Myofibroblast-derived exosomes enhance macrophages to myofibroblasts transition and kidney fibrosis

A critical event in the pathogenesis of kidney fibrosis is the transition of macrophages into myofibroblasts (MMT). Exosomes play an important role in crosstalk among cells in the kidney and the development of renal fibrosis. However, the role of myofibroblast-derived exosomes in the process of MMT and renal fibrosis progression remains unknown. Here, we examined the role of myofibroblast-derived exosomes in MMT and kidney fibrogenesis. In vitro, transforming growth factor-β1 stimulated the differentiation of kidney fibroblasts into myofibroblasts and promoted exosome release from myofibroblasts. RAW264.7 cells were treated with exosomes derived from myofibroblasts. We found purified exosomes from myofibroblasts trigger the MMT. By contrast, inhibition of exosome production with GW4869 or exosome depletion from the conditioned media abolished the ability of myofibroblasts to induce MMT. Mice treatment with myofibroblast-derived exosomes (Myo-Exo) exhibited severe fibrotic lesion and more abundant MMT cells in kidneys with folic acid (FA) injury, which was negated by TANK-banding kinase-1 inhibitor. Furthermore, suppression of exosome production reduced collagen deposition, extracellular matrix protein accumulation, and MMT in FA nephropathy. Collectively, Myo-Exo enhances the MMT and kidney fibrosis. Blockade of exosomes mediated myofibroblasts-macrophages communication may provide a novel therapeutic target for kidney fibrosis.

Delayed Collagen Production without Myofibroblast Formation Contributes to Reduced Scarring in Adult Skin Microwounds

In adult mammals, wound healing predominantly follows a fibrotic pathway, culminating in scar formation. However, cutaneous microwounds generated through fractional photothermolysis, a modality that produces a constellation of microthermal zones, exhibit a markedly different healing trajectory. Our study delineates the cellular attributes of these microthermal zones, underscoring a temporally limited, subclinical inflammatory milieu concomitant with rapid re-epithelialization within 24 hours. This wound closure is facilitated by the activation of genes associated with keratinocyte migration and differentiation. In contrast to macrothermal wounds, which predominantly heal through a robust myofibroblast-mediated collagen deposition, microthermal zones are characterized by absence of wound contraction and feature delayed collagen remodeling, initiating 5-6 weeks after injury. This distinct wound healing is characterized by a rapid re-epithelialization process and a muted inflammatory response, which collectively serve to mitigate excessive myofibroblast activation. Furthermore, we identify an initial reparative phase characterized by a heterogeneous extracellular matrix protein composition, which precedes the delayed collagen remodeling. These findings extend our understanding of cutaneous wound healing and may have significant implications for the optimization of therapeutic strategies aimed at mitigating scar formation.

WSB1, a Hypoxia-Inducible E3 Ligase, Promotes Myofibroblast Accumulation and Attenuates Alveolar Epithelial Regeneration in Mouse Lung Fibrosis

Idiopathic pulmonary fibrosis is a progressive interstitial lung disease for which there is no curative therapy available. Repetitive alveolar epithelial injury repair, myofibroblast accumulation, and excessive collagen deposition are key pathologic features of idiopathic pulmonary fibrosis, eventually leading to cellular hypoxia and respiratory failure. The precise mechanism driving this complex maladaptive process remains inadequately understood. WD repeat and suppressor of cytokine signaling box containing 1 (WSB1) is an E3 ubiquitin ligase, the expression of which is associated strongly with hypoxia, and forms a positive feedback loop with hypoxia-inducible factor 1α (HIF-1α) under anoxic condition. This study explored the expression, cellular distribution, and function of WSB1 in bleomycin (BLM)-induced mouse lung injury and fibrosis. WSB1 expression was highly induced by BLM injury and correlated with the progression of lung fibrosis. Significantly, conditional deletion of Wsb1 in adult mice ameliorated BLM-induced pulmonary fibrosis. Phenotypically, Wsb1-deficient mice showed reduced lipofibroblast to myofibroblast transition, but enhanced alveolar type 2 proliferation and differentiation into alveolar type 1 after BLM injury. Proteomic analysis of mouse lung tissues identified caveolin 2 as a potential downstream target of WSB1, contributing to BLM-induced epithelial injury repair and fibrosis. These findings unravel a vital role for WSB1 induction in lung injury repair, thus highlighting it as a potential therapeutic target for pulmonary fibrosis.

Ablation of Brg1 in fibroblast/myofibroblast lineages attenuates renal fibrosis in mice with diabetic nephropathy

AIMS

Diabetic nephropathy (DN) is one of the most common complications of diabetes and represents a prototypical form of chronic kidney disease (CKD). Interstitial fibrosis is a key pathological feature of DN. During DN-associated renal fibrosis, resident fibroblasts trans-differentiate into myofibroblasts to remodel the extracellular matrix, the underlying epigenetic mechanism of which is not entirely clear.

METHODS

Diabetic nephropathy was induced in C57B6/j mice by a single injection with streptozotocin (STZ). Gene expression was examined by quantitative PCR and Western blotting. Renal fibrosis was evaluated by PicroSirius Red staining.

RESULTS

We report that expression of Brg1, a chromatin remodeling protein, in renal fibroblasts was up-regulated during DN pathogenesis as assessed by single-cell RNA-seq. Treatment with high glucose similarly augmented Brg1 expression in primary renal fibroblasts in vitro. Importantly, Brg1 ablation in quiescent renal fibroblasts or in mature myofibroblasts equivalently attenuated renal fibrosis in the context of diabetic nephropathy in mice. Additionally, administration with a small-molecule Brg1 inhibitor PFI-3 ameliorated renal fibrosis and improved renal function in mice induced to develop DN.

SIGNIFICANCE

In conclusion, our data provide novel genetic evidence that links Brg1 to fibroblast-myofibroblast transition and renewed rationale for targeting Brg1 in the intervention of DN-associated renal fibrosis.

Cathelicidin LL-37 Expression in Human Breast Implant Capsules

BACKGROUND

Capsular contracture is the most common complication following breast implant placement. Cathelicidin LL-37 is a cationic peptide involved in innate immunity. Initially investigated for its antimicrobial role, it was found to have pleiotropic activities, such as immunomodulation, angiogenesis stimulation, and tissue healing. The aim of the study was to investigate the expression and localization of LL-37 in human breast implant capsules and its relationship with capsular formation, remodeling, and clinical outcomes.

METHODS

The study enrolled 28 women (29 implants) who underwent expander substitution with definitive implant. Contracture severity was evaluated. Specimens were stained with hematoxylin and eosin, Masson trichrome, immunohistochemistry, and immunofluorescence for LL-37, CD68, α-smooth muscle actin, collagen type I and type III, CD31, and Toll-like receptor-4.

RESULTS

LL-37 was expressed in macrophages and myofibroblasts of capsular tissue in 10 (34%) and nine (31%) of the specimens, respectively. In eight cases (27.5%), it was expressed by both macrophages and myofibroblasts of the same specimen. In infected capsules, expression by both cell types was found in all (100%) specimens. LL-37 expression by myofibroblasts positively correlated with its expression by macrophages ( P < 0.001). Moreover, LL-37 expression by macrophages of periexpander capsules negatively correlated with the severity of capsular contracture on definitive implants ( P = 0.04).

CONCLUSIONS

This study demonstrates the expression of LL-37 in macrophages and myofibroblasts of capsular tissue and its negative correlation with the severity of capsular contracture following permanent implant placement. Expression or up-regulation of LL-37 may be involved in myofibroblast and macrophage modulation, thus playing a role in the pathogenic fibrotic process underlying capsular contracture.

CLINICAL RELEVANCE STATEMENT

This is the first study to demonstrate LL37 expression in capsular tissue and to hypothesize its role in contracture and as a prognostic marker for contracture severity. If confirmed, medical strategies or implant coating could be implemented to reduce the risk of contracture for high-risk patients.

PBX/Knotted 1 homeobox-2 (PKNOX2) is a novel regulator of myocardial fibrosis

Much effort has been made to uncover the cellular heterogeneities of human hearts by single-nucleus RNA sequencing. However, the cardiac transcriptional regulation networks have not been systematically described because of the limitations in detecting transcription factors. In this study, we optimized a pipeline for isolating nuclei and conducting single-nucleus RNA sequencing targeted to detect a higher number of cell signal genes and an optimal number of transcription factors. With this unbiased protocol, we characterized the cellular composition of healthy human hearts and investigated the transcriptional regulation networks involved in determining the cellular identities and functions of the main cardiac cell subtypes. Particularly in fibroblasts, a novel regulator, PKNOX2, was identified as being associated with physiological fibroblast activation in healthy hearts. To validate the roles of these transcription factors in maintaining homeostasis, we used single-nucleus RNA-sequencing analysis of transplanted failing hearts focusing on fibroblast remodelling. The trajectory analysis suggested that PKNOX2 was abnormally decreased from fibroblast activation to pathological myofibroblast formation. Both gain- and loss-of-function in vitro experiments demonstrated the inhibitory role of PKNOX2 in pathological fibrosis remodelling. Moreover, fibroblast-specific overexpression and knockout of PKNOX2 in a heart failure mouse model induced by transverse aortic constriction surgery significantly improved and aggravated myocardial fibrosis, respectively. In summary, this study established a high-quality pipeline for single-nucleus RNA-sequencing analysis of heart muscle. With this optimized protocol, we described the transcriptional regulation networks of the main cardiac cell subtypes and identified PKNOX2 as a novel regulator in suppressing fibrosis and a potential therapeutic target for future translational studies.

