Mechanosignaling through YAP and TAZ drives fibroblast activation and fibrosis

Pulmonary fibrosis: from mechanisms to therapies

Pulmonary fibrosis (PF) is a chronic, progressive interstitial lung disease characterized by excessive deposition of extracellular matrix (ECM) and abnormal fibroblast proliferation, which is mainly caused by air pollution, smoking, aging, occupational exposure, environmental pollutants exposure, and microbial infections. Although antifibrotic agents such as pirfenidone and nintedanib, approved by the United States (US) Food and Drug Administration (FDA), can slow the decline in lung function and disease progression, their side effects and delivery inefficiency limit the overall prognosis of PF. Therefore, there is an urgent need to develop effective therapeutic targets and delivery approaches for PF in clinical settings. This review provides an overview of the pathogenic mechanisms, therapeutic drug targeting signaling pathways, and promising drug delivery strategies for treating PF.

YAP/TAZ activity in PDGFRα-expressing alveolar fibroblasts modulates AT2 proliferation through Wnt4

The Hippo pathway, mediated by its transcriptional effectors Yes-associated protein 1 (YAP) and WW-domain-containing transcription regulator 1 (TAZ), is crucial in maintaining lung homeostasis and facilitating injury repair. While its roles in epithelial cells are well established, its regulatory effects on lung fibroblasts remain less understood. We engineered a mouse model for the inducible knockdown of YAP/TAZ and showed that fibroblast-specific knockdown enhances PDGFRα+ alveolar fibroblasts' support for alveolar-epithelial-stem-cell-derived organoids in vitro. Single-cell profiling revealed changes in fibroblast subpopulations, including the emergence of a Wnt4+ enriched subpopulation. Epigenomic analyses revealed shifts in transcription factor motif enrichment in both fibroblasts and epithelial cells due to fibroblast YAP/TAZ suppression. Further computational and in vivo analyses confirmed increased Wnt signaling and Wnt4 expression in PDGFRα-lineage+ fibroblasts, which enhanced SPC+ alveolar type 2 (AT2) cell proliferation. These findings highlight a mechanistic role of YAP/TAZ in PDGFRα+ alveolar fibroblasts in supporting AT2 cell maintenance and proliferation via Wnt4 secretion.

Integration of mechanics and immunology: Perspective for understanding fibrotic disease mechanisms and innovating therapeutic strategies

The treatment of fibrotic diseases has long posed a medical challenge due to the complex mechanisms underlying their occurrence and progression. Emerging evidence suggests that fibrosis development is influenced not only by biochemical factors but also by the activation of mechanotransduction in response to mechanical stimuli. Mechanoimmunology, an interdisciplinary field that examines how the immune system is influenced by physical forces and mechanical environments, has recently demonstrated significant importance and considerable potential for application in the study of fibrotic diseases. While the mechanisms by which biochemical signals regulate the immune system have been extensively explored, the progression of fibrosis is often impacted by both immune dysregulation and mechanical changes. During fibrosis, immune cells encounter strong mechanical stimuli, such as stiffer substrates and altered viscoelasticity, which activate their own mechanotransduction pathways and subsequently influence fibrosis progression. Targeting the mechanosensation of immune cells to enhance or inhibit their mechanoreception and mechanotransduction, thereby enhancing the anti-fibrotic role they play in the fibrotic process, could help innovate therapeutic strategies for fibrotic diseases. STATEMENT OF SIGNIFICANCE: Fibrotic disease progression is often associated with dysregulation of both tissue mechanical properties and immune responses. The fibrotic microenvironment's altered mechanical properties both result from and drive fibrosis, while immune cells actively sense and respond to these mechanical cues through mechanotransduction pathways. Emerging mechanoimmunology research highlights how mechanical stimuli influence immune cell behavior, yet the precise regulatory mechanisms remain unclear. This review examines mechanical communication in fibrosis, focusing on immune cells' mechanosensing capabilities and their role in disease progression, which helps to enhance our understanding of the pathogenesis of fibrosis and inform innovative strategies to open up mechano-immune pathways targeting fibrosis therapy.

RGD peptide hydrogel downregulates mechanosignal YAP to inhibit postoperative scarring

OBJECTIVE

Glaucoma filtration failure may result from an overabundance of human Tenon's capsule fibroblasts (HTFs) forming a filtration tract scar. Conversely, the Yes-associated protein (YAP), a transcriptional activator of the Hippo signaling pathway, is a crucial matrix stiffness regulator of matrix production and fibroblast activation. With superior biocompatibility and biodegradability, RGD peptide hydrogels imitate the structure of real tissues' extracellular matrix (ECM). The purpose of this research was to determine whether down-regulating YAP expression via RGD peptide hydrogels may prevent HTFs activation and ECM protein secretion. Transforming growth factor-β2 (TGF-β2) was used to induce the activation of HTFs in a cellular model of scarring following glaucoma filtration surgery. Utilizing SD rats, a murine model of subconjunctival injury was established. The shape of collagen fibers was observed through Masson staining, and the expression of YAP and α-smooth muscle actin (α-SMA) was identified through immunohistochemistry. RGD peptide hydrogel was discovered to have anti-scarring properties in a mouse eye injury model, as well as the ability to lessen HTFs activation, YAP expression, cytosolic nucleus accumulation, and the expression of connective tissue growth factor (CTGF) and ECM proteins. The best concentration was found to be 1.0 weight percent among them. This concentration not only makes it easier to inject a drug subconjunctivally in vivo and maintain the filtration vesicle space in the conjunctiva, but it also inhibits the activation of fibroblasts into myofibroblasts and down-regulates the expression of the Hippo-YAP signaling pathway in Tenon's capsule fibroblasts.

STATEMENT OF SIGNIFICANCE

1. The homogenous reticular three-dimensional nanostructure that made up the interior structure of the 1.0 weight percent gel had good drug delivery characteristics for long-lasting controlled drug release. 2. RGD peptide hydrogel had a certain matrix hardness, which could mimic the normal connective tissue hardness under the conjunctiva. 3. RGD peptide hydrogels could prevented the development of rat conjunctival fibrosis. 4. RGD peptide hydrogel could inhibit the expression of YAP and its target gene CTGF, as well as α-SMA, ECM proteins in HTFs. 5. RGD peptide hydrogel has good biocompatibility, biodegradability, and stable mechanical properties, and can also be used as a promising carrier for the controlled release of drugs.

Trpv4-mediated mechanotransduction regulates the differentiation of valvular interstitial cells to myofibroblasts: implications for aortic valve stenosis

As aortic valve stenosis (AVS) progresses, the valve tissue also stiffens. This increase in tissue stiffness causes the valvular interstitial cells (VICs) to transform into myofibroblasts in response. VIC-to-myofibroblast differentiation is critically involved in the development of AVS. Herein, we investigated the role of mechanosensitive Ca2+-permeant transient receptor potential vanilloid 4 (Trpv4) channels in matrix stiffness- and transforming growth factor β1 (TGFβ1)-induced VIC-myofibroblast activation. We confirmed Trpv4 functionality in primary mouse wild-type VICs compared with Trpv4 null VICs using live Ca2+ influx detection during application of its selective agonist and antagonist. Using physiologically relevant hydrogels of varying stiffness that respectively mimic healthy or diseased aortic valve tissue stiffness, we found that genetic ablation of Trpv4 blocked matrix stiffness- and TGFβ1-induced VIC-myofibroblast activation as determined by changes in morphology, alterations of expression of α-smooth muscle actin, and modulations of F-actin generation. Our results showed that N-terminal residues 30-130 in Trpv4 were crucial for cellular force generation and VIC-myofibroblast activation, while deletion of residues 1-30 had no noticeable negative effect on these processes. Collectively, these data suggest a differential regulatory role for Trpv4 in stiffness/TGFβ1-induced VIC-myofibroblast activation. Our data further showed that Trpv4 regulates stiffness/TGFβ1-induced PI3K-AKT activity that is required for VIC-myofibroblast differentiation and cellular force generation, suggesting a mechanism by which Trpv4 activity regulates VIC-myofibroblast activation. Altogether, these data identify a novel role for Trpv4 mechanotransduction in regulating VIC-myofibroblast activation, implicating Trpv4 as a potential therapeutic target to slow and/or reverse AVS development.NEW & NOTEWORTHY Aortic valve stenosis (AVS) progression involves stiffened valve tissue, driving valvular interstitial cells (VICs) to transform into myofibroblasts. This study highlights the role of Trpv4 channels in VIC activation triggered by matrix stiffness and TGFß1. Using hydrogels mimicking healthy and diseased valves, researchers found that Trpv4 regulates cellular force generation and differentiation via PI3K-AKT activity. These findings identify Trpv4 as a potential therapeutic target to slow or reverse AVS progression.

The role of cyclic adenosine monophosphate (cAMP) in pathophysiology of fibrosis

Fibrosis, the excessive production and disorganised deposition of extracellular matrix proteins, can occur in any organ system, disrupting functionality and causing fatality. The number, efficacy and safety of antifibrotic drugs are incredibly limited. Therapeutics which elevate intracellular cyclic adenosine monophosphate (cAMP) offer a potential solution. In this review, we present the signalling mechanisms involved in fibrosis pathophysiology, how cAMP and its effectors might interact with these pathways, and the current preclinical and clinical efforts in this field. cAMP elevating agents have the potential to be future antifibrotic drug candidates, but further studies are required, particularly to develop tissue specific therapeutics.

