Meta-analysis of genome-wide association studies confirms a susceptibility locus for knee osteoarthritis on chromosome 7q22

Knowledge, Attitudes, and Practices of Patients with Knee Osteoarthritis Regarding Osteoporosis and Its Prevention: A Cross-Sectional Study in China

Background

Older age and female sex are risk factors for osteoarthritis and osteoporosis (OP). This study evaluated the knowledge, attitudes, and practices of patients with knee osteoarthritis (KOA) in China regarding OP and its prevention. This cross-sectional, questionnaire-based study enrolled patients with KOA at four grade-A tertiary hospitals in Shandong Province between 1st September and 20th November 2022.

Methods

The administered questionnaire contained 55 items across four dimensions (demographic information, knowledge, attitude, and practice). Logistic regression analyses were performed to identify factors associated with an overall questionnaire score ≥70% of the maximum possible score. SPSS 26.0 was used for the analyses; P<0.05 was considered significant.

Results

The analysis included 434 participants (261 females). The median knowledge, attitude, and practice scores were 7 (interquartile range: 5-10) (possible range, 0-17 points), 44 (interquartile range: 42-49) (possible range, 11-55 points), and 43 (interquartile range: 38-47) (possible range, 13-65 points), respectively. Multivariable logistic regression indicated that female sex (odds ratio [OR], 2.421; 95% confidence interval [95% CI] 1.558-3.762; P<0.001), age 56-65 years-old (OR, 4.222; 95% CI, 1.763-10.109; P=0.001 vs ≤55 years-old), age >65 years-old (OR, 4.358; 95% CI, 1.863-10.195; P=0.001 vs ≤55 years-old), middle/high/technical secondary school education (OR, 1.853; 95% CI, 1.002-3.428; P=0.049 vs primary school or below), and having KOA for 4-5 years (OR, 2.682; 95% CI, 1.412-5.094; P=0.003 vs ≤3 years) were independently associated with a high KAP score.

Conclusion

There is room for improvement in the knowledge and practices of patients with osteoarthritis in China regarding OP. The findings of this study may facilitate the design and implementation of education programs to increase awareness about OP prevention among patients with KOA.

The Genetics and Functional Genomics of Osteoarthritis

Osteoarthritis is the most prevalent whole-joint degenerative disorder, and is characterized by the degradation of articular cartilage and the underlying bone structures. Almost 600 million people are affected by osteoarthritis worldwide. No curative treatments are available, and management strategies focus mostly on pain relief. Here, we provide a comprehensive overview of the available human genetic and functional genomics studies for osteoarthritis to date and delineate how these studies have helped shed light on disease etiopathology. We highlight genetic discoveries from genome-wide association studies and provide a detailed overview of molecular-level investigations in osteoarthritis tissues, including methylation-, transcriptomics-, and proteomics-level analyses. We review how functional genomics data from different molecular levels have helped to prioritize effector genes that can be used as drug targets or drug-repurposing opportunities. Finally, we discuss future directions with the potential to drive a step change in osteoarthritis research.

Role of Serum Micro-RNA-122-5p Expression as a Circulatory Biomarker in People Having Both Knee Osteoarthritis and Osteoporosis: A Case-Control Study

Background Although knee osteoarthritis (KOA) and osteoporosis (OP) manifest distinct pathophysiologies, they share numerous similarities. These health conditions are commonly found in older individuals, particularly among women. The objective of this study is to explore the expression of micro-RNA (miRNA) 122-5p (miR-122-5p) in people affected by both KOA and OP. The main aim is to identify diagnostic biomarkers and potential therapeutic targets, which could help develop personalized treatment approaches. Methods As part of the study, a total of 268 serum samples were collected from the participants, who were divided into four groups: KOA, OP, KOA and OP, and controls, with 67 subjects per group. The miRNA species-containing total RNA was isolated from the serum samples using an miRNeasy serum/plasma kit by QIAGEN (Hilden, Germany). The expression of miR-122-5p was examined in each group using real-time quantitative polymerase chain reaction. Results Expression of miR-122-5p in all three groups (KOA, OP, and common group of KOA and OP) was significantly upregulated, and the fold change value was much higher in the group having both diseases. Conclusions These results might contribute to the identification of cases at risk, early diagnosis, and development, and might also contribute to the development of therapeutic targets in subjects having both KOA and OP.

Improved genetic prediction of the risk of knee osteoarthritis using the risk factor-based polygenic score

BACKGROUND

Polygenic risk score (PRS) analysis is used to predict disease risk. Although PRS has been shown to have great potential in improving clinical care, PRS accuracy assessment has been mainly focused on European ancestry. This study aimed to develop an accurate genetic risk score for knee osteoarthritis (OA) using a multi-population PRS and leveraging a multi-trait PRS in the Japanese population.

METHODS

We calculated PRS using PRS-CS-auto, derived from genome-wide association study (GWAS) summary statistics for knee OA in the Japanese population (same ancestry) and multi-population. We further identified risk factor traits for which PRS could predict knee OA and subsequently developed an integrated PRS based on multi-trait analysis of GWAS (MTAG), including genetically correlated risk traits. PRS performance was evaluated in participants of the Nagahama cohort study who underwent radiographic evaluation of the knees (n = 3,279). PRSs were incorporated into knee OA integrated risk models along with clinical risk factors.

RESULTS

A total of 2,852 genotyped individuals were included in the PRS analysis. The PRS based on Japanese knee OA GWAS was not associated with knee OA (p = 0.228). In contrast, PRS based on multi-population knee OA GWAS showed a significant association with knee OA (p = 6.7 × 10-5, odds ratio (OR) per standard deviation = 1.19), whereas PRS based on MTAG of multi-population knee OA, along with risk factor traits such as body mass index GWAS, displayed an even stronger association with knee OA (p = 5.4 × 10-7, OR = 1.24). Incorporating this PRS into traditional risk factors improved the predictive ability of knee OA (area under the curve, 74.4% to 74.7%; p = 0.029).

CONCLUSIONS

This study showed that multi-trait PRS based on MTAG, combined with traditional risk factors, and using large sample size multi-population GWAS, significantly improved predictive accuracy for knee OA in the Japanese population, even when the sample size of GWAS of the same ancestry was small. To the best of our knowledge, this is the first study to show a statistically significant association between the PRS and knee OA in a non-European population.

TRIAL REGISTRATION

No. C278.

Integrin Subunit Alpha M, ITGAM Nonsynonymous SNP Is Associated with Knee Osteoarthritis among Thais: A Case-Control Study

Knee osteoarthritis (OA), which is one of the most common degenerative joint diseases, presents a multifactorial etiology, involving multiple causative factors including genetic and environmental determinants. Four human neutrophil antigen (HNA) systems can be determined using each HNA allele by single-nucleotide polymorphisms (SNPs). However, there are no data on HNA polymorphisms and knee OA in Thailand, so we investigated the association of HNA SNPs and knee OA in the Thai population. In a case-control study, detection of HNA-1, -3, -4, and -5 alleles by polymerase chain reaction with sequence-specific priming (PCR-SSP) was performed in participants with and without symptomatic knee OA. Logistic regression models were used to estimate the odds ratio (OR) and 95% confidence interval (CI) between cases and controls. Among 200 participants, 117 (58.5%) had knee OA; 83 (41.5%) did not and were included as controls in this study. An integrin subunit alpha M (ITGAM) nonsynonymous SNP, rs1143679, was markedly associated with symptomatic knee OA. The ITGAM*01*01 genotype was identified as an important increased risk factor for knee OA (adjusted OR = 5.645, 95% CI = 1.799-17.711, p = 0.003). These findings may contribute to our understanding of the application prospects for therapeutic approaches to knee OA.

