Fibrotic Fibroblasts Research Articles

Teatime: epigallocatechin gallate targets fibroblast-epithelial cell crosstalk to combat lung fibrosis.

Epigallocatechin gallate (EGCG) is a polyphenol plant metabolite abundant in tea that has demonstrated antifibrotic properties in the lung. In this issue of the JCI, Cohen, Brumwell, and colleagues interrogated the mechanistic action of EGCG by investigating lung biopsies of patients with mild interstitial lung disease (ILD) who had undergone EGCG treatment. EGCG targeted the WNT inhibitor SFRP2, which was enriched in fibrotic fibroblasts and acted as a TGF-β target, with paracrine effects leading to pathologic basal metaplasia of alveolar epithelial type 2 cells. This study emphasizes the epithelial-mesenchymal trophic unit as a central signaling hub in lung fibrosis. Understanding and simultaneous targeting of interlinked signaling pathways, such as TGF-β and WNT, paves the road for future treatment options for pulmonary fibrosis.

Osthole mitigates the myofibroblast properties in oral submucous fibrosis by suppressing the TGF-β/smad2 signaling pathway and NCK-AS1 expression

Background/purposeNatural products are gaining increasing recognition as an alternative source for alleviating fibrosis as they can regulate various mediators or pathways against fibrosis by targeting non-coding RNAs. In the current study, we aimed to investigate the therapeutic effects of osthole in oral submucous fibrosis (OSF), a precancerous condition of the oral cavity. Materials and methodsThe cytotoxicity of osthole to normal and fibrotic buccal mucosal fibroblasts (fBMFs) derived from OSF tissues was assessed using MTT assay. Collagen gel contraction and transwell migration assays were conducted to examine the myofibroblast activities. Besides, the expression of TGF-β/Smad2 signaling as well as α-SMA and type I collagen were measured. Additionally, RNA sequencing was used to identify a potential target involved in the anti-fibrotic effect of osthole. ResultsOsthole exhibited a higher cytotoxic effect on fBMFs compared to normal BMFs and dose-dependently reduced several myofibroblast activities, including collagen gel contractility and transwell migration ability. In addition, the expression of the TGF-β/Smad2 pathway was inhibited along with a lower expression of α-SMA and type I collagen in osthole-receiving cells. Moreover, the administration of osthole downregulated the expression of NCK1-AS1 in fBMFs, which was proven to mediate the anti-fibrosis property of osthole. ConclusionOur results indicate that osthole may be a promising compound to inhibit the progression of OSF.

Loss of tet methyl cytosine dioxygenase 3 (TET3) enhances cardiac fibrosis via modulating the DNA damage repair response

BackgroundCardiac fibrosis is the hallmark of all forms of chronic heart disease. Activation and proliferation of cardiac fibroblasts are the prime mediators of cardiac fibrosis. Existing studies show that ROS and inflammatory cytokines produced during fibrosis not only signal proliferative stimuli but also contribute to DNA damage. Therefore, as a prerequisite to maintain sustained proliferation in fibroblasts, activation of distinct DNA repair mechanism is essential.ResultIn this study, we report that TET3, a DNA demethylating enzyme, which has been shown to be reduced in cardiac fibrosis and to exert antifibrotic effects does so not only through its demethylating activity but also through maintaining genomic integrity by facilitating error-free homologous recombination (HR) repair of DNA damage. Using both in vitro and in vivo models of cardiac fibrosis as well as data from human heart tissue, we demonstrate that the loss of TET3 in cardiac fibroblasts leads to spontaneous DNA damage and in the presence of TGF-β to a shift from HR to the fast but more error-prone non-homologous end joining repair pathway. This shift contributes to increased fibroblast proliferation in a fibrotic environment. In vitro experiments showed TET3’s recruitment to H2O2-induced DNA double-strand breaks (DSBs) in mouse cardiac fibroblasts, promoting HR repair. Overexpressing TET3 counteracted TGF-β-induced fibroblast proliferation and restored HR repair efficiency. Extending these findings to human cardiac fibrosis, we confirmed TET3 expression loss in fibrotic hearts and identified a negative correlation between TET3 levels, fibrosis markers, and DNA repair pathway alteration.ConclusionCollectively, our findings demonstrate TET3’s pivotal role in modulating DDR and fibroblast proliferation in cardiac fibrosis and further highlight TET3 as a potential therapeutic target.Graphical abstractSchematic representation illustrating the role of TET3 in modulating the DDR response in healthy and fibrotic fibroblasts.

