Combined effect of genetic background and gender in a mouse model of bleomycin-induced skin fibrosis

The antifibrotic effect of Vildagliptin and Diaminodiphenyl Sulfone in murine schistosomiasis mansoni

Schistosomiasis drastically affects human health, where S. mansoni-induced hepatic fibrosis remains a serious problem with no available drug yet. The current study aimed to evaluate the hepatoprotective effects of Vildagliptin (Vilda), Diaminodiphenyl Sulfone (DDS), and their combination (Vilda/DDS) against S. mansoni-induced hepatic fibrosis and elucidate their underlying molecular mechanisms. S.mansoni-infected mice were administered praziquantel (PZQ) for two consecutive days, or Vilda, DDS, and Vilda/DDS for 14 consecutive days. Schistosomiasis-induced hepatic fibrosis was assessed parasitologically, biochemically, and pathologically. Results revealed that Vilda, DDS, and Vida/DDS treatments significantly reduced worm count, oogram stages, ova count, and ameliorated the granulomatous inflammatory reactions and hepatotoxicity indices. Moreover, they enhanced hepatic Nrf2/HO-1 pathway with significant increasing SOD and reducing MDA levels. Furthermore, they significantly downregulated the hepatic TLR4/NF-κB and NLRP3 inflammasome pathways leading to a significant reduction in TNF-α and caspase-1 levels which is important in the activation of IL-1β and caspase-3. Notably, significant downregulation in hepatic TGF-β1, α-SMA, and MMP-9 expressions were also recorded. In conclusion, Vilda/DDS showed antioxidant, anti-inflammatory and antifibrotic activities in comparison to either Vilda or DDS alone against S. mansoni-induced hepatic fibrosis. Therefore, Vilda/DDS is a promising approach for managing S. mansoni infection, liver fibrosis, and associated disease morbidity.

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.

A Novel Bioswitchable miRNA Mimic Delivery System: Therapeutic Strategies Upgraded from Tetrahedral Framework Nucleic Acid System for Fibrotic Disease Treatment and Pyroptosis Pathway Inhibition

There has been considerable interest in gene vectors and their role in regulating cellular activities and treating diseases since the advent of nucleic acid drugs. MicroRNA (miR) therapeutic strategies are research hotspots as they regulate gene expression post-transcriptionally and treat a range of diseases. An original tetrahedral framework nucleic acid (tFNA) analog, a bioswitchable miR inhibitor delivery system (BiRDS) carrying miR inhibitors, is previously established; however, it remains unknown whether BiRDS can be equipped with miR mimics. Taking advantage of the transport capacity of tetrahedral framework nucleic acid (tFNA) and upgrading it further, the treatment outcomes of a traditional tFNA and BiRDS at different concentrations on TGF-β- and bleomycin-induced fibrosis simultaneously in vitro and in vivo are compared. An upgraded traditional tFNA is designed by successfully synthesizing a novel BiRDS, carrying a miR mimic, miR-27a, for treating skin fibrosis and inhibiting the pyroptosis pathway, which exhibits stability and biocompatibility. BiRDS has three times higher efficiency in delivering miRNAs than the conventional tFNA with sticky ends. Moreover, BiRDS is more potent against fibrosis and pyroptosis-related diseases than tFNAs. These findings indicate that the BiRDS can be applied as a drug delivery system for disease treatment.

Pathogenetic rationale for prescribing menopausal hormone therapy for systemic sclerosis

Systemic scleroderma (SS) is characterized by dysregulation of the innate and adaptive immune systems, vasculopathy, and generalized fibrosis. As with most autoimmune diseases, women predominate among patients, who get sick 3–14 times more often than men. It is assumed that gender differences and modulation of sex hormones are essential in the pathogenesis of SS. Estrogens are able to influence the immune response, have a vasodilating effect and stimulate the synthesis of collagen in the skin. The development of SS leads to a significant decrease in the quality of life, psychological disorders associated with changes in appearance, as well as the need for lifelong medication with the frequent development of side effects. Age-related estrogen deficiency associated with the onset of menopause is accompanied by a decrease in the quality of life and, in some cases, a change in the clinical manifestations of somatic diseases. This review considers the impact of menopause and menopausal hormone therapy (MHT) on the course and clinical manifestations of systemic scleroderma. It is noted that SS in some cases is accompanied by an early onset of menopause. The use of MHT is not associated with the progression of cutaneous fibrosis, and may also improve the vascular manifestations of SS.

Elevated Alpha 1(I) to Alpha 2(I) Collagen Ratio in Dermal Fibroblasts Possibly Contributes to Fibrosis in Systemic Sclerosis

Systemic sclerosis (SSc) is characterized by excessive collagen deposition in the skin and internal organs. Activated fibroblasts are the key effector cells for the overproduction of type I collagen, which comprises the α1(I) and α2(I) chains encoded by COL1A1 and COL1A2, respectively. In this study, we examined the expression patterns of α1(I) and α2(I) collagen in SSc fibroblasts, as well as their co-regulation with each other. The relative expression ratio of COL1A1 to COL1A2 in SSc fibroblasts was significantly higher than that in control fibroblasts. The same result was observed for type I collagen protein levels, indicating that α2(I) collagen is more elevated than α2(I) collagen. Inhibition or overexpression of α1(I) collagen in control fibroblasts affected the α2(I) collagen levels, suggesting that α1(I) collagen might act as an upstream regulator of α2(I) collagen. The local injection of COL1A1 small interfering RNA in a bleomycin-induced SSc mouse model was found to attenuate skin fibrosis. Overall, our data indicate that α2(I) collagen is a potent regulator of type I collagen in SSc; further investigations of the overall regulatory mechanisms of type I collagen may help understand the aberrant collagen metabolism in SSc.