Exclusive expression of KANK4 promotes myofibroblast mobility in keloid tissues

Keloids are characterized by abnormal wound healing with excessive accumulation of extracellular matrix. Myofibroblasts are the primary contributor to extracellular matrix secretion, playing an essential role in the wound healing process. However, the differences between myofibroblasts involved in keloid formation and normal wound healing remain unclear. To identify the specific characteristics of keloid myofibroblasts, we initially assessed the expression levels of well-established myofibroblast markers, α-smooth muscle actin (α-SMA) and transgelin (TAGLN), in scar and keloid tissues (n = 63 and 51, respectively). Although myofibroblasts were present in significant quantities in keloids and immature scars, they were absent in mature scars. Next, we conducted RNA sequencing using myofibroblast-rich areas from keloids and immature scars to investigate the difference in RNA expression profiles among myofibroblasts. Among significantly upregulated 112 genes, KN motif and ankyrin repeat domains 4 (KANK4) was identified as a specifically upregulated gene in keloids. Immunohistochemical analysis showed that KANK4 protein was expressed in myofibroblasts in keloid tissues; however, it was not expressed in any myofibroblasts in immature scar tissues. Overexpression of KANK4 enhanced cell mobility in keloid myofibroblasts. Our results suggest that the KANK4-mediated increase in myofibroblast mobility contributes to keloid pathogenesis.

Dynamic Hippo pathway activity underlies mesenchymal differentiation during lung alveolar morphogenesis

Alveologenesis, the final stage in lung development, substantially remodels the distal lung, expanding the alveolar surface area for efficient gas exchange. Secondary crest myofibroblasts (SCMF) exist transiently in the neonatal distal lung and are crucial for alveologenesis. However, the pathways that regulate SCMF function, proliferation and temporal identity remain poorly understood. To address this, we purified SCMFs from reporter mice, performed bulk RNA-seq and found dynamic changes in Hippo-signaling components during alveologenesis. We deleted the Hippo effectors Yap/Taz from Acta2-expressing cells at the onset of alveologenesis, causing a significant arrest in alveolar development. Using single cell RNA-seq, we identified a distinct cluster of cells in mutant lungs with altered expression of marker genes associated with proximal mesenchymal cell types, airway smooth muscle and alveolar duct myofibroblasts. In vitro studies confirmed that Yap/Taz regulates myofibroblast-associated gene signature and contractility. Together, our findings show that Yap/Taz is essential for maintaining functional myofibroblast identity during postnatal alveologenesis.

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.

In Vitro Assessment of Cardiac Fibroblast Activation at Physiologic Stiffness

Cardiac fibroblasts (CF) are an essential cell type in cardiac physiology, playing diverse roles in maintaining structural integrity, extracellular matrix (ECM) synthesis, and tissue repair. Under normal conditions, these cells reside in the interstitium in a quiescent state poised to sense and respond to injury by synthesizing and secreting collagen, vimentin, hyaluronan, and other ECM components. In response to mechanical and chemical stimuli, these "resident" fibroblasts can undergo a transformation through a continuum of activation states into what is commonly known as a "myofibroblast," in a process critical for injury response. Despite progress in understanding the contribution of fibroblasts to cardiac health and disease, much remains unknown about the signaling mediating this activation, in part owing to technical challenges in evaluating CF function and activation status in vitro. Given their role in monitoring the ECM, CFs are acutely sensitive to stiffness and pressure. High basal activation of isolated CFs is common due to the super-physiologic stiffness of traditional cell culture substrates, making assays dependent on quiescent cells challenging. To overcome this problem, cell culture parameters must be tightly controlled, and the use of dishes coated with biocompatible reduced-stiffness substrates, such as 8-kPa polydimethylsiloxane (PDMS), has shown promise in reducing basal activation of fibroblasts. Here, we describe cell culture protocol for maintaining CF quiescence in vitro to enable a dynamic range for the assessment of activation status in response to fibrogenic stimuli using PDMS-coated coverslips. Our protocol provides a cost-effective tool to study fibroblast signaling and activity, allowing researchers to better understand the underlying mechanisms involved in cardiac fibrosis. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Generation of 8-kPa polydimethylsiloxane (PDMS)/gelatin-coated coverslips for cardiac fibroblast cell culture Basic Protocol 2: Isolation of adult cardiac fibroblasts and plating onto PDMS coverslips Basic Protocol 3: Assessment of cardiac fibroblast activation by α smooth muscle actin (αSMA) immunocytochemistry.

The role of epithelial cells in fibrosis: Mechanisms and treatment

Fibrosis is a pathological process that affects multiple organs and is considered one of the major causes of morbidity and mortality in multiple diseases, resulting in an enormous disease burden. Current studies have focused on fibroblasts and myofibroblasts, which directly lead to imbalance in generation and degradation of extracellular matrix (ECM). In recent years, an increasing number of studies have focused on the role of epithelial cells in fibrosis. In some cases, epithelial cells are first exposed to external physicochemical stimuli that may directly drive collagen accumulation in the mesenchyme. In other cases, the source of stimulation is mainly immune cells and some cytokines, and epithelial cells are similarly altered in the process. In this review, we will focus on the multiple dynamic alterations involved in epithelial cells after injury and during fibrogenesis, discuss the association among them, and summarize some therapies targeting changed epithelial cells. Especially, epithelial mesenchymal transition (EMT) is the key central step, which is closely linked to other biological behaviors. Meanwhile, we think studies on disruption of epithelial barrier, epithelial cell death and altered basal stem cell populations and stemness in fibrosis are not appreciated. We believe that therapies targeted epithelial cells can prevent the progress of fibrosis, but not reverse it. The epithelial cell targeting therapies will provide a wonderful preventive and delaying action.

Temporal gene signature of myofibroblast transformation in Peyronie's disease: first insights into the molecular mechanisms of irreversibility

BACKGROUND

Transformation of resident fibroblasts to profibrotic myofibroblasts in the tunica albuginea is a critical step in the pathophysiology of Peyronie's disease (PD). We have previously shown that myofibroblasts do not revert to the fibroblast phenotype and we suggested that there is a point of no return at 36 hours after induction of the transformation. However, the molecular mechanisms that drive this proposed irreversibility are not known.

AIM

Identify molecular pathways that drive the irreversibility of myofibroblast transformation by analyzing the expression of the genes involved in the process in a temporal fashion.

METHODS

Human primary fibroblasts obtained from tunica albuginea of patients with Peyronie's disease were transformed to myofibroblasts using transforming growth factor beta 1 (TGF-β1). The mRNA of the cells was collected at 0, 24, 36, 48, and 72 hours after stimulation with TGF-β1 and then analyzed using a Nanostring nCounter Fibrosis panel. The gene expression results were analyzed using Reactome pathway analysis database and ANNi, a deep learning-based inference algorithm based on a swarm approach.

OUTCOMES

The study outcome was the time course of changes in gene expression during transformation of PD-derived fibroblasts to myofibroblasts.

RESULTS

The temporal analysis of the gene expression revealed that the majority of the changes at the gene expression level happened within the first 24 hours and remained so throughout the 72-hour period. At 36 hours, significant changes were observed in genes involved in MAPK-Hedgehog signaling pathways.

CLINICAL TRANSLATION

This study highlights the importance of early intervention in clinical management of PD and the future potential of new drugs targeting the point of no return.

STRENGTHS AND LIMITATIONS

The use of human primary cells and confirmation of results with further RNA analysis are the strengths of this study. The study was limited to 760 genes rather than the whole transcriptome.

CONCLUSION

This study is to our knowledge the first analysis of temporal gene expression associated with the regulation of the transformation of resident fibroblasts to profibrotic myofibroblasts in PD. Further research is warranted to investigate the role of the MAPK-Hedgehog signaling pathways in reversibility of PD.

The mechanism of Shenlong Jianji treatment of idiopathic pulmonary fibrosis inhibits fibroblast-to-myofibroblast transformation via the TGF-β1/smads signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Shenlong Jianji (SLJJ) is a Chinese herbal compound composed of traditional medicines for supplementing Qi, nourishing Yin, promoting blood circulation, and removing obstruction in channels. It is widely used to treat idiopathic pulmonary fibrosis (IPF) in China. However, the underlying mechanism of SLJJ remains unclear.

AIM OF THIS STUDY

To elucidate the efficacy and mechanisms of SLJJ in the treatment of IPF through in vivo and in vitro experiments.

MATERIAL AND METHODS

84 Wistar rats were randomly and equally divided into 7 groups: the control group (CTRL), the sham operation group (SHAM), the model group (IPF), the low dose of SLJJ group (L-SLJJ), the middle dose of SLJJ group (M-SLJJ), the high dose of SLJJ group (H-SLJJ), and the pirfenidone group (PFD). The rats in the CTRL, SHAM, and IPF groups were given normal saline each time for 28 days; the SLJJ groups were given Shenlong Jianji (9 g kg-1·d-1, 18 g kg-1·d-1, 36 g kg-1·d-1), and pirfenidone was administered as a sequential dose. After 28 days, the general condition of the rats was evaluated, and samples were collected. The lung coefficient was measured. The pathological changes of lung in each group were observed by H&E staining and Masson staining. α-SMA, collagen 1, and E-cadherin proteins were detected by immunohistochemistry. α-SMA, collagen 1, vimentin, E-cadherin, N-cadherin, TGF-β1, smad2, and smad3 proteins were detected by WB in vivo.In vitro, A scratch test was used to assess the ratio of cell migration. α-SMA, vimentin, E-cadherin, and N-cadherin protein levels were evaluated by a cellular immunofluorescence assay. TGF-β1/smads signaling pathway was detected by WB. HPLC-Q-TOF/MS analysis was used to identify the active compounds in the SLJJ. Molecular docking determined the free binding energy of the compound with the TGF-β1 protein.

