YAP activation inhibits inflammatory signalling and cartilage breakdown associated with reduced primary cilia expression

Electrospun PLGA/PCL Nanofiber Film Loaded with LPA Promotes Full-Layer Wound Healing by Regulating the Keratinocyte Pyroptosis

Electrospun nanofibers have a number of qualities that make them a suitable choice for skin wound healing. Lysophosphatidic acid (LPA) stimulates the keratinocytes and fibroblasts to proliferate, differentiate, and migrate and enhances skin wound healing. Here, we developed the electrospun scaffolds contained in polycaprolactone (PCL) and polylactic-co-glycolic acid (PLGA). The scaffolds loaded with LPA nanoparticles retained a porous nanofiber structure and showed better physicochemical properties and biocompatibility. The scaffold continuously releases LPA to quickly initiate cell signaling and maintain long-term anti-inflammatory activity. In this study, we found that PP scaffold with LPA reduces the disordered collagen deposition and the thickness of the newborn epidermis, improves skin healing, and reduces scar formation. Explaining the mechanism of LPA mineralized tissue regeneration in skin wound healing, LPA inhibited the pyroptosis of keratinocyte, a cell death process that induces inflammation and scar formation by inhibiting the expression of TNF-α and β-catenin proteins. Thus, the electrospun PP scaffold with LPA can be potentially developed as a therapeutic avenue to target skin wound healing.

BMAL1 alleviates sepsis-induced AKI by inhibiting ferroptosis

BACKGROUND

The role of BMAL1 in various diseases remains unclear, particularly its impact on sepsis-induced acute kidney injury (AKI). This study aims to investigate the role of BMAL1 in sepsis-induced AKI and its potential effects on cell ferroptosis. Initially, we assessed BMAL1 expression levels in mice treated with sepsis-induced AKI (via LPS injection) and in LPS-stimulated renal tubular epithelial cells. Subsequently, we explored the correlation between BMAL1 and ferroptosis using sequencing technology, validating our findings throughout experimental approaches. To further elucidate BMAL1's specific effects on AKI-related ferroptosis, we constructed BMAL1 overexpression models in mice and cells, analysing its impact on AKI and ferroptosis both in vivo and in vitro. Furthermore, using transcriptome sequencing technology, we identified key BMAL1-regulated genes and their associated biological pathways, validating these findings through in vivo and in vitro experiments.

RESULTS

Our findings indicate decreased BMAL1 expression in sepsis-induced AKI. BMAL1 overexpression effectively mitigated renal tubular injury by reducing ferroptosis levels in renal tubular epithelial cells. Using transcriptome sequencing and ChIP-qPCR technology, we identified YAP as a target of BMAL1. The overexpression of BMAL1 significantly reduced the transcriptional activity of YAP and inhibited the Hippo signalling pathway. Treatment with the Hippo inhibitor Verteporfin (VP) reversed the BMAL1-downregulation-induced damage. Additionally, our study revealed that YAP positively regulates ACSL4 gene expression and its downstream signalling pathways.

CONCLUSION

This study demonstrates that BMAL1 overexpression alleviates renal tubular epithelial cell injury and ferroptosis by inhibiting YAP expression and the Hippo pathway, thereby exerting protective effects in sepsis-induced AKI. These findings underscore the therapeutic potential of targeting BMAL1 in managing sepsis-induced AKI.

Genetically predicted circulating linoleic acid levels and risk of osteoarthritis: a two-sample mendelian randomization study

OBJECTIVES

This study aimed to provide insight into the effect of genetically predicted linoleic acid (LA) levels on osteoarthritis (OA).

METHODS

The LA dataset was obtained from the UK Biobank (UKBB) consortium and contained 114,999 samples. The OA discovery dataset was derived from MRC-IEU consortium and included 38,472 cases and 424,461 controls. The OA validation set was derived from a summary-level genome-wide association study (GWAS) and included 39,427 cases and 378,169 controls. Genetic variants strongly associated with LA (p < 5 × 10- 8) were extracted as instrumental variables (IVs). The inverse variance weighted (IVW) approach was adopted as the primary analysis method in this study. In addition, multiple sensitivity analysis methods were used to assess the reliability of our results.

RESULTS

The IVW approach showed that circulating LA levels were negatively associated with OA risk in the discovery set (odds ratio (OR) = 0.993, 95% confidence interval (95% CI): 0.988-0.998, p = 0.011). A consistent result was obtained in the validation set (OR = 0.904, 95%CI: 0.845-0.967, p = 0.003). These results were validated by sensitivity analysis.

CONCLUSION

This study provides new evidence for the causal relationship between LA and OA, which provides new insights for the treatment of OA.