Tetrahedral Framework Nucleic Acids Inhibit Skin Fibrosis via the Pyroptosis Pathway

The skin is the first line of defense for the human body and is vulnerable to injury. Various topical or systemic diseases facilitate skin inflammation, and when the intensity or duration of skin injury exceeds the ability of tissue repair, fibrosis, an outcome of a dysregulated tissue-repair response, begins to dominate the repair process. However, existing methods for reducing skin fibrosis are insufficient and cause side effects, highlighting the need for drugs that effectively inhibit skin fibrosis and reduce immunogenicity, inflammation, apoptosis, and pyroptosis. Tetrahedral framework nucleic acids (tFNAs) are DNA nanomaterials that have a unique spatial structure, demonstrate excellent biosecurity, and promote anti-inflammatory, antioxidative, antifibrotic, angiogenic, and skin-wound-healing activities with almost no toxicity. Here, we explored the potential of tFNAs in skin fibrosis therapy in vitro and in vivo. After incubating cells or injecting mice with profibrogenic molecules and tFNAs, we found that the tFNAs inhibited the epithelial-mesenchymal transition, reduced inflammatory factor levels, decreased skin collagen content, and inhibited the pyroptosis pathway. These findings suggest the potential of tFNAs in treating pyroptosis-related diseases.

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.

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.

Targeting Sirtuin1 to treat aging-related tissue fibrosis: From prevention to therapy

Fibrosis, which is characterized by excessive extracellular matrix (ECM) deposition, is a wound-healing response to organ injury and may promote cancer and failure in various organs, such as the heart, liver, lung, and kidney. Aging associated with oxidative stress and inflammation exacerbates cellular dysfunction, tissue failure, and body function disorders, all of which are closely related to fibrosis. Sirtuin-1 (SIRT1) is a class III histone deacetylase that regulates growth, transcription, aging, and metabolism in various organs. This protein is downregulated in organ injury and fibrosis associated with aging. Its expression and distribution change with age in different organs and play critical roles in tissue oxidative stress and inflammation. This review first described the background on fibrosis and regulatory functions of SIRT1. Second, we summarized the relationships of SIRT1 with other proteins and its protective action during fibrosis in the heart, liver, lung and kidney. Third, the activation of SIRT1 in therapies of tissue fibrosis, especially in liver fibrosis and aging-related tissue injury, was analyzed. In conclusion, SIRT1 targeting may be a new therapeutic strategy in fibrosis.

cRel expression regulates distinct transcriptional and functional profiles driving fibroblast matrix production in systemic sclerosis

OBJECTIVES

NF-κB regulates genes that control inflammation, cell proliferation, differentiation and survival. Dysregulated NF-κB signalling alters normal skin physiology and deletion of cRel limits bleomycin-induced skin fibrosis. This study investigates the role of cRel in modulating fibroblast phenotype in the context of SSc.

METHODS

Fibrosis was assessed histologically in mice challenged with bleomycin to induce lung or skin fibrosis. RNA sequencing and pathway analysis was performed on wild type and Rel-/- murine lung and dermal fibroblasts. Functional assays examined fibroblast proliferation, migration and matrix production. cRel overexpression was investigated in human dermal fibroblasts. cRel immunostaining was performed on lung and skin tissue sections from SSc patients and non-fibrotic controls.

RESULTS

cRel expression was elevated in murine lung and skin fibrosis models. Rel-/- mice were protected from developing pulmonary fibrosis. Soluble collagen production was significantly decreased in fibroblasts lacking cRel while proliferation and migration of these cells was significantly increased. cRel regulates genes involved in extracellular structure and matrix organization. Positive cRel staining was observed in fibroblasts in human SSc skin and lung tissue. Overexpression of constitutively active cRel in human dermal fibroblasts increased expression of matrix genes. An NF-κB gene signature was identified in diffuse SSc skin and nuclear cRel expression was elevated in SSc skin fibroblasts.

CONCLUSION

cRel regulates a pro-fibrogenic transcriptional programme in fibroblasts that may contribute to disease pathology. Targeting cRel signalling in fibroblasts of SSc patients could provide a novel therapeutic avenue to limit scar formation in this disease.

