Osteoarthritis-susceptibility locus on chromosome 11q, detected by linkage

Osteoarthritis: Trauma vs Disease

Osteoarthritis (OA) is the most prevalent joint disease characterized by pain and degenerative lesions of the cartilage, subchondral bone, and other joint tissues. The causes of OA remain incompletely understood. Over the years, it has become recognized that OA is a multifactorial disease. In particular, aging and trauma are the main risk factors identified for the development of OA; however, other factors such as genetic predisposition, obesity, inflammation, gender and hormones, or metabolic syndrome contribute to OA development and lead to a more severe outcome. While this disease mainly affects people older than 60 years, OA developed after joint trauma affects all range ages and has a particular impact on young individuals and people who have highest levels of physical activity such as athletes. Traumatic injury to the joint often results in joint instability or intra-articular fractures which lead to posttraumatic osteoarthritis (PTOA). In response to injury, several molecular mechanisms are activated, increasing the production and activation of different factors that contribute to the progression of OA.In this chapter, we have focused on the interactions and contribution of the multiple factors involved in joint destruction and progression of OA. In addition, we overview the main changes and molecular mechanisms related to OA pathogenesis.

Reduced Expression of FADS1 Predicts Worse Prognosis in Non-Small-Cell Lung Cancer

Objective: Fatty acid desaturase 1 is a member of the fatty acid desaturase, which is related to a number of diseases. However, its role in cancers remains unclear. This study was to explore the clinical importance of FADS1 expression in non-small-cell lung cancer (NSCLC). Materials and Methods: Immunochemistry was used to evaluate FADS1 expressions in 216 paraffin-embedded specimens. The expression of FADS1 was divided into high and low groups. The clinical and prognostic significance of FADS1 expression was analyzed statistically by Kaplan-Meier estimate and Cox regression model. Results: FADS1 overexpressed in normal bronchial mucosa compared with non-small-cell lung cancer. Reduced FADS1 expression was associated with tumor size (P=0.023) and histological grade (P<0.0001). Patients with lower expression of FADS1 had shorter overall survival and disease free survival (P=0.001 and P=0.002). Multivariate analysis showed FADS1 expression was an independent prognostic factor in NSCLC (P=0.011). Conclusion: Reduced expression of FADS1 suggests pessimistic prognosis for NSCLC patients. Further studies are warranted.

LRP receptor family member associated bone disease

A dozen years ago the identification of causal mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) gene involved in two rare bone disorders propelled research in the bone field in totally new directions. Since then, there have been an explosion in the number of reports that highlight the role of the Wnt/β-catenin pathway in the regulation of bone homeostasis. In this review we discuss some of the most recent reports (in the past 2 years) highlighting the involvement of the members of the LRP family (LRP5, LRP6, LRP4, and more recently LRP8) in the maintenance of bone and their implications in bone diseases. These reports include records of new single nucleotides polymorphisms (SNPs) and haplotypes that suggest variants in these genes can contribute to subtle variation in bone traits to mutations that give rise to extreme bone phenotypes. All of these serve to further support and reinforce the importance of this tightly regulated pathway in bone. Furthermore, we discuss provocative reports suggesting novel approaches through inhibitors of this pathway to treat rarer diseases such as Osteoporosis-Pseudoglioma Syndrome (OPPG), Osteogenesis Imperfecta (OI), and Sclerosteosis/Van Buchem disease. It is hoped that by understanding the role of each component of the pathway and their involvement in bone diseases that this knowledge will allow us to develop new, more effective therapeutic approaches for more common diseases such as post-menopausal osteoporosis, osteoarthritis, and rheumatoid arthritis as well as these rarer bone diseases.

The epidemiology of osteoarthritis

Osteoarthritis (OA) is a leading cause of disability and its incidence is rising due to increasing obesity and an ageing population. Risk factors can be divided into person-level factors, such as age, sex, obesity, genetics, race/ethnicity and diet, and joint-level factors including injury, malalignment and abnormal loading of the joints. The interaction of these risk factors is complex and provides a challenge to the managing physician. The purpose of this review is to illustrate how each of these factors interact together to instigate incident OA as well as to outline the need for ongoing epidemiologic studies for the future prevention of both incident and progressive OA. It is only by understanding the impact of this disease and the modifiable risk factors that we will be able to truly target public health prevention interventions appropriately.

Elevated immune-inflammatory signaling in mood disorders: a new therapeutic target?

Converging translational evidence has implicated elevated immune-inflammatory signaling activity in the pathoetiology of mood disorders, including major depressive disorder and bipolar disorder. This is supported in part by cross-sectional evidence for increased levels of proinflammatory eicosanoids, cytokines and acute-phase proteins during mood episodes, and prospective longitudinal evidence for the emergence of mood symptoms in response to chronic immune-inflammatory activation. In addition, mood-stabilizer and atypical antipsychotic medications downregulate initial components of the immune-inflammatory signaling pathway, and adjunctive treatment with anti-inflammatory agents augment the therapeutic efficacy of antidepressant, mood stabilizer and atypical antipsychotic medications. Potential pathogenic mechanisms linked with elevated immune-inflammatory signaling include perturbations in central serotonin neurotransmission and progressive white matter pathology. Both heritable genetic factors and environmental factors including dietary fatty-acid composition may act in concert to sustain elevated immune-inflammatory signaling. Collectively, these data suggest that elevated immune-inflammatory signaling is a mechanism that is relevant to the pathoetiology of mood disorders, and may therefore represent a new therapeutic target for the development of more effective treatments.