Association between single nucleotide variants and severe chronic pain in older adult patients after lower extremity arthroplasty

BACKGROUND

Hip or knee osteoarthritis (OA) is one of the main causes of disability worldwide and occurs mostly in the older adults. Total hip or knee arthroplasty is the most effective method to treat OA. However, severe postsurgical pain leading to a poor prognosis. So, investigating the population genetics and genes related to severe chronic pain in older adult patients after lower extremity arthroplasty is helpful to improve the quality of treatment.

METHODS

We collected blood samples from elderly patients who underwent lower extremity arthroplasty from September 2020 to February 2021 at the Drum Tower Hospital Affiliated to Nanjing University Medical School. The enrolled patients provided measures of pain intensity using the numerical rating scale on the 90th day after surgery. Patients were divided into the case group (Group A) and the control group (Group B) including 10 patients respectively by the numerical rating scale. DNA was isolated from the blood samples of the two groups for whole-exome sequencing.

RESULTS

In total, 661 variants were identified in the 507 gene regions that were significantly different between both groups (P < 0.05), including CASP5, RASGEF1A, CYP4B1, etc. These genes are mainly involved in biological processes, including cell-cell adhesion, ECM-receptor interaction, metabolism, secretion of bioactive substances, ion binding and transport, regulation of DNA methylation, and chromatin assembly.

CONCLUSIONS

The current study shows some variants within genes are significantly associated with severe postsurgical chronic pain in older adult patients after lower extremity arthroplasty, indicating a genetic predisposition for chronic postsurgical pain. The study was registered according to ICMJE guidelines. The trial registration number is ChiCTR2000031655 and registration date is April 6th, 2020.

An SNN retrocopy insertion upstream of GPR22 is associated with dark red coat color in Poodles

Pigment production and distribution is controlled through multiple genes, resulting in a wide range of coat color phenotypes in dogs. Dogs that produce only the pheomelanin pigment vary in intensity from white to deep red. The Poodle breed has a wide range of officially recognized coat colors, including the pheomelanin-based white, cream, apricot, and red coat colors, which are not fully explained by the previously identified genetic variants involved in pigment intensity. Here, a genome-wide association study for pheomelanin intensity was performed in Poodles which identified an association on canine chromosome 18. Whole-genome sequencing data revealed an SNN retrocopy insertion (SNNL1) in apricot and red Poodles within the associated region on chromosome 18. While equal numbers of melanocytes were observed in all Poodle skin hair bulbs, higher melanin content was observed in the darker Poodles. Several genes involved in melanogenesis were also identified as highly overexpressed in red Poodle skin. The most differentially expressed gene however was GPR22, which was highly expressed in red Poodle skin while unexpressed in white Poodle skin (log₂ fold change in expression 6.1, P < 0.001). GPR22 is an orphan G-protein-coupled receptor normally expressed exclusively in the brain and heart. The SNNL1 retrocopy inserted 2.8 kb upstream of GPR22 and is likely disrupting regulation of the gene, resulting in atypical expression in the skin. Thus, we identify the SNNL1 insertion as a candidate variant for the CFA18 pheomelanin intensity locus in red Poodles.

Phenotype-Genotype analysis of caucasian patients with high risk of osteoarthritis

Background: Osteoarthritis (OA) is a common cause of disability and pain around the world. Epidemiologic studies of family history have revealed evidence of genetic influence on OA. Although many efforts have been devoted to exploring genetic biomarkers, the mechanism behind this complex disease remains unclear. The identified genetic risk variants only explain a small proportion of the disease phenotype. Traditional genome-wide association study (GWAS) focuses on radiographic evidence of OA and excludes sex chromosome information in the analysis. However, gender differences in OA are multifactorial, with a higher frequency in women, indicating that the chromosome X plays an essential role in OA pathology. Furthermore, the prevalence of comorbidities among patients with OA is high, indicating multiple diseases share a similar genetic susceptibility to OA. Methods: In this study, we performed GWAS of OA and OA-associated key comorbidities on 3366 OA patient data obtained from the Osteoarthritis Initiative (OAI). We performed Mendelian randomization to identify the possible causal relationship between OA and OA-related clinical features. Results: One significant OA-associated locus rs2305570 was identified through sex-specific genome-wide association. By calculating the LD score, we found OA is positively correlated with heart disease and stroke. A strong genetic correlation was observed between knee OA and inflammatory disease, including eczema, multiple sclerosis, and Crohn's disease. Our study also found that knee alignment is one of the major risk factors in OA development, and we surprisingly found knee pain is not a causative factor of OA, although it was the most common symptom of OA. Conclusion: We investigated several significant positive/negative genetic correlations between OA and common chronic diseases, suggesting substantial genetic overlaps between OA and these traits. The sex-specific association analysis supports the critical role of chromosome X in OA development in females.

Multi-omics molecular biomarkers and database of osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis in the adult population and is a leading cause of disability. OA-related genetic loci may play an important role in clinical diagnosis and disease progression. With the rapid development of diverse technologies and omics methods, many OA-related public data sets have been accumulated. Here, we retrieved a diverse set of omics experimental results from 159 publications, including genome-wide association study, differentially expressed genes and differential methylation regions, and 2405 classified OA-related gene markers. Meanwhile, based on recent single-cell RNA-seq data from different joints, 5459 cell-type gene markers of joints were collected. The information has been integrated into an online database named OAomics and molecular biomarkers (OAOB). The database (http://ibi.zju.edu.cn/oaobdb/) provides a web server for OA marker genes, omics features and so on. To our knowledge, this is the first database of molecular biomarkers for OA.

The Genetic Epidemiology of Joint Shape and the Development of Osteoarthritis

Congruent, low-friction relative movement between the articulating elements of a synovial joint is an essential pre-requisite for sustained, efficient, function. Where disorders of joint formation or maintenance exist, mechanical overloading and osteoarthritis (OA) follow. The heritable component of OA accounts for ~ 50% of susceptible risk. Although almost 100 genetic risk loci for OA have now been identified, and the epidemiological relationship between joint development, joint shape and osteoarthritis is well established, we still have only a limited understanding of the contribution that genetic variation makes to joint shape and how this modulates OA risk. In this article, a brief overview of synovial joint development and its genetic regulation is followed by a review of current knowledge on the genetic epidemiology of established joint shape disorders and common shape variation. A summary of current genetic epidemiology of OA is also given, together with current evidence on the genetic overlap between shape variation and OA. Finally, the established genetic risk loci for both joint shape and osteoarthritis are discussed.

The Decisive Case-Control Study Elaborates the Null Association between ESR1 XbaI and Osteoarthritis in Asians: A Case-Control Study and Meta-Analysis

(1) Background: The prevalence of knee osteoarthritis (OA) in women is significantly higher than in men. The estrogen receptor α (ERα) has been considered to play a key role due to a large gender difference in its expression. ERα is encoded by the gene estrogen receptor 1 (ESR1), which is widely studied to explore the gender difference in knee OA. Several polymorphisms in ESR1 [PvuII (rs2234693) and BtgI (rs2228480)] were confirmed as the risk factors of OA. However, the evidence of the last widely investigated polymorphism, ESR1 Xbal (rs9340799), is still insufficient for concluding its effect on knee OA. (2) Objective: This study proposed a case-control study to investigate the association between ESR1 Xbal and knee OA. Moreover, a meta-analysis and trial sequential analysis (TSA) were conducted to enlarge the sample size for obtaining a conclusive evidence. (3) Methods: In total, 497 knee OA cases and 473 healthy controls were recruited between March 2015 and July 2018. The Kellgren-Lawrence grading system was used to identify the knee OA cases. To improve the evidence level of our study, we conducted a meta-analysis including the related studies published up until December 2018 from PubMed, Embase, and previous meta-analysis. The results are expressed as odds ratios (ORs) with corresponding 95% confidence intervals (CI) for evaluating the effect of this polymorphism on knee OA risk. TSA was used to estimate the sample sizes required in this issue. (4) Results: We found non-significant association between the G allele and knee OA [Crude-OR: 0.97 (95% CI: 0.78-1.20) and adjusted-OR: 0.90 (95% CI: 0.71-1.15) in allele model] in the present case-control study, and the analysis of other genetic models showed a similar trend. After including six published studies and our case-control studies, the current evidence with 3174 Asians showed the conclusively null association between ESR1 XbaI and knee OA [OR: 0.78 (95% CI: 0.59-1.04)] with a high heterogeneity (I²: 78%). The result of Caucasians also concluded the null association [OR: 1.05 (95% CI: 0.56-1.95), I²: 87%]. (5) Conclusions: The association between ESR1 XbaI and knee OA was not similar with other polymorphisms in ESR1, which is not a causal relationship. This study integrated all current evidence to elaborate this conclusion for suggesting no necessity of future studies.

