between cells, including in the skin. Atopic dermatitis (AD) is a chronic inflammatory skin disease for which filaggrin (FLG) gene mutations are the strongest genetic risk factor. Filaggrin insufficiency affects multiple cellular function, but it is unclear if sEV-mediated cellular communication originating from the affected keratinocytes is also altered, and if this influences peptide and lipid antigen presentation to T cells in the skin.

Methods

Available mRNA and protein expression datasets from filaggrin-insufficient keratinocytes (shFLG), organotypic models and AD skin were used for gene ontology analysis with FunRich tool. sEVs secreted by shFLG and control shC cells were isolated from conditioned media by differential centrifugation. Mass spectrometry was carried out for lipidomic and proteomic profiling of the cells and sEVs. T cell responses to protein, peptide, CD1a lipid antigens, as well as phospholipase A2-digested or intact sEVs were measured by ELISpot and ELISA.

Results

Data analysis revealed extensive remodeling of the sEV compartment in filaggrin insufficient keratinocytes, 3D models and the AD skin. Lipidomic profiles of shFLGsEV showed a reduction in the long chain (LCFAs) and polyunsaturated fatty acids (PUFAs; permissive CD1a ligands) and increased content of the bulky headgroup sphingolipids (non-permissive ligands). This resulted in a reduction of CD1a-mediated interferon-γ T cell responses to the lipids liberated from shFLG-generated sEVs in comparison to those induced by sEVs from control cells, and an increase in interleukin 13 secretion. The altered sEV lipidome reflected a generalized alteration in the cellular lipidome in filaggrin-insufficient cells and the skin of AD patients, resulting from a downregulation of key enzymes implicated in fatty acid elongation and desaturation, i.e., enzymes of the ACSL, ELOVL and FADS family.

Discussion

We determined that sEVs constitute a source of antigens suitable for CD1a-mediated presentation to T cells. Lipids enclosed within the sEVs secreted on the background of filaggrin insufficiency contribute to allergic inflammation by reducing type 1 responses and inducing a type 2 bias from CD1a-restricted T cells, thus likely perpetuating allergic inflammation in the skin.

Keratinocyte-derived circulating microRNAs in extracellular vesicles: a novel biomarker of psoriasis severity and potential therapeutic target

BACKGROUND

Psoriasis is a chronic inflammatory disorder characterized by pathogenic hyperproliferation of keratinocytes and immune dysregulation. Currently, objective evaluation tools reflecting the severity of psoriasis are insufficient. MicroRNAs in extracellular vesicles (EV miRNAs) have been shown to be potential biomarkers for various inflammatory diseases. Our objective was to investigate the possibility of plasma-derived EV miRNAs as a marker for the psoriasis disease severity.

METHODS

EVs were extracted from the plasma of 63 patients with psoriasis and 12 with Behçet's disease. We performed next-generation sequencing of the plasma-derived EV miRNAs from the psoriasis patients. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to validate the level of EV miRNA expression. In situ hybridization was used to discern the anatomical location of miRNAs. qRT-PCR, western blotting, and cell counting kits (CCKs) were used to investigate IGF-1 signaling in cells transfected with miRNA mimics.

RESULTS

We identified 19 differentially expressed EV miRNAs and validated the top three up-and down-regulated EV miRNAs. Among these, miR-625-3p was significantly increased in patients with severe psoriasis in both plasma and skin and most accurately distinguished moderate-to-severe psoriasis from mild-to-moderate psoriasis. It was produced and secreted by keratinocytes upon stimulation. We also observed a significant intensification of IGF-1 signalling and increased cell numbers in the miR-625-3p mimic transfected cells.

CONCLUSIONS

We propose keratinocyte-derived EV miR-625-3p as a novel and reliable biomarker for estimating the severity of psoriasis. This biomarker could objectively evaluate the severity of psoriasis in the clinical setting and might serve as a potential therapeutic target. Trial registration None.

The skin sensitization adverse outcome pathway: exploring the role of mechanistic understanding for higher tier risk assessment

For over a decade, the skin sensitization Adverse Outcome Pathway (AOP) has served as a useful framework for development of novel in chemico and in vitro assays for use in skin sensitization hazard and risk assessment. Since its establishment, the AOP framework further fueled the existing efforts in new assay development and stimulated a plethora of activities with particular focus on validation, reproducibility and interpretation of individual assays and combination of assay outputs for use in hazard/risk assessment. In parallel, research efforts have also accelerated in pace, providing new molecular and dynamic insight into key events leading to sensitization. In light of novel hypotheses emerging from over a decade of focused research effort, mechanistic evidence relating to the key events in the skin sensitization AOP may complement the tools currently used in risk assessment. We reviewed the recent advances unraveling the complexity of molecular events in sensitization and signpost the most promising avenues for further exploration and development of useful assays.