Role of FADS1 and FADS2 polymorphisms in polyunsaturated fatty acid metabolism

Tissue availability of polyunsaturated fatty acids (PUFAs) depends on dietary intake and metabolic turnover and has a major impact on human health. Strong associations between variants in the human genes fatty acid desaturase 1 (FADS1, encoding Delta-5 desaturase) and fatty acid desaturase 2 (FADS2, encoding Delta-6 desaturase) and blood levels of PUFAs and long-chain PUFAs (LC-PUFAs) have been reported. The most significant associations and the highest proportion of genetically explained variability (28%) were found for arachidonic acid (20:4n-6), the main precursor of eicosanoids. Subjects carrying the minor alleles of several single nucleotide polymorphisms had a lower prevalence of allergic rhinitis and atopic eczema. Therefore, blood levels of PUFAs and LC-PUFAs are influenced not only by diet, but to a large extent also by genetic variants common in a European population. These findings have been replicated in independent populations. Depending on genetic variants, requirements of dietary PUFA or LC-PUFA intakes to achieve comparable biological effects may differ. We recommend including analyses of FADS1 and FADS2 polymorphism in future cohort and intervention studies addressing biological effects of PUFAs and LC-PUFAs.

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.

A large kindred of early-onset osteoarthritis of the knee and hip: excluding the link to COL2A1 gene

OBJECTIVES

To characterize a large extended family with early-onset OA of the knee and investigate its associations with the COL2A1 gene.

METHODS

Phenotype assessments were conducted in a six-generation family to identify individuals affected with OA. Short tandem repeat polymorphic (STRP) markers and DNA sequencing were performed to investigate the involvement of the COL2A1 gene in this family.

RESULTS

The kindred affected with OA showed autosomal dominant inheritance. The mean age of onset was 37.3 +/- 19.2, 29.8 +/- 13.7 and 12.0 +/- 7.2 years for generations IV, V and VI, respectively, and 25 +/- 16.1 years for males and 34.3 +/- 15.5 years for females. The height of the affected males was shorter than the unaffected males (155.9 +/- 11.4 vs 164.5 +/- 16.0 cm, P = 0.010). Arm span in the affected males was also significantly shorter than the unaffected males (158.4 +/- 12.5 vs 165.3 +/- 16.7 cm, P = 0.027). However, both height and arm span were not reduced in the affected female OA patients. STRP markers surrounding COL2A1 locus did not show linkage of the COL2A1 locus with the OA. Sequencing of COL2A1 gene revealed three single nucleotide polymorphisms but no mutation was found in the affected patients.

CONCLUSIONS

The COL2A1 was not a susceptibility gene responsible for the OA phenotype in a large extended kindred with familial early-onset OA. The availability of DNA samples will allow genome-wide linkage study to identify the susceptibility locus.

The contribution of genes to osteoarthritis

Osteoarthritis (OA) is the most prevalent form of arthritis in the elderly. A large body of evidence, including familial aggregation and classic twin studies, indicates that primary OA has a strong hereditary component that is likely polygenic in nature. Traits related to OA, such as longitudinal changes in cartilage volume and progression of radiographic features, are also under genetic control. In recent years several linkage analyses and candidate gene studies have been performed and unveiled some of the specific genes involved in disease risk, such as FRZB and GDF5. This article discusses the impact that future genome-wide association scans can have on our understanding of the pathogenesis of OA and on identifying individuals at high risk for developing severe OA.

The contribution of genes to osteoarthritis

Osteoarthritis (OA) is the most prevalent form of arthritis in the elderly. A large body of evidence, including familial aggregation and classic twin studies, indicates that primary OA has a strong hereditary component that is likely polygenic in nature. Furthermore, traits related to OA, such as longitudinal changes in cartilage volume and progression of radiographic features, are also under genetic control. In recent years, several linkage analysis and candidate gene studies have been performed and have unveiled some of the specific genes involved in disease risk, such as FRZB and GDF5. The authors discuss the impact that future genome-wide association scans can have on our understanding of the pathogenesis of OA and on identifying individuals at high risk for developing severe OA.

Biomarkers associated with clinical phenotypes of hand osteoarthritis in a large multigenerational family: the CARRIAGE family study

OBJECTIVE

To evaluate biological markers as potential quantitative traits of clinical osteoarthritis (OA) in a large multigenerational family in the Carolinas of the USA known as the CARRIAGE (CARolinas Region Interaction of Aging, Genes and Environment) family.

METHODS

During a series of three family reunions over 6 years, we ascertained 365 family members. We performed clinical hand examinations (n=287), and obtained sera (n=278) for seven OA-related biomarkers [type IIA collagen N-propeptide (PIIANP), type II procollagen carboxy-propeptide (CPII), neoepitope from cleavage of CII (C(2)C), cartilage oligomeric matrix protein (COMP), hyaluronan (HA), high-sensitive C-reactive protein (hs-CRP), and glycated serum protein (GSP)]. Three hand OA definitions were evaluated--clinical ACR (American College of Rheumatology) and GOGO (Genetics of Generalized OA) criteria, and any single hand joint involvement. Non-hand OA was defined as a negative hand examination for OA but varying prevalence of joint symptoms; the control group was defined as having neither symptoms nor evidence for clinical hand OA.

RESULTS

Mean lnHA, lnCOMP, and lnhs-CRP were significantly higher in the hand OA group, compared with the non-hand OA or control group. Adjusted for age and sex, mean lnPIIANP (a collagen II synthesis marker) was significantly lower in the hand OA group compared with the other groups. Among those without clinical hand OA, GSP was associated with hand joint symptoms.