DUS4L Silencing Suppresses Cell Proliferation and Promotes Apoptosis in Human Lung Adenocarcinoma Cell Line A549

Purpose

This study aims to investigate the potential role of DUS4L (dihydrouridine synthase 4 like) in lung adenocarcinoma (LUAD) and explore its associated pathways in human LUAD.

Methods

Firstly, we evaluated the relationships between clinicopathological characteristics and DUS4L expression via analysis of TCGA RNA sequencing data and other publicly available databases. Then, DUS4L was effectively silenced in LUAD cell line A549 using the lentiviral shRNA (short-hairpin RNA) transfection to assess its effects on cell proliferation, cycle and apoptosis in LUAD cells. RNA-seq technology was applied to shDUS4L and shCtrl-transfected cells to generate the corresponding gene expression profiles. Differentially expressed genes (DEGs) were identified using the DESeq2 program package. Also, DEGs were subjected to Gene Ontology (GO) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis to explore the associated molecular signaling pathways and relevant biological functions.

Results

Analysis of TCGA data revealed that DUS4L was highly upregulated in LUAD tissues which was related to clinical T and TNM stages of LUAD. The knockdown of DUS4L effectively inhibited cell proliferation and promoted apoptosis in A549 cells. Furthermore, the DEGs between the shDUS4L and shCtrl A549 cells were mainly enriched in biological processes associated with spliceosome, ribosome, RNA catabolic process, ncRNA (non-coding RNA) processing, and p53 signaling pathway.

Conclusion

Altogether, our results suggest that DUS4L is significantly associated with tumorigenesis and could be utilized as a novel biomarker and therapeutic target for LUAD.

Treatment recommendations for chronic knee osteoarthritis

Primary osteoarthritis (OA) hinders an aging global population as one of the leading causes of years-lost-to-disability (YLD). OA in most patients is considered to be an overuse injury that results in degenerative inflammation of the joints with the associated formation of bony outgrowths. Due to the escalating nature of this chronic pain disease, treatment management for OA can initially begin with a more conservative approach. It can eventually lead to more invasive surgical procedures. At present, the standard of care remains initial conservative management with lifestyle changes, including weight loss with concurrent anti-inflammatory regimens. Injections are frequently used for the escalation of care, but a significant number of patients ultimately resort to total knee arthroplasty. This review will focus specifically on knee OA, providing a brief overview of risk factors and early management and in-depth exploration of the invasive interventions that can offer symptomatic relief and return of function.

Evolutionary Selection and Constraint on Human Knee Chondrocyte Regulation Impacts Osteoarthritis Risk

During human evolution, the knee adapted to the biomechanical demands of bipedalism by altering chondrocyte developmental programs. This adaptive process was likely not without deleterious consequences to health. Today, osteoarthritis occurs in 250 million people, with risk variants enriched in non-coding sequences near chondrocyte genes, loci that likely became optimized during knee evolution. We explore this relationship by epigenetically profiling joint chondrocytes, revealing ancient selection and recent constraint and drift on knee regulatory elements, which also overlap osteoarthritis variants that contribute to disease heritability by tending to modify constrained functional sequence. We propose a model whereby genetic violations to regulatory constraint, tolerated during knee development, lead to adult pathology. In support, we discover a causal enhancer variant (rs6060369) present in billions of people at a risk locus (GDF5-UQCC1), showing how it impacts mouse knee-shape and osteoarthritis. Overall, our methods link an evolutionarily novel aspect of human anatomy to its pathogenesis.

Osteoarthritis year in review 2019: genetics, genomics and epigenetics

Although osteoarthritis (OA) aetiology is complex, genetic, genomic and epigenetic studies published within the last decade have advanced our understanding of the molecular processes underlying this common musculoskeletal disease. The purpose of this narrative review is to highlight the key research articles within the OA genetics, genomics and epigenetics fields that were published between April 2018 and April 2019. The review focuses on the identification of new OA genetic risk loci, genomics techniques that have been used for the first time in human cartilage and new publicly available databases, and datasets that will aid OA functional studies. Fifty-six new OA susceptibility loci were identified by two large scale genome wide association study meta-analyses, increasing the number of genome-wide significant risk loci to 90. OA risk variants are enriched near genes involved in skeletal development and morphology, and show genetic overlap with height, hip shape, bone area and developmental dysplasia of the hip. Several functional studies of OA loci were published, including a genome-wide analysis of genetic variation on cartilage gene expression. A specialised data portal for exploring cross-species skeletal transcriptomic datasets has been developed, and the first use of cartilage single cell RNAseq analysis reported. This year also saw the systematic identification of all microRNAs, long non-coding RNAs and circular RNAs expressed in human OA cartilage. Putative transcriptional regulatory regions have been mapped in human chondrocytes genome-wide, providing a dataset that will facilitate the prioritisation and characterisation of OA genetic and epigenetic loci.

Genetic Susceptibility Loci for Cardiovascular Disease and Their Impact on Atherosclerotic Plaques

Supplemental Digital Content is available in the text.

Background:

Atherosclerosis is a chronic inflammatory disease in part caused by lipid uptake in the vascular wall, but the exact underlying mechanisms leading to acute myocardial infarction and stroke remain poorly understood. Large consortia identified genetic susceptibility loci that associate with large artery ischemic stroke and coronary artery disease. However, deciphering their underlying mechanisms are challenging. Histological studies identified destabilizing characteristics in human atherosclerotic plaques that associate with clinical outcome. To what extent established susceptibility loci for large artery ischemic stroke and coronary artery disease relate to plaque characteristics is thus far unknown but may point to novel mechanisms.

Methods:

We studied the associations of 61 established cardiovascular risk loci with 7 histological plaque characteristics assessed in 1443 carotid plaque specimens from the Athero-Express Biobank Study. We also assessed if the genotyped cardiovascular risk loci impact the tissue-specific gene expression in 2 independent biobanks, Biobank of Karolinska Endarterectomy and Stockholm Atherosclerosis Gene Expression.

Results:

A total of 21 established risk variants (out of 61) nominally associated to a plaque characteristic. One variant (rs12539895, risk allele A) at 7q22 associated to a reduction of intraplaque fat, P=5.09×10⁻⁶ after correction for multiple testing. We further characterized this 7q22 Locus and show tissue-specific effects of rs12539895 on HBP1 expression in plaques and COG5 expression in whole blood and provide data from public resources showing an association with decreased LDL (low-density lipoprotein) and increase HDL (high-density lipoprotein) in the blood.

Conclusions:

Our study supports the view that cardiovascular susceptibility loci may exert their effect by influencing the atherosclerotic plaque characteristics.

