Wnt coreceptor Lrp5 is a driver of idiopathic pulmonary fibrosis

Targeting SOCS2 alleviates myocardial fibrosis by reducing nuclear translocation of β-catenin

BACKGROUND

Myocardial fibrosis is an important pathological feature of dilated cardiomyopathy (DCM). The roles of SOCS2 in fibrosis of different organs are controversial. Herein, we investigated the function and potential mechanism of SOCS2 in myocardial fibrosis.

METHODS

Bioinformatics, immunohistochemistry (IHC), immunofluorescence (IF), western blot (WB), real-time fluorescence quantitative PCR (qPCR), rat primary myocardial fibroblasts (rCFs) culture, doxorubicin (DOX) induced mouse dilated cardiomyopathy (DCM) model, and in vivo adeno-associated virus (AAV) infection were used to explore the role of SOCS2 in DCM.

RESULTS

Bioinformatics analysis showed that SOCS2 was positively correlated with fibrosis related factors. SOCS2 was significantly upregulated in patients and mice with DCM. In vivo experiments showed that targeted inhibition of cardiac SOCS2 could improve mouse cardiac function and alleviate myocardial fibrosis. Further research demonstrated that SOCS2 promoted the transformation of myofibroblasts. Knockdown of SOCS2 reduced the nuclear localization of β-catenin, which inhibited the fibrogenic effect of Wnt/β-catenin pathway. In addition, bioinformatics analysis suggested that lymphoid enhancer binding factor 1 (LEF1) was significantly positively correlated with SOCS2. Finally, dual luciferase assays demonstrated that LEF1 could bind to the promoter region of SOCS2, thereby mediating its transcriptional activation.

CONCLUSION

SOCS2 could activate the Wnt/β-catenin by regulating the nuclear translocation of β-catenin, which induces the transcriptional activation of SOCS2. Overall, these results indicated a positive feedback activation phenomenon between SOCS2, β-catenin and LEF1 in DCM. These results suggested that inhibition of SOCS2 could effectively alleviate the progression of myocardial fibrosis and improve cardiac function.

CasRx-based Wnt activation promotes alveolar regeneration while ameliorating pulmonary fibrosis in a mouse model of lung injury

Wnt/β-catenin signaling is an attractive target for regenerative medicine. A powerful driver of stem cell activity and hence tissue regeneration, Wnt signaling can promote fibroblast proliferation and activation, leading to fibrosis, while prolonged Wnt signaling is potentially carcinogenic. Thus, to harness its therapeutic potential, the activation of Wnt signaling must be transient, reversible, and tissue specific. In the lung, Wnt signaling is essential for alveolar stem cell activity and alveolar regeneration, which is impaired in lung fibrosis. Activation of Wnt/β-catenin signaling in lung epithelium may have anti-fibrotic effects. Here, we used intratracheal adeno-associated virus 6 injection to selectively deliver CasRx into the lung epithelium, where it reversibly activates Wnt signaling by simultaneously degrading mRNAs encoding Axin1 and Axin2, negative regulators of Wnt/β-catenin signaling. Interestingly, CasRx-mediated Wnt activation specifically in lung epithelium not only promotes alveolar type II cell proliferation and alveolar regeneration but also inhibits lung fibrosis resulted from bleomycin-induced injury, relevant in both preventive and therapeutic settings. Our study offers an attractive strategy for treating pulmonary fibrosis, with general implications for regenerative medicine.

TGFβ1-Induced Fibrotic Responses of Conjunctival Fibroblasts through the Wnt/β-Catenin/CRYAB Signaling Pathway

Conjunctival fibrosis is a common postoperative complication of glaucoma filtration surgery, resulting in uncontrolled intraocular pressure and surgery failure. Therefore, there is an urgent need to understand the molecular mechanisms underlying conjunctival fibrosis and to explore novel pharmacologic anti-fibrosis therapies for glaucoma filtration surgery. Herein, the 4-dimensional data-independent acquisition (4D-DIA) quantitative proteomic results, coupled with experimental data, revealed the activation of the Wnt/β-catenin pathway in transforming growth factor (TGF)-β1-induced human conjunctival fibroblasts (HConFs). Treatment with ICG-001, a Wnt/β-catenin inhibitor, effectively inhibited cell proliferation and migration in TGFβ1-treated HConFs. ICG-001 treatment alleviated the increased generation of extracellular matrix proteins induced by TGFβ1. In addition, ICG-001 reduced the expression level of α smooth muscle actin (α-SMA) and inhibited cell contractility in TGFβ1-treated HConFs. Proteomics data further suggested that αB-crystallin (CRYAB) was a downstream target of Wnt/β-catenin, which was up-regulated by TGFβ1 and down-regulated by ICG-001. Immunoblotting assay also indicated that ICG-001 reduced the expressions of ubiquitin and β-catenin in TGFβ1-treated HConFs, implying that CRYAB stabilized β-catenin by inhibiting its ubiquitination degradation. Exogenous CRYAB promoted cell viability, increased extracellular matrix protein levels, and up-regulated α-SMA expression of HConFs under TGFβ1 stimulation. CRYAB rescued TGFβ1-induced fibrotic responses that were suppressed by ICG-001. In conclusion, this study elucidates the regulatory mechanism of the Wnt/β-catenin/CRYAB pathway in conjunctival fibrosis, offering promising therapeutic targets for mitigating bleb scarring after glaucoma filtration surgery.

5,7,3',4'-Tetramethoxyflavone suppresses TGF-β1-induced activation of murine fibroblasts in vitro and ameliorates bleomycin-induced pulmonary fibrosis in mice

OBJECTIVE

This study aimed to investigate the use of 5,7,3',4'-tetramethoxyflavone (TMF) to treat pulmonary fibrosis (PF), a chronic and fatal lung disease. In vitro and in vivo models were used to examine the impact of TMF on PF.

METHODS

NIH-3T3 (Mouse Embryonic Fibroblast) were exposed to transforming growth factor‑β1 (TGF-β1) and treated with or without TMF. Cell growth was assessed using the MTT method, and cell migration was evaluated with the scratch wound assay. Protein and messenger ribonucleic acid (mRNA) levels of extracellular matrix (ECM) genes were analyzed by western blotting and quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Downstream molecules affected by TGF-β1 were examined by western blotting. In vivo, mice with bleomycin-induced PF were treated with TMF, and lung tissues were analyzed with staining techniques.

RESULTS

The in vitro results showed that TMF had no significant impact on cell growth or migration. However, it effectively inhibited myofibroblast activation and ECM production induced by TGF-β1 in NIH-3T3 cells. This inhibition was achieved by suppressing various signaling pathways, including Smad, mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase/AKT (PI3K/AKT), and WNT/β-catenin. The in vivo experiments demonstrated the therapeutic potential of TMF in reducing PF induced by bleomycin in mice, and there was no significant liver or kidney toxicity observed.

CONCLUSION

These findings suggest that TMF has the potential to effectively inhibit myofibroblast activation and could be a promising treatment for PF. TMF achieves this inhibitory effect by targeting TGF-β1/Smad and non-Smad pathways.

A WNT mimetic with broad spectrum FZD-specificity decreases fibrosis and improves function in a pulmonary damage model

BACKGROUND

Wnt/β-catenin signaling is critical for lung development and AT2 stem cell maintenance in adults, but excessive pathway activation has been associated with pulmonary fibrosis, both in animal models and human diseases such as idiopathic pulmonary fibrosis (IPF). IPF is a detrimental interstitial lung disease, and although two approved drugs limit functional decline, transplantation is the only treatment that extends survival, highlighting the need for regenerative therapies.