M-Motif, a potential non-conventional NLS in YAP/TAZ and other cellular and viral proteins that inhibits classic protein import

Multiple mechanisms were proposed to mediate the nuclear import of TAZ/YAP, transcriptional co-activators regulating organ growth and regeneration. Our earlier observations showed that TAZ/YAP harbor a C-terminal, unconventional nuclear localization signal (NLS). Here, we show that this sequence, necessary and sufficient for basal, ATP-independent nuclear import, contains an indispensable central methionine flanked by negatively charged residues. Based on these features, we define the M-motif and propose that it is a new class of NLS, also present and import-competent in other cellular (STAT1 and cyclin B1) and viral (ORF6 of SARS-CoV2, VSV-M) proteins. Accordingly, ORF6 SARS-Cov2 competitively inhibits TAZ/YAP uptake, while TAZ abrogates STAT1 import. Similar to viral M-motif proteins, TAZ binds RAE1 and inhibits classic nuclear protein import, including that of antiviral factors (IRF3 and NF-κB). However, RAE1 is dispensable for TAZ import itself. Thus, the TAZ/YAP NLS has a dual function: it mediates unconventional nuclear import and inhibits classic import, contributing to the suppression of antiviral responses.

Targeted Therapy for Skeletal Muscle Fibrosis: Regulation of Myostatin, TGF-β, MMP, and TIMP to Maintain Extracellular Matrix Homeostasis

Muscle fibrosis, defined by the excessive deposition of extracellular matrix (ECM) components, is a key pathological process that hinders muscle regeneration following injury. Despite muscle's inherent regenerative potential, severe or chronic injuries often result in fibrosis, which compromises muscle function and impedes healing. This review explores a range of therapeutic strategies aimed at modulating the molecular pathways involved in muscle fibrosis, with a focus on the inhibition of myostatin and transforming growth factor-β (TGF-β), as well as the regulation of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Some therapy modalities, including physiotherapy and exercise therapy, which are commonly used, have demonstrated the ability to regulate extracellular matrix (ECM) components and promote muscle repair. In addition, the use of TGF-β inhibitors, herbal plants, and other biochemically relevant compounds, holds promise in controlling fibrosis by targeting key signaling pathways that drive ECM accumulation as well as having anti-fibrotic and anti-inflammatory properties. Regenerative medicine, including therapies using stem cell, secretome, and platelet-rich plasma (PRP), have also been used as single or adjuvant treatment for muscle fibrosis, and represents a novel and minimally invasive approach. Although these therapeutic strategies show considerable promise, translating preclinical findings to clinical practice remains challenging owing to variability in patient responses and the complexity of human muscle injuries. In conclusion, a multifaceted approach targeting ECM regulation, either as single treatment or combined treatment, offers a promising avenue for the treatment of muscle fibrosis.

EDA Fibronectin Microarchitecture and YAP Translocation during Wound Closure

Fibronectin (Fn) is an extracellular matrix glycoprotein with mechanosensitive structure-function. Extra domain A (EDA) Fn, a Fn isoform, is not present in adult tissue but is required for tissue repair. Curiously, EDA Fn is linked to both regenerative and fibrotic tissue repair. Given that Fn mechanoregulates cell behavior, EDA Fn organization during wound closure might play a role in mediating these differing responses. One mechanism by which cells sense and respond to their microenvironment is by activating a transcriptional coactivator, yes-associated protein (YAP). Interestingly, YAP activity is not only required for wound closure but similarly linked to both regenerative and fibrotic repair. Therefore, this study aims to evaluate how, during normal and fibrotic wound closure, EDA Fn organization might modulate YAP translocation by culturing human dermal fibroblasts on polydimethylsiloxane substrates mimicking normal (soft: 18 kPa) and fibrotic (stiff: 146 kPa) wounded skin. On stiffer substrates mimicking fibrotic wounds, fibroblasts assembled an aligned EDA Fn matrix comprising thinner fibers, suggesting increased microenvironmental tension. To evaluate if cell binding to the EDA domain of Fn was essential to overall matrix organization, fibroblasts were treated with Irigenin, which inhibits binding to the EDA domain within Fn. Blocking adhesion to EDA led to randomly organized EDA Fn matrices with thicker fibers, suggesting reduced microenvironmental tension even during fibrotic wound closure. To evaluate whether YAP signaling plays a role in EDA Fn organization, fibroblasts were treated with CA3, which suppresses YAP activity in a dose-dependent manner. Treatment with CA3 also led to randomly organized EDA Fn matrices with thicker fibers, suggesting a potential connected mechanism of reducing tension during fibrotic wound closure. Next, YAP activity was assessed to evaluate the impact of EDA Fn organization. Interestingly, fibroblasts migrating on softer substrates mimicking normal wounds increased YAP activity, but on stiffer substrates, they decreased YAP activity. When fibroblasts on stiffer substrates were treated with Irigenin or CA3, fibroblasts increased YAP activity. These results suggest that there may be disrupted signaling between EDA Fn organization and YAP translocation during fibrotic wound closure that could be restored when reestablishing normal EDA Fn matrix organization to instead drive regenerative wound repair.

Inhibition of Rho GEFs attenuates pulmonary fibrosis through suppressing myofibroblast activation and reprogramming profibrotic macrophages

Idiopathic pulmonary fibrosis has a poor prognosis, with existing medications only partially alleviating symptoms, highlighting the urgent need for new therapeutic approaches. The dysregulations of Rho GTPases/ROCK are related with various diseases, including fibrosis. Nevertheless, the development of drugs for pulmonary fibrosis treatment has predominantly concentrated on ROCK inhibitors. Small GTPases have been historically recognized as "undruggable". Here, we explore a novel Rho GEFs inhibitor GL-V9, and find that GL-V9 alleviates bleomycin-induced pulmonary fibrosis in mice by inhibiting myofibroblast activation and reprogramming profibrotic macrophages. Distinct from the mechanisms of the first-line drug Nintedanib, GL-V9 binds to the DH/PH domain of Rho GEFs and block the activation of Rho GTPase signaling. This action subsequently suppresses myofibroblast activation by interfering with Rho GTPase-dependent cytoskeletal reorganization and the activity of MRTF and YAP, and inhibits M2 macrophage polarization by modulating RhoA/STAT3 activity. The discovery of new regulatory mechanisms of GL-V9 suggests that targeting Rho GEFs represents a potent strategy for pulmonary fibrosis treatment.

Biomaterial scaffold stiffness influences the foreign body reaction, tissue stiffness, angiogenesis and neuroregeneration in spinal cord injury

Biomaterial scaffold engineering presents great potential in promoting axonal regrowth after spinal cord injury (SCI), yet persistent challenges remain, including the surrounding host foreign body reaction and improper host-implant integration. Recent advances in mechanobiology spark interest in optimizing the mechanical properties of biomaterial scaffolds to alleviate the foreign body reaction and facilitate seamless integration. The impact of scaffold stiffness on injured spinal cords has not been thoroughly investigated. Herein, we introduce stiffness-varied alginate anisotropic capillary hydrogel scaffolds implanted into adult rat C5 spinal cords post-lateral hemisection. Four weeks post-implantation, scaffolds with a stiffness approaching that of the spinal cord effectively minimize the host foreign body reaction via yes-associated protein (YAP) nuclear translocation. Concurrently, the softest scaffolds maximize cell infiltration and angiogenesis, fostering significant axonal regrowth but limiting the rostral-caudal linear growth. Furthermore, as measured by atomic force microscopy (AFM), the surrounding spinal cord softens when in contact with the stiffest scaffold while maintaining a physiological level in contact with the softest one. In conclusion, our findings underscore the pivotal role of stiffness in scaffold engineering for SCI in vivo, paving the way for the optimal development of efficacious biomaterial scaffolds for tissue engineering in the central nervous system.

New insights on mesenchymal stem cells therapy from the perspective of the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) manifests as chronic hepatic steatosis, occurring variably across people due to racial and genetic diversity. It represents a stage in the development of chronic liver disease, marked by fat accumulation, inflammatory responses, oxidative stress in the endoplasmic reticulum, and fibrosis as primary concerns. Understanding its underlying mechanisms remains a challenging and pivotal area of study. In the past, acute liver injury-related diseases were commonly treated with methods such as liver transplantation. However, the emergence of artificial liver has shifted focus to stem cell therapies. Unlike conventional drugs, stem cell therapies are continuously evolving. Despite being classified as drugs, stem cells demonstrated significant efficacy after multiple injections. Mesenchymal stem cells, unlike other types of stem cells, do not have the risk of tumor formation and low immunogenicity, reducing the hypersensitivity reactions associated with liver transplantation. Increasingly, studies suggest that mesenchymal stem cells hold promise in the treatment of chronic liver injury diseases. This review focuses on investigating the role of mesenchymal stem cells in chronic metabolic liver diseases, such as non-alcoholic fatty liver disease, and delves into their specific functions.

Cardiac Fibroblasts: Helping or Hurting

Cardiac fibroblasts (CFs) are the essential cell type for heart morphogenesis and homeostasis. In addition to maintaining the structural integrity of the heart tissue, muscle fibroblasts are involved in complex signaling cascades that regulate cardiomyocyte proliferation, migration, and maturation. While CFs serve as the primary source of extracellular matrix proteins (ECM), tissue repair, and paracrine signaling, they are also responsible for adverse pathological changes associated with cardiovascular disease. Following activation, fibroblasts produce excessive ECM components that ultimately lead to fibrosis and cardiac dysfunction. Decades of research have led to a much deeper understanding of the role of CFs in cardiogenesis. Recent studies using the single-cell genomic approach have focused on advancing the role of CFs in cellular interactions, and the mechanistic implications involved during cardiovascular development and disease. Arguably, the unique role of fibroblasts in development, tissue repair, and disease progression categorizes them into the friend or foe category. This brief review summarizes the current understanding of cardiac fibroblast biology and discusses the key findings in the context of development and pathophysiological conditions.

