Early-onset primary osteoarthritis and mild chondrodysplasia. Radiographic and pathologic studies with an analysis of cartilage proteoglycans

Persistence of intracellular and extracellular changes after incompletely suppressing expression of the R789C (p.R989C) and R992C (p.R1192C) collagen II mutants

Mutations in COL2A1 produce a spectrum of disorders whose hallmark feature is alterations in skeletal development. Attempts to counteract the effects of collagen mutations at the molecular level have been relatively ineffective due to the inability to selectively suppress a mutant allele, and failure to deliver a sufficient number of cells expressing wild-type collagen. Moreover, these approaches are hampered because the minimal therapeutic conditions that would allow extracellular matrix remodeling and recovery of cells from stress are not known. Here, we employed a tetracycline-inducible system for expressing the R789C or R992C collagen II mutants, allowing us to decrease the production of mutant proteins by 25, 50, 75, or 100% with respect to their initial production. Through analysis of intracellular and extracellular parameters we have shown that affected cell/matrix systems are able to recover from mutation-induced aberrations only when 100% expression of mutant collagens is shut off, but not if the expression of small amounts of mutant molecules persists in the system. Our data suggest that efficient remodeling of tissues affected by the presence of thermolabile collagen mutants may depend on their complete elimination rather than on partial reduction.

Nutritional considerations in joint health

Osteoarthritis, a debilitating joint disorder, is the most common form of arthritis in the United States, where it affects an estimated 21 million people. In 2004, the direct and indirect health care costs associated with all forms of arthritis were approximately 86 billion dollars. Joint discomfort from osteoarthritis and other joint disorders may reduce physical activity in individuals experiencing this condition, resulting in energy imbalance and weight gain. Increased weight can exacerbate existing problems, as additional stress on joints stimulates risk of additional joint disorders. Dietitians play a role in preventing or reversing the problem of joint disorders by promoting nutrient-rich diets that support joint health through improvement in cartilage metabolism. In addition, counseling individuals on weight management and active lifestyles are key strategies for the management of joint health.

The phenotypic spectrum in patients with arginine to cysteine mutations in the COL2A1 gene

BACKGROUND

The majority of COL2A1 missense mutations are substitutions of obligatory glycine residues in the triple helical domain. Only a few non-glycine missense mutations have been reported and among these, the arginine to cysteine substitutions predominate.

OBJECTIVE

To investigate in more detail the phenotype resulting from arginine to cysteine mutations in the COL2A1 gene.

METHODS

The clinical and radiographic phenotype of all patients in whom an arginine to cysteine mutation in the COL2A1 gene was identified in our laboratory, was studied and correlated with the abnormal genotype. The COL2A1 genotyping involved DHPLC analysis with subsequent sequencing of the abnormal fragments.

RESULTS

Six different mutations (R75C, R365C, R519C, R704C, R789C, R1076C) were found in 11 unrelated probands. Each mutation resulted in a rather constant and site-specific phenotype, but a perinatally lethal disorder was never observed. Spondyloarthropathy with normal stature and no ocular involvement were features of patients with the R75C, R519C, or R1076C mutation. Short third and/or fourth toes was a distinguishing feature of the R75C mutation and brachydactyly with enlarged finger joints a key feature of the R1076C substitution. Stickler dysplasia with brachydactyly was observed in patients with the R704C mutation. The R365C and R789C mutations resulted in classic Stickler dysplasia and spondyloepiphyseal dysplasia congenita (SEDC), respectively.

CONCLUSIONS

Arginine to cysteine mutations are rather infrequent COL2A1 mutations which cause a spectrum of phenotypes including classic SEDC and Stickler dysplasia, but also some unusual entities that have not yet been recognised and described as type II collagenopathies.

The onset of generalized osteoarthritis in older women: a qualitative approach

OBJECTIVE

This qualitative study aims to investigate which factors are possibly associated with the onset of generalized osteoarthritis (OA) in older women.