The Regulation of Exosome Generation and Function in Physiological and Pathological Processes

Exosomes, a type of extracellular vesicle with a diameter of approximately 100 nm that is secreted by all cells, regulate the phenotype and function of recipient cells by carrying molecules such as proteins, nucleic acids, and lipids and are important mediators of intercellular communication. Exosomes are involved in various physiological and pathological processes such as immunomodulation, angiogenesis, tumorigenesis, metastasis, and chemoresistance. Due to their excellent properties, exosomes have shown their potential application in the clinical diagnosis and treatment of disease. The functions of exosomes depend on their biogenesis, uptake, and composition. Thus, a deeper understanding of these processes and regulatory mechanisms can help to find new targets for disease diagnosis and therapy. Therefore, this review summarizes and integrates the recent advances in the regulatory mechanisms of the entire biological process of exosomes, starting from the formation of early-sorting endosomes (ESCs) by plasma membrane invagination to the release of exosomes by fusion of multivesicular bodies (MVBs) with the plasma membrane, as well as the regulatory process of the interactions between exosomes and recipient cells. We also describe and discuss the regulatory mechanisms of exosome production in tumor cells and the potential of exosomes used in cancer diagnosis and therapy.

The Relationship between Reactive Oxygen Species and the cGAS/STING Signaling Pathway in the Inflammaging Process

During Inflammaging, a dysregulation of the immune cell functions is generated, and these cells acquire a senescent phenotype with an increase in pro-inflammatory cytokines and ROS. This increase in pro-inflammatory molecules contributes to the chronic inflammation and oxidative damage of biomolecules, classically observed in the Inflammaging process. One of the most critical oxidative damages is generated to the host DNA. Damaged DNA is located out of the natural compartments, such as the nucleus and mitochondria, and is present in the cell's cytoplasm. This DNA localization activates some DNA sensors, such as the cGAS/STING signaling pathway, that induce transcriptional factors involved in increasing inflammatory molecules. Some of the targets of this signaling pathway are the SASPs. SASPs are secreted pro-inflammatory molecules characteristic of the senescent cells and inducers of ROS production. It has been suggested that oxidative damage to nuclear and mitochondrial DNA generates activation of the cGAS/STING pathway, increasing ROS levels induced by SASPs. These additional ROS increase oxidative DNA damage, causing a loop during the Inflammaging. However, the relationship between the cGAS/STING pathway and the increase in ROS during Inflammaging has not been clarified. This review attempt to describe the potential connection between the cGAS/STING pathway and ROS during the Inflammaging process, based on the current literature, as a contribution to the knowledge of the molecular mechanisms that occur and contribute to the development of the considered adaptative Inflammaging process during aging.

SOX9 in Keratinocytes Regulates Claudin 2 Transcription during Skin Aging

In order to prove that SOX9 in keratinocytes regulates claudin 2 transcription during skin aging, the skin of 8-week-old and 24-month-old mice is sequenced to obtain a differentially expressed gene SOX9. The gene is mainly expressed in keratinocytes, and it increases first and then decreases from newborn to aging. Six core sequences of SOX9 and claudin 2 are predicted from Jaspar. The double Luciferase Report shows that overexpression of SOX9 induces the full-length promoter of claudin 2 significantly and has no effect on the mutation and cleavage plasmid without SOX9 response. Claudin 2 is consistent with SOX9 in the skin of mice of different ages, and SOX9 is strongly positively correlated with claudin 2. Finally, overexpression of SOX9 and claudin 2 will delay PM2.5-induced keratinocyte senescence. The silencing of claudin 2 leads to the loss of SOX9 function. It is clearly evident that SOX9 can affect the transcription of claudin 2, which increases first and then decreases in the process of mice from newborn to aging. SOX9 inhibits proinflammatory mediators, increases antioxidant capacity, and restores keratin differentiation. It can effectively prevent melanin deposition and delay aging.

