Predisposition to familial osteoarthrosis linked to type II collagen gene

Molecular mechanisms and genetic factors contributing to the developmental dysplasia of the hip

The most prevalent hip disease in neonates is developmental dysplasia of the hip (DDH). A timely and accurate diagnosis is required to provide the most effective treatment for pediatric patients with DDH. Heredity and gene variation have been the subject of increased attention and research worldwide as one of the factors contributing to the pathogenesis of DDH. Genome-wide association studies (GWAS), genome-wide linkage analyses (GWLA), and exome sequencing (ES) have identified variants in numerous genes and single-nucleotide polymorphisms (SNPs) as being associated with susceptibility to DDH in sporadic and DDH family patients. Furthermore, the DDH phenotype can be observed in animal models that exhibit susceptibility genes or loci, including variants in CX3CR1, KANSL1, and GDF5. The dentification of noncoding RNAs and de novo gene variants in patients with DDH-related syndrome has enhanced our understanding of the genes implicated in DDH. This article reviews the most recent molecular mechanisms and genetic factors that contribute to DDH.

Osteoarthritis

The clinical appearance and radiological pattern of osteoarthritis have been identified in the skeletons of dinosaurs some 50-70 million years old, and in Egyptian mummies, and in ancient skeletons in England. Osteoarthritis patterns of joint involvement, often referred to as primary osteoarthritis, can be seen in the hands, spinal facet joints, hips, knees and feet, but can also be termed secondary osteoarthritis when seen in any joint that has had trauma, sepsis, surgery or metabolic insult. The prevalence of osteoarthritis increases with age. The histology and pathophysiology both demonstrate an inflammatory process. While there have been studies of genetic predisposition, the basic cause of primary osteoarthritis has not been determined.

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

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

Profiling and targeting connective tissue remodeling in autoimmunity - A novel paradigm for diagnosing and treating chronic diseases

Connective tissue (ConT) remodeling is an essential process in tissue regeneration, where a balanced replacement of old tissue by new tissue occurs. This balance is disturbed in chronic diseases, often autoimmune diseases, usually resulting in the buld up of fibrosis and a gradual loss of organ function. During progression of liver, lung, skin, heart, joint, skeletal and kidney diseasesboth ConT formation and degradation are elevated, which is tightly linked to immune cell activation and a loss of specific cell types and extracellular matrix (ECM) structures that are required for normal organ function. Here, we address the balance of key general and organ specific components of the ECM during homeostasis and in disease, with a focus on collagens, which are emerging as both structural and signaling molecules harbouring neoepitopes and autoantigens that are released during ConT remodeling. Specific collagen molecular signatures of ConT remodeling are linked to disease activity and stage, and to prognosis across different organs. These signatures accompany and further drive disease progression, and often become detectable before clinical disease manifestation (illness). Recent advances allow to quantify and define the nature of ConT remodeling via blood-based assays that measure the levels of well-defined collagen fragments, reflecting different facets of ConT formation and degradation, and associated immunological processes. These novel serum assays are becoming important tools of precision medicine, to detect various chronic and autoimmune diseases before their clinical manifestation, and to non-invasively monitor the efficacy of a broad range of pharmacological interventions.

Superolateral Hoffa's Fat Pad Edema and Trochlear Sulcal Angle Are Associated With Isolated Medial Patellofemoral Compartment Osteoarthritis

PURPOSE

To evaluate whether mediopatellar plica and knee morphometric measurements obtained from magnetic resonance imaging (MRI) studies are associated with isolated medial patellofemoral osteoarthritis in young adults.

METHODS

MRI studies from 60 patients with isolated medial patellofemoral osteoarthritis and 90 control patients with normal knee MRI studies were reviewed. The presence of mediopatellar plica, the presence of edema in the superolateral aspect of Hoffa's fat pad and suprapatellar fat pad, quadriceps and patellar tendinosis, and axial and sagittal alignment of the patellar and trochlear morphology were assessed using MRI. The relationship between mediopatellar plica, alignment, or morphology and the presence of isolated medial patellofemoral osteoarthritis was evaluated using logistic regression.

RESULTS

Superolateral Hoffa's fat pad edema (odds ratio [OR] = 3.4, P = .009) and decreased trochlear sulcal angle (OR = 0.95, P = .045) were associated with increased odds of isolated medial patellofemoral osteoarthritis. Decreased lateral patellar tilt (OR = 0.93, P = .087) and patellar tendinosis (OR = 4.13, P = .103) trended toward being associated with increased odds of isolated medial patellofemoral osteoarthritis but were not statistically significant. No significant association was seen between the presence of mediopatellar plica and medial patellofemoral osteoarthritis (OR = 0.95, P = .353).

CONCLUSIONS

Medial patellofemoral osteoarthritis is associated with trochlear morphology and patellar alignment but not with mediopatellar plica.

Prevalence of knee osteoarthritis in former athletes: a systematic review with meta-analysis

BACKGROUND

Prevalence of knee osteoarthritis in former athletes is still unclear.

OBJECTIVE

To investigate prevalence of knee osteoarthritis in former athletes. Moreover, the secondary aim was to investigate whether poor methodological quality of included studies, different diagnosis criteria for knee osteoarthritis, different sports modality or sex impact on overall estimated prevalence of knee osteoarthritis in former athletes.