Physical plasma therapy accelerates wound re-epithelialisation and enhances extracellular matrix formation in cutaneous skin grafts

Skin grafting is a surgical method of cutaneous reconstruction, which provides volumetric replacement in wounds unable to heal by primary intention. Clinically, full-thickness skin grafts (FTSGs) are placed in aesthetically sensitive and mechanically demanding areas such as the hands, face, and neck. Complete or partial graft failure is the primary complication associated with this surgical procedure. Strategies aimed at improving the rate of skin graft integration will reduce the incidence of graft failure. Cold atmospheric plasma (CAP) is an emerging technology offering innovative clinical applications. The aim of this study was to test the therapeutic potential of CAP to improve wound healing and skin graft integration into the recipient site. In vitro models that mimic wound healing were used to investigate the ability of CAP to enhance cellular migration, a key factor in cutaneous tissue repair. We demonstrated that CAP enhanced the migration of epidermal keratinocytes and dermal fibroblasts. This increased cellular migration was possibly induced by the low dose of reactive oxygen and nitrogen species produced by CAP. Using a mouse model of burn wound reconstructed with a full-thickness skin graft, we showed that wounds treated with CAP healed faster than did control wounds. Immunohistochemical wound analysis showed that CAP treatment enhanced the expression of the dermal-epidermal junction components, which are vital for successful skin graft integration. CAP treatment was characterised by increased levels of Tgfbr1 mRNA and collagen I protein in vivo, suggesting enhanced wound maturity and extracellular matrix deposition. Mechanistically, we show that CAP induced the activation of the canonical SMAD-dependent TGF-β1 pathway in primary human dermal fibroblasts, which may explain the increased collagen I synthesis in vitro. These studies revealed that CAP improved wound repair and skin graft integration via mechanisms involving extracellular matrix formation. CAP offers a novel approach for treating cutaneous wounds and skin grafts. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

CXCL17-mediated downregulation of type I collagen via MMP1 and miR-29 in skin fibroblasts possibly contributes to the fibrosis in systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is characterized by excessive deposition of collagen in the skin and internal organs. Recent studies have shown that chemokine (C-X-C motif) ligands (CXCLs) are involved in the pathogenesis of SSc.

OBJECTIVE

Our aim was to examine the anti-fibrotic potential of CXCL17, a newly discovered chemokine, in cultured skin fibroblasts and in a bleomycin-induced SSc mouse model. Moreover, we examined serum level of CXCL17 in patients with SSc.

METHODS

Type I collagen expression was evaluated in SSc skin and cultured fibroblasts treated with CXCL17 using immunoblotting and quantitative reverse transcription-PCR. Serum CXCL17 levels were determined using enzyme-linked immunosorbent assay in 63 patients with SSc and 17 healthy subjects. A bleomycin-induced SSc mouse model was used to evaluate the effect of CXCL17 on skin fibrosis.

RESULTS

CXCL17 reduced the expression of type I collagen in healthy control fibroblasts. CXCL17 also induced matrix metalloproteinase 1 (MMP1) and miR-29 expression in fibroblasts, indicating that CXCL17 regulates type I collagen expression in part via post-transcriptional mechanisms through MMP1 and miR-29. We found that local injection of CXCL17 attenuated bleomycin-induced skin fibrosis in mice. CXCL17 levels in SSc skin were lower than those in healthy controls, in contrast to the high serum CXCL17 levels in patients with SSc. The low expression of CXCL17 in SSc skin possibly affects type I collagen accumulation in this disease.

CONCLUSION

Our data indicate that understanding CXCL17 signaling may lead to a better therapeutic approach for SSc.

Adipose tissue-derived regenerative cells improve implantation of fertilized eggs in thin endometrium

Aim: Embryo implantation and subsequent pregnancy depends on endometrial thickness. To investigate potential fertility strategies for women with thin endometrium, we explored the efficacy of adipose tissue-derived regenerative cells (ADRCs) on thin endometrium and embryo implantation in a mouse model. Materials & methods: ADRCs isolated from mouse subcutaneous fat were characterized by flow cytometry. Endometrium thickness, endometrial fibrosis, embryo implantation and angiogenesis factors were evaluated in uterine cavities of ethanol-induced thin endometrium mice with ADRC transplantation. Results: ADRCs included adipose-derived stem cells and some blood vessel component cells. ADRCs improved endometrial thickness, endometrial fibrosis and embryo implantation and augmented vascular endothelial growth factor expression in the mouse uterine. Conclusion: ADRCs may be a useful therapeutic strategy to improve fertility of women with thin endometrium.

A Flowable Placental Formulation Prevents Bleomycin-Induced Dermal Fibrosis in Aged Mice

Fibrosis, the thickening and scarring of injured connective tissue, leads to a loss of organ function. Multiple cell types, including T-cells, macrophages, fibrocytes, and fibroblasts/myofibroblasts contribute to scar formation via secretion of inflammatory factors. This event results in an increase in oxidative stress and deposition of excessive extracellular matrix (ECM), characteristic of fibrosis. Further, aging is known to predispose connective tissue to fibrosis due to reduced tissue regeneration. In this study, we investigated the anti-fibrotic activity of a flowable placental formulation (FPF) using a bleomycin-induced dermal fibrosis model in aged mice. FPF consisted of placental amnion/chorion- and umbilical tissue-derived ECM and cells. The mice were injected with either FPF or PBS, followed by multiple doses of bleomycin. Histological assessment of FPF-treated skin samples revealed reduced dermal fibrosis, inflammation, and TGF-β signaling compared to the control group. Quantitative RT-PCR and Next Generation Sequencing analysis of miRNAs further confirmed anti-fibrotic changes in the FPF-treated group at both the gene and transcriptional levels. The observed modulation in miRNAs was associated with inflammation, TGF-β signaling, fibroblast proliferation, epithelial-mesenchymal transition and ECM deposition. These results demonstrate the potential of FPF in preventing fibrosis and may be of therapeutic benefit for those at higher risk of fibrosis due to wounds, aging, exposure to radiation and genetic predisposition.