Role of exosomes in skin diseases

BACKGROUND

Exosomes, as a family member of extracellular vesicles, are cell-secreted nanoscale structures that play pivotal roles in regulating physiological and pathophysiological processes of the skin. Exosomes induce communication between cells and are responsible for transporting cellular components such as microRNAs, mRNAs, DNA, lipids, metabolites, and cell-surface proteins. Numerous preclinical and clinical trials searched the contribution of exosomes to skin functions and disorders. Thus, exosomes are gaining increasing attention within investigational dermatology. In advance, stem-cell-derived exosomes were integrated into the functional cosmetics industry nominated as cell-free regenerative medicine.

OBJECTIVE

This review aims to demonstrate the roles of exosomes in inflammatory skin disorders, stem cell, and tumor biology through a comprehensive evaluation of the diagnostic, prognostic, and therapeutic perspectives.

METHODS

A comprehensive literature search was performed using electronic online databases "PubMed" and "Google Scholar" using key words ''exosomes'', ''skin'', ''wound healing''.

CONCLUSION

Exosomes are regarded as promising diagnostic and prognostic biomarkers for various skin diseases. Future prospects are repurposing exosomes to treat skin disorders, either as drug carriers or drugs themselves.

Exposure of Keratinocytes to Candida Albicans in the Context of Atopic Milieu Induces Changes in the Surface Glycosylation Pattern of Small Extracellular Vesicles to Enhance Their Propensity to Interact With Inhibitory Siglec Receptors

Candida albicans (C. albicans) infection is a potential complication in the individuals with atopic dermatitis (AD) and can affect clinical course of the disease. Here, using primary keratinocytes we determined that atopic milieu promotes changes in the interaction of small extracellular vesicles (sEVs) with dendritic cells and that this is further enhanced by the presence of C. albicans. sEV uptake is largely dependent on the expression of glycans on their surface; modelling of the protein interactions indicated that recognition of this pathogen through C. albicans-relevant pattern recognition receptors (PRRs) is linked to several glycosylation enzymes which may in turn affect the expression of sEV glycans. Here, significant changes in the surface glycosylation pattern, as determined by lectin array, could be observed in sEVs upon a combined exposure of keratinocytes to AD cytokines and C. albicans. This included enhanced expression of multiple types of glycans, for which several dendritic cell receptors could be proposed as binding partners. Blocking experiments showed predominant involvement of the inhibitory Siglec-7 and -9 receptors in the sEV-cell interaction and the engagement of sialic acid-containing carbohydrate moieties on the surface of sEVs. This pointed on ST6 β-Galactoside α-2,6-Sialyltransferase 1 (ST6GAL1) and Core 1 β,3-Galactosyltransferase 1 (C1GALT1) as potential enzymes involved in the process of remodelling of the sEV surface glycans upon C. albicans exposure. Our results suggest that, in combination with atopic dermatitis milieu, C. albicans promotes alterations in the glycosylation pattern of keratinocyte-derived sEVs to interact with inhibitory Siglecs on antigen presenting cells. Hence, a strategy aiming at this pathway to enhance antifungal responses and restrict pathogen spread could offer novel therapeutic options for skin candidiasis in AD.

Effects of keratinocyte-derived and fibroblast-derived exosomes on human epidermal melanocytes

BACKGROUND

Exosomes have been demonstrated to carry proteins, membrane lipids, mRNAs and microRNAs which can be transferred to surrounding cells and regulate the functions of those recipient cells.

OBJECTIVES

The objective of the study was to investigate the effects of exosomes released by keratinocytes and fibroblasts on the proliferation, tyrosinase activity and melanogenesis of melanocytes.

METHODS

Melanocytes, keratinocytes and fibroblasts obtained from human foreskin were cultured and exosomes secreted by keratinocytes and fibroblasts were harvested from the culture supernatants by ultracentrifugation. Each exosome fraction was divided into two parts; one part was subjected to high-throughput sequencing using an Illumina HiSeq sequencer to characterize the microRNA expression profiles, while the other part was labeled with the fluorescent dye PKH67 and was then co-cultivated with epidermal melanocytes.

RESULTS

High-throughput sequencing analysis showed 168 differentially expressed microRNA within exosomes derived from keratinocytes and from fibroblasts, 97 of those being up-regulated with the other 71 down-regulated. Gene ontology analysis showed that the target genes responsible for these differentially expressed microRNAs were mainly enriched in the protein-binding region of molecular functions. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that target genes regulated by differentially expressed microRNA were mainly involved in mitogen-activated protein kinase (MAPK) signaling pathway, Ras signaling pathway, cAMP signaling pathway and Wnt signaling pathway. Keratinocyte-derived exosomes were taken up by melanocytes co-cultured with them and promoted the proliferation, tyrosinase activity and melanin synthesis of those melanocytes. However, fibroblast-derived exosomes had no similar effects on melanocytes.