METHODS

Searches on MEDLINE, EMBASE, AMED, SPORTDiscus and CINAHL from the earliest record to February 2018 and hand-searching identified studies investigating prevalence of knee osteoarthritis in former athletes. Meta-analysis was conducted and the GRADE system summarized strength of the current recommendations. Sensitivity analyses investigated whether methodological quality, diagnostic criteria, type of sports or sex impacted on the overall estimated prevalence in former athletes. This review was registered at PROSPERO (CRD42016050903).

RESULTS

Fifteen studies were included and pooling of 3100 participants estimated overall prevalence of knee osteoarthritis in former athletes of 30.0% (95% CI: 20.0 to 40.0%). The strength of the current recommendations was low-quality. Sensitivity analyses suggested that different diagnostic criteria for knee osteoarthritis and type of sports may impact on the overall estimated prevalence.

CONCLUSIONS

Prevalence of knee osteoarthritis in former athletes was 30.0%. Researchers, clinicians and policymakers should be careful about potential prevalence differences among type of sports and diagnostic criteria. Current low-quality evidence shows that future high-quality studies are likely to impact on the estimated prevalence.

The good and the bad collagens of fibrosis - Their role in signaling and organ function

Usually the dense extracellular structure in fibrotic tissues is described as extracellular matrix (ECM) or simply as collagen. However, fibrosis is not just fibrosis, which is already exemplified by the variant morphological characteristics of fibrosis due to viral versus cholestatic, autoimmune or toxic liver injury, with reticular, chicken wire and bridging fibrosis. Importantly, the overall composition of the ECM, especially the relative amounts of the many types of collagens, which represent the most abundant ECM molecules and which centrally modulate cellular functions and physiological processes, changes dramatically during fibrosis progression. We hypothesize that there are good and bad collagens in fibrosis and that a change of location alone may change the function from good to bad. Whereas basement membrane collagen type IV anchors epithelial and other cells in a polarized manner, the interstitial fibroblast collagens type I and III do not provide directional information. In addition, feedback loops from biologically active degradation products of some collagens are examples of the importance of having the right collagen at the right place and at the right time controlling cell function, proliferation, matrix production and fate. Examples are the interstitial collagen type VI and basement membrane collagen type XVIII. Their carboxyterminal propeptides serve as an adipose tissue hormone, endotrophin, and as a regulator of angiogenesis, endostatin, respectively. We provide an overview of the 28 known collagen types and propose that the molecular composition of the ECM in fibrosis needs careful attention to assess its impact on organ function and its potential to progress or reverse. Consequently, to adequately assess fibrosis and to design optimal antifibrotic therapies, we need to dissect the molecular entity of fibrosis for the molecular composition and spatial distribution of collagens and the associated ECM.

Distribution of Risk Factors in Male and Female Primary Health Care Patients with Osteoarthritis in Albania

Aim:

We aimed to describe the distribution of the main risk factors among primary health care users diagnosed with osteoarthritis in Albania, a post-communist country in South Eastern Europe.

Methods:

Our study involved all individuals who were diagnosed with osteoarthritis over a two-year period (January 2013 – December 2014) in several primary health care centers in Tirana, the Albanian capital. On the whole, during this two-year period, 1179 adult individuals were diagnosed with osteoarthritis (521 men aged 60.1±10.6 years and 658 women aged 58.1±9.6 years). According to the criteria of the American College of Rheumatology, the diagnosis of osteoarthritis was based on the history of the disease, physical examination, laboratory findings and radiological findings. Binary logistic regression was used to assess the sex-differences regarding the major risk factors among individuals diagnosed with osteoarthritis.

Results:

In multivariable-adjusted logistic regression models, female gender was inversely associated with smoking (OR=0.39, 95%CI=0.27-0.56), alcohol intake (OR=0.08, 95%CI=0.06-0.10), overweight but not obesity (OR=0.65, 95%CI=0.46-0.91 and OR=0.74, 95%CI=0.46-1.18, respectively), weight lifting (OR=0.38, 95%CI=0.22-0.66) and heavy physical exercise (OR=0.69, 95%CI=0.46-1.03). Conversely, female gender was positively related to genetic factors (OR=2.17, 95%CI=1.55-3.04) and preexisting inflammatory diseases (OR=1.53, 95%CI=0.93-2.53).

Conclusion:

This study offers useful evidence about the distribution of the main risk factors for osteoarthritis in adult individuals diagnosed with osteoarthritis in Albania. This information may support health professionals and decision-makers in Albania for evidence-based health planning and policy formulation in order to control the toll of osteoarthritis in this transitional society.

Novel insights into the function and dynamics of extracellular matrix in liver fibrosis

Emerging evidence suggests that altered components and posttranslational modifications of proteins in the extracellular matrix (ECM) may both initiate and drive disease progression. The ECM is a complex grid consisting of multiple proteins, most of which play a vital role in containing the essential information needed for maintenance of a sophisticated structure anchoring the cells and sustaining normal function of tissues. Therefore, the matrix itself may be considered as a paracrine/endocrine entity, with more complex functions than previously appreciated. The aims of this review are to 1) explore key structural and functional components of the ECM as exemplified by monogenetic disorders leading to severe pathologies, 2) discuss selected pathological posttranslational modifications of ECM proteins resulting in altered functional (signaling) properties from the original structural proteins, and 3) discuss how these findings support the novel concept that an increasing number of components of the ECM harbor signaling functions that can modulate fibrotic liver disease. The ECM entails functions in addition to anchoring cells and modulating their migratory behavior. Key ECM components and their posttranslational modifications often harbor multiple domains with different signaling potential, in particular when modified during inflammation or wound healing. This signaling by the ECM should be considered a paracrine/endocrine function, as it affects cell phenotype, function, fate, and finally tissue homeostasis. These properties should be exploited to establish novel biochemical markers and antifibrotic treatment strategies for liver fibrosis as well as other fibrotic 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.

