Dynamic interplay between IL-1 and WNT pathways in regulating dermal adipocyte lineage cells during skin development and wound regeneration

C3H10T1/2 Mesenchymal Stem Cell Line as a New In Vitro Tool for Studying Adipocyte Dedifferentiation

Dedifferentiated fat (DFAT) cells are adipocyte-derived cells that are able to differentiate into multiple cell lineages such as adipocytes, osteoblasts and chondrocytes, similar to mesenchymal stem cells (MSCs). Despite their great potential for developing novel clinical interventions by using their multipotency, the detailed mechanisms of how adipocytes undergo dedifferentiation into DFAT cells are not completely understood, because useful in vitro tools for studying adipocyte dedifferentiation are missing. In this study, we show that mature adipocytes derived from the MSC cell line C3H10T1/2 underwent dedifferentiation into cells with DFAT cell-like characteristics, when they were cultured in an inverted flask. During the dedifferentiation, expression levels of genes and protein specific to adipocytes were continuously decreased, whereas those for MSC, proliferation and WNT/β-catenin signaling were gradually increased. These DFAT-like cells also underwent differentiation into adipocytes, osteoblasts and chondrocytes with their specific cell morphology and gene expression. We also observed that an individually cultured single adipocyte also underwent dedifferentiation into DFAT-like cells that were able to differentiate into the multiple cell lineages. Our results indicate that C3H10T1/2 cells could be a great tool for determining molecular biological and biochemical mechanisms underlying adipocyte dedifferentiation.

Exercise-induced anti-obesity effects in male mice generated by a FOXO1-KLF10 reinforcing loop promoting adipose lipolysis

Exercise combats obesity and metabolic disorders, but the underlying mechanism is incompletely understood. KLF10, a transcription factor involved in various biological processes, has an undefined role in adipose tissue and obesity. Here, we show that exercise facilitates adipocyte-derived KLF10 expression via SIRT1/FOXO1 pathway. Adipocyte-specific knockout of KLF10 blunts exercise-promoted white adipose browning, energy expenditure, fat loss, glucose tolerance in diet-induced obese male mice. Conversely, adipocyte-specific transgenic expression of KLF10 in male mice enhanced the above metabolic profits induced by exercise. Mechanistically, KLF10 interacts with FOXO1 and facilitates the recruitment of KDM4A to form a ternary complex on the promoter regions of Pnpla2 and Lipe genes to promote these key lipolytic genes expression by demethylating H3K9me3 on their promoters, which facilitates lipolysis to defend against obesity in male mice. As a downstream effector responding to exercise, adipose KLF10 could act as a potential target in the fight against obesity.

Exploration of Conserved Human Adipose Subpopulations Using Targeted Single-Nuclei RNA Sequencing Data Sets

BACKGROUND

Smooth-muscle cells and pericytes are mural cells. Pericytes can differentiate into myofibroblasts, chondrocytes, vascular smooth-muscle cells, and adipocytes, marking them as a distinct progenitor population. Our goal was to molecularly define the progenitor cell populations in human adipose tissues and test the adipogenic potential of human mural cells.

METHODS

We used informatic analysis of single-cell RNA sequencing data from human tissues to identify and define pericytes and adipose progenitor cells found in human adipose tissues, including perivascular, brown, and white adipose tissues.

RESULTS

We established tissue-specific patterns of gene expression in pericytes and other putative human adipocyte progenitor cells. PPARG-expressing pericytes were present in multiple human adipose depots with consistent expression of COL25A1, MYO1B, and POSTN. We also found evidence of tissue-specific pericyte markers. Although there is some conservation between human and mouse adipose tissues, human pericyte populations have unique, depot-specific gene expression signatures. Immunofluorescence staining of human adipose tissue revealed the presence of pericytes both distant from and adjacent to vasculature in human adipose tissue. Additionally, we demonstrated the potential of human brain pericytes and aortic vascular smooth-muscle cells to differentiate into adipocytes in vitro on the basis of intracellular lipid accumulation and expression of adipocyte markers.

CONCLUSIONS

Human adipose cell populations are distinct from mice, and the pericyte subpopulation in human adipose tissues are present across adipose depots. Given that vascular mural cells, including pericytes and smooth-muscle cells, can undergo adipogenesis, we postulate that they are a novel source of adipocytes in the vascular microenvironment.

Dedifferentiated fat cells-derived exosomes (DFATs-Exos) loaded in GelMA accelerated diabetic wound healing through Wnt/β-catenin pathway

BACKGROUND

Diabetic foot ulcers pose significant challenges for clinicians worldwide. Cell-free exosome therapy holds great potential for wound healing. Dedifferentiated fat cells (DFATs) have been used in tissue engineering and regeneration, but there are no reports on the use of DFATs-derived exosomes in diabetic wound repair.