Genome-wide association study of knee pain identifies associations with GDF5 and COL27A1 in UK Biobank

Knee pain is one of the most common musculoskeletal complaints that brings people to medical attention. Approximately 50% of individuals over the age of 50 report an experience of knee pain within the past 12 months. We sought to identify the genetic variants associated with knee pain in 171,516 subjects from the UK Biobank cohort and seek supporting evidence in cohorts from 23andMe, the Osteoarthritis Initiative, and the Johnston County Osteoarthritis Project. We identified two loci that reached genome-wide significance in the UK Biobank: rs143384, located in GDF5 (P = 1.32 × 10-12), a gene previously implicated in osteoarthritis; and rs2808772, located near COL27A1 (P = 1.49 × 10-8). These findings were supported in cohorts with self-reported osteoarthritis/radiographic knee osteoarthritis without pain information. In this report on genome-wide association of knee pain, we identified two loci in or near GDF5 and COL27A1 that are associated with knee pain.

Genome Engineering for Osteoarthritis: From Designer Cells to Disease-Modifying Drugs

BACKGROUND

Osteoarthritis (OA) is a highly prevalent degenerative joint disease involving joint cartilage and its surrounding tissues. OA is the leading cause of pain and disability worldwide. At present, there are no disease-modifying OA drugs, and the primary therapies include exercise and nonsteroidal anti-inflammatory drugs until total joint replacement at the end-stage of the disease.

METHODS

In this review, we summarized the current state of knowledge in genetic and epigenetic associations and risk factors for OA and their potential diagnostic and therapeutic applications.

RESULTS

Genome-wide association studies and analysis of epigenetic modifications (such as miRNA expression, DNA methylation and histone modifications) conducted across various populations support the notion that there is a genetic basis for certain subsets of OA pathogenesis.

CONCLUSION

With recent advances in the development of genome editing technologies such as the CRISPR-Cas9 system, these genetic and epigenetic alternations in OA can be used as platforms from which potential biomarkers for the diagnosis, prognosis, drug response, and development of potential personalized therapeutic targets for OA can be approached. Furthermore, genome editing has allowed the development of "designer" cells, whereby the receptors, gene regulatory networks, or transgenes can be modified as a basis for new cell-based therapies.

Meta-analysis of Icelandic and UK data sets identifies missense variants in SMO, IL11, COL11A1 and 13 more new loci associated with osteoarthritis

Osteoarthritis has a highly negative impact on quality of life because of the associated pain and loss of joint function. Here we describe the largest meta-analysis so far of osteoarthritis of the hip and the knee in samples from Iceland and the UK Biobank (including 17,151 hip osteoarthritis patients, 23,877 knee osteoarthritis patients, and more than 562,000 controls). We found 23 independent associations at 22 loci in the additive meta-analyses, of which 16 of the loci were novel: 12 for hip and 4 for knee osteoarthritis. Two associations are between rare or low-frequency missense variants and hip osteoarthritis, affecting the genes SMO (rs143083812, frequency 0.11%, odds ratio (OR) = 2.8, P = 7.9 × 10^-12, p.Arg173Cys) and IL11 (rs4252548, frequency 2.08%, OR = 1.30, P = 2.1 × 10^-11, p.Arg112His). A common missense variant in the COL11A1 gene also associates with hip osteoarthritis (rs3753841, frequency 61%, P = 5.2 × 10^-10, OR = 1.08, p.Pro1284Leu). In addition, using a recessive model, we confirm an association between hip osteoarthritis and a variant of CHADL¹ (rs117018441, P = 1.8 × 10^-25, OR = 5.9). Furthermore, we observe a complex relationship between height and risk of osteoarthritis.

Genome-wide meta-analysis of 158,000 individuals of European ancestry identifies three loci associated with chronic back pain

Back pain is the #1 cause of years lived with disability worldwide, yet surprisingly little is known regarding the biology underlying this symptom. We conducted a genome-wide association study (GWAS) meta-analysis of chronic back pain (CBP). Adults of European ancestry were included from 15 cohorts in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium, and from the UK Biobank interim data release. CBP cases were defined as those reporting back pain present for ≥3-6 months; non-cases were included as comparisons ("controls"). Each cohort conducted genotyping using commercially available arrays followed by imputation. GWAS used logistic regression models with additive genetic effects, adjusting for age, sex, study-specific covariates, and population substructure. The threshold for genome-wide significance in the fixed-effect inverse-variance weighted meta-analysis was p<5×10(-8). Suggestive (p<5×10(-7)) and genome-wide significant (p<5×10(-8)) variants were carried forward for replication or further investigation in the remaining UK Biobank participants not included in the discovery sample. The discovery sample comprised 158,025 individuals, including 29,531 CBP cases. A genome-wide significant association was found for the intronic variant rs12310519 in SOX5 (OR 1.08, p = 7.2×10(-10)). This was subsequently replicated in 283,752 UK Biobank participants not included in the discovery sample, including 50,915 cases (OR 1.06, p = 5.3×10(-11)), and exceeded genome-wide significance in joint meta-analysis (OR 1.07, p = 4.5×10(-19)). We found suggestive associations at three other loci in the discovery sample, two of which exceeded genome-wide significance in joint meta-analysis: an intergenic variant, rs7833174, located between CCDC26 and GSDMC (OR 1.05, p = 4.4×10(-13)), and an intronic variant, rs4384683, in DCC (OR 0.97, p = 2.4×10(-10)). In this first reported meta-analysis of GWAS for CBP, we identified and replicated a genetic locus associated with CBP (SOX5). We also identified 2 other loci that reached genome-wide significance in a 2-stage joint meta-analysis (CCDC26/GSDMC and DCC).

Lin28a overexpression reveals the role of Erk signaling in articular cartilage development

Adult articular cartilage shows limited tissue turnover, and therefore development of the proper structure of articular cartilage is crucial for life-long joint function. However, the mechanism by which the articular cartilage structure is developmentally regulated is poorly understood. In this study, we show evidence that activation of extracellular signal-regulated kinases (Erk1/2) in articular chondrocyte progenitors during developmental stages control articular cartilage thickness. We found that overexpression of Lin28a, an RNA-binding protein that regulates organismal growth and metabolism, in articular chondrocyte progenitor cells upregulated Erk signaling and increased articular cartilage thickness. Overexpression of a constitutively active Kras mimicked Lin28a overexpression, and inhibition of Erk signaling during embryonic stages normalized the cartilage phenotype of both Kras- and Lin28a-overexpressing mice. These results suggest that articular cartilage thickness is mainly determined during the process of embryonic synovial joint development, which is positively regulated by Erk signaling.

What did we learn from 'omics' studies in osteoarthritis

PURPOSE OF REVIEW

'Omics' technologies developed for the massive analysis of the major biologically relevant molecules (genes, proteins, metabolites) have been applied to the study of osteoarthritis (OA) for more than a decade.

RECENT FINDINGS

'Omics' studies have undoubtedly contributed to increase the knowledge on pathogenic processes related with OA and have provided hundreds to thousands of molecules that might have a putative biomarker utility for this disease.

SUMMARY

This review describes the most recent 'omics' studies in OA research, their conclusions, and discuss those remaining challenges. Still many validation studies must be performed in large and well-characterized cohorts for the translation of the findings from 'omics' strategies to clinical applications. The development of tools for the intelligent integration of 'omics' data with clinical and imaging information is also mandatory to take full profit of the work that has been already performed.

Genetic Variants and Anterior Cruciate Ligament Rupture: A Systematic Review

Background

Studies have shown a familial predisposition for anterior cruciate ligament (ACL) rupture and have been followed by genetic-association studies on polymorphisms in candidate genes in recent years. To date, no systematic review with a best-evidence synthesis has evaluated the influence of genetics on this devastating knee injury.

Objective

Our objective was to evaluate the association between genetic variants and ACL rupture.

