Genetic associations in peripheral joint osteoarthritis and spinal degenerative disease: a systematic review

Evaluation of circulating microRNA signature in patients with erosive hand osteoarthritis: The HOAmiR study

OBJECTIVES

To identify circulating micro-RNAs differentially expressed in patients with erosive hand osteoarthritis (HOA) compared to patients with non-erosive HOA and patients without HOA.

METHODS

In the screening phase, 768 well-characterized micro-RNAs using Taqman low-density array cards were measured in 30 sera from 10 patients with erosive HOA, 10 patients with non-erosive HOA, and 10 controls without HOA, matched for age and body mass index (BMI). In a second step, we validated the micro-RNAs identified at the screening phase (adjusted p value < 0.05 after false discovery rate correction using Benjamini-Hochberg method and literature review) in larger samples (60 patients with erosive HOA and 60 patients without HOA matched for age and BMI).

RESULTS

In the screening phase, we identified 21 down-regulated and 4 up-regulated micro-RNAs of interest between erosive HOA and control groups. Among these, 9 micro-RNAs (miR-373-3p, miR-558, miR-607, miR-653-5p, miR-137 and miR448 were down-regulated, and miR-142-3p, miR-144-3p and miR-34a-5p were up-regulated) were previously described in chondrocytes homeostasis or OA. We found only one significantly down-regulated micro-RNA between erosive and non-erosive HOA. In the validation phase, we showed replication of a single micro-RNA the significant downregulation of miR-196-5p, that had been previously identified in the screening phase among patients with erosive HOA compared to those without HOA. After reviewing the literature and the miRNA-gene interaction prediction model, we found that this microRNA could interact with bone homeostasis and HOXC8, which could explain its role in osteoarthritis.

CONCLUSIONS

We found that miR-196-5p was down-regulated in patients with erosive HOA and some of its targets could explain a role in OA.

Cemented vs. Cementless Fixation in Primary Knee Replacement: A Narrative Review

Knee osteoarthritis (OA) is one of the leading causes of disability around the globe. Osteoarthritis is mainly considered a disease affecting the elderly. However, more and more studies show that sports overuse, obesity, or congenital disorders can initiate a pathologic cascade that leads to OA changes in the younger population. Nevertheless, OA mostly affects the elderly, and with increasing life expectancy, the disease will develop in more and more individuals. To date, the golden standard in the treatment of the end-stage of the disease is total joint replacement (TJR), which restores painless knee motion and function. One of the weakest elements in TJR is its bonding with the bone, which can be achieved by bonding material, such as poly methyl-methacrylate (PMMA), or by cementless fixation supported by bone ingrowth onto the endoprosthesis surface. Each technique has its advantages; however, the most important factor is the revision rate and survivor time. In the past, numerous articles were published regarding TJR revision rate, but no consensus has been established yet. In this review, we focused on a comparison of cemented and cementless total knee replacement surgeries. We introduced PICO rules, including population, intervention, comparison and outcomes of TJR in a PubMed search. We identified 783 articles published between 2010 and 2023, out of which we included 14 in our review. Our review reveals that there is no universally prescribed approach to fixate knee prostheses. The determination of the most suitable method necessitates an individualized decision-making process involving the active participation and informed consent of each patient.

Combining single-cell RNA sequencing and population-based studies reveals hand osteoarthritis-associated chondrocyte subpopulations and pathways

Hand osteoarthritis is a common heterogeneous joint disorder with unclear molecular mechanisms and no disease-modifying drugs. In this study, we performed single-cell RNA sequencing analysis to compare the cellular composition and subpopulation-specific gene expression between cartilage with macroscopically confirmed osteoarthritis (n = 5) and cartilage without osteoarthritis (n = 5) from the interphalangeal joints of five donors. Of 105 142 cells, we identified 13 subpopulations, including a novel subpopulation with inflammation-modulating potential annotated as inflammatory chondrocytes. Fibrocartilage chondrocytes exhibited extensive alteration of gene expression patterns in osteoarthritic cartilage compared with nonosteoarthritic cartilage. Both inflammatory chondrocytes and fibrocartilage chondrocytes showed a trend toward increased numbers in osteoarthritic cartilage. In these two subpopulations from osteoarthritic cartilage, the ferroptosis pathway was enriched, and expression of iron overload-related genes, e.g., FTH1, was elevated. To verify these findings, we conducted a Mendelian randomization study using UK Biobank and a population-based cross-sectional study using data collected from Xiangya Osteoarthritis Study. Genetic predisposition toward higher expression of FTH1 mRNA significantly increased the risk of hand osteoarthritis (odds ratio = 1.07, 95% confidence interval: 1.02-1.11) among participants (n = 332 668) in UK Biobank. High levels of serum ferritin (encoded by FTH1), a biomarker of body iron overload, were significantly associated with a high prevalence of hand osteoarthritis among participants (n = 1 241) of Xiangya Osteoarthritis Study (P-for-trend = 0.037). In conclusion, our findings indicate that inflammatory and fibrocartilage chondrocytes are key subpopulations and that ferroptosis may be a key pathway in hand osteoarthritis, providing new insights into the pathophysiology and potential therapeutic targets of hand osteoarthritis.

Mechanotransduction pathways in articular chondrocytes and the emerging role of estrogen receptor-α

In the synovial joint, mechanical force creates an important signal that influences chondrocyte behavior. The conversion of mechanical signals into biochemical cues relies on different elements in mechanotransduction pathways and culminates in changes in chondrocyte phenotype and extracellular matrix composition/structure. Recently, several mechanosensors, the first responders to mechanical force, have been discovered. However, we still have limited knowledge about the downstream molecules that enact alterations in the gene expression profile during mechanotransduction signaling. Recently, estrogen receptor α (ERα) has been shown to modulate the chondrocyte response to mechanical loading through a ligand-independent mechanism, in line with previous research showing that ERα exerts important mechanotransduction effects on other cell types, such as osteoblasts. In consideration of these recent discoveries, the goal of this review is to position ERα into the mechanotransduction pathways known to date. Specifically, we first summarize our most recent understanding of the mechanotransduction pathways in chondrocytes on the basis of three categories of actors, namely mechanosensors, mechanotransducers, and mechanoimpactors. Then, the specific roles played by ERα in mediating the chondrocyte response to mechanical loading are discussed, and the potential interactions of ERα with other molecules in mechanotransduction pathways are explored. Finally, we propose several future research directions that may advance our understanding of the roles played by ERα in mediating biomechanical cues under physiological and pathological conditions.

Common variants in GNL3 gene contributed the susceptibility of hand osteoarthritis in Han Chinese population

Osteoarthritis (OA) is one of the most popular degenerative joint diseases. The nucleolar GTP binding protein 3 (GNL3) gene encodes guanine nucleotide binding protein-like 3, which is related in cell proliferation, differentiation, and cell cycle regulation. Our study aimed to examine the contribution of GNL3 gene polymorphisms to the risk of hand OA and its related clinical features. A total of 3387 study participants including 1160 patients with hand OA and 2227 controls were recruited in this study. Eleven SNPs in GNL3 gene were selected for genotyping. Genetic association signals were examined using Plink. Relationships between significant SNPs and clinical features of hand OA were also explored. SNP rs11177 was found to be strongly associated with susceptibility of hand OA (P = 4.32 × 10^-5). The minor allele of rs11177 was associated with increased susceptibility of hand OA. In addition, significant associations were also identified between genotypes of rs11177 and clinical features of hand OA patients including K-L grade (P < 0.01) and categorized pain scores (P < 0.01). Significant eQTL signals for rs11177 on GNL3 in multiple types of human tissues were also identified in GTEx database. Our results have established the link between GNL3 gene and susceptibility of hand OA.

