Animal model of sclerotic skin. I: Local injections of bleomycin induce sclerotic skin mimicking scleroderma

Enhancement of Ndrg2 promotes hypertrophic scar fibrosis by regulating PI3K/AKT signaling pathway

Hypertrophic scar (HTS) is a prevalent chronic inflammatory skin disorder characterized by abnormal proliferation and extracellular matrix deposition. N-Myc downstream regulated gene 2 (Ndrg2) is a cell stress response gene related to cell proliferation, differentiation and various fibrotic diseases. However, the role of Ndrg2 in HTS is unknown and warrants further investigation. In this study, we confirmed that the expression of Ndrg2 was increased in HTS of human and a bleomycin-induced fibrosis mouse model. We then used Ndrg2 knockout mice and found Ndrg2 deletion could significantly reduce the synthesis of collagen and alleviate skin fibrosis. In addition, the proliferation and migration of Ndrg2-interfered HTS-derived fibroblasts decreased and those of Ndrg2-overexpressed normal skin-derived fibroblasts increased. Further, by western blot analysis, we verified that the expression of phosphorylated-PI3K, PI3K, phosphorylated-AKT and AKT were all increased after Ndrg2 overexpressed in normal skin-derived fibroblasts. Moreover, PI3K inhibitor (LY294002) administration significantly rescued the effect of Ndrg2 overexpression on skin fibrosis. In summary, our results demonstrated that Ndrg2 could promote HTS fibrosis by mediating PI3K/AKT signaling pathway. Our data suggest that Ndrg2 may be a promising therapeutic target for HTS.

miR-143-3p boosts extracellular vesicles to improve the dermal fibrosis of localized scleroderma

Localized scleroderma (LoSc) is an autoimmune disease that features extensive fibrosis of the skin. Due to its severity and limited understanding, no effective treatments have been developed to date. Bone marrow mesenchymal stem cells (BMSCs) derived extracellular vesicles (EVs) have been demonstrated promising therapeutic effects on the LoSc mouse model in our previous study. However, identifying the targets and underlying mechanisms of EVs remains a significant challenge for therapeutic applications. miR-143-3p, a critical and abundant factor in BMSC-EVs identified through miRNA sequencing, mediates antifibrotic effects in a LoSc mouse model and is significantly lacking in the dermis of LoSc patients. This microRNA inhibits myofibroblast formation and collagen synthesis, contributing to the therapeutic effects of BMSC-EVs in the LoSc mouse model. Moreover, miR-143-3p-reinforced BMSC-EVs demonstrated enhanced therapeutic efficacy compared to normal BMSC-EVs, reducing dermal thickening, collagen deposition, fibroblast differentiation into myofibroblasts, and promoting skin tissue remodeling. IGF1R, highly expressed in the skin of LoSc, was identified as a potential target of miR-143-3p and was inhibited by miR-143-3p-reinforced EVs, thereby modulating the IGF1/IGF1R-AKT/MAPK pathway. In conclusion, miR-143-3p-enriched EVs could be a more efficient candidate for treating dermal fibrosis in LoSc.

Comparative Evaluation of Bleomycin- and Collagen-V-Induced Models of Systemic Sclerosis: Insights into Fibrosis and Autoimmunity for Translational Research

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by fibrosis, immune dysregulation, and vascular dysfunction, yet its pathogenesis remains incompletely understood. This study compares two widely used animal models of SSc-the bleomycin-induced fibrosis model and the collagen-V-induced autoimmune model-to evaluate their ability to replicate key disease features. In the bleomycin model, consistent cardiac fibrosis was observed across treatment groups despite variability in fibrosis in the skin and lungs, suggesting organ-specific differences in susceptibility. The collagen-V model demonstrated robust autoantibody production against collagen-V, confirming its utility in studying immune activation, though fibrosis was largely confined to the heart. While the bleomycin model excels at mimicking rapid fibrosis and is suitable for testing antifibrotic therapies, the collagen-V model provides insights into antigen-specific autoimmunity. Both models highlight the dynamic nature of fibrosis, where ECM deposition and degradation occur concurrently, complicating its use as a quantitative disease marker. Cardiac fibrosis emerged as a consistent feature in both models, emphasizing its relevance in SSc pathophysiology. Combining these models or refining their design through hybrid approaches, extended timelines, or sex and age adjustments could enhance their translational utility. These findings advance understanding of SSc mechanisms and inform therapeutic development for this challenging disease.

Pulmonary and systemic effects of inhaled crystalline silica in the HOCl-induced mouse model of systemic sclerosis: An experimental model of Erasmus syndrome

Occupational exposure to crystalline silica is etiologically linked to an increased incidence of systemic sclerosis (SSc), also called Erasmus syndrome. The underlying mechanisms of silica-related SSc are still poorly understood. We demonstrated that early and repeated silica exposure contribute to the severity of SSc symptoms in the hypochloric acid (HOCl)-induced SSc mouse model. Analyses of lung samples from silica-exposed HOCl mice revealed a slightly aggravation of fibrosis and an exacerbation of inflammation, notably an additionally overexpression of NLRP3 inflammasome genes and a recruitment of classical monocytes, macrophages, dendritic cells and neutrophils. Silica exposure showed systemic effects in SSc mouse model with an elevated circulating classical monocyte counts and an overexpression of inflammatory genes in the skin. Silica-exposed SSc patients also had more severe skin disease than unexposed patients. Overall, we provide new insights on immune cell populations and related pathways in early pathogenic mechanisms contributing to HOCl-induced and silica-related SSc.

A GPVI-platelet-neutrophil-NET axis drives systemic sclerosis

Systemic sclerosis (SSc) is characterized by progressive fibrosis of skin, lung, and other organs and retains among the highest rates of mortality among autoimmune diseases. We identified activation of circulating neutrophils from patients with diffuse SSc, together with concordant transcriptomic evidence of neutrophil activation in blood, skin, and lungs, and in mice with experimental SSc of skin and lung induced by hypochlorous acid or bleomycin. Neutrophil depletion abrogated experimental SSc, while adoptive transfer of SSc neutrophils induced skin and lung fibrosis in healthy mice, identifying neutrophils as both necessary and sufficient for disease. In patients, platelet activation accompanied diffuse SSc, and in mice platelet activation preceded neutrophil activation, suggesting an upstream role. Platelet depletion abrogated both neutrophil activation and tissue fibrosis. SSc platelets conferred upon neutrophils the capacity to induce SSc. This capacity corresponded to enhanced production of neutrophil extracellular traps (NETs); experimental SSc was abrogated in NET-deficient PAD4 -/- mice, a resistance bypassed by adoptive transfer of PAD4-suficient SSc neutrophils, confirming NETs as a key effector mechanism of SSc. In turn, platelet activation was mediated via the platelet collagen receptor GPVI, while GPVI deficiency resulted in attenuated platelet and neutrophil activation, fewer circulating NETs, and protection from fibrosis in both murine models of SSc. Together, these findings define a GPVI-platelet-neutrophil-NET axis in SSc and identify a new set of therapeutic targets in this often-refractory condition.

Inhibition of skin fibrosis via regulation of Th17/Treg imbalance in systemic sclerosis

Systemic sclerosis (SSc) is an idiopathic systemic connective tissue disorder characterized by fibrosis of the skin and internal organs, with growing interest in the imbalance between Th17 cells and regulatory T cells (Tregs) in the disease's pathogenesis. Heligmosomoides polygyrus (Hp), a natural intestinal parasite of mice, is known to induce Tregs in the host. We aimed to investigate the effects of Hp-induced Tregs on bleomycin-induced dermal fibrosis and clarify the role of the Th17/Treg balance in SSc fibrosis. Infection with Hp suppressed the development of bleomycin-induced dermal fibrosis and the infiltration of CD3+ T cells and CD68+ macrophages. Flow cytometric analysis revealed that Hp infection increased Tregs and inhibited the induction of bleomycin-induced Th17 cells. Treg depletion nullified these effects, suggesting that Hp-induced Tregs may prevent bleomycin-induced dermal fibrosis and inflammation. Analysis of the intestinal microbiota showed that bacteria positively correlated with Tregs exhibited a negative correlation with Th17 cells and dermal fibrosis in mice. SSc patients with severe fibrosis displayed a distinct microbiota profile. These results suggest that alterations in the intestinal microbiota may contribute to the Th17/Treg imbalance in SSc and its progression. Enhancing Tregs to regulate the Th17/Treg imbalance may present a promising strategy for suppressing fibrosis in SSc.

New insights into the structural role of EMILINs within the human skin microenvironment

Supramolecular extracellular matrix (ECM) networks play an essential role in skin architecture and function. Elastin microfibril interface-located proteins (EMILINs) comprise a family of three extracellular glycoproteins that serve as essential structural components of the elastin/fibrillin microfibril network, and exert crucial functions in cellular signaling. Little is known about the structural nature of EMILIN networks in skin. We therefore investigated the spatiotemporal localization of EMILIN-1, -2, -3 in human skin induced by aging, UV-exposure, fibrosis, and connective tissue disorder. Confocal immunofluorescence and immunogold electron microscopy analysis identified all EMILINs as components of elastic fibers and elastin-free oxytalan fibers inserted into the basement membrane (BM). Further, our ultrastructural analysis demonstrates cellular contacts of dermally localized EMILIN-1 positive fibers across the BM with the surface of basal keratinocytes. Analysis of skin biopsies and fibroblast cultures from fibrillin-1 deficient Marfan patients revealed that EMILINs require intact fibrillin-1 as deposition scaffold. In patients with scleroderma and the bleomycin-induced murine fibrosis model EMILIN-2 was upregulated. EMILIN-3 localizes to the tips of candelabra-like oxytalan fibers, and to specialized BMs engulfing hair follicles and sebaceous glands. Our data identify EMILINs as important markers to monitor rearrangements of the dermal ECM architecture induced by aging and pathological conditions.

