Association of COL1A2, COL2A1 and COL9A1 and primary osteoarthritis in a founder population

Transcriptomic analysis of human cartilage identified potential therapeutic targets for hip osteoarthritis

Cartilage degradation is the hallmark of osteoarthritis (OA). The purpose of this study was to identify and validate differentially expressed genes (DEGs) in human articular cartilage that could serve as potential therapeutic targets for hip OA. We performed transcriptomic profiling in a discovery cohort (12 OA-free and 72 hip OA-affected cartilage) and identified 179 DEGs between OA-free and OA-affected cartilage after correcting for multiple testing (P < 2.97 × 10-6). Pathway and network analyses found eight hub genes to be associated with hip OA (ASPN, COL1A2, MXRA5, P3H1, PCOLCE, SDC1, SPARC, and TLR2), which were all confirmed using qPCR in a validation cohort (36 OA-free and 62 hip OA-affected cartilage) (P < 6.25 × 10-3). Our data showed that dysregulation of extracellular matrix formation and imbalance in the proportion of collagen chains may contribute to the development of hip OA, and SDC1 could be a promising potential therapeutic target. These findings provided a better understanding of the molecular mechanisms for hip OA and may assist in developing targeted treatment strategies.

Gene Expression Microarray Data Identify Hub Genes Involved in Osteoarthritis

The present study was performed to explore the underlying molecular mechanisms and screen hub genes of osteoarthritis (OA) via bioinformatics analysis. In total, twenty-five OA synovial tissue samples and 25 normal synovial tissue samples were derived from three datasets, namely, GSE55457, GSE55235, and GSE1919, and were used to identify the differentially expressed genes (DEGs) of OA by R language. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DEGs were conducted using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). A Venn diagram was built to show the potential hub genes identified in all three datasets. The STRING database was used for constructing the protein–protein interaction (PPI) networks and submodules of DEGs. We identified 507 upregulated and 620 downregulated genes. Upregulated DEGs were significantly involved in immune response, MHC class II receptor activity, and presented in the extracellular region, while downregulated DEGs were mainly enriched in response to organic substances, extracellular region parts, and cadmium ion binding. Results of KEGG analysis indicated that the upregulated DEGs mainly existed in cell adhesion molecules (CAMs), while downregulated DEGs were significantly involved in the MAPK signaling pathway. A total of eighteen intersection genes were identified across the three datasets. These include Nell-1, ATF3, RhoB, STC1, and VEGFA. In addition, 10 hub genes including CXCL12, CXCL8, CCL20, and CCL4 were found in the PPI network and module construction. Identification of DEGs and hub genes associated with OA may be helpful for revealing the molecular mechanisms of OA and further promotes the development of relevant biomarkers and drug targets.

Impact of the gene-gene interactions related to the HIF-1α signaling pathway with the knee osteoarthritis development

INTRODUCTION/OBJECTIVES

Articular cartilage is the target tissue of osteoarthritis (OA), and because it lacks capillary networks, the microenvironment is hypoxic. Hypoxia inducible factor-1 alpha (HIF-1α) regulates the homeostasis of this tissue. The aim of this study was to investigate whether genetic polymorphisms of the HIF-1α signaling pathway are involved in the development of knee OA.

METHOD

We performed a case-control association study and genotyped 134 knee OA patients and 267 healthy controls. All participants were genotyped in order to evaluate 42 SNPs from 22 genes involved in the HIF-1α signaling pathway using the OpenArray technology. Gene-gene interactions (epistasis) were analyzed using the multifactor dimensionality reduction (MDR) method.

RESULTS

The MDR analysis showed epistasis between AKT2 (rs8100018) and IGF1 (rs2288377), AKT2 (rs8100018) and IGF1 (rs35767), IGF1 (rs35767) and COL2A1 (rs1793953), and between GSK3B (rs6438552) and IGF1 (rs35767) polymorphisms, with information gain values of 21.24%, 8.37%, 9.93%, and 5.73%, respectively. Additionally, our model allowed us to identify high- and low-risk genotypes among COL2A1 rs1793953, GSK3B rs6438552, AKT2 rs8100018, and IGF1 rs35767 polymorphisms.

