Skin serves as the first-order protective barrier against the environment and any significant disruptions in skin integrity must be promptly restored. Despite significant advances in therapeutic strategies, effective management of large chronic skin wounds remains a clinical challenge. Dermal fibroblasts are the primary cell type responsible for remodeling the extracellular matrix (ECM) in wound healing. Here, we investigated whether ECM derived from exogenous fibroblasts, in combination with keratinocytes, promoted scarless cutaneous wound healing. To overcome the limited lifespan of primary dermal fibroblasts, we established reversibly immortalized mouse dermal fibroblasts (imDFs), which were non-tumorigenic, expressed dermal fibroblast markers, and were responsive to TGF-β1 stimulation. The decellularized ECM prepared from both imDFs and primary dermal fibroblasts shared similar expression profiles of extracellular matrix proteins and promoted the proliferation of keratinocyte (iKera) cells. The imDFs-derived ECM solicited no local immune response. While the ECM and to a lesser extent imDFs enhanced skin wound healing with excessive fibrosis, a combination of imDFs-derived ECM and iKera cells effectively promoted the re-epithelization and scarless healing of full-thickness skin wounds. These findings strongly suggest that dermal fibroblast-derived ECM, not fibroblasts themselves, may synergize with keratinocytes in regulating scarless healing and re-epithelialization of skin wounds. Given its low immunogenic nature, imDFs-derived ECM should be a valuable resource of skin-specific biomaterial for wound healing and skin tissue engineering.

Systemic Sclerosis (SSc) is a systemic autoimmune disease of unknown etiology characterized by the development of frequently progressive cutaneous and internal organ fibrosis accompanied by severe vascular alterations. The pathogenesis of SSc is highly complex and, despite extensive investigation, has not been fully elucidated. Numerous studies have suggested that unknown etiologic factors cause multiple alterations in genetically receptive hosts, leading to SSc development and progression. These events may be functionally and pathologically interconnected and include: 1) Structural and functional microvascular and endothelial cell abnormalities; 2) Severe oxidative stress and high reactive oxygen species (3); Frequently progressive cutaneous and visceral fibrosis; 4) Transdifferentiation of various cell types into activated myofibroblasts, the cells ultimately responsible for the fibrotic process; 5) Establishment of a chronic inflammatory process in various affected tissues; 6) Release of cytokines, chemokines, and growth factors from the inflammatory cells; 7) Abnormalities in humoral and cellular immunity with the production of specific autoantibodies; and 8) Epigenetic alterations including changes in multiple non-coding RNAs. These events manifest with different levels of intensity in the affected organs and display remarkable individual variability, resulting in a wide heterogeneity in the extent and severity of clinical manifestations. Here, we will review some of the recent studies related to SSc pathogenesis.

Systemic sclerosis (SSc) remains a challenging and enigmatic systemic autoimmune disease, owing to its complex pathogenesis, clinical and molecular heterogeneity, and the lack of effective disease-modifying treatments. Despite a century of research in SSc, the interconnections among microvascular dysfunction, autoimmune phenomena and tissue fibrosis in SSc remain unclear. The absence of validated biomarkers and reliable animal models complicates diagnosis and treatment, contributing to high morbidity and mortality. Advances in the past 5 years, such as single-cell RNA sequencing, next-generation sequencing, spatial biology, transcriptomics, genomics, proteomics, metabolomics, microbiome profiling and artificial intelligence, offer new avenues for identifying the early pathogenetic events that, once treated, could change the clinical history of SSc. Collaborative global efforts to integrate these approaches are crucial to developing a comprehensive, mechanistic understanding and enabling personalized therapies. Challenges include disease classification, clinical heterogeneity and the establishment of robust biomarkers for disease activity and progression. Innovative clinical trial designs and patient-centred approaches are essential for developing effective treatments. Emerging therapies, including cell-based and fibroblast-targeting treatments, show promise. Global cooperation, standardized protocols and interdisciplinary research are vital for advancing SSc research and improving patient outcomes. The integration of advanced research techniques holds the potential for important breakthroughs in the diagnosis, treatment and care of individuals with SSc.

Cardiac fibrosis, a key contributor to ventricular pathologic remodeling and heart failure, currently lacks effective therapeutic approaches.

Small extracellular vesicles from young healthy human plasma (Young-sEVs) were characterized via protein marker, transmission electron microscopy, and nanoparticle tracking analysis, then applied in cellular models and mouse models of cardiac fibrosis. Western blotting and qRT-PCR were used to identify protective signaling pathways in cardiac fibroblasts (CFs).

Young-sEVs significantly inhibited cardiac fibrosis and subsequent cardiac dysfunction post-myocardial infarction (MI) in mice. The main findings included that echocardiographic assessments four weeks post-MI indicated that Young-sEVs improved left ventricular ejection fraction (LVEF) and fractional shortening (LVFS), and reduced left ventricular internal diameter in diastole (LVIDd) and systole (LVIDs). Treatment with Young-sEVs also decreased Masson-positive fibroblast areas and collagen synthesis in cardiac tissue. However, sEVs from the old control group did not achieve the above effect. Consistent with in vivo results, Young-sEVs could also inhibit the proliferation, migration, and collagen synthesis of CFs in the TGF-β1-induced cellular fibrosis model. High-throughput microRNA (miRNA) sequencing and qRT-PCR analysis revealed that miR-664a-3p was abundant in Young-sEVs. The high expression of miR-664a-3p significantly inhibited the proliferation, migration, and collagen synthesis of TGF-β1-induced CFs. However, suppressing the expression of miR-664a-3p in Young-sEVs eliminated their therapeutic effect on cardiac fibrosis in mice. Further studies confirmed SMAD4 as a direct downstream target of miR-664a-3p, whose overexpression could reverse the anti-fibrotic effects of miR-664a-3p.

