NOTCH2 sensitizes the chondrocyte to the inflammatory response of tumor necrosis factor α

NOTCH2 disrupts the synovial fibroblast identity and the inflammatory response of epiphyseal chondrocytes

Notch signaling plays a fundamental role in the inflammatory response and has been linked to the pathogenesis of osteoarthritis in murine models of the disease and in humans. To address how Notch signaling modifies transcriptomes and cell populations, we examined the effects of NOTCH2 in chondrocytes from mice harboring a NOTCH2 gain-of-function mutation (Notch2tm1.1Ecan) and a conditional NOTCH2 gain-of-function model expressing the NOTCH2 intracellular domain (NICD2) from the Rosa26 locus (R26-NICD2 mice). Bulk RNA-Sequencing (RNA-Seq) of primary epiphyseal cells from both gain-of-function models established increased expression of pathways associated with the phagosome, genes linked to osteoclast activity in rheumatoid arthritis signaling and pulmonary fibrosis signaling. Expression of genes linked to collagen degradation was enhanced in Notch2tm1.1Ecan cells, while genes related to osteoarthritis pathways were increased in NICD2-expressing cells. Single cell (sc)RNA-Seq of cultured Notch2tm1.1Ecan cells revealed clusters of cells related to limb mesenchyme, chondrogenic cells and fibroblasts including articular synovial fibroblasts. Pseudotime trajectory revealed close associations among clusters in control cultures, but the cluster of articular/synovial fibroblasts was disrupted in cells from Notch2tm1.1Ecan mice. ScRNA-Seq showed similarities in the cluster distributions and pseudotime trajectories of NICD2-expressing and control cells, except for altered progression in a cluster of NICD2-expressing cells. In conclusion, NOTCH2 enhances the activity of pathways associated with inflammation in epiphyseal chondrocytes and disrupts the transcriptome profile of articular/synovial fibroblasts.

Advancing Osteoarthritis Research: Insights from Rodent Models and Emerging Trends

Osteoarthritis (OA) is a degenerative joint disease that affects millions of individuals worldwide, causing pain, disability, and a significant burden on public health. Preclinical research using animal models is essential to our understanding of the underlying pathogenesis of OA and developing therapeutic strategies. Rodent models, in particular, have become indispensable in studying OA due to their ability to mimic various features of human disease. This review provides an overview of commonly used rodent models of OA, including surgical induction (e.g., destabilization of the medial meniscus and anterior cruciate ligament transection), chemical induction (e.g., monoiodoacetate-induced cartilage degeneration), and genetically modified models. Additionally, age-related OA models that naturally develop OA-like symptoms in aged rodents are also discussed. Despite their utility, rodent models face limitations in fully recapitulating the complexity of human OA. Emerging trends in OA research, including the use of 3D imaging for joint analysis, molecular profiling for deeper insights into disease mechanisms, and advancements in biomarkers for early detection and treatment, are highlighted. These innovations provide new opportunities to refine existing models and enhance the translation of findings to clinical therapies. This critical review provides comprehensive information for researchers working in OA and related fields, promoting a better understanding of the available rodent models and their applications in OA research.

'QuickDASH' to find unique genes and biological processes associated with shoulder osteoarthritis: a prospective case-control study

OBJECTIVE

Osteoarthritis (OA) is a disease impacting the synovial joint complex, yet transcriptional changes specific to shoulder OA remain underexplored. This study aims to profile transcriptomic changes in periarticular tissues from patients undergoing shoulder replacement for OA. By correlating these profiles with QuickDASH scores-a validated measure of worsening shoulder function-this research seeks to understand the gene expression changes associated with clinical decline. Capsular tissue biopsies from shoulder OA patients were compared with those from a control group undergoing shoulder stabilization for recurrent instability. This investigation forms part of a larger transcriptomic analysis of painful shoulder conditions which will address the current gap in knowledge regarding the molecular and genetic underpinnings of shoulder OA, rotator cuff tears and cuff-tear arthropathy.

RESULTS

The analysis revealed that genes most strongly associated with increasing QuickDASH scores across tissues were linked to inflammation and stress response. Key pathways involved interleukins, chemokines, complement components, nuclear response factors, and immediate early response genes, reflecting a balance between pro- and anti-inflammatory signalling. Additionally, this study identified unique gene expression patterns in shoulder OA not previously observed in hip and knee OA, along with novel genes implicated in shoulder OA, highlighting areas for future targeted investigation. Trial registration This investigation has been registered with the Australian New Zealand Clinical Trials Registry (ANZCTR), registered on the 26th of March 2018, registration number: 12618000431224, accessible from: https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374665&isReview=true.