Extracellular Matrix Stiffness: Mechanotransduction and Mechanobiological Response-Driven Strategies for Biomedical Applications Targeting Fibroblast Inflammation

The extracellular matrix (ECM) is a dynamic network providing mechanical and biochemical cues that regulate cellular behavior. ECM stiffness critically influences fibroblasts, the primary ECM producers, particularly in inflammation and fibrosis. This review explores the role of ECM stiffness in fibroblast-driven inflammation and tissue remodeling, focusing on the physicochemical and biological mechanisms involved. Engineered materials, hydrogels, and polydimethylsiloxane (PDMS) are highlighted for replicating tissue-specific stiffness, enabling precise control over cell-matrix interactions. The surface functionalization of substrate materials, including collagen, polydopamine, and fibronectin, enhances bioactivity and fibroblast adhesion. Key mechanotransduction pathways, such as integrin signaling and YAP/TAZ activation, are related to regulating fibroblast behaviors and inflammatory responses. The role of fibroblasts in driving chronic inflammatory diseases emphasizes their therapeutic potentials. Advances in ECM-modifying strategies, including tunable biomaterials and hydrogel-based therapies, are explored for applications in tissue engineering, drug delivery, anti-inflammatory treatments, and diagnostic tools for the accurate diagnosis and prognosis of ECM stiffness-related inflammatory diseases. This review integrates mechanobiology with biomedical innovations, providing a comprehensive prognosis of fibroblast responses to ECM stiffness and outlining future directions for targeted therapies.

Mechanism of Lung Fibrosis Caused by Rare Earth Samarium Oxide Through Hippo Signaling Pathway and the Intervention of GBE

With the ongoing advancement and utilization of rare earth elements, human and environmental exposure to these materials has risen substantially. Samarium oxide (Sm₂O₃), a rare earth element, has been shown to induce pulmonary fibrosis, but the mechanisms are not clear. This study aimed to investigate the primary mechanisms by which rare earth Sm2O3 contributes to pulmonary fibrosis in relation to the Hippo signaling pathway and to assess the interventional effects of Ginkgo biloba extract (GBE). A mouse model of pulmonary fibrosis was established through intratracheal administration of a Sm2O3 suspension, while human embryonic lung fibroblasts were also treated for intervention studies. The results indicated that compared with the control group, the expression of SAV1, LATS1/2, MST1, YAP1, and TEAD1 genes was significantly up-regulated in the Sm2O3 group, while the expression of TAZ gene was down-regulated. Additionally, the levels of p-LATS1, LATS1, YAP, and p-YAP were elevated, suggesting that Sm2O3 promotes pulmonary fibrosis through an imbalance and abnormal regulation of the Hippo signaling pathway. Furthermore, human embryonic lung fibroblasts stained with Sm2O3 were treated with different dose gradients of GBE, and the expression level of p-LATS1, LATS1, YAP, and p-YAP was decreased as the dose of Sm2O3 increased, whereas treatment with GBE increased the expression of these proteins. GBE can mitigate the fibrotic response induced by Sm₂O₃ exposure. These findings demonstrate that Sm₂O₃ induces pulmonary fibrosis, at least in part, by inactivating the Hippo signaling pathway. Further investigation is warranted to fully elucidate the protective mechanisms of GBE and its therapeutic potential in this context.

Selective Degradation of TEADs by a PROTAC Molecule Exhibited Robust Anticancer Efficacy In Vitro and In Vivo

Genetic mutations in components of the Hippo pathway frequently lead to the aberrant activation of TEADs, which is often associated with cancer. Consequently, TEADs have been actively pursued as therapeutic targets for diseases driven by TEAD overactivation. In this study, we report two series of TEAD PROTACs based on CRBN binders and VHL binders. Both series yielded potent TEAD degraders, including 19 and 40 (H122), which induced TEAD1 degradation with DC50 < 10 nM. Mechanistic studies demonstrated that the degradation of TEAD1 induced by 40 relied on CRBN binding, TEAD1 binding, E3 ligase activity, and a functional proteasome. RNA-seq analyses indicated that 40 significantly downregulated the expression of Myc target genes, as highlighted by GSEA analysis. More importantly, 40 exhibited robust antitumor efficacy in the MSTO-211H mouse xenograft model. Collectively, our results suggest that TEAD PROTACs have therapeutic potential for the treatment of cancers associated with TEAD overactivation.

Dysregulated ATX-LPA and YAP/TAZ signaling in dystrophic Sgcd-/- mice with early fibrosis and inflammation

BACKGROUND

Sarcoglycanopathies are muscle dystrophies caused by mutations in the genes encoding sarcoglycans (α, β, γ, and δ) that can destabilize the dystrophin-associated glycoprotein complex at the sarcolemma, leaving muscle fibers vulnerable to damage after contraction, followed by inflammatory and fibrotic responses and resulting in muscle weakness and atrophy. Two signaling pathways have been implicated in fibrosis and inflammation in various tissues: autotaxin/lysophosphatidic acid (ATX-LPA) and yes-associated protein 1/transcriptional co-activator with PDZ-binding motif (YAP/TAZ). LPA, synthesized by ATX, can act as a pleiotropic molecule due to its multiple receptors. Two Hippo pathway effectors, YAP/TAZ, can be dephosphorylated by LPA and translocated to the nucleus. They induce several target genes, such as CCN2/CTGF, involved in fibrosis and inflammation. However, no detailed characterization of these processes or whether these pathways change early in the development of sarcoglycanopathy has been evaluated in skeletal muscle.

METHODS

Using the δ-sarcoglycan knockout mouse model (Sgcd-/-), we investigated components of these pathways, inflammatory and fibrotic markers, and contractile properties of different skeletal muscles (triceps-TR, gastrocnemius-GST, diaphragm-DFG, tibialis anterior-TA, and extensor digitorum longus-EDL) at one and two months of age.

RESULTS

We found that Sgcd-/- mice show early dystrophic features (fiber damage/necrosis, centrally nucleated fibers, inflammatory infiltrate, and regenerated fibers) followed by later fiber size reduction in TR, GST, and DFG. These changes are concomitant with an early inflammatory and fibrotic response in these muscles. Sgcd-/- mice also have early impaired force generation in the TA and EDL, and resistance to mechanical damage in the EDL. In addition, an early dysregulation of the ATX-LPA axis and the YAP/TAZ signaling pathway in the TR, GST, and DFG was observed in these mice.

CONCLUSIONS

The ATX-LPA axis and the YAP/TAZ signaling pathway, which are involved in inflammation and fibrosis, are dysregulated in skeletal muscle from an early age in Sgcd-/- mice. These changes are concomitant with a fibrotic and inflammatory response in these mice. Unraveling the role of the LPA axis and YAP/TAZ in sarcoglycanopathy holds great promise for improving our understanding of disease pathogenesis and identifying novel therapeutic targets for this currently incurable group of muscle disorders.

The Hippo pathway: Organ size control and beyond

The Hippo signaling pathway is a highly conserved signaling network for controlling organ size, tissue homeostasis, and regeneration. It integrates a wide range of intracellular and extracellular signals, such as cellular energy status, cell density, hormonal signals, and mechanical cues, to modulate the activity of YAP/TAZ transcriptional coactivators. A key aspect of Hippo pathway regulation involves its spatial organization at the plasma membrane, where upstream regulators localize to specific membrane subdomains to regulate the assembly and activation of the pathway components. This spatial organization is critical for the precise control of Hippo signaling, as it dictates the dynamic interactions between pathway components and their regulators. Recent studies have also uncovered the role of biomolecular condensation in regulating Hippo signaling, adding complexity to its control mechanisms. Dysregulation of the Hippo pathway is implicated in various pathological conditions, particularly cancer, where alterations in YAP/TAZ activity contribute to tumorigenesis and drug resistance. Therapeutic strategies targeting the Hippo pathway have shown promise in both cancer treatment, by inhibiting YAP/TAZ signaling, and regenerative medicine, by enhancing YAP/TAZ activity to promote tissue repair. The development of small molecule inhibitors targeting the YAP-TEAD interaction and other upstream regulators offers new avenues for therapeutic intervention. SIGNIFICANCE STATEMENT: The Hippo signaling pathway is a key regulator of organ size, tissue homeostasis, and regeneration, with its dysregulation linked to diseases such as cancer. Understanding this pathway opens new possibilities for therapeutic approaches in regenerative medicine and oncology, with the potential to translate basic research into improved clinical outcomes.

Role of TGF-β/SMAD/YAP/TAZ signaling in skeletal muscle fibrosis

Skeletal muscle fibrosis is strongly associated with the differentiation of its resident multipotent fibro/adipogenic progenitors (FAPs) toward the myofibroblast phenotype. Although transforming growth factor type β (TGF-β) signaling is well-known for driving FAPs differentiation and fibrosis, due to its pleiotropic functions its complete inhibition is not suitable for treating fibrotic disorders such as muscular dystrophies. Here, we describe that TGF-β operates through the mechanosensitive transcriptional regulators Yes-associated protein (YAP)/ transcriptional coactivator with PDZ-binding motif (TAZ) to determine the myofibroblast fate of FAPs and skeletal muscle fibrosis. Spatial transcriptomics analyses of dystrophic and acute injured muscles showed that areas with active fibrosis and TGF-β signaling displayed high YAP/TAZ activity. Using a TGF-β-driven fibrotic mouse model, we found that activation of YAP/TAZ in activated FAPs is associated with the fibrotic process. Mechanistically, primary culture of FAPs reveals the remarkable ability of TGF-β1 to activate YAP/TAZ through its canonical SMAD3 pathway. Moreover, inhibition of YAP/TAZ, either by disrupting its activity (with Verteporfin) or cellular mechanotransduction (with the Rho inhibitor C3 or soft matrices), decreased TGF-β1-dependent FAPs differentiation into myofibroblasts. In vivo, administration of Verteporfin in mice limits the deposition of collagen and fibronectin, and the activation of FAPs during the development of fibrosis. Overall, our work provides robust evidence for considering YAP/TAZ as a potential target in muscular fibroproliferative disorders.NEW & NOTEWORTHY The understanding of the nuclear factors governing the differentiation of muscular fibro/adipogenic progenitors (FAPs) into myofibroblasts is in its infancy. Here, we comprehensively elucidate the status, regulation, and role of the mechanotransducers Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) in the muscular fibrotic process. Our findings reveal that inhibiting cellular mechanotransduction limits FAP differentiation and the extent of muscular fibrosis exerted by transforming growth factor type β (TGF-β). This research shed new lights on the molecular mechanisms dictating the cell fate of FAPs and the muscular fibrosis.