Osteoarthritis: detection, pathophysiology, and current/future treatment strategies

Osteoarthritis (OA) is a disease of the joint, and age is the major risk factor for its development. Clinical manifestation of OA includes joint pain, stiffness, and loss of mobility. Currently, no pharmacological treatments are available to treat this specific joint disease; only symptom-modifying drugs are available. Improvement in imaging technology, identification of biomarkers, and increased understanding of the molecular basis of OA will aid in detecting the early stages of disease. Yet the development of interventional strategies remains elusive and will be critical for effective prevention of OA-associated joint destruction. The potential of cell-based therapies may be applicable in improving joint function in mild to more advanced cases of OA. Ongoing studies to understand the basis of this disease will eventually lead to prevention and treatment strategies and will also be a key in reducing the social and economic burden of this disease. Nurses are advised to provide an integrative approach of disease assessment and management in OA patients' care with a focus on education and implementation. Knowledge and understanding of OA and how this affects the individual patient form the basis for such an integrative approach to all-round patient care and disease management.

Collagen expression in various degenerative meniscal changes: an immunohistological study

PURPOSE. To examine changes in acid mucopolysaccharides and collagen expression during meniscal degeneration, tearing, and repair, using menisci excised from knee joint surgeries. METHODS. Menisci excised from 23 patients aged 15 to 80 years who underwent meniscal surgery for flap and bucket handle tears (n=11) and total knee arthroplasty (TKA) for osteoarthritis (n=12) were examined histologically. Staining images were converted to greyscale images to measure the mean grey levels, which indicated densitometry. Comparisons were made between acutely injured menisci and menisci with and without degeneration (from patients with osteoarthritis) in terms of acid mucopolysaccharides, collagen types I, II, and III expression. RESULTS. In menisci with no degeneration, acid mucopolysaccharides, collagen types I and II were expressed throughout the entire meniscus except for the circulating area. Collagen type III was intensely expressed at the exterior peripheral border and on the surface. During progression of meniscal degeneration, the expression of acid mucopolysaccharides increased, and the expression of collagen types I, II, and III decreased. In acutely injured menisci, collagen types II and III disappeared first, followed by collagen type I, resulting in the abrogation of fibre construction. CONCLUSION. In normal menisci, acid mucopolysaccharides and collagen types I, II, and III were well-balanced, and meniscal function was maintained. When the limits of repair were exceeded, the meniscus tissue deteriorated owing to the disappearance of collagen types II and III and a decrease in collagen type I, resulting in the abrogation of meniscus fabric construction.

The age-related changes in cartilage and osteoarthritis

Osteoarthritis (OA) is closely associated with aging, but its underlying mechanism is unclear. Recent publications were reviewed to elucidate the connection between aging and OA. With increasing OA incidence, more senior people are facing heavy financial and social burdens. Age-related OA pathogenesis is not well understood. Recently, it has been realized that age-related changes in other tissues besides articular cartilage may also contribute to OA development. Many factors including senescence-related secretory phenotypes, chondrocytes' low reactivity to growth factors, mitochondrial dysfunction and oxidative stress, and abnormal accumulation of advanced glycation end products (AGEs) may all play key roles in the pathogenesis of age-related OA. Lately, epigenetic regulation of gene expression was recognized for its impact on age-related OA pathogenesis. Up to now, few studies have been reported about the role of miRNA and long-noncoding RNA (lncRNA) in age-related OA. Research focusing on this area may provide valuable insights into OA pathogenesis. OA-induced financial and social burdens have become an increasingly severe threat to older population. Age-related changes in noncartilage tissue should be incorporated in the understanding of OA development. Growing attention on oxidative stress and epigenetics will provide more important clues for the better understanding of the age-related OA.

Epidemiology of osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis in the United States and is a leading cause of disability. It is typically defined in epidemiologic studies by radiographic findings and consideration of symptoms. Its incidence and prevalence are rising, likely related to the aging of the population and increasing obesity. Risk factors for OA include numerous person-level factors, such as age, sex, obesity, and genetics, as well as joint-specific factors that are likely reflective of abnormal loading of the joints. In studying OA, several methodologic challenges exist that can hamper our ability to identify pertinent relationships.

Extracellular matrix remodeling: the common denominator in connective tissue diseases. Possibilities for evaluation and current understanding of the matrix as more than a passive architecture, but a key player in tissue failure

Increased attention is paid to the structural components of tissues. These components are mostly collagens and various proteoglycans. Emerging evidence suggests that altered components and noncoded modifications of the matrix may be both initiators and drivers of disease, exemplified by excessive tissue remodeling leading to tissue stiffness, as well as by changes in the signaling potential of both intact matrix and fragments thereof. Although tissue structure until recently was viewed as a simple architecture anchoring cells and proteins, this complex grid may contain essential information enabling the maintenance of the structure and normal functioning of tissue. The aims of this review are to (1) discuss the structural components of the matrix and the relevance of their mutations to the pathology of diseases such as fibrosis and cancer, (2) introduce the possibility that post-translational modifications (PTMs), such as protease cleavage, citrullination, cross-linking, nitrosylation, glycosylation, and isomerization, generated during pathology, may be unique, disease-specific biochemical markers, (3) list and review the range of simple enzyme-linked immunosorbent assays (ELISAs) that have been developed for assessing the extracellular matrix (ECM) and detecting abnormal ECM remodeling, and (4) discuss whether some PTMs are the cause or consequence of disease. New evidence clearly suggests that the ECM at some point in the pathogenesis becomes a driver of disease. These pathological modified ECM proteins may allow insights into complicated pathologies in which the end stage is excessive tissue remodeling, and provide unique and more pathology-specific biochemical markers.