Methods

We performed an extensive search in Embase, MEDLINE, Web of Science, Scopus, PubMed Publisher, Cochrane Register of Clinical Trials, and Google scholar up to 24 August 2015. Studies were eligible if they met the following inclusion criteria: (1) design was a case–control study, retrospective or prospective follow-up study, or a randomized controlled trial (RCT); (2) the study examined the association between a genetic variant and ACL rupture in both an ACL and a control group. We determined the risk of bias for all included studies.

Results

We included a total of 16 studies (eight at high risk of bias and eight with an unclear risk) that examined 33 different DNA variants. Conflicting evidence was found for the COL1A1 rs1800012 and COL3A1 rs1800255 variants, whereas limited evidence was found for no association of the COL5A1 rs12722 and rs13946 and COL12A1 rs970547 variants (all encoding collagen). Evidence was insufficient to draw conclusions as to whether any other genetic variant identified in this review had any association with ACL rupture.

Conclusions

More research is needed to support a clear association between ACL rupture and genetic variants. Genome-wide studies are recommended for exploring more potential genetic variants. Moreover, large prospective studies are needed to draw robust conclusions.

Association between EN1 rs4144782 and susceptibility of knee osteoarthritis: A case-control study

Osteoarthritis (OA) is a complex disease that affects the whole joint, resulting from the combined influence of biomechanical factors and genetic factors. The heritable component for primary OA accounts for about 60% of variation in population liability to the disease. So far, genome-wide association studies (GWAS) and candidate gene studies have established many OA-related loci. However, these findings account for only a rather small fraction of the genetic component. To further reveal the genetic architecture of OA, we conducted this case-control study to explore the association of locus EN1 rs4144782 and knee OA susceptibility in a Chinese population. EN1 rs4144782 was significantly associated with increased risk of knee OA (OR=1.26; 95% CI: 1.05-1.50, P value=0.012). In dominant model, compared with carriers of GG genotype, those with AG or AA genotype have an 1.44-fold increased risk of OA (OR: 1.44; 95% CI: 1.10-1.88; P value=0.008). Subgroup analyses didn't change the results materially. This should be the first association study of EN1 locus on risk of OA, and our finding suggested that the EN1 rs4144782 might contribute to the susceptibility of knee OA.

Candidate gene investigation of spinal degenerative osteoarthritis in Greek population

BACKGROUND CONTEXT

Few data exist concerning the natural history of degenerative osteoarthritis (OA) of the spine and its associated gene investigation. Degenerative spinal OA demonstrates an international prevalence of 15% in the general population.

PURPOSE

The aim of this Greek case-control study is to examine gene polymorphisms that have been previously shown or hypothesized to be correlated to degenerative OA. Gene polymorphisms, especially for OA, have never been previously studied in the Greek population.

STUDY DESIGN/SETTING

The study was conducted from May 2009 to December 2012. Eligible subjects who agreed to take part in the study were Greek adults from all of Greece, referred for consultation to the Palliative Care and Pain Relief Unit of Aretaieion University Hospital, in Athens, Greece.

PATIENT SAMPLE

A total of 601 matched pairs (cases and controls) participated in the study, 258 patients (188 women and 70 men) with clinically and radiologically confirmed degenerative OA and 243 control subjects (138 women and 105 men).

OUTCOME MEASURES

All patients presented with chronic pain at the spine (cervical, thoracic or lumbar) caused by sympomatic osteophytes or disc narrowing, whereas clinical diagnosis of OA was based on the presence of both joint symptoms and evidence of structural changes seen on plain conventional X-rays.

METHODS

We investigated genetic variation across candidate OA gene GDF5, CDMP1, CDMP2, Asporin, SMAD3, and chromosomal region 7q22, in a sample of 258 patients with clinically and radiologically confirmed degenerative OA, and 243 control subjects from the Greek population. All subjects (patients and controls) were subsequently matched for the epidemiologic, demographic, and clinical risk factors, to prevent selection biases. A tagging single nucleotide polymorphism (SNP) approach was pursued to cover variation across all targeted loci. Single marker tests as well as haplotypic tests of association were performed. There is no conflict of interest, and also, there are no study funding sources.

RESULTS

We found significant association of spine OA with SNPs and haplotypes along the 7q22 chromosomal region and the SMAD3 gene. At 7q22, single marker association tests showed SNPs rs3801954 and rs2023685 to be associated with the disorder (p-value .0312 and .0041, respectively), but only SNP rs2023685 retained a significant p-value (.046) after performing 1,000 permutation tests. At the SMAD3 gene, SNP rs422342 was also found to be statistically associated (p-value .0282) to intervertebral disc degeneration (permutation p-value .042).

CONCLUSIONS

This is the first study to investigate genetic variation in relation to spine OA in the Greek population. Our results indicate that the genetic basis of the disease may differ in the Greek population in relation to populations of Asian origin, although larger sample sizes are required to underpin the full extent of the involvement of analyzed loci.

Genetic Determinants of Radiographic Knee Osteoarthritis in African Americans

OBJECTIVE

The etiology of knee osteoarthritis (OA), the most common form of arthritis, is complex and may differ by race or ethnicity. In recent years, genetic studies have identified many genetic variants associated with OA, but nearly all the studies were conducted in European whites and Asian Americans. Few studies have focused on the genetics of knee OA in African Americans.

METHODS

We performed a genome-wide association study of radiographic knee OA in 1217 African Americans from 2 North American cohort studies: 590 subjects from the Johnston County Osteoarthritis Project and 627 subjects from the Osteoarthritis Initiative. Analyses were conducted in each cohort separately and combined in an inverse variance fixed effects metaanalysis, which were then included in pathway analyses. We additionally tested 12 single-nucleotide polymorphisms robustly associated with OA in European white populations for association in African Americans.

RESULTS

We identified a genome-wide significant variant in LINC01006 (minor allele frequency 12%; p = 4.11 × 10-9) that is less common in European white populations (minor allele frequency < 3%). Five other independent loci reached suggestive significance (p < 1 × 10-6). In pathway analyses, dorsal/ventral neural tube patterning and iron ion transport pathways were significantly associated with knee OA in African Americans (false discovery rate < 0.05). We found no evidence that previously reported OA susceptibility variants in European whites were associated with knee OA in African Americans.

CONCLUSION

These results highlight differences in the genetic architecture of knee OA between African American and European whites. This finding underscores the need to include more diverse populations in OA genetics studies.

Association of ADAM12 gene polymorphisms with knee osteoarthritis susceptibility

Previous studies that evaluated the association between a disintegrin and metalloprotease 12 (ADAM12) gene polymorphisms and knee osteoarthritis (KOA) have given controversial and indefinite results. Therefore, we performed a meta-analysis to confirm this correlation. We searched the PubMed, Embase, and SinoMed databases for all papers published up to April 11, 2017. Overall, five different studies, totaling 2,353 cases and 3,668 controls, were retrieved on the basis of the search criteria for KOA susceptibility related to four polymorphisms (rs3740199, rs1278279, rs1871054, and rs1044122) in the ADAM12 gene. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of this association. Publication bias was assessed using Egger's and Begg's tests. The rs3740199 G/C polymorphism was found to be associated with increased KOA risk in men (e.g., CG versus GG: OR = 1.44, 95% CI = 1.02–2.04, P = 0.040), but not in the overall analysis and in analyses of other subgroups. Significantly increased associations were also found for the rs1871054 polymorphism (e.g., C versus T allele: OR = 1.85, 95% CI = 1.49–2.30, P < 0.001). However, there were no associations for the rs1278279 and rs1044122 polymorphisms. Furthermore, no obvious evidence of publication bias was detected. Our study indicated that the rs1871054 polymorphism of ADAM12 was significantly associated with increased KOA risk.