METHODS

Using our antibody-based platform of Wnt/β-catenin modulators, we investigated the ability of a pathway antagonist and pathway activators to reduce pulmonary fibrosis in the acute bleomycin model, and we tested the ability of a WNT mimetic to affect alveolar organoid cultures.

RESULTS

A WNT mimetic agonist with broad FZD-binding specificity (FZD1,2,5,7,8) potently expanded alveolar organoids. Upon therapeutic dosing, a broad FZD-binding specific Wnt mimetic decreased pulmonary inflammation and fibrosis and increased lung function in the bleomycin model, and it impacted multiple lung cell types in vivo.

CONCLUSIONS

Our results highlight the unexpected capacity of a WNT mimetic to effect tissue repair after lung damage and support the continued development of Wnt/β-catenin pathway modulation for the treatment of pulmonary fibrosis.

Tissue fibrosis associated depletion of lipid-filled cells

Fibrosis is primarily described as the deposition of excessive extracellular matrix, but in many tissues it also involves a loss of lipid or lipid-filled cells. Lipid-filled cells are critical to tissue function and integrity in many tissues including the skin and lungs. Thus, loss or depletion of lipid-filled cells during fibrogenesis, has implications for tissue function. In some contexts, lipid-filled cells can impact ECM composition and stability, highlighting their importance in fibrotic transformation. Recent papers in fibrosis address this newly recognized fibrotic lipodystrophy phenomenon. Even in disparate tissues, common mechanisms are emerging to explain fibrotic lipodystrophy. These findings have implications for fibrosis in tissues composed of fibroblast and lipid-filled cell populations such as skin, lung, and liver. In this review, we will discuss the roles of lipid-containing cells, their reduction/loss during fibrotic transformation, and the mechanisms of that loss in the skin and lungs.

TGF-β1, pSmad-2/3, Smad-7, and β-Catenin Are Augmented in the Pulmonary Arteries from Patients with Idiopathic Pulmonary Fibrosis (IPF): Role in Driving Endothelial-to-Mesenchymal Transition (EndMT)

Background: We have previously reported that endothelial-to-mesenchymal transition (EndMT) is an active process in patients with idiopathic pulmonary fibrosis (IPF) contributing to arterial remodelling. Here, we aim to quantify drivers of EndMT in IPF patients compared to normal controls (NCs). Methods: Lung resections from thirteen IPF patients and eleven NCs were immunohistochemically stained for EndMT drivers, including TGF-β1, pSmad-2/3, Smad-7, and β-catenin. Intima, media, and adventitia were analysed for expression of each EndMT driver in pulmonary arteries. Computer- and microscope-assisted Image ProPlus7.0 image analysis software was used for quantifications. Results: Significant TGF-β1, pSmad-2/3, Smad-7, and β-catenin expression was apparent across all arterial sizes in IPF (p < 0.05). Intimal TGF-β1, pSmad-2/3, Smad-7, and β-catenin were augmented in the arterial range of 100-1000 μm (p < 0.001) compared to NC. Intimal TGF-β1 and β-catenin percentage expression showed a strong correlation with the percentage expression of intimal vimentin (r' = 0.54, p = 0.05 and r' = 0.61, p = 0.02, respectively) and intimal N-cadherin (r' = 0.62, p = 0.03 and r' = 0.70, p = 0.001, respectively). Intimal TGF-β1 and β-catenin expression were significantly correlated with increased intimal thickness as well (r' = 0.52, p = 0.04; r' = 0.052, p = 0.04, respectively). Moreover, intimal TGF-β1 expression was also significantly associated with increased intimal elastin deposition (r' = 0.79, p = 0.002). Furthermore, total TGF-β1 expression significantly impacted the percentage of DLCO (r' = -0.61, p = 0.03). Conclusions: This is the first study to illustrate the involvement of active TGF-β/Smad-2/3-dependent and β-catenin-dependent Wnt signalling pathways in driving EndMT and resultant pulmonary arterial remodelling in patients with IPF. EndMT is a potential therapeutic target for vascular remodelling and fibrosis in general in patients with IPF.

Targeted alveolar regeneration with Frizzled-specific agonists

Wnt ligands oligomerize Frizzled (Fzd) and Lrp5/6 receptors to control the specification and activity of stem cells in many species. How Wnt signaling is selectively activated in different stem cell populations, often within the same organ, is not understood. In lung alveoli, we show that distinct Wnt receptors are expressed by epithelial (Fzd5/6), endothelial (Fzd4), and stromal (Fzd1) cells. Fzd5 is uniquely required for alveolar epithelial stem cell activity, whereas fibroblasts utilize distinct Fzd receptors. Using an expanded repertoire of Fzd-Lrp agonists, we could activate canonical Wnt signaling in alveolar epithelial stem cells via either Fzd5 or, unexpectedly, non-canonical Fzd6. A Fzd5 agonist (Fzd5ag) or Fzd6ag stimulated alveolar epithelial stem cell activity and promoted survival in mice after lung injury, but only Fzd6ag promoted an alveolar fate in airway-derived progenitors. Therefore, we identify a potential strategy for promoting regeneration without exacerbating fibrosis during lung injury.

Basal Cell-derived WNT7A Promotes Fibrogenesis at the Fibrotic Niche in Idiopathic Pulmonary Fibrosis

Loss of epithelial integrity, bronchiolarization, and fibroblast activation are key characteristics of idiopathic pulmonary fibrosis (IPF). Prolonged accumulation of basal-like cells in IPF may impact the fibrotic niche to promote fibrogenesis. To investigate their role in IPF, basal cells were isolated from IPF explant and healthy donor lung tissues. Single-cell RNA sequencing was used to assess differentially expressed genes in basal cells. Basal cell and niche interaction was demonstrated with the sLP-mCherry niche labeling system. Luminex assays were used to assess cytokines secreted by basal cells. The role of basal cells in fibroblast activation was studied. Three-dimensional organoid culture assays were used to interrogate basal cell effects on AEC2 (type 2 alveolar epithelial cell) renewal capacity. Perturbation was used to investigate WNT7A function in vitro and in a repetitive bleomycin model in vivo. We found that WNT7A is highly and specifically expressed in basal-like cells. Proteins secreted by basal cells can be captured by neighboring fibroblasts and AEC2s. Basal cells or basal cell-conditioned media activate fibroblasts through WNT7A. Basal cell-derived WNT7A inhibits AEC2 progenitor cell renewal in three-dimensional organoid cultures. Neutralizing antibodies against WNT7A or a small molecule inhibitor of Frizzled signaling abolished basal cell-induced fibroblast activation and attenuated lung fibrosis in mice. In summary, basal cells and basal cell-derived WNT7A are key components of the fibrotic niche, providing a unique non-stem cell function of basal cells in IPF progression and a novel targeting strategy for IPF.

Plasticity towards Rigidity: A Macrophage Conundrum in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, and ultimately fatal diffuse parenchymal lung disease. The molecular mechanisms of fibrosis in IPF patients are not fully understood and there is a lack of effective treatments. For decades, different types of drugs such as immunosuppressants and antioxidants have been tested, usually with unsuccessful results. Although two antifibrotic drugs (Nintedanib and Pirfenidone) are approved and used for the treatment of IPF, side effects are common, and they only slow down disease progression without improving patients' survival. Macrophages are central to lung homeostasis, wound healing, and injury. Depending on the stimulus in the microenvironment, macrophages may contribute to fibrosis, but also, they may play a role in the amelioration of fibrosis. In this review, we explore the role of macrophages in IPF in relation to the fibrotic processes, epithelial-mesenchymal transition (EMT), and their crosstalk with resident and recruited cells and we emphasized the importance of macrophages in finding new treatments.