Engineered hydrogel biomaterials facilitate lung progenitor cell differentiation from induced pluripotent stem cells

Lung progenitor (LP) cells identified by the expression of transcription factor NK2 homeobox 1 (NKX2.1) are essential for the development of all lung epithelial cell types and hold tremendous potential for pulmonary research and translational regenerative medicine applications. Here, we present engineered hydrogels as a promising alternative to the naturally derived materials that are often used to differentiate human-induced pluripotent stem cells (iPSCs) into LP cells. Poly(ethylene glycol) norbornene (PEGNB) hydrogels with defined composition were used to systematically investigate the role of microenvironmental stiffness, cell origin, and splitting during the differentiation process. Results demonstrated that each factor impacted LP differentiation efficiency and that the soft hydrogels replicating healthy lung stiffness [elastic modulus (E) = 4.00 ± 0.25 kPa] produced the highest proportion of LP cells based on flow cytometric analysis results (54%) relative to the stiff hydrogels (48%) and Matrigel controls (32%) at the end of the nonsplit differentiation protocol. Collectively, these results showed that engineered hydrogels provide a well-defined microenvironment for iPSC-to-LP differentiation and perform as effectively as the current gold standard Matrigel-coated tissue culture plastic. Adopting engineered biomaterials in cell culture protocols may enable greater control over differentiation parameters and has the potential to enhance the clinical translation of iPSC-derived LP cells.NEW & NOTEWORTHY Standard iPSC differentiation protocols rely on Matrigel, a basement membrane extract from mouse sarcoma cells that is poorly defined and exhibits significant batch-to-batch variation. Due to these limitations, Matrigel-derived products have never been approved by the Food and Drug Administration. This study introduces a novel method for differentiating iPSCs into lung progenitor cells using well-defined hydrogel substrates. These biomaterials not only enhance differentiation efficiency but also streamline the regulatory pathway, facilitating their potential therapeutic application.

Interplay between genetics and epigenetics in lung fibrosis

Lung fibrosis, including idiopathic pulmonary fibrosis (IPF), is a complex and devastating disease characterised by the progressive scarring of lung tissue leading to compromised respiratory function. Aberrantly activated fibroblasts deposit extracellular matrix components into the surrounding lung tissue, impairing lung function and capacity for gas exchange. Both genetic and epigenetic factors have been found to play a role in the pathogenesis of lung fibrosis, with emerging evidence highlighting the interplay between these two regulatory mechanisms. This review provides an overview of the current understanding of the interplay between genetics and epigenetics in lung fibrosis. We discuss the genetic variants associated with susceptibility to lung fibrosis and explore how epigenetic modifications such as DNA methylation, histone modifications, and non-coding RNA expression contribute to disease. Insights from genome-wide association studies (GWAS) and epigenome-wide association studies (EWAS) are integrated to explore the molecular mechanisms underlying lung fibrosis pathogenesis. We also discuss the potential clinical implications of genetics and epigenetics in lung fibrosis, including the development of novel therapeutic targets. Overall, this review highlights the importance of considering both genetic and epigenetic factors in the understanding and management of lung fibrosis.

Masticatory Stress Maintains Mucosal Homeostasis via M2 Polarization

In addition to breaking down food, mastication plays regulatory roles in tissue homeostasis. During mastication, the oral mucosa is subjected to masticatory stress, and the maintenance between mucosal damage and repair is a key process. Despite rapid healing in the oral mucosa during chewing, the molecular mechanisms underlying repair remain unclear. In this study, we investigated the impact of masticatory stress on masticatory mucosal wound healing. Our data showed that reduced masticatory stress on the oral mucosa in mice fed a soft food diet resulted in decelerated hard palate mucosal wound healing and decreased numbers of Ki67-positive cells as compared with the hard food diet group. An RNA sequencing analysis revealed lower expression levels of the mechanosensitive gene Piezo1 in the hard palate mucosa, as well as lower levels of transforming growth factor β1 (Tgf-β1) and Tgf-β receptor 2 (Tgf-βr2), in the soft food diet group than the hard food diet group. Immunofluorescence staining, flow cytometry, and polymerase chain reaction analyses demonstrated that masticatory stress induced M2 polarization of macrophages surrounding the wound in the hard food diet group, leading to increased Tgf-β1 secretion. The specific deletion of Piezo1 in macrophages (Piezo1DLysm) attenuated masticatory stress-induced accelerated healing in mice. These findings reveal the crucial role of masticatory stress-induced Piezo1 expression in tissue repair, potentially influencing M2 polarization of mucosal macrophages and Tgf-β1 secretion. These findings underscore the pivotal role of physical stimulation in the immune response and tissue repair and may provide important insights into therapeutic interventions for tissue repair.

The involvement of YAP-TGFβ-SMAD-mediated fibrosis in primary inferior oblique overaction

This study investigates the involvement of fibrosis in primary inferior oblique overaction (PIOOA), a strabismus characterized by excessive upward eye rotation. First, we identified extensive fibrotic changes in inferior oblique (IO) muscles in PIOOA patients compared to normal controls. A strong positive correlation was clinically established between the severity of PIOOA and the expression of collagen type I alpha 1 chain (COL1A1). COL1A1 levels correlate with preoperative and postoperative clinical grading of PIOOA and the degree of fundus deviation, as measured by disk-foveal angle (DFA). Moreover, immunofluorescence in IO muscle sections of PIOOA patients confirmed activation of fibro/adipogenic progenitors (FAPs) and suggested increased activation of YAP. Interestingly, the TGFβ signaling pathway also exhibited activation, with a notable increase observed in the expression of TGFβ2 in the PIOOA group. Subsequently, we first isolated FAPs from human IO muscles and validated these findings. In vitro, YAP overexpression promoted the differentiation of FAPs into myofibroblasts, exacerbating fibrotic changes. However, knockdown of YAP inhibited the activation of FAPs and fibrogenesis induced by TGFβ2. More importantly, we found TGFβ2 treatment promoted the activation of YAP simultaneously, and the overexpression or inhibition of YAP also affected TGFβ2 production and Smad phosphorylation, indicating a close connection between the two. Remarkably, verteporfin was observed to block both pathways effectively. Taken together, these findings suggest that the YAP-TGFβ-SMAD signaling cascade plays a key role in the pathophysiology of PIOOA through FAP-mediated fibrosis. Targeting these pathways may therefore provide a potential therapeutic strategy for managing PIOOA by alleviating muscle fibrosis.

Dopamine receptors and organ fibrosis

Organ fibrosis, considered as a major global health concern, is a pathological condition often occurring after tissue injury in various organs. The pathogenesis of fibrosis involves multiple phases and multiple cell types. Dopamine is involved in various life activities by activating five receptors (D1, D2, D3, D4, D5). Activation or loss of function of dopamine receptors has been reported to be associated with the fibrosis of several organs, such as ocular, lung, liver, heart, and kidney. In this paper, we review dopamine receptors' potential roles in organ fibrosis and mechanisms by which organ fibrosis develops or decreases when dopamine receptors function is activated or perturbed.

Biomaterials for neuroengineering: applications and challenges

Neurological injuries and diseases are a leading cause of disability worldwide, underscoring the urgent need for effective therapies. Neural regaining and enhancement therapies are seen as the most promising strategies for restoring neural function, offering hope for individuals affected by these conditions. Despite their promise, the path from animal research to clinical application is fraught with challenges. Neuroengineering, particularly through the use of biomaterials, has emerged as a key field that is paving the way for innovative solutions to these challenges. It seeks to understand and treat neurological disorders, unravel the nature of consciousness, and explore the mechanisms of memory and the brain's relationship with behavior, offering solutions for neural tissue engineering, neural interfaces and targeted drug delivery systems. These biomaterials, including both natural and synthetic types, are designed to replicate the cellular environment of the brain, thereby facilitating neural repair. This review aims to provide a comprehensive overview for biomaterials in neuroengineering, highlighting their application in neural functional regaining and enhancement across both basic research and clinical practice. It covers recent developments in biomaterial-based products, including 2D to 3D bioprinted scaffolds for cell and organoid culture, brain-on-a-chip systems, biomimetic electrodes and brain-computer interfaces. It also explores artificial synapses and neural networks, discussing their applications in modeling neural microenvironments for repair and regeneration, neural modulation and manipulation and the integration of traditional Chinese medicine. This review serves as a comprehensive guide to the role of biomaterials in advancing neuroengineering solutions, providing insights into the ongoing efforts to bridge the gap between innovation and clinical application.