In summary, these findings firstly revealed that Young-sEVs could directly bind to the 3'-untranslated region of SMAD4 mRNA through miR-664a-3p, thereby inhibiting the TGF-β/SMAD4 signaling pathway to protect heart from fibrosis and improve cardiac function. Considering the ease of obtaining plasma-derived sEVs, our study offers a promising therapeutic strategy for heart failure, with the potential for rapid clinical translation in the near future.

Acute kidney injury (AKI) is a common health problem that leads to high morbidity and potential mortality. The failure of conventional treatments to improve forms of this condition highlights the need for innovative and effective treatment approaches. Regenerative therapies with Renal Progenitor Cells (RPCs) have been proposed as a promising new strategy. A growing body of evidence suggests that progenitor cells differentiated from different sources, including human embryonic stem cells (hESCs), can effectively treat AKI.

Here, we describe a method for generating RPCs and directed human Embryoid Bodies (EBs) towards CD133+CD24+ renal progenitor cells and evaluate their functional activity in alleviating AKI.

The obtained results show that hESCs-derived CD133+CD24+ RPCs can engraft into damaged renal tubules and restore renal function and structure in mice with gentamicin-induced kidney injury, and significantly decrease blood urea nitrogen levels, suppress oxidative stress and inflammation, and attenuate histopathological disturbances, including tubular necrosis, tubular dilation, urinary casts, and interstitial fibrosis.

The results suggest that RPCs have a promising regenerative potential in improving renal disease and can lay the foundation for future cell therapy and disease modeling.

Systemic sclerosis (SSc) is a rare and highly heterogeneous chronic autoimmune disease characterized by multi-organ and tissue fibrosis, often accompanied by a poor prognosis and high mortality rates. The primary pathogenic mechanisms of SSc are considered to involve tissue fibrosis, autoimmune dysfunction, and microvascular abnormalities. Recent studies have shed light on the gut microbiota (GM) and metabolites in SSc patients, revealing their association with gastrointestinal symptoms and disease phenotypes. However, further elucidation is needed on the specific mechanisms underlying the interactions between GM, metabolites, and the immune system and their roles in the pathogenesis of SSc. This review outlines the characteristics of GM and metabolites in SSc patients, exploring their interrelationships and analyzing their correlations with the clinical phenotypes of SSc. The findings indicate that while the α-diversity of GM in SSc patients resembles that of healthy individuals, notable differences exist in the β-diversity and the abundance of specific bacterial genera, which are closely linked to gastrointestinal symptoms. Moreover, alterations in the levels of amino acids and lipid metabolites in SSc patients are prominently observed and significantly associated with clinical phenotypes. Furthermore, this review delves into the potential immunopathological mechanisms of GM and metabolites in SSc, emphasizing the critical role of interactions between GM, metabolites, and the immune system in comprehending the immunopathological processes of SSc. These insights may offer new scientific evidence for the development of future treatment strategies.

Cardiac fibrosis is characterized by the over-proliferation, over-transdifferentiation and over-deposition of extracellular matrix (ECM) of cardiac fibroblasts (CFs). Cardiac sympathetic activation is one of the leading causes of myocardial fibrosis. Meanwhile, cardiac fibrosis is often together with cardiac inflammation, which accelerates fibrosis by mediating inflammatory cytokines secretion. Recently, the Janus kinase/signal transducer and activator of transcription (JAK/STAT3) signaling pathway has been confirmed by its vital role during the progression of cardiac fibrosis. Thus, JAK/STAT3 signaling pathway is thought to be a potential therapeutic target for cardiac fibrosis. Baricitinib (BR), a novel JAK1/2 inhibitor, has been reported excellent effects of anti-fibrosis in multiple fibrotic diseases. However, little is known about whether and how BR ameliorates cardiac fibrosis caused by chronic sympathetic activation. Isoproterenol (ISO), a β-Adrenergic receptor (β-AR) nonselective agonist, was used to modulate chronic sympathetic activation in mice. As expected, our results proved that BR ameliorated ISO-induced cardiac dysfunction. Meanwhile, BR attenuated ISO-induced cardiac fibrosis and cardiac inflammation in mice. Moreover, BR also inhibited ISO-induced cardiac fibroblasts activation and macrophages pro-inflammatory secretion. As for mechanism studies, BR reduced ISO-induced cardiac fibroblasts by JAK2/STAT3 and PI3K/Akt signaling, while reduced ISO-induced macrophages pro-inflammatory secretion by JAK1/STAT3 and NF-κB signaling. In summary, BR alleviates cardiac fibrosis and inflammation caused by chronic sympathetic activation. The underlying mechanism involves BR-mediated suppression of JAK1/2/STAT3, PI3K/Akt and NF-κB signaling.