Dendritic Cell - Fibroblast Crosstalk via TLR9 and AHR Signaling Drives Lung Fibrogenesis.

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive scarring and loss of lung function. With limited treatment options, patients succumb to the disease within 2-5 years. The molecular pathogenesis of IPF regarding the immunologic changes that occur is poorly understood. We characterize a role for non-canonical aryl-hydrocarbon receptor signaling (ncAHR) in dendritic cells (DCs) that leads to production of IL-6 and IL-17, promoting fibrosis. TLR9 signaling in myofibroblasts is shown to regulate production of TDO2 which converts tryptophan into the endogenous AHR ligand kynurenine. Mice with augmented ncAHR signaling were created by crossing floxed AHR exon-2 deletion mice (AHR Δex2 ) with mice harboring a CD11c-Cre. Bleomycin was used to study fibrotic pathogenesis. Isolated CD11c+ cells and primary fibroblasts were treated ex-vivo with relevant TLR agonists and AHR modulating compounds to study how AHR signaling influenced inflammatory cytokine production. Human datasets were also interrogated. Inhibition of all AHR signaling rescued fibrosis, however, AHR Δex2 mice treated with bleomycin developed more fibrosis and DCs from these mice were hyperinflammatory and profibrotic upon adoptive transfer. Treatment of fibrotic fibroblasts with TLR9 agonist increased expression of TDO2. Study of human samples corroborate the relevance of these findings in IPF patients. We also, for the first time, identify that AHR exon-2 floxed mice retain capacity for ncAHR signaling.

Alveolar fibroblast lineage orchestrates lung inflammation and fibrosis.

Fibroblasts are present throughout the body and function to maintain tissue homeostasis. Recent studies have identified diverse fibroblast subsets in healthy and injured tissues1,2, but the origins and functional roles of injury-induced fibroblast lineages remain unclear. Here we show that lung-specialized alveolar fibroblasts take on multiple molecular states with distinct roles in facilitating responses to fibrotic lung injury. We generate a genetic tool that uniquely targets alveolar fibroblasts to demonstrate their role in providing niches for alveolar stem cells in homeostasis and show that loss of this niche leads to exaggerated responses to acute lung injury. Lineage tracing identifies alveolar fibroblasts as the dominant origin for multiple emergent fibroblast subsets sequentially driven by inflammatory and pro-fibrotic signals after injury. We identify similar, but not completely identical, fibroblast lineages in human pulmonary fibrosis. TGFβ negatively regulates an inflammatory fibroblast subset that emerges early after injury and stimulates the differentiation into fibrotic fibroblasts to elicit intra-alveolar fibrosis. Blocking the induction of fibrotic fibroblasts in the alveolar fibroblast lineage abrogates fibrosis but exacerbates lung inflammation. These results demonstrate the multifaceted roles of the alveolar fibroblast lineage in maintaining normal alveolar homeostasis and orchestrating sequential responses to lung injury.

Sanglifehrin A mitigates multiorgan fibrosis by targeting the collagen chaperone cyclophilin B.

Pathological deposition and crosslinking of collagen type I by activated myofibroblasts drives progressive tissue fibrosis. Therapies that inhibit collagen synthesis have potential as antifibrotic agents. We identify the collagen chaperone cyclophilin B as a major cellular target of the natural product sanglifehrin A (SfA) using photoaffinity labeling and chemical proteomics. Mechanistically, SfA inhibits and induces the secretion of cyclophilin B from the endoplasmic reticulum (ER) and prevents TGF-β1-activated myofibroblasts from synthesizing and secreting collagen type I in vitro, without inducing ER stress or affecting collagen type I mRNA transcription, myofibroblast migration, contractility, or TGF-β1 signaling. In vivo, SfA induced cyclophilin B secretion in preclinical models of fibrosis, thereby inhibiting collagen synthesis from fibrotic fibroblasts and mitigating the development of lung and skin fibrosis in mice. Ex vivo, SfA induces cyclophilin B secretion and inhibits collagen type I secretion from fibrotic human lung fibroblasts and samples from patients with idiopathic pulmonary fibrosis (IPF). Taken together, we provide chemical, molecular, functional, and translational evidence for demonstrating direct antifibrotic activities of SfA in preclinical and human ex vivo fibrotic models. Our results identify the cellular target of SfA, the collagen chaperone cyclophilin B, as a mechanistic target for the treatment of organ fibrosis.