Nrf2 in keratinocytes protects against skin fibrosis via regulating epidermal lesion and inflammatory response

Nuclear factor-E2-related factor 2 (Nrf2) is a master transcription factor in antioxidant response, protecting against oxidative damage and various diseases. Previous studies suggest that Nrf2 is suppressed in fibrotic skin and Nrf2 agonists represent a therapeutic strategy, which is mainly attributed to Nrf2 function in fibroblasts. However, constitutive activation of Nrf2 may endow cells with proliferation and survival advantage, facilitating skin tumorigenesis. Non-invasive and mild modulation of Nrf2 via topical application may be helpful. Keratinocytes, which are essential for epidermal formation and function maintenance, have been shown to modulate differentiation of fibroblasts in different stages of fibrosis. In this respect, the role of Nrf2 in keratinocytes in skin fibrosis remains elusive. In the present study, bleomycin (BLM)-induced skin fibrosis model was applied to keratinocyte-specific Nrf2 knockout (Nrf2(K)-KO) mice generated with Keratin 14-Cre/loxp system. BLM treatment significantly suppressed Nrf2 expression in the epidermis. Nrf2 deficiency in keratinocytes exacerbated BLM-induced skin fibrosis according to dermal thickness, and immunostaining of collagen and α-SMA. One-dose BLM treatment led to the emergence of apoptotic cells in the epidermis and an elevated number of macrophages and neutrophils in the dermis, which was aggravated by Nrf2 deficiency, as indicated by TUNEL staining, and expression of F4/80 and Ly6G. In line with in vivo evidence, NRF2 silencing in HaCaT cells significantly decreased cell survival rate in response to BLM due to suppressed expression of antioxidative genes and increased intracellular levels of reactive oxygen species (ROS). The mRNA levels of chemokines and cytokines that are capable of recruiting macrophages and neutrophils, including Mcp-1, Il-6 and Il-8, were increased by Nrf2 deficiency in primary mouse keratinocytes. Moreover, bardoxolone methyl (CDDO-Me), a potent Nrf2 activator, ameliorated BLM-induced skin fibrosis after topical administration. These findings indicate that Nrf2 in keratinocytes protects against skin fibrosis via regulating cell resistance to apoptosis and expression of cytokines and chemokines. The restoration of Nrf2 through topical application might be a potential pharmacologic approach to combat skin fibrosis.

Experimental Mouse Model of Bleomycin-Induced Skin Fibrosis

Systemic sclerosis (SSc) refers to an autoimmune disease, which is manifested by inflammation, vasculopathy, and fibrosis of the skin and internal organs. There are a number of different animal models recapitulating specific aspects of SSc. The experimental mouse model of bleomycin-induced skin fibrosis is commonly used to study the pathogenesis observed in SSc. In this model, repetitive intradermal injections of the cytotoxic agent bleomycin trigger progressive skin thickening, associated with excessive accumulation of collagen, infiltration of immune cells, and formation of α-smooth muscle actin (α-SMA)-positive myofibroblasts. In this article, we provide a detailed protocol for the induction of skin fibrosis in experimental mice by bleomycin. Moreover, we describe procedures for processing and analyzing affected skin tissue, provide troubleshooting, highlight advantages and limitations of the presented model, and critically discuss representative results. © 2019 by John Wiley & Sons, Inc. Basic Protocol 1: Intradermal bleomycin injections to induce skin fibrosis in mice Support Protocol: Mouse tissue collection for fibrosis evaluation and for other molecular assays Basic Protocol 2: Evaluation of mouse skin thickness using Masson's trichrome staining Basic Protocol 3: Measurement of hydroxyproline content in skin tissue using a colorimetric assay Basic Protocol 4: Evaluation of myofibroblasts in mouse skin by immunohistochemistry.

Estrogens Counteract the Profibrotic Effects of TGF-β and their Inhibition Exacerbates Experimental Dermal Fibrosis

Systemic sclerosis primarily affects women. This sex bias raises the question on the role female hormones could play in the development of fibrosis, which is largely unknown. Our aim was to evaluate the effects of estrogens in the development of experimental dermal fibrosis, in the mouse models of bleomycin-induced dermal fibrosis and tight skin (Tsk-1) mice, and on the activation of dermal fibroblasts by transforming growth factor-β (TGF-β). Estrogen inhibition, obtained through gene inactivation for the estrogen receptor-αknockout or treatment with tamoxifen, exacerbated skin fibrosis in the bleomycin model and in the Tsk-1 mice. In the dermal fibroblasts, treatment with 17-β-estradiol significantly decreased the stimulatory effects of TGF-β on collagen synthesis and myofibroblast differentiation, decreased the activation of canonical TGF-β signaling, and markedly reduced the expression of the TGF-β target genes. Tamoxifen reversed the inhibitory effects of estrogens by restoring Smad2/3 phosphorylation and TGF-β-induced collagen synthesis. Our results demonstrate a beneficial effect of estrogens in dermal fibrosis. Estrogens reduce the TGF-β-dependent activation of dermal fibroblasts, and estrogen inhibition leads to a more severe experimental dermal fibrosis. These findings are consistent with the prominent development of systemic sclerosis in postmenopausal women and the greater severity of the disease in men.