YAP promotes fibrosis by regulating macrophage to myofibroblast transdifferentiation and M2 polarization in chronic pancreatitis

Chronic pancreatitis (CP) is a clinical entity characterized by progressive inflammation and irreversible fibrosis of the pancreas, which ultimately leads to exocrine and/or endocrine insufficiency as well as an increased risk of pancreatic cancer. Currently, there are no specific or effective approved therapies for CP. Herein, we show that macrophage to myofibroblast transdifferentiation (MMT) and M2 macrophage polarization are associated with both human CP and CP experimental mouse models. In addition, we show YAP is activated in macrophages during CP. Furthermore, we used the YAP agonist XMU-MP-1 (XMU) and the YAP inhibitor Verteporfin (VP) to modulate YAP expression levels. In vitro experiments revealed that XMU upregulated YAP expression, thereby promoting MMT and enhancing M2 macrophage polarization; conversely, VP downregulated YAP expression, inhibiting these effects. In vivo studies indicated that XMU exacerbated acinar cell atrophy and interstitial fibrosis in caerulein-induced mouse models of CP, while VP mitigated these adverse effects associated with CP. These findings provide new insights into the pathogenic mechanisms underlying CP, and offer potential therapeutic targets for CP.

Genome-wide CRISPR/Cas9 screening identifies key profibrotic regulators of TGF-β1-induced epithelial-mesenchymal transformation and pulmonary fibrosis

Background

The idiopathic pulmonary fibrosis (IPF) is a progressive and lethal interstitial lung disease with high morbidity and mortality. IPF is characterized by excessive extracellular matrix accumulation (ECM) and epithelial-mesenchymal transformation (EMT). To date, few anti-fibrotic therapeutics are available to reverse the progression of pulmonary fibrosis, and it is important to explore new profibrotic molecular regulators mediating EMT and pulmonary fibrosis.

Methods

Based on our model of TGF-β1-induced EMT in BEAS-2B cells, we performed the genome-wide CRISPR/Cas9 knockout (GeCKO) screening technique, pathway and functional enrichment analysis, loss-of-function experiment, as well as other experimental techniques to comprehensively investigate profibrotic regulators contributing to EMT and the pathogenesis of pulmonary fibrosis.

Results

Utilizing the GeCKO library screening, we identified 76 top molecular regulators. Ten candidate genes were subsequently confirmed by integrating the high-throughput data with findings from pathway and functional enrichment analysis. Among the candidate genes, knockout of COL20A1 and COL27A1 led to decreased mRNA expression of ECM components (Fibronectin and Collagen-I), as well as an increased rate of cell apoptosis. The mRNA expression of Collagen-I, together with the cell viability and migration, were inhibited when knocking out the WNT11. In addition, a decrease in the protein deposition of ECM components was observed by suppressing the expression of COL20A1, COL27A1, and WNT11.

Conclusion

Our study demonstrates that the COL20A1, COL27A1, and WNT11 serve as key profibrotic regulators of EMT. Gaining understanding and insights into these key profibrotic regulators of EMT paves the way for the discovery of new therapeutic targets against the onset and progression of IPF.

Biomaterial-based 3D human lung models replicate pathological characteristics of early pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and incurable lung disease characterized by tissue scarring that disrupts gas exchange. Epithelial cell dysfunction, fibroblast activation, and excessive extracellular matrix deposition drive this pathology that ultimately leads to respiratory failure. Mechanistic studies have shown that repeated injury to alveolar epithelial cells initiates an aberrant wound-healing response in surrounding fibroblasts through secretion of mediators like transforming growth factor-β, yet the precise biological pathways contributing to disease progression are not fully understood. To better study these interactions there is a critical need for lung models that replicate the cellular heterogeneity, geometry, and biomechanics of the distal lung microenvironment. In this study, induced pluripotent stem cell-derived alveolar epithelial type II (iATII) cells and human pulmonary fibroblasts were arranged to replicate human lung micro-architecture and embedded in soft or stiff poly(ethylene glycol) norbornene (PEG-NB) hydrogels that recapitulated the mechanical properties of healthy and fibrotic lung tissue, respectively. The co-cultured cells were then exposed to pro-fibrotic biochemical cues, including inflammatory cytokines and growth factors. iATIIs and fibroblasts exhibited differentiation pathways and gene expression patterns consistent with trends observed during IPF progression in vivo. A design of experiments statistical analysis identified stiff hydrogels combined with pro-fibrotic biochemical cue exposure as the most effective condition for modeling fibrosis in vitro. Finally, treatment with Nintedanib, one of only two Food and Drug Administration (FDA)-approved drugs for IPF, was assessed. Treatment reduced fibroblast activation, as indicated by downregulation of key activation genes, and upregulated several epithelial genes. These findings demonstrate that human 3D co-culture models hold tremendous potential for advancing our understanding of IPF and identifying novel therapeutic targets.

YAP as a potential therapeutic target for myofibroblast formation in asthma

Myofibroblasts accumulation contributes to airway remodeling, with the mechanisms being poorly understood. It is steroid-insensitive and has not been therapeutically targeted in asthma. In this study, we explored the potential of yes-associated protein (YAP) as a therapeutic target for myofibroblasts formation in asthma, by revealing the novel role and mechanisms by which YAP activation in type II alveolar epithelial (ATII) cells promotes the fibroblast-to-myofibroblast transition in vitro and in vivo. By performing immunofluorescence staining, we showed that myofibroblasts were increased in the bronchial walls and alveolar parenchyma in clinical asthmatic and house dust mite (HDM)-induced mouse lung samples. This was accompanied by YAP overexpression and nuclear translocation in ATII cells, and connective tissue growth factor (CTGF) upregulation. In vitro, HDM or combination of rhIL-1β with rhTNF-α upregulated and activated YAP in human primary ATII cells and A549 cells, but not in the bronchial epithelial cells, BEAS-2B. This effect was mediated by F-actin polymerization and could be suppressed by pretreatment with latrunculin A but not budesonide. Inhibition of YAP/transcriptional coactivator with PDZ-binding motif (TAZ) in A549 cells by pretreatment with YAP/TAZ siRNA or verteporfin, but not budesonide, impaired the fibroblast-to-myofibroblast transition in vitro. In vivo, verteporfin partly or completely prevented HDM-induced bronchial or alveolar myofibroblast accumulation, and significantly suppressed CTGF expression and collagen deposition in mouse lungs, without profoundly affecting airway inflammation. Our results provide novel mechanistic insights into airway remodeling, and holds promise for the development of novel therapeutic strategies.

Mechanosignaling via Integrins: Pivotal Players in Liver Fibrosis Progression and Therapy

Liver fibrosis, a consequence of chronic liver injury, represents a major global health burden and is the leading cause of liver failure, morbidity, and mortality. The pathological hallmark of this condition is excessive extracellular matrix deposition, driven primarily by integrin-mediated mechanotransduction. Integrins, transmembrane heterodimeric proteins that serve as primary ECM receptors, orchestrate complex mechanosignaling networks that regulate the activation, differentiation, and proliferation of hepatic stellate cells and other ECM-secreting myofibroblasts. These mechanical signals create self-reinforcing feedback loops that perpetuate the fibrotic response. Recent advances have provided insight into the roles of specific integrin subtypes in liver fibrosis and revealed their regulation of key downstream effectors-including transforming growth factor beta, focal adhesion kinase, RhoA/Rho-associated, coiled-coil containing protein kinase, and the mechanosensitive Hippo pathway. Understanding these mechanotransduction networks has opened new therapeutic possibilities through pharmacological manipulation of integrin-dependent signaling.

Extracellular Matrix Stiffness Modulates Myopia Scleral Remodeling Through Integrin/F-Actin/YAP Axis

Purpose

Scleral extracellular matrix (ECM) remodeling and weakened scleral stiffness are characteristic of myopia. The purpose of this study was to investigate the precise underlying mechanisms of scleral remodeling regulated by mechanical signals emanating from the ECM.

Methods

The expression and regulation of YES-associated protein (YAP) were confirmed in human samples or guinea pig myopia models by Western blot (WB) or ELISA. To mimic the biomechanical microenvironment associated with myopia, stiff (50 kPa) and soft (8 kPa) substrates were established. The underlying mechanisms were further investigated by quantitative real-time RT-PCR, WB, and fluorescence staining in cells treated with siRNAs, plasmids or inhibitors. In vivo, a YAP activator, inhibitor and F-actin polymerization facilitator were applied to evaluate their therapeutic significance for myopia.

Results

Our findings revealed that YAP expression is decreased in the sclera of guinea pigs and humans with myopia. Under mechanical stimuli, YAP functions as a mediator, transducing mechanical signals and modulating collagen expression. Furthermore, integrin α1β1 acts as a regulator of YAP and operates through modification of the F-actin cytoskeleton. Specifically, in response to mechanical forces, integrin α1β1 modulates F-actin restructuring. This modified actin cytoskeletal architecture subsequently facilitates the nuclear translocation of YAP, ultimately leading to the suppression of COL1A1 expression.

Conclusions

Our results suggest that the integrin α1β1-F-actin-YAP-COL1A1 axis constitutes a vital regulatory mechanism intrinsically associated with the pathogenesis of myopia.

Topical Application of TT-10 Ameliorates Impaired Wound Healing

BACKGROUND

In recent decades, chronic wounds have become an increasingly significant clinical concern because of their increasing morbidity and socioeconomic toll. However, there is currently no product available on the market that specifically targets this intricate process. One clear indicator of delayed wound repair is the inhibition of reepithelialization. Yes-associated protein (YAP), which is a potential focal point for tissue repair and regeneration, has been shown to be prominent in several studies. In this context, the authors have identified the pharmacologic product TT-10, which is a YAP activator, as a potential candidate for the treatment of various forms of chronic wounds.

METHODS

The role of TT-10 in regulating YAP activity and subcellular localization was determined by Western blotting and immunofluorescence staining. The effect of TT-10 on the biological functions of keratinocytes was assessed by proliferation, wound healing, and apoptosis assays. The impairment of YAP activity in chronic wounds was measured in human and mouse tissues. The in vivo efficacy of TT-10 was examined by gross examination; hematoxylin and eosin staining; and measuring wound areas and gaps in normal, diabetic, and ischemic wounds.

