Possible role of epiregulin from dermal fibroblasts in the keratinocyte hyperproliferation of psoriasis

Vitamin C Promotes Epidermal Proliferation by Promoting DNA Demethylation of Proliferation-Related Genes in Human Epidermal Equivalents

Keratinocyte differentiation is highly regulated to produce the stratified structure of the epidermis and must be balanced with cell proliferation. Our prior studies revealed that hairless mice that cannot synthesize vitamin C (VC) exhibit epidermal atrophy. VC is a cofactor for the DNA demethylation (ten-eleven translocation) enzyme, but the role of VC in DNA demethylation during keratinocyte differentiation remains unclear. In this study, we evaluated the role of VC in epigenetic regulation of epidermal proliferation and differentiation in a human epidermal equivalent model. Our findings demonstrated that intracellular VC uptake increased epidermal thickness, cell proliferation, and global levels of 5-hydroxymethylcytosine DNA. Notably, these effects of VC were attenuated by an inhibitor of the ten-eleven translocation enzyme. DNA microarray and whole-genome bisulfite sequencing analyses revealed that 12 genes related to cell proliferation were significantly upregulated by VC. Furthermore, hypomethylated DNA regions associated with these genes were revealed in the presence of VC. Collectively, our findings provide insight into how VC increases epidermal thickness by promoting keratinocyte proliferation through the DNA demethylation of proliferation-related genes. VC is a promising molecule that can be used as developing treatment for epidermal thinning, including in aging.

Knockdown of ANXA3 regulates NF-κB/STAT3 pathway to alleviate inflammation and hyperproliferation in psoriasis models

Psoriasis is an immune-mediated inflammatory skin disorder and its pathological mechanism remains incompletely understood. Detailed exploration of this mechanism is crucial to identify key regulatory molecules influencing its progression. In previous studies, Annexin A3 (ANXA3), a calcium-dependent phospholipid-binding protein from the annexin family, has been linked to psoriasis progression. However, its specific effects on the disease remain unclear. This study aimed to investigate the role of ANXA3 in psoriasis progression. For this purpose, we employed an imiquimod (IMQ)-induced mouse model and in-vitro experiments to uncover the underlying cellular mechanisms. A mixture of five inflammatory factors (TNF-α, IL-1α, IL-17A, IL-22, and statin M) was used to stimulate HaCaT cells, mimicking the psoriasis microenvironment. Our findings demonstrate that ANXA3 is highly expressed in psoriatic skin, and its knockdown alleviates skin lesions in IMQ-induced mice. Further analysis revealed that ANXA3 knockdown reduces skin tissue hyperplasia and decreases the expression of inflammatory factors in IMQ mice. Mechanistically, ANXA3 knockdown inhibits the NF-κB/STAT3 pathway in skin tissue. Additionally, ANXA3 knockdown inhibits inflammation and hyperproliferation in HaCaT cells. Collectively, these results indicate that ANXA3 alleviates psoriasis progression both in-vivo and in-vitro by inhibiting the NF-κB/STAT3 pathway.

dEREGulated pathways: unraveling the role of epiregulin in skin, kidney, and lung fibrosis

The epidermal growth factor receptor (EGFR) signaling pathway is an evolutionary conserved mechanism to control cell behavior during tissue development and homeostasis. Deregulation of this pathway has been associated with abnormal cell behavior, including hyperproliferation, senescence, and an inflammatory cell phenotype, thereby contributing to pathologies across a variety of organs, including the kidneys, skin, and lungs. To date, there are seven distinct EGFR ligands described. Although binding of these ligands to the receptor is cell type-specific and spatio-temporally controlled with distinct affinities and kinetics, epiregulin (EREG) stands out as a long-acting EGFR ligand that emerges under pathological conditions, particularly in tissue fibrosis. Although EREG has been extensively studied in cancer, its contribution to the maladaptive remodeling of tissue is elusive. The aim of this review is to highlight the role of EREG in skin, kidney, and lung fibrosis and to discuss opportunities for therapeutic intervention.

Fibroblast: A Novel Target for Autoimmune and Inflammatory Skin Diseases Therapeutics

Fibroblasts are crucial components of the skin structure. They were traditionally believed to maintain the skin's structure by producing extracellular matrix and other elements. Recent research illuminated that fibroblasts can respond to external stimuli and exhibit diverse functions, such as the secretion of pro-inflammatory factors, adipogenesis, and antigen presentation, exhibiting remarkable heterogeneity and plasticity. This revelation positions fibroblasts as active contributors to the pathogenesis of skin diseases, challenging the traditional perspective that views fibroblasts solely as structural entities. Based on their diverse functions, fibroblasts can be categorized into six subtypes: pro-inflammatory fibroblasts, myofibroblasts, adipogenic fibroblasts, angiogenic fibroblasts, mesenchymal fibroblasts, and antigen-presenting fibroblasts. Cytokines, metabolism, and epigenetics regulate functional abnormalities in fibroblasts. The dynamic changes fibroblasts exhibit in different diseases and disease states warrant a comprehensive discussion. We focus on dermal fibroblasts' aberrant manifestations and pivotal roles in inflammatory and autoimmune skin diseases, including psoriasis, vitiligo, lupus erythematosus, scleroderma, and atopic dermatitis, and propose targeting aberrantly activated fibroblasts as a potential therapeutic strategy for inflammatory and autoimmune skin diseases.