Multimodal single-cell analyses reveal mechanisms of perianal fistula in diverse patients with Crohn’s disease

Crohn's disease complicated by perianal fistulae is more prevalent and severe in patients of African ancestry. We profiled single cells from diverse patients with Crohn's disease with perianal fistula from colorectal mucosa and fistulous tracts.Immunofluorescence was performed to validate predicted cell-cell interactions. Unstimulated monocytes were chronically cultured in diverse cohorts. A subset was analyzed by single-nucleus RNA+ ATAC sequencing. Fistulous tract cells from complete proctectomies demonstrated enrichment of myeloid cells compared to paired rectal tissues. Ligand-receptor analysis highlights myeloid-stromal cross-talk and cellular senescence, with cellular co-localization validated by immunofluorescence. Chitinase-3 like-protein-1 (CHI3L1) is a top upregulated gene in stromal cells from fistulae expressing both destructive and fibrotic gene signatures. Monocyte cultures from patients of African ancestry and controls demonstrated differences in CHI3L1 and oncostatin M (OSM) expression upon differentiation compared to individuals of European ancestry. Activating protein-1 footprints are present in ATAC-seq peaks in stress response genes, including CHI3L1 and OSM; genome-wide chromatin accessibility including JUN footprints was observed, consistent with reported mechanisms of inflammatory memory. Regulon analyses confirm known cell-specific transcription factor regulation and implicate novel ones in fibroblast subsets. All pseudo-bulked clusters demonstrate enrichment of genetic loci, establishing multicellular contributions. In the most significant African American Crohn's genetic locus, upstream of prostaglandin E receptor 4, lymphoid-predominant ATAC-seq peaks were observed, with predicted RORC footprints. Population differences in myeloid-stromal cross-talk implicate fibrotic and destructive fibroblasts, senescence, epigenetic memory, and cell-specific enhancers in perianal fistula pathogenesis. The transcriptomic and epigenetic data provided here may guide optimization of promising mesenchymal stem cell therapies for perianal fistula. This work was supported by grants U01DK062422, U24DK062429, and R01DK123758.

Ketotifen directly modifies the fibrotic response of human skin fibroblasts

Fibrosis is a destructive, end-stage disease process. In the skin, it is associated with systemic sclerosis and scarring with considerable health burden. Ketotifen is a clinical antihistamine and mast cell stabilizer. Studies have demonstrated mast cell-dependent anti-fibrotic effects of ketotifen but direct effects on fibroblasts have not been determined. Human dermal fibroblasts were treated with pro-fibrotic transforming growth factor-β1 (TGFβ) followed by ketotifen or control treatments to determine direct effects on fibrotic fibroblasts. Ketotifen impaired TGFβ-induced α-smooth muscle actin gene and protein responses and decreased cytoskeletal- and contractility-associated gene responses associated with fibrosis. Ketotifen reduced Yes-associated protein phosphorylation, transcriptional coactivator with PDZ binding motif transcript and protein levels, and phosphorylation of protein kinase B. In a fibroblast-populated collagen gel contraction assay, ketotifen reduced the contractile activity of TGFβ-activated fibroblasts. In a murine model of bleomycin-induced skin fibrosis, collagen density and dermal thickness were significantly decreased in ketotifen-treated mice supporting in vitro findings. These results support a novel, direct anti-fibrotic activity of ketotifen, reducing pro-fibrotic phenotypic changes in fibroblasts and reducing collagen fibres in fibrotic mouse skin. Together, these findings suggest novel therapeutic potential and a novel mechanism of action for ketotifen in the context of fibrosis.