METHODS

The study population was recruited from participants of a group course, "Coping With Osteoarthritis of the Hip or Knee." Twenty-three women with generalized OA were identified, 20 of whom participated in a semistructured interview at home. All data were self-reported by the subjects.

RESULTS

Hereditary factors were present in 17 women. Metabolic factors (such as impairments in carbohydrate and lipid metabolism, diabetes, etc.) were not prevalent. Twelve women thought that certain diets influenced their pain symptoms. Five women spontaneously mentioned their health status during the Second World War as a cause of their OA. Four considered too much stress as being a cause, and in 13 women symptoms started after a period of stressful life events or depression.

CONCLUSION

According to the respondents, depression, stress, and diets are associated with the onset and worsening of their generalized OA. Heredity and a low health status at a vulnerable age may also be important. These findings could generate new hypotheses that can be tested in future quantitative studies.

Changes in serum cartilage marker levels indicate altered cartilage metabolism in families with the osteoarthritis-related type II collagen gene COL2A1 mutation

OBJECTIVE

The Arg5l9-Cys mutation in type II collagen results in severe, precocious familial osteoarthritis (OA) in 100% of carriers within the first 3 decades of life. The carrier population provided a well-defined patient population for the study of serum markers of familial OA with respect to pathogenesis, diagnosis, and prognosis.

METHODS

Serum was obtained from 31 mutation-positive individuals and 16 mutation-negative individuals. OA severity was determined by clinical and radiologic assessments. Levels of serum cartilage oligomeric matrix protein (COMP), keratan sulfate (KS) epitope, the 846 epitope of aggrecan, and the C propeptide of type II collagen (CPII) were measured and were correlated with the radiologic findings.

RESULTS

COMP and KS levels, both of which have been suggested to be indicative of disturbed cartilage turnover, were significantly elevated in mutation-positive individuals and in the individuals with OA regardless of mutation status. There was no statistically significant difference between mutation-positive, mutation-negative, OA-positive, and OA-negative individuals with respect to serum concentrations of epitope 846 or CPII, both of which are putative markers of cartilage repair.

CONCLUSION

Study of the macromolecular constituents of cartilage released into serum in subjects with familial OA revealed altered metabolism in OA, as demonstrated by elevated COMP and KS levels. Other constituents, the 846 epitope and CPII, were not altered, indicating dissociation of cartilage anabolism and breakdown. Future sequential studies will provide an opportunity to define biochemical changes as familial OA develops and to monitor therapeutic responses.

Phenotypic expressions of a Gly 154Arg mutation in type II collagen in two unrelated patients with spondyloepimetaphyseal dysplasia (SEMD)

Type II collagenopathies consist of chondrodysplasias ranging from lethal to mild in severity. A large number of mutations has been found in the COL2A1 gene. Glycine substitutions have been the most common types of mutation. Genotype-phenotype correlations in type II collagenopathies have not been established, partly because of insufficient clinical and radiographic description of the patients. We found a glycine-to-arginine substitution at position 154 in type II collagen in two unrelated isolated propositi with spondyloepimetaphyseal dysplasia and provide a comparative clinical and radiographic analysis from birth to young adulthood for this condition. The clinical phenotype was disproportionate short stature with varus/valgus deformities of the lower limbs requiring corrective osteotomies, and lumbar lordosis. The skeletal radiographs showed an evolution from short tubular bones, delayed epiphyseal development, and mild vertebral involvement to severe metaphyseal dysplasia with dappling irregularities, and hip "dysplasia." The metaphyseal abnormalities disappeared by adulthood.

Familial spondyloepiphyseal dysplasia tarda, brachydactyly, and precocious osteoarthritis associated with an arginine 75-->cysteine mutation in the procollagen type II gene in a kindred of Chiloe Islanders. I. Clinical, radiographic, and pathologic findings

OBJECTIVE

To characterize a kindred of Chiloe Islanders with spondyloepiphyseal dysplasia tarda (SEDT), brachydactyly, precocious osteoarthritis (OA), and intraarticular calcification.

METHODS

Sixteen family members underwent a complete physical examination, anthropometric measurements, radiographic studies of the spine and peripheral joints, and analysis of the type II procollagen gene (COL2A1).