OBJECTIVES

This study aims to investigate whether DFATs-Exos accelerated diabetic wound healing and explore its potential mechanism.

METHODS

In vitro, DFATs-Exos were harvested from adipose tissue and used to treat endothelial cells (ECs) and fibroblasts. XAV939 was used as a Wnt/β-catenin pathway inhibitor. The biocompatibility of gelatin methacryloyl (GelMA) hydrogel was assessed. In vivo, DFAT-derived exosomes were encapsulated in 10% GelMA hydrogel and applied to a diabetic wound model. Histological analysis and wound closure rates were evaluated.

RESULTS

DFATs-Exos promoted angiogenesis in ECs and significantly alleviated the high glucose-induced inhibition of cell proliferation and migration by activating the Wnt/β-catenin pathway. In vivo, compared to DFAT-Exos or GelMA alone, the DFAT-Exos/GelMA combination accelerated wound closure and enhanced collagen maturity.

CONCLUSION

The DFAT-Exos/GelMA hydrogel significantly promoted wound healing in a diabetic animal model through activation of the Wnt/β-catenin signaling pathway.

Antigen-presenting fibroblasts: emerging players in immune modulation and therapeutic targets

Antigen-presenting fibroblasts are a newly recognized subset that challenges the traditional view of these cells as mere structural components. Under pathological or environmental stimuli, fibroblasts acquire antigen-presenting capabilities through the expression of MHC-II molecules and co-stimulatory factors, enabling them to interact with T cells and modulate immune responses. These specialized fibroblasts have been identified across various tissues and diseases, where they play context-dependent roles, either amplifying immune dysregulation or contributing to immune homeostasis. This review synthesizes recent advances in understanding the origins, activation, and functions of antigen-presenting fibroblasts. It highlights their role in promoting pathogenic immune responses and offering therapeutic opportunities through targeted modulation. Advancing our understanding of antigen-presenting fibroblasts holds great promise for developing innovative approaches to immune modulation and therapy across a range of diseases.

TGFβ-mediated inhibition of hypodermal adipocyte progenitor differentiation promotes wound-induced skin fibrosis

Aberrant activation of dermal fibroblasts during wound healing often leads to debilitating fibrotic changes in the skin, such as scleroderma and keloids. However, the underlying cellular and molecular mechanisms remain elusive. Here, we established a wound-induced skin fibrosis (WISF) mouse model in mature adult mice, characterised by excessive deposition of collagen bundles, loss of dermal adipocytes, and enrichment of DPP4+Ly6A+THY1+ hypodermal interstitial adipocyte progenitors (HI-APs) and pericytes, resembling human fibrotic skin diseases. This WISF model exhibited an age-dependent gain of fibrotic characteristics, contrasting with the wound-induced hair neogenesis observed in younger mice. Through comprehensive analyses of the WISF, we delineated a trajectory of fibroblast differentiation that originates from HI-APs. These progenitors highly expressed several extracellular matrix (ECM) genes and exhibited a TGFβ pathway signature. TGFβ was identified as the key signal to inhibit the adipogenic potential and maintain the fibrogenic potential of dermal APs. Additionally, administering a TGFβ receptor inhibitor to wound scar reduced the abundance of ECM-producing APs. Finally, analysis of human scleroderma skin tissues revealed a negative correlation between the expression of AP-, ECM-, and TGFβ pathway-related genes and PPARG. Overall, this study establishes a wound-induced skin fibrosis mouse model and demonstrates that TGFβ-mediated blockage of HI-AP differentiation is crucial for driving fibrotic pathology. Targeting HI-APs and adipogenesis may provide novel avenues for developing disease-modifying therapies for fibrotic skin diseases.

Exercise-regulated lipolysis: Its role and mechanism in health and diseases

Exercise has received considerable attention because of its importance not just in regulating physiological function, but also in ameliorating multiple pathological processes. Among these processes, lipolysis may play an important role in exercise-induced benefits. It is generally accepted that active lipolysis contributes to breakdown of fats, leading to the release of free fatty acids (FFAs) that serve as an energy source for muscles and other tissues during exercise. However, the significance of lipolysis in the context of exercise has not been fully understood. This review comprehensively outlines the potential regulatory mechanisms by which exercise stimulates lipolysis. The potential roles of exercise-mediated lipolysis in various physiological and pathological processes are also summarized. Additionally, we also discussed the potential non-classical effects of key lipolytic effectors induced by exercise. This will enhance our understanding of how exercise improves lipolytic function to bring about beneficial effects, offering new insights into potential therapeutic avenues for promoting health and alleviating diseases.