Interactions between diabetes mellitus and osteoarthritis; from animal studies to clinical data

Diabetes mellitus (DM) and osteoarthritis (OA) are commonly known metabolic diseases that affect a large segment of the world population. These two conditions share several risk factors such as obesity and aging; however, there is still no consensus regarding the direct role of DM on OA development and progression. Interestingly, both animal and human studies have yielded conflicting results, with some showing a significant role for DM in promoting OA, while others found no significant interactions between these conditions. In this review, we will discuss preclinical and clinical data that assessed the interaction between DM and OA. We will also discuss possible mechanisms associated with the effect of high glucose on the articular cartilage and chondrocytes. An emerging theme dominates the breath of published work in this area: most of the studies discussed in this review do not take into consideration the role of other factors such as the type of diabetes, age, biological sex, type of animal model, body mass index, and the use of pain medications when analyzing and interpreting data. Therefore, future studies should be more rigorous when designing experiments looking at DM and its effects on OA and should carefully account for these confounding factors, so that better approaches can be developed for monitoring and treating patients at risk of OA and DM. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Shared genetic liability between major depressive disorder and osteoarthritis

Aims

Deciphering the genetic relationships between major depressive disorder (MDD) and osteoarthritis (OA) may facilitate an understanding of their biological mechanisms, as well as inform more effective treatment regimens. We aim to investigate the mechanisms underlying relationships between MDD and OA in the context of common genetic variations.

Methods

Linkage disequilibrium score regression was used to test the genetic correlation between MDD and OA. Polygenic analysis was performed to estimate shared genetic variations between the two diseases. Two-sample bidirectional Mendelian randomization analysis was used to investigate causal relationships between MDD and OA. Genomic loci shared between MDD and OA were identified using cross-trait meta-analysis. Fine-mapping of transcriptome-wide associations was used to prioritize putatively causal genes for the two diseases.

Results

MDD has a significant genetic correlation with OA (r_g = 0.29) and the two diseases share a considerable proportion of causal variants. Mendelian randomization analysis indicates that genetic liability to MDD has a causal effect on OA (b_xy = 0.24) and genetic liability to OA conferred a causal effect on MDD (b_xy = 0.20). Cross-trait meta-analyses identified 29 shared genomic loci between MDD and OA. Together with fine-mapping of transcriptome-wide association signals, our results suggest that Estrogen Receptor 1 (ESR1), SRY-Box Transcription Factor 5 (SOX5), and Glutathione Peroxidase 1 (GPX1) may have therapeutic implications for both MDD and OA.

Conclusion

The study reveals substantial shared genetic liability between MDD and OA, which may confer risk for one another. Our findings provide a novel insight into phenotypic relationships between MDD and OA.

Cite this article: Bone Joint Res 2022;11(1):12–22.

Recent Developments in Clinical Applications of Mesenchymal Stem Cells in the Treatment of Rheumatoid Arthritis and Osteoarthritis

Mesenchymal stem cell (MSC) therapies have been used as cell-based treatments for decades, owing to their anti-inflammatory, immunomodulatory, and regenerative properties. With high expectations, many ongoing clinical trials are investigating the safety and efficacy of MSC therapies to treat arthritic diseases. Studies on osteoarthritis (OA) have shown positive clinical outcomes, with improved joint function, pain level, and quality of life. In addition, few clinical MSC trials conducted on rheumatoid arthritis (RA) patients have also displayed some optimistic outlook. The largely positive outcomes in clinical trials without severe side effects establish MSCs as promising tools for arthritis treatment. However, further research is required to investigate its applicability in clinical settings. This review discusses the most recent advances in clinical studies on MSC therapies for OA and RA.

Morbidity, risk of cancer and mortality in 3645 HFE mutations carriers

BACKGROUND & AIMS

Mutations in the HFE gene can lead to hereditary haemochromatosis (HH) and have been suggested to increase the risk of extra-hepatic diseases, especially breast and colorectal cancer. Here we investigated long-term outcomes of Swedish patients with HFE mutations.

METHODS

We identified 3645 patients with a homozygous p.C282Y (62%) or a compound heterozygous p.C282Y/p.H63D (38%) mutation from eight centres in Sweden between 1997 and 2017. These were matched 1:10 by age, sex and county of residence to reference individuals from the general population. We ascertained incident outcomes until the end of 2017 by linkage to national registers. Studied outcomes were HH, cirrhosis, hepatocellular carcinoma (HCC), breast cancer (in women), colorectal cancer, type 1 and 2 diabetes, hypothyroidism, Parkinson's disease and mortality. Cox proportional hazards regression was used to estimate hazard ratios for these outcomes.

RESULTS

Median age at diagnosis was 52 years, 44% were females. During a mean follow-up of 7.9 years, we found an increased risk for HCC, HH, cirrhosis, type 2 diabetes, osteoarthritis and death. Excess mortality was only seen in men. No increased risk was seen for colorectal or breast cancer. Liver-related outcomes were rare, with a cumulative incidence of <1%.

CONCLUSIONS

Individuals found to be HFE mutation carriers in a university hospital setting had an increased risk for mortality in men, along with increased risks of cirrhosis, HCC, diabetes type 2, and osteoarthritis. In general, the absolute risk for adverse outcomes was low and no increased risk for colon or breast cancer was observed.

Hand osteoarthritis: clinical phenotypes, molecular mechanisms and disease management

Osteoarthritis (OA) is a highly prevalent condition, and the hand is the most commonly affected site. Patients with hand OA frequently report symptoms of pain, functional limitations and frustration in undertaking everyday activities. The condition presents clinically with changes to the bone, ligaments, cartilage and synovial tissue, which can be observed using radiography, ultrasonography or MRI. Hand OA is a heterogeneous disorder and is considered to be multifactorial in aetiology. This Review provides an overview of the epidemiology, presentation and burden of hand OA, including an update on hand OA imaging (including the development of novel techniques), disease mechanisms and management. In particular, areas for which new evidence has substantially changed the way we understand, consider and treat hand OA are highlighted. For example, genetic studies, clinical trials and careful prospective imaging studies from the past 5 years are beginning to provide insights into the pathogenesis of hand OA that might uncover new therapeutic targets in the disease.

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.

IL-1 in osteoarthritis: time for a critical review of the literature

The concept of interleukin-1 (IL-1) as a target in osteoarthritis (OA) has been an attractive one for many years. It is a highly potent inducer of cartilage degradation, causing the induction of mRNA and controlling the bioavailability of disease-relevant proteases such as ADAMTS5 and MMP13. It drives synovitis and can induce other disease-relevant genes such as nerve growth factor, a key pain sensitiser in OA. However, the quality of evidence for its involvement in disease is modest. Descriptive studies have demonstrated expression of IL-1α and β in OA cartilage and elevated levels in the synovial fluid of some patients. Agnostic transcriptomic and genomic analyses do not identify IL-1 as a key pathway. In vivo models show a conflicting role for this molecule; early studies using therapeutic approaches in large animal models show a benefit, but most murine studies fail to demonstrate protection where the ligands (IL-1α/β), the cytokine activator (IL-1–converting enzyme), or the receptor (IL-1R) have been knocked out. Recently, a number of large double-blind randomised controlled clinical studies targeting IL-1 have failed. Enthusiasm for IL-1 as a target in OA is rapidly dwindling.

The role of VNTR aggrecan gene polymorphism in the development of osteoarthritis in women

Osteoarthritis (OA) is a common multifactorial joint disease. Undifferentiated connective tissue dysplasia (uCTD) is a genetically determined lesion of the connective tissue structures, including joints, and it can be one of the factors predisposing to development of OA. Solving the problem of comorbidity of OA and uCTD signs will contribute to the early diagnosis and prophylactics of OA. Aggrecan is one of the major structural components of cartilage and it provides the ability to resist compressive loads throughout life. We examined 316 women (mean age 50.5 ± 4.77) for signs of uCTD and OA. A study of the aggrecan gene (ACAN) VNTR polymorphism, which is represented by a variable number of 57 nucleotide repeats, was performed. We searched for associations between the VNTR locus and OA in general and with an account of the localization of the pathological process, as well as with the presence of uCTD signs. Twelve allelic variants and 24 genotypes of the VNTR polymorphism of the aggrecan gene (ACAN) were identified, the most frequent variants were alleles with 27, 28 and 26 repeats. A significance of allele *27 (х2= 6.297, p = 0.012, odds ratio (OR) = 1.50; 95 % confidence interval (CI) 1.09-2.05) in the development of OA in general, knee OA (х2= 4.613, p = 0.031, OR = 1.52; 95 % CI 1.04-2.23), and multiple OA (х2= 4.181, p = 0.04, OR = 1.68; 95 % CI 1.02-2.78) was revealed. Homozygous genotype *27*27 was associated with OA (х2= 3.921, р = 0.047, OR = 1.72; 95 % CI 1-2.96), and OA with uCTD signs in women (х2= 5.415, p = 0.019, OR = 2.34; 95 % CI 1.13-4.83).