Association of ADAM 12 polymorphisms with the risk of knee osteoarthritis: meta-analysis of 5048 cases and 6848 controls

Several studies have suggested the association between ADAM 12 polymorphisms and the risk of osteoarthritis (OA), but the results remained controversial. Therefore, we designed a meta-analysis to systematically evaluate the association on this issue. A literature search for eligible studies was conducted in PubMed, Web of Science and Google Scholar databases. The association between ADAM 12 polymorphisms and knee OA risk was calculated by odds ratios (ORs) and 95% confidence intervals (CIs). Study heterogeneity, sensitivity and publication bias analyses were also conducted. Ten articles covering 5048 cases and 6848 controls met our criteria for the final analysis. We found that the rs1871054 was significantly associated with the risk of knee OA (allele model OR 1.72, 95% CI 1.43-2.07, P < 0.001; additive model: OR 2.06, 95% CI 1.19-3.56, P = 0.010; dominant model: OR 2.45, 95% CI 1.85-3.25, P < 0.001; recessive model: OR 1.54, 95% CI 1.13-2.10, P = 0.007). rs1044122 was significantly associated with knee OA susceptibility in recessive model (OR 1.45, 95% CI 1.03-2.04, P = 0.031). For rs3740199 and rs1278279, no significant associations with knee OA were found. In the stratified analysis by gender, significant association was identified with the risk of knee OA for rs3740199 in men in allele model (OR 2.41, 95% CI 1.51-3.84, P < 0.001), dominant model (OR 2.68, 95% CI 1.17-6.14, P = 0.02) and recessive model (OR 3.51, 95% CI 1.68-7.36, P = 0.001), but not for additive model (OR 1.30, 95% CI 0.81-2.08, P = 0.28). This meta-analysis suggests that the ADAM 12 genetic polymorphisms rs1871054 and rs1044122 might be associated with risk of knee OA; rs3740199 might be associated with risk of knee OA in men. Further well-designed and large scale studies are warranted to validate these associations.

Genome-Wide Association Study of Radiographic Knee Osteoarthritis in North American Caucasians

OBJECTIVE

A major barrier to genetic studies of osteoarthritis (OA) is the need to obtain large numbers of individuals with standardized radiographic evaluations for OA. To address this gap, we performed a genome-wide association study (GWAS) of radiographically defined tibiofemoral knee OA in 3,898 cases and 3,168 controls from 4 well-characterized North American cohorts, and we performed replication analysis of previously reported OA loci.

METHODS

We performed meta-analysis using a 2-stage design. Stage 1 (discovery) consisted of a GWAS meta-analysis of radiographic knee OA carried out in the Osteoarthritis Initiative and the Johnston County Osteoarthritis Project. Knee OA was defined as definite osteophytes and possible joint space narrowing or total joint replacement in one or both knees. Stage 2 (validation) was performed in the Multicenter Osteoarthritis Study and the Genetics of Osteoarthritis study. We genotyped lead meta-analysis variants (P ≤ 1 × 10^-4 ) from stage 1 and tested the association between these variants and knee OA. We then combined results from all cohorts in a meta-analysis.

RESULTS

Lead variants from stage 1, representing 49 unique loci, were analyzed in stage 2; none met genome-wide significance in the combined analysis of stage 1 and stage 2. We validated 1 locus (rs4867568 near LSP1P3) with nominal significance (P < 0.05), which was also our top finding in the combined meta-analysis (odds ratio [OR] 0.84 [95% confidence interval (95% CI) 0.79-0.91], P = 3.02 × 10^-6 ). We observed nominally significant associations (P < 0.05) with 3 previously reported OA loci: rs143383 in GDF5 (OR 1.12 [95% CI 1.04-1.21], P = 2.13 × 10^-3 ), rs835487 in CHST11 (OR 0.93 [95% CI 0.85-0.99], P = 0.03), and rs8044769 in FTO (OR 1.10 [95% CI 1.03-1.19], P = 6.13 × 10^-3 ).

CONCLUSION

These findings provide suggestive evidence of a novel knee OA locus and confirm previously reported associations in GDF5, CHST11, and FTO.

Radiographic endophenotyping in hip osteoarthritis improves the precision of genetic association analysis

OBJECTIVE

Osteoarthritis (OA) has a strong genetic component but the success of previous genome-wide association studies (GWAS) has been restricted due to insufficient sample sizes and phenotype heterogeneity. Our aim was to examine the effect of clinically relevant endophenotyping according to site of maximal joint space narrowing (maxJSN) and bone remodelling response on GWAS signal detection in hip OA.

METHODS

A stratified GWAS meta-analysis was conducted in 2118 radiographically defined hip OA cases and 6500 population-based controls. Signals were followed up by analysing differential expression of proximal genes for bone remodelling endophenotypes in 33 pairs of macroscopically intact and OA-affected cartilage.

RESULTS

We report suggestive evidence (p<5×10-6) of association at 6 variants with OA endophenotypes that would have been missed by using presence of hip OA as the disease end point. For example, in the analysis of hip OA cases with superior maxJSN versus cases with non-superior maxJSN we detected association with a variant in the LRCH1 gene (rs754106, p=1.49×10-7, OR (95% CIs) 0.70 (0.61 to 0.80)). In the comparison of hypertrophic with non-hypertrophic OA the most significant variant was located between STT3B and GADL1 (rs6766414, p=3.13×10-6, OR (95% CIs) 1.45 (1.24 to 1.69)). Both of these associations were fully attenuated in non-stratified analyses of all hip OA cases versus population controls (p>0.05). STT3B was significantly upregulated in OA-affected versus intact cartilage, particularly in the analysis of hypertrophic and normotrophic compared with atrophic bone remodelling pattern (p=4.2×10-4).

CONCLUSIONS

Our findings demonstrate that stratification of OA cases into more homogeneous endophenotypes can identify genes of potential functional importance otherwise obscured by disease heterogeneity.

Association study of candidate genes for susceptibility to Kashin-Beck disease in a Tibetan population

Background

Many osteoarthritis (OA) susceptibility genes have been identified in recent years. Given the overlap in the phenotype of joint inflammation between OA and Kashin-Beck disease (KBD), the aim of this study is to explore whether the reported OA susceptibility genes and two genes that may link to OA pathophysiology are associated with KBD in the Tibetan population.

Method

Fifteen single-nucleotide polymorphisms (SNPs) in 12 candidate genes previously reported as OA susceptibility loci were selected for investigation. Genotyping was performed using the SNaPshot method for these SNPs in a Tibetan population composed of 849 KBD patients and 565 normal controls. Meanwhile, the coding regions of two genes, COL10A1 and HABP2, which may involve in the pathological mechanism of OA/KBD, were sequenced by Sanger sequencing to identify susceptibility coding variants for KBD in the Tibetan population.

Results

The two arthritis-susceptible candidate SNPs, rs7775 (p.Arg324Gly) in the FRZB gene and rs7033979 in the ASPN gene, showed associations with KBD (OR = 1.568, P = 4 × 10⁻³ and OR = 0.744, P = 8 × 10⁻³, respectively). The coding variants rs142463796 (p.Asp128Asn) and rs2228547 (p.Gly545Arg) in the COL10A1 gene (OR = 9.832 and P = 6 × 10⁻³ and OR = 1.242, P = 0.043, respectively) and rs548354451 (p.Asp272Glu) in the HABP2 gene (OR = 2.813, P = 0.010) were associated with KBD patients.

Conclusion

These finding suggested that rs7775 in the FRZB gene may increase susceptibility to KBD, while rs7033979 in the ASPN gene may play a protective role in susceptibility to KBD in Tibetans. Moreover, genetic variants in chondrogenesis-related genes COL10A1 and HABP2 may play a role in the risk of developing KBD in the Tibetan population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0423-6) contains supplementary material, which is available to authorized users.