Fibrosis is not a disease but rather an outcome of the pathological tissue repair response. Many myofibroblasts are activated which lead to the excessive accumulation of extracellular matrix components such as collagen and fibronectin with fibrosis. A variety of organs, including kidney, liver, lung, heart and skin, can undergo fibrosis under the stimulation of exogenous or endogenous pathogenic factors. The orphan nuclear receptor 4 group A1 (NR4A1) and nuclear receptor 4 group A2（NR4A2）are belong to the nuclear receptor subfamily and inhibit the occurrence and development of fibrosis. NR4A1 is an inhibitory factor of TGF-β signaling transduction. Overexpression of NR4A1 in fibroblasts can reduce TGF-β induced collagen deposition and fibrosis related gene expression. Here, we summarize the current research progress on the NR4A1/2 and fibrosis, providing reference for the treatment of fibrosis.

Scar tissue formation following skin wound healing is a challenging public health problem. Skin regeneration and preventing the formation of scar tissue by currently available commercial products are largely ineffective. This study aimed to test the efficacy of a novel topical metformin lotion (ML) in inhibiting scar tissue formation during skin wound healing in rats and to determine the mechanisms of action involved. A 6% ML was prepared in our laboratory. A skin wound healing model in rats was used. The wounded rats were divided into two groups and treated daily for 10 days as follows: Group 1 received a daily application of 50 mg of control lotion, or 0% ML (totaling 100 mg of lotion per rat), and Group 2 received a daily application of 50 mg of 6% ML (totaling 100 mg of 6% ML per rat). Blood samples from the heart of each rat were analyzed for inflammatory markers, HMGB1 and IL-1β, using ELISA, and immunological and histological analyses were performed on skin tissue sections. ML decreased levels of inflammatory markers HMGB1 and IL-1β in the serum of rats and inhibited the release of HMGB1 from cell nuclei into the skin tissue matrix. Additionally, ML demonstrated anti-fibrotic properties by enhancing AMPK activity, decreasing the expression of TGF-β1, reducing the number of myofibroblasts, decreasing the production of collagen III, and increasing the expression of collagen I. ML promotes the regeneration of high-quality skin during wound healing by reducing scar tissue formation. This effect is mediated through the activation of AMPK, inhibition of TGF-β1, and a decrease in the number of myofibroblasts.

Recessive dystrophic epidermolysis bullosa (RDEB) is a blistering disease caused by mutations in the gene encoding type VII collagen (C7). RDEB is associated with fibrosis, which is responsible for severe complications. The phenotypic variability observed in siblings with RDEB suggests that epigenetic modifications contribute to disease severity. Identifying epigenetic changes may help to uncover molecular mechanisms underlying RDEB pathogenesis and new therapeutic targets.

To investigate histone acetylation in RDEB skin and to explore histone deacetylase inhibitors (HDACi) as therapeutic molecules capable of counteracting fibrosis and disease progression in RDEB mice.

Acetylated histone levels were detected in human skin by immunofluorescence and in RDEB fibroblasts by enzyme-linked immunosorbent assay (ELISA). The effects of givinostat and valproic acid (VPA) on RDEB fibroblast fibrotic behaviour were assessed by a collagen-gel contraction assay, Western blot and immunocytofluorescence for α-smooth muscle actin, and ELISA for released transforming growth factor (TGF)-β1. RNA sequencing was performed in HDACi- and vehicle-treated RDEB fibroblasts. VPA was systemically administered to RDEB mice and effects on overt phenotype were monitored. Fibrosis was investigated in the skin using histological and immunofluorescence analyses. Eye and tongue defects were examined microscopically. Mass spectrometry proteomics was performed on skin protein extracts from VPA-treated RDEB and control mice.

Histone acetylation decreases in RDEB skin and primary fibroblasts. RDEB fibroblasts treated with HDACi lowered fibrotic traits, including contractility, TGF-β1 release and proliferation. VPA administration to RDEB mice mitigated severe manifestations affecting the eyes and paws. These effects were associated with fibrosis inhibition. Proteomic analysis of mouse skin revealed that VPA almost normalized protein sets involved in protein synthesis and immune response, processes linked to the increased susceptibility to cancer and bacterial infections seen in people with RDEB.

Dysregulated histone acetylation contributes to RDEB pathogenesis by facilitating the progression of fibrosis. Repurposing of HDACi could be considered for disease-modifying treatments in RDEB.

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune-driven connective tissue disorder that results in fibrosis of the skin and internal organs such as the lung. Fibroblasts are known as the main effector cells involved in the progression of SSc through the induction of extracellular matrix (ECM) proteins and myofibroblast differentiation. Here, we demonstrate that 4'-(cyclopropylmethyl)-N2-4-pyridinyl-[4,5'-bipyrimidine]-2,2'-diamine (PIK-III), known as class III phosphatidylinositol 3-kinase (PIK3C3/VPS34) inhibitor, exerts potent antifibrotic effects in human dermal fibroblasts (HDFs) by attenuating transforming growth factor-beta 1 (TGF-β1)-induced ECM expression, cell contraction and myofibroblast differentiation. Unexpectedly, neither genetic silencing of PIK3C3 nor other PIK3C3 inhibitors (e.g., SAR405 and Autophinib) were able to mimic PIK-III-mediated antifibrotic effect in dermal fibroblasts, suggesting that PIK-III inhibits fibroblast activation through another signaling pathway. We identified that PIK-III effectively inhibits p38 activation in TGF-β1-stimulated dermal fibroblasts. Finally, PIK-III administration significantly attenuated dermal and lung fibrosis in bleomycin-injured mice.

