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Inflammatory macrophage-derived extracellular vesicles trigger the non-canonical pyroptosis pathway in chondrocytes leading to cartilage catabolism and degeneration in osteoarthritis

ABSTRACT: The severity of osteoarthritis (OA) and cartilage degeneration are highly correlated with the development of synovitis, which is mediated by the activity of inflammatory macrophages. A better understanding of intercellular communication between inflammatory macrophages and chondrocytes should aid in the discovery of novel therapeutic targets. Here, we explored the pathological role of inflammatory macrophage-extracellular vesicles (EVs) in cartilage degeneration. Macrophages were stimulated by treatment with bacterial lipopolysaccharides to mimic the state of inflammatory macrophages and the resulting EVs (M-LPS EVs) were harvested for chondrocyte stimulation and intraarticular injection in a mouse model. This stimulation resulted in increased catabolism of chondrocytes and cartilage degeneration. Consistently, RNA-seq analyses of stimulated chondrocytes indicated that upregulated genes are mainly categorized into apoptotic process and TNF-signaling pathway which suggests the induction of apoptotic process. These chondrocytes exhibited a significant elevation in the expression of pyroptosis-related molecules that were correlated with the expression of chondrocyte catabolic factors. The disruption of caspase-11 significantly alleviated pyroptotic and catabolic processes in stimulated chondrocytes and the pathological changes in collagenase-induced OA model. Our results provide a new insight into the pathological mechanisms of OA and suggest that non-canonical pyroptosis signaling in chondrocytes represents an attractive therapeutic target for future treatment.

ORGANISM(S): Mus musculus

PROVIDER: GSE199193 | GEO | 2023/09/20

REPOSITORIES: GEO

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Project description:Osteoarthritis (OA) of the hand is a common disease resulting in pain and impaired function. The pathogenesis of hand OA (HOA) is elusive and models to study it have not been described so far. Culture of chondrocytes is a model to study the development of cartilage degeneration, which is a hallmark of OA and well established in OA of the knee and hip. In the current study we investigated the feasibility human chondrocyte culture derived from proximal interphalangeal (PIP) finger joints of dissecting room cadavers. Index and middle fingers without signs of osteoarthritis were obtained from 30 cadavers using two different protocols. Hyaline cartilage from both articulating surfaces of the proximal interphalangeal (PIP) joint was harvested and digested in collagenase. Cultured chondrocytes were monitored for contamination, viability, and expression of chondrocyte specific genes. Chondrocytes derived from knee joints of the cadavers were cultured under identical conditions. Gene expression comparing chondrocytes from PIP and knee joints was carried out using Affymetrix GeneChip Human 2.0 ST arrays. The resulting differentially expressed genes were validated by real-time PCR and immunohistochemistry.Chondrocytes harvested up to 101 hours after death of the donors were viable. mRNA expression of collagen 2A1, aggrecan and Sox9 was significantly higher in chondrocytes as compared to cultured fibroblasts. Comparison of gene expression by chondrocytes from PIP and knee joints yielded 528 differentially expressed genes. Chondrocytes from the same joint region had a higher grade of similarity than chondrocytes of the same individual. These results were validated using real-time PCR and immunohistochemistry.We demonstrate for the first time a reliable method for culture of chondrocytes derived from PIP joints. PIP chondrocytes show a specific gene expression pattern and could be used as tool to study cartilage degeneration in HOA. Three samples of cultured chondrocytes from knee and proximal interphalangeal finger joints were compared. Gene expression of the four most differentially regulated genes was confirmed by real-time PCR in 10 independent samples.

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Project description:Avascular soft tissues of the skeletal system, including articular cartilage, have an extremely limited healing capacity, in part due to their low metabolic activity. No drugs are available that can prevent or slow the development of osteoarthritis (OA) after joint injury. Therefore, mesenchymal stromal cell (MSC)-based regenerative therapies are increasingly common in the treatment of OA, but questions regarding their clinical efficacy and mechanisms of action remain unanswered. Our group recently reported that mitochondrial dysfunction is one of the earliest responses of cartilage to injury, resulting in chondrocyte death, extracellular matrix degeneration, and ultimately OA. MSCs have been found to rescue injured cells and improve healing by donating healthy mitochondria in highly metabolic tissues, but mitochondrial transfer has not been investigated in cartilage. To investigate how gene expression changes in stressed chondrocytes, and therefore how they might elicit mitochondrial donation from MSCs, we developed a custom quantitative PCR panel of relevant genes involved in chondrocyte metabolism and OA. We cultured chondrocytes under conditions known induce chondrocyte mitochondrial dysfunction, including stimulation with rotenone/antimycin and non-physiologic culture conditions (hyperoxia and hyperglycemia). We found that expression of gap junction alpha 1 (GJA1), the gene that encodes the Cx43 protein, was increased in hyperoxia. The senescence associated markers, cyclin-dependent kinase inhibitor 2A (CDKN2A) and tissue inhibitor of metalloproteinases 1 (TIMP1), were also increased in hyperoxia. In addition, hyperoxia caused chondrocytes to increase the expression of the antioxidant enzyme, SOD2. This work provides insights into the chemical and environmental conditions that can alter gene expression in chondrocytes. Further, this provides supporting evidence to our hypothesis that stressed chondrocytes may trigger mitochondrial donation from MSCs may via direct or indirect signaling involving the inflammation- and senescence-related genes identified in the present study.

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Inflammatory macrophage-derived extracellular vesicles trigger the non-canonical pyroptosis pathway in chondrocytes leading to cartilage catabolism and degeneration in osteoarthritis

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