An in vitro study of the impact of IL-17A and IL-22 on ciliogenesis in nasal polyps epithelium via the Hippo-YAP pathway

BACKGROUND

Cilia loss and impaired motile ciliary functions are among the typical pathological features of chronic rhinosinusitis with nasal polyps (CRSwNP). IL17A and IL22 are the canonical cytokines of type 3 inflammation, exhibiting similar functional effects on epithelial cells. In this study, we sought to examine the effects of IL17A and IL22 on ciliated cells and investigate the potential involvement of Hippo-YAP signaling in their influence on ciliogenesis.

METHODS

We assessed both the mRNA and protein expression levels of IL17A and IL22 in nasal tissues obtained from patients with CRSwNP and compared them to those from healthy controls. To further explore the impact of IL17A and IL22, we established a primary human nasal epithelial cell model using different concentrations (2 ng/mL, 10 ng/mL, 50 ng/mL) for a duration of 28 days in an air-liquid interface culture. Additionally, we employed the inhibitor verteporfin to investigate whether IL17A and IL22 exert their effects on ciliated cells via the Hippo-YAP pathway.

RESULTS

The mRNA and protein levels of IL17A and IL22 in CRSwNP were significantly higher than those in healthy controls, revealing a robust correlation between IL17A and IL22. YAP was highly expressed in the nucleus of ciliated cells in CRSwNP and displayed a positive correlation with clinical symptoms. Both IL17A and IL22 were found to reduce the number of ciliated cells. IL17A, but not IL22, suppressed ciliogenesis by disrupting the proper development and docking of the basal body of ciliated cells, resulting in motile ciliary dysfunctions. Furthermore, the expression of YAP within the nucleus of ciliated cells gradually declined as these cells reached the final stage of differentiation. However, this process was obstructed by IL17A only. YAP inhibitors, such as verteporfin, markedly reversed the effects of IL17A by increasing the proportion of ciliated cells, suppressing nuclear YAP expression in these cells, and enhancing ciliary beating frequency.

CONCLUSIONS

Both IL17A and IL22 are overexpressed in nasal epithelium of CRSwNP, which is associated with the impairment of epithelial cell differentiation. Furthermore, IL17A has been shown to exert a disruptive effect on morphogenesis of motile cilia via activation of YAP.

Hippo-PKCζ-NFκB signaling axis: A druggable modulator of chondrocyte responses to mechanical stress

Recent studies have implicated a crucial role of Hippo signaling in cell fate determination by biomechanical signals. Here we show that mechanical loading triggers the activation of a Hippo-PKCζ-NFκB pathway in chondrocytes, resulting in the expression of NFκB target genes associated with inflammation and matrix degradation. Mechanistically, mechanical loading activates an atypical PKC, PKCζ, which phosphorylates NFκB p65 at Serine 536, stimulating its transcriptional activation. This mechanosensitive activation of PKCζ and NFκB p65 is impeded in cells with gene deletion or chemical inhibition of Hippo core kinases LATS1/2, signifying an essential role of Hippo signaling in this mechanotransduction. A PKC inhibitor AEB-071 or PKCζ knockdown prevents p65 Serine 536 phosphorylation. Our study uncovers that the interplay of the Hippo signaling, PKCζ, and NFκB in response to mechanical loading serves as a therapeutic target for knee osteoarthritis and other conditions resulting from mechanical overloading or Hippo signaling deficiencies.

Alkaptonuria: From Molecular Insights to a Dedicated Digital Platform

Alkaptonuria (AKU) is a genetic disorder that affects connective tissues of several body compartments causing cartilage degeneration, tendon calcification, heart problems, and an invalidating, early-onset form of osteoarthritis. The molecular mechanisms underlying AKU involve homogentisic acid (HGA) accumulation in cells and tissues. HGA is highly reactive, able to modify several macromolecules, and activates different pathways, mostly involved in the onset and propagation of oxidative stress and inflammation, with consequences spreading from the microscopic to the macroscopic level leading to irreversible damage. Gaining a deeper understanding of AKU molecular mechanisms may provide novel possible therapeutical approaches to counteract disease progression. In this review, we first describe inflammation and oxidative stress in AKU and discuss similarities with other more common disorders. Then, we focus on HGA reactivity and AKU molecular mechanisms. We finally describe a multi-purpose digital platform, named ApreciseKUre, created to facilitate data collection, integration, and analysis of AKU-related data.

The role of YAP/TAZ on joint and arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are two common forms of arthritis with undefined etiology and pathogenesis. Yes-associated protein (YAP) and its homolog transcriptional coactivator with PDZ-binding motif (TAZ), which act as sensors for cellular mechanical and inflammatory cues, have been identified as crucial players in the regulation of joint homeostasis. Current studies also reveal a significant association between YAP/TAZ and the pathogenesis of OA and RA. The objective of this review is to elucidate the impact of YAP/TAZ on different joint tissues and to provide inspiration for further studying the potential therapeutic implications of YAP/TAZ on arthritis. Databases, such as PubMed, Cochran Library, and Embase, were searched for all available studies during the past two decades, with keywords "YAP," "TAZ," "OA," and "RA."