The Role of PTEN in Epithelial–Mesenchymal Transition

Simple Summary

The PTEN phosphatase is a ubiquitously expressed tumor suppressor, which inhibits the PI3K/AKT pathway in the cell. The PI3K/AKT pathway is considered to be one of the main signaling pathways that drives the proliferation of cancer cells. Furthermore, the same pathway controls the epithelial–mesenchymal transition (EMT). EMT is an evolutionarily conserved developmental program, which, upon aberrant reactivation, is also involved in the formation of cancer metastases. Importantly, metastasis is the leading cause of cancer-associated deaths. In this review, we discuss the literature data that highlight the role of PTEN in EMT. Based on this knowledge, we speculate about new possible strategies for cancer treatment.

Abstract

Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN) is one of the critical tumor suppressor genes and the main negative regulator of the PI3K pathway. PTEN is frequently found to be inactivated, either partially or fully, in various malignancies. The PI3K/AKT pathway is considered to be one of the main signaling cues that drives the proliferation of cells. Perhaps it is not surprising, then, that this pathway is hyperactivated in highly proliferative tumors. Importantly, the PI3K/AKT pathway also coordinates the epithelial–mesenchymal transition (EMT), which is pivotal for the initiation of metastases and hence is regarded as an attractive target for the treatment of metastatic cancer. It was shown that PTEN suppresses EMT, although the exact mechanism of this effect is still not fully understood. This review is an attempt to systematize the published information on the role of PTEN in the development of malignant tumors, with a main focus on the regulation of the PI3K/AKT pathway in EMT.

Research Progress in the Molecular Mechanisms, Therapeutic Targets, and Drug Development of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease. Recent studies have identified the key role of crosstalk between dysregulated epithelial cells, mesenchymal, immune, and endothelial cells in IPF. In addition, genetic mutations and environmental factors (e.g., smoking) have also been associated with the development of IPF. With the recent development of sequencing technology, epigenetics, as an intermediate link between gene expression and environmental impacts, has also been reported to be implicated in pulmonary fibrosis. Although the etiology of IPF is unknown, many novel therapeutic targets and agents have emerged from clinical trials for IPF treatment in the past years, and the successful launch of pirfenidone and nintedanib has demonstrated the promising future of anti-IPF therapy. Therefore, we aimed to gain an in-depth understanding of the underlying molecular mechanisms and pathogenic factors of IPF, which would be helpful for the diagnosis of IPF, the development of anti-fibrotic drugs, and improving the prognosis of patients with IPF. In this study, we summarized the pathogenic mechanism, therapeutic targets and clinical trials from the perspective of multiple cell types, gene mutations, epigenetic and environmental factors.

Matrix Metalloproteinases and Their Inhibitors in Pulmonary Fibrosis: EMMPRIN/CD147 Comes into Play

Pulmonary fibrosis (PF) is characterized by aberrant extracellular matrix (ECM) deposition, activation of fibroblasts to myofibroblasts and parenchymal disorganization, which have an impact on the biomechanical traits of the lung. In this context, the balance between matrix metalloproteinases (MMPs) and their tissue inhibitors of metalloproteinases (TIMPs) is lost. Interestingly, several MMPs are overexpressed during PF and exhibit a clear profibrotic role (MMP-2, -3, -8, -11, -12 and -28), but a few are antifibrotic (MMP-19), have both profibrotic and antifibrotic capacity (MMP7), or execute an unclear (MMP-1, -9, -10, -13, -14) or unknown function. TIMPs are also overexpressed in PF; hence, the modulation and function of MMPs and TIMP are more complex than expected. EMMPRIN/CD147 (also known as basigin) is a transmembrane glycoprotein from the immunoglobulin superfamily (IgSF) that was first described to induce MMP activity in fibroblasts. It also interacts with other molecules to execute non-related MMP aactions well-described in cancer progression, migration, and invasion. Emerging evidence strongly suggests that CD147 plays a key role in PF not only by MMP induction but also by stimulating fibroblast myofibroblast transition. In this review, we study the structure and function of MMPs, TIMPs and CD147 in PF and their complex crosstalk between them.

Dynamic Involvement of Telocytes in Modulating Multiple Signaling Pathways in Cardiac Cytoarchitecture

Cardiac interstitium is a complex and dynamic environment, vital for normal cardiac structure and function. Telocytes are active cellular players in regulating main events that feature myocardial homeostasis and orchestrating its involvement in heart pathology. Despite the great amount of data suggesting (microscopically, proteomically, genetically, etc.) the implications of telocytes in the different physiological and reparatory/regenerative processes of the heart, understanding their involvement in realizing the heart's mature cytoarchitecture is still at its dawn. Our scrutiny of the recent literature gave clearer insights into the implications of telocytes in the WNT signaling pathway, but also TGFB and PI3K/AKT pathways that, inter alia, conduct cardiomyocytes differentiation, maturation and final integration into heart adult architecture. These data also strengthen evidence for telocytes as promising candidates for cellular therapies in various heart pathologies.

Tangshen Formula Improves Diabetes-Associated Myocardial Fibrosis by Inhibiting TGF-β/Smads and Wnt/β-Catenin Pathways

Cardiovascular disease has become the main cause of death among complications of diabetes. Myocardial fibrosis is a crucial pathological change of cardiovascular disease. Tangshen Formula (TSF) shows a good clinical effect in the treatment of diabetic kidney disease (DKD). However, whether TSF alleviates diabetes-associated myocardial fibrosis is still unknown. In the present research, we studied the effect and mechanism of TSF in the treatment of myocardial fibrosis in vivo and in vitro. We found that TSF treatment significantly downregulates myocardial fibrosis-related markers, including collagens I and III, and α-SMA. TSF also protects primary mouse cardiac fibroblast (CF) from transforming growth factor-β1- (TGF-β1-) induced damage. Moreover, TSF decreased the expression levels of TGF-β/Smad-related genes (α-SMA, collagens I and III, TGF-β1, and pSmad2/3), and increased Smad7 gene expression. Finally, TSF decreased the expressions of wnt1, active-β-catenin, FN, and MMP7 to regulate the Wnt/β-catenin pathway. Taken together, TSF seems to attenuate myocardial fibrosis in KKAy mice by inhibiting TGF-β/Smad2/3 and Wnt/β-catenin signaling pathways.

Noncanonical Wnt Signaling Promotes Myofibroblast Differentiation in Pulmonary Fibrosis

The Wnt/β-catenin pathway initiates a signaling cascade that is critical in cell differentiation and the normal development of multiple organ systems. The reactivation of this pathway has been documented in experimental and human idiopathic pulmonary fibrosis, wherein Wnt/β-catenin activation has been implicated in epithelial-cell repair. Furthermore, the canonical ligand Wnt3a is known to induce myofibroblast differentiation; however, the role of noncanonical Wnt ligands remains unclear. This study showed significantly higher levels of Wnt11 expression in cells from both patients with idiopathic pulmonary fibrosis and bleomycin-treated mice, as well as in TGFβ-treated mouse lung fibroblasts. Moreover, Wnt11 induced myofibroblast differentiation as manifested by increased α-SMA (ACTA2) expression, which was similar to that induced by canonical Wnt3a/β-catenin signaling. Further investigation revealed that Wnt11 induction of α-SMA was associated with the activation of JNK (c-Jun N-terminal kinase)/c-Jun signaling and was inhibited by a JNK inhibitor. The potential importance of this signaling pathway was supported by in vivo evidence showing significantly increased levels of Wnt11 and activated JNK in the lungs of mice with bleomycin-induced pulmonary fibrosis. Interestingly, fibroblasts did not express canonical Wnt3a, but treatment of these cells with exogenous Wnt3a induced endogenous Wnt11 and Wnt5a, resulting in repression of the Wnt3a/β-catenin target gene Axin2. These findings suggested that the noncanonical Wnt induction of myofibroblast differentiation mediated by the JNK/c-Jun pathway might play a significant role in pulmonary fibrosis, in addition to or in synergy with canonical Wnt3a/β-catenin signaling. Moreover, Wnt3a activation of noncanonical Wnt signaling might trigger a switch from canonical to noncanonical Wnt signaling to induce myofibroblast differentiation.