CONCLUSION

Keratinocyte-derived exosomes but not fibroblast-derived exosomes were taken up by melanocytes in co-culture and significantly stimulated their proliferation, tyrosinase activity and melanin synthesis. Those different effects may be mainly due to the differential expression of microRNAs in exosomes derived from the different types of cells.

LIMITATIONS

Electron microscopy of the obtained exosomes and in-depth study of apparently differentially expressed microRNAs were not performed.

Applications, challenges and prospects of mesenchymal stem cell exosomes in regenerative medicine

Recent advances in the identification and application of different stem cell types have offered alternative therapeutic approaches for clinicians. The lack of successful engraftment, migration into the injured site, loss of functionality and viability, ethical issues, shortage of donated allogeneic stem cells and the possibility of transmission of infectious are the main challenges associated with direct cell transplantation. The discovery and research on exosomes have led to the rise of hopes for the alleviation of different pathologies in regenerative medicine. Exo are nano-sized extracellular vesicles (40-150 nm) and released by each type. These nanoparticles participate in cell-to-cell communication in a paracrine manner. It is thought that the application of Exo can circumvent several drawbacks related to whole-cell therapies. Because of their appropriate size and stability, Exo are touted as therapeutic bullets transferring signaling factors into the acceptor cells in a paracrine manner. Despite these advantages, technologies associated with Exo isolation and purification are challenging because of heterogeneity in exosomal size and cargo. The lack of standard GMP-grade protocols is the main hurdle that limits the extensive application of Exo in the clinical setting. Here, the authors aimed to inspire a logical and realistic vision about problems associated with Exo application in regenerative medicine.

The Role of Non-Immune Cell-Derived Extracellular Vesicles in Allergy

Extracellular vesicles (EVs), and especially exosomes, have been shown to mediate information exchange between distant cells; this process directly affects the biological characteristics and functionality of the recipient cell. As such, EVs significantly contribute to the shaping of immune responses in both physiology and disease states. While vesicles secreted by immune cells are often implicated in the allergic process, growing evidence indicates that EVs from non-immune cells, produced in the stroma or epithelia of the organs directly affected by inflammation may also play a significant role. In this review, we provide an overview of the mechanisms of allergy to which those EVs contribute, with a particular focus on small EVs (sEVs). Finally, we also give a clinical perspective regarding the utilization of the EV-mediated communication route for the benefit of allergic patients.

Keratinocytes Regulate the Threshold of Inflammation by Inhibiting T Cell Effector Functions

Whilst the importance of keratinocytes as a first-line defense has been widely investigated, little is known about their interactions with non-resident immune cells. In this study, the impact of human keratinocytes on T cell effector functions was analyzed in an antigen-specific in vitro model of allergic contact dermatitis (ACD) to nickel sulfate. Keratinocytes partially inhibited T cell proliferation and cytokine production. This effect was dependent on the keratinocyte/T cell ratio and was partially reversible by increasing the number of autologous dendritic cells. The inhibition of T cell proliferation by keratinocytes was independent of the T cell subtype and antigen presentation by different professional antigen-presenting cells. Autologous and heterologous keratinocytes showed comparable effects, while the fixation of keratinocytes with paraformaldehyde abrogated the immunosuppressive effect. The separation of keratinocytes and T cells by a transwell chamber, as well as a cell-free keratinocyte supernatant, inhibited T cell effector functions to the same amount as directly co-cultured keratinocytes, thus proving that soluble factor/s account for the observed suppressive effects. In conclusion, keratinocytes critically control the threshold of inflammatory processes in the skin by inhibiting T cell proliferation and cytokine production.