CONCLUSIONS

This is the first report, to our knowledge, showing an association of OA biomarkers and hand OA based on physical examination alone. Analyses using these biomarkers as quantitative traits could reveal novel genetic loci and facilitate exploration of the genetic susceptibility to OA.

Congenic strains displaying similar clinical phenotype of arthritis represent different immunologic models of inflammation

Proteoglycan (PG)-induced arthritis (PGIA) is an autoimmune inflammatory disease controlled by multiple genes in the murine genome. BALB/c x DBA/2 congenic strains carrying four major PGIA chromosome loci were immunized, and positions of loci on chromosomes 3, 7, 8 and 19 (loci Pgia26, Pgia21, Pgia4 and Pgia12, respectively) were confirmed. Each congenic strain exhibited a different pattern of regulation of clinical and immunologic features of PGIA, and these features were significantly influenced by gender. Locus Pgia26 delayed PGIA onset in males and females, and the effect was associated with a lower rate of antigen-induced lymphocyte proliferation and lower production of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and interleukin-4 (IL-4). Pgia12 similarly delayed onset in males, but the effect was achieved by elevated proliferation of PG-specific lymphocytes and enhanced production of IFN-gamma and IL-4. The effect of the Pgia21 locus was arthritis-suppressive in females but PGIA-permissive in congenic males. These opposite effects are attributed to two-fold higher serum autoantibody and IL-6 levels in males than in females. Our study supports the idea that each congenic strain represents a different immunologic subtype of PGIA, providing an explanation for the complex etiology and various clinical phenotypes of rheumatoid arthritis.

[Pathogenesis of osteoarthritis--a snapshot]

Osteoarthritis (OA) is a degenerative joint disease of as yet unknown pathology. Combining genome and transcriptome analyses with methods from systems biology helped to identify OA as the result of active disease processes. Here, chondrocytes are of central importance as they seem to undergo increased apoptosis and to shift their metabolism towards cartilage degradation.

Hip osteoarthritis: what the radiologist wants to know

Osteoarthritis (OA) is the most common disease of the hip joint seen in adults. The diagnosis of OA is based on a combination of radiographic findings of joint degeneration and characteristic subjective symptoms. The lack of a radiographic consensus definition has resulted in a variation of the published incidences and prevalence of OA. The chronological sequence of degeneration includes the following plain radiographic findings: joint space narrowing, development of osteophytes, subchondral sclerosis, and cyst formation. There are cases though, that plain radiographs show minor changes and the clinical suspicion of early disease can be confirmed with more sophisticated imaging methods, such as multi-detector computed tomography and MR imaging. The present article will review all the clinical information on the hip OA together with an updated radiological approach, with emphasis on the early depiction and the differential diagnosis of the disease.

Q89R polymorphism in the LDL receptor-related protein 5 gene is associated with spinal osteoarthritis in postmenopausal Japanese women

STUDY DESIGN

An association study investigating the genetic etiology for spinal osteoarthritis.

OBJECTIVE

To determine the association of single-nucleotide polymorphism (SNP) causing an amino-acid change (Q89R) in the low-density lipoprotein receptor-related protein 5 (LRP5) coding region with spinal osteoarthritis.

SUMMARY OF BACKGROUND DATA

Wnt/beta-catenin signaling pathway regulates bone density through a Wnt coreceptor LRP5. This pathway is also involved in cartilage development and homeostasis, suggesting that genetic variation in LRP5 gene may affect the pathogenesis of cartilage-related diseases, such as osteoarthritis.

METHODS

We evaluated the presence of osteophytes, endplate sclerosis, and narrowing of disc spaces in 357 Japanese postmenopausal women. Missense coding SNP for Q89R of LRP5 gene was determined using TaqMan polymerase chain reaction (PCR) method.

RESULTS

We found that subjects without the R allele (QQ; n = 321) had a significantly lower osteophyte formation score than did subjects bearing at least one R allele (QR + RR; n = 36) (7.80 vs. 10.89, P = 0.0019 by analysis of covariance).

CONCLUSIONS

We suggest that a genetic variation at the LRP5 gene locus is associated with spinal osteoarthritis, in line with the involvement of the LRP5 gene in the bone and cartilage metabolism.

Tumour necrosis factor alpha-stimulated gene-6 inhibits osteoblastic differentiation of human mesenchymal stem cells induced by osteogenic differentiation medium and BMP-2

To better understand the molecular pathogenesis of OPLL (ossification of the posterior longitudinal ligament) of the spine, an ectopic bone formation disease, we performed cDNA microarray analysis on cultured ligament cells from OPLL patients. We found that TSG-6 (tumour necrosis factor alpha-stimulated gene-6) is down-regulated during osteoblastic differentiation. Adenovirus vector-mediated overexpression of TSG-6 inhibited osteoblastic differentiation of human mesenchymal stem cells induced by BMP (bone morphogenetic protein)-2 or OS (osteogenic differentiation medium). TSG-6 suppressed phosphorylation and nuclear accumulation of Smad 1/5 induced by BMP-2, probably by inhibiting binding of the ligand to the receptor, since interaction between TSG-6 and BMP-2 was observed in vitro. TSG-6 has two functional domains, a Link domain (a hyaluronan binding domain) and a CUB domain implicated in protein interaction. The inhibitory effect on osteoblastic differentiation was completely lost with exogenously added Link domain-truncated TSG-6, while partial inhibition was retained by the CUB domain-truncated protein. In addition, the inhibitory action of TSG-6 and the in vitro interaction of TSG-6 with BMP-2 were abolished by the addition of hyaluronan. Thus, TSG-6, identified as a down-regulated gene during osteoblastic differentiation, suppresses osteoblastic differentiation induced by both BMP-2 and OS and is a plausible target for therapeutic intervention in OPLL.