Matrix metalloproteinases inhibitors in idiopathic pulmonary fibrosis: Medicinal chemistry perspectives

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with limited therapeutic options and a particularly poor prognosis. Matrix metalloproteinases (MMPs), promising targets for the treatment of IPF, have been identified as playing a pivotal role in IPF. Although the pathological processes of MMPs and IPF have been verified, there are no MMP inhibitors for the treatment of IPF in the clinic. In this review, we will present the latest developments in MMP inhibitors, including pharmacophores, binding modes, selectivity and optimization strategies. In addition, we will also discuss the future development direction of MMP inhibitors based on emerging tools and techniques.

DNA Methylation Profiling for the Diagnosis and Prognosis of Patients with Nontuberculous Mycobacterium Lung Disease

The incidence of nontuberculous Mycobacterium (NTM) lung disease is rapidly increasing; however, its diagnosis and prognosis remain unclear while selecting patients who will respond to appropriate treatment. Differences in DNA methylation patterns between NTM patients with good or poor prognosis could provide important therapeutic targets. We used the Illumina MethylationEPIC (850k) DNA methylation microarray to determine the pattern between differentially methylated regions (DMRs) in NTM patients with good or poor prognosis (n = 4/group). Moreover, we merged and compared 20 healthy controls from previous Illumina Methylation450k DNA methylation microarray data. We selected and visualized the DMRs in the form of heatmaps, and enriched terms associated with these DMRs were identified by functional annotation with the “pathfinder” package. In total, 461 and 293 DMRs (|Log2 fold change| > 0.1 and P < 0.03) were more methylated in patients with four poor and four good prognoses, respectively. Furthermore, 337 and 771 DMRs (|Log2 fold change| > 0.08 and P < 0.001) were more methylated in eight NTM patients and 20 healthy controls, respectively. TGFBr1 was significantly less methylated, whereas HLA-DR1 and HLA-DR5 were more methylated in patients with poor prognosis (compared to those with good prognosis). LRP5, E2F1, and ADCY3 were the top three less-methylated genes in NTM patients (compared with the controls). The mTOR and Wnt signaling pathway-related genes were less methylated in patients with NTM. Collectively, genes related to Th1- cell differentiation, such as TGFBr1 and HLA-DR, may be used as biomarkers for predicting the treatment response in patients with NTM lung disease.

Wnt signaling in lung development, regeneration, and disease progression

The respiratory tract is a vital, intricate system for several important biological processes including mucociliary clearance, airway conductance, and gas exchange. The Wnt signaling pathway plays several crucial and indispensable roles across lung biology in multiple contexts. This review highlights the progress made in characterizing the role of Wnt signaling across several disciplines in lung biology, including development, homeostasis, regeneration following injury, in vitro directed differentiation efforts, and disease progression. We further note uncharted directions in the field that may illuminate important biology. The discoveries made collectively advance our understanding of Wnt signaling in lung biology and have the potential to inform therapeutic advancements for lung diseases.

Cody Aros, Carla Pantoja, and Brigitte Gomperts review the key role of Wnt signaling in all aspects of lung development, repair, and disease progression. They provide an overview of recent research findings and highlight where research is needed to further elucidate mechanisms of action, with the aim of improving disease treatments.

Endothelial-to-mesenchymal transition in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by significant vascular alterations and multi-organ fibrosis. Microvascular alterations are the first event of SSc and injured endothelial cells (ECs) may transdifferentiate towards myofibroblasts, the cells responsible for fibrosis and collagen deposition. This process is identified as endothelial-to-mesenchymal transition (EndMT), and understanding of its development is pivotal to identify early pathogenetic events and new therapeutic targets for SSc. In this review, we have highlighted the molecular mechanisms of EndMT and summarize the evidence of the role played by EndMT during the development of progressive fibrosis in SSc, also exploring the possible therapeutic role of its inhibition.

Macrophages in Lung Injury, Repair, and Fibrosis

Fibrosis progression in the lung commonly results in impaired functional gas exchange, respiratory failure, or even death. In addition to the aberrant activation and differentiation of lung fibroblasts, persistent alveolar injury and incomplete repair are the driving factors of lung fibrotic response. Macrophages are activated and polarized in response to lipopolysaccharide- or bleomycin-induced lung injury. The classically activated macrophage (M1) and alternatively activated macrophage (M2) have been extensively investigated in lung injury, repair, and fibrosis. In the present review, we summarized the current data on monocyte-derived macrophages that are recruited to the lung, as well as alveolar resident macrophages and their polarization, pyroptosis, and phagocytosis in acute lung injury (ALI). Additionally, we described how macrophages interact with lung epithelial cells during lung repair. Finally, we emphasized the role of macrophage polarization in the pulmonary fibrotic response, and elucidated the potential benefits of targeting macrophage in alleviating pulmonary fibrosis.

Fighting the storm: could novel anti-TNFα and anti-IL-6 C. sativa cultivars tame cytokine storm in COVID-19?

The main aspects of severe COVID-19 disease pathogenesis include hyper-induction of proinflammatory cytokines, also known as 'cytokine storm', that precedes acute respiratory distress syndrome (ARDS) and often leads to death. COVID-19 patients often suffer from lung fibrosis, a serious and untreatable condition. There remains no effective treatment for these complications. Out of all cytokines, TNFα and IL-6 play crucial roles in cytokine storm pathogenesis and are likely responsible for the escalation in disease severity. These cytokines also partake in the molecular pathogenesis of fibrosis. Therefore, new approaches are urgently needed, that can efficiently and swiftly downregulate TNFα, IL-6, and the inflammatory cytokine cascade, in order to curb inflammation and prevent fibrosis, and lead to disease remission. Cannabis sativa has been proposed to modulate gene expression and inflammation and is under investigation for several potential therapeutic applications against autoinflammatory diseases and cancer. Here, we hypothesized that the extracts of novel C. sativa cultivars may be used to downregulate the expression of pro-inflammatory cytokines and pathways involved in inflammation and fibrosis. Initially, to analyze the anti-inflammatory effects of novel C. sativa cultivars, we used a well-established full thickness human 3D skin artificial EpiDermFTTM tissue model, whereby tissues were exposed to UV to induce inflammation and then treated with extracts of seven new cannabis cultivars. We noted that out of seven studied extracts of novel C. sativa cultivars, three (#4, #8 and #14) were the most effective, causing profound and concerted down-regulation of COX2, TNFα, IL-6, CCL2, and other cytokines and pathways related to inflammation and fibrosis. These data were further confirmed in the WI-38 lung fibroblast cell line model. Most importantly, one of the tested extracts had no effect at all, and one exerted effect that may be deleterious, signifying that careful cannabis cultivar selection must be based on thorough pre-clinical studies. The observed pronounced inhibition of TNFα and IL-6 is the most important finding, because these molecules are currently considered to be the main targets in COVID-19 cytokine storm and ARDS pathogenesis. Novel anti-TNFα and anti-IL-6 cannabis extracts can be useful additions to the current anti-inflammatory regimens to treat COVID-19, as well as various rheumatological diseases and conditions, and 'inflammaging' - the inflammatory underpinning of aging and frailty.