Pathogenic role of anti-nuclear autoantibodies in systemic sclerosis: Insights from other rheumatic diseases

Systemic sclerosis (SSc) is a severe autoimmune disease characterized by vasculopathy, fibrosis, and dysregulated immunity, with hallmark autoantibodies targeting nuclear antigens such as centromere protein (ACA) and topoisomerase I (ATA). These autoantibodies are highly prevalent and disease-specific, rarely coexisting, thus serving as crucial biomarkers for SSc diagnosis. Despite their diagnostic value, their roles in SSc pathogenesis remain unclear. This review summarizes current literature on ACA and ATA in SSc, comparing them to autoantibodies in other rheumatic diseases to elucidate their potential pathogenic roles. Similarities are drawn with anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis, particularly regarding disease specificity and minimal pathogenic impact of antigen binding. In addition, differences between ANA and ACPA in therapeutic responses and Fab glycosylation patterns are reviewed. While ACA and ATA are valuable for disease stratification and monitoring activity, understanding their origins and the associated B cell responses is critical for advancing therapeutic strategies for SSc.

SPARC activates p38γ signaling to promote PFKFB3 protein stabilization and contributes to keloid fibroblast glycolysis

BACKGROUND

Keloids are currently challenging to treat because they recur after resection which may affect patients' quality of life. At present, no universal consensus on treatment regimen has been established. Thus, finding new molecular mechanisms underlying keloid formation is imminent. This study aimed to explore the function of secreted protein acidic and cysteine rich (SPARC) on keloids and its behind exact mechanisms.

METHODS

The expression of SPARC, p38γ, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), α-SMA, and Ki67 in patients with keloid and bleomycin (BLM)-induced fibrosis mice was assessed utilizing western blot, qRT-PCR, and immunohistochemical staining. After transfected with pcDNA-SPARC, si-SPARC-1#, si-SPARC-2#, and si-p38γ, and treated with glycolytic inhibitor (2-DG) or p38 inhibitor (SB203580), CCK-8, EdU, transwell, and western blot were utilized for assessing the proliferation, migration, and collagen production of keloid fibroblasts (KFs).

RESULTS

SPARC, p38γ, and PFKFB3 were highly expressed in patients with keloid and BLM-induced fibrosis mice. SPARC promoted the proliferation, migration, and collagen production of KFs via inducing glycolysis. Moreover, SPARC could activate p38γ signaling to stabilize PFKFB3 protein expression in KFs. Next, we demonstrated that SPARC promoted the proliferation, migration, collagen production, and glycolysis of KFs via regulating p38γ signaling. In addition, in BLM-induced fibrosis mice, inhibition of p38γ and PFKFB3 relieved skin fibrosis.

CONCLUSIONS

Our findings indicated that SPARC could activate p38γ pathway to stabilize the expression of PFKFB3, and thus promote the glycolysis of KFs and the progression of keloid.

Unraveling the role of MiR-181 in skin fibrosis pathogenesis by targeting NUDT21

Systemic sclerosis (SSc) is a life-threatening autoimmune disease characterized by widespread fibrosis in the skin and several internal organs. Nudix Hydrolase 21 (NUDT2 or CFIm25) downregulation in fibroblasts is known to play detrimental roles in both skin and lung fibrosis. This study aims to investigate the upstream mechanisms that lead to NUDT21 repression in skin fibrosis. We identified transforming growth factor β (TGFβ1) as the primary cytokine that downregulated NUDT21 in normal skin fibroblasts. In the bleomycin-induced dermal fibrosis model, consistent with the peak activation of TGFβ1 at the late fibrotic stage, NUDT21 was downregulated at this stage, and delayed NUDT21 knockdown during this fibrotic phase led to enhanced fibrotic response to bleomycin. Further investigation suggested TGFβ downregulated NUDT21 through microRNA (miRNA) 181a and 181b induction. Both miR-181a and miR-181b were elevated in bleomycin-induced skin fibrosis in mice and primary fibroblasts isolated from SSc patients, and they directly targeted NUDT21 and led to its downregulation in skin fibroblasts. Functional studies demonstrated that miR-181a and miR-181b inhibitors attenuated bleomycin-induced skin fibrosis in mice in association with decreased NUDT21 expression, while miR-181a and miR-181b mimics promoted bleomycin-induced fibrosis. Overall, these findings suggest a novel role for miR-181a/b in SSc pathogenesis by repressing NUDT21 expression.

Deletion of adipocyte Sine Oculis Homeobox Homolog 1 prevents lipolysis and attenuates skin fibrosis

Dermal fibrosis is a cardinal feature of systemic sclerosis (SSc) for which there are limited treatment strategies. This is in part due to our fragmented understanding of how dermal white adipose tissue (DWAT) contributes to skin fibrosis. We identified elevated sine oculis homeobox homolog 1 (SIX1) expression in SSc skin samples from the GENISOS and PRESS cohorts, the expression of which correlated with adipose-associated genes and molecular pathways. SIX1 localization studies identified increased signals in the DWAT area in SSc and in experimental models of skin fibrosis. Global and adipocyte specific Six1 deletion abrogated end-stage fibrotic gene expression and dermal adipocyte shrinkage induced by SQ bleomycin treatment. Further studies revealed a link between elevated SIX1 and increased expression of SERPINE1 and its protein PAI-1 which are known pro-fibrotic mediators. However, SIX1 deletion did not appear to affect cellular trans differentiation. Taken together these results point at SIX1 as a potential target for dermal fibrosis in SSc.

Cannabinoid receptor 2 selective agonist alleviates systemic sclerosis by inhibiting Th2 differentiation through JAK/SOCS3 signaling

Systemic sclerosis (SSc) poses a significant challenge in autoimmunology, characterized by the development of debilitating fibrosis of skin and internal organs. The pivotal role of dysregulated T cells, notably the skewed polarization toward Th2 cells, has been implicated in the vascular damage and progressive fibrosis observed in SSc. In this study, we explored the underlying mechanisms by which cannabinoid receptor 2 (CB2) highly selective agonist HU-308 restores the imbalance of T cells to alleviate SSc. Using a bleomycin-induced SSc (BLM-SSc) mouse model, we demonstrated that HU-308 effectively attenuates skin and lung fibrosis by specifically activating CB2 on CD4+ T cells to inhibit the polarization of Th2 cells in BLM-SSc mice, which was validated by Cnr2-specific-deficient mice. Different from classical signaling downstream of G protein-coupled receptors (GPCRs), HU-308 facilitates the expression of SOCS3 protein and subsequently impedes the IL2/STAT5 signaling pathway during Th2 differentiation. The deficiency of SOCS3 partially mitigated the impact of HU-308. Analysis of a cohort comprising 80 SSc patients and 82 healthy controls revealed an abnormal elevation in the Th2/Th1 ratio in SSc patients. The proportion of Th2 cells showed a significant positive correlation with mRSS score and positivity of anti-Scl-70. Administration of HU-308 to PBMCs and peripheral CD4+ T cells from SSc patients led to the upregulation of SOCS3, which effectively suppressed the aberrantly activated STAT5 signaling pathway and the proportion of CD4+IL4+ T cells. In conclusion, our findings unveil a novel mechanism by which the CB2 agonist HU-308 ameliorates fibrosis in SSc by targeting and reducing Th2 responses. These insights provide a foundation for future therapeutic approaches in SSc by modulating Th2 responses.

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

Impaired LAIR-1-mediated immune control due to collagen degradation in fibrosis

Tissue repair is disturbed in fibrotic diseases like systemic sclerosis (SSc), where the deposition of large amounts of extracellular matrix components such as collagen interferes with organ function. LAIR-1 is an inhibitory collagen receptor highly expressed on tissue immune cells. We questioned whether in SSc, impaired LAIR-1-collagen interaction is contributing to the ongoing inflammation and fibrosis. We found that SSc patients do not have an intrinsic defect in LAIR-1 expression or function. Instead, fibroblasts from healthy controls and SSc patients stimulated by soluble factors that drive inflammation and fibrosis in SSc deposit disorganized collagen products in vitro, which are dysfunctional LAIR-1 ligands. This is dependent of matrix metalloproteinases and platelet-derived growth factor receptor signaling. In support of a non-redundant role of LAIR-1 in the control of fibrosis, we found that LAIR-1-deficient mice have increased skin fibrosis in response to repeated injury and in the bleomycin mouse model for SSc. Thus, LAIR-1 represents an essential control mechanism for tissue repair. In fibrotic disease, excessive collagen degradation may lead to a disturbed feedback loop. The presence of functional LAIR-1 in patients provides a therapeutic opportunity to reactivate this intrinsic negative feedback mechanism in fibrotic diseases.