Absence of linkage to chromosomes 6q and 16p in a Greek population with knee osteoarthritis

Osteoarthritis (OA) is a common age-related debilitating disease of the joints characterized by degeneration of the articular cartilage which leads to joint pain, discomfort, and immobility. Several risk factors have been associated with OA including a genetic predisposition. Specific chromosomal regions have thus far been associated with susceptibility to OA, the strongest being on chromosomes 2, 6, and 16. We hereby report our data on 34 Central Greek knee OA families that were investigated for linkage to the chromosome 6q and 16p susceptibility regions. All affected members had undergone total knee replacement surgery (TKR) at a single large Orthopedics Unit in Central Greece. Nineteen microsatellite markers were selected, 15 for chromosome 6q and 4 for chromosome 16p at a distance of approximately 7 cm. Allele fragment sizes were determined by an automated DNA sequencer using the Fragment Analysis Software. Our results revealed a statistically significant difference in the ratio of affected females to males with knee OA and also showed that there is no evidence of linkage to regions 6q and 16p in a cohort of Central Greek pedigrees with knee OA.

Osteoarthritis susceptibility loci defined by genome scan meta-analysis

Genome scans for osteoarthritis (OA) have yielded inconsistent results. The absence of replication of linkage might be due to lack of power of individual studies. A meta-analysis of the published data was performed to assess evidence for linkage of OA across genome scan studies. Three OA whole-genome scans including 893 families with 3,000 affected individuals were used for genome scan meta-analysis (GSMA). A total of 5 bins lie above 95% confidence level (P = 0.05) and 1 bin is above 99% confidence level (P = 0.01) in OA GSMA; bins 7.6 (7q34-7q36.3, Psumrnk = 0.0035), 11.3 (11p12-11q13.4), 6.3 (6p21.1-6q15), 2.8 (2q31.1-2q34) and 15.3 (15q21.3-15q26.1). The highest summed rank was observed at bin 7.6. In conclusion, the OA GSMA has shown chromosome 7q34-7q36.3 with the highest summed rank and four additional loci with significant summed ranks across studies.

Familial osteoarthritis of the hip joint associated with acetabular dysplasia maps to chromosome 13q

Genetic factors have been implicated in osteoarthritis (OA), particularly in OA of the hip joint (hip OA). Several instances of familial hip OA that show distinctive modes of inheritance but that differ from chondrodysplasia have been reported. Here, we report the characterization of a large Japanese family with an inherited disease of the hip that is indistinguishable from common hip OA, as evidenced by clinical symptoms and radiographs of the joint. This family contained eight patients in 4 generations. Affected individuals develop pain in the hip joint during adolescence, and the disease progresses to severe crippling before age 60 years. Patients generally are in good health, height is not reduced, and there is no extraskeletal involvement suggestive of chondrodysplasia. The skeletal change is bilateral acetabular dysplasia followed by OA, which occurs after age approximately 40 years and is indistinguishable from idiopathic nonfamilial dysplastic hip OA. This trait shows autosomal dominant inheritance, with a considerably consistent phenotype. Genomewide screening revealed linkage at chromosome 13q22, and haplotype analysis narrowed the locus to a 6.0-cM interval between markers D13S1296 and D13S162, with a maximal multipoint LOD score of 3.57. The family described here represents a novel genetic entity as a monogenic form of hip OA. Its further characterization can aid in elucidating the etiology and pathogenesis of a common idiopathic form of OA.

Common genetic variants of the FADS1 FADS2 gene cluster and their reconstructed haplotypes are associated with the fatty acid composition in phospholipids

Fatty acid composition in membranes plays an important role in cellular processes and has shown to be associated with the aetiology of several complex diseases in humans. We report strong associations between variants in the human delta-5 and delta-6 desaturase genes FADS1 FADS2 and fatty acid composition in serum phospholipids. Eighteen polymorphisms located in this gene cluster were genotyped in 727 adults from Erfurt, a German centre of the European Community Respiratory Health Survey. The cluster is located at chromosome 11q12-11q13.1, a region repeatedly found to be linked with atopy and other complex diseases. Polymorphisms and statistically reconstructed haplotypes of FADS1 and the upstream region of FADS2 showed strongest associations with the level of the direct precursor of inflammatory eicosanoids, the n-6 fatty acid arachidonic acid (C20:4n-6), also strong associations with levels of the n-6 fatty acids C18:2n-6, C18:3n-6, C20:2n-6, C20:3n-6, C22:4n-6 and of the n-3 fatty acids C18:3n-3, C20:5n-3 and C22:5n-3 (P-values < 1.0 x 10(-13)). Carriers of the rare alleles of several SNPs and their respective haplotypes had a lower prevalence of allergic rhinitis and atopic eczema. No association was found for total and specific IgE levels.

Investigations in generalized osteoarthritis. Part 1: genetic study of Heberden's nodes

OBJECTIVE

Until the current molecular genetic investigations, all available data concerning the genetic predisposition to Heberden's nodes are based on a single investigation by Stecher in the 1940s. There is controversy in the literature about the correlation between Heberden's nodes and generalized osteoarthritis (GOA). Our own epidemiological and clinical investigations support this correlation. Therefore, the question arises as to whether the remarkable inheritance described by Stecher is correct and whether Heberden's nodes can indeed be used as a genetic marker for GOA.

METHODS

From our clinical trial on 106 patients with Heberden's arthritis, we could identify 88 families from index cases. Altogether, we included 931 family members over a maximum of four generations. First of all, the genealogical trees of the families were established. Subsequently, we examined the patients' hands in respect of Heberden's nodes and completed the genealogical trees during home visits.