Single-cell epigenomic dysregulation of Systemic Sclerosis fibroblasts via CREB1/EGR1 axis in self-assembled human skin equivalents

Systemic sclerosis (SSc) is an autoimmune disease characterized by skin fibrosis, internal organ involvement and vascular dropout. We previously developed and phenotypically characterized an in vitro 3D skin-like tissue model of SSc, and now analyze the transcriptomic (scRNA-seq) and epigenetic (scATAC-seq) characteristics of this model at single-cell resolution. SSc 3D skin-like tissues were fabricated using autologous fibroblasts, macrophages, and plasma from SSc patients or healthy control (HC) donors. SSc tissues displayed increased dermal thickness and contractility, as well as increased α-SMA staining. Single-cell transcriptomic and epigenomic analyses identified keratinocytes, macrophages, and five populations of fibroblasts (labeled FB1 - 5). Notably, FB1 APOE-expressing fibroblasts were 12-fold enriched in SSc tissues and were characterized by high EGR1 motif accessibility. Pseudotime analysis suggests that FB1 fibroblasts differentiate from a TGF-β1-responsive fibroblast population and ligand-receptor analysis indicates that the FB1 fibroblasts are active in macrophage crosstalk via soluble ligands including FGF2 and APP. These findings provide characterization of the 3D skin-like model at single cell resolution and establish that it recapitulates subsets of fibroblasts and macrophage phenotypes observed in skin biopsies.

Generating detailed intercellular communication patterns in psoriasis at the single-cell level using social networking, pattern recognition, and manifold learning methods to optimize treatment strategies

Psoriasis, a complex and recurrent chronic inflammatory skin disease involving various inflammatory cell types, requires effective cell communication to maintain the homeostatic balance of inflammation. However, patterns of communication at the single-cell level have not been systematically investigated. In this study, we employed social network analysis tools, pattern recognition, and manifold learning to compare molecular communication features between psoriasis cells and normal skin cells. Utilizing a process that facilitates the discovery of cell type-specific regulons, we analyzed internal regulatory networks among different cells in psoriasis. Advanced techniques for the quantitative detection of non-targeted proteins in pathological tissue sections were employed to demonstrate protein expression. Our findings revealed a synergistic interplay among the communication signals of immune cells in psoriasis. B-cells were activated, while Langerhans cells shifted into the primary signaling output mode to fulfill antigen presentation, mediating T-cell immunity. In contrast to normal skin cells, psoriasis cells shut down numerous signaling pathways, influencing the balance of skin cell renewal and differentiation. Additionally, we identified a significant number of active cell type-specific regulons of resident immune cells around the hair follicle. This study unveiled the molecular communication features of the hair follicle cell-psoriasis axis, showcasing its potential for therapeutic targeting at the single-cell level. By elucidating the pattern of immune cell communication in psoriasis and identifying new molecular features of the hair follicle cell-psoriasis axis, our findings present innovative strategies for drug targeting to enhance psoriasis treatment.

Exploring the role of growth factors as potential regulators in psoriatic plaque formation

Psoriasis is a chronic inflammatory skin disease in which growth activity is more prominent than inflammatory activity at the centre of lesional skin (CE skin). This growth activity is partly influenced by growth factors (GFs) that play an important role in cell growth and inflammation during the plaque development. In this study, we identified potential GFs in CE skin and predicted their regulatory functions and biological activity in mediating transcripts in the plaques. Samples of uninvolved skin (UN skin) and CE skin were biopsied from patients with psoriasis vulgaris for RNA-sequencing analysis in order to identify differentially expressed genes (DEGs). Our finding revealed that epidermal growth factor (EGF), fibroblast growth factor (FGF), platelet-derived growth factor (PDGF) and hepatocyte growth factor (HGF) signalling were enriched by CE/UN skin-derived DEGs. Additionally, several EGFR ligands, namely EGF, heparin-binding EGF like growth factor (HB-EGF), amphiregulin (AREG) and transforming growth factor (TGF)-α, as well as TGF-β1, TGF-β2, vascular endothelial growth factor-A, FGFs, PDGF-B and HGF, were predicted to be GF regulators. The regulatory pattern and biological activity of these GF regulators on mediating the CE/UN skin-derived DEGs was demonstrated. This study provides a novel hypothesis regarding the overall regulatory function of GFs, which appear to modulate the expression of the transcripts involved in inflammation and growth in the CE skin. In addition, some GFs may exert anti-inflammatory effects. Further investigations on the mechanisms underlying this regulation may contribute to a deeper understanding of psoriasis and the identification of potential therapeutic targets for patients with psoriasis.

Skin Barrier Dysregulation in Psoriasis

The skin barrier is broadly composed of two elements-a physical barrier mostly localised in the epidermis, and an immune barrier localised in both the dermis and epidermis. These two systems interact cooperatively to maintain skin homeostasis and overall human health. However, if dysregulated, several skin diseases may arise. Psoriasis is one of the most prevalent skin diseases associated with disrupted barrier function. It is characterised by the formation of psoriatic lesions, the aberrant differentiation and proliferation of keratinocytes, and excessive inflammation. In this review, we summarize recent discoveries in disease pathogenesis, including the contribution of keratinocytes, immune cells, genetic and environmental factors, and how they advance current and future treatments.