Interstitial lung diseases (ILD) encompass a wide range of disorders characterized by alveolar inflammation and fibrotic tissue remodeling, marked by significant morbidity and mortality. Systemic sclerosis (SSc), among other connective tissue diseases, is a frequent cause of ILD. Assessment of pulmonary fibrosis is frequently constrained by the delayed manifestations of profibrotic activation of fibroblasts, which results in late macroscopic alterations detectable by standard imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) scans. 68Ga-labeled fibroblast activation protein inhibitors (68Ga-FAPI [fibroblast activation protein inhibitor]) are novel radionuclides used in the selective positron emission tomography/computed tomography (PET/CT) detection of profibrotic fibroblasts, a key player in fibrotic tissue remodeling. Application of 68Ga-FAPI in different target organs undergoing fibrosis, such as lung and heart, highlights its efficacy in detecting ongoing fibrotic processes, since FAPI tracer uptake has been correlated with clinical disease progression markers in SSc-ILD. This feature could enable physicians to detect subclinical fibrotic activity and tailor an individualised therapy plan on a case by case basis. The use of 68Ga-FAPI in ILD and other fibrotic conditions may emerge as a novel tool in future clinical practice for both activity monitoring and treatment optimisation. Other tracers tested in ILD of different etiologies have shown promising results and may in future also be considered for potential application in SSc-ILD.

In the complex panorama of autoimmune diseases, the characterisation of pivotal contributing autoantibodies that are involved in disease progression remains challenging. This study aimed to employ a global antibody profiling strategy to identify novel antibodies and investigate their association with systemic sclerosis (SSc).

We implemented this strategy by conducting immunoprecipitation (IP) following on-bead digestion with the sera of patients with SSc or healthy donors, using antigen pools derived from cell lysates. The enriched antigen-antibody complex was proceeded with mass spectrometry (MS)-based quantitative proteomics and over-represented by bioinformatics analysis. The candidate antibodies were then orthogonally validated in two independent groups of patients with SSc. Mice were immunised with the target antigen, which was subsequently evaluated by histological examination and RNA sequencing.

The IP-MS analysis, followed by validation in patients with SSc, revealed a significant elevation in anti-PRMT5 antibodies among patients with SSc. These antibodies exhibited robust diagnostic accuracy in distinguishing SSc from healthy controls and other autoimmune conditions, including systemic lupus erythematosus and Sjögren's syndrome, with an area under the curve ranging from 0.900 to 0.988. The elevation of anti-PRMT5 antibodies was verified in a subsequent independent group with SSc using an additional method, microarray. Notably, 31.11% of patients with SSc exhibited seropositivity for anti-PRMT5 antibodies. Furthermore, the titres of anti-PRMT5 antibodies demonstrated a correlation with the progression or regression trajectory in SSc. PRMT5 immunisation displayed significant inflammation and fibrosis in both the skin and lungs of mice. This was concomitant with the upregulation of multiple proinflammatory and profibrotic pathways, thereby underscoring a potentially pivotal role of anti-PRMT5 antibodies in SSc.

This study has identified anti-PRMT5 antibodies as a novel biomarker for SSc.

The term 'fibroblast' often serves as a catch-all for a diverse array of mesenchymal cells, including perivascular cells, stromal progenitor cells and bona fide fibroblasts. Although phenotypically similar, these subpopulations are functionally distinct, maintaining tissue integrity and serving as local progenitor reservoirs. In response to tissue injury, these cells undergo a dynamic fibroblast-myofibroblast transition, marked by extracellular matrix secretion and contraction of actomyosin-based stress fibres. Importantly, whereas transient activation into myofibroblasts aids in tissue repair, persistent activation triggers pathological fibrosis. In this Review, we discuss the roles of mechanical cues, such as tissue stiffness and strain, alongside cell signalling pathways and extracellular matrix ligands in modulating myofibroblast activation and survival. We also highlight the role of epigenetic modifications and myofibroblast memory in physiological and pathological processes. Finally, we discuss potential strategies for therapeutically interfering with these factors and the associated signal transduction pathways to improve the outcome of dysregulated healing.

Systemic sclerosis (SSc) is a devastating autoimmune illness with a wide range of clinical symptoms, including vascular abnormalities, inflammation, and persistent and progressive fibrosis. The disease's complicated pathophysiology makes it difficult to develop effective therapies, necessitating research into novel therapeutic options. Molecular hybridization is a strategy that can be used to develop new drugs that act on two or multiple targets and represents an interesting option to be explored for the treatment of complex diseases. We aimed to evaluate the effects of a hybrid mutual prodrug of ibuprofen and acetaminophen (IBPA) in peripheral blood mononuclear cells (PBMC) isolated from SSc patients, and in an in vivo model of SSc induced in BALB/c mice by intradermal injections of hypochlorous acid (HOCl) for 6 weeks. The mice were treated at the same time with daily intraperitoneal injections of IBPA (40 mg/kg). Pulmonary and skin fibrosis as well as immune responses were evaluated. IBPA significantly decreased the release of cytokines in PBMC culture supernatants from SSc patients after stimulation with phytohemagglutinin-M (IL-2, IL-4, IL-6, IL-10, IL-13, IL-17A, TNF and IFN-γ).In HOCl-induced SSc, IBPA treatment prevented dermal and pulmonary fibrosis, in addition to reducing CD4 + T and B cells activation and reversing the M2 polarization of macrophages in spleen cells, and inhibiting IFN-γ secretion in splenocyte cultures. These results show the anti-inflammatory and antifibrotic effects of IBPA in SSc and highlight the therapeutic potential of this mutual prodrug, providing support for future studies.