An Assessment of Administration Route on MSC-sEV Therapeutic Efficacy

Mesenchymal stem/stromal cell-derived small extracellular vesicles (MSC-sEVs) are promising therapeutic agents. In this study, we investigated how the administration route of MSC-sEVs affects their therapeutic efficacy in a mouse model of bleomycin (BLM)-induced skin scleroderma (SSc). We evaluated the impact of topical (TOP), subcutaneous (SC), and intraperitoneal (IP) administration of MSC-sEVs on dermal fibrosis, collagen density, and thickness. All three routes of administration significantly reduced BLM-induced fibrosis in the skin, as determined by Masson's Trichrome staining. However, only TOP administration reduced BLM-induced dermal collagen density, with no effect on dermal thickness observed for all administration routes. Moreover, SC, but not TOP or IP administration, increased anti-inflammatory profibrotic CD163+ M2 macrophages. These findings indicate that the administration route influences the therapeutic efficacy of MSC-sEVs in alleviating dermal fibrosis, with TOP administration being the most effective, and this efficacy is not mediated by M2 macrophages. Since both TOP and SC administration target the skin, the difference in their efficacy likely stems from variations in MSC-sEV delivery in the skin. Fluorescence-labelled TOP, but not SC MSC-sEVs when applied to skin explant cultures, localized in the stratum corneum. Hence, the superior efficacy of TOP over SC MSC-sEVs could be attributed to this localization. A comparison of the proteomes of stratum corneum and MSC-sEVs revealed the presence of >100 common proteins. Most of these proteins, such as filaggrin, were known to be crucial for maintaining skin barrier function against irritants and toxins, thereby mitigating inflammation-induced fibrosis. Therefore, the superior efficacy of TOP MSC-sEVs over SC and IP MSC-sEVs against SSc is mediated by the delivery of proteins to the stratum corneum to reinforce the skin barrier.

Skin and lung fibrosis induced by bleomycin in mice: a systematic review

OBJECTIVE

Scleroderma, or systemic sclerosis (SSc), is a chronic autoimmune connective disease with an unknown etiology and poorly understood pathogenesis. The striking array of autoimmune, vascular, and fibrotic changes that develop in almost all patients makes SSc unique among connective tissue diseases. Although no animal model developed for SSc to date fully represents all features of human disease, some animal models that demonstrate features of SSc may help to better understand the pathogenesis of the disease and to develop new therapeutic options. In this review, we aimed to evaluate skin fibrosis and lung involvement in a bleomycin (BLM)-induced mouse model and to evaluate the differences between studies.

METHODS

A systematic literature review (PRISMA guideline) on PubMed and EMBASE (until May 2023, without limits) was performed. A primary literature search was conducted using the PubMed and EMBASE databases for all articles published from 1990 to May 2023. Review articles, human studies, and non-dermatological studies were excluded. Of the 38 non-duplicated studies, 20 articles were included.

RESULTS

Among inducible animal models, the BLM-induced SSc is still the most widely used. In recent years, the measurement of tissue thickness between the epidermal-dermal junction and the dermal-adipose tissue junction (dermal layer) has become more widely accepted.

CONCLUSIONS

In animal studies, it is important to simultaneously evaluate lung tissues in addition to skin fibrosis induced in mice by subcutaneous BLM application, following the 3R (replacement, reduction, and refinement) principle to avoid cruelty to animals.

Insights into the unique roles of dermal white adipose tissue (dWAT) in wound healing

Dermal white adipose tissue (dWAT) is a newly recognized layer of adipocytes within the reticular dermis of the skin. In many mammals, this layer is clearly separated by panniculus carnosus from subcutaneous adipose tissue (sWAT). While, they concentrated around the hair shaft and follicle, sebaceous gland, and arrector pili muscle, and forms a very specific cone geometry in human. Both the anatomy and the histology indicate that dWAT has distinct development and functions. Different from sWAT, the developmental origin of dWAT shares a common precursor with dermal fibroblasts during embryogenesis. Therefore, when skin injury happens and mature adipocytes in dWAT are exposed, they may undergo lipolysis and dedifferentiate into fibroblasts to participate in wound healing as embryogenetic stage. Studies using genetic strategies to selectively ablate dermal adipocytes observed delayed revascularization and re-epithelialization in wound healing. This review specifically summarizes the hypotheses of the functions of dWAT in wound healing. First, lipolysis of dermal adipocytes could contribute to wound healing by regulating inflammatory macrophage infiltration. Second, loss of dermal adipocytes occurs at the wound edge, and adipocyte-derived cells then become ECM-producing wound bed myofibroblasts during the proliferative phase of repair. Third, mature dermal adipocytes are rich resources for adipokines and cytokines and could release them in response to injury. In addition, the dedifferentiated dermal adipocytes are more sensitive to redifferentiation protocol and could undergo expansion in infected wound. We then briefly introduce the roles of dWAT in protecting the skin from environmental challenges: production of an antimicrobial peptide against infection. In the future, we believe there may be great potential for research in these areas: (1) taking advantage of the plasticity of dermal adipocytes and manipulating them in wound healing; (2) investigating the precise mechanism of dWAT expansion in infected wound healing.

The Current Status and Future Direction of Extracellular Nano-vesicles in the Alleviation of Skin Disorders

Exosomes are extracellular vesicles (EVs) that originate from endocytic membranes. The transfer of biomolecules and biological compounds such as enzymes, proteins, RNA, lipids, and cellular waste disposal through exosomes plays an essential function in cell-cell communication and regulation of pathological and physiological processes in skin disease. The skin is one of the vital organs that makes up about 8% of the total body mass. This organ consists of three layers, epidermis, dermis, and hypodermis that cover the outer surface of the body. Heterogeneity and endogeneity of exosomes is an advantage that distinguishes them from nanoparticles and liposomes and leads to their widespread usage in the remedy of dermal diseases. The biocompatible nature of these extracellular vesicles has attracted the attention of many health researchers. In this review article, we will first discuss the biogenesis of exosomes, their contents, separation methods, and the advantages and disadvantages of exosomes. Then we will highlight recent developments related to the therapeutic applications of exosomes in the treatment of common skin disorders like atopic dermatitis, alopecia, epidermolysis bullosa, keloid, melanoma, psoriasis, and systemic sclerosis.

Progress in research on mesenchymal stem cells and their extracellular vesicles for treating fibrosis in systemic sclerosis

Systemic sclerosis (SSc) refers to an autoimmune disease characterized by immune dysfunction, vascular endothelial damage, and multi-organ fibrosis. Thus far, this disease is incurable, and its high mortality rate is significantly correlated with fibrotic events. Fibrosis has been confirmed as a difficult clinical treatment area that should be urgently treated in clinical medicine. Mesenchymal stem cells (MSCs) exhibit immunomodulatory, pro-angiogenic, and anti-fibrotic functions. MSCs-derived extracellular vesicles (EVs) have aroused rising interest as a cellular component that retains the functions of MSCs while circumventing the possible adverse effects of MSCs. Moreover, EVs have great potential in treating SSc. In this study, the current research progress on MSCs and their EVs for treating fibrosis in SSc was reviewed, with an aim to provide some reference for future MSCs and their EVs in treating SSc.

Ablation of integrin-mediated cell-collagen communication alleviates fibrosis

OBJECTIVES

Activation of fibroblasts is a hallmark of fibrotic processes. Besides cytokines and growth factors, fibroblasts are regulated by the extracellular matrix environment through receptors such as integrins, which transduce biochemical and mechanical signals enabling cells to mount appropriate responses according to biological demands. The aim of this work was to investigate the in vivo role of collagen-fibroblast interactions for regulating fibroblast functions and fibrosis.

METHODS

Triple knockout (tKO) mice with a combined ablation of integrins α1β1, α2β1 and α11β1 were created to address the significance of integrin-mediated cell-collagen communication. Properties of primary dermal fibroblasts lacking collagen-binding integrins were delineated in vitro. Response of the tKO mice skin to bleomycin induced fibrotic challenge was assessed.

RESULTS

Triple integrin-deficient mice develop normally, are transiently smaller and reveal mild alterations in mechanoresilience of the skin. Fibroblasts from these mice in culture show defects in cytoskeletal architecture, traction stress generation, matrix production and organisation. Ablation of the three integrins leads to increased levels of discoidin domain receptor 2, an alternative receptor recognising collagens in vivo and in vitro. However, this overexpression fails to compensate adhesion and spreading defects on collagen substrates in vitro. Mice lacking collagen-binding integrins show a severely attenuated fibrotic response with impaired mechanotransduction, reduced collagen production and matrix organisation.

CONCLUSIONS

The data provide evidence for a crucial role of collagen-binding integrins in fibroblast force generation and differentiation in vitro and for matrix deposition and tissue remodelling in vivo. Targeting fibroblast-collagen interactions might represent a promising therapeutic approach to regulate connective tissue deposition in fibrotic diseases.

Tripterygium wilfordii derivative celastrol, a YAP inhibitor, has antifibrotic effects in systemic sclerosis

OBJECTIVES

Systemic sclerosis (SSc) is characterised by extensive tissue fibrosis maintained by mechanotranductive/proadhesive signalling. Drugs targeting this pathway are therefore of likely therapeutic benefit. The mechanosensitive transcriptional co-activator, yes activated protein-1 (YAP1), is activated in SSc fibroblasts. The terpenoid celastrol is a YAP1 inhibitor; however, if celastrol can alleviate SSc fibrosis is unknown. Moreover, the cell niches required for skin fibrosis are unknown.

METHODS

Human dermal fibroblasts from healthy individuals and patients with diffuse cutaneous SSc were treated with or without transforming growth factor β1 (TGFβ1), with or without celastrol. Mice were subjected to the bleomycin-induced model of skin SSc, in the presence or absence of celastrol. Fibrosis was assessed using RNA Sequencing, real-time PCR, spatial transcriptomic analyses, Western blot, ELISA and histological analyses.