O146: Investigating the cell-matrix interplay in fibrotic remodelling using renal 3D in vitro models

Abstract Introduction The dynamic biophysical microenvironment of the renal extracellular matrix is integral in regulating tissue homeostasis. Matrix remodelling is an iterative process, which guides cell behaviour and pathological fibrosis occurs due to aberrant tissue repair. Fibrosis, characterised by the desmoplastic ECM deposition and tissue stiffening, is prominent in CKD and renal carcinomas. We engineered biomimetic 3D constructs to recapitulate cell-matrix interactions in fibrotic disease progression. Methods Soft collagen-I and laminin constructs (0.2%w/v) were engineered with renal cancer cells (786-O or ACHN) or renal fibroblasts (TK188). Plastic compression was used to generate dense collagen constructs, at 6%w/v collagen density. Mechanical properties were analysed using shear rheology. Gene expression of markers defining the healthy/diseased kidney matrix was determined using qPCR. Results Over 21 days, 786-O cancer cells softened the collagen matrix. Matrix degradation was supported by collagen-I downregulation and MMP7 and vimentin upregulation. Whereas metastatic cancer cells (ACHN) stiffened the dense matrix to ∼1.25kPa, with significant gene upregulation of collagen-I, collagen-IV and LOX. Fibrotic fibroblasts soften the dense matrix by ∼1kPa, with α-SMA and MMP9 upregulation. However, matrix stiffness significantly increases with cancer cell co-cultures. Discussion Renal cancer cells remodel their biophysical environment, altering the construct’s material properties. In our models, collagen density and stromal complexity influences cell behaviour, causing alterations in biomechanics and gene expression. These models can generate physiologically relevant stiffness, enabling investigation between key cell types and the physical environment. Drugs targeting MMPs and LOX will be used to determine if we can disrupt the fibrotic remodelling.

Aberrantly downregulated FENDRR by arecoline elevates ROS and myofibroblast activation via mitigating the miR-214/MFN2 axis

Long non-coding RNA FENDRR possesses both anti-fibrotic and anti-cancer properties, but its significance in the development of premalignant oral submucous fibrosis (OSF) remains unclear. Here, we showed that FENDRR was downregulated in OSF specimens and fibrotic buccal mucosal fibroblasts (fBMFs), and overexpression of FENDRR mitigated various myofibroblasts hallmarks, and vice versa. In the course of investigating the mechanism underlying the implication of FENDRR in myofibroblast transdifferentiation, we found that FENDRR can directly bind to miR-214 and exhibit its suppressive effect on myofibroblast activation via titrating miR-214. Moreover, we showed that mitofusin 2 (MFN2), a protein that is crucial to the fusion of mitochondria, was a direct target of miR-214. Our data suggested that FENDRR was positively correlated with MFN2 and MFN2 was required for the inhibitory property of FENDRR pertaining to myofibroblast phenotypes. Additionally, our results showed that the FENDRR/miR-214 axis participated in the arecoline-induced reactive oxygen species (ROS) accumulation and myofibroblast transdifferentiation. Building on these results, we concluded that the aberrant downregulation of FENDRR in OSF may be associated with chronic exposure to arecoline, leading to upregulation of ROS and myofibroblast activation via the miR-214-mediated suppression of MFN2.

Pro-Fibrotic Effects of CCL18 on Human Lung Fibroblasts Are Mediated via CCR6.

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease of unknown origin, with a median patient survival time of ~3 years after diagnosis without anti-fibrotic therapy. It is characterized by progressive fibrosis indicated by increased collagen deposition and high numbers of fibroblasts in the lung. It has been demonstrated that CCL18 induces collagen and αSMA synthesis in fibroblasts. We aimed to identify the CCL18 receptor responsible for its pro-fibrotic activities. We used a random phage display library to screen for potential CCL18-binding peptides, demonstrated its expression in human lungs and fibroblast lines by PCR and immunostaining and verified its function in cell lines. We identified CCR6 (CD196) as a CCL18 receptor and found its expression in fibrotic lung tissue and lung fibroblast lines derived from fibrotic lungs, but it was almost absent in control lines and tissue. CCL18 induced receptor internalization in a CCR6-overexpressing cell line. CCR6 blockade in primary human lung fibroblasts reduced CCL18-induced FGF2 release as well as collagen-1 and αSMA expression. Knockdown of CCR6 in a mouse fibroblast cell line abolished the induction of collagen and α-smooth muscle actin expression. Our data indicate that CCL18 triggers pro-fibrotic processes via CCR6, highlighting its role in fibrogenesis.