Regulation of Oxygen Tension as a Strategy to Control Chondrocytic Phenotype for Cartilage Tissue Engineering and Regeneration

Cartilage defects and osteoarthritis are health problems which are major burdens on health care systems globally, especially in aging populations. Cartilage is a vulnerable tissue, which generally faces a progressive degenerative process when injured. This makes it the 11th most common cause of global disability. Conservative methods are used to treat the initial phases of the illness, while orthopedic management is the method used for more progressed phases. These include, for instance, arthroscopic shaving, microfracturing and mosaicplasty, and joint replacement as the final treatment. Cell-based implantation methods have also been developed. Despite reports of successful treatments, they often suffer from the non-optimal nature of chondrocyte phenotype in the repair tissue. Thus, improved strategies to control the phenotype of the regenerating cells are needed. Avascular tissue cartilage relies on diffusion for nutrients acquisition and the removal of metabolic waste products. A low oxygen content is also present in cartilage, and the chondrocytes are, in fact, well adapted to it. Therefore, this raises an idea that the regulation of oxygen tension could be a strategy to control the chondrocyte phenotype expression, important in cartilage tissue for regenerative purposes. This narrative review discusses the aspects related to oxygen tension in the metabolism and regulation of articular and growth plate chondrocytes and progenitor cell phenotypes, and the role of some microenvironmental factors as regulators of chondrocytes.

Yes-Associated Protein Mediates the Transition from Inflammation to Fibrosis in Graves' Orbitopathy

Background: In Graves' orbitopathy (GO), localized orbital inflammation within the fixed orbit often leads to a fibrotic phenotype resulting in restrictive myopathy or refractory proptosis. However, the molecular pathways related to the transition from inflammation to fibrosis in GO are less understood. Yes-associated protein (YAP) and its homolog, transcriptional coactivator with PDZ-binding motif (TAZ; a Hippo pathway effector), are critical mechanosensors of mechanical stimuli and activate signaling cascades for cell proliferation, differentiation, and transformation. In this study, we aimed to examine the role of YAP in both inflammatory and fibrotic GO pathogenesis. Methods: Based on RNA sequencing performed on freshly obtained orbital adipose tissue from patients with GO and healthy individuals, Gene Ontology analysis and gene set-enrichment analysis were performed to analyze gene-expression differences between GO and normal orbital tissues. The role of YAP in GO-related inflammation and fibrosis was studied in primary cultured orbital fibroblasts. The effects of interleukin-1β (IL-1β)-induced inflammation and transforming growth factor-beta (TGF-β)-induced fibrosis on YAP expression were evaluated using real-time polymerase chain reaction and Western blotting analyses. The effects of YAP on inflammatory and fibrotic responses were also examined by YAP silencing or treatment with pharmacological YAP inhibitors. Results: RNA sequencing revealed enhanced YAP expression in GO orbital tissues. Gene Ontology analysis indicated that "response to mechanical stimulus"-related genes were overexpressed in GO orbital tissues, along with those enriched for the "adipose proliferation," "inflammatory responses," and "hormone stimulus responses" terms. IL-1β did not enhance YAP expression, and YAP silencing decreased IL-1β-induced IL-6 expression while increasing prostaglandin-endoperoxide synthase 2 expression, leading to paradoxical pro-inflammatory effects. Conversely, TGF-β enhanced YAP expression, and YAP silencing and pharmacological YAP inhibitor (cerivastatin, verteporfin, TED-347, and CA3) treatment significantly reduced TGF-β-induced myofibroblast differentiation and collagen formation. Conclusion: YAP, a mechanotransducer responding to mechanical stimuli, was strongly expressed in GO orbital tissues, and YAP was induced by TGF-β in orbital fibroblasts. Our study establishes YAP as a novel mediator of GO pathobiology, potentially mediating the transition from early inflammation to chronic fibrosis in GO. The finding that YAP inhibition suppressed TGF-β-induced fibrotic response suggests YAP as a therapeutic target against the fibrotic mechanism of GO.

The roles of the Hippo-YAP signalling pathway in Cartilage and Osteoarthritis

Osteoarthritis (OA) is an age-related disease, characterized by cartilage degeneration. The pathogenesis of OA is complicated and the current therapeutic approaches for OA are limited. Cartilage, an integral part of the skeletal system composed of chondrocytes, is essential for skeletal development, tissue patterning, and maintaining the normal activity of joints. The development, homeostasis and degeneration of cartilage are tightly associated with OA. Over the past decade, accumulating evidence indicates that Hippo/YAP is a vital biochemical signalling pathway that strictly governs tissue development and homeostasis. The joint tissues, especially for cartilage, are sensitive to changes of Hippo/YAP signalling. In this review, we summarize the role of Hippo/YAP signalling in cartilage and discuss its involvement in OA progression from points of cartilage degradation, subchondral bone remodeling, and synovial alteration. We also highlight the potential therapeutic implications of Hippo/YAP signalling and further discuss current limitations and controversy on Hippo/YAP-based application for OA treatment.