Fibroblast-Mediated Macrophage Recruitment Supports Acute Wound Healing

Epithelial and immune cells have long been appreciated for their contribution to the early immune response after injury; however, much less is known about the role of mesenchymal cells. Using single-nuclei RNA sequencing, we defined changes in gene expression associated with inflammation 1 day after wounding in mouse skin. Compared with those in keratinocytes and myeloid cells, we detected enriched expression of proinflammatory genes in fibroblasts associated with deeper layers of the skin. In particular, SCA1+ fibroblasts were enriched for numerous chemokines, including CCL2, CCL7, and IL-33, compared with SCA1- fibroblasts. Genetic deletion of Ccl2 in fibroblasts resulted in fewer wound-bed macrophages and monocytes during injury-induced inflammation, with reduced revascularization and re-epithelialization during the proliferation phase of healing. These findings highlight the important contribution of fibroblast-derived factors to injury-induced inflammation and the impact of immune cell dysregulation on subsequent tissue repair.

The Central Roles of Keratinocytes in Coordinating Skin Immunity

The function of keratinocytes (KCs) to form a barrier and produce cytokines is well-known, but recent progress has revealed many different roles for KCs in regulation of skin immunity. In this review, we provide an update on the current understanding of how KCs communicate with microbes, immunocytes, neurons, and other cells to form an effective immune barrier. We catalog the large list of genes and metabolites of KCs that participate in host defense and discuss the mechanisms of immune crosstalk, addressing how KCs simultaneously form a physical barrier, communicate with fibroblasts, and control immune signals. Overall, the signals sent and received by KCs are an exciting group of therapeutic targets to explore in the treatment of dermatologic disorders.

Suture-anchored cutaneous tension induces persistent hypertrophic scarring in a novel murine model

Background

Hypertrophic scars cause impaired skin appearance and function, seriously affecting physical and mental health. Due to medical ethics and clinical accessibility, the collection of human scar specimens is frequently restricted, and the establishment of scar experimental animal models for scientific research is urgently needed. The four most commonly used animal models of hypertrophic scars have the following drawbacks: the rabbit ear model takes a long time to construct; the immunodeficient mouse hypertrophic scar model necessitates careful feeding and experimental operations; female Duroc pigs are expensive to purchase and maintain, and their large size makes it difficult to produce a significant number of models; and mouse scar models that rely on tension require special skin stretch devices, which are often damaged and shed, resulting in unstable model establishment. Our group overcame the shortcomings of previous scar animal models and created a new mouse model of hypertrophic scarring induced by suture anchoring at the wound edge.

Methods

We utilized suture anchoring of incisional wounds to impose directional tension throughout the healing process, restrain wound contraction, and generate granulation tissue, thus inducing scar formation. Dorsal paired incisions were generated in mice, with wound edges on the upper back sutured to the rib cage and the wound edges on the lower back relaxed as a control. Macroscopic manifestation, microscopic histological analysis, mRNA sequencing, bioinformatics, and in vitro cell assays were also conducted to verify the reliability of this method.

Results

Compared with those in relaxed controls, the fibrotic changes in stretched wounds were more profound. Histologically, the stretched scars were hypercellular, hypervascular, and hyperproliferative with disorganized extracellular matrix deposition, and displayed molecular hallmarks of hypertrophic fibrosis. In addition, the stretched scars exhibited transcriptional overlap with mechanically stretched scars, and human hypertrophic and keloid scars. Phosphatidylinositol 3-kinase-serine/threonine-protein kinase B signaling was implicated as a profibrotic mediator of apoptosis resistance under suture-induced tension.

Conclusions

This straightforward murine model successfully induces cardinal molecular and histological features of pathological hypertrophic scarring through localized suture tension to inhibit wound contraction. The model enables us to interrogate the mechanisms of tension-induced fibrosis and evaluate anti-scarring therapies.

Dermal white adipose tissue: Development and impact on hair follicles, skin defense, and fibrosis

Dermal white adipose tissue (DWAT) is a distinctive adipose depot located within the lower dermis of the skin. Its significance as an ancillary fat in skin homoeostasis has recently received increased attention. New research has revealed that DWAT responses to skin pathology and physiology changes, impacting skin development, hair cycling, defense mechanisms, and fibrotic conditions. In this review, we explore the developmental process of DWAT and the adipose commitment timing of hypodermal. We explore the development process of DWAT and its pivotal role in regulating the hair cycle. We conclude the antibacterial activity and reversible dedifferentiation of dermal adipocytes in response to skin defense. Furthermore, we underscore the potentially crucial yet underestimated anti-fibrotic functions of DWAT-derived adipokines and adipocyte-myofibroblast transition.