Antifibrotic effects of 2-carba cyclic phosphatidic acid (2ccPA) in systemic sclerosis: contribution to the novel treatment

Background

Cyclic phosphatidic acid (cPA) has an inhibitory effect on the autotaxin (ATX)/lysophosphatidic acid (LPA) axis, which has been implicated to play an important role in the progression of fibrosis in systemic sclerosis (SSc). The purpose of this study is to assess the antifibrotic activity of cPA for the treatment of SSc using SSc skin fibroblasts and an animal model of bleomycin-induced skin fibrosis.

Methods

We used a chemically stable derivative of cPA (2ccPA). First, we investigated the effect of 2ccPA on extracellular matrix (ECM) expression in skin fibroblasts. Next, the effect of 2ccPA on the intracellular cAMP levels was determined to investigate the mechanisms of the antifibrotic activity of 2ccPA. Finally, we administered 2ccPA to bleomycin-induced SSc model mice to evaluate whether 2ccPA prevented the progression of skin fibrosis.

Results

2ccPA decreased ECM expression in SSc skin fibroblasts and TGF-β1-treated healthy skin fibroblasts without LPA stimulation. 2ccPA increased the intracellular cAMP levels in skin fibroblasts, suggesting that the antifibrotic effect of 2ccPA was the consequence of the increase in the intracellular cAMP levels. Administration of 2ccPA also ameliorated the progression of bleomycin-induced skin fibrosis in mice.

Conclusions

Our data indicated that 2ccPA had inhibitory effects on the progression of skin fibrosis by abrogating ECM production from activated skin fibroblasts. These cells were repressed, at least in part, by increased intracellular cAMP levels. 2ccPA may be able to be used to treat fibrotic lesions in SSc.

Non-invasive bioluminescence imaging as a standardized assessment measure in mouse models of dermal inflammation

BACKGROUND

Myeloperoxidase is used as a marker and diagnostic tool for inflammatory processes. Hypochlorous acid produced by myeloperoxidase oxidizes luminol to produce light. By injecting luminol into experimental animals, inflammatory processes can be tracked in real-time by bioluminescence imaging (BLI).

OBJECTIVE

We aimed to establish BLI as a standardized assessment measure in three mouse models of dermal inflammation.

METHODS

Oxazolone-induced delayed-type-hypersensitivity (DTH) (acute), a model for dermatitis, imiquimod (IMQ) (sub-chronic) model for psoriasis and the (chronic) bleomycin model for scleroderma were used. In the first two models, dexamethasone and clobetasol, respectively, were used as reference compounds. In all cases, classical readouts such as dermal swelling, severity scores and histological analyses were compared with in- vivo bioluminescence.

RESULTS

In DTH, bioluminescence peaked earlier than ear swelling, reflecting early cell infiltration. Dexamethasone blocked both ear swelling and bioluminescence. In the IMQ model, bioluminescence closely reflected the psoriasis scores and histology and revealed a relapse-remitting course of the disease. Clobetasol partially decreased the disease severity. After stopping IMQ and clobetasol treatment, BLI adopted a rhythmic pattern during resolution. Bleomycin induced an increase in bioluminescence and in collagen thickness. BLI revealed a time-course of the effects of bleomycin that was not reflected by histology alone.

CONCLUSION

For drug discovery and translational purposes, it is important that disease processes be tracked in vivo and possibly over a long period. We conclude that BLI is a valuable and reliable method for in-vivo measurement of dermal inflammation and potentially for inflammation resolution.

NF‑κB is a key modulator in the signaling pathway of Borrelia burgdorferi BmpA‑induced inflammatory chemokines in murine microglia BV2 cells

Lyme disease, caused by the bacterial spirochete Borrelia burgdorferi, is a tick‑borne zoonosis. Lyme neuroborreliosis is a principal manifestation of Lyme disease and its pathogenesis remains incompletely understood. Recent studies have demonstrated that Borrelia burgdorferi lipoproteins caused similar inflammatory effects as exhibited in Lyme neuroborreliosis. Basic membrane protein A (BmpA) is one of the dominant lipoproteins in the Borrelia burgdorferi membrane. In addition, nuclear factor κ‑B (NF‑κB) modulates the regulation of gene transcription associated with immunity and inflammation; however, in unstimulated cells, NF‑κB is combined with the inhibitor of NF‑κB (IκB‑β). Therefore, it was hypothesized that NF‑κB may be associated with BmpA‑induced inflammation and the occurrence of Lyme neuroborreliosis. Therefore, the aim of the present study was to investigate the role that NF‑κB serves in the signaling pathway of rBmpA‑induced inflammatory chemokines. The present study measured the expression levels of NF‑κB, IκB‑β and inflammatory chemokines following recombinant BmpA (rBmpA) stimulation of murine microglia BV2 cells. Following stimulation with rBmpA, concentrations of pro‑inflammatory cytokines including C‑X‑C motif chemokine 2, C‑C motif chemokine (CCL) 5 and CCL22 were determined by ELISA analysis. Reverse transcription‑quantitative polymerase chain reaction and western blotting were used to detect the expression levels of NF‑κB p65 and IκB‑β. The data demonstrated that concentrations of these chemokines in cell supernatants increased significantly following rBmpA stimulation. NF‑κB was overexpressed, but IκB‑β expression was significantly decreased. In conclusion, these results suggested that NF‑κB serves an important stimulatory role in the signaling pathway of rBmpA‑induced inflammatory chemokines in BV2 cells.

