Biology subjects

Brochard, S.

Publications and source records attributed to Brochard, S..

3 recordsLinked to original sources

bioRxiv2025

Systemic immune alterations in a murine experimental model of osteoarthritis

Osteoarthritis (OA) is accompanied by an inflamed synovium containing macrophages, dendritic cells, T and B lymphocytes. Macrophages predominate and drive cytokine-mediated cartilage catabolism, while T cells and B cells, though fewer, may shape chronic adaptive responses. However, systemic immune contributions, particularly within peripheral lymphoid organs such as the spleen, remain poorly characterized. Our study aims to profile systemic immune changes in experimental OA induced by injection of mono-iodoacetate (MIA) in mouse paw. At day 56 post-OA induction, analysis of splenocytes showed that macrophages and conventional dendritic cells (cDC1 and cDC2) displayed a significant downregulation of MHCII expression, suggesting a negative feedback mechanism that limits chronic T cell activation. OA is also associated with an increase in total DCs including mainly MHCII negative tolerogenic DCs. Notably, while the proportion of CD11b- tolerogenic DCs was reduced, CD11blow tolerogenic DCs markedly expanded in OA animals. Expression level of the CD11b integrin was upregulated on macrophages and cDC2 in MIA-induced OA mice potentially facilitating their adhesion and migration toward inflamed joint. OA mice showed a significant reduction in total splenic leukocytes, primarily due to a loss of B cells, while total T cell numbers remained stable. However, T cell composition shifted: CD4+ T cells including activated and regulatory subsets decreased, whereas activated CD8+ T cells increased. This indicates a systemic imbalance favoring cytotoxic over regulatory immune activity, possibly linked to chronic immune stress or redistribution of lymphocytes to inflamed joint. In conclusion, our data reveals that chronic OA induces a coordinated remodeling of systemic innate and adaptive immunity. These systemic immune dysregulations could reveal new biomarkers or therapeutic targets.

physiology↗

bioRxiv2025

Epigenetic Regulation of Chondrogenesis: JMJD3 and UTX as Key Targets for Gene-Modified Mesenchymal Stem Cell Therapy in Cartilage Tissue Engineering

Osteoarthritis is a major cause of disability in older adults, and among the promising therapeutic strategies, cartilage tissue engineering shows great potential. Histone methylation plays a critical role in cartilage development, making it an appealing target for improving cartilage engineering protocols. In this study, we evaluated the roles of JMJD3 (KDM6B) and UTX (KDM6A), both demethylases of histone H3 at lysine 27 (H3K27), in chondrogenesis and their application in gene-modified mesenchymal stem cell therapy for cartilage tissue engineering. Using high-throughput analyses such as ChIP-Seq and whole-transcriptome microarray, we explored the functions of JMJD3 and UTX in human bone marrow-derived mesenchymal stem cells (hBM-MSC) undergoing chondrogenesis. We investigated the impact of inhibiting JMJD3 and UTX with the pharmacological inhibitor GSK-J4 or using siRNA. Additionally, the effects of transiently transfecting JMJD3 or UTX expression vectors were assessed both in vitro and in vivo, following the implantation of hBM-MSC embedded in alginate in nude mice. Our findings revealed that JMJD3 is specifically upregulated during chondrogenesis in hBM-MSC, and is crucial for this differentiation process. In contrast, UTX was found to be dispensable for chondrogenesis. Nevertheless, both JMJD3 and UTX share the ability to demethylate similar gene loci, thereby promoting the expression of chondrogenic signature genes, which suggests functional redundancy. Notably, the genes encoding these H3K27me3 demethylases emerge as strong candidates for enhancing gene-modified mesenchymal stem cell therapy for cartilage tissue engineering, as their overexpression during chondrogenesis significantly increased the formation of thicker cartilage discs enriched with type II collagen. In conclusion, this study provides important insights into the epigenetic regulation of chondrogenesis, especially regarding the role of H3K27me3 demethylases. We demonstrate that, although JMJD3 and UTX have overlapping targets, only JMJD3 is critical for the chondrogenesis process. Additionally, the findings emphasize the potential of transient JMJD3 transduction, along with a lesser emphasis on UTX, as effective strategies for improving gene-modified mesenchymal stem cell therapy in cartilage tissue engineering.

developmental biology↗

bioRxiv2025

Inhibiting EZH2 Alleviates Osteoarthritis and Pain in an Experimental Murine Model Through Modulating Synovial and Macrophage Inflammation, Axon Guidance, and Osteoclastogenesis

Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase responsible for H3K27 trimethylation, has emerged as a potential therapeutic target in osteoarthritis (OA). However, its contribution to the multicellular mechanisms driving joint degeneration and pain remains poorly understood. Here, we investigated the effects of pharmacological EZH2 inhibition in a pain-relevant murine OA model and explored its cellular and molecular consequences across OA-associated cell populations. OA was induced in mice by intra-articular monosodium iodoacetate (MIA) injection followed by local administration of the EZH2 inhibitor EPZ-6438. Joint pathology and pain-related behaviors were assessed by histological and functional analyses. Mechanistic studies were performed in primary human OA fibroblast-like synoviocytes and bone marrow-derived cells using targeted gene expression analyses, proteomics and ChIP-seq approaches. EZH2 inhibition reduced cartilage damage, synovial inflammation and pain-related behavioral alterations in vivo. In OA synoviocytes, EPZ-6438 decreased the expression of inflammatory, catabolic and pain-associated mediators while promoting autophagy-related responses. Proteomic and ChIP-seq analyses revealed EZH2-dependent regulation of inflammatory pathways, cellular homeostasis and neuronal-associated processes, including axon guidance-related pathways. ChIP-seq further identified inflammation-dependent EZH2 recruitment to promoters of neurodevelopmental regulators, including PAX6, suggesting a potential contribution of EZH2 to neuronal-associated mechanisms in OA. In addition, EZH2 inhibition reduced macrophage inflammatory activation and osteoclast differentiation. Together, these findings identify EZH2 as a candidate epigenetic regulator linking inflammatory, neuroimmune and osteoimmune pathways across the osteoarthritic joint. Targeting EZH2 may represent a therapeutic strategy to simultaneously modulate joint inflammation, remodeling and pain-associated pathways.

physiology↗