Epidemiology of osteoarthritis

Osteoarthritis (OA) is the most common joint disorder in the United States. Symptomatic knee OA occurs in 10% men and 13% in women aged 60 years or older. The number of people affected with symptomatic OA is likely to increase due to the aging of the population and the obesity epidemic. OA has a multifactorial etiology, and can be considered the product of an interplay between systemic and local factors. Old age, female gender, overweight and obesity, knee injury, repetitive use of joints, bone density, muscle weakness, and joint laxity all play roles in the development of joint OA, particularly in the weight-bearing joints. Modifying these factors may reduce the risk of OA and prevent subsequent pain and disability.

Topographic Patterns of Cartilage Lesions in Knee Osteoarthritis

OBJECTIVE: Treatments for articular cartilage lesions could benefit from characterization of lesion patterns and their progression to end-stage osteoarthritis. The objective of this study was to identify, quantitatively, topographic patterns of cartilage lesions in the human knee. DESIGN: Photographs were taken of 127 unilateral distal femora (from 109 cadavers and 18 arthroplasty remnants) with full-thickness cartilage lesions. Using digital image analysis, the lesions were localized and normalized lesion size was determined for the patellofemoral groove (PFG) and the lateral and medial femoral condyles (LFC, MFC). Samples were classified into patterns using cluster analysis of the lesion size at each compartment. For each pattern, maps showing the extent and frequency of lesions were created. RESULTS: Four main patterns (a-d) were identified (each p<0.001), with the lesion size varying from small (a) to large in distinct regions (b-d). Pattern b had a predominant lesion (23% area) in the MFC, and smaller (<3%) lesions elsewhere. Pattern c had predominant lesions in the LFC (19%) and MFC (10%). Pattern d had a predominant lesion in the PFG (15%) and smaller lesions in the MFC (6%) and LFC (2%). The sub-patterns of a (a1, a2, a3) had relatively small lesions, with similarity between a2 and b, and a3 and d. CONCLUSION: The present methods facilitated quantitative identification of distinct topographic patterns of full-thickness cartilage lesions, based on lesion size and location. These results have implications for stratifying OA patients using precise quantitative methods and, with additional longitudinal data, targeting cartilage treatments.

Epidemiology of osteoarthritis

Evolving definitions of osteoarthritis and improvements in risk factor measurement that use advanced imaging, systemic and local biomarkers, and improved methods for measuring symptoms and their impact can help elucidate mechanisms and identify potential areas for intervention or prevention.

Structural parameters and mechanical strength of cancellous bone in the femoral head in osteoarthritis do not depend on age

For normal bone, aging has been associated with a decrease of both density and failure strength, and with the development of pathologies such as osteoporosis. Conversely, it has been reported that another common disease, osteoarthritis, may alter these age-related changes in cancellous bone, suggesting that it may have a protective role against osteoporosis and the correspondent fracture risk. It was reported that in the principal compressive region of the femoral head in osteoarthritis the bone density does not depend on age. However, it is not clear if this independence on age of the cancellous bone density corresponds also to a reduced dependence on age of the strength to failure. The present work examined cancellous bone from the principal compressive region of the femoral head of 37 patients having severe osteoarthritis. The aim was (1) to investigate the dependence on age of both the structural parameters and the ultimate stress and (2) to investigate the relationships between the ultimate stress and the structural parameters. Using X-ray microcomputed tomography, three-dimensional structural parameters, such as bone volume fraction, direct trabecular thickness and structure model index were calculated. Then the specimens were compressed to failure to determine the ultimate stress. It was found that none of the investigated structural parameters did depend on age, and also the ultimate stress did not depend on age (p>0.05 for all regressions on age). In addition, the ultimate stress was significantly correlated with the structural parameters, primary with the minimum bone volume fraction and the average bone volume fraction (R(2)=0.95 and R(2)=0.84, respectively). These findings show that severe osteoarthritis or a related factor may change the age dependences of both the structural parameters and the mechanical properties usually reported for normal cancellous bone. These results suggest for this pathology to have a protective role against the age-related decrease in density, the age-related deterioration of the microarchitecture and the age-related decrease of the failure strength for the cancellous bone in the principal compressive region of the human femoral head.

New Developments in Osteoarthritis

Osteoarthritis (OA) has been a frustrating disease for both the patient and the physician. Its current impact on society is tremendous and rivals that of ischemic heart disease in many regards. As the baby boomers reach late adulthood and the obesity epidemic rages on, OA will assume an even greater impact on society. The current OA armamentarium only reduces pain and perhaps improves function, but has no impact on the disease incidence or progression. Thus, the challenge for researchers to develop disease-modifying OA drugs becomes an issue of paramount importance. Several advances in the understanding of OA pathophysiology have provided a glimpse of optimism that disease modification is a real possibility.