RESULTS

In dermal fibroblasts, celastrol impaired the ability of TGFβ1 to induce an SSc-like pattern of gene expression, including that of cellular communication network factor 2, collagen I and TGFβ1. Celastrol alleviated the persistent fibrotic phenotype of dermal fibroblasts cultured from lesions of SSc patients. In the bleomycin-induced model of skin SSc, increased expression of genes associated with reticular fibroblast and hippo/YAP clusters was observed; conversely, celastrol inhibited these bleomycin-induced changes and blocked nuclear localisation of YAP.

CONCLUSIONS

Our data clarify niches within the skin activated in fibrosis and suggest that compounds, such as celastrol, that antagonise the YAP pathway may be potential treatments for SSc skin fibrosis.

A cysteine proteinase inhibitor ALLN alleviates bleomycin-induced skin and lung fibrosis

BACKGROUND

Systemic sclerosis (SSc) is a connective tissue disease that is characterized by fibrosis in the skin and internal organs, such as the lungs. Activated differentiation of progenitor cells, which are mainly resident fibroblasts, into myofibroblasts is considered a key mechanism underlying the overproduction of extracellular matrix and the resultant tissue fibrosis in SSc. Calpains are members of the Ca2+-dependent cysteine protease family, whose enzymatic activities participate in signal transduction and tissue remodeling, potentially contributing to fibrosis in various organs. However, the roles of calpain in the pathogenesis of SSc remain unknown. This study aimed to examine the anti-fibrotic properties of N-acetyl-Leu-Leu-norleucinal (ALLN), one of the cysteine proteinase inhibitors that primarily inhibit calpain, in vitro and in vivo, to optimally translate into the therapeutic utility in human SSc.

METHODS

Normal human dermal and lung fibroblasts pretreated with ALLN were stimulated with recombinant transforming growth factor beta 1 (TGF-β1), followed by assessment of TGF-β1/Smad signaling and fibrogenic molecules.

RESULTS

ALLN treatment significantly inhibited TGF-β1-induced phosphorylation and nuclear transport of Smad2/3 in skin and lung fibroblasts. TGF-β1-dependent increases in α-smooth muscle actin (αSMA), collagen type I, fibronectin 1, and some mesenchymal transcription markers were attenuated by ALLN. Moreover, our findings suggest that ALLN inhibits TGF-β1-induced mesenchymal transition in human lung epithelial cells. Consistent with these in vitro findings, administering ALLN (3 mg/kg/day) three times a week intraperitoneally remarkably suppressed the development of skin and lung fibrosis in a SSc mouse model induced by daily subcutaneous bleomycin injection. The number of skin- and lung-infiltrating CD3+ T cells decreased in ALLN-treated mice compared with that in control-treated mice. Phosphorylation of Smad3 and/or an increase in αSMA-positive myofibroblasts was significantly inhibited by ALLN treatment on the skin and lungs. However, no adverse effects were observed.

CONCLUSIONS

Our results prove that calpains can be a novel therapeutic target for skin and lung fibrosis in SSc, considering its inhibitor ALLN.

CXCL9 Links Skin Inflammation and Fibrosis through CXCR3-Dependent Upregulation of Col1a1 in Fibroblasts

Morphea is characterized by initial inflammation followed by fibrosis of the skin and soft tissue. Despite its substantial morbidity, the pathogenesis of morphea is poorly studied. Previous work showed that CXCR3 ligands CXCL9 and CXCL10 are highly upregulated in the sera and lesional skin of patients with morphea. We found that an early inflammatory subcutaneous bleomycin mouse model of dermal fibrosis mirrors the clinical, histological, and immune dysregulation observed in human morphea. We used this model to examine the role of the CXCR3 chemokine axis in the pathogenesis of cutaneous fibrosis. Using the REX3 (Reporting the Expression of CXCR3 ligands) mice, we characterized which cells produce CXCR3 ligands over time. We found that fibroblasts contribute the bulk of CXCL9-RFP and CXCL10-BFP by percentage, whereas macrophages produce high amounts on a per-cell basis. To determine whether these chemokines are mechanistically involved in pathogenesis, we treated Cxcl9-, Cxcl10-, or Cxcr3-deficient mice with bleomycin and found that fibrosis is dependent on CXCL9 and CXCR3. Addition of recombinant CXCL9 but not CXCL10 to cultured mouse fibroblasts induced Col1a1 mRNA expression, indicating that the chemokine itself contributes to fibrosis. Taken together, our studies provide evidence that CXCL9 and its receptor CXCR3 are functionally required for inflammatory fibrosis.

ATRA ameliorates fibrosis by suppressing the pro-fibrotic molecule Fra2/AP-1 in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disease that leads to irreversible fibrosis of the skin and the internal organs. The etiology of SSc is complex, its pathophysiology is poorly understood, and clinical therapeutic options are restricted. Thus, research into medications and targets for treating fibrosis is essential and urgent. Fos-related antigen 2 (Fra2) is a transcription factor that is a member of the activator protein-1 family. Fra2 transgenic mice were shown to have spontaneous fibrosis. All-trans retinoic acid (ATRA) is a vitamin A intermediate metabolite and ligand for the retinoic acid receptor (RAR), which possesses anti-inflammatory and anti-proliferative properties. Recent research has demonstrated that ATRA also has an anti-fibrotic effect. However, the exact mechanism is not fully understood. Interestingly, we identified potential binding sites for the transcription factor RARα to the promoter region of the FRA2 gene through JASPAR and PROMO databases. In this study, the pro-fibrotic effect of Fra2 in SSc is confirmed. SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc animals exhibit increased levels of Fra2. Inhibition of Fra2 expression in SSc dermal fibroblasts with Fra2 siRNA markedly decreased collagen I expression. ATRA reduced the expressions of Fra2, collagen I, and α-smooth muscle actin(α-SMA) in SSc dermal fibroblasts and bleomycin-induced fibrotic tissues of SSc mice. In addition, chromatin immunoprecipitation and dual-luciferase assays demonstrated that retinoic acid receptor RARα binds to the FRA2 promoter and modulates its transcriptional activity. ATRA decreases collagen I expression both in vivo and in vitro via the reduction of Fra2 expression. This work establishes the rationale for expanding the use of ATRA in the treatment of SSc and indicates that Fra2 can be used as an anti-fibrotic target.

Injectable, Drug-Eluting Nanocrystals Prevent Fibrosis and Stricture Formation In Vivo

BACKGROUND & AIMS

Tissue fibrosis results from uncontrolled healing responses leading to excessive mesenchymal cell activation and collagen and other extracellular matrix deposition. In the gastrointestinal tract, fibrosis leads to narrowing of the lumen and stricture formation. A drug treatment to prevent fibrosis and strictures in the gastrointestinal tract would be transformational for patient care. We aimed to develop a stricture treatment with the following characteristics and components: a small molecule with strong antifibrotic effects that is delivered locally at the site of the stricture to ensure correct lesional targeting while protecting the systemic circulation, and that is formulated with sustained-release properties to act throughout the wound healing processes.

METHODS

A high-throughput drug screening was performed to identify small molecules with antifibrotic properties. Next, we formulated an antifibrotic small molecule for sustained release and tested its antifibrotic potential in 3 animal models of fibrosis.

RESULTS

Sulconazole, a US Food and Drug Administration-approved drug for fungal infections, was found to have strong antifibrotic properties. Sulconazole was formulated as sulconazole nanocrystals for sustained release. We found that sulconazole nanocrystals provided superior or equivalent fibrosis prevention with less frequent dosing in mouse models of skin and intestinal tissue fibrosis. In a patient-like swine model of bowel stricture, a single injection of sulconazole nanocrystals prevented stricture formation.

CONCLUSIONS

The current data lay the foundation for further studies to improve the management of a range of diseases and conditions characterized by tissue fibrosis.

Bioinformatics-integrated screening of systemic sclerosis-specific expressed markers to identify therapeutic targets

BACKGROUND

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by extensive skin fibrosis. There are no effective treatments due to the severity, multiorgan presentation, and variable outcomes of the disease. Here, integrated bioinformatics was employed to discover tissue-specific expressed hub genes associated with SSc, determine potential competing endogenous RNAs (ceRNA) regulatory networks, and identify potential targeted drugs.

METHODS

In this study, four datasets of SSc were acquired. To identify the genes specific to tissues or organs, the BioGPS web database was used. For differentially expressed genes (DEGs), functional and enrichment analyses were carried out, and hub genes were screened and shown in a network of protein-protein interactions (PPI). The potential lncRNA-miRNA-mRNA ceRNA network was constructed using the online databases. The specifically expressed hub genes and ceRNA network were validated in the SSc mouse and in normal mice. We also used the receiver operating characteristic (ROC) curve to determine the diagnostic values of effective biomarkers in SSc. Finally, the Drug-Gene Interaction Database (DGIdb) identified specific medicines linked to hub genes.

RESULTS

The pooled datasets identified a total of 254 DEGs. The tissue/organ-specifically expressed genes involved in this analysis are commonly found in the hematologic/immune system and bone/muscle tissue. The enrichment analysis of DEGs revealed the significant terms such as regulation of actin cytoskeleton, immune-related processes, the VEGF signaling pathway, and metabolism. Cytoscape identified six gene cluster modules and 23 hub genes. And 4 hub genes were identified, including Serpine1, CCL2, IL6, and ISG15. Consistently, the expression of Serpine1, CCL2, IL6, and ISG15 was significantly higher in the SSc mouse model than in normal mice. Eventually, we found that MALAT1-miR-206-CCL2, let-7a-5p-IL6, and miR-196a-5p-SERPINE1 may be promising RNA regulatory pathways in SSc. Besides, ten potential therapeutic drugs associated with the hub gene were identified.