RESULTS

In the 88 families analyzed, 152 patients with manifest Heberden's arthritis were listed (26 males, 126 females). The genealogical analysis of 156 descendants (74 males, 82 females) of 93 patients with Heberden's nodes suggests autosomal dominant inheritance. In view of the age-related manifestation and age pattern of the descendants, we postulate a heterozygous manifestation for women (dominant gene action) and only a homozygous manifestation for men (recessive gene action).

CONCLUSIONS

The genealogic analysis does not contrast with the quite remarkable inheritance described by Stecher but rather supports the hypothesis that manifestation is dominant in females and recessive in males. From our point of view, this heredity does not contradict latest genetic assays which show the possibility of genetic defects causing the hereditary osteoarthritis (OA).

Osteoarthritis susceptibility loci defined by genome scan meta-analysis

Genome scans for osteoarthritis (OA) have yielded inconsistent results. The absence of replication of linkage might be due to the lack of power of individual studies. A meta-analysis of published data was performed to assess evidence for linkage of OA across genome scan studies. Three OA whole-genome scans including 893 families with 3,000 affected individuals were used for genome scan meta-analysis (GSMA). A total of five bins lie above 95% confidence level (P=0.05) and one bin is above 99% confidence level (P=0.01) in OA GSMA; bins 7.6 (7q34-7q36.3, P (sumrnk) =0.0035), 11.3 (11p12-11q13.4), 6.3 (6p21.1-6q15), 2.8 (2q31.1-2q34) and 15.3 (15q21.3-15q26.1). The highest summed bin was bins 7.6. In conclusion, the OA GSMA has shown that chromosome 7q34-7q36.3 have the highest summed rank and four additional loci with significant summed ranks across studies.

Linkage to nodal osteoarthritis: quantitative and qualitative analyses of data from a whole-genome screen identify trait-dependent susceptibility loci

OBJECTIVE

To identify susceptibility loci for nodal osteoarthritis.

METHODS

A genome screen at an average marker spacing of 9.29 cM was carried out on 558 people from 202 families, of whom 491 had nodal osteoarthritis. All genotyped people were graded for the incidence and severity of distal interphalangeal (DIP) nodes, and radiographs from 354 people were graded for joint-space narrowing (JSN) and osteophytes (OSTs). Age-regressed indices for DIP nodes, JSN and OSTs were calculated using these phenotypic data. Affected sibling pair (ASP) and quantitative trait analyses were carried out using MERLIN.

RESULTS

The data analysis identified suggestive linkage to loci on chromosomes 3 (for JSN and OST), 4 (for JSN), 8 (for DIP), 11 (for radiographic osteoarthritis) and 16 (for JSN). Both the ASP and quantitative analyses identified the loci on chromosomes 4 and 11. The loci on chromosomes 3 and 16 overlap with those previously identified for large-joint osteoarthritis. Of the loci identified by the quantitative analyses with the logarithm of the odds of linkage >1.5, two were linked to more than one trait, whereas nine were linked to single traits: one for DIP, six for JSN and two for OST.

CONCLUSION

The ASP and quantitative analyses of the cohort with nodal osteoarthritis suggest that multiple susceptibility loci for osteoarthritis influence the traits, which combine to form the osteoarthritis phenotype, and that these loci may not act exclusively on the joints of the hand.

Hip joint replacement surgery for idiopathic osteoarthritis aggregates in families

In order to determine whether there is a genetic component to hip or knee joint failure due to idiopathic osteoarthritis (OA), we invited patients (probands) undergoing hip or knee arthroplasty for management of idiopathic OA to provide detailed family histories regarding the prevalence of idiopathic OA requiring joint replacement in their siblings. We also invited their spouses to provide detailed family histories about their siblings to serve as a control group. In the probands, we confirmed the diagnosis of idiopathic OA using American College of Rheumatology criteria. The cohorts included the siblings of 635 probands undergoing total hip replacement, the siblings of 486 probands undergoing total knee replacement, and the siblings of 787 spouses. We compared the prevalence of arthroplasty for idiopathic OA among the siblings of the probands with that among the siblings of the spouses, and we used logistic regression to identify independent risk factors for hip and knee arthroplasty in the siblings. Familial aggregation for hip arthroplasty, but not for knee arthroplasty, was observed after controlling for age and sex, suggesting a genetic contribution to end-stage hip OA but not to end-stage knee OA. We conclude that attempts to identify genes that predispose to idiopathic OA resulting in joint failure are more likely to be successful in patients with hip OA than in those with knee OA.

Association between a variation inLRCH1 and knee osteoarthritis: A genome-wide single-nucleotide polymorphism association study using DNA pooling

OBJECTIVE

To perform a large-scale association analysis of single-nucleotide polymorphisms (SNPs) in patients with radiographically defined osteoarthritis (OA) of the knee.

METHODS

We examined >25,000 SNPs located within approximately 14,000 genes for associations with radiographically defined knee OA, using polymerase chain reaction and MassExtend amplification techniques. Allele frequencies were estimated initially in DNA pools from 335 female patients with knee OA and 335 asymptomatic and radiographically negative female control subjects. All were of northern European ancestry. Significant allele frequency differences were validated by genotyping of individual DNA samples. Confirmed significant findings were verified in 2 additional case-control samples from the UK (443 cases and 303 controls) and Newfoundland (346 cases and 264 controls). Chondrosarcoma cell lines were used to test for potential differences in gene expression.