New developments in osteoarthritis

Osteoarthritis (OA) has been a frustrating disease for both the patient and the physician. Its current impact on society is tremendous, and rivals that of ischemic heart disease in many regards. As the baby boomers reach late adulthood and the obesity epidemic rages on, OA will assume an even greater impact on society. The current OA armamentarium only reduces pain and perhaps improves function, and has no impact on the disease incidence or progression. Thus, the challenge for researchers to develop disease-modifying OA drugs becomes an issue of paramount importance. Several advances in our understanding of OA pathophysiology have provided a glimpse of optimism that disease modification is a real possibility. Appreciation of the local factors involved in OA progression as well as the inflammatory nature in a subset of patients has led to different treatment strategies based on predominant phenotype. Further understanding of the initiating events in cartilage destruction, the relationship between the different pathologic influences, and the role of the chondrocyte in maintaining extracellular matrix homeostasis will be necessary to reveal potential targets of therapy.

The role of sequence variations within the genes encoding collagen II, IX and XI in non-syndromic, early-onset osteoarthritis

OBJECTIVE

We sought to determine whether sequence variations in cartilage collagen genes are associated with primary, early-onset osteoarthritis (OA).

METHODS

The cartilage collagen genes, COL2A1, COL9A1, COL9A2, COL9A3, COL11A1 and COL11A2, were screened for sequence variations in 72 Finnish probands and one US family with primary early-onset hip and/or knee OA. In addition, allelic association studies were performed using six to 12 common polymorphisms from each gene by genotyping 72 OA patients and 103 controls.

RESULTS

Altogether 239 sequence variations were found, of which 16 were not present in the controls. Seven of the unique variations, four in COL11A1, two in COL11A2 and one in COL2A1, were studied further, because they resulted in the substitution of conserved amino acids or were predicted to affect mRNA splicing. Co-segregation of a sequence variation and the phenotype was found in all four families available for study. Association analysis failed to identify any common predisposing alleles.

CONCLUSIONS

Early-onset OA demonstrates locus and allelic heterogeneity since the identified variations were in three different collagen genes and each of the six probands had a different mutation. It is also possible that some OA cases represent the mild end of the chondrodysplasia phenotypic spectrum. The major susceptibility alleles in this form of OA, however, remain to be identified.

A human COL2A1 gene with an Arg519Cys mutation causes osteochondrodysplasia in transgenic mice

OBJECTIVE

An arginine-to-cysteine substitution at position 519 of the COL2A1 gene causes early generalized osteoarthritis with mild chondrodysplasia in humans. In this study, a human COL2A1 gene with the same mutation was introduced into a murine genome having 1 or no alleles of the murine Col2a1 gene, and the skeletal phenotypes of the transgenic mice were compared with those of control mice.

METHODS

Mice with 1 allele of the normal murine Col2a1 gene and 1 allele of the mutated human COL2A1 gene (n = 10), those with no murine Col2a1 gene and 2 alleles of the mutated human COL2A1 gene (n = 13), those with no murine Col2a1 gene and only 1 allele of the mutated COL2A1 gene (n = 9), and normal control mice (n = 11) were studied for skeletal abnormalities, using radiographic imaging and light microscopic analyses of histologic sections. The collagen network of cartilage was also investigated with transmission electron microscopy.

RESULTS

At 2 months of age, all transgenic mice had dysplastic changes in their long bones, flattened vertebral bodies, and osteoarthritic changes in their joints. The intervertebral discs of the transgenic animals were degenerated, and their histologic structure was disturbed. The changes were more severe in mice with no murine Col2a1 allele.

CONCLUSION

The human COL2A1 gene with the Arg519Cys mutation causes osteochondrodysplasia in mice, as it does in humans.

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 two gene polymorphisms with osteoarthritis secondary to hip dysplasia

Two adjacent genes on the 12q chromosome, the alpha 1 chain of Type II collagen, and the vitamin D receptor, have been considered potentially related to the pathophysiology of osteoarthritis. Two restriction fragment length polymorphisms were detected in 50 healthy donors and in 143 patients having a total hip replacement for idiopathic osteoarthritis or osteoarthritis secondary to developmental hip dysplasia. The polymorphic sites of Type II collagen and vitamin D receptor were amplified by polymerase chain reaction, and the products were digested with PvuII and BsmI restriction enzymes, respectively. The results showed that medical history and clinical characteristics, including gender, familial history of osteoarthritis, other hip prosthesis, and how early in life implantation was done did not seem to be connected to a particular genotype. Significant results were found by assessing the two groups of diseases that led to hip arthroplasty, suggesting a possible link between some haplotypes and the risk of severe osteoarthritis in patients with hip dysplasia. These results indicate that genetic markers could contribute to the understanding of the natural history of this disease.

Genome studies and linkage in primary osteoarthritis

Genetic epidemiologic studies have demonstrated that primary OA has a major genetic component that segregates in families in a complex manner. Some of these studies suggest that genetic susceptibility may be more relevant to female OA than to male OA and that genes may have a greater role in OA development and progression at certain joint groups compared with others. These observations are not universal, however, and discrepancies between different studies may simply serve to highlight the complex nature of the transmittance of OA susceptibility. The numerous OA linkage studies that have now been performed have revealed a number of regions of the human genome that are likely to harbor genes predisposing to OA. Several of these regions, particularly those identified in genome-wide scans of ASPs, have relatively low LOD scores; as a result, their reliability must be questioned. Nevertheless, a few of these regions have already been linked in more than one study, and these linkages can be considered as more robust. Such confirmation is a prerequisite to finer linkage mapping, which should narrow the linkage intervals to a point at which comprehensive association analysis of DNA sequence variants can be undertaken.