CONCLUSIONS

This study revealed tissue-specific expressed genes, SERPINE1, CCL2, IL6, and ISG15, as effective biomarkers and provided new insight into the mechanisms of SSc. Potential RNA regulatory pathways, including MALAT1-miR-206-CCL2, let-7a-5p-IL6, and miR-196a-5p-SERPINE1, contribute to our knowledge of SSc. Furthermore, the analysis of drug-hub gene interactions predicted TIPLASININ, CARLUMAB and BINDARIT as candidate drugs for SSc.

MKP-1 Deficiency Exacerbates Skin Fibrosis in a Mouse Model of Scleroderma

Scleroderma is a chronic fibrotic disease, where proinflammatory and profibrotic events precede collagen accumulation. MKP-1 [mitogen-activated protein kinase (MAPK) phosphatase-1] downregulates inflammatory MAPK pathways suppressing inflammation. MKP-1 also supports Th1 polarization, which could shift Th1/Th2 balance away from profibrotic Th2 profile prevalent in scleroderma. In the present study, we investigated the potential protective role of MKP-1 in scleroderma. We utilized bleomycin-induced dermal fibrosis model as a well-characterized experimental model of scleroderma. Dermal fibrosis and collagen deposition as well as the expression of inflammatory and profibrotic mediators were analyzed in the skin samples. Bleomycin-induced dermal thickness and lipodystrophy were increased in MKP-1-deficient mice. MKP-1 deficiency enhanced collagen accumulation and increased expression of collagens, 1A1 and 3A1, in the dermis. Bleomycin-treated skin from MKP-1-deficient mice also showed enhanced expression of inflammatory and profibrotic factors IL-6, TGF-β1, fibronectin-1 and YKL-40, and chemokines MCP-1, MIP-1α and MIP-2, as compared to wild-type mice. The results show, for the first time, that MKP-1 protects from bleomycin-induced dermal fibrosis, suggesting that MKP-1 favorably modifies inflammation and fibrotic processes that drive the pathogenesis of scleroderma. Compounds enhancing the expression or activity of MKP-1 could thus prevent fibrotic processes in scleroderma and possess potential as a novel immunomodulative drug.

STAT6 suppression prevents bleomycin-induced dermal fibrosis

Fibrosis of the skin and internal organs is a hallmark of systemic sclerosis (SSc). Although the pathogenesis of SSc is poorly understood, increasing evidence suggests that interleukins (IL)-4 and - 13 contribute to the pathogenesis of skin fibrosis by promoting collagen production and myofibroblast differentiation. Signal transducers and activators of transcription 6 (STAT6) is one of the most important downstream transcription factors activated by both IL-4 and IL-13. However, it is not completely understood whether STAT6 plays a role during the pathogenesis of skin fibrosis in SSc. In this study, we observed increased STAT6 phosphorylation in fibrotic skin samples collected from SSc patients as well as bleomycin-injected murine mice. Knockout of Stat6 in mice significantly (1) suppressed the expression of fibrotic cytokines including Il13, Il17, Il22, Ccl2, and the alternatively activated macrophage marker Cd206; (2) reduced the production of collagen and fibronectin, and (3) attenuated late-stage skin fibrosis and inflammation induced by bleomycin. Consistently, mice treated with STAT6 inhibitor AS1517499 also attenuated skin fibrosis on day 28. In addition, a co-culture experiment demonstrated that skin epithelial cells with STAT6 knockdown had reduced cytokine expression in response to IL-4/IL-13, and subsequently attenuated fibrotic protein expression in skin fibroblasts. On the other side, STAT6 depletion in skin fibroblasts attenuated IL-4/IL-13-induced cytokine and fibrotic marker expression, and reduced CXCL2 expression in co-cultured keratinocytes. In summary, our study highlighted an important yet not fully understood role of STAT6 in skin fibrosis by driving innate inflammation and differentiation of alternatively activated macrophages in response to injury.

Loss of Protein Kinase D2 Activity Protects Against Bleomycin-Induced Dermal Fibrosis in Mice

Protein kinase D (PKD) has been linked to inflammatory responses in various pathologic conditions; however, its role in inflammation-induced dermal fibrosis has not been evaluated. In this study, we aimed to investigate the roles and mechanisms of protein kinase D2 (PKD2) in inflammation-induced dermal fibrosis and evaluate the therapeutic potential of PKD inhibitors in this disease. Using homozygous kinase-dead PKD2 knock-in (KI) mice, we examined whether genetic ablation or pharmacologic inhibition of PKD2 activity affected dermal inflammation and fibrosis in a bleomycin (BLM)-induced skin fibrosis model. Our data showed that dermal thickness and collagen fibers were significantly reduced in BLM-treated PKD2 KI mice compared with that in wild-type mice, and so was the expression of α-smooth muscle actin and collagens and the mRNA levels of transforming growth factor-β1 and interleukin-6 in the KI mice. Corroboratively, pharmacologic inhibition of PKD by CRT0066101 also significantly blocked BLM-induced dermal fibrosis and reduced α-smooth muscle actin, collagen, and interleukin-6 expression. Further analyses indicated that loss of PKD2 activity significantly blocked BLM-induced infiltration of monocytes/macrophages and neutrophils in the dermis. Moreover, using bone marrow-derived macrophages, we demonstrated that PKD activity was required for cytokine production and migration of macrophages. We have further identified Akt as a major downstream target of PKD2 in the early inflammatory phase of the fibrotic process. Taken together, our findings indicate that PKD2 promotes dermal fibrosis via regulating immune cell infiltration, cytokine production, and downstream activation of Akt in lesional skin, and targeted inhibition of PKD2 may benefit the treatment of this condition.

Using the Bleomycin-Induced Model of Fibrosis to Study the Contribution of CCN Proteins to Scleroderma Fibrosis

Approximately 45% of the deaths in the developed world result from conditions with a fibrotic component. Although no specific, focused anti-fibrotic therapies have been approved for clinical use, a long-standing concept is that targeting CCN proteins may be useful to treat fibrosis. Herein, we summarize current data supporting the concept that targeting CCN2 may be a viable anti-fibrotic approach to treat scleroderma. Testing this hypothesis has been made possible by using a mouse model of inflammation-driven skin and lung fibrosis.

Epiregulin is a dendritic cell-derived EGFR ligand that maintains skin and lung fibrosis

Immune cells are fundamental regulators of extracellular matrix (ECM) production by fibroblasts and have important roles in determining extent of fibrosis in response to inflammation. Although much is known about fibroblast signaling in fibrosis, the molecular signals between immune cells and fibroblasts that drive its persistence are poorly understood. We therefore analyzed skin and lung samples of patients with diffuse cutaneous systemic sclerosis, an autoimmune disease that causes debilitating fibrosis of the skin and internal organs. Here, we define a critical role of epiregulin-EGFR signaling between dendritic cells and fibroblasts to maintain elevated ECM production and accumulation in fibrotic tissue. We found that epiregulin expression marks an inducible state of DC3 dendritic cells triggered by type I interferon and that DC3-derived epiregulin activates EGFR on fibroblasts, driving a positive feedback loop through NOTCH signaling. In mouse models of skin and lung fibrosis, epiregulin was essential for persistence of fibrosis in both tissues, which could be abrogated by epiregulin genetic deficiency or a neutralizing antibody. Therapeutic administration of epiregulin antibody reversed fibrosis in patient skin and lung explants, identifying it as a previously unexplored biologic drug target. Our findings reveal epiregulin as a crucial immune signal that maintains skin and lung fibrosis in multiple diseases and represents a promising antifibrotic target.

SARA suppresses myofibroblast precursor transdifferentiation in fibrogenesis in a mouse model of scleroderma

We previously reported that Smad anchor for receptor activation (SARA) plays a critical role in maintaining epithelial cell phenotype. Here, we show that SARA suppressed myofibroblast precursor transdifferentiation in a mouse model of scleroderma. Mice overexpressing SARA specifically in PDGFR-β+ pericytes and pan-leukocytes (SARATg) developed significantly less skin fibrosis in response to bleomycin injection compared with wild-type littermates (SARAWT). Single-cell RNA-Seq analysis of skin PDGFR-β+ cells implicated pericyte subsets assuming myofibroblast characteristics under fibrotic stimuli, and SARA overexpression blocked the transition. In addition, a cluster that expresses molecules associated with Th2 cells and macrophage activation was enriched in SARAWT mice, but not in SARATg mice, after bleomycin treatment. Th2-specific Il-31 expression was increased in skin of the bleomycin-treated SARAWT mice and patients with scleroderma (or systemic sclerosis, SSc). Receptor-ligand analyses indicated that lymphocytes mediated pericyte transdifferentiation in SARAWT mice, while with SARA overexpression the myofibroblast activity of pericytes was suppressed. Together, these data suggest a potentially novel crosstalk between myofibroblast precursors and immune cells in the pathogenesis of SSc, in which SARA plays a critical role.