Interplay of Inflammatory Mediators with Epigenetics and Cartilage Modifications in Osteoarthritis

Osteoarthritis (OA), a degenerative disease of diarthrodial joints, is influenced by mechanical and inflammatory factors with aging, obesity, chronic injuries, and secondary diseases thought to be major factors driving the process of articular cartilage degeneration. Chondrocytes, the cellular component of cartilage, reside in an avascular environment and normally have limited potential to replicate. However, extrinsic factors such as injury to the joint or intrinsic alterations to the chondrocytes themselves can lead to an altered phenotype and development of OA. Synovial inflammation is also a pivotal element of the osteoarthritic, degenerative process: influx of pro-inflammatory cytokines and production of matrix metalloproteinases accelerate advanced cellular processes such as synovitis and cartilage damage. As well as a genetic input, recent data have highlighted epigenetic factors as contributing to disease. Studies conducted over the last decade have focused on three key aspects in OA; inflammation and the immune response, genome-wide association studies that have identified important genes undergoing epigenetic modifications, and finally how chondrocytes transform in their function during development and disease. Data highlighted here have identified critical inflammatory genes involved in OA and how these factors impact chondrocyte hypertrophy in the disease. This review also addresses key inflammatory factors in synovial inflammation, epigenetics, and chondrocyte fate, and how agents that inhibit epigenetic mechanisms like DNA methylation and histone modifications could aid in development of long-term treatment strategies for the disease.

Novel Genetic Variants Associated with Lumbar Spondylosis in Koreans : A Genome-Wide Association Study

Objective

The aim of this study was to identify the susceptibility genes responsible for lumbar spondylosis (LS) in Korean patients.

Methods

Data from 1427 subjects were made available for radiographic grading and genome wide association studies (GWAS) analysis. Lateral lumbar spine radiographs were obtained and the various degrees of degenerative change were semi-quantitatively scored. A pilot GWAS was performed using the AffymetrixGenome-Wide Human single-nucleotide polymorphisms (SNPs), 500K array. A total of 352228 SNPs were analyzed and the association between the SNPs and case-control status was analyzed by stepwise logistic regression analyses.

Results

The top 100 SNPs with a cutoff p-value of less than 3.7×10^-4 were selected for joint space narrowing, while a cutoff p-value of 6.0×10^-4 was applied to osteophytes and the Kellgren-Lawrence (K-L) osteoarthritis grade. The SNPs with the strongest effect on disc space narrowing, osteophytes, and K-L grade were serine incorporator 1 (rs155467, odds ratio [OR]=17.58, p=1.6×10^-4), stromal interaction molecule 2 (STIM1, rs210781, OR=5.53, p=5×10^-4), and transient receptor potential cation channel, subfamily C (rs11224760, OR=3.99, p=4.8×10^-4), respectively. Leucine-rich repeat-containing G protein-coupled receptor 4 was significantly associated with both disc space narrowing and osteophytes (rs1979400, OR=2.01, p=1.1×10^-4 for disc space narrowing, OR=1.79, p=3×10^-4 for osteophytes), while zinc finger and BTB domain containing 7C was significantly and negatively associated with both osteophytes and a K-L grade >2 (rs12457004,OR=0.25, p=5.8×10^-4 and OR=0.27, p=5.3×10^-4, respectively).

Conclusion

We identified SNPs that potentially contribute to the pathogenesis of LS. This is the first report of a GWAS in an Asian population.

Strong association of the polymorphisms in PBEF1 and knee OA risk: a two-stage population-based study in China

The association of Pre-B cell colony enhancing factor 1 (PBEF1) with obesity, together with its pro-inflammatory properties suggests that PBEF1 might be another crucial mediator that links inflammation with obesity and primary osteoarthritis (OA). We hypothesized that polymorphisms in PBEF1 may modify the risk of developing OA. Thus we systematically screened 4 tagging polymorphisms (rs4730153, rs2058540, rs3801267 and rs16872158) in PBEF1 and evaluated the association between the genetic variants and OA risk in a two-stage case-control study including 196 cases and 442 controls in the first stage and 143 cases and 238 controls in the second stage. In the first stage, two SNPs (rs4730153 and rs16872158) were found to be potentially associated with OA risk (P < 0.05), which were further confirmed in the second stage with similar effects. After combining the two stages, we found that rs4730153 was significantly associated with decreased risk of OA in an additive genetic model (P < 0.05), while rs16872158 showed increased risk of developing OA (P < 0.05). Combined analysis of these 2 SNPs showed a significant allele-dosage association between the number of risk alleles and OA risk (Ptrend = 5.25 × 10(-5)). These findings indicate that genetic variants in PBEF1 gene may modify individual susceptibility to OA in the Chinese population.

Osteoarthritis of the Distal Interphalangeal and First Carpometacarpal Joints is Associated with High Bone Mass in Women and Small Bone Size and Low Lean Mass in Men

Objective:

To determine if primary hand osteoarthritis (OA) is associated with abnormal bone and anthropometric traits.

Methods:

We used DXA to measure total body bone mineral density (BMD), femoral neck width (bone size) and total body lean and fat mass in 39 subjects with hand OA (primary DIP and/or CMC I) and 164 controls. Data are presented as mean Z-scores or Odds Ratios (OR) with 95% confidence intervals.

Results:

Women with hand OA had (compared to controls) higher BMD (0.5(0.1,0.9)) but similar bone size (-0.3(-0.8,0.2)), lean mass (0.3(-0.3,0.9)), fat mass (-0.1(-0.6,0.5)) and BMI (0.0(-0.6,0.6)). Men with hand OA had (compared to controls) similar BMD (-0.1(-0.7,0.6)), smaller bone size (-0.5(-1.1,-0.01)), lower lean mass (-0.6(-1.1,-0.04)), and similar fat mass (-0.2(-0.7,0.4)) and BMI -0.1(-0.6,0.6). In women, each SD higher BMD was associated with an OR of 1.8 (1.03, 3.3) for having hand OA. In men each SD smaller bone size was associated with an OR of 1.8 (1.02, 3.1) and each SD lower proportion of lean body mass with an OR of 1.9 (1.1, 3.3) for having hand OA.

Conclusion:

Women with primary DIP finger joint and/or CMC I joint OA have a phenotype with higher BMD while men with the disease have a smaller bone size and lower lean body mass.

Osteoarthritis in the XXIst century: risk factors and behaviours that influence disease onset and progression

Osteoarthritis (OA) is a growing public health problem across the globe, affecting more than half of the over 65 population. In the past, OA was considered a wear and tear disease, leading to the loss of articular cartilage and joint disability. Nowadays, thanks to advancements in molecular biology, OA is believed to be a very complex multifactorial disease. OA is a degenerative disease characterized by “low-grade inflammation” in cartilage and synovium, resulting in the loss of joint structure and progressive deterioration of cartilage. Although the disease can be dependent on genetic and epigenetic factors, sex, ethnicity, and age (cellular senescence, apoptosis and lubricin), it is also associated with obesity and overweight, dietary factors, sedentary lifestyle and sport injuries. The aim of this review is to highlight how certain behaviors, habits and lifestyles may be involved in the onset and progression of OA and to summarize the principal risk factors involved in the development of this complicated joint disorder.