Corneal neovascularization can impair vision and result in a poor quality of life. The pathogenesis involves a complex interplay of angiogenic factors, notably vascular endothelial growth factor (VEGF). This review provides a comprehensive overview of potential therapies for corneal neovascularization, covering tissue inhibitors of metalloproteinases (TIMPs), transforming growth factor beta (TGF-β) inhibitors, interleukin-1L receptor antagonist (IL-1 Ra), nitric oxide synthase (NOS) isoforms, galectin-3 inhibitors, retinal pigment epithelium-derived factor (PEDF), platelet-derived growth factor (PDGF) receptor inhibitors, and surgical treatments. Conventional treatments include anti-VEGF therapy and laser interventions, while emerging therapies such as immunosuppressive drugs (cyclosporine and rapamycin) have been explored. Losartan and decorin are potential antifibrotic agents that mitigate TGF-β-induced fibrosis. Ocular nanosystems are innovative drug-delivery platforms that facilitate the targeted release of therapeutic agents. Gene therapies, such as small interfering RNA and antisense oligonucleotides, are promising approaches for selectively inhibiting angiogenesis-related gene expression. Aganirsen is efficacious in reducing the corneal neovascularization area without significant adverse effects. These multifaceted approaches underscore the corneal neovascularization management complexity and highlight ideas for enhancing therapeutic outcomes. Furthermore, the importance of combination therapies and the need for further research to develop specific inhibitors while considering their therapeutic efficacy and potential adverse effects are discussed.

Fibrosis is a pathological condition consisting of a delayed deposition and remodeling of the extracellular matrix (ECM) by fibroblasts. This deregulation is mostly triggered by a chronic stimulus mediated by pro-inflammatory cytokines, such as TNF-α and IL-1, which activate fibroblasts. Due to their anti-inflammatory and immunosuppressive potential, dental pulp stem cells (DPSCs) could affect fibrotic processes. This study aims to clarify if DPSCs can affect fibroblast activation and modulate collagen deposition. We set up a transwell co-culture system, where DPSCs were seeded above the monolayer of fibroblasts and stimulated with LPS or a combination of TNF-α and IL-1β and quantified a set of genes involved in inflammasome activation or ECM deposition. Cytokines-stimulated co-cultured fibroblasts, compared to unstimulated ones, showed a significant increase in the expression of IL-1β, IL-6, NAIP, AIM2, CASP1, FN1, and TGF-β genes. At the protein level, IL-1β and IL-6 release as well as FN1 were increased in stimulated, co-cultured fibroblasts. Moreover, we found a significant increase of MMP-9 production, suggesting a role of DPSCs in ECM remodeling. Our data seem to suggest a crosstalk between cultured fibroblasts and DPSCs, which seems to modulate genes involved in inflammasome activation, ECM deposition, wound healing, and fibrosis.

Wounds are one of the most common health issues, and the cost of wound care and healing has continued to increase over the past decade. In recent years, there has been growing interest in developing innovative strategies to enhance the efficacy of wound healing. Tetrahedral framework nucleic acids (tFNAs) have emerged as a promising tool for wound healing applications due to their unique structural and functional properties. Therefore, it is of great significance to summarize the applications of tFNAs for wound healing. This review article provides a comprehensive overview of the potential of tFNAs as a novel therapeutic approach for wound healing. In this review, we discuss the possible mechanisms of tFNAs in wound healing and highlight the role of tFNAs in modulating key processes involved in wound healing, such as cell proliferation and migration, angiogenesis, and tissue regeneration. The targeted delivery and controlled release capabilities of tFNAs offer advantages in terms of localized and sustained delivery of therapeutic agents to the wound site. In addition, the latest research progress on tFNAs in wound healing is systematically introduced. We also discuss the biocompatibility and biosafety of tFNAs, along with their potential applications and future directions for research. Finally, the current challenges and prospects of tFNAs are briefly discussed to promote wider applications.

We investigated multiple signaling pathways activated by CYP11A1-derived vitamin D3 hydroxymetabolites in human skin fibroblasts by assessing the actions of these molecules on their cognate receptors and by investigating the role of CYP27B1 in their biological activities. The actions of 20(OH)D3, 20,23(OH)2D3, 1,20(OH)2D3 and 1,20,23(OH)3D3 were compared to those of classical 1,25(OH)2D3. This was undertaken using wild type (WT) fibroblasts, as well as cells with VDR, RORs, or CYP27B1 genes knocked down with siRNA. Vitamin D3 hydroxymetabolites had an inhibitory effect on the proliferation of WT cells, but this effect was abrogated in cells with silenced VDR or RORs. The collagen expression by WT cells was reduced upon secosteroid treatment. This effect was reversed in cells where VDR or RORs were knocked down where the inhibition of collagen production and the expression of anti-fibrotic genes in response to the hydroxymetabolites was abrogated, along with ablation of their anti-inflammatory action. The knockdown of CYP27B1 did not change the effect of either 20(OH)D3 or 20,23(OH)2D3, indicating that their actions are independent of 1α-hydroxylation. In conclusion, the expression of the VDR and/or RORα/γ receptors in fibroblasts is necessary for the inhibition of both the proliferation and fibrogenic activity of hydroxymetabolites of vitamin D3, while CYP27B1 is not required.