RESULTS

SLJJ significantly improved the respiratory symptoms, heart rate, mental state, and food intake of IPF group rats and decreased the lung coefficient. In the IPF group, inflammatory cells were infiltrated, and the thickened alveoli wall and alveoli collapse were shown, while significantly alleviating pathological changes in the SLJJ and PFD groups. Masson staining showed that SLJJ and PFD decreased the collagen expression. Immunohistochemical results showed that the expressions of α-SMA, collagen 1, and N-cadherin decreased in the SLJJ and PFD groups, while E-cadherin increased significantly compared with the IPF group. SLJJ regulates TGF-β1/smads signaling pathway proteins in vivo. SLJJ decreased the ratio of migration in HFL-1 cells; SLJJ reduced the fluorescence intensity of α-SMA, vimentin, and N-cadherin and increased the fluorescence intensity of E-cadherin in primary rat lung (PRL) fibroblast cells and HFL-1 cells. WB results showed that SLJJ significantly down-regulated α-SMA, Vimentin, N-cadherin, TGF-β1, smad2, and p-smad2/3 proteins expression and up-regulated E-cadherin protein expression in vitro, whereas SRI-011381 (a TGF-β1 agonist) antagonized the effects of SLJJ.

CONCLUSION

SLJJ inhibits idiopathic pulmonary fibrosis. The TGF- β1/Smads signaling pathway can be the target of SLJJ, which inhibits fibroblast-to-myofibroblast transformation and is expected to be a new drug for the treatment of IPF.

Deciphering the molecular landscape: integrating single-cell transcriptomics to unravel myofibroblast dynamics and therapeutic targets in clear cell renal cell carcinomas

Background

Clear cell renal cell carcinomas (ccRCCs) epitomize the most formidable clinical subtype among renal neoplasms. While the impact of tumor-associated fibroblasts on ccRCC progression is duly acknowledged, a paucity of literature exists elucidating the intricate mechanisms and signaling pathways operative at the individual cellular level.

Methods

Employing single-cell transcriptomic analysis, we meticulously curated UMAP profiles spanning substantial ccRCC populations, delving into the composition and intrinsic signaling pathways of these cohorts. Additionally, Myofibroblasts were fastidiously categorized into discrete subpopulations, with a thorough elucidation of the temporal trajectory relationships between these subpopulations. We further probed the cellular interaction pathways connecting pivotal subpopulations with tumors. Our endeavor also encompassed the identification of prognostic genes associated with these subpopulations through Bulk RNA-seq, subsequently validated through empirical experimentation.

Results

A notable escalation in the nFeature and nCount of Myofibroblasts and EPCs within ccRCCs was observed, notably enriched in oxidation-related pathways. This phenomenon is postulated to be closely associated with the heightened metabolic activities of Myofibroblasts and EPCs. The Myofibroblasts subpopulation, denoted as C3 HMGA1+ Myofibroblasts, emerges as a pivotal subset, displaying low differentiation and positioning itself at the terminal point of the temporal trajectory. Intriguingly, these cells exhibit a high degree of interaction with tumor cells through the MPZ signaling pathway network, suggesting that Myofibroblasts may facilitate tumor progression via this pathway. Prognostic genes associated with C3 were identified, among which TUBB3 is implicated in potential resistance to tumor recurrence. Finally, experimental validation revealed that the knockout of the key gene within the MPZ pathway, MPZL1, can inhibit tumor activity, proliferation, invasion, and migration capabilities.

Conclusion

This investigation delves into the intricate mechanisms and interaction pathways between Myofibroblasts and ccRCCs at the single-cell level. We propose that targeting MPZL1 and the oxidative phosphorylation pathway could serve as potential key targets for treating the progression and recurrence of ccRCC. This discovery paves the way for new directions in the treatment and prognosis diagnosis of ccRCC in the future.

Increased extracellular matrix stiffness regulates myofibroblast transformation through induction of autophagy-mediated Kindlin-2 cytoplasmic translocation

The extracellular matrix (ECM) mechanical properties regulate biological processes, such as fibroblast-myofibroblast transformation (FMT), which is a crucial component in pelvic organ prolapse (POP) development. The 'Kindlin-2' protein, expressed by fibroblasts, plays an important role in the development of the mesoderm, which is responsible for connective tissue formation; however, the role of Kindlin-2 in FMT remains to be explored. In this study, we aimed to explore the role of Kindlin-2 in FMT as it relates to POP. We found that ECM stiffness induces autophagy to translocate Kindlin-2 to the cytoplasm of L929 cells, where it interacts with and degrades MOB1, thereby facilitating Yes-associated protein (YAP) entry into the nucleus and influencing FMT progression. Stiffness-induced autophagy was inhibited when using an autophagy inhibitor, which blocked the translocation of Kindlin-2 to the cytoplasm and partially reversed high-stiffness-induced FMT. In patients with POP, we observed an increase in cytoplasmic Kindlin-2 and nuclear YAP levels. Similar changes in vaginal wall-associated proteins were observed in a mouse model of acute vaginal injury. In conclusion, Kindlin-2 is a key gene affecting ECM stiffness, which regulates FMT by inducing autophagy and may influence the development of POP.

Sophocarpine alleviates intestinal fibrosis via inhibition of inflammation and fibroblast into myofibroblast transition by targeting the Sirt1/p65 signaling axis

In this study, we used alkaloids from Sophora flavescens to inhibit the SASP, leading to fibroblast-into-myofibroblast transition (FMT) to maintain intestinal mucosal homeostasis in vitro and in vivo. We used western blotting (WB) and immunofluorescence staining (IF) to assess whether five kinds of alkaloids inhibit the major inflammatory pathways and chose the most effective compound (sophocarpine; SPC) to ameliorate colorectal inflammation in a dextran sulfate sodium (DSS)-induced UC mouse model. IF, Immunohistochemistry staining (IHC), WB, disease activity index (DAI), and enzyme-linked immunosorbent assay (ELISA) were conducted to investigate the mechanism of action of this compound. Next, we detected the pharmacological activity of SPC on the senescence-associated secretory phenotypes (SASP) and FMT in interleukin 6 (IL-6)-induced senescence-like fibroblasts and discussed the mucosal protection ability of SPC on a fibroblast-epithelium/organoid coculture system and organ-on-chip system. Taken together, our results provide evidence that SPC alleviates the inflammatory response, improves intestinal fibrosis and maintains intestinal mucosal homeostasis in vivo. Meanwhile, SPC was able to prevent IL-6-induced SASP and FMT in fibroblasts, maintain the expression of TJ proteins, and inhibit inflammation and genomic stability of colonic mucosal epithelial cells by activating SIRT1 in vitro. In conclusion, SPC treatment attenuates intestinal fibrosis by regulating SIRT1/NF-κB p65 signaling, and it might be a promising therapeutic agent for inflammatory bowel disease.

Tonic ErbB signaling underlies TGFβ-induced activation of ERK and is required for lens cell epithelial to myofibroblast transition

Fibrosis is a major, but incompletely understood, component of many diseases. The most common vision-disrupting complication of cataract surgery involves differentiation of residual lens cells into myofibroblasts. In serum-free primary cultures of lens epithelial cells (DCDMLs), inhibitors of either ERK or of ErbB signaling prevent TGFβ from upregulating both early (fibronectin) and late (αSMA) markers of myofibroblast differentiation. TGFβ stimulates ERK in DCDMLs within 1.5 h. Kinase inhibitors of ErbBs, but not of several other growth factor receptors in lens cells, reduce phospho ERK to below basal levels in the absence or presence of TGFβ. This effect is attributable to constitutive ErbB activity playing a major role in regulating the basal levels pERK. Additional studies support a model in which TGFβ-generated reactive oxygen species serve to indirectly amplify ERK signaling downstream of tonically active ErbBs to mediate myofibroblast differentiation. ERK activity is in turn essential for expression of ErbB1 and ErbB2, major inducers of ERK signaling. By mechanistically linking TGFβ, ErbB, and ERK signaling to myofibroblast differentiation, our data elucidate a new role for ErbBs in fibrosis and reveal a novel mode by which TGFβ directs lens cell fate.

Intermittent hypoxia induces myofibroblast differentiation and extracellular matrix production of MRC5s via HIF-1α-TGF-β/Smad pathway

PURPOSE

To investigate whether or not intermittent hypoxia (IH), the main characteristic of obstructive sleep apnea (OSA) may affect the myofibroblast differentiation and extracellular matrix (ECM) production of lung fibroblast through the HIF-1α-TGF-β/Smad pathway and assess the interventional role of a HIF-1α inhibitor, 2-methoxyestradiol (2-ME2).

METHOD

The human lung fibroblast MRC5 cells were exposed to normoxia or IH conditions, and the expression of myofibroblast differentiation marker α-smooth muscle actin (α-SMA) and ECM protein collagen I were evaluated. To clarify the underlying mechanism, the expression level of HIF-1α, TGF-β, and p-Smads/Smads were measured and the effects of inhibiting HIF-1α with 2-ME2 on the α-SMA expression level and ECM production through the TGF-β/Smad pathway were assessed. Si HIF-1α was applied to genetically inhibit HIF-1α in MRC5 cells, and the related proteins were assessed.

RESULTS

IH increased the protein and mRNA expression of Collagen I and α-SMA of MRC5 cells in a time-dependent manner. IH activated the protein and mRNA level of HIF-1α and TGF-β and increased the phosphorylation of Smad2/Smad3 of MRC5 cells in a time-dependent manner. 2-ME2 inhibited the activation of HIF-1α induced by IH and decreased overexpression of TGF-β, p-Smad2/Smad2, and p-Smad3/Smad3, which in turn partially reversed the upregulation of α-SMA and Collagen I induced by IH in MRC5 cells. When HIF-1α was successfully silenced by si-HIF-1α, upregulation of TGF-β induced by intermittent hypoxia was partially decreased.

CONCLUSIONS

This study showed that IH contributes to myofibroblast differentiation and excessive ECM production of MRC5 cells through activation of the HIF-1α-TGF-β/Smad pathway. 2-ME2 partially attenuated myofibroblast differentiation induced by IH by inhibiting the HIF-1α-TGF-β/Smad pathway.