Association of PPARγ gene polymorphisms with osteoarthritis in a southeast Chinese population

Primary osteoarthritis (OA) is a leading cause of disability in developed countries. Currently no satisfactory treatment to stop disease progression exists. Recent studies suggest that activation of the transcription factor peroxisome proliferator-activated receptor gamma (PPARγ) is an interesting therapeutic target for this disease. PPARγ is a transcription factor important for adipogenesis and adipocyte differentiation. Agonists of PPARγ inhibit inflammation and reduce generation of cartilage degradation products both in vitro and in vivo, and reduce the development/progression of cartilage lesions in OA animal models. However, there are no studies to assess the role of PPARγ in OA susceptibility of human peripheral joints in a Chinese population. We conducted a case-control study in a southeast Chinese population to determine the association of PPARγ gene polymorphisms (rs1801282, rs12629751, rs2292101, rs4135275 and rs1175543) with OA. One-hundred knee OA cases and 100 controls were studied. Statistically significant differences were detected in genotype and allele frequencies between OA and control groups in this population. For knee OA, the highest risk was associated with the variant allele T of the single nucleotide polymorphism rs12629751 (odds ratio (OR): 0.341, 95% confidence interval (CI):0.173-0.673, P = 0.002), and allele T of SNP rs12629751 (chi-square: 9.546, P = 0.002) could be considered as a risk factor of knee OA. Therefore, PPARγ mutation could be associated with the incidence of OA in a Chinese population. There is a significant association between the PPARγ polymorphism rs12629751 and susceptibility to knee OA in a southeast Chinese population.

Variations in the TNFα gene and their interactions with the IL4R and IL10 genes in relation to hand osteoarthritis

Background

The development of osteoarthritis (OA) involves inflammation, but the evidence for participation of genes propagating or inhibiting inflammation in the OA process is inconsistent. We investigated the associations of common variants in the TNFα gene, and their interactions with other cytokine genes, with hand OA among Finnish women.

Methods

This cross-sectional study was based on bilateral hand radiographs of 542 female dentists and teachers which were classified according to the presence of OA (radiographic K-L score ≥ 2 in ≥ 3 joints) using reference images. The genotypes were determined by PCR-based methods. The degree of pairwise linkage disequilibrium (LD) and haplotypes were constructed and analyzed by the SNPStats software. The associations between four TNFα SNPs and hand OA were tested using logistic regression adjusting for age, occupation, and BMI, and fitting a log-additive model of inheritance. Gene-gene interactions of TNFα SNPs with IL4R and IL10 SNPs were examined by stratified logistic regression analyses. Possible interactions of the TNFα SNPs with variants in the previously reported IL1β and IL6 genes in influencing hand OA were also explored.

Results

Two TNFα polymorphisms (“-1031” and “-863”) were associated with hand OA (OR = 1.45, 95% CI 1.01-2.07 and 1.55, 1.06-2.25, respectively). These associations retained when adjusting further for IL1β “3954” and IL6 “174”. The TNFα G-A-G haplotype was associated with an increased risk of hand OA (1.61, 1.10-2.37, p = 0.01). Interactions were observed between TNFα “-1031” and IL4R Ser503Pro, TNFα “-1031” and IL10 “-1082”, and TNFα “-863” and IL10 “-1082” SNPs with regard to hand OA (p = 0.012, p = 0.0068, and p = 0.02, respectively). The carriage of the TNFα “-1031” minor allele doubled the risk (2.01, 1.26 - 3.22) only in women with the IL4R Ser/Ser genotype. Similarly, the TNFα “-1031” and “-863” minor alleles were associated with an increased risk of hand OA only in IL10 G/G or A/A homozygotes (2.54, 1.45-4.47 and 2.60, 1.46-4.62, respectively) but not in heterozygotes (G/A).

Conclusions

Our results suggest that the TNF α gene variants play a role in the etiology of hand OA. In addition, the findings are suggestive of a gene-gene interaction of the TNF α with IL4R and IL10 genes.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-311) contains supplementary material, which is available to authorized users.

A systems view of risk factors for knee osteoarthritis reveals insights into the pathogenesis of the disease

Early detection of osteoarthritis (OA) remains a critical yet unsolved multifaceted problem. To address the multifaceted nature of OA a systems model was developed to consolidate a number of observations on the biological, mechanical and structural components of OA and identify features common to the primary risk factors for OA (aging, obesity and joint trauma) that are present prior to the development of clinical OA. This analysis supports a unified view of the pathogenesis of OA such that the risk for developing OA emerges when one of the components of the disease (e.g., mechanical) becomes abnormal, and it is the interaction with the other components (e.g., biological and/or structural) that influences the ultimate convergence to cartilage breakdown and progression to clinical OA. The model, applied in a stimulus-response format, demonstrated that a mechanical stimulus at baseline can enhance the sensitivity of a biomarker to predict cartilage thinning in a 5 year follow-up in patients with knee OA. The systems approach provides new insight into the pathogenesis of the disease and offers the basis for developing multidisciplinary studies to address early detection and treatment at a stage in the disease where disease modification has the greatest potential for a successful outcome.

Meta-analysis of the association between COL9A2 genetic polymorphisms and lumbar disc disease susceptibility

STUDY DESIGN

Meta-analysis to collect all the relevant studies to date to further investigate whether or not the COL9A2 gene rs12077871, rs12722877, and rs7533552 polymorphism are associated with susceptibility to lumbar disc disease (LDD).

OBJECTIVE

The aim of this study was to assess the association between the COL9A2 gene rs12077871, rs12722877, and rs7533552 and LDD.

SUMMARY OF BACKGROUND DATA

LDD is a common musculoskeletal disease with strong genetic determinants. COL9A2 encodes the α2 (IX) chain of type IX collagen, which is the major collagen component of the hyaline cartilage. Growing numbers of studies have revealed the association between COL9A2 polymorphisms and susceptibility to LDD. However, those studies have yielded contradictory results.

METHODS

Data were collected from the following electronic databases: PubMed, Web of Knowledge, and China National Knowledge Infrastructure, with the last report up to November 30, 2013. The odds ratio (OR) and 95% confidence interval (CI) were used to assess the strength of association under the allelic genetic model. We summarized the data on the association between COL9A2 rs12077871, rs12722877, and rs7533552 polymorphism and LDD in the overall studies.

RESULTS

Nine case-control studies, including 1522 LDD cases and 1646 controls, were identified. The results indicated that the rs12077871, rs12722877, and rs7533552 variants in COL9A2 were not associated with LDD (rs12077871: C vs. T, OR = 0.541, 95% CI = 0.256-1.147, P = 0.109; rs12722877: C vs. G, OR = 1.199, 95% CI = 0.992-1.448, P = 0.06; rs7533552: A vs. G, OR = 0.993, 95% CI = 0.815-1.069, P = 0.320). Furthermore, the Egger test and the Begg funnel plot did not show any evidence of publication bias.

CONCLUSION

Our results suggest that the COL9A2 rs12077871, rs12722877, and rs7533552 polymorphisms may not be associated with LDD. More studies based on larger sample sizes and homogeneous samples of patients with LDD are needed to confirm these findings.

LEVEL OF EVIDENCE

2.

Vertebral endplate change as a feature of intervertebral disc degeneration: a heritability study

PURPOSE

To study the prevalence of vertebral endplate or Modic change (MC), the progression of MC over a 10-year follow-up and the heritability of MC prevalence in a classical twin study.

METHODS

The study population was recruited from TwinsUK register between 1996 and 2000. MC was evaluated from T2-weighted lumbar magnetic resonance imaging (MRI) at baseline and follow-up. Heritability was estimated using variance components analysis. Baseline MRI with appropriate data was available for 831 twins and follow-up for 436 twins. In total, both baseline and follow-up imaging were available for 347 twins.