Role of adipose tissue in facial aging

Age-dependent modification of the facial subcutaneous white adipose tissue (sWAT) connected with reduction of its volume, modification of collagen content and adhesion between dermal and adipose layers can significantly influence mechanical stability of the skin and cause the development of aging symptoms such as wrinkles. Typical aging appearance in facial skin is at least partly connected with special phenotypical features of facial preadipocytes and mature adipocytes. In this paper, we have discussed the possible roles of local inflammation, compartmental structure of facial sWAT and trans-differentiation processes such as beiging of white adipocytes and adipocyte-myofibroblast transition in facial skin aging.

Activation of STAT3 integrates common profibrotic pathways to promote fibroblast activation and tissue fibrosis

Signal transducer and activator of transcription 3 (STAT3) is phosphorylated by various kinases, several of which have been implicated in aberrant fibroblast activation in fibrotic diseases including systemic sclerosis (SSc). Here we show that profibrotic signals converge on STAT3 and that STAT3 may be an important molecular checkpoint for tissue fibrosis. STAT3 signaling is hyperactivated in SSc in a TGFβ-dependent manner. Expression profiling and functional studies in vitro and in vivo demonstrate that STAT3 activation is mediated by the combined action of JAK, SRC, c-ABL, and JNK kinases. STAT3-deficient fibroblasts are less sensitive to the pro-fibrotic effects of TGFβ. Fibroblast-specific knockout of STAT3, or its pharmacological inhibition, ameliorate skin fibrosis in experimental mouse models. STAT3 thus integrates several profibrotic signals and might be a core mediator of fibrosis. Considering that several STAT3 inhibitors are currently tested in clinical trials, STAT3 might be a candidate for molecular targeted therapies of SSc.

STAT3 is a transcription factor that is activated in fibrotic diseases such as systemic sclerosis. Here the authors show that STAT3 is the converging point for multiple pro-fibrotic signalling pathways, and that its genetic ablation or inhibition ameliorate skin fibrosis in mouse models.

PTP4A1 promotes TGFβ signaling and fibrosis in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of skin and internal organs. Protein tyrosine phosphatases have received little attention in the study of SSc or fibrosis. Here, we show that the tyrosine phosphatase PTP4A1 is highly expressed in fibroblasts from patients with SSc. PTP4A1 and its close homolog PTP4A2 are critical promoters of TGFβ signaling in primary dermal fibroblasts and of bleomycin-induced fibrosis in vivo. PTP4A1 promotes TGFβ signaling in human fibroblasts through enhancement of ERK activity, which stimulates SMAD3 expression and nuclear translocation. Upstream from ERK, we show that PTP4A1 directly interacts with SRC and inhibits SRC basal activation independently of its phosphatase activity. Unexpectedly, PTP4A2 minimally interacts with SRC and does not promote the SRC–ERK–SMAD3 pathway. Thus, in addition to defining PTP4A1 as a molecule of interest for TGFβ-dependent fibrosis, our study provides information regarding the functional specificity of different members of the PTP4A subclass of phosphatases.

Although protein tyrosine kinases are being explored as antifibrotic agents for the treatment of systemic sclerosis, little is known about the function of counteractive protein tyrosine phosphatases in this context. Here, the authors show that PTP4A1 is highly expressed by fibroblasts from patients with systemic sclerosis and promotes TGFβ activity via SRC–ERK–SMAD3 signaling.

Interfacial Adipose Tissue in Systemic Sclerosis

Purpose of Review

This review provides a summary of recent insights into the role of the local white adipose tissue (WAT) in systemic sclerosis.

Recent Findings

Adipocytes located in an interfacial WAT area adjacent to fibrotic lesions have an intermediate phenotype and special properties implicated in fibrotic pathology in systemic sclerosis (SSc). The important role of these cells is recognized in different pathologies, such as wound healing, psoriasis, breast cancer, and prostate cancer. Additionally, both immature and mature adipocytes are involved in the appearance of fibroblast-like cells but exhibit different phenotypes and synthetic properties.

Summary

Adipocytes from interfacial WAT adjacent to the fibrotic area in SSc are phenotypically different from bulk adipocytes and are involved in pathogenesis of SSc. Immature and mature adipocytes from this WAT layer differentiate into various types of fibroblast-like cells, making the local ratio of immature to mature adipocytes in interfacial WAT of particular importance in SSc pathogenesis.