DOP88 Lipids drive myofibroblast activation and the epithelial-mesenchymal transition process in Crohn’s Disease

Abstract Background Fibrostenosis represents one of the major clinical complications of Crohn’s Disease (CD). However, the molecular mechanisms underlying intestinal fibrogenesis remain poorly understood and anti-fibrotic therapy has not yet been developed. Growing evidences supports that oxidative stress and the epithelial-mesenchymal transition (EMT) process contribute to the development and progression of fibrosis. Here, we assessed the role of lipids in fibrogenesis and whether mitochondria dysfunction can support fibrosis formation. Methods Spatial metabolomics analysis and adipophilin (ADFP) staining were performed on surgical specimens from fibrotic ileum and the surrounding region (healthy) derived from CD patients. Fibroblasts isolated from fibrotic and healthy ileum and human induced pluripotent stem cell-derived intestinal organoids (iHOs) were treated for 1-3 weeks with lipid mix (2%) and analyzed by RNA sequencing. Pathways significantly modulated were validated by RT-PCR, WB, FACS analysis, and proliferative, migratory and contraction assays, and mitochondrial functions by Seahorse analyzer. Results Spatial metabolomics revealed a significant accumulation of lipids characterized by very long-chain fatty acids in the fibrotic area compared to surrounding healthy regions, which was further confirmed by ADFP staining. RNA-seq analysis showed overlapping dysregulated pathways between healthy fibroblasts stimulated with lipids and fibrotic fibroblasts, in particular genes related to cell cycle, cytoskeletal reorganization, migration, contractility and cell metabolism (oxidative stress) which were further confirmed by functional assays. Among the genes related to oxidative stress, lipid stimulation significantly decreased NFE2L2 and promoted an increase in CPT1A, gene encoding for a fatty oxidation mediator. Moreover, lipid-stimulated fibroblasts showed a reduction in mitochondrial respiration, particularly basal and maximal respiration, and spare respiratory capacity by Seahorse analysis. On the other hand, long exposure of iHOs to lipids promoted the EMT process through the upregulation of TWIST, ZEB, VIM, and S100a4. Conclusion Lipid stimulation induced myofibroblast activation through oxidative stress and alteration of mitochondrial metabolism, and increased the expression of EMT transcription factors in intestinal epithelial cells (iHOs) that may support fibroblast-mediated pro-fibrotic activity. These data indicate that regulators of fatty acid oxidation involved in the fibrotic process may represent new potential targets for the treatment of fibrostenotic CD patients.

PGF2α signaling drives fibrotic remodeling and fibroblast population dynamics in mice.

Idiopathic pulmonary fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2α, and its cognate receptor FPr (Ptgfr) are implicated as a TGF-β1-independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER-SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen-treated IER-SftpcI73T mice developed an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER-SftpcI73T mice crossed to a Ptgfr-null (FPr-/-) line showed attenuated weight loss and gene dosage-dependent rescue of mortality compared with FPr+/+ cohorts. IER-SftpcI73T/FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single-cell RNA-Seq, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts, which were reprogrammed to an "inflammatory/transitional" cell state in a PGF2α /FPr-dependent manner. Collectively, the findings provide evidence for a role for PGF2α signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.

Mechanism of adipose tissue-derived stromal cell-extracellular vesicles in treating oral submucous fibrosis by blocking the TGF-β1/Smad3 pathway via the miR-760-3p/IGF1R axis.