Establishment of a humanized animal model of systemic sclerosis in which T helper-17 cells from patients with systemic sclerosis infiltrate and cause fibrosis in the lungs and skin

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by inflammation, microangiopathy, and progressive fibrosis in the skin and internal organs. To evaluate the pathophysiologic mechanisms and efficacies of potential therapeutics for SSc, a preclinical model recapitulating the disease phenotypes is needed. Here, we introduce a novel animal model for SSc using immunodeficient mice injected with peripheral blood mononuclear cells (PBMCs) from SSc patients. Human PBMCs acquired from SSc patients and healthy controls were transferred into NOD.Cg-Prkdc^scidIl2rg^tm1Wjl (NSG) mice with concurrent bleomycin injection. Blood, skin, and lung tissues were acquired and analyzed after PBMC engraftment. In addition, we investigated whether the humanized murine model could be used to assess the efficacy of potential therapeutics for SSc. Human PBMCs from SSc patients and healthy controls were engrafted into the blood, skin, and lung tissues of NSG mice. Histological analysis of affected tissues from mice treated with SSc PBMCs (SSc hu-mice) demonstrated substantial inflammation, fibrosis and vasculopathy with human immune cell infiltration and increased expression of IL-17, TGF-β, CCL2, CCL3, and CXCL9. The proportions of circulating and tissue-infiltrating T helper 17 (Th17) cells were elevated in SSc hu-mice. These cells showed increased expression of CXCR3 and phosphorylated STAT3. SSc hu-mice treated with rebamipide and other potential Th17-cell-modulating drugs presented significantly reduced tissue fibrosis. Mice injected with patient-derived PBMCs show promise as an animal model of SSc.

A humanized mouse model of the autoimmune disease systemic sclerosis (SSc) could improve understanding of disease progression and provide a trial platform for potential treatments. SSc results in inflammation and progressive fibrosis in the skin, heart, lungs and kidneys. Existing animal models for SSc are unable to fully mimic the mechanisms behind the disease. Mi-La Cho and Sung-Hwan Park at the Catholic University of Korea, Seoul, South Korea, and co-workers injected peripheral blood cells from patients with SSc into immune-deficent mice, generating a humanized animal model. Several weeks after, the team analysed blood and tissue samples from the mice and found significant inflammation and fibrosis in the skin and lungs, consistent with SSc. Levels of proinflammatory proteins and specific human T-helper cells were significantly elevated, providing possible insights into disease initiation and progression.

Topical application of an irreversible small molecule inhibitor of lysyl oxidases ameliorates skin scarring and fibrosis

Scarring is a lifelong consequence of skin injury, with scar stiffness and poor appearance presenting physical and psychological barriers to a return to normal life. Lysyl oxidases are a family of enzymes that play a critical role in scar formation and maintenance. Lysyl oxidases stabilize the main component of scar tissue, collagen, and drive scar stiffness and appearance. Here we describe the development and characterisation of an irreversible lysyl oxidase inhibitor, PXS-6302. PXS-6302 is ideally suited for skin treatment, readily penetrating the skin when applied as a cream and abolishing lysyl oxidase activity. In murine models of injury and fibrosis, topical application reduces collagen deposition and cross-linking. Topical application of PXS-6302 after injury also significantly improves scar appearance without reducing tissue strength in porcine injury models. PXS-6302 therefore represents a promising therapeutic to ameliorate scar formation, with potentially broader applications in other fibrotic diseases.

Chemokines form nanoparticles with DNA and can superinduce TLR-driven immune inflammation

Chemokines control the migratory patterns and positioning of immune cells to organize immune responses to pathogens. However, many chemokines have been associated with systemic autoimmune diseases that have chronic IFN signatures. We report that a series of chemokines, including CXCL4, CXCL10, CXCL12, and CCL5, can superinduce type I IFN (IFN-I) by TLR9-activated plasmacytoid DCs (pDCs), independently of their respective known chemokine receptors. Mechanistically, we show that chemokines such as CXCL4 mediate transcriptional and epigenetic changes in pDCs, mostly targeted to the IFN-I pathways. We describe that chemokines physically interact with DNA to form nanoparticles that promote clathrin-mediated cellular uptake and delivery of DNA in the early endosomes of pDCs. Using two separate mouse models of skin inflammation, we observed the presence of CXCL4 associated with DNA in vivo. These data reveal a noncanonical role for chemokines to serve as nucleic acid delivery vectors to modulate TLR signaling, with implications for the chronic presence of IFN-I by pDCs in autoimmune diseases.

Effect of Adipose-Derived Stem Cell on Collagen Deposition in Nude Mouse Model of Scleroderma

Systemic sclerosis is an autoimmune disease featured by uncontrolled fibrosis and collagen deposition. This study aimed to investigate the impact of adipose-derived stem cells (ADSCs) transplantation on collagen in scleroderma. After establishment of scleroderma model using Bleomycin, the animals received subcutaneous injection of 0.3 ml fat (group B) or 0.3 ml fat+1×106 ADSCs (group C), or 1×106 ADSCs alone (group D). Mice treated with PBS were taken as control group (group A). One month after operation, the skin tissue at injection site was collected for H&E staining, and immunohistochemistry to determine the content of TGF-β1 and type III collagen. Compared to control group, group B, C, and D exhibited improvement in collagen deposition and reduction in TGF-β1 content and type III collagen. Combined graft of fat and ADSCs exerted more significant effect compared to single ADSCs treatment. In conclusion, fat and ADSCs transplantation improves collagen deposition in nude mice with scleroderma and the combined treatment exerts a higher efficacy, suggesting that ADSCs need adipose carrier and microenvironment. These findings provide a novel insight into the treatment of scleroderma.

Myeloid cell-specific deletion of Capns1 prevents macrophage polarization toward the M1 phenotype and reduces interstitial lung disease in the bleomycin model of systemic sclerosis

Background

Calpains are a family of calcium-dependent thiol proteases that participate in a wide variety of biological activities. In our recent study, calpain is increased in the sera of scleroderma or systemic sclerosis (SSc). However, the role of calpain in interstitial lung disease (ILD) has not been reported. ILD is a severe complication of SSc, which is the leading cause of death in SSc. The pathogenesis of SSc-related ILD remains incompletely understood. This study investigated the role of myeloid cell calpain in SSc-related ILD.

Methods

A novel line of mice with myeloid cell-specific deletion of Capns1 (Capns1-ko) was created. SSc-related ILD was induced in Capns1-ko mice and their wild-type littermates by injection 0.l mL of bleomycin (0.4 mg/mL) for 4 weeks. In a separate experiment, a pharmacological inhibitor of calpain PD150606 (Biomol, USA, 3 mg/kg/day, i.p.) daily for 30 days was given to mice after bleomycin injection on daily basis. At the end of the experiment, the animals were killed, skin and lung tissues were collected for the following analysis. Inflammation, fibrosis and calpain activity and cytokines were assessed by histological examinations and ELISA, and immunohistochemical analyses, western blot analysis and Flow cytometry analysis.

Results

Calpain activities increased in SSc-mouse lungs. Both deletion of Capns1 and administration of PD150606 attenuated dermal sclerosis as evidenced by a reduction of skin thickness and reduced interstitial fibrosis and inflammation in bleomycin model of SSc mice. These effects of reduced calpain expression or activity were associated with prevention of macrophage polarization toward M1 phenotype and consequent reduced production of pro-inflammatory cytokines including TNF-α, IL-12 and IL-23 in lung tissues of Capns1-ko mice with bleomycin model of SSc. Furthermore, inhibition of calpain correlated with an increase in the protein levels of PI3K and phosphorylated AKT1 in lung tissues of the bleomycin model of SSc mice.

Conclusions

This study for the first time demonstrates that the role of myeloid cell calpain may be promotion of macrophage M1 polarization and pro-inflammatory responses related PI3K/AKT1 signaling. Thus, myeloid cell calpain may be a potential therapeutic target for bleomycin model of SSc-related ILD.

Skin Fibrosis and Recovery Is Dependent on Wnt Activation via DPP4

Fibrosis is the life-threatening, excessive accumulation of the extracellular matrix and is sometimes associated with a loss of lipid-filled cells in the skin and other organs. Understanding the mechanisms of fibrosis and associated lipodystrophy and their reversal may reveal new targets for therapeutic intervention. In vivo genetic models are needed to identify key targets that induce recovery from established fibrosis. Wnt signaling is activated in animal and human fibrotic diseases across organs. Here, we developed a genetically inducible and reversible Wnt activation model and showed that it is sufficient to cause fibrotic dermal remodeling, including extracellular matrix expansion and shrinking of dermal adipocytes. Upon withdrawal from Wnt activation, Wnt-induced fibrotic remodeling was reversed in mouse skin-fully restoring skin architecture. Next, we demonstrated CD26/ DPP4 is a Wnt/β-catenin-responsive gene and a functional mediator of fibrotic transformation. We provide genetic evidence that the Wnt/DPP4 axis is required to drive fibrotic dermal remodeling and is associated with human skin fibrosis severity. Remarkably, DPP4 inhibitors can be repurposed to accelerate recovery from established Wnt-induced fibrosis. Collectively, this study identifies Wnt/DPP4 axis as a key driver of extracellular matrix homeostasis and dermal fat loss, providing therapeutic avenues to manipulate the onset and reversal of tissue fibrosis.

Animal Models of Systemic Sclerosis: Using Nailfold Capillaroscopy as a Potential Tool to Evaluate Microcirculation and Microangiopathy: A Narrative Review

Systemic sclerosis (SSc) is an autoimmune disease with three pathogenic hallmarks, i.e., inflammation, vasculopathy, and fibrosis. A wide plethora of animal models have been developed to address the complex pathophysiology and for the development of possible anti-fibrotic treatments. However, no current model comprises all three pathological mechanisms of the disease. To highlight the lack of a complete model, a review of some of the most widely used animal models for SSc was performed. In addition, to date, no model has accomplished the recreation of primary or secondary Raynaud’s phenomenon, a key feature in SSc. In humans, nailfold capillaroscopy (NFC) has been used to evaluate secondary Raynaud’s phenomenon and microvasculature changes in SSc. Being a non-invasive technique, it is widely used both in clinical studies and as a tool for clinical evaluation. Because of this, its potential use in animal models has been neglected. We evaluated NFC in guinea pigs to investigate the possibility of applying this technique to study microcirculation in the nailfold of animal models and in the future, development of an animal model for Raynaud’s phenomenon. The applications are not only to elucidate the pathophysiological mechanisms of vasculopathy but can also be used in the development of novel treatment options.