CONCLUSIONS

Knowing the interactions of these polymorphisms involved in HIF-1α signaling pathway could provide a new diagnostic support tool to identify individuals at high risk of developing knee OA.

Whole-genome sequencing reveals novel genes in ossification of the posterior longitudinal ligament of the thoracic spine in the Chinese population

BACKGROUND

Ossification of the posterior longitudinal ligament (OPLL) of the spine is a complex, multifactorial disease. Although several genes that are linked to cervical OPLL susceptibility have been reported, specific genetic studies regarding thoracic OPLL are lacking. Whole-genome sequencing has been considered as an efficient strategy to search for disease-causing genes.

METHODS

We analysed whole-genome sequences in a cohort of 25 unrelated patients with thoracic OPLL. Bioinformatics analysis and various algorithms were used to predict deleterious variants. Sanger sequencing was used to confirm the variants.

RESULTS

Four deleterious mutations in three genes (c.2716C>T (p.Arg906Cys) in collagen type VI α6 (COL6A6); c.1946G>C (p.Gly649Ala) in collagen type IX α1 (COL9A1); and c.301T>C (p.Ser101Pro) and c.171A>G (p.Ile57Met) in toll-like receptor 1 (TLR1)) were successfully identified. All the variants were confirmed by Sanger sequencing.

CONCLUSION

The novel deleterious mutations of the three genes may contribute to the development of thoracic OPLL.

Exercise-driven metabolic pathways in healthy cartilage

OBJECTIVE

Exercise is vital for maintaining cartilage integrity in healthy joints. Here we examined the exercise-driven transcriptional regulation of genes in healthy rat articular cartilage to dissect the metabolic pathways responsible for the potential benefits of exercise.

METHODS

Transcriptome-wide gene expression in the articular cartilage of healthy Sprague-Dawley female rats exercised daily (low intensity treadmill walking) for 2, 5, or 15 days was compared to that of non-exercised rats, using Affymetrix GeneChip arrays. Database for Annotation, Visualization and Integrated Discovery (DAVID) was used for Gene Ontology (GO)-term enrichment and Functional Annotation analysis of differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genome (KEGG) pathway mapper was used to identify the metabolic pathways regulated by exercise.

RESULTS

Microarray analysis revealed that exercise-induced 644 DEGs in healthy articular cartilage. The DAVID bioinformatics tool demonstrated high prevalence of functional annotation clusters with greater enrichment scores and GO-terms associated with extracellular matrix (ECM) biosynthesis/remodeling and inflammation/immune response. The KEGG database revealed that exercise regulates 147 metabolic pathways representing molecular interaction networks for Metabolism, Genetic Information Processing, Environmental Information Processing, Cellular Processes, Organismal Systems, and Diseases. These pathways collectively supported the complex regulation of the beneficial effects of exercise on the cartilage.

CONCLUSIONS

Overall, the findings highlight that exercise is a robust transcriptional regulator of a wide array of metabolic pathways in healthy cartilage. The major actions of exercise involve ECM biosynthesis/cartilage strengthening and attenuation of inflammatory pathways to provide prophylaxis against onset of arthritic diseases in healthy cartilage.

Association of COL2A1 gene polymorphism with degenerative lumbar scoliosis

Background

Degenerative lumbar scoliosis (DLS) progresses with aging after 50-60 years, and the genetic association of DLS remains largely unclear. In this study, the genetic association between collagen type II alpha 1 (COL2A1) gene and DLS was investigated.