RESULTS

The marker most strongly associated with the risk of knee OA was rs912428, a C/T polymorphism in intron 1 of LRCH1, a gene on chromosome 13q14 that encodes a novel protein of as-yet-unknown function. The frequency of the T allele compared with controls was consistently increased by 40% across all 3 case-control groups. Additional subanalyses in case-control samples with hip OA and hand OA suggested similar trends, but did not reach statistical significance. Association fine-mapping using 10 additional SNPs in LRCH1 confirmed intron 1 as the region of highest association but failed to reveal variations with significance stronger than the marker SNP, as did the haplotype analysis. LRCH1 was not up-regulated or overexpressed in chondrosarcoma cell lines exposed to inflammatory stimuli, suggesting a possible structural role.

CONCLUSION

A genetic variant in LRCH1 was consistently associated with knee OA in 3 samples from 2 populations. Our results also suggest that the same association with OA may exist at other sites. Additional genetic and experimental work is needed to elucidate the precise mechanism by which the LRCH1 gene influences OA risk.

Osteoarthritis: an overview of the disease and its treatment strategies

Osteoarthritis (OA) is currently defined by the American College of Rheumatology as a "heterogeneous group of conditions that leads to joint symptoms and signs which are associated with defective integrity of articular cartilage, in addition to related changes in the underlying bone at the joint margins." Its prevalence after the age of 65 years is about 60% in men and 70% in women. The etiology of OA is multifactorial, with inflammatory, metabolic, and mechanical causes. A number of environmental risk factors, such as obesity, occupation, and trauma, may initiate various pathological pathways. OA indicates the degeneration of articular cartilage together with changes in subchondral bone and mild intraarticular inflammation. The principal treatment objectives are to control pain adequately, improve function, and reduce disability. Acetaminophen is frequently used for symptomatic OA with mild to moderate pain. Nonsteroidal antiinflammatory drugs (NSAIDs) are more effective in the case of moderate-severe pain, but they have an increased risk of serious upper gastrointestinal adverse events. The newer cyclooxygenase COX-2 specific inhibitors (Coxibs) are as efficacious as traditional NSAIDs and have a better gastrointestinal safety profile. Other compounds (eg, chondroitin sulfate, diacerein, glucosamine sulfate) have a symptomatic effect that is slower and less than that of NSAIDs. The structure-modifying effects of drugs are currently being evaluated, and both glucosamine sulfate and diacerein have been shown in some trials to have a beneficial structural effect. Nonpharmacological interventions are frequently and widely used in the management of OA patients, but there is little evidence that they are effective: the best studied and most successful nonpharmacological interventions are patient education, self-management, and exercise. There is some evidence for the pain-relieving efficacy of thermotherapy and transcutaneous electrical nerve stimulation (TENS) but not of electrotherapy, acupuncture, homeopathy, or manual therapy. The value of interventions aimed at improving function and maximizing independence (occupational therapy, walking aids, workplace adaptation) is also unclear. The disease course and patient's requirements often change over time, thus requiring a periodic review and readjustment of therapy rather than the rigid continuation of a single treatment.

Haplotypes of the low-density lipoprotein receptor-related protein 5 (LRP5) gene: are they a risk factor in osteoarthritis?

OBJECTIVE

Several genome-wide scans have revealed an osteoarthritis (OA)-susceptibility locus on chromosome 11q in close proximity to the low-density lipoprotein receptor-related protein 5 (LRP5) gene. The regulation of bone mass is under the control of LRP5 and since increased bone mass is thought to play a role in the pathology of OA we examined LRP5 polymorphisms and haplotypes to determine if variants of this locus may predispose to OA.

METHODS

A UK control population of 187 individuals was examined for five commonly occurring polymorphisms against a cohort of 158 DNAs from patients with knee OA. An additional UK cohort was also examined to confirm the findings of the first study; this second group consisted of 110 knee OA patients. Haplotype analysis was also performed on patient and control DNAs.

RESULTS

A study of individual polymorphisms revealed no association with disease. However, haplotype analysis of the initial two populations revealed a common haplotype (C-G-C-C-A) that provided a 1.6-fold increased risk of OA (P(c)=0.021). The data obtained from the second cohort confirmed the initial findings, with a 1.6-fold increased risk observed within this cohort for the risk haplotype (P=0.012).

CONCLUSIONS

A closer investigation of LRP5 and associated Wnt signalling molecules in OA will help determine disease aetiology and the development of novel treatment strategies that specifically target the bone compartment.

Lack of support for the presence of an osteoarthritis susceptibility locus on chromosome 6p

OBJECTIVE

To replicate, in a Northern Irish population, the previously reported association between a locus on chromosome 6 and hip osteoarthritis (OA).

METHODS

Patients with hip OA were identified from a registry of patients who had undergone total hip replacement surgery over an 8-year period at a single large orthopedic unit in Northern Ireland. Patients identified as index cases were contacted by mail and asked to reply only if another family member also had undergone total hip replacement surgery. Using this approach, we identified 288 sibling pairs concordant for primary hip OA. DNA was extracted from peripheral blood, and microsatellite markers were amplified by polymerase chain reaction and subsequently genotyped.

RESULTS

No evidence of linkage to this region was demonstrated by either 2-point analysis or multipoint analysis of 17 microsatellites.

CONCLUSION

The reported association between a locus on chromosome 6 and hip OA could not be confirmed in this population. Different methods of ascertainment and phenotyping of OA may contribute to the current inability to replicate genetic associations for hip OA.