RESULTS

The authors' findings suggest that TT-10 facilitates the nuclear transport of YAP, consequently increasing YAP activity, which in turn increases the proliferation and migration of keratinocytes. Moreover, the authors showed that intracutaneous injection of TT-10 along the wound periphery promoted reepithelialization by means of YAP activation in the epidermis, culminating in accelerated wound closure in several chronic wound healing models.

CONCLUSION

The authors' research highlights the potential of TT-10 to treat chronic wounds, which is a persistent challenge in tissue repair.

CLINICAL RELEVANCE STATEMENT

The authors' research identifies TT-10, a small molecule YAP activator, as a novel therapeutic candidate that enhances keratinocyte function and promotes reepithelialization, offering plastic surgeons an innovative approach to addressing chronic wound challenges.

ECM stiffness regulates lung fibroblast survival through RasGRF1-dependent signaling

Extracellular matrix stiffness is one of the multiple mechanical signals that alter cellular behavior. During studies exploring the effect of matrix rigidity on lung fibroblast survival, we discovered that enhanced survival on stiff substrates is dependent on elevated Ras activity, owing to the activation of the guanine nucleotide exchange factor, RasGRF1. Mechanistically, we found that the increased Ras activity lead to the activation of both the AKT and ERK pathways. Pharmacological inhibition of AKT or ERK signaling attenuates the elevated survival observed on stiff substrates. AKT signaling regulates the phosphorylation and inactivation of the transcription factor FOXO3a. RNAi experiments demonstrate that FOXO3a activity is critical for the cell death observed on soft substrates. Additionally, downregulation of FOXO3a activity on stiff substrate leads to the degradation of the proapoptotic protein Bim. Depletion of Bim increased the survival of cells on soft substrates. Together, our data show that enhanced matrix stiffness activates a RasGRF1/Ras signaling cascade that regulates the activity of AKT and ERK-dependent FOXO3a and Bim expression to alter cell survival.

Inhibition of Myocardin-related Transcription Factor A Ameliorates Pathological Remodeling of the Pressure-loaded Right Ventricle

Right ventricular (RV) fibrosis is associated with RV dysfunction in a variety of RV pressure-loading conditions in which RV mechanical stress is increased, but the underlying mechanisms driving RV fibrosis are incompletely understood. In pulmonary and cardiovascular diseases characterized by elevated mechanical stress and transforming growth factor-β1 signaling, myocardin-related transcription factor A (MRTF-A) is a mechanosensitive protein critical to driving myofibroblast transition and fibrosis. In this study, we investigated whether MRTF-A inhibition improves RV profibrotic remodeling and function in response to a pulmonary artery banding (PAB) model of RV pressure loading. Rats were assigned into either sham or PAB groups. MRTF-A inhibitor CCG-1423 was administered daily at 0.75 mg/kg in a subset of PAB animals. Echocardiography and pressure-volume hemodynamics were obtained at a terminal experiment 6 weeks later. RV myocardial samples were analyzed for fibrosis, cardiomyocyte hypertrophy, and profibrotic signaling. MRTF-A inhibition slightly reduced systolic dysfunction in PAB rats reflected by increased lateral tricuspid annulus peak systolic velocity, whereas diastolic function parameters were not significantly improved. RV remodeling was attenuated in PAB rats with MRTF-A inhibition, displaying reduced fibrosis. This was accompanied with a reduction in PAB-induced upregulation of Yes-associated protein (YAP) and its paralog transcriptional coactivator with PDZ-binding motif (TAZ). We also confirmed, using a second-generation MRTF-A inhibitor CCG-203971, that MRTF-A is critical in driving RV fibroblast expression of TAZ and markers of myofibroblast transition in response to transforming growth factor-β1 stress and RhoA activation. These studies identify RhoA, MRTF-A, and YAP/TAZ as interconnected regulators of profibrotic signaling in RV pressure loading and as potential targets to improve RV profibrotic remodeling.

YAP/TAZ-associated cell signaling - at the crossroads of cancer and neurodevelopmental disorders

YAP/TAZ (Yes-associated protein/paralog transcriptional co-activator with PDZ-binding domain) are transcriptional cofactors that are the key and major downstream effectors of the Hippo signaling pathway. Both are known to play a crucial role in defining cellular outcomes, including cell differentiation, cell proliferation, and apoptosis. Aside from the canonical Hippo signaling cascade with the key components MST1/2 (mammalian STE20-like kinase 1/2), SAV1 (Salvador homologue 1), MOB1A/B (Mps one binder kinase activator 1A/B) and LATS1/2 (large tumor suppressor kinase 1/2) upstream of YAP/TAZ, YAP/TAZ activation is also influenced by numerous other signaling pathways. Such non-canonical regulation of YAP/TAZ includes well-known growth factor signaling pathways such as the epidermal growth factor receptor (EGFR)/ErbB family, Notch, and Wnt signaling as well as cell-cell adhesion, cell-matrix interactions and mechanical cues from a cell's microenvironment. This puts YAP/TAZ at the center of a complex signaling network capable of regulating developmental processes and tissue regeneration. On the other hand, dysregulation of YAP/TAZ signaling has been implicated in numerous diseases including various cancers and neurodevelopmental disorders. Indeed, in recent years, parallels between cancer development and neurodevelopmental disorders have become apparent with YAP/TAZ signaling being one of these pathways. This review discusses the role of YAP/TAZ in brain development, cancer and neurodevelopmental disorders with a special focus on the interconnection in the role of YAP/TAZ in these different conditions.

PIEZO1-mediated mechanotransduction regulates collagen synthesis on nanostructured 2D and 3D models of fibrosis

Progressive fibrosis can lead to tissue malfunction and organ failure due to the pathologic accumulation of a collagen-rich extracellular matrix. In vitro models provide useful tools for deconstructing the roles of specific biomechanical or biological mechanisms, such as substrate micro- and nanoscale architecture, in these processes for identifying potential therapeutic targets. Here, we investigated how the mechanosensitive ion channel PIEZO1 influences fibrotic gene and protein expression in adipose-derived stem cells (hASCs). Specifically, we examined the role of PIEZO1 and the mechanosensitive transcription factors YAP/TAZ in sensing aligned or non-aligned substrate architecture to regulate collagen formation. We utilized both 2D microphotopatterned substrates and 3D electrospun polycaprolactone (PCL) substrates to study the role of culture dimensionality. We found that PIEZO1 regulates collagen synthesis in hASCs in a manner that is sensitive to substrate architecture. Activation of PIEZO1 induced significant morphological changes in hASCs, particularly when cultured on aligned substrates, leading to a 30-40 % reduction in cell spreading area and increased cell elongation, in 3D-aligned cultures. Picrosirius Red staining and immunoblotting revealed that PIEZO1 activation reduced collagen accumulation in 3D culture. While YAP translocated to the cytoplasm following PIEZO1 activation, depleting YAP and TAZ did not change collagen expression significantly downstream of PIEZO1 activation, implying that YAP/TAZ translocation from the nucleus and decreased collagen synthesis may be independent consequences of PIEZO1 activation. Our studies demonstrate a role for PIEZO1 in cellular mechanosensing of substrate architecture and provide targetable pathways for treating fibrosis and for enhancing tissue-engineered and regenerative approaches for fibrous tissue repair. STATEMENT OF SIGNIFICANCE: This study examines how cells sense and respond to their physical environment via PIEZO1 mechanotransduction. We discovered that cells use PIEZO1 to detect the alignment of surrounding structures, influencing the production of collagen - a key component in fibrosis. Our study used both 2D and 3D models to mimic different tissue environments, providing new insights into how cellular responses change in more complex settings. Importantly, we found that activating PIEZO1 alters cell shape and collagen production, especially on aligned surfaces. Interestingly, while PIEZO1 activation caused YAP translocation to the cytoplasm, this translocation did not directly affect collagen production. This work advances our understanding of fibrosis development and identifies PIEZO1 as a potential target for new therapies.

Muscle satellite cells and fibro-adipogenic progenitors from muscle contractures of children with cerebral palsy have impaired regenerative capacity

AIM

To evaluate the mechanosensitivity of muscle satellite cells (MuSCs) and fibro-adipogenic progenitors (FAPs) in cerebral palsy (CP) and the efficacy of the drug verteporfin in restoring cells' regenerative capacity.

METHOD

Muscle biopsies were collected from six children with CP and six typically developing children. MuSCs and FAPs were isolated and plated on collagen-coated polyacrylamide gels at stiffnesses of 0.2 kPa, 8 kPa, and 25 kPa. Cells were treated with verteporfin to block mechanosensing or with dimethyl sulfoxide as a negative control. MuSC differentiation and FAP activation into myofibroblasts were measured using immunofluorescence staining.

RESULTS

Surprisingly, MuSC differentiation was not affected by stiffness; however, stiff substrates resulted in large myonuclear clustering. Across all stiffnesses, MuSCs from children with CP had less differentiation than those of their typically developing counterparts. FAP activation into myofibroblasts was significantly higher in children with CP than their typically developing peers, but was not affected by stiffness. Verteporfin did not affect differentiation or activation in either cell population, but slightly decreased myonuclear clustering on stiff substrates.

INTERPRETATION

Cells from children with CP were less regenerative and more fibrotic compared to those of their typically developing counterparts, with MuSCs being sensitive to increases in stiffness. Therefore, the mechanosensitivity of MuSCs and FAPs may represent a new target to improve differentiation and activation in CP muscle.