Epidemiology of risk factors for osteoarthritis: systemic factors

Osteoarthritis (OA) appears to be a mechanically driven but chemically mediated disease process in which there is attempted (or aberrant) repair. Well established risk factors for OA include aging, obesity, gender, and, in selected subgroups, congenital anomalies. This review addresses less well established risk factors for OA that can impact joints through their effect on systemic metabolism rather than their contribution to local joint geometry and structure. These systemic risk factors include obesity; bone and bone density; nutrients, particularly those that function as antioxidants; and genetic factors. There is great opportunity for new prevention and intervention strategies as we expand our understanding of the role of these systemic risk factors.

Definition and epidemiology of osteoarthritis of the hand: a review

The hand is a common site of peripheral joint involvement in osteoarthritis (OA) and although often underestimated as a cause of disability, the effect on quality of life from limitations in performing activities of daily living such as dressing and feeding may be considerable. Hand OA may also be an important indicator of a systemic tendency to OA which may involve weight bearing joints, notably the hips and knees. (1) The definition of hand OA, particularly for epidemiological studies, has undergone reassessment and revision over the last few years. In this paper we examine the issues relating to this and consider the epidemiology of hand OA.

Practical approaches to determining disease-susceptible loci in multigenic autoimmune models

Linkage analysis using polymorphic DNA markers has paved the way toward the identification of genes responsible for rare recessive traits and for the susceptibility to certain tumors in humans. However, genetic susceptibility to common diseases, including systemic autoimmune diseases, is difficult to determine, hence has remained a challenging problem in the field of molecular genetics. Elucidation of multiple quantitative trait loci that predispose individuals to multi-phenotypic systemic autoimmune disease requires formidable research efforts, and there is a growing consensus that mouse models are required. This review provides a guide to methods that can be used in linkage studies of autoimmune mice. Mouse studies in relation to recent advances in bio-informatics are also discussed.

Genetic markers of osteoarticular disorders: facts and hopes

Osteoarthritis and osteoporosis are the two most common age-related chronic disorders of articular joints and skeleton, representing a major public health problem in most developed countries. Apart from being influenced by environmental factors, both disorders have a strong genetic component, and there is now considerable evidence from large population studies that these two disorders are inversely related. Thus, an accurate analysis of the genetic component of one of these two multifactorial diseases may provide data of interest for the other. However, the existence of confounding factors must always be borne in mind in interpreting the genetic analysis. In addition, each patient must be given an accurate clinical evaluation, including family history, history of drug treatments, lifestyle, and environment, in order to reduce the background bias. Here, we review the impact of recent work in molecular genetics suggesting that powerful molecular biology techniques will soon make possible both a rapid accumulation of data on the genetics of both disorders and the development of novel diagnostic, prognostic, and therapeutic approaches.

The inheritance of hip osteoarthritis in Iceland

OBJECTIVE

To assess, in a population-wide study in Iceland, the genetic contribution to hip osteoarthritis (OA) leading to total hip replacement (THR).

METHODS

Information from 2 population-based databases in Iceland was combined: a national registry of all THRs performed between 1972 and 1996, and a genealogy database of all available Icelandic genealogy records for the last 11 centuries. A genetic contribution to THR for OA was assessed by 1) identifying familial clusters of OA patients with THR, 2) applying the minimum founder test (MFT) to estimate the minimum number of ancestors ("founders") that would account for the genealogy of all 2,713 patients with THR for OA, compared with the average number of founders for control lists, 3) calculating an average pairwise kinship coefficient (KC) for the patient list and control lists, and 4) estimating the relative risk (RR) for THR among relatives of OA patients who have undergone the procedure. One thousand matched control lists, each the same size as the patient list, were created using the genealogy database.

RESULTS

A large number of familial clusters of patients with THR for OA were identified. The MFT showed that OA patients descended from fewer founders than did subjects in the control groups (P < 0.001). The average pairwise KC among patients with OA was greater than in the control population (P < 0.001). The RR for THR among siblings of OA patients was 3.05 (95% confidence interval 2.52-3.10).

CONCLUSION

This population-based study shows that Icelandic patients with hip replacement for OA are significantly more related to each other than are matched controls drawn from the Icelandic population. These findings support a significant genetic contribution to a common form of OA and encourage the search for genes conferring an increased susceptibility to OA.

Osteoarthritis-like lesions in transgenic mice harboring a small deletion mutation in type II collagen gene

OBJECTIVE

The present study was conducted on transgenic Del1 (+/-) mice harboring six copies of a transgene with small deletion mutation engineered into mouse type II collagen gene. Incorporation of transgene into mouse genome was predicted to cause reduced mechanical strength of articular cartilage with deposition of structurally inferior collagen network and consequently to predispose the animal to early-onset joint degeneration.

DESIGN

Progression of degenerative chances in the knee joints of Del1 (+/-) and control mice was followed by macroscopic and histologic analyses at 3-5 month intervals between 3 and 22 months of age. Expression and distribution of type II collagen was studied with Northern hybridization, RNase protection assay and immunohistochemistry.

RESULTS

Articular cartilage degeneration began with superficial fibrillation at the age of 3 months in Del1 (+/-) mice. These changes coincided with a significant reduction in the expression of both endogenous and transgene-derived type II collagen mRNA. The defects gradually progressed into erosions penetrating the articular cartilage, bony sclerosis, degeneration of menisci, mineralization of various joint structures, cyst formation and exposure of subchondral bone. Nontransgenic controls also developed osteoarthritic lesions, but these appeared significantly later and were less severe. Increased transcription of type IIA procollagen mRNA, typical for chondroprogenitor cells and cartilage repair was also observed at six months in Del1 (+/-) mice.