RESULTS

Mean age of the study population was 54.1 years (range 45.7-62.5) and females comprised 96%. The prevalence of MC at baseline was 32.1% and at follow-up 48.4%. The incidence of MC during the 10-year follow-up was 21.6% and was highest at L4-5 and L5-S1. MC regressed totally in 3.5% of twins. Twins with prevalent MC at baseline demonstrated a higher incidence of MC at upper lumbar levels during follow-up compared to twins without baseline MC (p = 0.009). Probandwise concordance rates were higher in monozygotic (0.56) than dizygotic twin pairs (0.39) suggestive of familial influence. Heritability of MC prevalence was estimated at 30 (16-43) %.

CONCLUSIONS

The results suggest that MC is generally progressive in middle age and furthermore is heritable. Since MC is associated with disc degeneration, which is also heritable, further work on potential shared mechanisms is needed.

Genetic influences on hand osteoarthritis in Finnish women--a replication study of candidate genes

Objectives

Our aims were to replicate some previously reported associations of single nucleotide polymorphisms (SNPs) in five genes (A2BP1, COG5, GDF5, HFE, ESR1) with hand osteoarthritis (OA), and to examine whether genes (BCAP29, DIO2, DUS4L, DVWA, HLA, PTGS2, PARD3B, TGFB1 and TRIB1) associated with OA at other joint sites were associated with hand OA among Finnish women.

Design

We examined the bilateral hand radiographs of 542 occupationally active Finnish female dentists and teachers aged 45 to 63 and classified them according to the presence of OA by using reference images. Data regarding finger joint pain and other risk factors were collected using a questionnaire. We defined two hand OA phenotypes: radiographic OA in at least three joints (ROA) and symptomatic DIP OA. The genotypes were determined by PCR-based methods. In statistical analysis, we used SNPStats software, the chi-square test and logistic regression.

Results

Of the SNPs, rs716508 in A2BP1 was associated with ROA (OR = 0.7, 95% CI 0.5–0.9) and rs1800470 in TGFB1 with symptomatic DIP OA (1.8, 1.2–2.9). We found an interaction between ESR1 (rs9340799) and occupation: teachers with the minor allele were at an increased risk of symptomatic DIP OA (2.8, 1.3–6.5). We saw no association among the dentists. We also found that the carriage of the COG5 rs3757713 C allele increased the risk of ROA only among women with the BCAP29 rs10953541 CC genotype (2.6; 1.1–6.1). There was also a suggestive interaction between the HFE rs179945 and the ESR1 rs9340799, and the carriage of the minor allele of either of these SNPs was associated with an increased risk of symptomatic DIP OA (2.1, 1.3–2.5).

Conclusions

Our results support the earlier findings of A2BP1 and TBGF1 being OA susceptibility genes and provide evidence of a possible gene-gene interaction in the genetic influence on hand OA predisposition.

Association of single nucleotide polymorphisms in estrogen receptor alpha gene with susceptibility to knee osteoarthritis: a case-control study in a Chinese Han population

Osteoarthritis (OA) is the most prevalent form of arthritis and its multifactorial nature has been increasingly recognized. Genetic factors play an important role in OA etiology and estrogen receptor alpha (ESR1) gene polymorphisms may be involved. This study tried to explore whether the ESR1 gene single nucleotide polymorphisms (SNPs) were associated with primary knee OA in the Chinese Han population. Two SNPs, rs2234693 and rs9340799, were genotyped in 469 cases and 522 controls. Rs2234693 was associated with knee OA in the dominant genetic model (TT + TC versus CC) (P = 0.025) and a higher T allele frequency existed (P = 0.047) among females. The combined genotype (TT + TC) (P = 0.025) and T allele (P = 0.016) were related with mild knee OA only. For rs9340799, A allele was associated with knee OA in all subjects (P = 0.031) and females (P = 0.046). Statistical differences were detected in the dominant genetic model (AA + AG versus GG) among females (P = 0.030). The combined genotype (AA + AG) (P = 0.036) and A allele (P = 0.039) were merely correlated with mild knee OA. ESR1 gene is considerably associated with knee OA etiology in the Chinese Han population.

Age-dependent ferritin elevations and HFE C282Y mutation as risk factors for symptomatic knee osteoarthritis in males: a longitudinal cohort study

Background

Age, gender and genetic predisposition are major intrinsic risk factors for osteoarthritis (OA). Iron increases are associated with age and gene mutation. In the present study, we examined whether serum ferritin, an indicator of total body iron stores, correlates with clinical features in patients with OA, and whether the hemochromatosis Fe (HFE) gene mutation plays a role.

Methods

In a 2-year longitudinal observational study, 127 patients with knee OA and 20 healthy individuals (controls) were enrolled. All patients underwent standardized weight-bearing fixed-flexion posteroanterior knee radiographs. Peripheral blood samples were analyzed for serum ferritin, and genotyped for HFE using allelic discrimination methods.

Results

Higher levels of serum ferritin were found in patients older than 56 years (P =0.0186) and males (P =0.0006), with a trend toward higher ferritin in patients with OA. HFE gene mutation carriers were more prevalent among patients with OA than among healthy controls. When stratified further by gender, we found that male patients with OA had higher levels of serum ferritin than male control subjects [odds ratio = 4.18 (limits of 95% confidence interval: 0.86–27.69, P = 0.048)]. Analyses of radiographic data indicated that higher ferritin was associated with narrower joint space width at baseline (P = 0.032) in male patients. Additionally, among men, risk prediction of radiographic severity [Kellgren-Lawrence (KL) grade >2)] in the higher ferritin group was almost five times that of the lower ferritin group (odds ratio = 4.74, P = 0.023).

Conclusion

Our data suggest that increased ferritin levels are associated with symptomatic knee OA in males. This finding needs to be validated in a larger cohort of patients.

Relationship between vitamin D receptor gene (VDR) polymorphisms, vitamin D status, osteoarthritis and intervertebral disc degeneration

The vitamin D endocrine system is involved in bony and cartilaginous metabolisms and alterations in the homeostasis of this system could be associated to pathological conditions of cartilaginous tissue. In this context, the presence of polymorphisms in the vitamin D receptor gene (VDR), in association with the susceptibility to common osteochondral diseases, was largely investigated. The aim of this review was to summarize data present in literature, analyzing the association of the VDR polymorphisms, vitamin D status and knee cartilage and intervertebral disc pathologies, trying to suggest links between the different specific pathologies analyzed. Concerning the association between VDR polymorphisms and cartilaginous tissue diseases, we found controversial reports. However, the great majority of papers reported an association with lumbar disc degeneration, whereas about half of the studies found an association with osteoarthritis. A further association between VDR polymorphisms (in linkage disequilibrium) and the presence of specific characteristics of these diseases, in particular the formation of osteophytes, was evidenced. Finally, the influence of vitamin D status on these pathologies was evaluated, trying to evidence the relation between the presence of particular genetic variants in the VDR and vitamin D levels or to show whether a particular vitamin D status could predispose to the development or progression of such diseases, however, no significant associations were found. In the future, given the role of vitamin D system in the cartilaginous tissue metabolism, it could be interesting to perform functional and tissue specific studies to analyze the interplay between the different VDR variants and its ligand.

Gene-environment interaction between body mass index and transforming growth factor beta 1 (TGFβ1) gene in knee and hip osteoarthritis

Introduction

The objective was to investigate potential gene-environment interaction between body mass index (BMI) and each of eight TGFβ1 polymorphisms in knee and hip osteoarthritis (OA).

Methods

We conducted a case-control study of Caucasian men and women aged 45 to 86 years from Nottingham, United Kingdom (Genetics of OA and Lifestyle (GOAL) study). Cases had clinically severe symptoms and radiographic knee or hip OA; controls had no symptoms and no radiographic knee/hip OA. We used logistic regression to investigate the association of TGFβ1 polymorphisms and OA when stratifying by BMI. Knee and hip OA were analyzed separately with adjustment for potential confounders. Additive and multiplicative interactions were examined.