Leukemia inhibitory factor (LIF) receptor amplifies pathogenic activation of fibroblasts in lung fibrosis

Fibrosis drives end-organ damage in many diseases. However, clinical trials targeting individual upstream activators of fibroblasts, such as TGFβ, have largely failed. Here, we target the leukemia inhibitory factor receptor (LIFR) as an "autocrine master amplifier" of multiple upstream activators of lung fibroblasts. In idiopathic pulmonary fibrosis (IPF), the most common fibrotic lung disease, we found that lung myofibroblasts had high LIF expression, and the fibroblasts in fibroblastic foci coexpressed LIF and LIFR. In IPF, fibroblastic foci are the "leading edge" of fibrosis and a key site of disease pathogenesis. TGFβ1, one of the principal drivers of fibrosis, up-regulated LIF expression in IPF fibroblasts. We found that TGFβ1, IL-4, and IL-13 stimulations of fibroblasts require the LIF-LIFR axis to evoke a strong fibrogenic effector response in fibroblasts. In vitro antibody blockade of LIFR on IPF lung fibroblasts reduced the induction of profibrotic genes after TGFβ1 stimulation. Silencing LIF and LIFR reduced profibrotic fibroblast activation following TGFβ1, IL-4, and IL-13 stimulations. We also demonstrated that LIFR amplified profibrotic stimuli in precision-cut lung slices from IPF patients. These LIFR signals were transduced via JAK2, and STAT1 in IPF lung fibroblasts. Together, we find that LIFR drives an autocrine circuit that amplifies and sustains pathogenic activation of IPF fibroblasts. Targeting a single, downstream master amplifier on fibroblasts, like LIFR, is an alternative therapeutic strategy that simultaneously attenuates the profibrotic effects of multiple upstream stimuli.

The Multifaceted Roles of Hippo-YAP in Cardiovascular Diseases

The Hippo-yes-associated protein (YAP) signaling pathway plays a crucial role in cell proliferation, differentiation, and death. It is known to have impact on the progression and development of cardiovascular diseases (CVDs) as well as in the regeneration of cardiomyocytes (CMs). However, further research is needed to understand the molecular mechanisms by which the Hippo-YAP pathway affects the pathological processes of CVDs in order to evaluate its potential clinical applications. In this review, we have summarized the recent findings on the role of the Hippo-YAP pathway in CVDs such as myocardial infarction, heart failure, and cardiomyopathy, as well as its in CM development. This review calls attention to the potential roles of the Hippo-YAP pathway as a relevant target for the future treatment of CVDs.

Calpain-1 Up-Regulation Promotes Bleomycin-Induced Pulmonary Fibrosis by Activating Ferroptosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal disease. Calpain-1 is an effective therapeutic target for vascular endothelial dysfunction and pulmonary hypertension. However, the role of calpain-1 in bleomycin (BLM)-induced IPF has not been defined. The aim of this study was to assess the targeting of calpain-1 by activating ferroptosis in BLM-treated knockout mice and murine lung epithelial-12 cells. The role of calpain-1 in the regulation of IPF was investigated using a BLM-induced IPF mouse model. The results of this study showed that increased expression of calpain-1 was accompanied by increased fibrosis, lipid peroxidation, iron ion accumulation, and Yes-associated protein (YAP) levels and decreased levels of phosphorylated adenosine 5'-monophosphate-activated protein kinase (p-AMPK) in BLM-induced IPF. MDL-28170 (calpain-1 inhibition) treatment and calpain-1 knockdown alleviated ferroptosis and IPF induced by BLM. Overexpression of calpain-1 in murine lung epithelial-12 cells further exacerbated iron accumulation and IPF. Mechanistically, lentivirus-mediated up-regulation of calpain-1 inhibited AMPK activity and promoted the nuclear translocation of YAP, leading to high levels of acyl-CoA synthetase long-chain family 4 and transferrin receptor protein 1 and triggering a ferroptosis response that ultimately exacerbated BLM-induced lung fibrosis. Calpain-1 inhibition reversed these results and ameliorated BLM-induced IPF. In conclusion, these findings suggest that the calpain-1-acyl-CoA synthetase long-chain family 4-transferrin receptor protein 1-ferroptosis-positive regulatory axis contributes to BLM-induced IPF, which indicates that calpain-1 has potential therapeutic value for the treatment of IPF.

TRPV4-mediated Mechanotransduction Regulates the Differentiation of Valvular Interstitial Cells to Myofibroblasts: Implications for Aortic Stenosis

As aortic valve stenosis (AVS) progresses, the valve tissue also stiffens. This increase in tissue stiffness causes the valvular interstitial cells (VICs) to transform into myofibroblasts in response. VIC-to-myofibroblast differentiation is critically involved in the development of AVS. Herein, we investigated the role of mechanosensitive Ca2+-permeant transient receptor potential vanilloid 4 (Trpv4) channels in matrix stiffness- and transforming growth factor β1 (TGFβ1)-induced VIC-myofibroblast activation. We confirmed Trpv4 functionality in primary mouse wild-type VICs compared to Trpv4 null VICs using live Ca2+ influx detection during application of its selective agonist and antagonist. Using physiologically relevant hydrogels of varying stiffness that respectively mimic healthy or diseased aortic valve tissue stiffness, we found that genetic ablation of Trpv4 blocked matrix stiffness- and TGFβ1-induced VIC-myofibroblast activation as determined by changes in morphology, alterations of expression of α-smooth muscle actin, and modulations of F-actin generation. Our results showed that N-terminal residues 30-130 in Trpv4 were crucial for cellular force generation and VIC-myofibroblast activation, while deletion of residues 1-30 had no noticeable negative effect on these processes. Collectively, these data suggest a differential regulatory role for Trpv4 in stiffness/TGFβ1-induced VIC-myofibroblast activation. Our data further showed that Trpv4 regulates stiffness/TGFβ1-induced PI3K-AKT activity that is required for VIC-myofibroblast differentiation and cellular force generation, suggesting a mechanism by which Trpv4 activity regulates VIC-myofibroblast activation. Altogether, these data identify a novel role for Trpv4 mechanotransduction in regulating VIC-myofibroblast activation, implicating Trpv4 as a potential therapeutic target to slow and/or reverse AVS development.

Fibrosis-related Transcriptome Unveils a Distinctive Remodelling Matrix Pattern in Penetrating Ileal Crohn's Disease

BACKGROUND AND AIMS

Stricturing [B2] and penetrating [B3] ileal Crohn's disease have been reported to present similar levels of histopathological transmural fibrosis. This study aimed to compare the fibrosis-related transcriptomic profiles of penetrating and stricturing ileal Crohn's disease.

METHODS

Using Nanostring technology and comparative bioinformatics, we analysed the expression of 787 fibrosis-related genes in 36 ileal surgical specimens, 12 B2 and 24 B3, the latter including 12 cases with associated stricture[s] [B3s] and 12 without [B3o]. Quality control of extracted RNA was performed according to Nanostring parameters and principal component analysis for the distribution analysis. For the selection of the differentially expressed genes, a p-adjusted <0.05 and fold change ≤-1.5 or ≥1.5 were adopted. Quantitative polymerase chain reaction (qPCR) and immunohistochemistry analyses were used to validate selected differentially expressed genes.

RESULTS

We included 34 patients with B2 and B3 phenotypes, balanced for age at diagnosis, age at surgery, gender, Crohn's disease localisation, perianal disease, and therapy. Inflammation and fibrosis histopathological scoring were similar in all cases. B2 and B3 groups showed a very good clustering regarding 30 significantly differentially expressed genes, all being remarkably upregulated in B3. More than half of these genes were involved in Crohn's disease fibrogenesis, and eight differentially expressed genes were so in other organs. The most significantly active biological processes and pathways in penetrating disease were response to TGFβ and matrix organisation and degradation, as validated by immunohistochemistry.

CONCLUSIONS

Despite the histopathological similarities in fibrosis between stricturing and penetrating ileal Crohn's disease, their fibrosis-related transcriptomic profiles are distinct. Penetrating disease exhibits a distinctive transcriptomic landscape related to enhanced matrix remodelling.

Construction of a Curcumin‐Loaded PLLA/PCL Micro‐Nano Conjugated Fibrous Membrane to Synergistically Prevent Postoperative Adhesion From Multiple Perspectives

Postoperative adhesion (POA) has emerged as a prevalent clinical challenge in soft tissue repair, emphasizing the critical need for preventive measures. However, the complex POA development process makes POA prevention from a single aspect insufficient. Hence, a curcumin‐loaded poly‐L‐lactic acid‐poly (caprolactone) micro‐nano conjugated fibrous membrane (PAPC MCFM (cur)) is engineered to synergistically prevent POA from multiple perspectives, in which poly (caprolactone) (PCL) nanofibers (118 ± 12 nm) with low orientation traverse the oriented poly‐L‐lactic acid (PLLA) microfibers (2.0 ± 0.3 µm). The PAPC MCFM not only significantly improves the mechanical properties of the anisotropic fibrous membrane (AIFM) that the modulus of elasticity and the tensile strength in the direction vertical to microfiber orientation increase by 4.5 and 13.0 times, respectively, but also can further enhance the “contact guidance effect” of AIFM, i.e., hindering fibroblast adhesion, proliferation, and differentiation to myofibroblast through inhibiting integrin β1 activation, vinculin expression and focal adhesion (FA) formation, and the nuclear localization activation of yes‐associated protein (YAP). Except for these effects, PAPC MCFM loading with 2.5 mg mL−1 curcumin can further prevent POA by delivering anti‐inflammatory, antioxidant, and antibacterial properties, and by suppressing fibrosis through decreased transforming growth factor‐β1(TGF‐β1) expression, showing effective POA prevention in rat abdominal cavity and rabbit dura mater models.