Functional variants within the secreted frizzled-related protein 3 gene are associated with hip osteoarthritis in females

Osteoarthritis (OA) is a leading cause of disability in Western society with multiple risk factors, including a complex genetic pattern. Identifying loci involved in the heredity of OA might lead to insights into the molecular pathogenesis of this common disorder. A previous genome scan mapped a primary hip OA susceptibility locus to chromosome 2q with a maximum multipoint logarithm of odds score of 1.6 in 378 affected sibling pair families. Here, microsatellite targeting of eight candidate genes in this region from 2q23-2q32 demonstrated significant associations with the tumor necrosis factor alpha-induced protein 6 gene in all probands and the integrin alpha 6 and frizzled motif associated with bone development (FRZB) genes in female probands. However, genotyping showed lack of association for a nonsynonymous single-nucleotide polymorphism in tumor necrosis factor alpha-induced protein 6, whereas a single-nucleotide polymorphism in FRZB resulting in an Arg324Gly substitution at the carboxyl terminus was associated with hip OA in the female probands (P = 0.04). This association was confirmed in an independent cohort of female hip cases (n = 338; P = 0.04). In addition, a haplotype coding for substitutions of two highly conserved arginine residues (Arg200Trp and Arg324Gly) in FRZB was a strong risk factor for primary hip OA, with an odds ratio of 4.1 (P = 0.004). FRZB encodes secreted frizzled-related protein 3, which is a soluble antagonist of wingless (wnt) signaling. Variant secreted frizzled-related protein 3 with the Arg324Gly substitution had diminished ability to antagonize wnt signaling in vitro. Hence, functional polymorphisms within FRZB confer susceptibility for hip OA in females and implicate the wnt signaling pathway in the pathogenesis of this disease.

Insulin-like growth factor I gene promoter polymorphism, collagen type II alpha1 (COL2A1) gene, and the prevalence of radiographic osteoarthritis: the Rotterdam Study

OBJECTIVE

To examine the role of an IGF-I gene promoter polymorphism in the prevalence of radiographic osteoarthritis (ROA), and study its interaction with the COL2A1 gene.

METHODS

Individuals genotyped for IGF-I (n = 1546) and COL2A1 gene polymorphisms (n = 808) were selected from a random sample (n = 1583) derived from the Rotterdam study. The presence of ROA was defined as a Kellgren score of 2 or more in at least one of four joints (knee, hip, hand, and spine). Genotype specific odds ratios (OR) were adjusted for age, sex, body mass index, and bone mineral density using logistic regression. Interaction with the COL2A1 genotype was tested.

RESULTS

Overall, no association was found between the IGF-I polymorphism and ROA. In subjects aged 65 years or younger (n = 971), the prevalence of ROA increased with the absence of the 192 base pair (bp) allele (p for trend = 0.03). Compared with homozygotes for the 192 bp allele, the prevalence of ROA was 1.4 times higher in heterozygotes (95% confidence interval, 1.0 to 1.8) and 1.9 times higher in non-carriers (1.1 to 3.3). There was evidence of interaction between the IGF-I and COL2A1 genes. Individuals with the risk genotype of both genes had an increased prevalence of ROA (OR 3.4 (1.1 to 10.7)). No effect was observed in subjects older than 65 years.

CONCLUSIONS

SUBJECTS

with genetically determined low IGF-I expression (non-carriers of the 192 bp allele) may be at increased risk of ROA before the age of 65 years. Furthermore, an interaction between the IGF-I and COL2A1 genes is suggested.

Genetics of osteoarthritis

Osteoarthritis (OA) is a major cause of morbidity, physical limitation, and health care use, including total joint arthroplasty. That OA has a genetic component has been known for some time, but only recently has formal study of this occurred. Twin studies, segregation analyses, linkage analyses, and candidate gene association studies have generated important information about inheritance patterns and the location in the genome of potentially causative mutations. Results across studies are not always concordant, however; this is likely the result of variations in study populations, disease definitions, evaluation of control subjects, and statistical analysis. Although the genetics of OA is complex and not completely understood, there is cause for optimism as rapidly improving technologies make the quest for the genes responsible for OA increasingly within reach. Family history of OA and joint replacement for OA should be assessed in the context of other potentially modifiable risk factors to attempt to alter patient outcome.

Diagnostic classification and orthopaedic physical therapy practice: what we can learn from medicine

Concepts of diagnosis and classification have a long history in medicine, while formal schemes of diagnostic classification in physical therapy are relatively new. Basic differences exist between medicine and physical therapy in the phenomena which are diagnosed and classified. However, similarities in the diagnostic and classification process provide an opportunity to learn from medicine as the process now evolves in physical therapy. This paper provides a brief history of the development of the concept of diagnostic classification in medicine and physical therapy. Difficulties associated with the process are described. Knowledge of these difficulties is used to analyze some of the evolving concepts of diagnostic classification in physical therapy, especially those related to orthopaedic physical therapy practice.

Finer linkage mapping of primary osteoarthritis susceptibility loci on chromosomes 4 and 16 in families with affected women

OBJECTIVE

To more finely linkage-map primary osteoarthritis (OA) susceptibility loci on chromosomes 4 and 16.

METHODS

Two hundred eighteen families, each with 2 or more women concordant for primary OA (ascertained by total hip replacement [THR] or total knee replacement), were genotyped using highly polymorphic microsatellite markers from chromosomes 4 and 16, at an average density of 1 marker every 4 cM. Two-point and multipoint linkage analyses were performed for all 218 families and for the 146 families from the 218 that included women concordant for THR (female-THR families).

RESULTS

A single region of linkage was identified on chromosome 4q, with a maximum multipoint logarithm of odds (LOD) score (MLS) of 3.1 in the 146 female-THR families. This locus was centered 79 cM from the 4p telomere and had a 1-LOD support interval of 4 cM. Two regions of linkage were identified on chromosome 16, the first on 16p with an MLS of 1.7 in the female-THR families and the second on 16q with an MLS of 1.9 in all 218 families. The first locus was centered 46 cM and the second 89 cM from the p-telomere. The 1-LOD support intervals were 12 cM and 10 cM, respectively.