The chromatin remodeling protein BRG1 mediates Ang II induced pro-fibrogenic response in renal fibroblasts

AIMS

Renal fibrosis is an important pathophysiological process commonly observed in patients chronic kidney disease (CKD). Angiotensin II (Ang II) is a major risk factor for CKD in part by promoting renal fibrosis. In the present study we investigated Brahma-Related Gene 1 (BRG1, encoded by Smarca4) in Ang II induced pro-fibrogenic response in renal fibroblasts.

METHODS AND MATERIALS

CKD was induced by chronic angiotensin II infusion. Fibroblast- and myofibroblast-specific BRG1 deletion was achieved by crossing the BRG1f/f mice to the Col1a1-CreERT2 mice and the Postn-CreERT2 mice, respectively.

KEY FINDINGS

BRG1 expression was up-regulated when fibroblasts were exposed to Ang II in vitro and in vivo. BRG1 silencing in primary renal fibroblasts blocked transition to myofibroblasts as evidenced by down-regulation of myofibroblast marker genes and reduction in cell proliferation, migration, and contraction. Consistently, deletion of BRG1 from fibroblasts or from myofibroblasts significantly attenuated renal fibrosis in mice subjected to chronic Ang II infusion. Transcriptomic analysis indicated that BRG1 primarily regulated expression of genes involved in cell migroproliferative behavior and extracellular matrix remodeling. Importantly, administration of PFI-3, a small-molecule BRG1 inhibition, markedly ameliorated Ang II induced renal fibrosis in mice.

SIGNIFICANCE

Our data support a role for BRG1 in Ang II induced fibrogenic response in renal fibroblasts and suggest that targeting BRG1 could be considered as a reasonable approach for the intervention of CKD.

Role of ZIP kinase in development of myofibroblast differentiation from HPMCs

During the development of pleural fibrosis, pleural mesothelial cells (PMCs) undergo phenotypic switching from differentiated mesothelial cells to mesenchymal cells (MesoMT). Here, we investigated how external stimuli such as TGF-β induce HPMC-derived myofibroblast differentiation to facilitate the development of pleural fibrosis. TGF-β significantly increased di-phosphorylation but not mono-phosphorylation of myosin II regulatory light chain (RLC) in HPMCs. An increase in RLC di-phosphorylation was also found at the pleural layer of our carbon black bleomycin (CBB) pleural fibrosis mouse model, where it showed filamentous localization that coincided with alpha smooth muscle actin (αSMA) in the cells in the pleura. Among the protein kinases that can phosphorylate myosin II RLC, ZIPK (zipper-interacting kinase) protein expression was significantly augmented after TGF-β stimulation. Furthermore, ZIPK gene silencing attenuated RLC di-phosphorylation, suggesting that ZIPK is responsible for di-phosphorylation of myosin II in HPMCs. Although TGF-β significantly increased the expression of ZIP kinase protein, the change in ZIP kinase mRNA was marginal, suggesting a posttranscriptional mechanism for the regulation of ZIP kinase expression by TGF-β. ZIPK gene knockdown (KD) also significantly reduced TGF-β-induced upregulation of αSMA expression. This finding suggests that siZIPK attenuates myofibroblast differentiation of HPMCs. siZIPK diminished TGF-β-induced contractility of HPMCs consistent with siZIPK-induced decrease in the di-phosphorylation of myosin II RLC. The present results implicate ZIPK in the regulation of the contractility of HPMC-derived myofibroblasts, phenotype switching, and myofibroblast differentiation of HPMCs.NEW & NOTEWORTHY Here, we highlight that ZIP kinase is responsible for di-phosphorylation of myosin light chain, which facilitates stress fiber formation and actomyosin-based cell contraction during mesothelial to mesenchymal transition in human pleural mesothelial cells. This transition has a significant impact on tissue remodeling and subsequent stiffness of the pleura. This study provides insight into a new therapeutic strategy for the treatment of pleural fibrosis.

IL11-mediated stromal cell activation may not be the master regulator of pro-fibrotic signaling downstream of TGFβ

Fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF) and systemic scleroderma (SSc), are commonly associated with high morbidity and mortality, thereby representing a significant unmet medical need. Interleukin 11 (IL11)-mediated cell activation has been identified as a central mechanism for promoting fibrosis downstream of TGFβ. IL11 signaling has recently been reported to promote fibroblast-to-myofibroblast transition, thus leading to various pro-fibrotic phenotypic changes. We confirmed increased mRNA expression of IL11 and IL11Rα in fibrotic diseases by OMICs approaches and in situ hybridization. However, the vital role of IL11 as a driver for fibrosis was not recapitulated. While induction of IL11 secretion was observed downstream of TGFβ signaling in human lung fibroblasts and epithelial cells, the cellular responses induced by IL11 was quantitatively and qualitatively inferior to that of TGFβ at the transcriptional and translational levels. IL11 blocking antibodies inhibited IL11Rα-proximal STAT3 activation but failed to block TGFβ-induced profibrotic signals. In summary, our results challenge the concept of IL11 blockade as a strategy for providing transformative treatment for fibrosis.

TEA domain transcription factor 1(TEAD1) induces cardiac fibroblasts cells remodeling through BRD4/Wnt4 pathway

Cardiac fibroblasts (CFs) are the primary cells tasked with depositing and remodeling collagen and significantly associated with heart failure (HF). TEAD1 has been shown to be essential for heart development and homeostasis. However, fibroblast endogenous TEAD1 in cardiac remodeling remains incompletely understood. Transcriptomic analyses revealed consistently upregulated cardiac TEAD1 expression in mice 4 weeks after transverse aortic constriction (TAC) and Ang-II infusion. Further investigation revealed that CFs were the primary cell type expressing elevated TEAD1 levels in response to pressure overload. Conditional TEAD1 knockout was achieved by crossing TEAD1-floxed mice with CFs- and myofibroblasts-specific Cre mice. Echocardiographic and histological analyses demonstrated that CFs- and myofibroblasts-specific TEAD1 deficiency and treatment with TEAD1 inhibitor, VT103, ameliorated TAC-induced cardiac remodeling. Mechanistically, RNA-seq and ChIP-seq analysis identified Wnt4 as a novel TEAD1 target. TEAD1 has been shown to promote the fibroblast-to-myofibroblast transition through the Wnt signalling pathway, and genetic Wnt4 knockdown inhibited the pro-transformation phenotype in CFs with TEAD1 overexpression. Furthermore, co-immunoprecipitation combined with mass spectrometry, chromatin immunoprecipitation, and luciferase assays demonstrated interaction between TEAD1 and BET protein BRD4, leading to the binding and activation of the Wnt4 promoter. In conclusion, TEAD1 is an essential regulator of the pro-fibrotic CFs phenotype associated with pathological cardiac remodeling via the BRD4/Wnt4 signalling pathway.

Pharmacological Stimulation of Soluble Guanylate Cyclase Counteracts the Profibrotic Activation of Human Conjunctival Fibroblasts

Conjunctival fibrosis is a serious clinical concern implicated in a wide spectrum of eye diseases, including outcomes of surgery for pterygium and glaucoma. It is mainly driven by chronic inflammation that stimulates conjunctival fibroblasts to differentiate into myofibroblasts over time, leading to abnormal wound healing and scar formation. Soluble guanylate cyclase (sGC) stimulation was found to suppress transforming growth factor β (TGFβ)-induced myofibroblastic differentiation in various stromal cells such as skin and pulmonary fibroblasts, as well as corneal keratocytes. Here, we evaluated the in vitro effects of stimulation of the sGC enzyme with the cell-permeable pyrazolopyridinylpyrimidine compound BAY 41-2272 in modulating the TGFβ1-mediated profibrotic activation of human conjunctival fibroblasts. Cells were pretreated with the sGC stimulator before challenging with recombinant human TGFβ1, and subsequently assayed for viability, proliferation, migration, invasiveness, myofibroblast marker expression, and contractile properties. Stimulation of sGC significantly counteracted TGFβ1-induced cell proliferation, migration, invasiveness, and acquisition of a myofibroblast-like phenotype, as shown by a significant downregulation of FAP, ACTA2, COL1A1, COL1A2, FN1, MMP2, TIMP1, and TIMP2 mRNA levels, as well as by a significant reduction in α-smooth muscle actin, N-cadherin, COL1A1, and FN-EDA protein expression. In addition, pretreatment with the sGC stimulator was capable of significantly dampening TGFβ1-induced acquisition of a contractile phenotype by conjunctival fibroblasts, as well as phosphorylation of Smad3 and release of the proinflammatory cytokines IL-1β and IL-6. Taken together, our findings are the first to demonstrate the effectiveness of pharmacological sGC stimulation in counteracting conjunctival fibroblast-to-myofibroblast transition, thus providing a promising scientific background to further explore the feasibility of sGC stimulators as potential new adjuvant therapeutic compounds to treat conjunctival fibrotic conditions.

Residual ANTXR1+ myofibroblasts after chemotherapy inhibit anti-tumor immunity via YAP1 signaling pathway

Although cancer-associated fibroblast (CAF) heterogeneity is well-established, the impact of chemotherapy on CAF populations remains poorly understood. Here we address this question in high-grade serous ovarian cancer (HGSOC), in which we previously identified 4 CAF populations. While the global content in stroma increases in HGSOC after chemotherapy, the proportion of FAP+ CAF (also called CAF-S1) decreases. Still, maintenance of high residual CAF-S1 content after chemotherapy is associated with reduced CD8+ T lymphocyte density and poor patient prognosis, emphasizing the importance of CAF-S1 reduction upon treatment. Single cell analysis, spatial transcriptomics and immunohistochemistry reveal that the content in the ECM-producing ANTXR1+ CAF-S1 cluster (ECM-myCAF) is the most affected by chemotherapy. Moreover, functional assays demonstrate that ECM-myCAF isolated from HGSOC reduce CD8+ T-cell cytotoxicity through a Yes Associated Protein 1 (YAP1)-dependent mechanism. Thus, efficient inhibition after treatment of YAP1-signaling pathway in the ECM-myCAF cluster could enhance CD8+ T-cell cytotoxicity. Altogether, these data pave the way for therapy targeting YAP1 in ECM-myCAF in HGSOC.