Leflunomide prevents ROS-induced systemic fibrosis in mice

Systemic sclerosis (SSc) is a connective tissue disorder characterized by fibrosis of the skin and inner organs, vasculopathy and immunological abnormalities. Recent insights into the polarization of macrophages in scleroderma and into the implication of STAT6 and KLF4 in this process have prompted us to investigate the effects of the inhibition of STAT6 signaling pathway by leflunomide in mice. SSc was induced in BALB/c mice by daily subcutaneous injections of hypochlorous acid (HOCl) or bleomycin. Mice were treated (or not) every other day, for 4 or 6 weeks, by leflunomide. Skin and lung fibrosis as well as immunological features were studied. Mice exposed to HOCl developed a diffuse cutaneous SSc with pulmonary fibrosis and anti-DNA topoisomerase 1 auto-antibodies. STAT6 pathway was hyperactivated and KLF4 was overexpressed in the skin and the lungs of diseased mice. Their inhibition by leflunomide prevented skin and lung fibrosis. Moreover, the hyperproliferative and pro-oxidative phenotype of skin and lung fibroblasts was reversed by leflunomide. Beneficial immunological effects of leflunomide were associated with decreased activation of CD4+ and CD8+ T cells, B cell activation, decreased auto-antibodies production and restored polarization of macrophages in the spleen. The improvement provided by leflunomide in both mouse models of SSc provides a rationale for the evaluation of this immunomodulating drug in the management of patients affected by this disease.

Animal models of scleroderma: recent progress

PURPOSE OF REVIEW

We discuss recent advances in evaluating and optimizing animal models of systemic sclerosis (SSc). Such models could be of value for illuminating etiopathogenesis using hypothesis-testing experimental approaches, for developing effective disease-modifying therapies, and for uncovering clinically relevant biomarkers.

RECENT FINDINGS

We describe recent advances in previously reported and novel animal models of SSc. The limitations of each animal model and their ability to recapitulate the pathophysiology of recognized molecular subsets of SSc are discussed. We highlight attrition of dermal white adipose tissue as a consistent pathological feature of dermal fibrosis in mouse models, and its relevance to SSc-associated cutaneous fibrosis.

SUMMARY

Several animal models potentially useful for studying SSc pathogenesis have been described. Recent studies highlight particular strengths and weaknesses of selected models in recapitulating distinct features of the human disease. When used in the appropriate experimental setting, and in combination, these models singly and together provide a powerful set of in-vivo tools to define underlying mechanisms of disease and to develop and evaluate effective antifibrotic therapies.

Bone Marrow-Derived Mesenchymal Stem Cells Expressing Thioredoxin 1 Attenuate Bleomycin-Induced Skin Fibrosis and Oxidative Stress in Scleroderma

Systemic sclerosis (SSc) is an autoimmune disorder that affects multiple organs. It is characterized by a thickening of the dermis and connective tissue caused by collagen accumulation, and vascular injuries that induce hypoxia. The present study investigated the therapeutic potential of bone marrow-derived mesenchymal stem cells (BMSCs) expressing thioredoxin 1 (Trx-1) in treating SSc-mediated skin disease after transplantation into a bleomycin-induced murine model. Mice with bleomycin-induced SSc were subcutaneously injected with BMSCs or Trx-1-overexpressing BMSCs and exposed to hypoxic conditions for 48 hours. Two weeks later, skin tissue samples were collected to assess fibrosis, oxidative stress, and angiogenesis by western blotting, ELISA, and histologic and immunofluorescence approaches. In vivo experiments showed that Trx-1-overexpressing BMSCs inhibited hypoxia-induced apoptosis and inhibited fibrosis under hypoxic conditions, possibly by downregulating transforming growth factor-β. Trx-1-overexpressing BMSCs also promoted the formation of tubular-like structures by endothelial progenitor cells, indicating that Trx-1 can promote angiogenesis in bleomycin-induced SSc. These results demonstrate that the transplantation of Trx-1-overexpressing BMSCs restored normal skin tissue in a mouse model of bleomycin-induced SSc, highlighting the therapeutic potential of engineered BMSCs for treating SSc.

Transplanting Human Skin Grafts onto Nude Mice to Model Skin Scars

Hypertrophic scar (HTS) is a common outcome of deep dermal wound healing mainly followed mechanical, chemical, and thermal injuries in the skin. Because of the lack of the most effective prevention and treatment, it is particularly important to establish an ideal dermal animal model for improving the understanding of the pathogenesis and exploring therapeutic approaches of HTS. Compared to other dermal fibrotic animal models in rabbits, red Duroc pigs, guinea pigs, rats, and mice, the approach that uses normal human split-thickness skin grafted onto nude or other immunodeficient mice which develop scars that resemble human HTS offers the advantages of lower cost, easier manipulation, and shorter research period. In this chapter, we will introduce the detailed procedures to create the ideal dermal fibrotic mouse model.

Intradermal Injections of Bleomycin to Model Skin Fibrosis

Systemic sclerosis (scleroderma) is a fibrotic condition characterized by immunologic abnormalities, vascular injury, and increased accumulation of extracellular matrix proteins in the affected organs. Although the etiology of scleroderma has not yet been fully elucidated, a growing body of evidence suggests that extracellular matrix overproduction by activated fibroblasts results from a complex interaction among endothelial cells, immunocytes, and fibroblasts, involving a number of mediators such as cytokines, chemokines, growth factors, and their receptors. For a better understanding of the pathophysiology of scleroderma, animal models are important tools. They reproduce several histological as well as biochemical aspects resembling human scleroderma, and we can learn lots of new findings through animal studies. On the other hand, it must be emphasized that there are no animal models so far exhibiting all the aspects of human scleroderma, and studying animal models cannot answer all the problems of human scleroderma. This paper introduces current concepts of various animal models for scleroderma and discusses their advantages/disadvantages, contribution to our understanding of the pathogenesis, and therapeutic approach for human scleroderma.