Oral submucous fibrosis (OSF) is a prevalent chronic condition, and understanding its pathogenesis is crucial for developing effective therapeutic strategies. This study explores the potential of adipose tissue-derived stromal cell-extracellular vesicles (ADSC-EVs) in mitigating OSF and investigates the underlying molecular mechanisms. OSF was induced in mice by arecoline feeding. Adipose tissue-derived stromal cells (ADSCs), fibrotic buccal mucosal fibroblasts (fBMFs) isolated from OSF mice, and ADSC-EVs were comprehensively characterized. The treatment effects of extracellular vesicles (EVs) and pcDNA3.1-IGF1R on fBMF proliferation, migration, and invasion were assessed using Cell Counting Kit-8 (CCK-8) assay, transwell assay, and flow cytometry assay. The expression levels of alpha-smooth muscle actin (α-SMA), collagen I, collagen III, and insulin-like growth factor 1 receptor (IGF1R) were evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot. The interaction between miR-760-3p and IGF1R was investigated. In fBMFs and OSF mice treated with a miR-760-3p inhibitor and/or EVs, the expression patterns of miR-760-3p, IGF1R, and proteins related to the TGF-β1/Smad3 pathway were determined. ADSC-EVs demonstrated the ability to upregulate miR-760-3p, impede cell proliferation, migration, and invasion, and reduce α-SMA, collagen I, and collagen III levels in fBMFs. The expression of miR-760-3p was diminished in ADSC-EVs treated with a miR-760-3p inhibitor. However, silencing miR-760-3p or overexpressing IGF1R partially counteracted the beneficial effects of ADSC-EVs on fBMF fibrosis. miR-760-3p directly targets IGF1R. Significantly, ADSC-EVs exert their suppressive effects on the TGF-β1/Smad3 pathway through the miR-760-3p/IGF1R axis. In summary, ADSC-EVs, by transferring miR-760-3p and inhibiting IGF1R expression, effectively block the TGF-β1/Smad3 pathway, thereby alleviating fibrosis in fBMFs and preventing the progression of OSF.

Inhibition of Oral Fibrinogenesis Through Transforming Growth Factor-Beta/SMAD2/3 Signalling Inhibition Using Mangosteen Pericarp Extract.

Background Chewing areca nuts can result in an oral disorder known as oral submucous fibrosis (OSF), which has the potential to be cancerous. Although it is only beginning to spread to European and the North American continents, it is highly prevalent in Southeast Asia. The probability of malignant transformation from OSF is raised by chewing tobacco use. In the current research, our objective was to assess the potential anti-fibrosis effects and the ability to prevent malignant transformation through the application of mangosteen pericarp extract. Methodology The Ethical Approval-IHEC/SDC/OMED-2101/23/085 from the institution was obtained to conduct this ex vivo study. The cytotoxicity effect of mangosteen pericarp extract on both normal and fibrotic buccal mucosal fibroblasts originating from OSF tissues was tested. Cell proliferationand cell migration by scratch wound healing assay was examined. Dual staining was done to determine the mode of cell death. Additionally, real-time PCR was utilized to measure the expression of TGF-β/Smad2/3 signalling, α-SMA, and type I collagen gene expression. Results Mangosteen extract exerted higher cytotoxicity of fibrotic buccal mucosal fibroblasts compared to normal cells. Furthermore, mangosteen-receiving cells exhibited downregulation in the expression of the TGF-β/Smad2 pathway, as well as reduced expression of α-SMA and type I collagen. Conclusion Findings from this study suggest that mangosteen could serve as a promising agent for averting the progression of oral fibrogenesis and halting the malignancy of the oral epithelium in patients with OSF.

Persistent hypoxia promotes myofibroblast differentiation via GPR-81 and differential regulation of LDH isoenzymes in normal and idiopathic pulmonary fibrosis fibroblasts.