Using chemiluminescence imaging of cells (CLIC) for relative protein quantification

Cell physiology and cellular responses to external stimuli are partly controlled through protein binding, localization, and expression level. Thus, quantification of these processes is pivotal in understanding cellular biology and disease pathophysiology. However, it can be methodologically challenging. Immunofluorescence is a powerful technique, yet quantification by this method can be hampered by auto-fluorescence. Here we describe a simple, sensitive and robust chemiluminescence-based immunoassay (chemiluminescence imaging of cells; CLIC) for relative quantification of proteins. We first employed this method to quantify complement activation in cultured mammalian cells, and to quantify membrane protein expression, shedding, binding and internalization. Moreover, through specific membrane permeabilization we were able to quantify both cytosolic and nuclear proteins, and their translocation. We validated the CLIC quantification method by performing parallel experiments with other quantification methods like ELISA, qPCR, and immunofluorescence microscopy. The workflow of the immunoassay was found to be advantageous in certain instances when compared to these quantification methods. Since the reagents used for CLIC are common to other immunoassays with no need for specialized equipment, and due to the good linearity, dynamic range and signal stability inherent to chemiluminescence, we suggest that this assay is suitable for both small scale and high throughput relative protein quantification studies in whole cells.

Shedding light on the role of keratinocyte-derived extracellular vesicles on skin-homing cells

Extracellular vesicles (EVs) are secretory lipid membranes with the ability to regulate cellular functions by exchanging biological components between different cells. Resident skin cells such as keratinocytes, fibroblasts, melanocytes, and inflammatory cells can secrete different types of EVs depending on their biological state. These vesicles can influence the physiological properties and pathological processes of skin, such as pigmentation, cutaneous immunity, and wound healing. Since keratinocytes constitute the majority of skin cells, secreted EVs from these cells may alter the pathophysiological behavior of other skin cells. This paper reviews the contents of keratinocyte-derived EVs and their impact on fibroblasts, melanocytes, and immune cells to provide an insight for better understanding of the pathophysiological mechanisms of skin disorders and their use in related therapeutic approaches.

Extracellular vesicles in Inflammatory Skin Disorders: from Pathophysiology to Treatment

Extracellular vesicles (EVs), naturally secreted by almost all known cell types into extracellular space, can transfer their bioactive cargos of nucleic acids and proteins to recipient cells, mediating cell-cell communication. Thus, they participate in many pathogenic processes including immune regulation, cell proliferation and differentiation, cell death, angiogenesis, among others. Cumulative evidence has shown the important regulatory effects of EVs on the initiation and progression of inflammation, autoimmunity, and cancer. In dermatology, recent studies indicate that EVs play key immunomodulatory roles in inflammatory skin disorders, including psoriasis, atopic dermatitis, lichen planus, bullous pemphigoid, systemic lupus erythematosus, and wound healing. Importantly, EVs can be used as biomarkers of pathophysiological states and/or therapeutic agents, both as carriers of drugs or even as a drug by themselves. In this review, we will summarize current research advances of EVs from different cells and their implications in inflammatory skin disorders, and further discuss their future applications, updated techniques, and challenges in clinical translational medicine.

Small Extracellular Vesicles Containing miR-381-3p from Keratinocytes Promote T Helper Type 1 and T Helper Type 17 Polarization in Psoriasis

T helper cells are crucial for psoriasis pathogenesis. Communication between T cells and psoriatic keratinocytes (KCs) helps drive the Th1 and Th17 response, but the underlying mechanism is not well-understood. Small extracellular vesicles (sEVs) are emerging mediators of intercellular communication. Here, we investigated the role of KC-derived sEVs in the Th1 and Th17 response in psoriasis. We isolated and characterized sEVs from KCs under normal (untreated) and psoriatic (cytokine-treated) conditions. sEVs under both conditions exhibited a cup-shaped morphology and expressed markers CD63 and CD81. sEVs from cytokine-treated KCs can be taken up by CD4⁺T cells, leading to the induction of Th1 and Th17 polarization. Small RNA sequencing revealed that miR-381-3p was significantly increased in sEVs from cytokine-treated KCs and in CD4⁺T cells from patients with psoriasis. Moreover, sEVs-containing miR-381-3p was responsible for sEVs-induced Th1 and Th17 polarization. We further found that the miR-381-3p targeted to the 3' untranslated region of E3 ubiquitin-ligase UBR5 and stabilized RORγt protein expression. It also targeted to the 3' untranslated region of FOXO1, associated with activated T-bet and RORγt transcription. Taken together, we propose that psoriatic KCs transfer miR-381-3p to CD4⁺T cells through sEVs, inducing Th1 and Th17 polarization and promoting psoriasis development. Our findings motivate future studies of KC-derived sEVs or their specific cargoes as therapeutic candidates for psoriasis.