RESULTS

Seven family members presented with SEDT, brachydactyly, precocious OA, and periarticular calcification while 2 others had the same syndrome but without brachydactyly. The inheritance was autosomal dominant, and the disease cosegregated with a base substitution in the COL2A1 gene.

CONCLUSION

The syndrome o SEDT, precocious OA, and brachydactyly in a kindred of Chiloe Islanders is associated with a point mutation in 1 allele of the COL2A1 gene. The relationship of this type of SEDT to familial calcium pyrophosphate dihydrate deposition disease and idiopathic hip dysplasia, both endemic in Chiloe Islanders, needs to be further investigated.

Clinical correlations of osteoarthritis associated with a single-base mutation (arginine519 to cysteine) in type II procollagen gene. A newly defined pathogenesis

OBJECTIVE

To investigate the occurrence and clinical correlation of the arg519-to-cys mutation in the type II procollagen gene in patients with osteoarthritis (OA).

METHODS

Sixty-six subjects from 7 families with a strong family history of generalized OA and 13 patients with erosive OA were evaluated clinically and radiologically. Blood samples from 58 subjects in the familial OA group and from all 13 patients with erosive OA were obtained for DNA analysis. Exon 31 of COL2A1, which spans residue 519, was amplified by polymerase chain reaction.

RESULTS

The arg519-to-cys mutation was detected in 2 of the 7 families with generalized OA. In these 2 families, the mutation was present in the 2 probands and in 19 other clinically affected family members, as well as in 3 (so-far) clinically unaffected family members (ages 25, 14, and 11 years). It was absent in 18 clinically unaffected members tested. The mutation was associated with a distinctive pattern of early-onset, aggressive, generalized OA with a mild spinal chondrodysplasia. Inheritance was autosomal dominant. No mutation was found in any of the patients with erosive OA.

CONCLUSION

The arg519-to-cys mutation defines a new pathogenic factor in generalized OA with characteristic clinical and radiologic features. The demonstration of a mutation in 3 of 8 families with OA studied thus far suggests a significant incidence of genetically related clinical OA.

Collagen genes: mutations affecting collagen structure and expression

It is to be expected that more collagen genes will be identified and that additional heritable connective tissue diseases will be shown to arise from collagen mutations. Further progress will be fostered by the coordinated study of naturally occurring and induced heritable connective tissues diseases. In some instances, human mutations will be studied in more detail using transgenic mice, while in others, transgenic studies will be used to determine the type of human phenotype that is likely to result from mutations of a given collagen gene. Further studies of transcriptional regulation of the collagen genes will provide the prospect for therapeutic control of expression of specific collagen genes in patients with genetically determined collagen disorders as well as in a wide range of common human diseases in which abnormal formation of the connective tissues is a feature.

Early-onset osteoarthritis linked to the type II procollagen gene. Detailed clinical phenotype and further analyses of the gene

OBJECTIVE

To specify in detail the clinical phenotype in 2 Finnish families demonstrating linkage between the type II procollagen gene (COL2A1) and osteoarthritis (OA). We also reevaluated the linkage and screened the exon sequences of the COL2A1 gene for mutations.

METHODS

We used single-stranded conformation polymorphism and denaturing gradient-gel electrophoresis techniques for the analyses.

RESULTS

The patients' phenotype represented typical, but early-onset, OA. There was no clinical or radiographic evidence of chondrodysplasia. No mutation in the protein-coding regions of the COL2A1 gene could be identified. However, the linkage analysis with a new multiallelic marker resulted in a statistically more significant logarithm of odds (LOD) score than has been reported.

CONCLUSION

Familial OA with classic clinical and radiographic findings is tightly linked to the COL2A1 gene. Systematic screening of the 54 exons did not, however, reveal any mutations; this suggests that the mutation may lie in the promoter region or within the introns of this 35-kb gene.