CONCLUSION

These findings suggest that the impact of truncated type II collagen transgene, together with maturation-related reduction in type II collagen production significantly contribute to the early-onset degeneration of knee joints in Del1 (+/-) mice. These mice with osteoarthritis-like phenotype should provide a useful model for studies on the early pathogenic mechanisms involved in articular cartilage degeneration.

What can we do about osteoarthritis?

Osteoarthritis is complex in genetics, pathogenesis, monitoring and treatment. Current treatment of osteoarthritis does not influence progression. Much could be gained by more effective 'low-tech-low-cost' treatment. However, many patients have rapidly progressive disease, multiple joint involvement, and severe disease. We need to clarify the genetics of osteoarthritis, identify those at risk for progression and severe disease, and identify molecular processes critical for joint survival and failure. Will saving the cartilage improve patient pain and function? Effective outcome measures are needed to accelerate testing of new treatments. Further improvement is needed in joint implant technology to decrease costs, wear and loosening.

Vitamin D receptor gene polymorphisms and osteoarthritis of the hand, hip, and knee: acase-control study in Japan

OBJECTIVE

To investigate the association between vitamin D receptor (VDR) gene polymorphisms andJapanese female patients with osteoarthritis (OA) of the hand, hip, and knee.

METHODS

BsmI,ApaI, andTaqI restriction fragment length polymorphisms (RFLPs) of the VDR gene were analysed in 270Japanese female patients with radiographic OA of the hand, hip, tibiofemoral (TF) joint, andpatellofemoral (PF) joint, as well as in female controls.

RESULTS

There was no significant association between the VDR gene RFLPs and OA of the hand, hip, TFjoint, PF joint, or polyarticular involvement. The previously detected preventive genotype of the VDRgene was uncommon in our test population.

CONCLUSION

The relative importance of VDR gene polymorphism in the development of OA may vary betweenethnic groups.

Association between an aggrecan gene polymorphism and lumbar disc degeneration

STUDY DESIGN

A case-control study using magnetic resonance imaging findings and a polymerase chain reaction assay to investigate the association between aggrecan gene polymorphism and lumbar disc degeneration.

OBJECTIVE

To analyze whether the aggrecan gene polymorphism is related to lumbar disc disease in young women.

SUMMARY OF BACKGROUND DATA

It has been suggested that a genetic factor or familial predisposition contributes to the development of lumbar disc herniation. However, the precise genetic component related to disc disease remains unclear. Recently, a polymorphism has been identified in the region of the human aggrecan gene. The expressed variable numbers of tandem repeat polymorphism occur in the highly conserved repeat region.

METHODS

The participants were 64 young women with or without low back problems. Magnetic resonance imaging was used to evaluate the degeneration and herniation of the intervertebral disc. Genomic deoxyribonucleic acid was extracted from all participants. A polymerase chain reaction assay was carried out to detect the alleles of the aggrecan gene. The association of intervertebral disc degeneration and herniation with the distribution of the aggrecan gene alleles was analyzed.

RESULTS

Findings showed an overrepresentation of alleles with small numbers of repeats in subjects with multilevel disc degeneration, thus indicating a significant distribution difference. There also was a significant difference between the distribution of alleles and the severity of disc degeneration. No significant association was found between any of the alleles either in number or type of disc herniation.

CONCLUSIONS

The current study showed that multilevel and severe disc degeneration was present in the participants with shorter variable numbers of tandem repeat length of the aggrecan gene. This suggests that subjects with shorter variable numbers of tandem repeat length of the aggrecan gene have a risk of having multilevel disc degeneration develop at an early age.

Type X collagen, a natural component of mouse articular cartilage: association with growth, aging, and osteoarthritis

OBJECTIVE

To perform a systematic study on the production and deposition of type X collagen in developing, aging, and osteoarthritic (OA) mouse articular cartilage.

METHODS

Immunohistochemistry was employed to define the distribution of type X collagen and Northern analyses to determine the messenger RNA levels as an indicator of the synthetic activity of the protein.

RESULTS

Type X collagen was observed in the epiphyseal and articular cartilage of mouse knee joints throughout development and growth. Type X collagen deposition in the transitional zone of articular cartilage became evident toward cessation of growth, at the age of 2-3 months. The most intense staining for type X collagen was limited to the tidemark, the border between uncalcified and calcified cartilage. Northern analysis confirmed that the type X collagen gene is also transcribed by articular cartilage chondrocytes. Intense immunostaining was observed in the areas of OA lesions, specifically, at sites of osteophyte formation and surface fibrillation. Type X collagen deposition was also seen in degenerating menisci.

CONCLUSION

This study demonstrates that type X collagen is a natural component of mouse articular cartilage throughout development, growth, and aging. This finding and the deposition of type X collagen at sites of OA lesions suggest that type X collagen may have a role in providing structural support for articular cartilage.

Evidence for a Mendelian gene in a segregation analysis of generalized radiographic osteoarthritis: the Framingham Study

OBJECTIVE

To investigate the inheritance of generalized osteoarthritis (OA).

METHODS

OA was identified on hand and knee radiographs obtained from members of the Framingham Study cohort (the parents) in 1967-1970 and 1992-1993, and from their adult children in the Framingham Offspring Study in 1993-1994. All hand and knee radiographs evaluated for OA were graded using the Kellgren and Lawrence (K/L) scale. A measure of generalized OA was defined as the count of the number of hand and knee joints affected, as determined by the proportion of joints with a K/L grade > or =2. The OA count, treated as a continuous variable, was adjusted for age, body mass index, and a measure of physical activity for each joint area (hand or knee). Calculations were made separately for each generation and each sex, and correlations were analyzed against the standardized residual of OA. Segregation analysis was used to test whether OA aggregated in families, and if its transmission fit a Mendelian pattern.