Hypoxia, a state of insufficient oxygen availability, promotes cellular lactate production. Lactate levels are increased in lungs from patients with idiopathic pulmonary fibrosis (IPF), a disease characterized by excessive scar formation, and lactate is implicated in the pathobiology of lung fibrosis. However, the mechanisms underlying the effects of hypoxia and lactate on fibroblast phenotype are poorly understood. We exposed normal and IPF lung fibroblasts to persistent hypoxia and found that increased lactate generation by IPF fibroblasts was driven by the FoxM1-dependent increase of lactate dehydrogenase A (LDHA) coupled with decreased LDHB that was not observed in normal lung fibroblasts. Importantly, hypoxia reduced α-smooth muscle actin (α-SMA) expression in normal fibroblasts but had no significant impact on this marker of differentiation in IPF fibroblasts. Treatment of control and IPF fibroblasts with TGF-β under hypoxic conditions did not significantly change LDHA or LDHB expression. Surprisingly, lactate directly induced the differentiation of normal, but not IPF fibroblasts under hypoxic conditions. Moreover, while expression of GPR-81, a G-protein-coupled receptor that binds extracellular lactate, was increased by hypoxia in both normal and IPF fibroblasts, its inhibition or silencing only suppressed lactate-mediated differentiation in normal fibroblasts. These studies show that hypoxia differentially affects normal and fibrotic fibroblasts, promoting increased lactate generation by IPF fibroblasts through regulation of the LDHA/LDHB ratio and promoting normal lung fibroblast responsiveness to lactate through GPR-81. This supports a novel paradigm in which lactate may serve as a paracrine intercellular signal in oxygen-deficient microenvironments.

Targeting Pulmonary Fibrosis by SLC1A5-Dependent Glutamine Transport Blockade.

The neutral amino acid glutamine plays a central role in TGF-β (transforming growth factor-β)-induced myofibroblast activation and differentiation. Cells take up glutamine mainly through a transporter expressed on the cell surface known as solute carrier SLC1A5 (solute carrier transporter 1A5). In the present work, we demonstrated that profibrotic actions of TGF-β are mediated, at least in part, through a metabolic maladaptation of SLC1A5 and that targeting SLC1A5 abrogates multiple facets of fibroblast activation. This approach could thus represent a novel therapeutic strategy to treat patients with fibroproliferative diseases. We found that SLC1A5 was highly expressed in fibrotic lung fibroblasts and fibroblasts isolated from idiopathic pulmonary fibrosis lungs. The expression of profibrotic targets, cell migration, and anchorage-independent growth by TGF-β required the activity of SLC1A5. Loss or inhibition of SLC1A5 function enhanced fibroblast susceptibility to autophagy; suppressed mTOR, HIF (hypoxia-inducible factor), and Myc signaling; and impaired mitochondrial function, ATP production, and glycolysis. Pharmacological inhibition of SLC1A5 by the small-molecule inhibitor V-9302 shifted fibroblast transcriptional profiles from profibrotic to fibrosis resolving and attenuated fibrosis in a bleomycin-treated mouse model of lung fibrosis. This is the first study, to our knowledge, to demonstrate the utility of a pharmacological inhibitor of glutamine transport in fibrosis, providing a framework for new paradigm-shifting therapies targeting cellular metabolism for this devastating disease.

73 Fibroblasts Derived from Scar Lose Fibrotic Phenotype in Culture: Are We Using the Right Model?

Abstract Introduction Hypertrophic scar (HTS) after burn injury is difficult to treat and leads to lasting morbidity. As such, HTS formation and treatment strategies are essential to study in the laboratory. Animal models of HTS exist, but are limited by high cost and the small numbers of scars that can be created for study. As an alternative, the isolation of HTS cells for study in the laboratory is a common practice. In this study, we examine the maintenance of fibrotic fibroblast phenotype in vitro to determine whether cells retain characteristics of HTS. We hypothesized that these features may not persist in culture. Methods HTSs were formed in Duroc pigs (n=4 scars). On day 105 post-injury, tissue biopsies were obtained from HTS and normal skin (NS). Biopsies were either: saved immediately by flash freezing; stored in dispase solution for overnight incubation to remove the epidermis and then frozen; or incubated in 1 mg/mL collagenase for 6 hours at 37oC to obtain single cell suspensions. These single cells were harvested with Trizol reagent immediately prior to seeding, or were seeded, grown, and harvested 24 hours later. Cells were seeded in DMEM/F12 media with 10% FBS and 1% pen/strep. In a subset of cells, 18% macromolecular crowding (MMC) was achieved through addition of 70/400kDa ficoll to media. RNA was isolated from tissues and cells. qRT-PCR was performed for collagen 1a1 (COL1A1) and galectin 1 (LGALS1). HTS was normalized to NS. Results HTSs had increased stiffness, trans-epidermal water loss, and dyschromia compared to NS (p< 0.05). COL1A1 expression in biopsies harvested from in vivo HTS was 18.96-fold greater compared to NS. After 24 hours at 4oC, this level dropped to 6.28-fold. Cells isolated from immediate processing lost all differential COL1A1 expression in HTS vs. NS (1.75-fold). After 24 hours in culture, fibroblasts down-regulated COL1A1 expression in HTS vs. NS (-2.39-fold). The addition of MMC media to mimic excessive extracellular matrix did not change COL1A1 expression (-2.65-fold). Similarly, for LGALS1, in vivo biopsies had high expression at 3.52-fold in HTS vs. NS and each group thereafter had reduced expression (6.68, 1.09, -1.19, -2.69). Conclusions When fibroblasts are isolated from HTS and digested for use in cell culture experiments, their phenotype changes immediately upon isolation of the cells even prior to seeding. This suggests that additional steps are needed for HTS fibroblast cell isolation to retain HTS cell expression. Applicability of Research to Practice Current methods for isolating scar single cells are likely not nuanced enough to capture the HTS phenotype. This could contribute to the lack of translation of findings from the in vitro environment to clinical scar treatments. Additional research should focus on optimizing methods to culture HTS fibroblasts that are phenotypically similar to in vivo scars in order to study scar interventions. These findings also have implications for single cell sequencing experiments.