Cartilage matrix metabolism in osteoarthritis: markers in synovial fluid, serum, and urine

Osteoarthritis is a major cause of disability and early retirement. Yet we lack the means to diagnose the disease in its early stages or to monitor the effects of treatment on the target tissue, the joint cartilage. Neither can we identify the disease mechanisms at the tissue or cell level. Current research focuses on the use of markers of cartilage matrix metabolism in body fluids as a means to diagnose and monitor osteoarthritis. Cartilage proteoglycan, collagen and glycoprotein fragments, as well as proteinases and their inhibitors, are being suggested for this purpose. Structural information on matrix molecule fragments released into body fluids may also help to identify the enzymes active in the destruction of the cartilage, a central issue in osteoarthritis.

Markers of cartilage metabolism in arthrosis. A review

The mechanisms involved in the disease process in arthrosis are largely unknown, with genetics, joint malalignment, overload or trauma, obesity, and aging as some of the known or suspected contributing factors. Even less well known is how these general factors are translated into disease mechanisms at the cell and tissue levels. However, it may be argued that degradation of cartilage matrix is a key event at some time in the development of arthrosis. During this process, fragments of matrix molecules and other chondrocyte products are released into the joint fluid and eventually into other body fluids. These molecules can be used as markers of cartilage metabolism to monitor joint disease. In addition, by identifying the proteases and the structure of the released matrix fragments, we may improve our understanding of the cellular mechanisms active in cartilage degradation. Such information offers improved diagnostic and prognostic tools for rational treatment aimed at retarding cartilage destruction in arthrosis.

Classification of disease: osteoarthritis

Criteria for the classification of osteoarthritis (OA) have been developed to establish uniformity in the reporting of this disease. Different criteria sets were developed for OA of the knee, hand, and hip that can serve different investigative purposes. The use of checklists facilitates the use of the criteria sets.

Cartilage expression of a type II collagen mutation in an inherited form of osteoarthritis associated with a mild chondrodysplasia

In a family who expressed severe dominantly inherited osteoarthritis, the underlying mutation was traced by genomic sequencing to a single base change which predicts an amino acid substitution of cysteine for arginine at residue 519 of the triple-helical domain of the type II collagen molecule (Ala-Kokko, L., C. T. Baldwin, R. W. Moskowitz, and D. J. Prockop. 1990. Proc. Natl. Acad. Sci. USA. 87:6565-6568). In the present study we examined whether this predicted protein phenotype was evident in articular cartilage obtained from an affected family member who underwent hip surgery. The cartilage collagen was solubilized by CNBr digestion. Cysteine residues were labeled by reduction and alkylation with 14C-iodoacetate. Collagen CNBr-peptides were fractionated by ion exchange and reverse phase column chromatography. One peptide from the alpha 1(II) chain, alpha 1(II) CB8, was found to be radiolabeled. Tryptic peptides were prepared from it and identified by microsequence analysis. The results show that approximately one-quarter of the alpha 1(II) chains present in the polymeric extracellular collagen of the patient's cartilage contained the Arg519-to-Cys substitution. The protein exhibited other abnormal properties including disulfide-bonded alpha 1(II)-dimers and signs of posttranslational overmodification. The premature cartilage failure and osteoarthritis are presumably a result of the abnormal type II collagen being expressed in the cartilage matrix.

Single base mutation in the type II procollagen gene (COL2A1) as a cause of primary osteoarthritis associated with a mild chondrodysplasia

A cosmid clone was isolated that contained an allele for the type II procollagen gene previously shown to be coinherited with primary generalized osteoarthritis in a large family. Affected members of the family had evidence of a mild chondrodysplasia, but they developed progressive osteoarthritic changes in many joints that had no epiphyseal deformities. The clone contained 52 of the 54 exons of the gene. Nucleotide sequencing of greater than 20,000 base pairs from the clone demonstrated that all the coding sequences and all the intron-exon boundaries were normal except for a single base mutation that converted the codon for arginine at position 519 of the alpha 1(II) chain to a codon for cysteine, an amino acid not found in type II collagen from humans or a variety of other species. The mutation was found in all affected members of the family but not in unaffected members or in 57 unrelated individuals.