WNT Signalling in Lung Physiology and Pathology

The main physiological function of the lung is gas exchange, mediated at the interface between the alveoli and the pulmonary microcapillary network and facilitated by conducting airway structures that regulate the transport of these gases from and to the alveoli. Exposure to microbial and environmental factors such as allergens, viruses, air pollution, and smoke contributes to the development of chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and lung cancer. Respiratory diseases as a cluster are the commonest cause of chronic disease and of hospitalization in children and are among the three most common causes of morbidity and mortality in the adult population worldwide. Many of these chronic respiratory diseases are associated with inflammation and structural remodelling of the airways and/or alveolar tissues. They can often only be treated symptomatically with no disease-modifying therapies that normalize the pathological tissue destruction driven by inflammation and remodelling. In search for novel therapeutic strategies for these diseases, several lines of evidence revealed the WNT pathway as an emerging target for regenerative strategies in the lung. WNT proteins, their receptors, and signalling effectors have central regulatory roles under (patho)physiological conditions underpinning lung function and (chronic) lung diseases and we summarize these roles and discuss how pharmacological targeting of the WNT pathway may be utilized for the treatment of chronic lung diseases.

The self-fulfilling prophecy of pulmonary fibrosis: a selective inspection of pathological signalling loops

Pulmonary fibrosis is a devastating, progressive disease and carries a prognosis worse than most cancers. Despite ongoing research, the mechanisms that underlie disease pathogenesis remain only partially understood. However, the self-perpetuating nature of pulmonary fibrosis has led several researchers to propose the existence of pathological signalling loops. According to this hypothesis, the normal wound-healing process becomes corrupted and results in the progressive accumulation of scar tissue in the lung. In addition, several negative regulators of pulmonary fibrosis are downregulated and, therefore, are no longer capable of inhibiting these feed-forward loops. The combination of pathological signalling loops and loss of a checks and balances system ultimately culminates in a process of unregulated scar formation. This review details specific signalling pathways demonstrated to play a role in the pathogenesis of pulmonary fibrosis. The evidence of detrimental signalling loops is elucidated with regard to epithelial cell injury, cellular senescence and the activation of developmental and ageing pathways. We demonstrate where these loops intersect each other, as well as common mediators that may drive these responses and how the loss of pro-resolving mediators may contribute to the propagation of disease. By focusing on the overlapping signalling mediators among the many pro-fibrotic pathways, it is our hope that the pulmonary fibrosis community will be better equipped to design future trials that incorporate the redundant nature of these pathways as we move towards finding a cure for this unrelenting disease.

Icaritin Inhibits Skin Fibrosis through Regulating AMPK and Wnt/β-catenin Signaling

Skin fibrosis is one of the major features of scleroderma. WNT/β-catenin signaling is associated with the progression of skin fibrosis. In this study, we aimed to determine the effect of icaritin (IT), a natural compound, on scleroderma-related skin fibrosis and its mechanisms. We found that IT could reduce the expression of COL1A1, COL1A2, COL3A1, CTGF, and α-SMA in human foreskin fibroblasts (HFF-1 cells), scleroderma skin fibroblasts (SSF cells), and TGF-β-induced HFF-1 cells. Wnt/β-catenin signaling was shown to be suppressed by IT. Additionally, IT activated AMPK signaling in HFF-1 cells. In conclusion, IT has an anti-skin fibrotic effect through activation of AMPK signaling and inhibition of WNT/β-catenin signaling. Our findings indicate the potential role of IT in the treatment of scleroderma and provide novel insight for the selection of drug therapy for scleroderma.

Endothelial to mesenchymal transition (EndMT) and vascular remodeling in pulmonary hypertension and idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible fibrotic disease associated with respiratory failure. The disease remains idiopathic, but repeated alveolar epithelium injury, disruption of alveolar-capillary integrity, abnormal vascular repair, and pulmonary vascular remodeling are considered possible pathogenic mechanisms. Also, the development of comorbidities such as pulmonary hypertension (PH) could further impact disease outcome, quality of life and survival rates in IPF.

AREAS COVERED

The current review provides a comprehensive literature survey of the mechanisms involved in the development and manifestations of IPF and their links to PH pathology. This review also provides the current understanding of molecular mechanisms that link the two pathologies and will specifically decipher the role of endothelial to mesenchymal transition (EndMT) along with the possible triggers of EndMT. The possibility of targeting EndMT as a therapeutic option in IPF is discussed.

EXPERT OPINION

With a steady increase in prevalence and mortality, IPF is no longer considered a rare disease. Thus, it is of utmost importance and urgency that the underlying profibrotic pathways and mechanisms are fully understood, to enable the development of novel therapeutic strategies.

The contribution of animal models to understanding the role of the immune system in human idiopathic pulmonary fibrosis

Pulmonary fibrosis occurs in a heterogeneous group of lung disorders and is characterised by an excessive deposition of extracellular matrix proteins within the pulmonary interstitium, leading to impaired gas transfer and a loss of lung function. In the past 10 years, there has been a dramatic increase in our understanding of the immune system and how it contributes to fibrogenic processes within the lung. This review will compare some of the models used to investigate the pathogenesis and treatment of pulmonary fibrosis, in particular those used to study immune cell pathogenicity in idiopathic pulmonary fibrosis, highlighting their advantages and disadvantages in dissecting human disease.

Wnt signaling pathway in aging-related tissue fibrosis and therapies

Fibrosis is the final hallmark of pathological remodeling, which is a major contributor to the pathogenesis of various chronic diseases and aging-related organ failure to fully control chronic wound-healing and restoring tissue function. The process of fibrosis is involved in the pathogenesis of the kidney, lung, liver, heart and other tissue disorders. Wnt is a highly conserved signaling in the aberrant wound repair and fibrogenesis, and sustained Wnt activation is correlated with the pathogenesis of fibrosis. In particular, mounting evidence has revealed that Wnt signaling played important roles in cell fate determination, proliferation and cell polarity establishment. The expression and distribution of Wnt signaling in different tissues vary with age, and these changes have key effects on maintaining tissue homeostasis. In this review, we first describe the major constituents of the Wnt signaling and their regulation functions. Subsequently, we summarize the dysregulation of Wnt signaling in aging-related fibrotic tissues such as kidney, liver, lung and cardiac fibrosis, followed by a detailed discussion of its involvement in organ fibrosis. In addition, the crosstalk between Wnt signaling and other pathways has the potential to profoundly add to the complexity of organ fibrosis. Increasing studies have demonstrated that a number of Wnt inhibitors had the potential role against tissue fibrosis, specifically in kidney fibrosis and the implications of Wnt signaling in aging-related diseases. Therefore, targeting Wnt signaling might be a novel and promising therapeutic strategy against aging-related tissue fibrosis.

TGF-β and WNT signaling pathways in cardiac fibrosis: non-coding RNAs come into focus

Cardiac fibrosis describes the inappropriate proliferation of cardiac fibroblasts (CFs), leading to accumulation of extracellular matrix (ECM) proteins in the cardiac muscle, which is found in many pathophysiological heart conditions. A range of molecular components and cellular pathways, have been implicated in its pathogenesis. In this review, we focus on the TGF-β and WNT signaling pathways, and their mutual interaction, which have emerged as important factors involved in cardiac pathophysiology. The molecular and cellular processes involved in the initiation and progression of cardiac fibrosis are summarized. We focus on TGF-β and WNT signaling in cardiac fibrosis, ECM production, and myofibroblast transformation. Non-coding RNAs (ncRNAs) are one of the main players in the regulation of multiple pathways and cellular processes. MicroRNAs, long non-coding RNAs, and circular long non-coding RNAs can all interact with the TGF-β/WNT signaling axis to affect cardiac fibrosis. A better understanding of these processes may lead to new approaches for diagnosis and treatment of many cardiac conditions. Video Abstract.

