Kdm6b regulates cartilage development and homeostasis through anabolic metabolism.

Epigenetic mechanisms have been reported to play key roles in chondrogenesis and osteoarthritis (OA) development. Here, we sought to identify specific histone demethylases that are involved and delineate the underlying mechanisms. We screened the expression of 17 distinct histone demethylases by quantitative real time PCR (qRT-PCR) during chondrogenic differentiation of C3H10T1/2 cells. The role of Kdm6b in cartilage development was then analysed with transgenic Col2a1-CreERT2;Kdm6bf/f . RNA-Seq was applied to explore the underlying changes in chondrocytes upon knockdown of Kdm6b. Experimental OA in mice was induced by destabilisation of the medial meniscus in C57BL/6J (wild type, Kdm6bf/f and Col2a1-CreERT2;Kdm6bf/f ) mice, either with intra-articular injection of shKdm6b lentivirus or after tamoxifen treatment. Mouse joints and human cartilage samples were used for histological analysis. Kdm6b expression was significantly increased during cartilage development. Col2a1-CreERT2;Kdm6bf/f mice displayed obvious skeletal abnormalities at E16.5 and E18.5 with intraperitoneal injection of tamoxifen at E12.5. RNA-Seq and qRT-PCR analyses revealed decreased expression of chondrocyte anabolic genes in Col2a1-CreERT2;Kdm6bf/f chondrocytes. The histological OA score was significantly higher in mice injected with Kdm6b short hairpin RNA lentivirus. Col2a1-CreERT2;Kdm6bf/f mice exhibited accelerated OA development at 8 and 12 weeks following surgical induction. The number of Kdm6b-positive chondrocytes was lower in both mice and human OA cartilage samples. These findings indicate that knockdown of Kdm6b in chondrocytes leads to abnormal cartilage development and accelerated OA progression via inhibition of the anabolic metabolism of chondrocytes. Understanding the epigenetic mechanism of joint cartilage development and homeostasis would be useful for development of new therapeutic modalities for OA.

Dai J ，Yu D ，Wang Y ，Chen Y ，Sun H ，Zhang X ，Zhu S ，Pan Z ，Heng BC ，Zhang S ，Ouyang H ... -  《-》

Curcumenol regulates Histone H3K27me3 demethylases KDM6B affecting Succinic acid metabolism to alleviate cartilage degeneration in knee osteoarthritis.

Cartilage metabolism dysregulation is a crucial driver in knee osteoarthritis (KOA). Modulating the homeostasis can mitigate the cartilage degeneration in KOA. Curcumenol, derived from traditional Chinese medicine Curcuma Longa L., has demonstrated potential in enhancing chondrocyte proliferation and reducing apoptosis. However, the specific mechanism of Curcumenol in treating KOA remains unclear. This study aimed to demonstrate the molecular mechanism of Curcumenol in treating KOA based on the transcriptomics and metabolomics, and both in vivo and in vitro experimental validations. In this study, a destabilization medial meniscus (DMM)-induced KOA mouse model was established. And the mice were intraperitoneally injected with Curcumenol at 4 and 8 mg/kg concentrations. The effects of Curcumenol on KOA cartilage and subchondral was evaluated using micro-CT, histopathology, and immunohistochemistry (IHC). In vitro, OA chondrocytes were induced with 10 μg/mL lipopolysaccharide (LPS) and treated with Curcumenol to evaluate the proliferation, apoptosis, and extracellular matrix (ECM) metabolism through CCK8 assay, flow cytometry, and chondrocyte staining. Furthermore, transcriptomics and metabolomics were utilized to identify differentially expressed genes (DEGs) and metabolites. Finally, integrating multi-omics analysis, virtual molecular docking (VMD), and molecular dynamics simulation (MDS), IHC, immunofluorescence (IF), PCR, and Western blot (WB) validation were conducted to elucidate the mechanism by which Curcumenol ameliorates KOA cartilage degeneration. Curcumenol ameliorated cartilage destruction and subchondral bone loss in KOA mice, promoted cartilage repair, upregulated the expression of COL2 while downregulated MMP3, and improved ECM synthesis metabolism. Additionally, Curcumenol also alleviated the damage of LPS on the proliferation activity and suppressed apoptosis, promoted ECM synthesis. Transcriptomic analysis combined with weighted gene co-expression network analysis (WGCNA) identified a significant downregulation of 19 key genes in KOA. Metabolomic profiling showed that Curcumenol downregulates the expression of d-Alanyl-d-alanine, 17a-Estradiol, Glutathione, and Succinic acid, while upregulating Sterculic acid and Azelaic acid. The integrated multi-omics analysis suggested that Curcumenol targeted KDM6B to regulate downstream protein H3K27me3 expression, which inhibited methylation at the histone H3K27, consequently reducing Succinic acid levels and improving KOA cartilage metabolism homeostasis. Finally, both in vivo and in vitro findings indicated that Curcumenol upregulated KDM6B, suppressed H3K27me3 expression, and stimulated collagen II expression and ECM synthesis, thus maintaining cartilage metabolism homeostasis and alleviating KOA cartilage degeneration. Curcumenol promotes cartilage repair and ameliorates cartilage degeneration in KOA by upregulating KDM6B expression, thereby reducing H3K27 methylation and downregulating Succinic Acid, restoring metabolic stability and ECM synthesis.