Genetic effects of rs3740199 polymorphism in ADAM12 gene on knee osteoarthritis: a meta-analysis

BACKGROUND

Knee osteoarthritis (OA) is a complex arthritic condition in which genetic factors play an important role. ADAM12 gene is one of the recognized candidate genes although the results are conflicting. To derive a more precise estimation of the association between rs3740199 polymorphism in ADAM12 gene and risk of knee OA, we performed a meta-analysis based on six related studies, including a total of 2185 cases and 3716 controls.

METHODS

A comprehensive search was performed to identify related studies up to April 14, 2017. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. Different genetic models were used to assess the pooled and stratified data.

RESULTS

Overall, no significant association was found in all genetic models (C vs. G, OR = 0.983, 95% CI = 0.910-1.061; CC vs. GG, OR = 1.033, 95% CI = 0.851-1.255; CG vs. GG, OR = 1.030, 95% CI = 0.877-1.209; CC/CG vs. GG, OR = 1.031, 95% CI = 0.886-1.201; CC vs. CG/GG, OR = 1.017, 95% CI = 0.868-1.190). When stratified by ethnicity, no significant association was found.

CONCLUSIONS

This meta-analysis suggested that the rs3740199 polymorphism does not contribute to the development of knee OA. Additional well-designed large studies are required to confirm these findings in different populations.

Candidate methylated genes in osteoarthritis explored by bioinformatics analysis

BACKGROUND

This study aimed to explore potential novel genes correlated with osteoarthritis (OA).

METHODS

The gene expression profile of GSE48422 was downloaded from the Gene Expression Omnibus (GEO) database. This dataset included five arthritic cartilage samples and five non-arthritic cartilage samples from five female OA patients. Differentially methylated genes (DMGs) between the two kinds of samples were identified, followed by their functional analysis and protein-protein interaction (PPI) analysis. Furthermore, the Comparative Toxicogenomics Database (CTD) was used to further identify OA-related genes among these DMGs.

RESULTS

In total, 965 hypermethylated genes and 112 hypomethylated genes were identified in the arthritic cartilage samples. The hypermethylated genes (e.g., ADCY4 and ADCY6) were significantly related to the calcium signaling pathway and gonadotropin-releasing hormone signaling pathway, while the hypomethylated genes were implicated in the mammalian target of rapamycin signaling pathway. In the PPI network, several genes had a higher degree, such as ADCY4, ADCY6 and GPR17, and they interacted with each other. Additionally, 565 DMGs were predicted to be associated with OA, and five of them (e.g., COMP and EDIL3) were previously identified as OA markers.

CONCLUSIONS

The methylation of genes ADCY4, ADCY6 and GPR17, as well as the gonadotropin-releasing hormone signaling pathway, was newly found to be potentially associated with OA. They may be novel OA markers.

Identification of novel genetic variations affecting osteoarthritis patients

Background

Osteoarthritis (OA) is a progressive joint disease characterized by gradual degradation of extracellular matrix (ECM) components in the cartilage and bone. The ECM of cartilage is a highly specified structure that is mainly composed of type II collagen and provides tensile strength to the tissue via aggrecan and proteoglycans. However, changes in the ECM composition and structure can lead to loss of collagen type II and network integrity. Several risk factors have been correlated with OA including age, genetic predisposition, hereditary factors, obesity, mechanical injuries, and joint trauma. Certain genetic association studies have identified several genes associated with OA using genome-wide association studies (GWASs).

Results

We identified several novel genetic variants affecting genes that function in several candidate causative pathways including immune responses, inflammatory and cartilage degradation such as SELP, SPN, and COL6A6.

Conclusions

The approach of whole-exome sequencing can be a promising method to identify genetic mutations that can influence the OA disease.

Novel Genetic Variants for Cartilage Thickness and Hip Osteoarthritis

Osteoarthritis is one of the most frequent and disabling diseases of the elderly. Only few genetic variants have been identified for osteoarthritis, which is partly due to large phenotype heterogeneity. To reduce heterogeneity, we here examined cartilage thickness, one of the structural components of joint health. We conducted a genome-wide association study of minimal joint space width (mJSW), a proxy for cartilage thickness, in a discovery set of 13,013 participants from five different cohorts and replication in 8,227 individuals from seven independent cohorts. We identified five genome-wide significant (GWS, P≤5·0×10-8) SNPs annotated to four distinct loci. In addition, we found two additional loci that were significantly replicated, but results of combined meta-analysis fell just below the genome wide significance threshold. The four novel associated genetic loci were located in/near TGFA (rs2862851), PIK3R1 (rs10471753), SLBP/FGFR3 (rs2236995), and TREH/DDX6 (rs496547), while the other two (DOT1L and SUPT3H/RUNX2) were previously identified. A systematic prioritization for underlying causal genes was performed using diverse lines of evidence. Exome sequencing data (n = 2,050 individuals) indicated that there were no rare exonic variants that could explain the identified associations. In addition, TGFA, FGFR3 and PIK3R1 were differentially expressed in OA cartilage lesions versus non-lesioned cartilage in the same individuals. In conclusion, we identified four novel loci (TGFA, PIK3R1, FGFR3 and TREH) and confirmed two loci known to be associated with cartilage thickness.The identified associations were not caused by rare exonic variants. This is the first report linking TGFA to human OA, which may serve as a new target for future therapies.

Angiotensin-Converting Enzyme Insertion/Deletion Polymorphism and Susceptibility to Osteoarthritis of the Knee: A Case-Control Study and Meta-Analysis

Background

Studies of angiotensin-converting enzyme insertion/deletion (ACE I/D) polymorphisms and the risks of knee osteoarthritis (OA) have yielded conflicting results.

Objective

To determine the association between ACE I/D and knee OA, we conducted a combined case-control study and meta-analysis.

Methods

For the case-control study, 447 knee OA cases and 423 healthy controls were recruited between March 2010 and July 2011. Knee OA cases were defined using the Kellgren-Lawrence grading system, and the ACE I/D genotype was determined using a standard polymerase chain reaction. The association between ACE I/D and knee OA was detected using allele, genotype, dominant, and recessive models. For the meta-analysis, PubMed and Embase databases were systematically searched for prospective observational studies published up until August 2015. Studies of ACE I/D and knee OA with sufficient data were selected. Pooled results were expressed as odds ratios (ORs) with corresponding 95% confidence intervals (CI) for the D versus I allele with regard to knee OA risk.

Results

We found no significant association between the D allele and knee OA [OR: 1.09 (95% CI: 0.76–1.89)] in the present case-control study, and the results of other genetic models were also nonsignificant. Five current studies were included, and there were a total of six study populations after including our case-control study (1165 cases and 1029 controls). In the meta-analysis, the allele model also yielded nonsignificant results [OR: 1.37 (95% CI: 0.95–1.99)] and a high heterogeneity (I²: 87.2%).

Conclusions

The association between ACE I/D and knee OA tended to yield negative results. High heterogeneity suggests a complex, multifactorial mechanism, and an epistasis analysis of ACE I/D and knee OA should therefore be conducted.

Analysis of genetics and DNA methylation in osteoarthritis: What have we learnt about the disease?

Osteoarthritis (OA) is a chronic musculoskeletal disease characterised by the destruction of articular cartilage, synovial inflammation and bone remodelling. Disease aetiology is complex and highly heritable, with genetic variation estimated to contribute to 50% of OA occurrence. Epigenetic alterations, including DNA methylation changes, have also been implicated in OA pathophysiology. This review examines what genetic and DNA methylation studies have taught us about the genes and pathways involved in OA pathology. The influence of DNA methylation on the molecular mechanisms underlying OA genetic risk and the consequence of this interaction on disease susceptibility and penetrance are also discussed.

