Biology subjects

Sochart, D.

Publications and source records attributed to Sochart, D..

3 recordsLinked to original sources

bioRxiv2026

CaMKII Activation Enhances Antioxidant Defence and Mitochondrial Function in human articular chondrocytes

BackgroundThe articular cartilage has limited vascular supply and repair capacity, making it particularly susceptible to reactive oxygen species (ROS)-driven oxidative damage. Excess ROS contributes to extracellular matrix breakdown and is a major factor in osteoarthritis (OA) progression. We previously identified Calcium/Calmodulin-dependent protein kinase II (CaMKII) as a regulator of cartilage homeostasis, prompting us to investigate its role during oxidative stress. MethodsPrimary adult human articular chondrocytes were isolated from OA cartilage. CaMKII activity was modulated using adenoviral overexpression of a constitutively active form of the kinase or of Autocamtide-2-related inhibitory peptide, a CaMKII inhibitor. Redox status and mitochondrial function were assessed by molecular and metabolic assays. ResultsOxidative stress increased CaMKII phosphorylation. CaMKII inhibition elevated cellular and mitochondrial ROS, whereas CaMKII activation enhanced mitochondrial respiration capacity, improved mitochondrial morphology, and was associated to NRF2 nuclear translocation. ConclusionCaMKII supports redox homeostasis in chondrocytes and may represent a therapeutic strategy to preserve cartilage integrity and delay disease onset.

cell biology↗

bioRxiv2024

microRNA-544a as a new modulator of the Wnt-signalling network in the articular cartilage and osteoarthritis

ObjectiveDetermining the effect of microRNA-544a (miR-544a) in articular chondrocytes isolated from patients affected by osteoarthritis (OA) and its role in the modulation of the Wnt signalling. MethodsArticular chondrocytes were isolated from patients undergoing joint replacement because of OA. Expression levels of miR-544a were measured by PCR and by in situ hybridization. Putative targets of miR-544a were confirmed by reporter assay and by qPCR in cells stimulated with a miR-544a mimic. The effect of miR-544a on chondrocyte metabolism was monitored by qPCR for phenotypic markers, protein expression levels of aggrecan neoepitopes/MMP-13 and modulation of alcian blue content in micromass cultures, upon stimulation with a miR-544a mimic. The expression levels of MMP-13 and Aggrecan neoepitopes in response to miR-544a stimulation was also measured in co-stimulation with Xav-939 and KN93, which are respectively {beta}-catenin and CaMKII inhibitors. ResultsOur results suggest that miR-544a enhances the activation of the Wnt-signalling in the articular chondrocytes, by downregulating the expression of components of the Wnt/{beta}-catenin destruction complex. The expression of miR-544a is higher in chondrocytes isolated from damaged areas of the articular cartilage removed from OA patients, and can be upregulated by pro-inflammatory and pro-fibrotic cytokines. miR-544a exerts a pro-catabolic effect of articular chondrocytes, which is rescued both by the inhibition of the Wnt/{beta}-catenin and Wnt/CaMKII signalling pathways. Conclusionour results point to miR-544a as a new, important modulator of the Wnt signalling network within the articular cartilage suggesting a key role for microRNAs in regulating how the multiple branches of the network and their interaction modulate cartilage homeostasis.

pharmacology and toxicology↗

bioRxiv2024

CaMKII induces an autophagy-dependent anabolic response in Articular Chondrocytes

ObjectiveThe objective of this study was to elucidate the role of Calcium calmodulin-dependent Kinase II (CaMKII) in articular chondrocytes and its involvement in osteoarthritis (OA) pathogenesis. By performing gain and loss of function experiments, the research aimed to determine how CaMKII modulates chondrocyte metabolism, anabolic and catabolic processes, hypertrophic differentiation, and autophagy within the articular cartilage. DesignArticular cartilage was harvested from patients undergoing joint replacement surgery for OA, and adult human articular chondrocytes (AHACs) were isolated and cultured. Recombinant adenoviruses were used to overexpress a constitutively active form of CaMKII{gamma} (AdCaMKII) or inhibit CaMKII activity (AdAIP). Various assays, including RT-PCR analysis, alcian blue staining of Micromass cultures, immunofluorescence, and Western blotting, were performed to assess the effects of CaMKII modulation on chondrocyte function. ResultsOverexpression of activated CaMKII{gamma} promoted anabolism, evidenced by increased expression of SOX9, COL2A1, and ACAN, and decreased MMP-13 levels. It also enhanced proteoglycan content in AHAC micromass cultures. Furthermore, CaMKII counteracted the catabolic effects of IL-1{beta} and preserved proteoglycan content. We also observed decreased chondrocyte proliferation and increased synthesis of hypertrophic marker Type X Collagen. CaMKII activation was found to induce autophagy, as indicated by increased phosphorylation of Beclin1 and decreased p62 expression. The anabolic effects of CaMKII were dependent on autophagy, as inhibition of autophagy with Bafilomycin prevented the CaMKII-induced increase in glycosaminoglycan content. ConclusionsCaMKII plays a significant role in modulating chondrocyte metabolism and maintaining cartilage homeostasis. It promotes anabolic processes, counteracts catabolic stimuli, and induces autophagy in articular chondrocytes. However, it also promotes hypertrophic differentiation, highlighting the complexity of CaMKII-mediated signalling in cartilage. Understanding these pathways could lead to new therapeutic strategies that leverage CaMKIIs anabolic potential while mitigating its pro-degenerative effects.

cell biology↗