PCSK9 regulates myofibroblast transformation through the JAK2/STAT3 pathway to regulate fibrosis after myocardial infarction

Cardiac fibrosis is pivotal in the progression of numerous cardiovascular diseases. This phenomenon is hallmarked by an excessive deposition of ECM protein secreted by myofibroblasts, leading to increased myocardial stiffness. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that belongs to the proprotein-converting enzyme family. It has emerged as a viable therapeutic target for reducing plasma low-density lipoprotein cholesterol. However, the exact mechanism via which PCSK9 impacts cardiac fibrosis remains unclear. In the present research, an increase in circulating PCSK9 protein levels was observed in individuals with myocardial infarction and rat models of myocardial infarction. Moreover, the inhibition of circulating PCSK9 in rats was found to reduce post-infarction fibrosis. In vitro experiments further demonstrated that overexpression of PCSK9 or stimulation by extracellular PCSK9 recombinant protein enhanced the transformation of cardiac fibroblasts to myofibroblasts. This process also elevated collagen Ⅰ, and Ⅲ, as well as α-SMA protein levels. However, these effects were countered when co-incubated with the STAT3 inhibitor S3I-201. This study suggests that PCSK9 may function as a novel regulator of myocardial fibrosis, primarily via the JAK2/STAT3 pathway.

Cavin-2 promotes fibroblast-to-myofibroblast trans-differentiation and aggravates cardiac fibrosis

AIMS

Transforming growth factor β (TGF-β) signalling is one of the critical pathways in fibroblast activation, and several drugs targeting the TGF-β/Smad signalling pathway in heart failure with cardiac fibrosis are being tested in clinical trials. Some caveolins and cavins, which are components of caveolae on the plasma membrane, are known for their association with the regulation of TGF-β signalling. Cavin-2 is particularly abundant in fibroblasts; however, the detailed association between Cavin-2 and cardiac fibrosis is still unclear. We tried to clarify the involvement and role of Cavin-2 in fibroblasts and cardiac fibrosis.

METHODS AND RESULTS

To clarify the role of Cavin-2 in cardiac fibrosis, we performed transverse aortic constriction (TAC) operations on four types of mice: wild-type (WT), Cavin-2 null (Cavin-2 KO), Cavin-2flox/flox , and activated fibroblast-specific Cavin-2 conditional knockout (Postn-Cre/Cavin-2flox/flox , Cavin-2 cKO) mice. We collected mouse embryonic fibroblasts (MEFs) from WT and Cavin-2 KO mice and investigated the effect of Cavin-2 in fibroblast trans-differentiation into myofibroblasts and associated TGF-β signalling. Four weeks after TAC, cardiac fibrotic areas in both the Cavin-2 KO and the Cavin-2 cKO mice were significantly decreased compared with each control group (WT 8.04 ± 1.58% vs. Cavin-2 KO 0.40 ± 0.03%, P < 0.01; Cavin-2flox/flox , 7.19 ± 0.50% vs. Cavin-2 cKO 0.88 ± 0.44%, P < 0.01). Fibrosis-associated mRNA expression (Col1a1, Ctgf, and Col3) was significantly attenuated in the Cavin-2 KO mice after TAC. α1 type I collagen deposition and non-vascular αSMA-positive cells (WT 43.5 ± 2.4% vs. Cavin-2 KO 25.4 ± 3.2%, P < 0.01) were reduced in the heart of the Cavin-2 cKO mice after TAC operation. The levels of αSMA protein (0.36-fold, P < 0.05) and fibrosis-associated mRNA expression (Col1a1, 0.69-fold, P < 0.01; Ctgf, 0.27-fold, P < 0.01; Col3, 0.60-fold, P < 0.01) were decreased in the Cavin-2 KO MEFs compared with the WT MEFs. On the other hand, αSMA protein levels were higher in the Cavin-2 overexpressed MEFs compared with the control MEFs (2.40-fold, P < 0.01). TGF-β1-induced Smad2 phosphorylation was attenuated in the Cavin-2 KO MEFs compared with WT MEFs (0.60-fold, P < 0.01). Heat shock protein 90 protein levels were significantly reduced in the Cavin-2 KO MEFs compared with the WT MEFs (0.69-fold, P < 0.01).

CONCLUSIONS

Cavin-2 loss suppressed fibroblast trans-differentiation into myofibroblasts through the TGF-β/Smad signalling. The loss of Cavin-2 in cardiac fibroblasts suppresses cardiac fibrosis and may maintain cardiac function.

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Liver fibrosis in NAFLD/NASH: from pathophysiology towards diagnostic and therapeutic strategies

Liver fibrosis, as an excess deposition of extracellular matrix (ECM) components, results from chronic liver injury as well as persistent activation of inflammatory response and of fibrogenesis. Liver fibrosis is a major determinant for chronic liver disease (CLD) progression and in the last two decades our understanding on the major molecular and cellular mechanisms underlying the fibrogenic progression of CLD has dramatically improved, boosting pre-clinical studies and clinical trials designed to find novel therapeutic approaches. From these studies several critical concepts have emerged, starting to reveal the complexity of the pro-fibrotic microenvironment which involves very complex, dynamic and interrelated interactions between different hepatic and extrahepatic cell populations. This review will offer first a recapitulation of established and novel pathophysiological basic principles and concepts by intentionally focus the attention on NAFLD/NASH, a metabolic-related form of CLD with a high impact on the general population and emerging as a leading cause of CLD worldwide. NAFLD/NASH-related pro-inflammatory and profibrogenic mechanisms will be analysed as well as novel information on cells, mediators and signalling pathways which have taken advantage from novel methodological approaches and techniques (single cell genomics, imaging mass cytometry, novel in vitro two- and three-dimensional models, etc.). We will next offer an overview on recent advancement in diagnostic and prognostic tools, including serum biomarkers and polygenic scores, to support the analysis of liver biopsies. Finally, this review will provide an analysis of current and emerging therapies for the treatment of NAFLD/NASH patients.

Sfrp1 inhibits lung fibroblast invasion during transition to injury-induced myofibroblasts

BACKGROUND

Fibroblast-to-myofibroblast conversion is a major driver of tissue remodelling in organ fibrosis. Distinct lineages of fibroblasts support homeostatic tissue niche functions, yet their specific activation states and phenotypic trajectories during injury and repair have remained unclear.

METHODS

We combined spatial transcriptomics, multiplexed immunostainings, longitudinal single-cell RNA-sequencing and genetic lineage tracing to study fibroblast fates during mouse lung regeneration. Our findings were validated in idiopathic pulmonary fibrosis patient tissues in situ as well as in cell differentiation and invasion assays using patient lung fibroblasts. Cell differentiation and invasion assays established a function of SFRP1 in regulating human lung fibroblast invasion in response to transforming growth factor (TGF)β1.

MEASUREMENTS AND MAIN RESULTS

We discovered a transitional fibroblast state characterised by high Sfrp1 expression, derived from both Tcf21-Cre lineage positive and negative cells. Sfrp1 + cells appeared early after injury in peribronchiolar, adventitial and alveolar locations and preceded the emergence of myofibroblasts. We identified lineage-specific paracrine signals and inferred converging transcriptional trajectories towards Sfrp1 + transitional fibroblasts and Cthrc1 + myofibroblasts. TGFβ1 downregulated SFRP1 in noninvasive transitional cells and induced their switch to an invasive CTHRC1+ myofibroblast identity. Finally, using loss-of-function studies we showed that SFRP1 modulates TGFβ1-induced fibroblast invasion and RHOA pathway activity.

CONCLUSIONS

Our study reveals the convergence of spatially and transcriptionally distinct fibroblast lineages into transcriptionally uniform myofibroblasts and identifies SFRP1 as a modulator of TGFβ1-driven fibroblast phenotypes in fibrogenesis. These findings are relevant in the context of therapeutic interventions that aim at limiting or reversing fibroblast foci formation.

MyD88 in myofibroblasts enhances nonalcoholic fatty liver disease-related hepatocarcinogenesis via promoting macrophage M2 polarization

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver diseases and has emerged as the leading factor in the pathogenesis of hepatocellular carcinoma (HCC). MyD88 contributes to the development of HCC. However, the underlying mechanism by which MyD88 in myofibroblasts regulates NAFLD-associated liver cancer development remains unknown.

RESULTS

Myofibroblast MyD88-deficient (SMAMyD88-/-) mice were protected from diet-induced obesity and developed fewer and smaller liver tumors. MyD88 deficiency in myofibroblasts attenuated macrophage M2 polarization and fat accumulation in HCC tissues. Mechanistically, MyD88 signaling in myofibroblasts enhanced CCL9 secretion, thereby promoting macrophage M2 polarization. This process may depend on the CCR1 receptor and STAT6/ PPARβ pathway. Furthermore, liver tumor growth was attenuated in mice treated with a CCR1 inhibitor. CCLl5 (homologous protein CCL9 in humans) expression was increased in myofibroblasts of HCC and was associated with shorter survival of patients with HCC. Thus, our results indicate that MyD88 in myofibroblasts promotes NAFLD-related HCC progression and may be a promising therapeutic target for HCC treatment.

CONCLUSION

This study demonstrates that MyD88 in myofibroblasts can promote nonalcoholic fatty liver disease-related hepatocarcinogenesis by enhancing macrophage M2 polarization, which might provide a potential molecular therapeutic target for HCC.

