Pharmacological YAP activation promotes regenerative repair of cutaneous wounds

Activation of MST1 protects filtration barrier integrity of diabetic kidney disease in mice through restoring the tight junctions of glomerular endothelial cells

As a pathological feature of diabetic kidney disease (DKD), dysregulated glomerular filtration barrier function could lead to the increased levels of proteinuria. The integrity of tight junctions (TJs) of glomerular endothelial cells (GECs) is a guarantee of physiological function of glomerular filtration barrier. Mammalian sterile 20-like kinase (MST1) is a key regulatory protein in the blood-brain barrier (BBB), and it regulates the expression of TJs-related proteins in cerebral vascular endothelial cells. Our previous study showed that MST1 was involved in renal tubulointerstitial fibrosis of DKD. In the present study we investigated the role of MST1 in barrier function of GECs of DKD, and explored its regulatory mechanisms. In kidney tissue section of DKD patients and db/db mice, and high glucose (HG)-cultured mouse glomerular endothelial cells (mGECs), we showed that MST1 was inactivated in the GECs of DKD accompanied by disrupted glomerular endothelial barrier. In db/db mice and HG-cultured mGECs, knockdown of MST1 increased proteinuria levels, and disrupted glomerular endothelial barrier through decreasing TJs-related proteins, whereas MST1 overexpression restored glomerular endothelial barrier through regaining TJs-related proteins. In db/db mice and HG-cultured mGECs, we demonstrated that MST1 inhibition induced TJs's disruption of GECs via activating YAP1/TEAD signaling. Verteporfin (an inhibitor of YAP1-TEAD interaction) and PY-60 (a YAP1 agonist) were used to verify the role of YAP1/TEAD signaling in the regulation effect of MST1 on barrier function of mGECs. In conclusion, MST1 activation recovers glomerular endothelial barrier of DKD by regaining TJs-related proteins via inhibiting YAP1/TEAD signaling. This study highlights the multiple regulation of MST1 activation on kidney injury.

Binding of collagen I to integrins alleviates UVB-caused mitochondrial disorders in human keratinocytes HaCaT through enhancement of F-actin polymerization

Collagen I is one of the major components of the extracellular matrix in human skin, and is frequently used in skin cares and medications. Previously, we revealed that human keratinocytes HaCaT cells grown on collagen I (Col)-coated dishes gain resistance against UVB damages owing to the restored mitophagy. In this study, we further investigate the mechanisms by which collagen I modulates mitophagy. UVB irradiation causes loss of integrin β1 and collapse of F-actin cytoskeleton. Considering the requirement of actin skeleton in various cellular processes, we are curious about the participation of F-actin collapse in UVB damage. Integrin β1, whose activation enhances F-actin assembly, is a potential target for Col in UVB-treated cells. Notably, inhibiting integrin by adding an inhibitor RGDS or siRNA attenuates the effect of Col against UVB damages, confirming the participation of integrin in cell protection. The collapse of F-actin is rescued by Col, accompanying increases in the mRNA of F-actin polymerization-associated proteins and decreases in the mRNA of depolymerization-associated proteins. Inhibiting actin polymerization by using cytochalasin D represses the protective effect of Col, confirming the cytoprotective role of F-actin in UVB-treated cells. Remarkably, mitophagy in UVB-treated cells restored by Col-coating is inhibited by adding cytochalasin D or RGDS, as shown by the decreases of lysosomes, mitochondrial ubiquitin proteins, and co-localization of autophagosomes and mitochondria, resulting in accumulation of damaged mitochondria, which stresses the importance of F-actin and integrin in mitophagy. In summary, integrins and F-actin are required for mitophagy in UVB-irradiated HaCaT cells, and their enhancements by Col-coating facilitate timely elimination of damaged mitochondria caused by UVB, finally contributing to cell survival.

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.

The Recovery of Epidermal Proliferation Pattern in Human Skin Xenograft

Abnormalities in epidermal keratinocyte proliferation are a characteristic feature of a range of dermatological conditions. These include hyperproliferative states in psoriasis and dermatitis as well as hypoproliferative states in chronic wounds. This emphasises the importance of investigating the proliferation kinetics under conditions of healthy skin and identifying the key regulators of epidermal homeostasis, maintenance, and recovery following wound healing. Animal models contribute to our understanding of human epidermal self-renewal. Human skin xenografting overcomes the ethical limitations of studying human skin during regeneration. The application of this approach has allowed for the identification of a single population of stem cells and both slowly and rapidly cycling progenitors within the epidermal basal layer and the mapping of their location in relation to rete ridges and hair follicles. Furthermore, we have traced the dynamics of the proliferation pattern reorganization that occurs during epidermal regeneration, underlining the role of YAP activity in epidermal relief formation.