Results

2,048 cases (1,042 knee OA, 1,006 hip OA) and 967 controls were studied. For hip OA, the highest risk was in overweight (BMI ≥25 kg/m²) individuals with the variant allele of single-nucleotide polymorphism (SNP) rs1800468 (odds ratio (OR) 2.21, 95% confidence interval (CI) 1.55, 3.15). Evaluation of gene-environment interaction indicated significant synergetic interaction (relative excess risk due to interaction (RERI) = 0.93, synergy index (SI) = 4.33) with an attributable proportion due to interaction (AP) of 42% (AP = 0.42; 95% CI 0.16, 0.68). Multiplicative interaction was also significant (OR for interaction (ORINT) = 2.27, P = 0.015). For knee OA, the highest risk was in overweight individuals with homozygous genotype 11 of SNP rs2278422 (OR = 6.95, P <0.001). In contrast, the variant allele indicated slightly lower risks (OR = 4.72, P <0.001), a significant antagonistic interaction (RERI = -2.66, SI = 0.59), AP = -0.56 (95%CI -0.94, -0.17) and a significant multiplicative interaction (ORINT = 0.47, P = 0.013).

Conclusion

TGFβ1 gene polymorphisms interact with being overweight to influence the risk of large joint OA.

Differentiation, diagnosis, and treatment of osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis

Osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis are hip arthropathies that result in marked pain and disability. Although these diseases share features of arthritis-like symptoms and are all treated with total hip arthroplasty, they are separate diseases with distinct epidemiologic, radiographic, and histopathologic findings. In this article, the authors present clinical tips and techniques that will aid the surgeon in diagnosing and treating these different entities.

GDF5 single-nucleotide polymorphism rs143383 is associated with lumbar disc degeneration in Northern European women

Objective

Lumbar disc degeneration (LDD) is a serious social and medical problem which has been shown to be highly heritable. It has similarities with peripheral joint osteoarthritis (OA) in terms of both epidemiology and pathologic processes. A few known genetic variants have been identified using a candidate gene approach, but many more are thought to exist. GDF5 is a gene whose variants have been shown to play a role in skeletal height as well as predisposing to peripheral joint OA. In vitro, the gene product growth differentiation factor 5 has been shown to promote growth and repair of animal disc. This study was undertaken to investigate whether the GDF5 gene plays a role in LDD.

Methods

We investigated whether the 5′ upstream single-nucleotide polymorphism (SNP) variant rs143383 was associated with LDD, using plain radiography and magnetic resonance imaging to identify disc space narrowing and osteophytes, in 5 population cohorts from Northern Europe.

Results

An association between LDD and the SNP rs143383 was identified in women, with the same risk allele as in knee and hip OA (odds ratio 1.72 [95% confidence interval 1.15–2.57], P = 0.008).

Conclusion

Our findings in 5 population cohorts from Northern Europe indicate that a variant in the GDF5 gene is a risk factor for LDD in women. Many more such variants are predicted to exist, but this result highlights the growth and differentiation cellular pathway as a possible route to a better understanding of the process behind lumbar disc degeneration.

Genetic association studies in lumbar disc degeneration: a systematic review

Objective

Low back pain is associated with lumbar disc degeneration, which is mainly due to genetic predisposition. The objective of this study was to perform a systematic review to evaluate genetic association studies in lumbar disc degeneration as defined on magnetic resonance imaging (MRI) in humans.

Methods

A systematic literature search was conducted in MEDLINE, MEDLINE In-Process, SCOPUS, ISI Web of Science, The Genetic Association Database and The Human Genome Epidemiology Network for information published between 1990–2011 addressing genes and lumbar disc degeneration. Two investigators independently identified studies to determine inclusion, after which they performed data extraction and analysis. The level of cumulative genetic association evidence was analyzed according to The HuGENet Working Group guidelines.

Results

Fifty-two studies were included for review. Forty-eight studies reported at least one positive association between a genetic marker and lumbar disc degeneration. The phenotype definition of lumbar disc degeneration was highly variable between the studies and replications were inconsistent. Most of the associations presented with a weak level of evidence. The level of evidence was moderate for ASPN (D-repeat), COL11A1 (rs1676486), GDF5 (rs143383), SKT (rs16924573), THBS2 (rs9406328) and MMP9 (rs17576).

Conclusions

Based on this first extensive systematic review on the topic, the credibility of reported genetic associations is mostly weak. Clear definition of lumbar disc degeneration phenotypes and large population-based cohorts are needed. An international consortium is needed to standardize genetic association studies in relation to disc degeneration.

From expression pattern to genetic association in asthma and asthma-related phenotypes

BACKGROUND

Asthma is a complex disease characterized by hyperresponsiveness, obstruction and inflammation of the airways. To date, several studies using different approaches as candidate genes approach, genome wide association studies, linkage analysis and genomic expression leaded to the identification of over 300 genes involved in asthma pathophysiology. Combining results from two studies of genomic expression, this study aims to perform an association analysis between genes differently expressed in bronchial biopsies of asthmatics compared to controls and asthma-related phenotypes using the same French-Canadian Caucasian population.

RESULTS

Before correction, 31 of the 85 genes selected were associated with at least one asthma-related phenotype. We found four genes that survived the correction for multiple testing. The rs11630178 in aggrecan gene (AGC1) is associated with atopy (p=0.0003) and atopic asthma (p=0.0001), the rs1247653 in the interferon alpha-inducible protein 6 (IFI6), the rs1119529 in adrenergic, alpha-2A-, receptor (ADRA2A) and the rs13103321 in the alcohol dehydrogenase 1B (class I), beta polypeptide (ADH1B), are associated with asthma (p=0.019; 0.01 and 0.002 respectively).

CONCLUSION

To our knowledge, this is the first time those genes are associated with asthma and related traits. Consequently, our study confirms that genetic and expression studies are complementary to identify new candidate genes and to investigate their role to improve the comprehension of the complexity of asthma pathophysiology.

Novel genetic variants associated with lumbar disc degeneration in northern Europeans: a meta-analysis of 4600 subjects

OBJECTIVE

Lumbar disc degeneration (LDD) is an important cause of low back pain, which is a common and costly problem. LDD is characterised by disc space narrowing and osteophyte growth at the circumference of the disc. To date, the agnostic search of the genome by genome-wide association (GWA) to identify common variants associated with LDD has not been fruitful. This study is the first GWA meta-analysis of LDD.

METHODS

We have developed a continuous trait based on disc space narrowing and osteophytes growth which is measurable on all forms of imaging (plain radiograph, CT scan and MRI) and performed a meta-analysis of five cohorts of Northern European extraction each having GWA data imputed to HapMap V.2.

RESULTS

This study of 4600 individuals identified four single nucleotide polymorphisms with p<5×10(-8), the threshold set for genome-wide significance. We identified a variant in the PARK2 gene (p=2.8×10(-8)) associated with LDD. Differential methylation at one CpG island of the PARK2 promoter was observed in a small subset of subjects (β=8.74×10(-4), p=0.006).

CONCLUSIONS

LDD accounts for a considerable proportion of low back pain and the pathogenesis of LDD is poorly understood. This work provides evidence of association of the PARK2 gene and suggests that methylation of the PARK2 promoter may influence degeneration of the intervertebral disc. This gene has not previously been considered a candidate in LDD and further functional work is needed on this hitherto unsuspected pathway.

Early diagnosis to enable early treatment of pre-osteoarthritis

Osteoarthritis is a prevalent and disabling disease affecting an increasingly large swathe of the world population. While clinical osteoarthritis is a late-stage condition for which disease-modifying opportunities are limited, osteoarthritis typically develops over decades, offering a long window of time to potentially alter its course. The etiology of osteoarthritis is multifactorial, showing strong associations with highly modifiable risk factors of mechanical overload, obesity and joint injury. As such, characterization of pre-osteoarthritic disease states will be critical to support a paradigm shift from palliation of late disease towards prevention, through early diagnosis and early treatment of joint injury and degeneration to reduce osteoarthritis risk. Joint trauma accelerates development of osteoarthritis from a known point in time. Human joint injury cohorts therefore provide a unique opportunity for evaluation of pre-osteoarthritic conditions and potential interventions from the earliest stages of degeneration. This review focuses on recent advances in imaging and biochemical biomarkers suitable for characterization of the pre-osteoarthritic joint as well as implications for development of effective early treatment strategies.