WNT-dependent interaction between inflammatory fibroblasts and FOLR2+ macrophages promotes fibrosis in chronic kidney disease

Chronic kidney disease (CKD) is a public health problem driven by myofibroblast accumulation, leading to interstitial fibrosis. Heterogeneity is a recently recognized characteristic in kidney fibroblasts in CKD, but the role of different populations is still unclear. Here, we characterize a proinflammatory fibroblast population (named CXCL-iFibro), which corresponds to an early state of myofibroblast differentiation in CKD. We demonstrate that CXCL-iFibro co-localize with macrophages in the kidney and participate in their attraction, accumulation, and switch into FOLR2+ macrophages from early CKD stages on. In vitro, macrophages promote the switch of CXCL-iFibro into ECM-secreting myofibroblasts through a WNT/β-catenin-dependent pathway, thereby suggesting a reciprocal crosstalk between these populations of fibroblasts and macrophages. Finally, the detection of CXCL-iFibro at early stages of CKD is predictive of poor patient prognosis, which shows that the CXCL-iFibro population is an early player in CKD progression and demonstrates the clinical relevance of our findings.

Integrin αV mediated activation of myofibroblast via mechanoparacrine of transforming growth factor β1 in promoting fibrous scar formation after myocardial infarction

BACKGROUND

Myocardial infarction (MI) dramatically changes the mechanical stress, which is intensified by the fibrotic remodeling. Integrins, especially the αV subunit, mediate mechanical signal and mechanoparacrine of transforming growth factor β1 (TGF-β1) in various organ fibrosis by activating CFs into myofibroblasts (MFBs). We investigated a possible role of integrin αV mediated mechanoparacrine of TGF-β1 in MFBs activation for fibrous reparation in mice with MI.

METHODS

Heart samples from MI, sham, or MI plus cilengitide (14 mg/kg, specific integrin αV inhibitor) treated mice, underwent functional and morphological assessments by echocardiography, and histochemistry on 7, 14 and 28 days post-surgery. The mechanical and ultrastructural changes of the fibrous scar were further evaluated by atomic mechanics microscope (AFM), immunofluorescence, second harmonic generation (SHG) imaging, polarized light and scanning electron microscope, respectively. Hydroxyproline assay was used for total collagen content, and western blot for protein expression profile examination. Fibroblast bioactivities, including cell shape, number, Smad2/3 signal and expression of extracellular matrix (ECM) related proteins, were further evaluated by microscopic observation and immunofluorescence in polyacrylamide (PA) hydrogel with adjustable stiffness, which was re-explored in fibroblast cultured on stiff matrix after silencing of integrin αV. The content of total and free TGF-β1 was tested by enzyme-linked immunosorbent assay (ELISA) in both infarcted tissue and cell samples.

RESULT

Increased stiffness with heterogeneity synchronized with integrin αV and alpha smooth muscle actin (α-SMA) positive MFBs accumulation in those less mature fibrous areas. Cilengitide abruptly reduced collagen content and disrupted collagen alignment, which also decreased TGF-β1 bioavailability, Smad2/3 phosphorylation, and α-SMA expression in the fibrous area. Accordingly, fibroblast on stiff but not soft matrix exhibited obvious MFB phenotype, as evidenced by enlarged cell, hyperproliferation, well-developed α-SMA fibers, and elevated ECM related proteins, while silencing of integrin αV almost abolished this switch via attenuating paracrine of TGF-β1 and nuclear translocation of Smad2/3.

CONCLUSION

This study illustrated that increased tissue stiffness activates CFs into MFBs by integrin αV mediated mechanoparacrine of TGF-β1, especially in immature scar area, which ultimately promotes fibrous scar maturation.

H3K18 lactylation promotes the progression of arsenite-related idiopathic pulmonary fibrosis via YTHDF1/m6A/NREP

As epigenetic modifications, lactylation and N6-methyladenosine (m6A) have attracted wide attention. Arsenite is an environmental pollutant that has been proven to induce idiopathic pulmonary fibrosis (IPF). However, the molecular mechanisms of lactylation and m6A methylation are unclear in arsenite-related IPF (As-IPF). In view of the limited understanding of molecular mechanism of m6A and lactylation in As-IPF, MeRIP-seq, RNA-seq and ChIP-seq were analyzed to verify the target gene regulated by m6A and H3K18 lactylation (H3K18la). We found that, for As-IPF, the global levels of m6A, levels of YTHDF1 and m6A-modified neuronal protein 3.1 (NREP) were elevated in alveolar epithelial cells (AECs). The secretion levels of TGF-β1 were increased via YTHDF1/m6A/NREP, which promoted the fibroblast-to-myofibroblast transition (FMT). Further, extracellular lactate from myofibroblasts elevated levels of the global lactylation (Kla) and H3K18la via the lactate monocarboxylate transporter 1 (MCT1), and, in AECs, H3K18la facilitated the transcription of Ythdf1. This report highlights the role of crosstalk between AECs and myofibroblasts via lactylation and m6A and the significance of H3K18la regulation of YTHDF1 in the progression of As-IPF, which may be useful for finding effective therapeutic targets.

Systems-based identification of the Hippo pathway for promoting fibrotic mesenchymal differentiation in systemic sclerosis

Systemic sclerosis (SSc) is a devastating autoimmune disease characterized by excessive production and accumulation of extracellular matrix, leading to fibrosis of skin and other internal organs. However, the main cellular participants in SSc skin fibrosis remain incompletely understood. Here using differentiation trajectories at a single cell level, we demonstrate a dual source of extracellular matrix deposition in SSc skin from both myofibroblasts and endothelial-to-mesenchymal-transitioning cells (EndoMT). We further define a central role of Hippo pathway effectors in differentiation and homeostasis of myofibroblast and EndoMT, respectively, and show that myofibroblasts and EndoMTs function as central communication hubs that drive key pro-fibrotic signaling pathways in SSc. Together, our data help characterize myofibroblast differentiation and EndoMT phenotypes in SSc skin, and hint that modulation of the Hippo pathway may contribute in reversing the pro-fibrotic phenotypes in myofibroblasts and EndoMTs.

Identification of Periostin as a critical niche for myofibroblast dynamics and fibrosis during tendon healing

Tendon injuries are a major clinical problem, with poor patient outcomes caused by abundant scar tissue deposition during healing. Myofibroblasts play a critical role in the initial restoration of structural integrity after injury. However, persistent myofibroblast activity drives the transition to fibrotic scar tissue formation. As such, disrupting myofibroblast persistence is a key therapeutic target. While myofibroblasts are typically defined by the presence of αSMA+ stress fibers, αSMA is expressed in other cell types including the vasculature. As such, modulation of myofibroblast dynamics via disruption of αSMA expression is not a translationally tenable approach. Recent work has demonstrated that Periostin-lineage (PostnLin) cells are a precursor for cardiac fibrosis-associated myofibroblasts. In contrast to this, here we show that PostnLin cells contribute to a transient αSMA+ myofibroblast population that is required for functional tendon healing, and that Periostin forms a supportive matrix niche that facilitates myofibroblast differentiation and persistence. Collectively, these data identify the Periostin matrix niche as a critical regulator of myofibroblast fate and persistence that could be targeted for therapeutic manipulation to facilitate regenerative tendon healing.

Prenatal FGFR2 Signaling via PI3K/AKT Specifies the PDGFRA+ Myofibroblast

It is well known that FGFR2 (fibroblast growth factor receptor 2) signaling is critical for proper lung development. Recent studies demonstrate that epithelial FGFR2 signaling during the saccular phase of lung development (sacculation) regulates alveolar type 1 (AT1) and AT2 cell differentiation. During sacculation, PDGFRA (platelet-derived growth factor receptor-α)-positive lung fibroblasts exist as three functional subtypes: contractile myofibroblasts, extracellular matrix-producing matrix fibroblasts, and lipofibroblasts. All three subtypes are required during alveolarization to establish a niche that supports AT2 epithelial cell self-renewal and AT1 epithelial cell differentiation. FGFR2 signaling directs myofibroblast differentiation in PDGFRA+ fibroblasts during alveolar reseptation after pneumonectomy. However, it remains unknown if FGFR2 signaling regulates PDGFRA+ myo-, matrix, or lipofibroblast differentiation during sacculation. In this study, FGFR2 signaling was inhibited by temporal expression of a secreted dominant-negative FGFR2b (dnFGFR2) by AT2 cells from embryonic day (E) 16.5 to E18.5. Fibroblast and epithelial differentiation were analyzed at E18.5 and postnatal days 7 and 21. At all time points, the number of myofibroblasts was reduced and the number of lipo-/matrix fibroblasts was increased. AT2 cells are increased and AT1 cells are reduced postnatally, but not at E18.5. Similarly, in organoids made with PDGFRA+ fibroblasts from dnFGFR2 lungs, increased AT2 cells and reduced AT1 cells were observed. In vitro treatment of primary wild-type E16.5 adherent saccular lung fibroblasts with recombinant dnFGFR2b/c resulted in reduced myofibroblast contraction. Treatment with the PI3K/AKT activator 740 Y-P rescued the lack of myofibroblast differentiation caused by dnFGFR2b/2c. Moreover, treatment with the PI3K/AKT activator 740 Y-P rescued myofibroblast differentiation in E18.5 fibroblasts isolated from dnFGFR2 lungs.

Intermittent actuation attenuates fibrotic behaviour of myofibroblasts

The foreign body response (FBR) to implanted materials culminates in the deposition of a hypo-permeable, collagen rich fibrotic capsule by myofibroblast cells at the implant site. The fibrotic capsule can be deleterious to the function of some medical implants as it can isolate the implant from the host environment. Modulation of fibrotic capsule formation has been achieved using intermittent actuation of drug delivery implants, however the mechanisms underlying this response are not well understood. Here, we use analytical, computational, and in vitro models to understand the response of human myofibroblasts (WPMY-1 stromal cell line) to intermittent actuation using soft robotics and investigate how actuation can alter the secretion of collagen and pro/anti-inflammatory cytokines by these cells. Our findings suggest that there is a mechanical loading threshold that can modulate the fibrotic behaviour of myofibroblasts, by reducing the secretion of soluble collagen, transforming growth factor beta-1 and interleukin 1-beta, and upregulating the anti-inflammatory interleukin-10. By improving our understanding of how cells involved in the FBR respond to mechanical actuation, we can harness this technology to improve functional outcomes for a wide range of implanted medical device applications including drug delivery and cell encapsulation platforms. STATEMENT OF SIGNIFICANCE: A major barrier to the successful clinical translation of many implantable medical devices is the foreign body response (FBR) and resultant deposition of a hypo-permeable fibrotic capsule (FC) around the implant. Perturbation of the implant site using intermittent actuation (IA) of soft-robotic implants has previously been shown to modulate the FBR and reduce FC thickness. However, the mechanisms of action underlying this response were largely unknown. Here, we investigate how IA can alter the activity of myofibroblast cells, and ultimately suggest that there is a mechanical loading threshold within which their fibrotic behaviour can be modulated. These findings can be harnessed to improve functional outcomes for a wide range of medical implants, particularly drug delivery and cell encapsulation devices.