Single Nucleotide Polymorphisms and Osteoarthritis: An Overview and a Meta-Analysis

Osteoarthritis (OA) is a complex disorder characterized by degenerative articular cartilage and is largely attributed to genetic risk factors. Single nucleotide polymorphisms (SNPs) are common DNA variants that have shown promising and efficiency, compared with positional cloning, to map candidate genes of complex diseases, including OA. In this study, we aim to provide an overview of multiple SNPs from a number of genes that have recently been linked to OA susceptibility. We also performed a comprehensive meta-analysis to evaluate the association of SNP rs7639618 of double von Willebrand factor A domains (DVWA) gene with OA susceptibility. A systematic search of studies on the association of SNPs with susceptibility to OA was conducted in PubMed and Google scholar. Studies subjected to meta-analysis include human and case-control studies that met the Hardy-Weinberg equilibrium model and provide sufficient data to calculate an odds ratio (OR). A total of 9500 OA cases and 9365 controls in 7 case-control studies relating to SNP rs7639618 were included in this study and the ORs with 95% confidence intervals (CIs) were calculated. Over 50 SNPs from different genes have been shown to be associated with either hip (23), or knee (20), or both (13) OA. The ORs of these SNPs for OA and the subtypes are not consistent. As to SNP rs7639618 of DVWA, increased knee OA risk was observed in all genetic models analyzed. Specifically, people from Asian with G-allele showed significantly increased risk of knee OA (A versus G: OR = 1.28, 95% CI 1.13-1.46; AA versus GG: OR = 1.60, 95% CI 1.25-2.05; GA versus GG: OR = 1.31, 95% CI 1.18-1.44; AA versus GA+GG: OR = 1.34, 95% CI 1.12-1.61; AA+GA versus GG: OR = 1.40, 95% CI 1.19-1.64), but not in Caucasians or with hip OA. Our results suggest that multiple SNPs play different roles in the pathogenesis of OA and its subtypes; SNP rs7639618 of DVWA gene is associated with a significantly increased risk of knee OA in Asians. Given the limited sample size, further studies are needed to evaluate this observation.

The Genetic Epidemiological Landscape of Hip and Knee Osteoarthritis: Where Are We Now and Where Are We Going?

Osteoarthritis (OA) is a complex disease that affects the whole joint, with multiple biological and environmental factors contributing to its development. The heritable component for primary OA accounts for ∼50% of susceptibility. So far, candidate gene studies and genome-wide association scans have established 18 OA-associated loci. These findings account for 11% of the heritability, explaining a rather small fraction of the genetic component. To further unravel the genetic architecture of OA, the field needs to facilitate more precise phenotypic definitions, high genome coverage, and large sample metaanalyses, expecting the identification of rare and low frequency variants with potentially higher penetrance, and more accurate methods for calculating phenotype-genotype correlation. Expression analysis, epigenetics, and investigation of interactions can also help clarify the implicated transcriptional regulatory pathways and provide insights into further novel pathogenic OA mechanisms leading to diagnostic biomarker identification and new, more focused therapeutic disease approaches.

Association study of MMP8 gene in osteoarthritis

OBJECTIVES

Osteoarthritis (OA) is a joint disease common in the elderly. There is a prior functional evidence for different matrix metalloproteinases (MMPs), such as MMP8 and MMP9, having a role in the breakdown of cartilage extracellular matrix in OA. Thus, we analyzed whether the common genetic variants of MMP8 and MMP9 contribute to the risk of OA.

MATERIALS AND METHODS

In total, 13 common tagging single-nucleotide polymorphisms (SNPs) were studied in a discovery knee OA cohort of 185 cases and 895 controls. For validation, two knee OA replication cohorts and two hand OA replication cohorts were studied (altogether 1369 OA cases, 4445 controls in the five cohorts). The χ(2) test for individual study cohorts and Cochran-Mantel-Haenszel test for combined meta-analysis were calculated using Plink.

RESULTS

The rs1940475 SNP in MMP8 showed suggestive association in the discovery cohort (OR = 0.721, 95% CI 0.575-0.906; p = 0.005). Other knee and hand OA replication study cohorts showed similar trend for the predisposing allele without reaching statistical significance in independent replication cohorts nor in their meta-analysis (p > 0.05). Meta-analysis of all five hand and knee OA study cohorts yielded a p-value of 0.027 (OR = 0.904, 95% CI 0.826-0.989).

CONCLUSIONS

Initial analysis of the MMP8 gene showed suggestive association between rs1940475 and knee OA, but the finding did not replicate in other study cohorts, even though the trend for predisposing allele was similar in all five cohorts. MMP-8 is a good biological candidate for OA, but our study did not find common variants with significant association in the gene.

Genetic polymorphisms of interleukin-16 and risk of knee osteoarthritis

BACKGROUND

Interleukin-16 (IL-16), a pleiotropic cytokine, plays a fundamental role in inflammatory diseases. This study investigates the association between IL-16 polymorphisms and the risk of knee osteoarthritis (OA) in a Chinese population.

METHODS

The IL-16 rs11556218, rs4072111, and rs4778889 polymorphisms were determined in 150 knee OA cases and 147 healthy controls through polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The results suggested that the variants in IL-16 gene rs11556218 site were associated with a decreased knee OA risk after adjusting for age, sex, BMI, and smoking and drinking status (TG vs. TT: OR, 0.69; 95% CI, 0.53-0.89; P = 0.006; GG vs. TT: OR, 0.64; 95% CI, 0.45-0.90; P = 0.042; dominant model: OR, 0.68; 95% CI, 0.29-0.87; P = 0.002; G vs. T allele: OR, 0.77; 95% CI, 0.66-0.90; P = 0.003). Similarly, subjects bearing the rs4072111 variant genotypes and alleles also had a lower susceptibility to knee OA compared with those bearing the wild-type (CT vs. CC: OR, 0.66; 95% CI, 0.53-0.83; P = 0.002; TT vs. CC: OR, 0.57; 95% CI, 0.40-0.82; P = 0.027; dominant model: OR, 0.65; 95%, CI 0.52-0.80; P <0.001; T vs. C allele: OR, 0.69; 95% CI, 0.58-0.81; P <0.001). Further, the C allele and the combined genotype (CC+CT) of rs4778889 were associated with a slightly decreased risk of knee OA. In addition, we found two high-risk haplotypes: TTT (OR, 3.70) and GCC (OR, 6.22). Finally, serum IL-16 levels of knee OA patients were significantly higher than those of controls (P = 0.001).

CONCLUSIONS

Despite the small sample size, this is the first study suggesting IL-16 gene polymorphisms to be associated with the risk of knee OA.

Applying personal genetic data to injury risk assessment in athletes

Recent studies have identified genetic markers associated with risk for certain sports-related injuries and performance-related conditions, with the hope that these markers could be used by individual athletes to personalize their training and diet regimens. We found that we could greatly expand the knowledge base of sports genetic information by using published data originally found in health and disease studies. For example, the results from large genome-wide association studies for low bone mineral density in elderly women can be re-purposed for low bone mineral density in young endurance athletes. In total, we found 124 single-nucleotide polymorphisms associated with: anterior cruciate ligament tear, Achilles tendon injury, low bone mineral density and stress fracture, osteoarthritis, vitamin/mineral deficiencies, and sickle cell trait. Of these single nucleotide polymorphisms, 91% have not previously been used in sports genetics. We conducted a pilot program on fourteen triathletes using this expanded knowledge base of genetic variants associated with sports injury. These athletes were genotyped and educated about how their individual genetic make-up affected their personal risk profile during an hour-long personal consultation. Overall, participants were favorable of the program, found it informative, and most acted upon their genetic results. This pilot program shows that recent genetic research provides valuable information to help reduce sports injuries and to optimize nutrition. There are many genetic studies for health and disease that can be mined to provide useful information to athletes about their individual risk for relevant injuries.