Chen W ，Xiao J ，Zhou Y ，Liu W ，Jian J ，Yang J ，Chen B ，Ye Z ，Liu J ，Xu X ，Jiang T ，Wang H ，Liu W ... -  《-》

H3K27me3 demethylases regulate in vitro chondrogenesis and chondrocyte activity in osteoarthritis.

Yapp C ，Carr AJ ，Price A ，Oppermann U ，Snelling SJ ... -  《-》

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is increased in osteoarthritis and regulates chondrocyte catabolic and anabolic activities.

We determined if the epidermal growth factor receptor ligand HB-EGF is produced in cartilage and if it regulates chondrocyte anabolic or catabolic activity. HB-EGF expression was measured by quantitative PCR using RNA isolated from mouse knee joint tissues and from normal and osteoarthritis (OA) human chondrocytes. Immunohistochemistry was performed on normal and OA human cartilage and meniscus sections. Cultured chondrocytes were treated with fibronectin fragments (FN-f) as a catabolic stimulus and osteogenic protein 1 (OP-1) as an anabolic stimulus. Effects of HB-EGF on cell signaling were analyzed by immunoblotting of selected signaling proteins. MMP-13 was measured in conditioned media, proteoglycan synthesis was measured by sulfate incorporation, and matrix gene expression by quantitative PCR. HB-EGF expression was increased in 12-month old mice at 8 weeks after surgery to induce OA and increased amounts of HB-EGF were noted in human articular cartilage from OA knees. FN-f stimulated chondrocyte HB-EGF expression and HB-EGF stimulated chondrocyte MMP-13 production. However, HB-EGF was not required for FN-f stimulation of MMP-13 production. HB-EGF activated the ERK and p38 MAP kinases and stimulated phosphorylation of Smad1 at an inhibitory serine site which was associated with inhibition of OP-1 mediated proteoglycan synthesis and reduced aggrecan (ACAN) but not COL2A1 expression. HB-EGF is a new factor identified in OA cartilage that promotes chondrocyte catabolic activity while inhibiting anabolic activity suggesting it could contribute to the catabolic-anabolic imbalance seen in OA cartilage.

Long DL ，Ulici V ，Chubinskaya S ，Loeser RF ... -  《-》

MicroRNA-34a-5p Promotes Joint Destruction During Osteoarthritis.

MicroRNA-34a-5p (miR-34a-5p) expression is elevated in the synovial fluid of patients with late-stage knee osteoarthritis (OA); however, its exact role and therapeutic potential in OA remain to be fully elucidated. This study was undertaken to examine the role of miR-34a-5p in OA pathogenesis. Expression of miR-34a-5p was determined in joint tissues and human plasma (n = 71). Experiments using miR-34a-5p mimic or antisense oligonucleotide (ASO) treatment were performed in human OA chondrocytes, fibroblast-like synoviocytes (FLS) (n = 7-9), and mouse OA models, including destabilization of the medial meniscus (DMM; n = 22) and the accelerated, more severe model of mice fed a high-fat diet and subjected to DMM (n = 11). Wild-type (WT) mice (n = 9) and miR-34a-knockout (KO) mice (n = 11) were subjected to DMM. Results were expressed as the mean ± SEM and analyzed by t-test or analysis of variance, with appropriate post hoc tests. P values less than 0.05 were considered significant. RNA sequencing was performed on WT and KO mouse chondrocytes. Expression of miR-34a-5p was significantly increased in the plasma, cartilage, and synovium of patients with late-stage OA and in the cartilage and synovium of mice subjected to DMM. Plasma miR-34a-5p expression was significantly increased in obese patients with late-stage OA, and in the plasma and knee joints of mice fed a high-fat diet. In human OA chondrocytes and FLS, miR-34a-5p mimic increased key OA pathology markers, while miR-34a-5p ASO improved cellular gene expression. Intraarticular miR-34a-5p mimic injection induced an OA-like phenotype. Conversely, miR-34a-5p ASO injection imparted cartilage-protective effects in the DMM and high-fat diet/DMM models. The miR-34a-KO mice exhibited protection against DMM-induced cartilage damage. RNA sequencing of WT and KO chondrocytes revealed a putative miR-34a-5p signaling network. Our findings provide comprehensive evidence of the role and therapeutic potential of miR-34a-5p in OA.

Endisha H ，Datta P ，Sharma A ，Nakamura S ，Rossomacha E ，Younan C ，Ali SA ，Tavallaee G ，Lively S ，Potla P ，Shestopaloff K ，Rockel JS ，Krawetz R ，Mahomed NN ，Jurisica I ，Gandhi R ，Kapoor M ... -  《-》