A novel mechanoeffector role of fibroblast S100A4 in myofibroblast transdifferentiation and fibrosis

Fibroblast to myofibroblast transdifferentiation mediates numerous fibrotic disorders, such as idiopathic pulmonary fibrosis (IPF). We have previously demonstrated that non-muscle myosin II (NMII) is activated in response to fibrotic lung extracellular matrix, thereby mediating myofibroblast transdifferentiation. NMII-A is known to interact with the calcium-binding protein S100A4, but the mechanism by which S100A4 regulates fibrotic disorders is unclear. In this study, we show that fibroblast S100A4 is a calcium-dependent, mechanoeffector protein that is uniquely sensitive to pathophysiologic-range lung stiffness (8-25 kPa) and thereby mediates myofibroblast transdifferentiation. Re-expression of endogenous fibroblast S100A4 rescues the myofibroblastic phenotype in S100A4 KO fibroblasts. Analysis of NMII-A/actin dynamics reveals that S100A4 mediates the unraveling and redistribution of peripheral actomyosin to a central location, resulting in a contractile myofibroblast. Furthermore, S100A4 loss protects against murine in vivo pulmonary fibrosis, and S100A4 expression is dysregulated in IPF. Our data reveal a novel mechanosensor/effector role for endogenous fibroblast S100A4 in inducing cytoskeletal redistribution in fibrotic disorders such as IPF.

Comprehensive modular analyses of scar subtypes illuminate underlying molecular mechanisms and potential therapeutic targets

Pathological scarring resulting from traumas and wounds, such as hypertrophic scars and keloids, pose significant aesthetic, functional and psychological challenges. This study provides a comprehensive transcriptomic analysis of these conditions, aiming to illuminate underlying molecular mechanisms and potential therapeutic targets. We employed a co-expression and module analysis tool to identify significant gene clusters associated with distinct pathophysiological processes and mechanisms, notably lipid metabolism, sebum production, cellular energy metabolism and skin barrier function. This examination yielded critical insights into several skin conditions including folliculitis, skin fibrosis, fibrosarcoma and congenital ichthyosis. Particular attention was paid to Module Cluster (MCluster) 3, encompassing genes like BLK, TRPV1 and GABRD, all displaying high expression and potential implications in immune modulation. Preliminary immunohistochemistry validation supported these findings, showing elevated expression of these genes in non-fibrotic samples rich in immune activity. The complex interplay of different cell types in scar formation, such as fibroblasts, myofibroblasts, keratinocytes and mast cells, was also explored, revealing promising therapeutic strategies. This study underscores the promise of targeted gene therapy for pathological scars, paving the way for more personalised therapeutic approaches. The results necessitate further research to fully ascertain the roles of these identified genes and pathways in skin disease pathogenesis and potential therapeutics. Nonetheless, our work forms a strong foundation for a new era of personalised medicine for patients suffering from pathological scarring.

Studying Monocyte-Myofibroblast Immunomodulation in a 3D Co-culture System

Simple and reproducible 3D cell culture systems that mimic biological interactions within physiological tissues (biomimetics) can provide unique insight for scientific inquiries compared to 2D cell cultures. Fibroblast-populated collagen lattices (FPCLs) are commonly used for mimicking physiological collagen matrices, potentiating biomechanical stresses on embedded fibroblasts. Here, we describe a novel 3D co-culture model that incorporates human Tenon's capsule fibroblasts embedded in FPCLs co-cultured with THP-1 monocytes suspended in culture media. This method can be used for the assessment of cell-cell interactions in various stages of the wound healing process and can facilitate various types of immune cells in co-culture. This system can also be used to study pharmacological agents that may eventually improve clinical outcomes in patients affected by inflammatory disorders.

Hematopoietic Transcription Factor RUNX1 is Essential for Promoting Macrophage-Myofibroblast Transition in Non-Small-Cell Lung Carcinoma

Macrophage-myofibroblast transition (MMT) is a newly discovered pathway for mass production of pro-tumoral cancer-associated fibroblasts (CAFs) in non-small cell lung carcinoma (NSCLC) in a TGF-β1/Smad3 dependent manner. Better understanding its regulatory signaling in tumor microenvironment (TME) may identify druggable target for the development of precision medicine. Here, by dissecting the transcriptome dynamics of tumor-associated macrophage at single-cell resolution, a crucial role of a hematopoietic transcription factor Runx1 in MMT formation is revealed. Surprisingly, integrative bioinformatic analysis uncovers Runx1 as a key regulator in the downstream of MMT-specific TGF-β1/Smad3 signaling. Stromal Runx1 level positively correlates with the MMT-derived CAF abundance and mortality in NSCLC patients. Mechanistically, macrophage-specific Runx1 promotes the transcription of genes related to CAF signatures in MMT cells at genomic level. Importantly, macrophage-specific genetic deletion and systemic pharmacological inhibition of TGF-β1/Smad3/Runx1 signaling effectively prevent MMT-driven CAF and tumor formation in vitro and in vivo, representing a potential therapeutic target for clinical NSCLC.

TGFβ1-driven SMAD2/3 phosphorylation and myofibroblast emergence are fully dependent on the TGFβ1 pre-activation of MAPKs and controlled by maternal leucine zipper kinase

Following wounding, endogenously secreted TGFβs drive resident and bone marrow-derived cells to convert into α-smooth actin (SMA)-rich, contractile myofibroblasts. The TGFβ effect is initiated by the phosphorylation of SMADs 2 and 3 (SMAD2/3). This event has been referred to as the canonical response to TGFβ. TGFβ also elicits other responses viewed as parallel events not directly connected to the SMAD activation, and thus referred to as noncanonical. A recognized response is the phosphorylation of the -activated kinase (TAK1/MAP3K), an upstream component of the mitogen-activated protein kinase (MAPK) cascade. We have now examined the relationship between these two effects of TGFβ1 at their earliest stages. The bulk of the studies were carried out with primary fibroblasts derived from the human cornea. The results' widespread relevance was confirmed in critical experiments with dermal-, and Tenon's capsule-derived fibroblasts. Cells were treated with kinase inhibitors or targeting siRNAs followed by induction by 2 ng/ml TGFβ1, and/or 10 ng/ml TNF-α. Cells were collected after 1 to 30 min for Western blot analysis and assayed for the accumulation of phosphorylated TAK1, ASK1, JNK1/2, p38, HPS27, MELK, SMAD2/3, and GAPDH. The effect of the kinase inhibitors on α-SMA expression and α-SMA stress fiber organization was also tested. For the immediate response to TGFβ1 we found that a) activation of the MAPK pathway was completed within 1 min after the addition of TGFβ1; b) phosphorylation of JNK1/2 was fully dependent on TAK1 and ASK1 activity, c) phosphorylation of MELK was fully dependent on JNK1/2 activity; d) phosphorylation of ASK1 depends on MELK activity, indicating the existence of an ASK1-MELK positive activation feedback loop; e) phosphorylation of SMAD2/3 started only after a 5 min period and reached a nadir after 10-15 min, f) the latter phosphorylation was fully blocked by inhibition of TAK1, ASK1, JNK1/2, and MELK, and siRNA-driven MELK downregulation; g) the inhibitors equally blocked the α-SMA protein expression, stress fiber development, and cell morphology changes at 72 h. These results demonstrate that the activation of the canonical pathway is fully subordinate to the activity of the MAPK pathway, challenging the concept of canonical and noncanonical TGFβ pathways and that SMAD2/3 activation is mediated by MELK, a kinase not previously associated with rapid pharmacological responses.

Promotion of myofibroblast differentiation through repeated treatment of fibroblasts to low concentrations of PM2.5

Exposure to particulate matter ≤ 2.5 µm (PM2.5) is a risk factor for many lung diseases. Although the toxicologic effects of PM2.5 on airway epithelium are well-described, the effects of PM2.5 on fibroblasts in the lung are less studied. Here, we sought to examine the effects of PM2.5 on the differentiation of fibroblasts into myofibroblasts. Although a single treatment of fibroblasts did not result in a change in collagen or the myofibroblast marker α-SMA, exposing fibroblasts to sequential treatments with PM2.5 at low concentrations caused a robust increase in these proteins. Treatment of fibroblasts with IMD0354, an inhibitor to nuclear factor κB, but not with an antagonist to aryl hydrocarbon receptor, abolished the ability of PM2.5 to induce myofibroblast differentiation. These data demonstrate that potential impact of PM2.5 to fibroblast activation and fibrosis and support the importance of utilizing low concentrations and varying exposure protocols to toxicologic studies.