Advances in Research on the Bioactivity of Alginate Oligosaccharides

Alginate is a natural polysaccharide present in various marine brown seaweeds. Alginate oligosaccharide (AOS) is a degradation product of alginate, which has received increasing attention due to its low molecular weight and promising biological activity. The wide-ranging biological activity of AOS is closely related to the diversity of their structures. AOS with a specific structure and distinct applications can be obtained by different methods of alginate degradation. This review focuses on recent advances in the biological activity of alginate and its derivatives, including their anti-tumor, anti-oxidative, immunoregulatory, anti-inflammatory, neuroprotective, antibacterial, hypolipidemic, antihypertensive, and hypoglycemic properties, as well as the ability to suppress obesity and promote cell proliferation and regulate plant growth. We hope that this review will provide theoretical basis and inspiration for the high-value research developments and utilization of AOS-related products.

Keratinocyte exosomes activate neutrophils and enhance skin inflammation in psoriasis

Psoriasis is a chronic inflammatory skin disease that severely affects patients physiologically and psychologically. The pathogenesis involving communication between psoriatic keratinocytes and infiltrated immune cells such as neutrophils remains unclear. Exosomes are emerging mediators of intercellular communication. Herein we aim to investigate the release and function of psoriatic keratinocyte exosomes, which have not been illustrated to any extent. We first isolated exosomes from both healthy and psoriasis-like keratinocytes treated with psoriatic cytokine cocktail. These exosomes were observed to be endocytosed by neutrophils. Unlike non-cytokine-treated keratinocyte exosomes, cytokine-treated keratinocyte exosomes significantly induced NETosis (the process by which neutrophils produce and release neutrophil extracellular traps) and the expressions of IL-6, IL-8, and TNF-α in neutrophils. Proteomic analysis showed that cytokine-treated keratinocyte exosomes exhibited a specific protein profile with proteins enriched in immune-related pathways. We then confirmed that NF-κB and p38 MAPK signaling pathways were activated in neutrophils stimulated by cytokine-treated keratinocyte exosomes and were responsible for the expressions of proinflammatory factors mentioned above. Finally, we verified in vivo that cytokine-treated keratinocyte exosomes participated in the skin lesion development of imiquimod-induced psoriasis-like mouse model. Collectively, we reveal that the release of exosomes works as a way of keratinocyte-neutrophil communication, indicating that keratinocyte exosomes, with their specific cargoes, are therapeutic candidates for psoriasis.-Jiang, M., Fang, H., Shao, S., Dang, E., Zhang, J., Qiao, P., Yang, A., Wang, G. Keratinocyte exosomes activate neutrophils and enhance skin inflammation in psoriasis.

Exosome swarms eliminate airway pathogens and provide passive epithelial immunoprotection through nitric oxide

BACKGROUND

Nasal mucosa-derived exosomes (NMDEs) harbor immunodefensive proteins and are capable of rapid interepithelial protein transfer.

OBJECTIVES

We sought to determine whether mucosal exposure to inhaled pathogens stimulates a defensive swarm of microbiocidal exosomes, which also donate their antimicrobial cargo to adjacent epithelial cells.

METHODS

We performed an institutional review board-approved study of healthy NMDE secretion after Toll-like receptor (TLR) 4 stimulation by LPS (12.5 μg/mL) in the presence of TLR4 inhibitors. Interepithelial transfer of exosomal nitric oxide (NO) synthase and nitric oxide was measured by using ELISAs and NO activity assays. Exosomal antimicrobial assays were performed with Pseudomonas aeruginosa. Proteomic analyses were performed by using SOMAscan.

RESULTS

In vivo and in vitro LPS exposure induced a 2-fold increase in NMDE secretion along with a 2-fold increase in exosomal inducible nitric oxide synthase expression and function through TLR4 and inhibitor of nuclear factor κB kinase activation. LPS stimulation increased exosomal microbiocidal activity against P aeruginosa by almost 2 orders of magnitude. LPS-stimulated exosomes induced a 4-fold increase in NO production within autologous epithelial cells with protein transfer within 5 minutes of contact. Pathway analysis of the NMDE proteome revealed 44 additional proteins associated with NO signaling and innate immune function.

CONCLUSIONS

We provide direct in vivo evidence for a novel exosome-mediated innate immunosurveillance and defense mechanism of the human upper airway. These findings have implications for lower airway innate immunity, delivery of airway therapeutics, and host microbiome regulation.