The compound LG283 inhibits bleomycin-induced skin fibrosis via antagonizing TGF-β signaling

Background

Systemic sclerosis (SSc) is a collagen disease that exhibits intractable fibrosis and vascular injury of the skin and internal organs. Transforming growth factor-β (TGF-β)/Smad signaling plays a central role in extracellular matrix (ECM) production by α-SMA-positive myofibroblasts. Myofibroblasts may be partially derived from various precursor cells in addition to resident fibroblasts. Recently, our high-throughput in vitro screening discovered a small compound, LG283, that may disrupt the differentiation of epithelial cells into myofibroblasts. This compound was originally generated as a curcumin derivative.

Methods

In this study, we investigated the effect of LG283 on inhibiting fibrosis and its mechanism. The action of LG283 on TGF-β-dependent fibrogenic activity and epithelial-mesenchymal transition (EMT) was analyzed in vitro. The effects of LG283 were also examined in a bleomycin-induced skin fibrosis mouse model.

Results

LG283 suppressed TGF-β-induced expression of ECM, α-SMA, and transcription factors Snail 1 and 2, and Smad3 phosphorylation in cultured human dermal fibroblasts. LG283 was also found to block EMT induction in cultured human epithelial cells. During these processes, Smad3 phosphorylation and/or expression of Snail 1 and 2 were inhibited by LG283 treatment. In the bleomycin-induced skin fibrosis model, oral administration of LG283 efficiently protected against the development of fibrosis and decrease of capillary vessels without significantly affecting cell infiltration or cytokine concentrations in the skin. No apparent adverse effects of LG283 were found. LG283 treatment remarkably inhibited the enhanced expression of α-SMA and phosphorylated Smad3, as well as those of Snail 1 and 2, in the bleomycin-injected skin.

Conclusions

The LG283 compound exhibits antagonistic activity on fibrosis and vascular injury through inhibition of TGF-β/Smad/Snail mesenchymal transition pathways and thus, may be a candidate therapeutic for the treatment of SSc. Although the involvement of EMT in the pathogenesis of SSc remains unclear, the screening of EMT regulatory compounds may be an attractive approach for SSc therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02773-2.

A Systematic Review Comparing Animal and Human Scarring Models

Introduction

A reproducible, standardised model for cutaneous scar tissue to assess therapeutics is crucial to the progress of the field. A systematic review was performed to critically evaluate scarring models in both animal and human research.

Method

All studies in which cutaneous scars are modelling in animals or humans were included. Models that were focused on the wound healing process or those in humans with scars from an existing injury were excluded. Ovid Medline^® was searched on 25 February 2019 to perform two near identical searches; one aimed at animals and the other aimed at humans. Two reviewers independently screened the titles and abstracts for study selection. Full texts of potentially suitable studies were then obtained for analysis.

Results

The animal kingdom search yielded 818 results, of which 71 were included in the review. Animals utilised included rabbits, mice, pigs, dogs and primates. Methods used for creating scar tissue included sharp excision, dermatome injury, thermal injury and injection of fibrotic substances. The search for scar assessment in humans yielded 287 results, of which 9 met the inclusion criteria. In all human studies, sharp incision was used to create scar tissue. Some studies focused on patients before or after elective surgery, including bilateral breast reduction, knee replacement or midline sternotomy.

Discussion

The rabbit ear scar model was the most popular tool for scar research, although pigs produce scar tissue which most closely resembles that of humans. Immunodeficient mouse models allow for in vivo engraftment and study of human scar tissue, however, there are limitations relating to the systemic response to these xenografts. Factors that determine the use of animals include cost of housing requirements, genetic traceability, and ethical concerns. In humans, surgical patients are often studied for scarring responses and outcomes, but reproducibility and patient factors that impact healing can limit interpretation. Human tissue use in vitro may serve as a good basis to rapidly screen and assess treatments prior to clinical use, with the advantage of reduced cost and setup requirements.

PLG nanoparticles target fibroblasts and MARCO+ monocytes to reverse multi-organ fibrosis

Systemic sclerosis (SSc) is a chronic, multisystem orphan disease with a highly variable clinical course, high mortality rate, and a poorly understood complex pathogenesis. We have identified an important role for a subpopulation of monocytes and macrophages characterized by surface expression of the scavenger receptor macrophage receptor with collagenous structure (MARCO) in chronic inflammation and fibrosis in SSc and in preclinical disease models. We show that MARCO⁺ monocytes and macrophages accumulate in lesional skin and lung in topographic proximity to activated myofibroblasts in patients with SSc and in the bleomycin-induced mouse model of SSc. Short-term treatment of mice with a potentially novel nanoparticle, poly(lactic-co-glycolic) acid (PLG), which is composed of a carboxylated, FDA-approved, biodegradable polymer and modulates activation and trafficking of MARCO⁺ inflammatory monocytes, markedly attenuated bleomycin-induced skin and lung inflammation and fibrosis. Mechanistically, in isolated cells in culture, PLG nanoparticles inhibited TGF-dependent fibrotic responses in vitro. Thus, MARCO⁺ monocytes are potent effector cells of skin and lung fibrosis and can be therapeutically targeted in SSc using PLG nanoparticles.

Esomeprazole alleviates fibrosis in systemic sclerosis by modulating AhR/Smad2/3 signaling

Systemic sclerosis (SSc) is a connective tissue disease with the involvement of complex signaling pathways, such as TGF-β/Smad2/3. SSc can lead to severe multiple organ fibrosis, but no effective therapy is currently available because of its unclear pathogenesis. Exploring new treatments is the focus of recent research on SSc. Recent studies have implied a potential antifibrotic role of esomeprazole (ESO), but with currently unidentified mechanisms. Signaling of AhR, a ligand-dependent transcription factor, has been described as a key controller of fibrosis, tumorigenesis, and immune balance. Recently, it has been reported that ESO may be an exogenous agonist of AhR signaling, while no previous study has revealed the effects of ESO on SSc and its underlying mechanisms. In this study, we demonstrate that ESO suppresses the migration of SSc dermal fibroblasts, downregulates profibrotic markers, including COLIA1, α-SMA CTGF and MMP1, and limits collagen production potentially via the activation of AhR signaling. More importantly, ESO could block Smad2/3 phosphorylation concurrently with the reduction in collagen via AhR signaling. Moreover, our results from the bleomycin (BLM)-induced SSc model in skin and lung shows that ESO ameliorates fibrosis in vivo, which in keeping with our in vitro results. We conclude that ESO is a potential therapeutic drug for SSc fibrosis.

Inhibition of PDE4 by apremilast attenuates skin fibrosis through directly suppressing activation of M1 and T cells

Systemic sclerosis (SSc) is a life-threatening chronic connective tissue disease with the characteristics of skin fibrosis, vascular injury, and inflammatory infiltrations. Though inhibition of phosphodiesterase 4 (PDE4) has been turned out to be an effective strategy in suppressing inflammation through promoting the accumulation of intracellular cyclic adenosine monophosphate (cAMP), little is known about the functional modes of inhibiting PDE4 by apremilast on the process of SSc. The present research aimed to investigate the therapeutic effects and underlying mechanism of apremilast on SSc. Herein, we found that apremilast could markedly ameliorate the pathological manifestations of SSc, including skin dermal thickness, deposition of collagens, and increased expression of α-SMA. Further study demonstrated that apremilast suppressed the recruitment and activation of macrophages and T cells, along with the secretion of inflammatory cytokines, which accounted for the effects of apremilast on modulating the pro-fibrotic processes. Interestingly, apremilast could dose-dependently inhibit the activation of M1 and T cells in vitro through promoting the phosphorylation of CREB. In summary, our research suggested that inhibiting PDE4 by apremilast might provide a novel therapeutic option for clinical treatment of SSc patients.

Expression of the α7 Nicotinic Acetylcholine Receptor Is Critically Required for the Antifibrotic Effect of PHA-543613 on Skin Fibrosis

INTRODUCTION

Targeting the α7 nicotinic acetylcholine receptor (α7nAChR) has recently been suggested as a potential new treatment for fibrotic skin diseases. Here, we performed a genetic and pharmacologic approach to clarify the role of this receptor in the bleomycin (BLM) mouse model of skin fibrosis using α7nAChR KO mice.

METHODS

We analyzed the expression of extracellular matrix (ECM) components in murine skin using quantitative RT-PCR, pepsin digestion/SDS-PAGE of proteins and performed hydroxyproline assays as well as histological/immunohistochemical staining of skin sections. To identity the target cells of the α7nAChR agonist PHA-543613, we used murine dermal fibroblasts (MDF). We tested their response to the profibrotic cytokine transforming growth factor-β1 (TGF-β1) and utilized gene silencing to elucidate the role of the α7nAChR.

RESULTS

We confirmed our previous findings on C3H/HeJ mice and detected a suppressive effect of PHA-543613 on BLM-induced skin fibrosis in the mouse strain C57BL/6J. This antifibrotic effect of PHA-543613 was abrogated in α7nAChR-KO mice. Interestingly, α7nAChR-KO animals exhibited a basal profibrotic signature by higher RNA expression of ECM genes and hydroxyproline content than WT mice. In WT MDF, PHA-543613 suppressed ECM gene expression induced by TGF-β1. Gene silencing of α7nAChR by small interfering RNA neutralized the effects of PHA-543613 on TGF-β1-mediated ECM gene expression.