Treatment with abatacept prevents experimental dermal fibrosis and induces regression of established inflammation-driven fibrosis

OBJECTIVE

Activated T cells are the main component of the inflammatory skin infiltrates that characterise systemic sclerosis (SSc). Our aim was to investigate the efficacy of abatacept, which tempers T-cell activation, in reducing skin fibrosis in complementary mouse models of SSc.

METHODS

The antifibrotic properties of abatacept were evaluated in the mouse models of bleomycin-induced dermal fibrosis and sclerodermatous chronic graft-versus-host disease, reflecting early and inflammatory stages of SSc. Thereafter, we studied the efficacy of abatacept in tight skin (Tsk-1) mice, an inflammation-independent mouse model of skin fibrosis.

RESULTS

Abatacept efficiently prevented bleomycin-induced skin fibrosis and was also effective in the treatment of established fibrosis. In this model, abatacept decreased total and activated T-cell, B-cell and monocyte infiltration in the lesional skin. Abatacept did not protect CB17-SCID mice from the development of bleomycin-induced dermal fibrosis, which supports that T cells are necessary to drive the antifibrotic effects of abatacept. Upon bleomycin injections, skin interleukin (IL) 6 and IL-10 levels were significantly reduced upon abatacept treatment. Moreover, treatment with abatacept ameliorated fibrosis in the chronic graft-versus-host disease model, but demonstrated no efficacy in Tsk-1 mice. The tolerance of abatacept was excellent in the three mouse models.

CONCLUSIONS

Using complementary models, we demonstrate that inhibition of T-cell activation by abatacept can prevent and induce the regression of inflammation-driven dermal fibrosis. Translation to human disease is now required, and targeting early and inflammatory stages of SSc sounds the most appropriate for positioning abatacept in SSc.

Pan PPAR agonist IVA337 is effective in prevention and treatment of experimental skin fibrosis

BACKGROUND

The pathogenesis of systemic sclerosis (SSc) involves a distinctive triad of autoimmune, vascular and inflammatory alterations resulting in fibrosis. Evidence suggests that peroxisome proliferator-activated receptors (PPARs) play an important role in SSc-related fibrosis and their agonists may become effective therapeutic targets.

OBJECTIVE

To determine the expression of PPARs in human fibrotic skin and investigate the effects of IVA337, a pan PPAR agonist, in in vitro and in vivo models of fibrosis.

METHODS

The antifibrotic effects of IVA337 were studied using a bleomycin-induced mouse model of dermal fibrosis. The in vivo effect of IVA337 on wound closure and inflammation were studied using an excisional model of wound healing.

RESULTS

Low levels of PPARα and PPARγ were detected in the skin of patients with SSc compared with controls. In mice, IVA337 was associated with decreased extracellular matrix (ECM) deposition and reduced expression of phosphorylated SMAD2/3-intracellular effector of transforming growth factor (TGF)-β1. Although the antifibrotic effect of pan PPAR was similar to that of PPARγ agonist alone, a significant downregulation of several markers of inflammation was associated with IVA337. Despite its anti-inflammatory and antifibrotic properties, IVA337 did not interfere with wound closure. In vitro effects of IVA337 included attenuation of transcription of ECM genes and alteration of canonical and non-canonical TGF-β signalling pathways.

CONCLUSIONS

These findings indicate that simultaneous activation of all three PPAR isoforms exerts a dampening effect on inflammation and fibrosis, making IVA337 a potentially effective therapeutic candidate in the treatment of fibrotic diseases including SSc.

Skin fibrosis: Models and mechanisms

Matrix synthesis, deposition and remodeling are complex biological processes that are critical in development, maintenance of tissue homeostasis and repair of injured tissues. Disturbances in the regulation of these processes can result in severe pathological conditions which are associated with tissue fibrosis as e.g. in Scleroderma, cutaneous Graft-versus-Host-Disease, excessive scarring after trauma or carcinogenesis. Therefore, finding efficient treatments to limit skin fibrosis is of major clinical importance. However the pathogenesis underlying the development of tissue fibrosis is still not entirely resolved. In recent years progress has been made unraveling the complex cellular and molecular mechanisms that determine fibrosis. Here we provide an overview of established and more recently developed mouse models that can be used to investigate the mechanisms of skin fibrosis and to test potential therapeutic approaches.

Updates on animal models of systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology that is characterized by fibrosis of the skin and several internal organs, vasculopathy, inflammation and autoimmunity. Animal models have improved our understanding of the pathogenesis of SSc. Many inducible and genetic animal models of SSc have been developed and characterized in the last years. All of these models have different strengths and limitations and mimic different aspects of the pathogenesis of SSc. The purpose of this review is to summarize the characteristics of the various animal models of SSc and to provide an outline of how to use these models to study certain aspects in the pathogenesis of SSc and to test the effects of potential therapeutic approaches.