Multipotent mesenchymal stromal cells (MSCs) regulate tissue repair through paracrine activity, with secreted proteins being significant contributors. Human tissue repair commonly results in fibrosis, where fibroblast differentiation into myofibroblasts is a major cellular mechanism. MSCs' paracrine activity can inhibit fibrosis development. We previously demonstrated that the separation of MSC secretome, represented by conditioned medium (CM), into subfractions enriched with extracellular vesicles (EV) or soluble factors (SF) boosts EV and SF antifibrotic effect. This effect is realized through the inhibition of fibroblast-to-myofibroblast differentiation in vitro. To unravel the mechanisms of MSC paracrine effects on fibroblast differentiation, we performed a comparative proteomic analysis of MSC secretome fractions. We found that CM was enriched in NF-κB activators and confirmed via qPCR that CM, but not EV or SF, upregulated NF-κB target genes (COX2, IL6, etc.) in human dermal fibroblasts. Furthermore, we revealed that EV and SF were enriched in TGF-β, Notch, IGF, and Wnt pathway regulators. According to scRNAseq, 11 out of 13 corresponding genes were upregulated in a minor MSC subpopulation disappearing in profibrotic conditions. Thus, protein enrichment of MSC secretome fractions and cellular subpopulation patterns shift the balance in fibroblast-to-myofibroblast differentiation, which should be considered in studies of MSC paracrine effects and the therapeutic use of MSC secretome.

Tendon injuries, while prevalent, present significant challenges regarding their structural and functional restoration. Utilizing alpha-smooth muscle actin (α-SMA)-Ai9-scleraxis (Scx)-green fluorescent protein (GFP) transgenic mice, which exhibit both Scx (a tendon cell marker) and α-SMA (a myofibroblast marker), we explored the effects of metformin (Met) on tendon healing, repair, and its mechanisms of action. Our findings revealed that intraperitoneal (IP) injections of Met, administered before or after injury, as well as both, effectively prevented the release of HMGB1 into the tendon matrix and reduced circulating levels of HMGB1. Additionally, Met treatment increased and activated AMPK and suppressed TGF-β1 levels within the healing tendon. Tendon healing was also improved by blocking the migration of α-SMA+ myofibroblasts, reducing the prevalence of disorganized collagen fibers and collagen type III. It also enhanced the presence of collagen type I. These outcomes highlight Met's anti-fibrotic properties in acutely injured tendons and suggest its potential for repurposing as a therapeutic agent to minimize scar tissue formation in tendon injuries, which could have profound implications in clinical practice.

Phosphodiesterase (PDE) 4 inhibitors have been reported to suppress the progression of dermal fibrosis in patients with systemic sclerosis (SSc); however, the precise mechanisms remain to be elucidated. Therefore, we conducted experiments focusing on the antifibrotic and anti-inflammatory effects of apremilast using dermal fibroblasts derived from patients with SSc and an SSc mouse model. Dermal fibroblasts derived from healthy controls and patients with SSc were incubated with apremilast in the presence or absence of 10 ng/ml transforming growth factor (TGF)-β1 for the measurement of intracellular cAMP levels and evaluation of mRNA and protein expression. A bleomycin-induced dermal fibrosis mouse model was used to evaluate the inhibitory effects of apremilast on the progression of dermal fibrosis. Intracellular cAMP levels were significantly reduced in dermal fibroblasts derived from patients with SSc compared with those derived from healthy controls. Apremilast reduced the mRNA expression of profibrotic markers and the protein expression of type I collagen and Cellular Communication Network Factor 2 (CCN2) in dermal fibroblasts. Additionally, apremilast inhibited the progression of dermal fibrosis in mice, partly by acting on T cells. These results suggest that apremilast may be a potential candidate for treating dermal fibrosis in SSc.

Cellular senescence is induced by many stresses including telomere shortening, DNA damage, oxidative, or metabolic stresses. Senescent cells are stably cell cycle arrested and they secrete many factors including cytokines and chemokines. Accumulation of senescent cells promotes many age-related alterations and diseases. In this study, we investigated the role of the pro-senescent phospholipase A2 receptor 1 (PLA2R1) in regulating some age-related alterations in old mice and in mice subjected to a Western diet, whereas aged wild-type mice displayed a decreased ability to regulate their glycemia during glucose and insulin tolerance tests, aged Pla2r1 knockout (KO) mice efficiently regulated their glycemia and displayed fewer signs of aging. Loss of Pla2r1 was also found protective against the deleterious effects of a Western diet. Moreover, these Pla2r1 KO mice were partially protected from diet-induced senescent cell accumulation, steatosis, and fibrosis. Together these results support that Pla2r1 drives several age-related alterations, especially in the liver, arising during aging or through a Western diet.

This research paper addresses the hypothesis that mast cells (MCs) contribute to the formation of mammary fibrosis. MCs are important immune regulatory and immune modulatory cells that play major roles in the inflammatory process. Since there is no detailed knowledge, this research study aimed to comparatively investigate the presence, localization, and immunophenotypes of MCs in healthy and mastitic mammary tissues. A total of 264 mammary samples were evaluated for the examination of mast cells and fibrosis. The mean mast cell number in both acute and chronic mastitis samples were very significantly higher than the control group P < 0.001). A 7.9-fold increase in the number of mast cells was found when the chronic mastitis group was compared with the control (healthy) group. Immunohistochemistry revealed presence of all three immune phenotypes in control and mastitic mammary samples (tryptase + (MCT), chymase + (MCC) and both chymase and tryptase + (MCTC). The mean MCT, MCC, and MCTC numbers in the chronic mastitis group were found to be significantly higher than the control (P < 0.001 for all three phenotypes) but did not differ significantly between control and acute mastitis samples. When the mean numbers of MCT, MCC, and MCTC in the control group and chronic mastitis group were compared, a 10.5, 7.8, and a 4.1-fold increase was observed, respectively. The amount of connective tissue was strongly increased in tissues with chronic mastitis and a 3.01-fold increase was detected compared to the control group. A statistically significant relation was also found between the amount of fibrosis and the increased number of total MCs (P < 0.001).