IL-1β promotes adipogenesis by directly targeting adipocyte precursors

Postprandial IL-1β surges are predominant in the white adipose tissue (WAT), but its consequences are unknown. Here, we investigate the role of IL-1β in WAT energy storage and show that adipocyte-specific deletion of IL-1 receptor 1 (IL1R1) has no metabolic consequences, whereas ubiquitous lack of IL1R1 reduces body weight, WAT mass, and adipocyte formation in mice. Among all major WAT-resident cell types, progenitors express the highest IL1R1 levels. In vitro, IL-1β potently promotes adipogenesis in murine and human adipose-derived stem cells. This effect is exclusive to early-differentiation-stage cells, in which the adipogenic transcription factors C/EBPδ and C/EBPβ are rapidly upregulated by IL-1β and enriched near important adipogenic genes. The pro-adipogenic, but not pro-inflammatory effect of IL-1β is potentiated by acute treatment and blocked by chronic exposure. Thus, we propose that transient postprandial IL-1β surges regulate WAT remodeling by promoting adipogenesis, whereas chronically elevated IL-1β levels in obesity blunts this physiological function.

Defining cell type-specific immune responses in a mouse model of allergic contact dermatitis by single-cell transcriptomics

Allergic contact dermatitis (ACD), a prevalent inflammatory skin disease, is elicited upon repeated skin contact with protein-reactive chemicals through a complex and poorly characterized cellular network between immune cells and skin resident cells. Here, single-cell transcriptomic analysis of the murine hapten-elicited model of ACD reveals that upon elicitation of ACD, infiltrated CD4+ or CD8+ lymphocytes were primarily the IFNγ-producing type 1 central memory phenotype. In contrast, type 2 cytokines (IL4 and IL13) were dominantly expressed by basophils, IL17A was primarily expressed by δγ T cells, and IL1β was identified as the primary cytokine expressed by activated neutrophils/monocytes and macrophages. Furthermore, analysis of skin resident cells identified a sub-cluster of dermal fibroblasts with preadipocyte signature as a prominent target for IFNγ+ lymphocytes and dermal source for key T cell chemokines CXCL9/10. IFNγ treatment shifted dermal fibroblasts from collagen-producing to CXCL9/10-producing, which promoted T cell polarization toward the type-1 phenotype through a CXCR3-dependent mechanism. Furthermore, targeted deletion of Ifngr1 in dermal fibroblasts in mice reduced Cxcl9/10 expression, dermal infiltration of CD8+ T cell, and alleviated ACD inflammation in mice. Finally, we showed that IFNγ+ CD8+ T cells and CXCL10-producing dermal fibroblasts co-enriched in the dermis of human ACD skin. Together, our results define the cell type-specific immune responses in ACD, and recognize an indispensable role of dermal fibroblasts in shaping the development of type-1 skin inflammation through the IFNGR-CXCR3 signaling circuit during ACD pathogenesis.

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.

Advancements in Regenerative Medicine for Aesthetic Dermatology: A Comprehensive Review and Future Trends

The growing interest in maintaining a youthful appearance has encouraged an accelerated development of innovative, minimally invasive aesthetic treatments for facial rejuvenation and regeneration. The close correlation between tissue repair, regeneration, and aging has paved the way for the application of regenerative medicine principles in cosmetic dermatology. The theoretical substrates of regenerative medicine applications in dermo-aesthetics are plentiful. However, regenerative dermatology is an emerging field and needs more data and in vivo trials to reach a consensus on the standardization of methods. In this review, we summarize the principles of regenerative medicine and techniques as they apply to cosmetic dermatology, suggesting unexplored fields and future directions.

Tissue fibrosis associated depletion of lipid-filled cells

Fibrosis is primarily described as the deposition of excessive extracellular matrix, but in many tissues it also involves a loss of lipid or lipid-filled cells. Lipid-filled cells are critical to tissue function and integrity in many tissues including the skin and lungs. Thus, loss or depletion of lipid-filled cells during fibrogenesis, has implications for tissue function. In some contexts, lipid-filled cells can impact ECM composition and stability, highlighting their importance in fibrotic transformation. Recent papers in fibrosis address this newly recognized fibrotic lipodystrophy phenomenon. Even in disparate tissues, common mechanisms are emerging to explain fibrotic lipodystrophy. These findings have implications for fibrosis in tissues composed of fibroblast and lipid-filled cell populations such as skin, lung, and liver. In this review, we will discuss the roles of lipid-containing cells, their reduction/loss during fibrotic transformation, and the mechanisms of that loss in the skin and lungs.