CONCLUSION

Finer linkage mapping using a high density of microsatellite markers has narrowed female OA susceptibility loci on chromosomes 4 and 16. The regions have been narrowed sufficiently for association analysis.

Risk factors for osteoarthritis: genetics

Although the multifactorial nature of osteoarthritis (OA) is well recognized, genetic factors have been found to be strong determinants of the disease. Evidence of a genetic influence of OA comes from a number of sources, including epidemiological studies of family history and family clustering, twin studies, and exploration of rare genetic disorders. Classic twin studies have shown that the influence of genetic factors is between 39% and 65% in radiographic OA of the hand and knee in women, about 60% in OA of the hip, and about 70% in OA of the spine. Taken together, these estimates suggest a heritability of OA of 50% or more, indicating that half the variation in susceptibility to disease in the population is explained by genetic factors. Studies have implicated linkages to OA on chromosomes 2q, 9q, 11q, and 16p, among others. Genes implicated in association studies include VDR, AGC1, IGF-1, ER alpha, TGF beta, CRTM (cartilage matrix protein), CRTL (cartilage link protein), and collagen II, IX, and XI. Genes may operate differently in the two sexes, at different body sites, and on different disease features within body sites. OA is a complex disease, and understanding its complexity should help us find the genes and new pathways and drug targets.

Association of the interleukin-1 gene cluster with radiographic signs of osteoarthritis of the hip

OBJECTIVE

To study the role of the interleukin-1 beta gene (IL1B) and the IL-1 receptor antagonist gene (IL1RN) in relation to the occurrence of radiographic osteoarthritis (ROA) in the hip, knee, and hand and disc degeneration of the spine.

METHODS

The study population consisted of a random sample of 886 subjects (ages 55-65 years) from a population-based cohort (the Rotterdam study). Two polymorphisms within IL1B (3953C>T and -511C>T) and one within IL1RN (the variable-number tandem repeat [VNTR]) were analyzed and used in an association study of the occurrence of ROA. Haplotyping and simultaneous logistic regression analysis were performed to investigate whether the associations observed were independent.

RESULTS

Associations with a predisposition for hip ROA were observed for heterozygous and homozygous carriers of the rare IL1B allele -511T (crude odds ratio [OR] 1.8, 95% confidence interval [95% CI] 1.0-3.4 and OR 2.9, 95% CI 1.4-6.3, respectively) and of the IL1RN VNTR allele 2 (crude OR 2.0, 95% CI 1.1-3.4 and OR 3.3, 95% CI 1.4-7.8, respectively). An additive effect was observed for carriers of risk alleles of both polymorphisms, with a significant linear-by-linear association (P = 0.00022).

CONCLUSION

Our findings suggest that the IL-1 gene cluster polymorphisms may play a significant role in the pathogenesis of OA of the hip.

Epidemiology of osteoarthritis: prevalence, risk factors and functional impact

Osteoarthritis (OA), the most common form of arthritis, is a major contributor to functional impairment and reduced independence in older adults. OA of the hip and knee are two of the most important causes of pain and physical disability in community-dwelling adults. Symptomatic hand OA is a common disease among the elderly, and impairs hand function, this impairment being largely mediated by pain. Like other chronic diseases, the etiology of OA is multifactorial, and several local and systemic risk factors have been identified. Differences in the prevalence of OA may be attributable to both genetic and life-style factors. Disease definition may be based upon clinical or radiographic criteria, although case definition should rely on radiographic features for epidemiological studies. This review focuses on the functional impact of the disease, describes geographic differences in prevalence rates, discusses disease definition criteria, and summarizes the most common risk factors, including age, associated with the risk of OA.

Search for linkage between hand osteoarthritis and 11q 12-13 chromosomal segment

OBJECTIVE

The aims of the present study were: (1) to evaluate the extent and mode of inheritance of hand osteoarthritis by using a large sample of ethnically homogeneous pedigrees of Caucasian origin; (2) to examine whether the synthetic measure of osteoarthritis according to Kellgren and Lawrence (K-L) and the more specific measure, namely, the extent of osteophytes development, have a similar putative genetic determination and pattern of biological inheritance and (3) to test the hypothesis that hand osteoarthritis dependent phenotypes are linked to the 11q 12-13 chromosomal region.

METHODS

The population of the present study comprised 1190 Chuvashians (Russian Federation) belonging to 295 nuclear families. Segregation analysis was carried out on a total sample. Sub-sample of 571 individuals was used to conduct Transmission/disequilibrium test (TDT) and model-based linkage analysis.

RESULTS

Adjusted for age, sex and other covariates, both OA phenotypes showed significant familial aggregation. The model fitting analysis strongly supported the hypothesis of a major gene effect on study traits. The inferred major gene explained about 52% of the osteophyte score (OPS) and 49% of the K-L score variation adjusted for confounding variables. The series of model-based linkage analyses and TDTs provided inconclusive evidence on possible linkage of both phenotypes to the 11q 12-13 chromosomal region.

CONCLUSIONS

We support the hypothesis of a major gene effect in heritability of hand osteoarthritis in both phenotypes. Despite the fact that some DNA markers showed statistically significant association to studied primary phenotypes, we find only weak evidence of linkage disequilibrium between hand osteoarthritis and the proximal part of the 11q 12-13 chromosomal segment (D11S1983 for K-L score and D11S1313 for OPS). The subject, however, a merit requires further investigation.