Methods

COL2A1 gene polymorphism was investigated in DLS subjects compared to healthy controls to investigate the possibility of its association with COL2A1 gene. Based on a single nucleotide polymorphism (SNP) database, SNP (rs2276454) in COL2A1 were selected and genotyped using direct sequencing in 51 patients with DLS and 235 healthy controls. The SNP effects were analyzed using three models of codominant, dominant, and recessive. Logistic regression models were calculated for odds ratios (ORs) with 95% confidence intervals (CIs) and corresponding p-values, controlling age and gender as co-variables.

Results

SNP (rs2276454) in COL2A1 was significantly associated with the degenerative lumbar scoliosis in the codominant (OR, 1.90; 95% CI, 1.17 to 3.10; p = 0.008) and dominant models (OR, 3.58; 95% CI, 1.59 to 9.29; p = 0.001).

Conclusions

The results suggest that COL2A1 is associated with the risk of DLS in Korean population.

Direct assessment of articular cartilage and underlying subchondral bone reveals a progressive gene expression change in human osteoarthritic knees

OBJECTIVE

To evaluate the interaction of articular cartilage (AC) and subchondral bone (SB) through analysis of osteoarthritis (OA)-related genes of site-matched tissue.

DESIGN

We developed a novel method for isolating site-matched overlying AC and underlying SB from three and four regions of interest respectively from the human knee tibial plateau (n = 50). For each site, the severity of cartilage changes of OA were assessed histologically, and the severity of bone abnormalities were assessed by microcomputed tomography. An RNA isolation procedure was optimized that yielded high quality RNA from site-matched AC and SB tibial regions. Quantitative polymerase chain reaction (Q-PCR) analysis was performed to evaluate gene expression of 61 OA-associated genes for correlation with cartilage integrity and bone structure parameters.

RESULTS

A total of 27 (44%) genes were coordinately up- or down-regulated in both tissues. The expression levels of 19 genes were statistically significantly correlated with the severity of AC degeneration and changes of SB structure; these included: ADAMTS1, ASPN, BMP6, BMPER, CCL2, CCL8, COL5A1, COL6A3, COL7A1, COL16A1, FRZB, GDF10, MMP3, OGN, OMD, POSTN, PTGES, TNFSF11 and WNT1.

CONCLUSIONS

These results provide a strategy for identifying targets whose modification may have the potential to ameliorate pathological alterations and progression of disease in both AC and SB simultaneously. In addition, this is the first study, to our knowledge, to overcome the major difficulties related to isolation of high quality RNA from site-matched joint tissues. We expect this method to facilitate advances in our understanding of the coordinated molecular responses of the whole joint organ.

Large-scale association study for structural soundness and leg locomotion traits in the pig

BACKGROUND

Identification and culling of replacement gilts with poor skeletal conformation and feet and leg (FL) unsoundness is an approach used to reduce sow culling and mortality rates in breeding stock. Few candidate genes related to soundness traits have been identified in the pig.

METHODS

In this study, 2066 commercial females were scored for 17 traits describing body conformation and FL structure, and were used for association analyses. Genotyping of 121 SNPs derived from 95 genes was implemented using Sequenom's MassARRAY system.

RESULTS

Based on the association results from single trait and principal components using mixed linear model analyses and false discovery rate testing, it was observed that APOE, BMP8, CALCR, COL1A2, COL9A1, DKFZ, FBN1 and VDBP were very highly significantly (P < 0.001) associated with body conformation traits. The genes ALOX5, BMP8, CALCR, OPG, OXTR and WNT16 were very highly significantly (P < 0.001) associated with FL structures, and APOE, CALCR, COL1A2, GNRHR, IHH, MTHFR and WNT16 were highly significantly (P < 0.01) associated with overall leg action. Strong linkage disequilibrium between CALCR and COL1A2 on SSC9 was detected, and haplotype -ACGACC- was highly significantly (P < 0.01) associated with overall leg action and several important FL soundness traits.

CONCLUSION

The present findings provide a comprehensive list of candidate genes for further use in fine mapping and biological functional analyses.