Extracellular Vesicles Derived Ectonucleoside Triphosphate Diphosphohydrolase 3 Alleviates Mitochondrial Dysfunction of Osteoarthritis Chondrocytes via Ectonucleotide Pyrophosphatase/Phosphodiesterase 1-Induced Suppression of the AKT/Notch2 Pathway

Osteoarthritis (OA) is the most common joint disease that usually starts from joint cartilage injury. Notch2, a versatile signaling in human development and diseases, was recently uncovered to be an important regulator in chondrocyte damage. However, in OA chondrocytes, how Notch2 activation is dysregulated is largely unknown. Here, integrated bioinformatic analysis was performed on GEO datasets (GSE199193 and GSE224255) to search potential extracellular vesicles (EVs) derived regulators of Notch2 in OA chondrocytes. Ectonucleoside triphosphate diphosphohydrolase 3 (Entpd3), a most differentially expressed gene both in LPS-induced macrophage EV and Notch2 mutant chondrocytes, was screened as the candidate regulator of Notch2 in OA chondrocytes. Gain-of-function experiments in cultured human chondrocytes revealed that recombinant Entpd3 protein and macrophage EV both had a protective effect on LPS-induced inflammation, oxidative stress, apoptosis, and collagen loss in chondrocytes. In terms of mechanism, Entpd3 directly interacted with ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) and suppressed AKT/Notch2-mediated mitochondrial dysfunction. Finally, we verified that either macrophage EV administration or Entpd3 overexpression was able to alleviate osteoarthritis in mice in vivo. In conclusion, Entpd3 is identified as a new regulator in OA, which alleviates mitochondrial dysfunction induced chondrocyte damage via ENPP1-induced suppression of the AKT/Notch2 pathway.

TNFα has differential effects on the transcriptome profile of selected populations in murine cartilage

Objective

To further our understanding of the role of tumor necrosis factor (TNF)α on the inflammatory response in chondrocytes.

Design

We explored the effects of TNFα on the transcriptome of epiphyseal chondrocytes from newborn C57BL/6 mice at the total and single cell (sc) resolution.

Results

Gene set enrichment analysis of total RNA-Seq from TNFα-treated chondrocytes revealed enhanced response to biotic stimulus, defense and immune response and cytokine signaling and suppressed cartilage and skeletal morphogenesis and development. scRNA-Seq analyzed 14,239 ​cells and 24,320 genes and distinguished 16 ​cell clusters. The more prevalent ones were constituted by limb bud and chondrogenic cells and fibroblasts comprising ∼73 ​% of the cell population. Genes expressed by joint fibroblasts were detected in 5 clusters comprising ∼45 ​% of the cells isolated. Pseudotime trajectory finding revealed an association between fibroblast and chondrogenic clusters which was not modified by TNFα. TNFα decreased the total cells recovered by 18.5 ​% and the chondrogenic, limb bud and mesenchymal clusters by 32 ​%, 27 ​% and 7 ​%, respectively. TNFα had profound effects on the insulin-like growth factor (IGF) axis decreasing Igf1, Igf2 and Igfbp4 and inducing Igfbp3 and Igfbp5, explaining an inhibition of collagen biosynthesis, cartilage and skeletal morphogenesis. Ingenuity Pathway Analysis of scRNA-Seq data revealed that TNFα enhanced the osteoarthritis, rheumatoid arthritis, pathogen induced cytokine storm and interleukin 6 signaling pathways and suppressed fibroblast growth factor signaling.

Conclusions

Epiphyseal chondrocytes are constituted by diverse cell populations distinctly regulated by TNFα to promote inflammation and suppression of matrix biosynthesis and growth.

Screening and identification of key biomarkers associated with endometriosis using bioinformatics and next-generation sequencing data analysis

Background

Endometriosis is a common cause of endometrial-type mucosa outside the uterine cavity with symptoms such as painful periods, chronic pelvic pain, pain with intercourse and infertility. However, the early diagnosis of endometriosis is still restricted. The purpose of this investigation is to identify and validate the key biomarkers of endometriosis.