RESULTS

A total of 337 nuclear families with 2 parents and at least 1 biologic offspring were studied. In parents, the mean age was 61.2 years at the time of hand radiographs and 72.8 years at the time of knee radiographs, which were mostly obtained at a later examination. The mean age at the time of radiographs in offspring was 53.9 years. Using standardized residuals, parent-offspring and sibling-sibling correlations ranged from 0.115 to 0.306. In segregation analyses, models testing the hypotheses of no familial aggregation, no familial transmission, or a Mendelian gene alone were all rejected (P < 0.001 for each of these models). The best-fitting models were mixed models with a Mendelian mode of inheritance and a residual multifactorial component. The Mendelian recessive model provided the best fit.

CONCLUSION

These analyses support a significant genetic contribution to OA, with evidence for a major recessive gene and a multifactorial component, representing either polygenic or environmental factors.

Allelic variation in the vitamin D receptor, lifestyle factors and lumbar spinal degenerative disease

OBJECTIVE

To describe the relation between spinal degenerative disease, allelic variation in the vitamin D receptor gene, and lifestyle factors in a population-based association study.

METHODS

Random population-based sample of 110 men and 172 women over 60 years of age participating in the Dubbo Osteoporosis Epidemiology Study who had spinal radiographs (performed according to a standardised approach), assessment of lifestyle factors, bone densitometry as well as blood taken for genotyping.

RESULTS

Spinal degenerative disease of varying severity was common in this sample. Multivariate analysis of genetic and lifestyle factors simultaneously strengthened the statistical significance of each indicating the presence of additive gene environment interaction. Allelic variation in the vitamin D receptor gene was associated with severity of osteophytosis (adjusted OR "TT" v "tt" 0.41, 95% CI 0.17, 0.97), presence of disc narrowing (adjusted OR "TT" v "tt" 0.45, 95% CI 0.20, 0.99) and weakly with presence of osteophytosis (adjusted OR "TT" v "tt" 0.47, 95% CI 0.19, 1.16) but not with severity of disc narrowing (OR "TT" v "tt" 1.05, 95% CI 0.40, 2.72) or apophyseal arthritis (OR "TT" v "tt" 0.63, 95% CI 0.24, 1.59). Adjustment for femoral neck bone density did not change these findings suggesting that the association is not mediated through bone density. Presence and severity of spinal degenerative disease increased with age at all sites. Current smoking increased both the presence (adjusted OR 9.70, 95% CI 2.08, 45.1) and severity (adjusted OR 2.91, 95% CI 1.16, 9.03) of spinal osteophytosis with intermediate values for past smokers. Severity of osteophytosis was also independently associated with body mass index and quadriceps strength consistent with a contributory effect of physical loading.

CONCLUSIONS

In this elderly sample, both genetic and lifestyle factors were associated with the presence and severity of spinal degenerative disease. There were site specific differences in associations at the spine, which may be because of misclassification of disease status or may indicate possible environmental and genetic differences in the pathophysiology of spinal degenerative disease. Further studies are required to confirm these findings in different population samples and to further explore potential aetiological mechanisms particularly gene environment interaction.

Genetic linkage analysis of 14 candidate gene loci in a family with autosomal dominant osteoarthritis without dysplasia

The role of various gene loci was investigated in a family in which familial osteoarthritis (FOA), with onset at an early age, is transmitted as an autosomal dominant mendelian trait. The absence of clinical and radiographic signs of dysplasia and calcium pyrophosphate deposition disease (CPDD) indicates that the basic disease process in this family is osteoarthritis (OA). Genetic linkage analysis of 14 candidate genes resulted in the exclusion of 10 important genes (COL2A1, COL9A1, COL9A2, COL11A1, COL11A2, COMP, the CPDD region, CRTL-1, CRTM, and MMP3). Other relevant genes were not informative in this family. The candidate loci previously identified in FOA and heritable skeletal disorders associated with OA are clearly not involved in the development of the primary FOA phenotype in the family investigated, indicating genetic heterogeneity.

Abnormal craniofacial growth and early mandibular osteoarthritis in mice harbouring a mutant type II collagen transgene

Skull morphology and histology in the heterozygous offspring of a transgenic founder mouse Del1, harbouring 6 copies of deletion mutation in Col2a1 gene, were compared with those in normal siblings. On visual observation and roentgenocephalometric examination the heads of heterozygous Del1 mice were smaller than normal. Histologically the sizes of cartilaginous structures of the cranial base were reduced. Severe defects were seen in the temporomandibular joint as progressive osteoarthritic lesions. These observations elucidate the relationship between the genotype and phenotype and demonstrate that heterozygous Del1 mice are a useful model for studies on a genetic disturbance where 'clinical' manifestations are not evident until adult age.

Genetics of osteoarthritis

The available evidence suggests that genetic factors have a major role in osteoarthritis. It has been believed for over 50 years that a strong genetic component to certain forms of osteoarthritis is present. This genetic influence has now been estimated to be up to 65% in a recent twin study. The nature of the genetic influence in osteoarthritis is speculative and may involve either a structural defect (that is, collagen), alterations in cartilage or bone metabolism, or alternatively a genetic influence on a known risk factor for osteoarthritis such as obesity. Exciting work has showed that mutations in the collagen type 2 are important in some rare, familial forms of osteoarthritis. Further work is needed on isolating the gene or genes involved in the pathogenesis of this common, disabling condition.