Genetics and epigenetics of osteoarthritis

Osteoarthritis (OA) is a common age-related disease that affects the tissues of the synovial joint, leading to loss of function and pain. It impacts on both patient morbidity and mortality. It is a complex, polygenic disease that lacks any large-effect susceptibility loci. Instead, OA susceptibility alleles individually contribute only modestly to the overall disease risk, making their identification challenging. Despite this, breakthroughs have occurred with compelling associations so far reported to polymorphisms within the genes GDF5 and MCF2L and to the genomic region 7q22. The latter two have emerged from genome-wide association scans, which are likely to yield more hits in the near future. As for many complex diseases, it is now apparent that epigenetic effects are also important mediators of disease biology, with DNA methylation, histone modifications and non-coding RNAs all having a role. At present, much of the epigenetic focus has been on cartilage, the tissue at the center of the OA disease process. If we are to get close to a qualitative and quantitative understanding of the impact of epigenetics on OA, then in future the other tissues of the joint will also need to be investigated. One of the more exciting insights to have emerged recently is the fact that epigenetic effects can impact on OA genetic effects and this may be a particularly fruitful avenue for integrating both as we move toward a clearer understanding of the pathophysiology of this intriguing disease.

Genetic susceptibility of intervertebral disc degeneration among young Finnish adults

BACKGROUND

Disc degeneration (DD) is a common condition that progresses with aging. Although the events leading to DD are not well understood, a significant genetic influence has been found. This study was undertaken to assess the association between relevant candidate gene polymorphisms and moderate DD in a well-defined and characterized cohort of young adults. Focusing on young age can be valuable in determining genetic predisposition to DD.

METHODS

We investigated the associations of existing candidate genes for DD among 538 young adults with a mean age of 19 belonging to the 1986 Northern Finland Birth Cohort. Nineteen single nucleotide polymorphisms (SNP) in 16 genes were genotyped. We evaluated lumbar DD using the modified Pfirrmann classification and a 1.5-T magnetic resonance scanner for imaging.

RESULTS

Of the 538 individuals studied, 46% had no degeneration, while 54% had DD and 51% of these had moderate DD. The risk of DD was significantly higher in subjects with an allele G of IL6 SNPs rs1800795 (OR 1.45, 95% CI 1.07-1.96) and rs1800797 (OR 1.37, 95% CI 1.02-1.85) in the additive inheritance model. The role of IL6 was further supported by the haplotype analysis, which resulted in an association between the GGG haplotype (SNPs rs1800797, rs1800796 and rs1800795) and DD with an OR of 1.51 (95% CI 1.11-2.04). In addition, we observed an association between DD and two other polymorphisms, SKT rs16924573 (OR 0.27 95% CI 0.07-0.96) and CILP rs2073711 in women (OR 2.04, 95% CI 1.07-3.89).

CONCLUSION

Our results indicate that IL6, SKT and CILP are involved in the etiology of DD among young adults.

Progression of lumbar disc degeneration over a decade: a heritability study

OBJECTIVES

Lumbar disc degeneration (LDD) is prevalent, age-related and contributes to low back pain. Cross-sectional LDD as determined by MRI scan is known to be highly heritable. The authors postulated that the rate of progression might also be controlled by genetic factors.

METHODS

A 10-year follow-up of MRI-determined LDD was performed in 234 pairs of twin volunteers in the UK and Australia, comprising 90 monozygotic pairs and 144 dizygotic same-sex twin pairs. Of the total sample, 95% were female. The mean age at baseline was 53.3 years (range 32.3-69.5). The rate of progression was calculated and, because the effect of age was non-linear, the sample was divided into age strata and heritability estimated for each trait's progression.

RESULTS

All MRI-determined traits worsened significantly over the period of follow-up (p<0.0001 for each). Change in disc height was not heritable at any age while posterior disc bulge was heritable across all age categories (range 28-53%), with higher heritability in those over 60 years. Change in disc signal intensity and anterior osteophytes were found to be heritable only in those aged under 50 years at baseline (heritability estimates 76% (95% CI 44% to 100%) and 74% (42% to 100%), respectively).

CONCLUSIONS

Longitudinal change in LDD traits is heritable for all traits except disc height, but there is a significant influence of age, which varies across traits. Future studies to define the genetic variants influencing LDD progression should examine MRI traits individually and in women should focus on those under 50 years of age.

Do musculoskeletal degenerative diseases affect mortality and cause of death after 10 years in Japan?

There are several reports from Europe and the United States on mortality from musculoskeletal degenerative diseases; however, no reports have been published from Japan. This study is the first that has examined whether musculoskeletal degenerative diseases affect life prognosis in Japan. As many as 944 persons who were 60 years of age and older and who underwent one or more musculoskeletal checkups (knee, lower back, and bone mineral density examination) were enrolled. Survival and death after 10 years were examined. For each knee, lower back, and bone mineral density examination, subjects were divided into normal and abnormal groups. For each of the examinations (knee, lower back, or bone mineral density), 10-year mortality was compared between the two groups. Also, causes of death were examined after 10 years. As many as 805 subjects survived and 125 died. For those with and without osteoarthritis of the knee, mortality after 10 years was 17 and 10%, respectively. For those with and without lower back abnormalities, mortality after 10 years was 12 and 14%, respectively. For those with or without low bone mineral density, mortality after 10 years was 17 and 10%, respectively. Multivariate analysis adjusted for age, gender, body mass index, and lifestyle revealed that odds ratio of death after 10 years was 2.32 and 2.33 in the presence of osteoarthritis of the knee and a low bone mineral density, respectively, and thus the risk of death after 10 years was significantly high. With regard to the cause of death, cerebrovascular and cardiovascular diseases were most frequently evident in patients with osteoarthritis of the knee. Musculoskeletal degenerative diseases influence mortality after 10 years.

Candidate gene association study of magnetic resonance imaging-based hip osteoarthritis (OA): evidence for COL9A2 gene as a common predisposing factor for hip OA and lumbar disc degeneration

OBJECTIVE

To study whether gene variants associated with lumbar disc degeneration (LDD) phenotypes are also associated with hip osteoarthritis (OA).

METHODS

Magnetic resonance imaging (MRI)-based hip OA changes for 345 twins were assessed and 99 single-nucleotide polymorphisms (SNP) were analyzed.

RESULTS

Variants in the COL9A2 (rs7533552, p = 0.0025) and COL10A1 (rs568725, p = 0.002) genes showed association with hip OA.

CONCLUSION

The associating G allele in COL9A2 changes a glutamine to arginine or to tryptophan and may predispose to both hip OA and LDD, making it a candidate for degenerative connective tissue diseases.

Common variations in estrogen-related genes are associated with severe large-joint osteoarthritis: a multicenter genetic and functional study

OBJECTIVE

Several lines of evidence suggest that estrogens influence the development of osteoarthritis (OA). The aim of this study was to explore the association of two common polymorphisms within the aromatase (CYP19A1) and estrogen receptor (ER) alpha (ESR1) genes with severe OA of the lower limbs.

METHODS

The rs1062033 (CYP19A1) and rs2234693 (ESR1) single nucleotide polymorphisms were genotyped in 5528 individuals (3147 patients with severe hip or knee OA, and 2381 controls) from four centres in Spain and the United Kingdom. Gene expression was measured in femoral bone samples from a group of patients.

RESULTS

In the global analysis, both polymorphisms were associated with OA, but there was a significant sex interaction. The GG genotype at rs1062033 was associated with an increased risk of knee OA in women [odds ratio (OR) 1.23; P=0.04]. The CC genotype at rs2234693 tended to be associated with reduced OA risk in women (OR 0.76, P=0.028, for knee OA; OR=0.84, P=0.076 for hip OA), but with increased risk of hip OA in men (OR 1.28; P=0.029). Women with unfavourable genotypes at both loci had an OR of 1.61 for knee OA (P=0.006). The rs1062033 genotype associated with higher OA risk was also associated with reduced expression of the aromatase gene in bone.