RFX2 downregulates RASSF1 expression and YAP phosphorylation through Hippo signaling to promote immune escape in lung adenocarcinoma

OBJECTIVE

Regulatory Factor X (RFX) transcription factors have been implicated in different cancers. Ras association domain family (RASSF) has been shown clinical significance in lung cancer. This paper was to investigate the interaction of RFX2 and RASSF1 in lung adenocarcinoma (LUAD).

METHODS

The transcriptome differences of LUAD patients in GSE32863, GSE43458, and GSE21933 datasets were analyzed. A-549 and NCI-H358 cell lines after overexpression of RFX2 were co-cultured with activated CD8+ T cells, and the release of IFN-γ, GZMB, PRF1 by CD8+ T cells, and PD-L1 in the LUAD cells were detected. Cell viability, invasion, and apoptosis were analyzed by CCK-8, Transwell, and TUNEL assays. Dual-luciferase assay and ChIP were conducted to detect the interaction between RFX2 and RASSF1 promoter. An in vivo tumor model was constructed to monitor tumor growth. YAP protein levels and phosphorylation were measured. A-549 and NCI-H358 cells treated with DMSO or PY-60 after RFX2 overexpression were co-cultured with activated CD8+ T cells.

RESULTS

RFX2 was notably downregulated in LUAD. RFX2 overexpression increased infiltrating CD8+ T cells within transplanted tumors and inhibited immune escape, proliferation, and invasion of LUAD cells. RFX2 was enriched in the RASSF1 promoter, and RFX2 activated RASSF1 transcription by binding to the RASSF1 promoter. RASSF1 knockdown reversed the ability of RFX2 overexpression to inhibit immune escape. RFX2 depletion downregulated RASSF1, which reduced YAP phosphorylation, thus affecting the Hippo pathway to promote the immune escape.

CONCLUSION

RFX2 Loss in LUAD downregulates RASSF1 expression and YAP phosphorylation, thereby promoting immune escape through Hippo signaling.

Heparan sulfate regulates amphiregulin programming of tissue reparative lung mesenchymal cells during influenza A virus infection in mice

Amphiregulin (Areg), a growth factor produced by regulatory T (Treg) cells to facilitate tissue repair, contains a heparan sulfate (HS) binding domain. How HS, a highly sulfated glycan subtype that alters growth factor signaling, influences Areg repair functions is unclear. Here we report that inhibition of HS in various cell lines and primary lung mesenchymal cells (LMC) qualitatively alters Areg downstream signaling. Utilization of a panel of cell lines with targeted deletions in HS synthesis-related genes identifies the glypican family of HS proteoglycans as critical for Areg signaling. In the context of influenza A virus (IAV) infection in vivo, an Areg-responsive subset of reparative LMC upregulate glypican-4 and HS; conditional deletion of HS primarily within this LMC subset results in reduced repair characteristics following IAV infection. This study demonstrates that HS on a specific lung mesenchymal population is a mediator of Treg cell-derived Areg reparative signaling.

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.

Targeting TEAD would be a potential strategy for scarless wound repair: A preliminary study

Despite of decades of efforts, novel approaches are still limited to attenuate or prevent skin scarring. A previous report published in Science demonstrated that inhibition of YAP promotes scarless wound repair by regeneration. Due to the difficult drugability of targeting YAP, we speculated that inhibition of TEAD, a partner molecule of YAP, might exist similar therapeutic potential. Therefore, the aim of the study was to evaluate therapeutical effect of a novel inhibitor of TEAD auto-palmitoylation, VT107, on scar formation in a cutaneous wound healing model. Our findings confirmed VT107 exhibited favorable effect on preventing scarring, manifesting as reducing fibroblast proliferation and collagen denaturation, decreasing TGF-β1 and collagen deposition, as well as connective tissue growth factor (CTGF) expression. These findings provide a novel insight for the development of anti-scarring strategies. TEAD would become an ideal target for the treatment of scars.

Imperfect wound healing sets the stage for chronic diseases

Although the age of the genome gave us much insight about how our organs fail with disease, it also suggested that diseases do not arise from mutations alone; rather, they develop as we age. In this Review, we examine how wound healing might act to ignite disease. Wound healing works well when we are younger, repairing damage from accidents, environmental assaults, and battles with pathogens. Yet, with age and accumulation of mutations and tissue damage, the repair process can devolve, leading to inflammation, fibrosis, and neoplastic signaling. We discuss healthy wound responses and how our bodies might misappropriate these pathways in disease. Although we focus predominantly on epithelial-based (lung and skin) diseases, similar pathways might operate in cardiac, muscle, and neuronal diseases.