Optimal conditions for wound healing require a smooth transition from the early stage of inflammation to proliferation, and during this time alternatively activated (M2) macrophages play a central role. Recently, heat-killed lactic acid bacteria (LAB), such as Lactobacillus plantarum (L. plantarum) have been reported as possible modulators affecting the immune responses in wound healing. However, how signaling molecules regulate this process after the administration of heat-killed LAB remains unclear. In this study, we examined the effect of heat-killed L. plantarum KB131 (KB131) administration on wound healing and the contribution of CARD9, which is an essential signaling adaptor molecule for NF-kB activation upon triggering through C-type lectin receptors, in the effects of this bacterium. We analyzed wound closure, histological findings, and inflammatory responses. We found that administration of KB131 accelerated wound closure, re-epithelialization, granulation area, CD31-positive vessels, and α-SMA-positive myofibroblast accumulated area, as well as the local infiltration of leukocytes. In particular, M2 macrophages were increased, in parallel with CCL5 synthesis. The acceleration of wound healing responses by KB131 was canceled in CARD9-knockout mice. These results indicate that the topical administration of KB131 accelerates wound healing, accompanying increased M2 macrophages, which suggests that CARD9 may be involved in these responses.

Pulmonary fibrosis (PF) is a serious progressive fibrotic disease that is characterized by excessive accumulation of extracellular matrix (ECM), thus resulting in stiff lung tissues. Lysyl oxidase (LOX) is an enzyme involved in fibrosis by catalyzing collagen cross-linking. Studies found that the ingredients in schisandra ameliorated bleomycin (BLM)-induced PF, but it is unknown whether the anti-PF of schisandra is related to LOX. In this study, we established models of PF including a mouse model stimulated by BLM and a HFL1 cell model induced by transforming growth factor (TGF)-β1 to evaluate the inhibition effects of Schisandrin C (Sch C) on PF. We observed that Sch C treatment decreased pulmonary indexes compared to control group. Treatment of Sch C showed a significant reduction in the accumulation of ECM as evidenced by decreased expressions of α-SMA, FN, MMP2, MMP9, TIMP1 and collagen proteins such as Col 1A1, and Col 3A1. In addition, the expression of LOX in the lung tissue of mice after Sch C treatment was effectively decreased compared with the MOD group. The inhibition effects in vitro were consistent with those in vivo. Mechanistic studies revealed that Sch C significantly inhibited TGF-β1/Smad2/3 and TNF-α/JNK signaling pathways. In conclusion, our data demonstrated that Sch C significantly ameliorated PF in vivo and vitro, which may play an important role by reducing ECM deposition and inhibiting the production of LOX.

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. Key players mediating fibrosis are myofibroblasts (MF) that, following transforming growth factor β (TGFβ) exposure, produce a collagen-rich extracellular matrix (ECM) that induces myofibroblast differentiation. Myofibroblasts express αvβ3 integrin (a membrane receptor for thyroid hormones) and miRNA-21 that promotes deiodinase-type-3 expression (D3), causing the degradation of triiodothyronine (T3) that attenuates fibrosis. We hypothesized that αvβ3 affects the fibrotic processes through its thyroid hormones (THs) binding site. To test this, dermal fibroblasts (DF) were cultured with/without TGFβ and removed with a base, leaving only normal/fibrotic ECMs in wells. Then, DF were cultured on the ECMs with/without tetrac (αvβ3 ligand, T4 antagonist), and evaluated for pro-fibrotic characteristics, αvβ3, miRNA-21, and D3 levels. Blood free-T3 (fT3), miRNA-21 levels, and the modified Rodnan skin score (MRSS) were evaluated in SSc patients. We found that the "fibrotic-ECM" significantly increased the pro-fibrotic characteristics of DF and the levels of miRNA-21, D3, and αvβ3, compared to the "normal-ECM." Tetrac significantly inhibited the effects of the "fibrotic-ECM" on the cells. In accordance with tetrac's effect on D3/miRNA-21, a negative correlation was found between the patients' fT3 to miRNA-21 levels, and to the development of pulmonary arterial hypertension (PAH). We conclude that occupying the THs binding site of αvβ3 may delay the development of fibrosis.

Silicosis, characterized by irreversible pulmonary fibrosis, remains a major global public health problem. Nowadays, cumulative studies are focusing on elucidating the pathogenesis of silicosis in order to identify preventive or therapeutic antifibrotic agents. However, the existing research on the mechanism of silica-dust-induced pulmonary fibrosis is only the tip of the iceberg and lags far behind clinical needs. Idiopathic pulmonary fibrosis (IPF), as a pulmonary fibrosis disease, also has the same problem. In this study, we examined the relationship between silicosis and IPF from the perspective of their pathogenesis and fibrotic characteristics, further discussing current drug research and limitations of clinical application in silicosis. Overall, this review provided novel insights for clinical treatment of silicosis with the hope of bridging the gap between research and practice in silicosis.