Methods

Next-generation sequencing dataset GSE243039 was obtained from the Gene Expression Omnibus database, and differentially expressed genes (DEGs) between endometriosis and normal control samples were identified. After screening of DEGs, gene ontology (GO) and REACTOME pathway enrichment analyses were performed. Furthermore, a protein–protein interaction (PPI) network was constructed and modules were analyzed using the Human Integrated Protein–Protein Interaction rEference database and Cytoscape software, and hub genes were identified. Subsequently, a network between miRNAs and hub genes, and network between TFs and hub genes were constructed using the miRNet and NetworkAnalyst tool, and possible key miRNAs and TFs were predicted. Finally, receiver operating characteristic curve analysis was used to validate the hub genes.

Results

A total of 958 DEGs, including 479 upregulated genes and 479 downregulated genes, were screened between endometriosis and normal control samples. GO and REACTOME pathway enrichment analyses of the 958 DEGs showed that they were mainly involved in multicellular organismal process, developmental process, signaling by GPCR and muscle contraction. Further analysis of the PPI network and modules identified 10 hub genes, including vcam1, snca, prkcb, adrb2, foxq1, mdfi, actbl2, prkd1, dapk1 and actc1. Possible target miRNAs, including hsa-mir-3143 and hsa-mir-2110, and target TFs, including tcf3 (transcription factor 3) and clock (clock circadian regulator), were predicted by constructing a miRNA-hub gene regulatory network and TF-hub gene regulatory network.

Conclusions

This investigation used bioinformatics techniques to explore the potential and novel biomarkers. These biomarkers might provide new ideas and methods for the early diagnosis, treatment and monitoring of endometriosis.

NOTCH2 promotes osteoclast maturation and metabolism and modulates the transcriptome profile during osteoclastogenesis

Notch signaling plays a key regulatory role in bone remodeling and NOTCH2 enhances osteoclastogenesis, an effect that is mostly mediated by its target gene Hes1. In the present study, we explored mechanisms responsible for the enhanced osteoclastogenesis in bone marrow-derived macrophages (BMM) from Notch2tm1.1Ecan, harboring a NOTCH2 gain-of-function mutation, and control mice. Notch2tm1.1Ecan mice are osteopenic and have enhanced osteoclastogenesis. Bulk RNA-Seq and gene set enrichment analysis of Notch2tm1.1Ecan BMMs cultured in the presence of macrophage colony stimulating factor (M-CSF) and receptor activator of NF-κB ligand revealed enrichment of genes associated with enhanced cell metabolism, aerobic respiration, and mitochondrial function, all associated with osteoclastogenesis. These pathways were not enhanced in the context of a Hes1 inactivation. Analysis of single cell RNA-Seq data of pooled control and Notch2tm1.1Ecan BMMs treated with M-CSF or M-CSF and receptor activator of NF-κB ligand for 3 days identified 11 well-defined cellular clusters. Pseudotime trajectory analysis indicated a trajectory of clusters expressing genes associated with osteoclast progenitors, osteoclast precursors, and mature cells. There were an increased number of cells expressing gene markers associated with the osteoclast and with an unknown, albeit related, cluster in Notch2tm1.1Ecan than in control BMMs as well as enhanced expression of genes associated with osteoclast progenitors and precursors in Notch2tm1.1Ecan cells. In conclusion, BMM cultures display cellular heterogeneity, and NOTCH2 enhances osteoclastogenesis, increases mitochondrial and metabolic activity of osteoclasts, and affects cell cluster allocation in BMMs.

Insights into the Notch signaling pathway in degenerative musculoskeletal disorders: Mechanisms and perspectives

Degenerative musculoskeletal disorders are a group of age-related diseases of the locomotive system that severely affects the patient's ability to work and cause adverse sequalae such as fractures and even death. The incidence and prevalence of degenerative musculoskeletal disorders is rising owing to the aging of the world's population. The Notch signaling pathway, which is expressed in almost all organ systems, extensively regulates cell proliferation and differentiation as well as cellular fate. Notch signaling shows increased activity in degenerative musculoskeletal disorders and retards the progression of degeneration to some extent. The review focuses on four major degenerative musculoskeletal disorders (osteoarthritis, intervertebral disc degeneration, osteoporosis, and sarcopenia) and summarizes the pathophysiological functions of Notch signaling in these disorders, especially its role in stem/progenitor cells in each disorder. Finally, a conclusion will be presented to explore the research and application of the perspectives on Notch signaling in degenerative musculoskeletal disorders.