Schisandrin B attenuates bleomycin-induced pulmonary fibrosis in mice through the wingless/integrase-1 signaling pathway

Purpose/Aim: Pulmonary fibrosis (PF) is characterized by the progressive and ultimately fatal accumulation of fibroblasts and extracellular matrix in the lung that distorts its architecture and compromises its function.Objective: The present study investigated the potential protective effects of schisandrin B (Sch B) on the Wingless/Integrase-1 (Wnt) signaling pathway in attenuating inflammation and oxidative stress in ICR mice.Methods: Sixty healthy ICR mice were randomly divided into the following groups: control group, bleomycin (BLM) group, Sch B low dose (Sch B-L) group, Sch B medium dose (Sch B-M) group, Sch B high dose (Sch B-H) group, and dexamethasone (DXM) group. The expression of transforming growth factor (TGF)-β1 was examined by ELISA. In addition, the levels of superoxide dismutase (SOD), hydroxyproline (HYP), and the total antioxidant capacity (T-AOC) were determined. The protein and mRNA levels of matrix metalloproteinase 7 (MMP7) and β-catenin in mice were analyzed by western blot and quantitative real -quantitative time PCR (qRT-PCR), respectively.Results: Lung tissues from the BLM group exhibited significantly more inflammatory changes and a significantly greater number of collagen fibers than lung tissues from the control group. In addition, the lung tissues from these BLM-treated mice exhibited slightly increased MMP7 and β-catenin protein expression. Lung tissues from the Sch B-H group exhibited fewer inflammatory changes and fewer collagen fibers than lung tissues from the BLM group. Furthermore, the lung tissues from the Sch B-H mice exhibited decreased HYP and TGF-β1 levels, but increased SOD and T-AOC levels.Conclusions: The present study provided evidence that Sch B may be a potential therapeutic agent for the treatment of PF.

A novel role of LRP5 in tubulointerstitial fibrosis through activating TGF-β/Smad signaling

Previous studies by us and others demonstrated that activation of Wnt/β-catenin signaling plays a pathogenic role in chronic kidney diseases (CKD). Wnt co-receptor LRP5 variants are reported to associate with autosomal dominant polycystic kidney disease; but their exact roles in this disease and renal fibrosis have not been explored. Here, we observed the upregulation of LRP5 in the renal tubules of both type 1 and type 2 diabetic models and of an obstructive nephropathy model. In the obstructed kidneys, Lrp5 knockout significantly ameliorated tubulointerstitial fibrosis and tubular injury without changing Wnt/β-catenin signaling. Instead, decreased levels of TGF-β1 and TGF-β receptors (TβRs) were detected in Lrp5 knockout kidneys, followed by attenuated activation and nuclear translocation of Smad2/3 in the renal tubules, suggesting a regulatory effect of LRP5 on TGF-β/Smad signaling. In consistent with this hypothesis, LRP5 overexpression resulted in enhanced TGF-β/Smad signaling activation in renal tubule epithelial cells. Furthermore, LRP5 was co-immunoprecipitated with TβRI and TβRII, and its extracellular domain was essential for interacting with TβRs and for its pro-fibrotic activity. In addition to stabilizing TβRs, LRP5 increased the basal membrane presentation and TGF-β1-induced internalization of these receptors. Notably, TGF-β1 also induced LRP5 internalization. These findings indicate that LRP5 promotes tubulointerstitial fibrosis, at least partially, via direct modulation of TGF-β/Smad signaling, a novel, Wnt-independent function.

Alveolar Epithelial Type II Cells as Drivers of Lung Fibrosis in Idiopathic Pulmonary Fibrosis

: Alveolar epithelial type II cells (AT2) are a heterogeneous population that have critical secretory and regenerative roles in the alveolus to maintain lung homeostasis. However, impairment to their normal functional capacity and development of a pro-fibrotic phenotype has been demonstrated to contribute to the development of idiopathic pulmonary fibrosis (IPF). A number of factors contribute to AT2 death and dysfunction. As a mucosal surface, AT2 cells are exposed to environmental stresses that can have lasting effects that contribute to fibrogenesis. Genetical risks have also been identified that can cause AT2 impairment and the development of lung fibrosis. Furthermore, aging is a final factor that adds to the pathogenic changes in AT2 cells. Here, we will discuss the homeostatic role of AT2 cells and the studies that have recently defined the heterogeneity of this population of cells. Furthermore, we will review the mechanisms of AT2 death and dysfunction in the context of lung fibrosis.

Chronic WNT/β-catenin signaling induces cellular senescence in lung epithelial cells

The rapid expansion of the elderly population has led to the recent epidemic of age-related diseases, including increased incidence and mortality of chronic lung diseases, such as Idiopathic Pulmonary Fibrosis (IPF). Cellular senescence is a major hallmark of aging and has a higher occurrence in IPF. The lung epithelium represents a major site of tissue injury, cellular senescence and aberrant activity of developmental pathways such as the WNT/β-catenin pathway in IPF. The potential impact of WNT/β-catenin signaling on alveolar epithelial senescence in general as well as in IPF, however, remains elusive. Here, we characterized alveolar epithelial cells of aged mice and assessed the contribution of chronic WNT/β-catenin signaling on alveolar epithelial type (AT) II cell senescence. Whole lungs from old (16-24 months) versus young (3 months) mice had relatively less epithelial (EpCAM⁺) but more inflammatory (CD45⁺) cells, as assessed by flow cytometry. Compared to young ATII cells, old ATII cells showed decreased expression of the ATII cell marker Surfactant Protein C along with increased expression of the ATI cell marker Hopx, accompanied by increased WNT/β-catenin activity. Notably, when placed in an organoid assay, old ATII cells exhibited decreased progenitor cell potential. Chronic canonical WNT/β-catenin activation for up to 7 days in primary ATII cells as well as alveolar epithelial cell lines induced a robust cellular senescence, whereas the non-canonical ligand WNT5A was not able to induce cellular senescence. Moreover, chronic WNT3A treatment of precision-cut lung slices (PCLS) further confirmed ATII cell senescence. Simultaneously, chronic but not acute WNT/β-catenin activation induced a profibrotic state with increased expression of the impaired ATII cell marker Keratin 8. These results suggest that chronic WNT/β-catenin activity in the IPF lung contributes to increased ATII cell senescence and reprogramming. In the fibrotic environment, WNT/β-catenin signaling thus might lead to further progenitor cell dysfunction and impaired lung repair.

Rewiring Host Signaling: Hepatitis C Virus in Liver Pathogenesis

Hepatitis C virus (HCV) is a major cause of liver disease including metabolic disease, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). HCV induces and promotes liver disease progression by perturbing a range of survival, proliferative, and metabolic pathways within the proinflammatory cellular microenvironment. The recent breakthrough in antiviral therapy using direct-acting antivirals (DAAs) can cure >90% of HCV patients. However, viral cure cannot fully eliminate the HCC risk, especially in patients with advanced liver disease or comorbidities. HCV induces an epigenetic viral footprint that promotes a pro-oncogenic hepatic signature, which persists after DAA cure. In this review, we summarize the main signaling pathways deregulated by HCV infection, with potential impact on liver pathogenesis. HCV-induced persistent signaling patterns may serve as biomarkers for the stratification of HCV-cured patients at high risk of developing HCC. Moreover, these signaling pathways are potential targets for novel chemopreventive strategies.