Opposing roles for ADAMTS2 and ADAMTS14 in myofibroblast differentiation and function

Crosstalk between cancer and stellate cells is pivotal in pancreatic cancer, resulting in differentiation of stellate cells into myofibroblasts that drives tumour progression. To assess cooperative mechanisms in a 3D context, we generated chimeric spheroids using human and mouse cancer and stellate cells. Species-specific deconvolution of bulk-RNA sequencing data revealed cell type-specific transcriptomes underpinning invasion. This dataset highlighted stellate-specific expression of transcripts encoding the collagen-processing enzymes ADAMTS2 and ADAMTS14. Strikingly, loss of ADAMTS2 reduced, while loss of ADAMTS14 promoted, myofibroblast differentiation and invasion independently of their primary role in collagen-processing. Functional and proteomic analysis demonstrated that these two enzymes regulate myofibroblast differentiation through opposing roles in the regulation of transforming growth factor β availability, acting on the protease-specific substrates, Serpin E2 and fibulin 2, for ADAMTS2 and ADAMTS14, respectively. Showcasing a broader complexity for these enzymes, we uncovered a novel regulatory axis governing malignant behaviour of the pancreatic cancer stroma. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Human left ventricular cardiac fibroblasts undergo a dynamic shift in secretome and gene expression toward a cardiac myofibroblast phenotype during early passage in typical culture expansion conditions

Cardiac fibroblasts (CFs) are critical components of the cardiac niche and primarily responsible for assembly and maintenance of the cardiac extracellular matrix (ECM). CFs are increasingly of interest for tissue engineering and drug development applications, as they provide synergistic support to cardiomyocytes through direct cell-to-cell signaling and cell-to-ECM interactions via soluble factors, including cytokines, growth factors and extracellular vesicles. CFs can be activated to a cardiac myofibroblast (CMF) phenotype upon injury or stimulation with transforming growth factor beta 1. Once activated, CMFs assemble collagen-rich ECM, which is vitally important to stabilize scar formation following myocardial infarction, for example. Although there is greater experience with culture expansion of CFs among non-human strains, very little is known about human CF-to-CMF transitions and expression patterns during culture expansion. In this study, we evaluated for shifts in inflammatory and angiogenic expression profiles of human CFs in typical culture expansion conditions. Understanding shifts in cellular expression patterns during CF culture expansion is critically important to establish quality benchmarks and optimize large-scale manufacturing for future clinical applications.

Anoctamin-1 is induced by TGF-β and contributes to lung myofibroblast differentiation

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by progressive scarring of the lungs and resulting in deterioration in lung function. Transforming growth factor-β (TGF-β) is one of the most established drivers of fibrotic processes. TGF-β promotes the transformation of tissue fibroblasts to myofibroblasts, a key finding in the pathogenesis of pulmonary fibrosis. We report here that TGF-β robustly upregulates the expression of the calcium-activated chloride channel anoctamin-1 (ANO1) in human lung fibroblasts (HLFs) at mRNA and protein levels. ANO1 is readily detected in fibrotic areas of IPF lungs in the same area with smooth muscle α-actin (SMA)-positive myofibroblasts. TGF-β-induced myofibroblast differentiation (determined by the expression of SMA, collagen-1, and fibronectin) is significantly inhibited by a specific ANO1 inhibitor, T16Ainh-A01, or by siRNA-mediated ANO1 knockdown. T16Ainh-A01 and ANO1 siRNA attenuate profibrotic TGF-β signaling, including activation of RhoA pathway and AKT, without affecting initial Smad2 phosphorylation. Mechanistically, TGF-β treatment of HLFs results in a significant increase in intracellular chloride levels, which is prevented by T16Ainh-A01 or by ANO1 knockdown. The downstream mechanism involves the chloride-sensing "with-no-lysine (K)" kinase (WNK1). WNK1 siRNA significantly attenuates TGF-β-induced myofibroblast differentiation and signaling (RhoA pathway and AKT), whereas the WNK1 kinase inhibitor WNK463 is largely ineffective. Together, these data demonstrate that 1) ANO1 is a TGF-β-inducible chloride channel that contributes to increased intracellular chloride concentration in response to TGF-β; and 2) ANO1 mediates TGF-β-induced myofibroblast differentiation and fibrotic signaling in a manner dependent on WNK1 protein but independent of WNK1 kinase activity.NEW & NOTEWORTHY This study describes a novel mechanism of differentiation of human lung fibroblasts (HLFs) to myofibroblasts: the key process in the pathogenesis of pulmonary fibrosis. Transforming growth factor-β (TGF-β) drives the expression of calcium-activated chloride channel anoctmin-1 (ANO1) leading to an increase in intracellular levels of chloride. The latter recruits chloride-sensitive with-no-lysine (K) kinase (WNK1) to activate profibrotic RhoA and AKT signaling pathways, possibly through activation of mammalian target of rapamycin complex-2 (mTORC2), altogether promoting myofibroblast differentiation.

The chromatin remodeling protein BRG1 regulates HSC-myofibroblast differentiation and liver fibrosis

Excessive fibrogenic response in the liver disrupts normal hepatic anatomy and function heralding such end-stage liver diseases as hepatocellular carcinoma and cirrhosis. Myofibroblasts, derived primarily from hepatic stellate cells (HSCs), are the effector of liver fibrosis. In the present study we investigated the mechanism by which Brahma-related gene 1 (BRG1, encoded by Smarca4) regulates HSC-myofibroblast transition and the implication in intervention against liver fibrosis. We report that BRG1 expression was elevated during HSC maturation in cell culture, in animal models, and in human cirrhotic liver biopsy specimens. HSC-specific deletion of BRG1 attenuated liver fibrosis in several different animal models. In addition, BRG1 ablation in myofibroblasts ameliorated liver fibrosis. RNA-seq identified IGFBP5 as a novel target for BRG1. Over-expression of IGFBP5 partially rescued the deficiency in myofibroblast activation when BRG1 was depleted. On the contrary, IGFBP5 knockdown suppressed HSC-myofibroblast transition in vitro and mollified liver fibrosis in mice. Mechanistically, IGFBP5 interacted with Bat3 to stabilize the Bat3-TβR complex and sustain TGF-β signaling. In conclusion, our data provide compelling evidence that BRG1 is a pivotal regulator of liver fibrosis by programming HSC-myofibroblast transition.

Development of accessible platforms to promote myofibroblast differentiation by playing on hydrogel scaffold composition

Mechanomimetic materials are particularly attractive for modeling in vitro fibroblast to myofibroblast (Myof) transition, a key process in the physiological repair of damaged tissue, and recognized as the core cellular mechanism of pathological fibrosis in different organs. In vivo, mechanical stimuli from the extracellular matrix (ECM) are crucial, together with cell-cell contacts and the pro-fibrotic transforming growth factor (TGF)-β1, in promoting fibroblast differentiation. Here, we explore the impact of hydrogels made by polyacrylamide with different composition on fibroblast behavior. By appropriate modulation of the hydrogel composition (e.g. adjusting the crosslinker content), we produce and fully characterize three kinds of scaffolds with different Young modulus (E). We observe that soft hydrogels (E < 1 kPa) induced fibroblast differentiation better than stiffer ones, also in the absence of TGF-β1. This study provides a readily accessible biomaterial platform to promote Myof generation. The easy approach used and the commercial availability of the monomers make these hydrogels suitable to a wide range of biomedical applications combined with high reproducibility and simple preparation protocols.

Profibrotic COVID-19 subphenotype exhibits enhanced localized ER-dependent HSP47+ expression in cardiac myofibroblasts in situ

We recently described a subgroup of autopsied COVID-19 subjects (∼40%), termed 'profibrotic phenotype,' who exhibited clusters of myofibroblasts (Mfbs), which were positive for the collagen-specific chaperone heat shock protein 47 (HSP47+) in situ. This report identifies increased, localized (hot spot restricted) expression of αSMA, COLα1, POSTN and FAP supporting the identity of HSP47+ cells as myofibroblasts and characterizing a profibrotic extracellular matrix (ECM) phenotype. Coupled with increased GRP78 in COVID-19 subjects, these data could reflect induction of the unfolded protein response for mitigation of proteostasis (i.e., protein homeostasis) dysfunction in discrete clusters of cells. ECM shifts in selected COVID-19 subjects occur without significant increases in either global trichrome positive staining or myocardial injury based quantitively on standard H&E scoring. Our findings also suggest distinct mechanism(s) for ECM remodeling in the setting of SARS-CoV-2 infection. The ratio of CD163+/CD68+ cells is increased in hot spots of profibrotic hearts compared with either controls or outside of hot spots in COVID-19 subjects. In sum, matrix remodeling of human COVID-19 hearts in situ is characterized by site-restricted profibrotic mediated (e.g., HSP47+ Mfbs, CD163+ Mφs) modifications in ECM (i.e., COLα1, POSTN, FAP), with a strong correlation between COLα1 and HSP47+cells within hot spots. Given the established associations of viral infection (e.g., human immunodeficiency virus; HIV), myocardial fibrosis and sudden cardiac death, early screening tools (e.g., plasma biomarkers, noninvasive cardiac magnetic resonance imaging) for diagnosis, monitoring and treatment of fibrotic ECM remodeling are warranted for COVID-19 high-risk populations.

Defining the molecular fingerprint of bladder and kidney fibroblasts

Fibroblasts are integral to the organization and function of all organs and play critical roles in pathologies such as fibrosis; however, we have limited understanding of the fibroblasts that populate the bladder and kidney. In this review, I describe how transcriptomics is leading to a revolution in our understanding of fibroblast biology by defining the molecular fingerprint (i.e., transcriptome) of universal and specialized fibroblast types, revealing gene signatures that allows one to resolve fibroblasts from other mesenchymal cell types, and providing a new comprehension of the fibroblast lineage. In the kidney, transcriptomics is giving us new insights into the molecular fingerprint of kidney fibroblasts, including those for cortical fibroblasts, medullary fibroblasts, and erythropoietin (EPO)-producing Norn fibroblasts, as well as new information about the gene signatures of kidney myofibroblasts and the transition of kidney fibroblasts into myofibroblasts. Transcriptomics has also revealed that the major cell type in the bladder interstitium is the fibroblast, and that multiple fibroblast types, each with their own molecular fingerprint, are found in the bladder wall. Interleaved throughout is a discussion of how transcriptomics can drive our future understanding of fibroblast identification, diversity, function, and their roles in bladder and kidney biology and physiology in health and in disease states.