Defois, A. | bioRxiv Science

bioRxiv2026

Molecular and spatial profiling identifies immune endotypes for the stratification of OA patients

Osteoarthritis (OA) is a prevalent and heterogeneous joint disease in which synovial inflammation drives structural progression and pain. Despite the recognized heterogeneity of OA, the cellular and molecular organization of synovial tissue remains poorly characterized and defining distinct histological and immune endotypes could guide precision medicine and therapeutic targeting. We show that histologically defined synovial pathotypes are conserved across independent cohorts and correspond to distinct molecular immune endotypes. Integration of bulk and spatial transcriptomics with proteomics revealed niche-specific gene and protein signatures, reflecting the anatomical and functional diversity of OA synovium. The lympho-myeloid pathotype was characterized by mature ectopic lymphoid structures containing CD21+CD23+ follicular dendritic cells, spatially organized T and B cell zones, and clonally expanded T and B cells with shared immune cell receptor motifs, consistent with local adaptive immune activity correlating with radiological joint damage. These findings highlight how immune organization and cellular composition shape OA pathogenesis and provide a framework for endotype-guided stratification and therapeutic targeting.

immunology↗

bioRxiv2025

Multimodal analysis of osteoarthritic chondrocytes reveals mitochondrial alterations and patient-specific OxPhos response to bezafibrate

BackgroundOsteoarthritis (OA) is the most common joint disease and is characterized by bone remodeling, cartilage degradation and synovial inflammation. To date, no effective treatment is available for this debilitating condition. Recent evidence suggests that mitochondrial dysfunction, including oxidative phosphorylation (OxPhos) failure, accumulates within OA chondrocytes and may contribute to pathogenesis. In this context, mitochondrial dysfunction may be associated with observable changes in mitochondrial number, size and shape. However, a comprehensive characterization of mitochondria-related features during OA, from tissue-to-cell level, is still lacking. Addressing these gaps could inform therapeutic strategies, such as the partial restoration of OxPhos, which has been proposed as a therapeutic approach. MethodsHere, we employed a multimodal approach that included Fourier-transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM) and real-time cellular metabolic assays (Seahorse technology) to better characterize mitochondrial parameters in cartilage during OA. Two types of experimental models were used using human cartilage: (1) undamaged versus damaged OA zones, and (2) non-OA versus OA samples. In addition, we investigated the potential of repurposing bezafibrate, an approved peroxisome proliferator-activated receptor (PPAR) agonist, as a mitochondria-based therapy to restore OxPhos in OA chondrocytes. ResultsWe identified that OA chondrocytes exhibit a decrease in glycogen deposits surface, and an increased number of mitochondria alongside an OxPhos dysfunction compared to non-OA chondrocytes. A similar trend toward glycogen storage deficiency and increased mitochondria number was observed in OA chondrocytes from damaged cartilage areas. Furthermore, multivariate analyses revealed that the clinical profiles of OA patients allowed OA chondrocytes to be separated into responders and non-responders to bezafibrate. ConclusionWe provide evidence that OA chondrocytes display decreased glycogen deposits surface, increased mitochondrial number and OxPhos dysfunction. Additionally, we identified that bezafibrate, a PPAR agonist, improved OxPhos function in a subgroup of OA chondrocytes derived from patients.

pathology↗