YAP/TAZ Signalling Controls Epidermal Keratinocyte Fate

The paralogues Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) control cell proliferation and cell fate determination from embryogenesis to ageing. In the skin epidermis, these proteins are involved in both homeostatic cell renewal and injury-induced regeneration and also drive carcinogenesis and other pathologies. YAP and TAZ are usually considered downstream of the Hippo pathway. However, they are the central integrating link for the signalling microenvironment since they are involved in the interplay with signalling cascades induced by growth factors, cytokines, and physical parameters of the extracellular matrix. In this review, we summarise the evidence on how YAP and TAZ are activated in epidermal keratinocytes; how YAP/TAZ-mediated signalling cooperates with other signalling molecules at the plasma membrane, cytoplasmic, and nuclear levels; and how YAP/TAZ ultimately controls transcription programmes, defining epidermal cell fate.

Research Progress of Fibroblasts in Human Diseases

Fibroblasts, which originate from embryonic mesenchymal cells, are the predominant cell type seen in loose connective tissue. As the main components of the internal environment that cells depend on for survival, fibroblasts play an essential role in tissue development, wound healing, and the maintenance of tissue homeostasis. Furthermore, fibroblasts are also involved in several pathological processes, such as fibrosis, cancers, and some inflammatory diseases. In this review, we analyze the latest research progress on fibroblasts, summarize the biological characteristics and physiological functions of fibroblasts, and delve into the role of fibroblasts in disease pathogenesis and explore treatment approaches for fibroblast-related diseases.

Activation of fetal-like molecular programs during regeneration in the intestine and beyond

Tissue regeneration after damage is generally thought to involve the mobilization of adult stem cells that divide and differentiate into progressively specialized progeny. However, recent studies indicate that tissue regeneration can be accompanied by reversion to a fetal-like state. During this process, cells at the injury site reactivate programs that operate during fetal development but are typically absent in adult homeostasis. Here, we summarize our current understanding of the molecular signals and epigenetic mediators that orchestrate "fetal-like reversion" during intestinal regeneration. We also explore evidence for this phenomenon in other organs and species and highlight open questions that merit future examination.

Heparan sulfate regulates amphiregulin signaling towards reparative lung mesenchymal cells during influenza A infection

Amphiregulin (Areg), a growth factor produced by regulatory T (Treg) cells to facilitate tissue repair/regeneration, contains a heparan sulfate (HS) binding domain. How HS, a highly sulfated glycan subtype that alters growth factor signaling, influences Areg repair/regeneration functions is unclear. Here we report that inhibition of HS in various cell lines and primary lung mesenchymal cells (LMC) qualitatively alters downstream signaling and highlights the existence of HS-dependent vs. -independent Areg transcriptional signatures. Utilizing a panel of cell lines with targeted deletions in HS synthesis-related genes, we found that the presence of the glypican family of heparan sulfate proteoglycans is critical for Areg signaling and confirmed this dependency in primary LMC by siRNA-mediated knockdown. Furthermore, in the context of influenza A (IAV) infection in vivo , we found that an Areg-responsive subset of reparative LMC upregulate glypican-4 and HS. Conditional deletion of HS primarily within this LMC subset resulted in reduced blood oxygen saturation following infection with IAV, with no changes in viral load. Finally, we found that co-culture of HS-knockout LMC with IAV-induced Treg cells results in reduced LMC responses. Collectively, this study reveals the essentiality of HS on a specific lung mesenchymal population as a mediator of Treg cell-derived Areg reparative signaling during IAV infection.

Pharmacological YAP activation promotes regenerative repair of cutaneous wounds

Chronic cutaneous wounds remain a persistent unmet medical need that decreases life expectancy and quality of life. Here, we report that topical application of PY-60, a small-molecule activator of the transcriptional coactivator Yes-associated protein (YAP), promotes regenerative repair of cutaneous wounds in pig and human models. Pharmacological YAP activation enacts a reversible pro-proliferative transcriptional program in keratinocytes and dermal cells that results in accelerated re-epithelization and regranulation of the wound bed. These results demonstrate that transient topical administration of a YAP activating agent may represent a generalizable therapeutic approach to treating cutaneous wounds.