YAP Alleviates Pulmonary Fibrosis Through Promoting Alveolar Regeneration via Modulating the Stemness of Alveolar Type 2 Cells

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with no cure except transplantation. Abnormal alveolar epithelial regeneration is a key driver of IPF development. The function of Yes1 Associated Transcriptional Regulator (YAP) in alveolar regeneration and IPF pathogenesis remains elusive. Here, we first revealed the activation of YAP in alveolar epithelium 2 cells (AEC2s) from human IPF lungs and fibrotic mouse lungs. Notably, conditional deletion of YAP in mouse AEC2s exacerbated bleomycin-induced pulmonary fibrosis. Intriguingly, we showed in both conditional knockout mice and alveolar organoids that YAP deficiency impaired AEC2 proliferation and differentiation into alveolar epithelium 1 cells (AEC1s). Mechanistically, YAP regulated expression levels of genes associated with cell cycle progression and AEC1 differentiation. Furthermore, overexpression of YAP in vitro promoted cell proliferation. These results indicate the critical role of YAP in alveolar regeneration and IPF pathogenesis. Our findings provide new insights into the regulation of alveolar regeneration and IPF pathogenesis, paving the road for developing novel treatment strategies.

Adolescent exposure to a mixture of per- and polyfluoroalkyl substances (PFAS) depletes the ovarian reserve, increases ovarian fibrosis, and alters the Hippo pathway in adult female mice

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals known for their environmental persistence and resistance to biodegradation. This study investigated the impact of adolescent exposure to a PFAS mixture on adult ovarian function. Female CD-1 mice were orally exposed to vehicle control or a PFAS mixture (comprised of perfluorooctanoic acid, perfluorooctanesulfonic acid, undecafluoro-2-methyl-3-oxahexanoic acid, and perfluorobutanesulfonic acid) for 15 d. After a 42-d recovery period, reproductive hormones, ovarian fibrosis, and ovarian gene and protein expression were analyzed using ELISA, Picrosirius red staining, qPCR, and immunoblotting, respectively. Results revealed that PFAS exposure did not affect adult body or organ weight, although ovarian weight slightly decreased. PFAS-exposed mice exhibited a disturbed estrous cycle, with less time spent in proestrus than control mice. Follicle counting indicated a reduction in primordial and primary follicles. Serum analysis revealed no changes in steroid hormones, follicle-stimulating hormone, or anti-Müllerian hormone, but a significant increase in luteinizing hormone was observed in PFAS-treated mice. Ovaries collected from PFAS-treated mice had increased mRNA transcripts for steroidogenic enzymes and fatty acid synthesis-related genes. PFAS exposure also increased collagen content in the ovary. Additionally, serum tumor necrosis factor-α levels were higher in PFAS-treated mice. Finally, transcripts and protein abundance for Hippo pathway components were upregulated in the ovaries of the PFAS-treated mice. Overall, these findings suggest that adolescent exposure to PFAS can disrupt ovarian function in adulthood.

Involvement of lysophosphatidic acid-LPA1-YAP signaling in healthy and pathological FAPs migration

Skeletal muscle fibrosis is defined as the excessive accumulation of extracellular matrix (ECM) components and is a hallmark of muscular dystrophies. Fibro-adipogenic progenitors (FAPs) are the main source of ECM, and thus have been strongly implicated in fibrogenesis. In skeletal muscle fibrotic models, including muscular dystrophies, FAPs undergo dysregulations in terms of proliferation, differentiation, and apoptosis, however few studies have explored the impact of FAPs migration. Here, we studied fibroblast and FAPs migration and identified lysophosphatidic acid (LPA), a signaling lipid central to skeletal muscle fibrogenesis, as a significant migration inductor. We identified LPA receptor 1 (LPA1) mediated signaling as crucial for this effect through a mechanism dependent on the Hippo pathway, another pathway implicated in fibrosis across diverse tissues. This cross-talk favors the activation of the Yes-associated protein 1 (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ), leading to increased expression of fibrosis-associated genes. This study reveals the role of YAP in LPA-mediated fibrotic responses as inhibition of YAP transcriptional coactivator activity hinders LPA-induced migration in fibroblasts and FAPs. Moreover, we found that FAPs derived from the mdx4cv mice, a murine model of Duchenne muscular dystrophy, display a heightened migratory phenotype due to enhanced LPA signaling compared to wild-type FAPs. Remarkably, we found that the inhibition of LPA1 or YAP transcriptional coactivator activity in mdx4cv FAPs reverts this phenotype. In summary, the identified LPA-LPA1-YAP pathway emerges as a critical driver of skeletal muscle FAPs migration and provides insights into potential novel targets to mitigate fibrosis in muscular dystrophies.

Emerging role and function of Hippo-YAP/TAZ signaling pathway in musculoskeletal disorders

Hippo pathway is an evolutionarily conservative key pathway that regulates organ size and tissue regeneration by regulating cell proliferation, differentiation and apoptosis. Yes-associated protein 1 (YAP)/ WW domain-containing transcription regulator 1 (TAZ) serves as a pivotal transcription factor within the Hippo signaling pathway, which undergoes negative regulation by the Hippo pathway. The expression of YAP/TAZ affects various biological processes, including differentiation of osteoblasts (OB) and osteoclasts (OC), cartilage homeostasis, skeletal muscle development, regeneration and quality maintenance. At the same time, the dysregulation of the Hippo pathway can concurrently contribute to the development of various musculoskeletal disorders, including bone tumors, osteoporosis (OP), osteoarthritis (OA), intervertebral disc degeneration (IDD), muscular dystrophy, and rhabdomyosarcoma (RMS). Therefore, targeting the Hippo pathway has emerged as a promising therapeutic strategy for the treatment of musculoskeletal disorders. The focus of this review is to elucidate the mechanisms by which the Hippo pathway maintains homeostasis in bone, cartilage, and skeletal muscle, while also providing a comprehensive summary of the pivotal role played by core components of this pathway in musculoskeletal diseases. The efficacy and feasibility of Hippo pathway-related drugs for targeted therapy of musculoskeletal diseases are also discussed in our study. These endeavors offer novel insights into the application of Hippo signaling in musculoskeletal disorders, providing effective therapeutic targets and potential drug candidates for treating such conditions.

Targeting YAP Activity and Glutamine Metabolism Cooperatively Suppresses Tumor Progression by Preventing Extracellular Matrix Accumulation

Cancer cells use multiple mechanisms to evade the effects of glutamine metabolism inhibitors. The pathways that govern responses to alterations in glutamine availability within the tumor may represent therapeutic targets for combinatorial strategies with these inhibitors. Here, we showed that targeting glutamine utilization stimulated Yes-associated protein (YAP) signaling in cancer cells by reducing cyclic adenosine monophosphate/protein kinase A (PKA)-dependent phosphorylation of large tumor suppressor (LATS). Elevated YAP activation induced extracellular matrix (ECM) deposition by increasing the secretion of connective tissue growth factor that promoted the production of fibronectin and collagen by surrounding fibroblasts. Consequently, inhibiting YAP synergized with inhibition of glutamine utilization to effectively suppress tumor growth in vivo, along with a concurrent decrease in ECM deposition. Blocking ECM remodeling also augmented the tumor suppressive effects of the glutamine utilization inhibitor. Collectively, these data reveal mechanisms by which targeting glutamine utilization increases ECM accumulation and identify potential strategies to reduce ECM levels and increase the efficacy of glutamine metabolism inhibitors. Significance: Blocking glutamine utilization activates YAP to promote ECM deposition by fibroblasts, highlighting the potential of YAP inhibitors and antifibrotic strategies as promising approaches for effective combination metabolic therapies in cancer.

Vitamin D receptor attenuates carbon tetrachloride-induced liver fibrosis via downregulation of YAP

Liver fibrosis is characterized by the excessive accumulation of extracellular matrix proteins, which can lead to cirrhosis and liver cancer. Metabolic dysfunction-associated steatosis liver diseases are common causes of liver fibrosis, sharing a similar pathogenesis with carbon tetrachloride (CCl₄) exposure. This process involves the activation of hepatic stellate cells (HSCs) into myofibroblasts. However, the detailed mechanism and effective treatment strategies require further investigation. In this study, we uncovered a negative correlation between VDR expression and YAP within HSCs. Subsequently, we demonstrated that VDR exerted a downregulatory influence on YAP transcriptional activity in HSCs. Intriguingly, activation VDR effectively inhibited the culture induced activation of primary HSCs by suppressing the transcriptional activity of early YAP. Furthermore, in vivo results manifested that hepatic-specific deletion of YAP/TAZ ameliorates CCl4-induced liver fibrosis, and nullified the antifibrotic efficacy of VDR. Importantly, a YAP inhibitor rescued the exacerbation of liver fibrosis induced by hepatic-specific VDR knockout. Moreover, the combined pharmacological of VDR agonist and YAP inhibitor demonstrated a synergistic effect in diminishing CCl4-induced liver fibrosis, primary HSCs activation and hepatic injury in vivo. These effects were underpinned by their collective ability to inhibit HSC activation through AMPK activation, consequently curbing ATP synthesis and HSCs proliferation. In conclusion, our results not only revealed the inhibition of VDR on YAP-activated liver stellate cells but also identified a synergistic effect of VDR agonist and YAP inhibitor in an AMPKα-dependent manner, providing a practical foundation for integration of multi-targeted drugs in the therapy of CCl4-induced hepatic fibrosis.

Mechanical network motifs as targets for mechanomedicine

The identification and analysis of network motifs has been widely used in the functional analysis of signaling components, disease discovery and other fields. The positive feedback loop (PFL) is a simple but important network motif. The formation of a PFL is regulated by mechanical cues such as substrate stiffness, fiber stretching and cell compression in the cell microenvironment. Here, we propose a new term, 'mechanical PFL', and analyze the mechanisms of mechanical PFLs at molecular, subcellular and cellular scales. More and more therapies are being targeted against mechanosignaling pathways at the experimental and preclinical stages, and exploring mechanical PFLs as potential mechanomedicine targets could be a new direction for disease treatment.