TGF-β in fibrosis by acting as a conductor for contractile properties of myofibroblasts

Myofibroblasts are non-muscle contractile cells that play a key physiologically role in organs such as the stem villi of the human placenta during physiological pregnancy. They are able to contract and relax in response to changes in the volume of the intervillous chamber. Myofibroblasts have also been observed in several diseases and are involved in wound healing and the fibrotic processes affecting several organs, such as the liver, lungs, kidneys and heart. During the fibrotic process, tissue retraction rather than contraction is correlated with collagen synthesis in the extracellular matrix, leading to irreversible fibrosis and, finally, apoptosis of myofibroblasts. The molecular motor of myofibroblasts is the non-muscle type IIA and B myosin (NMMIIA and NMMIIB). Fibroblast differentiation into myofibroblasts is largely governed by the transforming growth factor-β1 (TGF-β1). This system controls the canonical WNT/β-catenin pathway in a positive manner, and PPARγ in a negative manner. The WNT/β-catenin pathway promotes fibrosis, while PPARγ prevents it. This review focuses on the contractile properties of myofibroblasts and the conductor, TGF-β1, which together control the opposing interplay between PPARγ and the canonical WNT/β-catenin pathway.

Glucocorticoids inhibits the repair of airway epithelial cells via the activation of wnt pathway

BACKGROUND

The purpose of this study was to explore the effect of Wnt pathway on the inhibition of airway epithelial cells repair by glucocorticoid.

MATERIALS AND METHODS

The expression of E-cadherin in asthma mice model was detected by immunocytochemistry. XAV939 was used to treat 16HBE, and the expressions of related genes were determined by western blotting and quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, migration and cell cycle were analyzed by methylthiazolyldiphenyl-tetrazolium bromide, wound healing and flow cytometry, respectively.

RESULTS

In asthma mice model, the lung tissue was impaired. After dexamethasone treatment, the airway inflammation was relieved and the expression of E-cadherin was reduced. Dexamethasone increased the expressions of Wnt7b, LRP5, β-catenin and CyclinD1, inhibited cell viability and migration and arrested cell cycle, whereas XAV939 produced the opposite effects. In addition, XAV939 suppressed Wnt pathway that activated by dexamethasone.

CONCLUSION

Glucocorticoid could inhibit cell proliferation and migration via regulating Wnt pathway to affect cell cycle, thus inhibiting the repair of airway epithelial after injury.

The novel inhibitor PRI-724 for Wnt/β-catenin/CBP signaling ameliorates bleomycin-induced pulmonary fibrosis in mice

Purpose/Aim of the Study: Wnt/β-catenin signaling was reported to be activated in pulmonary fibrosis, and was focused on as a target for antifibrotic therapy. However, the mechanism how the inhibition of Wnt/β-catenin signaling ameliorate pulmonary fibrosis has not been fully elucidated. The purpose of this study is to explore the target cells of Wnt/β-catenin inhibition in pulmonary fibrosis and to examine the antifibrotic effect of the novel inhibitor PRI-724 specifically disrupting the interaction of β-catenin and CBP. Materials and Methods: The effect of C-82, an active metabolite of PRI-724, on the expression of TGF-β1 and α-smooth muscle actin (SMA) was examined on fibroblasts and macrophages. We also examined the effects of PRI-724 in mouse model of bleomycin-induced pulmonary fibrosis. Results: The activation and increased accumulation of β-catenin in the canonical pathway were detected in lung fibroblasts as well as macrophages stimulated by Wnt3a using Western blotting. Treatment with C-82 reduced CBP protein and increased p300 protein binding to β-catenin in the nucleus of lung fibroblasts. In addition, C-82 inhibited the expression of SMA in lung fibroblasts treated with TGF-β, indicating the inhibition of myofibroblast differentiation. In the fibrotic lungs induced by bleomycin, β-catenin was stained strongly in macrophages, but the staining of β-catenin in alveolar epithelial cells and fibroblasts was weak. The administration of PRI-724 ameliorated pulmonary fibrosis induced by bleomycin in mice when administered with a late, but not an early, treatment schedule. Analysis of bronchoalveolar fluid (BALF) showed a decreased number of alveolar macrophages. In addition, the level of TGF-β1 in BALF was decreased in mice treated with PRI-724. C-82 also inhibited the production of TGF-β1 by alveolar macrophages. Conclusions: These results suggest that the β-catenin/CBP inhibitor PRI-724 is a potent antifibrotic agent that acts by modulating the activity of macrophages in the lungs.

Single-Cell Transcriptomic Analysis of Human Lung Provides Insights into the Pathobiology of Pulmonary Fibrosis

Rationale: The contributions of diverse cell populations in the human lung to pulmonary fibrosis pathogenesis are poorly understood. Single-cell RNA sequencing can reveal changes within individual cell populations during pulmonary fibrosis that are important for disease pathogenesis. Objectives: To determine whether single-cell RNA sequencing can reveal disease-related heterogeneity within alveolar macrophages, epithelial cells, or other cell types in lung tissue from subjects with pulmonary fibrosis compared with control subjects. Methods: We performed single-cell RNA sequencing on lung tissue obtained from eight transplant donors and eight recipients with pulmonary fibrosis and on one bronchoscopic cryobiospy sample from a patient with idiopathic pulmonary fibrosis. We validated these data using in situ RNA hybridization, immunohistochemistry, and bulk RNA-sequencing on flow-sorted cells from 22 additional subjects. Measurements and Main Results: We identified a distinct, novel population of profibrotic alveolar macrophages exclusively in patients with fibrosis. Within epithelial cells, the expression of genes involved in Wnt secretion and response was restricted to nonoverlapping cells. We identified rare cell populations including airway stem cells and senescent cells emerging during pulmonary fibrosis. We developed a web-based tool to explore these data. Conclusions: We generated a single-cell atlas of pulmonary fibrosis. Using this atlas, we demonstrated heterogeneity within alveolar macrophages and epithelial cells from subjects with pulmonary fibrosis. These results support the feasibility of discovery-based approaches using next-generation sequencing technologies to identify signaling pathways for targeting in the development of personalized therapies for patients with pulmonary fibrosis.

The Primary Cilium: Emerging Role as a Key Player in Fibrosis

PURPOSE OF REVIEW

The myofibroblast is the culprit in the pathogenesis of fibrosis in systemic sclerosis (SSc). Activation of morphogen signaling pathways has been shown to be critically involved in organ fibrosis. Remarkably, the cellular receptors and key molecules from these signaling pathways are localized in the primary cilium. The primary cilium is a unique cellular organelle present in virtually all cells. This article summarizes recent studies evaluating the association between primary cilia and morphogen signaling driving myofibroblast transition and subsequent fibrosis.

RECENT FINDINGS

Emerging observations implicate dysfunctional primary cilia in fibrosis in many different tissues and organs. Primary cilia seem to be necessary for the initiation of the transition and sustained activation of myofibroblasts. We summarize recent progress in this field and propose the primary cilium as a potential mediator of fibrosis pathogenesis in SSc. Understanding the contributions of primary cilia in fibrosis may ultimately inform the development of entirely new approaches for fibrosis prevention and treatment.