CONCLUSION

In summary, we have identified the α7nAChR as the essential mediator of the antifibrotic effect of PHA-543613. MDF are directly targeted by PHA-543613 to suppress collagen synthesis. Our findings emphasize therapeutic exploitation of α7nAChR receptor agonists in fibrotic skin diseases.

Progesterone Aggravates Lung Fibrosis in a Mouse Model of Systemic Sclerosis

Background

Gender-related factors have explained the higher prevalence of autoimmune diseases in women. Sex hormones play a key role in the immune system and parenchymal cells function; therefore, these hormones can be important in the pathogenesis of autoimmune diseases as a risk or beneficial factor. Lung fibrosis is the main cause of mortality in systemic sclerosis, a female predominant autoimmune disease. The objective of this study was to examine the effect of progesterone on lung fibrosis in a mouse model of systemic sclerosis.

Methods

Mice with bleomycin-induced lung fibrosis treated with progesterone subcutaneously for 21 and 28 days. Blood was collected for hormone and cytokine measurement at the end of treatment then, skin and lung tissues were harvested for histological assessment, gene expression, cytokine, hydroxyproline, and gelatinase measurement.

Results

Trichrome staining and hydroxyproline measurements showed that progesterone treatment increased the content of collagen in fibrotic and normal lung tissues. Progesterone increased α-SMA (P < 0.01), TGF- β (P < 0.05) and decreased MMP9 (P < 0.05) in fibrotic lung tissues. Also progesterone treatment decreased the gene expression of Col1a2 (P <0.05), Ctgf (P <01), End1 (0.001) in bleomycin- injured lung tissues. The serum level of TNF-α was decreased, but the serum level of cortisol was increased by progesterone treatment in fibrotic mice (P< 0.05).

Conclusion

Our results showed that progesterone aggravates lung fibrosis in a mouse model of systemic sclerosis.

Therapeutic effect of cyclin-dependent kinase 4/6 inhibitor on dermal fibrosis in murine models of systemic sclerosis

OBJECTIVE

Histology of systemic sclerosis (SSc) includes an increased number of myofibroblasts, where transforming growth factor-β (TGF-β) plays a crucial role to promote dermal fibrosis. The objectives of this study were to examine whether the inhibition of cell cycle with cyclin-dependent kinase (CDK) 4/6 inhibitor suppress fibroblast proliferation and the differentiation into myofibroblasts, and the therapeutic effect of a CDK4/6 inhibitor on dermal fibrosis in murine models of SSc in monotherapy or in combination with TGF-β receptor inhibitor (TGFβRI).

METHODS

SSc fibroblasts were cultured in the presence or absence of TGF-β. Effects of palbociclib (CDKI), a CDK4/6 inhibitor, on fibroblast proliferation and TGF-β-induced differentiation into myofibroblasts were examined with BrdU uptake, immunofluorescence, and immunoblotting. Hypochlorous acid (HOCl)- and bleomycin-induced dermal fibrosis models were used to study the effect of CDKI on dermal fibrosis in monotherapy or in combination with galunisertib, a TGFβRI.

RESULTS

CDKI suppressed the proliferation of SSc fibroblasts and their TGF-β-induced differentiation into myofibroblast without inhibiting canonical and non-canonical TGF-β signals. Treatment of dermal fibrosis models with CDKI decreased dermal thickness and collagen content, as well as fibroblast proliferation and myofibroblast number. The combination therapy with CDKI and TGFβRI exerted additive anti-fibrotic effects. Mechanistically, CDKI suppressed the expression of cellular communication network (CCN) 2 and cadherin-11 important for fibrosis.

CONCLUSION

We demonstrated the therapeutic effect of CDKI on dermal fibrosis in monotherapy or in combination with TGFβRI. CDKI should be a novel agent for the treatment of SSc, which may be used with TGFβRI to increase the efficacy.

MicroRNA-411-3p inhibits bleomycin-induced skin fibrosis by regulating transforming growth factor-β/Smad ubiquitin regulatory factor-2 signalling

Skin fibrosis, which is characterized by fibroblast proliferation and increased extracellular matrix, has no effective treatment. An increasing number of studies have shown that microRNAs (miRNAs/miRs) participate in the mechanism of skin fibrosis, such as in limited cutaneous systemic sclerosis and pathological scarring. The objective of the present study was to determine the role of miR‐411‐3p in bleomycin (BLM)‐induced skin fibrosis and skin fibroblast transformation. Using Western blot analysis and real‐time quantitative polymerase chain reaction assess the expression levels of miR‐411‐3p, collagen (COLI) and transforming growth factor (TGF)‐β/Smad ubiquitin regulatory factor (Smurf)‐2/Smad signalling factors both in vitro and in vivo with or without BLM. To explore the regulatory relationship between miR‐411‐3p and Smurf2, we used the luciferase reporter assay. Furthermore, miR‐411‐3p overexpression was identified in vitro and in vivo via transfection with Lipofectamine 2000 reagent and injection. Finally, we tested the dermal layer of the skin using haematoxylin and eosin and Van Gieson's staining. We found that miR‐411‐3p expression was decreased in bleomycin (BLM)‐induced skin fibrosis and fibroblasts. However, BLM accelerated transforming growth factor (TGF)‐β signalling and collagen production. Overexpression of miR‐411‐3p inhibited the expression of collagen, F‐actin and the TGF‐β/Smad signalling pathway factors in BLM‐induced skin fibrosis and fibroblasts. In addition, miR‐411‐3p inhibited the target Smad ubiquitin regulatory factor (Smurf)‐2. Furthermore, Smurf2 was silenced, which attenuated the expression of collagen via suppression of the TGF‐β/Smad signalling pathway. We demonstrated that miR‐411‐3p exerts antifibrotic effects by inhibiting the TGF‐β/Smad signalling pathway via targeting of Smurf2 in skin fibrosis.

Scleroderma-like Impairment in the Network of Telocytes/CD34+ Stromal Cells in the Experimental Mouse Model of Bleomycin-Induced Dermal Fibrosis

Considerable evidence accumulated over the past decade supports that telocytes (TCs)/CD34⁺ stromal cells represent an exclusive type of interstitial cells identifiable by transmission electron microscopy (TEM) or immunohistochemistry in various organs of the human body, including the skin. By means of their characteristic cellular extensions (telopodes), dermal TCs are arranged in networks intermingled with a multitude of neighboring cells and, hence, they are thought to contribute to skin homeostasis through both intercellular contacts and releasing extracellular vesicles. In this context, fibrotic skin lesions from patients with systemic sclerosis (SSc, scleroderma) appear to be characterized by a disruption of the dermal network of TCs, which has been ascribed to either cell degenerative processes or possible transformation into profibrotic myofibroblasts. In the present study, we utilized the well-established mouse model of bleomycin-induced scleroderma to gain further insights into the TC alterations found in cutaneous fibrosis. CD34 immunofluorescence revealed a severe impairment in the dermal network of TCs/CD34⁺ stromal cells in bleomycin-treated mice. CD31/CD34 double immunofluorescence confirmed that CD31^-/CD34⁺ TC counts were greatly reduced in the skin of bleomycin-treated mice compared with control mice. Ultrastructural signs of TC injury were detected in the skin of bleomycin-treated mice by TEM. The analyses of skin samples from mice treated with bleomycin for different times by either TEM or double immunostaining and immunoblotting for the CD34/α-SMA antigens collectively suggested that, although a few TCs may transition to α-SMA⁺ myofibroblasts in the early disease stage, most of these cells rather undergo degeneration, and then are lost. Taken together, our data demonstrate that TC changes in the skin of bleomycin-treated mice mimic very closely those observed in human SSc skin, which makes this experimental model a suitable tool to (i) unravel the pathological mechanisms underlying TC damage and (ii) clarify the possible contribution of the TC loss to the development/progression of dermal fibrosis. In perspective, these findings may have important implications in the field of skin regenerative medicine.

The Therapeutic Effects of Exosomes Derived from Human Umbilical Cord Mesenchymal Stem Cells on Scleroderma

Background:

Scleroderma is a multisystem disease in which tissue fibrosis is caused by inflammation and vascular damage. The mortality of scleroderma has remained high due to a lack of effective treatments. However, exosomes derived from human umbilical cord mesenchymal stem cells (HUMSCs)-Ex have been regarded as potential treatments for various autoimmune diseases, and may also act as candidates for treating scleroderma.

Methods:

Mice with scleroderma received a single 50 μg HUMSCs-Ex. HUMSCs-Ex was characterized using transmission electron microscopy, nanoparticle tracking analysis and nanoflow cytometry. The therapeutic efficacy was assessed using histopathology, immunohistochemistry, immunofluorescence, quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay and western blot.

Results:

HUMSCs-Ex ameliorated the deposition of extracellular matrix and suppressed the epithelial-mesenchymal transition process, and the effects lasted at least three weeks. In addition, HUMSCs-Ex promoted M1 macrophage polarization and inhibited M2 macrophage polarization, leading to the restoration of the balance of M1/M2 macrophages.

Conclusion:

We investigated the potential antifibrotic and anti-inflammatory effects of HUMSCs-Ex in a bleomycin-induced mouse model of scleroderma. So HUMSCs-Ex could be considered as a candidate therapy for scleroderma.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13770-021-00405-5.