Expression profiles of genes involved in apoptosis and selenium metabolism in articular cartilage of patients with Kashin–Beck osteoarthritis

Kashin–Beck disease (KBD) is a special type of endemic osteoarthritis. It has been suggested that alterations in selenium metabolism and apoptosis play a role in KBD. However, the underlying molecular mechanism remains largely unclear. We performed a microarray analysis using RNA isolated from cartilages of KBD patients and healthy controls, through Significance Analysis of Microarray (SAM) software. Functional gene networks and crucial molecules associated with differentially expressed genes were investigated via Ingenuity Pathway Analysis (IPA) and hub gene analysis. Quantitative real-time PCR was used to check the validation of chip test. We identified 52 up-regulated apoptosis-related genes and 26 down-regulated selenium-related genes between KBD and controls, and these genes associated with the “MYC-mediated apoptosis signaling pathway”. We confirmed the results from array studies with quantitative real-time PCR analysis. Our results suggest that abnormal regulation of selenium metabolism and apoptosis through the MYC mediated signaling pathway contributes to the pathogenesis of KBD, but the relationship between apoptosis gene and selenium gene was not found.     

Trans-omics pathway analysis suggests that eQTLs contribute to chondrocyte apoptosis of Kashin–Beck disease through regulating apoptosis pathway expression

Kashin–Beck disease (KBD) is a serious osteoarthropathia, mainly characterized by excessive chondrocyte necrosis and apoptosis. The molecular signaling pathways underlying KBD excessive chondrocyte apoptosis remain unclear, leading to a lack of effective medical interventions now. To clarify whether expression quantitative trait loci (eQTLs) contribute to excessive chondrocyte apoptosis of Kashin–Beck disease through regulating the expression of apoptosis pathways. We conducted a genome-wide eQTLs based pathway association analysis of KBD using Affymetrix Human SNP Array 6.0 in 1717 Chinese Han subjects. PLINK software was used for genome-wide association study (GWAS) of KBD. A modified gene set enrichment algorithm was applied for pathway association analysis based on GWAS results. The KBD-associated pathways were compared with abnormally expressed pathways in KBD articular cartilage, identified by microarray study of KBD. We identified 4 eQTLs pathways, which were not only significantly associated with KBD, but also abnormally expressed in KBD articular cartilage, including REACTOME_INTRINSIC_PATHWAY_FOR_APOPTOSIS (P = 0.008), MAHAJAN _RESPONSE_TO_IL1A_UP (P = 0.010), KEGG_PEROXISOME (P = 0.005) and MARKS_HDAC_TARGETS_UP (P = 0.006). Our results suggest that eQTLs contributed to KBD excessive chondrocyte apoptosis through regulating the expression of apoptosis related pathways. This study provides novel insight into the genetic susceptibility and therapeutic rationale of KBD.     

Interaction of the receptor FGFRL1 with the negative regulator Spred1

FGFRL1 is a member of the fibroblast growth factor receptor family. It plays an essential role during branching morphogenesis of the metanephric kidneys, as mice with a targeted deletion of the Fgfrl1 gene show severe kidney dysplasia. Here we used the yeast two-hybrid system to demonstrate that FGFRL1 binds with its C-terminal, histidine-rich domain to Spred1 and to other proteins of the Sprouty/Spred family. Members of this family are known to act as negative regulators of the Ras/Raf/Erk signaling pathway. Truncation experiments further showed that FGFRL1 interacts with the SPR domain of Spred1, a domain that is shared by all members of the Sprouty/Spred family. The interaction could be verified by coprecipitation of the interaction partners from solution and by codistribution at the cell membrane of COS1 and HEK293 cells. Interestingly, Spred1 increased the retention time of FGFRL1 at the plasma membrane where the receptor might interact with ligands. FGFRL1 and members of the Sprouty/Spred family belong to the FGF synexpression group, which also includes FGF3, FGF8, Sef and Isthmin. It is conceivable that FGFRL1, Sef and some Sprouty/Spred proteins work in concert to control growth factor signaling during branching morphogenesis of the kidneys and other organs.     

Disordered glycometabolism involved in pathogenesis of Kashin–Beck disease,an endemic osteoarthritis in China

Kashin–Beck disease (KBD) is a chronic endemic osteoarthritis in China. Previous studies have suggested a role of metabolic dysfunction in causation of this disease. In this investigation, the metabolomics approach and cell experiments were used to discover the metabolic changes and their effects on KBD chondrocytes. Nuclear magnetic resonance (¹H NMR) spectroscopy was used to examine serum samples from both the KBD patients and normal controls. The pattern recognition multivariate analysis (OSC–PLS) and quantitative analysis (QMTLS iterator) revealed altered glycometabolism in KBD, with increased glucose and decreased lactate and citrate levels. IPA biological analysis showed the centric location of glucose in the metabolic network. Massive glycogen deposits in chondrocytes and increased uptake of glucose by chondrocytes further confirmed disordered glycometabolism in KBD. An in vitro study showed the effects of disordered glycometabolism in chondrocytes. When chondrocytes were treated with high glucose, expression of type II collagen and aggrecan were decreased, while TNF-α expression, the level of cellular reactive oxygen species and cell apoptosis rates all were increased. Therefore, our results demonstrated that disordered glycometabolism in patients with KBD was linked to the damage of chondrocytes. This may provide a new basis for understanding the pathogenesis of KBD.