CONCLUSIONS

Common genetic variations of the aromatase and ER genes are associated with the risk of severe OA of the large joints of the lower limb in a sex-specific manner. These results are consistent with the hypothesis that estrogen activity may influence the development of large-joint OA.

Interleukin-4/interleukin-4 receptor gene polymorphisms in hand osteoarthritis

OBJECTIVE

IL-13/IL-4/IL-4R system has strong chondroprotective activity. We investigated polymorphisms in these genes as potential hand osteoarthritis (OA) susceptibility loci by performing a case-control association study.

METHODS

Eighteen common single nucleotide polymorphisms (SNPs) (nine in IL-4R, five in IL-4 and four in IL-13) were genotyped in 403 patients (380 females) with hand OA and 322 healthy controls (308 females).

RESULTS

Two SNPs (rs1805013 and rs1805015), mapping to the IL-4R gene, were associated with P-values of 0.0116 and 0.0305 respectively in the whole sample. As far as the non-erosive hand OA group (n=159) is concerned, the significance level of association of SNP rs1805013 is increased. After correction for multiple testing (correction for the 54 tests) the significance was not retained. None of the IL-13 SNPs analyzed showed association with hand OA. Some of the analyzed SNP within the IL-4 gene showed significant association with hand OA only when considering subgroups of patients. With respect to the CMC1 OA group, two SNPs in IL-4 (rs2243250 and rs2243274) showed association with a P-value of 0.027 and 0.018 respectively. None of these associations remained after correction for multiple testing.

CONCLUSIONS

The present study shows a trend to an association between non-erosive hand OA in Caucasian population and a genetic variant in the coding region of IL-4R gene. Our results, in keeping with previous data on hip OA, confirm the suggestion that IL-4/IL-4R system plays a role in OA pathogenesis. Further confirmation studies on different populations are necessary.

Genome-wide linkage analysis of quantitative biomarker traits of osteoarthritis in a large, multigenerational extended family

OBJECTIVE

The genetic contributions to the multifactorial disorder osteoarthritis (OA) have been increasingly recognized. The goal of the current study was to use OA-related biomarkers of severity and disease burden as quantitative traits to identify genetic susceptibility loci for OA.

METHODS

In a large multigenerational extended family (n = 350), we measured 5 OA-related biomarkers: hyaluronan (HA), cartilage oligomeric matrix protein (COMP), N-propeptide of type IIA collagen (PIIANP), C-propeptide of type II procollagen (CPII), and type II collagen neoepitope (C2C). Single-nucleotide polymorphism markers (n = 6,090) covering the whole genome were genotyped using the Illumina HumanLinkage-12 BeadChip. Variance components analysis, as implemented in the Sequential Oligogenic Linkage Analysis Routines, was used to estimate heritabilities of the quantitative traits and to calculate 2-point and multipoint logarithm of odds (LOD) scores using a polygenic model.

RESULTS

After adjusting for age and sex, we found that 4 of the 5 biomarkers exhibited significant heritability (PIIANP 0.57, HA 0.49, COMP 0.43, C2C 0.30; P < or = 0.01 for all). Fourteen of the 19 loci that had multipoint LOD scores of >1.5 were near to or overlapped with previously reported OA susceptibility loci. Four of these loci were identified by more than 1 biomarker. The maximum multipoint LOD scores for the heritable quantitative biomarker traits were 4.3 for PIIANP (chromosome 8p23.2), 3.2 for COMP (chromosome 8q11.1), 2.0 for HA (chromosome 6q16.3), and 2.0 for C2C (chromosome 5q31.2).

CONCLUSION

Herein, we report the first evidence of genetic susceptibility loci identified by OA-related biomarkers in an extended family. Our results demonstrate that serum concentrations of PIIANP, HA, COMP, and C2C have substantial heritable components, and using these biomarkers, several genetic loci potentially contributing to the genetic diversity of OA were identified.

Radiographic severity of knee osteoarthritis is conditional on interleukin 1 receptor antagonist gene variations

BACKGROUND

A lack of biomarkers that identify patients at risk for severe osteoarthritis (OA) complicates development of disease-modifying OA drugs.

OBJECTIVE

To determine whether inflammatory genetic markers could stratify patients with knee OA into high and low risk for destructive disease.

METHODS

Genotype associations with knee OA severity were assessed in two Caucasian populations. Fifteen single nucleotide polymorphisms (SNPs) in six inflammatory genes were evaluated for association with radiographic severity and with synovial fluid mediators in a subset of the patients.

RESULTS

Interleukin 1 receptor antagonist (IL1RN) SNPs (rs419598, rs315952 and rs9005) predicted Kellgren-Lawrence scores independently in each population. One IL1RN haplotype was associated with lower odds of radiographic severity (OR=0.15; 95% CI 0.065 to 0.349; p<0.0001), greater joint space width and lower synovial fluid cytokine levels. Carriage of the IL1RN haplotype influenced the age relationship with severity.

CONCLUSION

IL1RN polymorphisms reproducibly contribute to disease severity in knee OA and may be useful biomarkers for patient selection in disease-modifying OA drug trials.

Associations of 25 structural, degradative, and inflammatory candidate genes with lumbar disc desiccation, bulging, and height narrowing

OBJECTIVE

To examine the allelic diversity of structural, inflammatory, and matrix-modifying gene candidates and their association with disc degeneration.

METHODS

Subjects were 588 men ages 35-70 years. We investigated associations of single-nucleotide polymorphisms in AGC1 and in 12 collagen, 8 interleukin, and 4 matrix metalloproteinase genes with quantitative magnetic resonance imaging measurements of disc desiccation and disc bulging and height narrowing scores, after controlling for age and suspected risk factors. Analyses were performed using QTDT software. P values were derived from 1,000 permutations, and empirical P values for global significance also were applied.

RESULTS

Twelve of the 99 variants in 25 selected candidate genes provided evidence of association (P < 0.05) with disc signal intensity in the upper and/or lower lumbar regions. Allelic variants of AGC1 (rs1042631; P = 0.001), COL1A1 (rs2075555; P = 0.005), COL9A1 (rs696990; P = 0.00008), and COL11A2 (rs2076311; P = 0.018) genes provided the most significant evidence of association with disc signal intensity. The same variants of AGC1 (P = 0.010) and COL9A1 (P = 0.014), as well as variants in the COL11A1 gene (rs1463035 [P = 0.004]; rs1337185 [P = 0.015]) were also associated with disc bulging, as was AGC1 with disc height narrowing (rs1516797; P = 0.005). In addition, 4 allelic variants in the immunologic candidate genes (rs2071375 in IL1A [P = 0.027]; rs1420100 in IL18RAP [P = 0.005]) were associated with disc signal intensity.

CONCLUSION

Genetic variants account for interindividual differences in disc matrix synthesis and degradation. The accuracy of the quantitative disc signal intensity measurements we used likely enhanced our ability to observe these associations. Our findings shed light on possible mechanisms of degeneration and support the view that disc degeneration is a polygenetic condition.

The genetic influence on radiographic osteoarthritis is site specific at the hand, hip and knee

Objective. To identify whether a shared genetic influence accounts for the occurrence of OA at different skeletal sites.

Methods. Multivariate modelling of data on prevalent radiographic OA at the hand (DIP, PIP and CMC joints), hip and knee joints assessed in 992 monozygotic and dizygotic female twin participants from the TwinsUK Registry.

Results. OA at all the five joint sites was heritable. Genetic influences were strongly correlated among joints in the hand; however, there was little evidence of common genetic pathways to account for the co-occurrence of OA at the hand, hip and knee.

Conclusions. While genetic influences are important in explaining the variation in occurrence of OA at the hand, hip and knee, there is no evidence that common or shared genetic factors determine the occurrence of disease across all these skeletal sites. The findings suggest that there are important aetiological differences in the disease that are site-specific in women. These results have implications for the design of studies examining the genetic basis of OA as well as for strategies aimed at preventing and treating the disease.