Tonic repression of collagen I by the bradykinin receptor 2 in skin fibroblasts.

Imbalance of collagen I expression results in severe pathologies. Apart from activation by the TGFβ-receptor/Smad pathway, control of collagen I expression remains poorly understood. Here, we used human dermal fibroblasts expressing a mCherry fluorescent protein driven by endogenous COL1A1 promoter to functionally screen the kinome and phosphatome. We identify 8 negative regulators, revealing that collagen is under tonic repression. The cell surface receptor BDKRB2 represses collagen I and other pro-fibrotic genes. Interestingly, it also promotes other basal membrane ECM genes. This function is independent of the natural ligand, bradykinin, and of SMAD2/3 factors, instead requiring constant ERK1/2 repression. TGFβ stimulation induces rapid BDKRB2 transcriptional downregulation. Human fibrotic fibroblasts have reduced BDKRB2 levels and enhancing its expression in keloid fibroblasts represses COL1A1. We propose that tonic signalling by BDKRB2 prevents collagen overproduction in skin fibroblasts.

The IL-33:ST2 axis is unlikely to play a central fibrogenic role in idiopathic pulmonary fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a devastating interstitial lung disease (ILD) with limited treatment options. Interleukin-33 (IL-33) is proposed to play a role in the development of IPF however the exclusive use of prophylactic dosing regimens means that the therapeutic benefit of targeting this cytokine in IPF is unclear.MethodsIL-33 expression was assessed in ILD lung sections and human lung fibroblasts (HLFs) by immunohistochemistry and gene/protein expression and responses of HLFs to IL-33 stimulation measured by qPCR. In vivo, the fibrotic potential of IL-33:ST2 signalling was assessed using a murine model of bleomycin (BLM)-induced pulmonary fibrosis and therapeutic dosing with an ST2-Fc fusion protein. Lung and bronchoalveolar lavage fluid were collected for measurement of inflammatory and fibrotic endpoints. Human precision-cut lung slices (PCLS) were stimulated with transforming growth factor-β (TGFβ) or IL-33 and fibrotic readouts assessed.ResultsIL-33 was expressed by fibrotic fibroblasts in situ and was increased by TGFβ treatment in vitro. IL-33 treatment of HLFs did not induce IL6, CXCL8, ACTA2 and COL1A1 mRNA expression with these cells found to lack the IL-33 receptor ST2. Similarly, IL-33 stimulation had no effect on ACTA2, COL1A1, FN1 and fibronectin expression by PCLS. Despite having effects on inflammation suggestive of target engagement, therapeutic dosing with the ST2-Fc fusion protein failed to reduce BLM-induced fibrosis measured by hydroxyproline content or Ashcroft score.ConclusionsTogether these findings suggest the IL-33:ST2 axis does not play a central fibrogenic role in the lungs with therapeutic blockade of this pathway unlikely to surpass the current standard of care for IPF.