LRP5 in age-related changes in vascular and alveolar morphogenesis in the lung

Aging is associated with impaired angiogenesis and lung alveolar regeneration, which contributes to the increased susceptibility to chronic lung diseases (CLD). We have reported that the Wnt ligand co-receptor, low-density lipoprotein receptor-related protein 5 (LRP5), stimulates angiogenesis and lung alveolar regeneration. However, the role of LRP5 in age-related decline in vascular and alveolar morphogenesis remains unclear. In this report, we have demonstrated that vascular and alveolar structures are disrupted in the 24-month (24M) old mouse lungs. The expression of LRP5 and the major angiogenic factors, VEGFR2 and Tie2, is lower in endothelial cells (ECs) isolated from 24M old mouse lungs compared to those from 2M old mouse lungs. Vascular and alveolar formation is attenuated in the hydrogel implanted on the 24M old mouse lungs, while overexpression of LRP5, which restores angiogenic factor expression, reverses vascular and alveolar morphogenesis in the gel. Compensatory lung growth after unilateral pneumonectomy is inhibited in 24M old mice, which is reversed by overexpression of LRP5. These results suggest that LRP5 mediates age-related inhibition of angiogenesis and alveolar morphogenesis. Modulation of LRP5 may be a novel intervention to rejuvenate regenerative ability in aged lung and will lead to the development of efficient strategies for aging-associated CLD.

Ubiquitination in Scleroderma Fibrosis and Its Treatment

Scleroderma (systemic sclerosis, SSc) is a highly heterogeneous rheumatic disease, and uncontrolled fibrosis in visceral organs is the major cause of death in patients. The transforming growth factor-β (TGF-β) and WNT/β-catenin signaling pathways, along with signal transducer and activator of transcription 3 (STAT3), play crucial roles in this fibrotic process. Currently, no therapy is available that effectively arrests or reverses the progression of fibrosis in patients with SSc. Ubiquitination is an important post-translational modification that controls many critical cellular functions. Dysregulated ubiquitination events have been observed in patients with systemic lupus erythematosus, rheumatoid arthritis and fibrotic diseases. Inhibitors targeting the ubiquitination pathway have considerable potential for the treatment of rheumatic diseases. However, very few studies have examined the role and mechanism of ubiquitination in patients with SSc. In this review, we will summarize the molecular mechanisms of ubiquitination in patients with SSc and explore the potential targets for treatment.

Potential regulatory role of circular RNA in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive type of interstitial pneumonia with unknown causes, poor prognosis and no effective therapy available. Circular RNAs (circRNAs), which serve as potential therapeutic targets and diagnostic biomarkers for certain diseases, represent a recent hotspot in the field of RNA research. In the present study, a total of 67 significantly dysregulated circRNAs were identified in the plasma of IPF patients by using a circRNA microarray. Among these circRNAs, 38 were upregulated, whereas 29 were downregulated. Further validation of the results by polymerase chain reaction analysis indicated that Homo sapiens (hsa)_circRNA_100906, hsa_circRNA_102100 and hsa_circRNA_102348 were significantly upregulated, whereas hsa_circRNA_101225, hsa_circRNA_104780 and hsa_circRNA_101242 were downregulated in plasma samples of IPF patients compared with those in samples from healthy controls. The majority of differentially expressed circRNAs were generated from exonic regions. The host genes of the differentially expressed circRNAs were involved in the regulation of the cell cycle, adherens junctions and RNA transport. The competing endogenous RNA (ceRNA) network of the circRNAs/micro(mi)RNAs/mRNAs indicated that circRNA-protected mRNA participated in transforming growth factor-β1, hypoxia-inducible factor-1, Wnt, Janus kinase, Rho-associated protein kinase, vascular endothelial growth factor, mitogen-activated protein kinase, Hedgehog and nuclear factor κB signalling pathways or functioned as biomarkers for pulmonary fibrosis. Furthermore, luciferase reporter assays confirmed that hsa_circRNA_100906 and hsa_circRNA_102348 directly interact with miR-324-5p and miR-630, respectively, which were downregulated in IPF patients. The present study provided a novel avenue for exploring the underlying molecular mechanisms of IPF disease.

Canonical and Non-Canonical Wnt Signaling in Immune Cells

Cell differentiation, proliferation, and death are vital for immune homeostasis. Wnt signaling plays essential roles in processes across species. The roles of Wnt signaling proteins and Wnt ligands have been studied in the past, but the context-dependent mechanisms and functions of these pathways in immune responses remain unclear. Recent findings regarding the role of Wnt ligands and Wnt signaling in immune cells and their immunomodulatory mechanisms suggest that Wnt ligands and signaling are significant in regulating immune responses. We introduce recent key findings and future perspectives on Wnt ligands and their signaling pathways in immune cells as well as the immunological roles and functions of Wnt antagonists.

Developmental pathways in the pathogenesis of lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and terminal lung disease with no known cure. IPF is a disease of aging, with median age of diagnosis over 65 years. Median survival is between 3 and 5 years after diagnosis. IPF is characterized primarily by excessive deposition of extracellular matrix (ECM) proteins by activated lung fibroblasts and myofibroblasts, resulting in reduced gas exchange and impaired pulmonary function. Growing evidence supports the concept of a pro-fibrotic environment orchestrated by underlying factors such as genetic predisposition, chronic injury and aging, oxidative stress, and impaired regenerative responses may account for disease development and persistence. Currently, two FDA approved drugs have limited efficacy in the treatment of IPF. Many of the genes and gene networks associated with lung development are induced or activated in IPF. In this review, we analyze current knowledge in the field, gained from both basic and clinical research, to provide new insights into the disease process, and potential approaches to treatment of pulmonary fibrosis.

Emerging role and therapeutic implication of Wnt signaling pathways in liver fibrosis

Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in liver fibrosis. Therefore, improving our understanding of the molecular pathways that are involved in these processes is essential to generate new therapies for liver fibrosis. Greater knowledge of the role of the Wnt signaling pathway in liver fibrosis could improve understanding of the liver fibrosis pathogenesis. The aim of this review is to describe the present knowledge about the Wnt signaling pathway, which significantly participates in liver fibrosis and HSC activation, and look ahead on new perspectives of Wnt signaling pathway research. Moreover, we will discuss the different interactions with Wnt signaling pathway-regulated liver fibrosis. The Wnt signaling pathway modulates several important aspects of function, including cell proliferation, activation and differentiation. Targeting the Wnt signaling pathway can be a promising direction in liver fibrosis treatment. We discuss new perspectives of Wnt signaling pathway activation in liver fibrosis. For example, antagonist to Wnt and Wnt ligands could inhibit liver fibrosis by regulating Wnt/β-catenin signaling pathway. These findings identify the Wnt signaling pathway as a potentially important for therapeutic targets in liver fibrosis. Future studies are needed in order to find safer and more effective Wnt-based drugs.

Impact of Transcriptomics on Our Understanding of Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal fibrotic lung disease characterized by aberrant remodeling of the lung parenchyma with extensive changes to the phenotypes of all lung resident cells. The introduction of transcriptomics, genome scale profiling of thousands of RNA transcripts, caused a significant inversion in IPF research. Instead of generating hypotheses based on animal models of disease, or biological plausibility, with limited validation in humans, investigators were able to generate hypotheses based on unbiased molecular analysis of human samples and then use animal models of disease to test their hypotheses. In this review, we describe the insights made from transcriptomic analysis of human IPF samples. We describe how transcriptomic studies led to identification of novel genes and pathways involved in the human IPF lung such as: matrix metalloproteinases, WNT pathway, epithelial genes, role of microRNAs among others, as well as conceptual insights such as the involvement of developmental pathways and deep shifts in epithelial and fibroblast phenotypes. The impact of lung and transcriptomic studies on disease classification, endotype discovery, and reproducible biomarkers is also described in detail. Despite these impressive achievements, the impact of transcriptomic studies has been limited because they analyzed bulk tissue and did not address the cellular and spatial heterogeneity of the IPF lung. We discuss new emerging technologies and applications, such as single-cell RNAseq and microenvironment analysis that may address cellular and spatial heterogeneity. We end by making the point that most current tissue collections and resources are not amenable to analysis using the novel technologies. To take advantage of the new opportunities, we need new efforts of sample collections, this time focused on access to all the microenvironments and cells in the IPF lung.