Organ fibrosis can occur in virtually all major organs with relentlessly progressive and irreversible progress, ultimately resulting in organ dysfunction and potentially death. Unfortunately, current clinical treatments cannot halt or reverse the progression of fibrosis to end-stage organ failure, and thus, advanced antifibrotic therapeutics are urgently needed. In recent years, a growing body of research has revealed that circular RNAs (circRNAs) play pivotal roles in the development and progression of organ fibrosis through highly diverse mechanisms of action. Thus, manipulating circRNAs has emerged as a promising strategy to mitigate fibrosis across different organ types. In this review, we systemically summarize the current state of knowledge about circRNA biological properties and the regulatory mechanisms of circRNAs. A comprehensive overview of major fibrotic signaling pathways and representative circRNAs that are known to modulate fibrotic signals are outlined. Then, we focus on the research progress of the versatile functional roles and underlying molecular mechanisms of circRNAs in various fibrotic diseases in different organs, including the heart, liver, lung, kidney and skin. Finally, we offer a glimpse into the prospects of circRNA-based interference and therapy, as well as their utilization as biomarkers in the diagnosis and prognosis of fibrotic diseases. Video abstract.

Mesenchymal cells in the lung are crucial during development, but also contribute to the pathogenesis of fibrotic disorders, including idiopathic pulmonary fibrosis (IPF), the most common and deadly form of fibrotic interstitial lung diseases. Originally thought to behave as supporting cells for the lung epithelium and endothelium with a singular function of producing basement membrane, mesenchymal cells encompass a variety of cell types, including resident fibroblasts, lipofibroblasts, myofibroblasts, smooth muscle cells, and pericytes, which all occupy different anatomic locations and exhibit diverse homeostatic functions in the lung. During injury, each of these subtypes demonstrate remarkable plasticity and undergo varying capacity to proliferate and differentiate into activated myofibroblasts. Therefore, these cells secrete high levels of extracellular matrix (ECM) proteins and inflammatory cytokines, which contribute to tissue repair, or in pathologic situations, scarring and fibrosis. Whereas epithelial damage is considered the initial trigger that leads to lung injury, lung mesenchymal cells are recognized as the ultimate effector of fibrosis and attempts to better understand the different functions and actions of each mesenchymal cell subtype will lead to a better understanding of why fibrosis develops and how to better target it for future therapy. This review summarizes current findings related to various lung mesenchymal cells as well as signaling pathways, and their contribution to the pathogenesis of pulmonary fibrosis.

Vascular Smooth Muscle Cells (VSMCs) are known to be the key drivers of intimal thickening which contribute to early progression of atherosclerosis. VSMCs are the major producers of extracellular matrix within the vessel wall and in response to atherogenic stimuli they could modify the type of matrix proteins produced. Serotonin receptor 2B (5-HT_2B receptor/HTR2B) has been implicated in several chronic fibrotic and vascular diseases. Although studies have successfully demonstrated the efficacy of HTR2B blockade in attenuating fibrotic disease, the role of 5-HT2B receptor in TGFβ mediated VSMC differentiation remain largely unknown. In the present study, we investigated the potential of targeting the 5-HT2B receptor to prevent TGFβ induced VSMCs differentiation. Our results showed that 5-HT2B receptors are expressed in human atherosclerotic lesion and HTR2B expression positively correlated to the VSMCs markers. We show that AM1125, a selective 5-HT2B receptor inhibitor, significantly inhibits TGFβ1 induced production of collagen and CTGF. The investigation of underlying mechanisms indicated that 5-HT2B receptor antagonism blocks phospho-Smad2 mediated downstream signaling of TGFβ1 in vascular smooth muscle cells. Collectively, the HTR2B/TGF-β1/Phospho-Smad2 pathway plays a critical role in the regulation of VSMCs differentiation. Our findings might serve 5-HT2B receptor as a therapeutic target to limit TGF-β1 induced VSMC differentiation.

Fibrosis is an unmet medical problem due to a lack of evident biomarkers to help develop efficient targeted therapies. Fibrosis can affect almost every organ and eventually induce organ failure. Homeodomain-interacting protein kinase 2 (HIPK2) is a protein kinase that controls several molecular pathways involved in cell death and development and it has been extensively studied, mainly in the cancer biology field. Recently, a role for HIPK2 has been highlighted in tissue fibrosis. Thus, HIPK2 regulates several pro-fibrotic pathways such as Wnt/β-catenin, TGF-β and Notch involved in renal, pulmonary, liver and cardiac fibrosis. These findings suggest a wider role for HIPK2 in tissue physiopathology and highlight HIPK2 as a promising target for therapeutic purposes in fibrosis. Here, we will summarize the recent studies showing the involvement of HIPK2 as a novel regulator of fibrosis.

Fibrotic skin conditions, such as hypertrophic and keloid scars, frequently result from injury to the skin and as sequelae to surgical procedures. The development of skin fibrosis may lead to patient discomfort, limitation in range of motion, and cosmetic disfigurement. Despite the frequency of skin fibrosis, treatments that seek to address the root causes of fibrosis are lacking. Much research into fibrotic pathophysiology has focused on dermal pathology, but less research has been performed to understand aberrations in fibrotic epidermis, leading to an incomplete understanding of dermal fibrosis. The literature on occlusion, a treatment modality known to reduce dermal fibrosis, in part through accelerating wound healing and regulating aberrant epidermal inflammation that otherwise drives fibrosis in the dermis, is reviewed. There is a focus on epidermal-dermal crosstalk, which contributes to the development and maintenance of dermal fibrosis, an underemphasized interplay that may yield novel strategies for treatment if understood in more detail.