Association between serum levels of the proinflammatory protein S100A8/A9 and clinical and structural characteristics of patients with established knee, hip, and hand osteoarthritis.

OBJECTIVES: To explore the association between S100A8/A9 serum levels with clinical and structural characteristics of patients with established knee, hip, or hand osteoarthritis (OA). METHOD: A cross-sectional exploratory study was conducted with 162 OA patients. Measures for pain, stiffness, and function included the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire or the Australian Canadian Osteoarthritis Hand (AUSCAN) Index and for structural abnormalities, osteophytes and joint space narrowing grades. The association between S100A8/A9 and clinical or structural characteristics was analysed using linear regression or logistic regression where appropriate. RESULTS: The mean age of the OA patients was 56 years, 71% were female, and 61% had a Kellgren and Lawrence (K&L) score ≥ 2. The serum S100A8/A9 level did not differ between knee, hip, and hand OA patients and no association was found between serum S100A8/A9 and clinical characteristics. The serum S100A8/A9 level was negatively associated with the sum score of osteophytes after adjusting for sex and body mass index (BMI) [adjusted ß -0.015, 95% confidence interval (CI) -0.030 to 0.001, p = 0.062] and positively associated with erythrocyte sedimentation rate (ESR) > 12 mm/h (adjusted OR 1.002, 95% CI 1.000-1.004 p = 0.049) for each increase in S100A8/A9 of 1 ng/mL. For hand OA patients, a negative association of S100A8/A9 with sum score of joint space narrowing was found (adjusted ß -0.007, 95% CI -0.016 to 0.001, p = 0.099). CONCLUSIONS: The results from this cross-sectional exploratory study do not support an important role for serum S100A8/A9 levels as a biomarker for clinical and structural characteristics in established knee, hip, and hand OA patients. The inverse association with structural abnormalities and the positive association with ESR may reflect inflammatory synovial processes in patients with OA before structural abnormalities occur.

Dermal connective tissue development in mice: an essential role for tenascin-X.

Deficiency of the extracellular matrix protein tenascin-X (TNX) causes a recessive form of Ehlers-Danlos syndrome (EDS) characterized by hyperextensible skin and hypermobile joints. It is not known whether the observed alterations of dermal collagen fibrils and elastic fibers in these patients are caused by disturbed assembly and deposition or by altered stability and turnover. We used biophysical measurements and immunofluorescence to study connective tissue properties in TNX knockout and wild-type mice. We found that TNX knockout mice, even at a young age, have greatly disturbed biomechanical properties of the skin. No joint abnormalities were noted at any age. The spatio-temporal expression of TNX during normal mouse skin development, during embryonic days 13-19 (E13-E19), was distinct from tropoelastin and the dermal fibrillar collagens type I, III, and V. Our data show that TNX is not involved in the earliest phase (E10-E14) of the deposition of collagen fibrils and elastic fibers during fetal development. From E15 to E19, TNX starts partially to colocalize with the dermal collagens and elastin, and in adult mice, TNX is present in the entire dermis. In adult TNX knockout mice, we observed an apparent increase of elastin. We conclude that TNX knockout mice only partially recapitulate the phenotype of TNX-deficient EDS patients, and that TNX could potentially be involved in maturation and/or maintenance of the dermal collagen and elastin network.

Elastic fiber abnormalities in hypermobility type Ehlers-Danlos syndrome patients with tenascin-X mutations.

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders with characteristic skin and joint involvement. The concept that EDS is a disease of fibrillar collagen was challenged by the identification of a clinically distinct, recessive type of EDS caused by deficiency of the extracellular matrix protein tenascin-X (TNX). Interestingly, haploinsufficiency of TNX is associated with the dominantly inherited hypermobility type of EDS. In this study, we examined whether missense mutations in the TNX gene can account for some of the cases of hypermobility type EDS. Furthermore, we studied whether missense mutations or heterozygosity for truncating mutations in the TNX gene lead to alterations in the dermal connective tissue. Sequence analysis revealed three missense mutations in TNX in hypermobility type EDS patients, which were not present in 192 control alleles. Morphometric analysis of skin biopsies of these patients showed altered elastic fibers in one of them, suggesting that this missense mutation is disease causing. Light microscopic and ultrastructural changes of the elastic fibers were observed in TNX-haploinsufficient hypermobility type EDS patients, which were not found in hypermobility type EDS patients in whom TNX mutations were excluded. Our results indicate that the observed alterations in elastic fibers are specific for hypermobility type EDS patients with mutations of TNX.

A recessive form of the Ehlers-Danlos syndrome caused by tenascin-X deficiency.

BACKGROUND: The Ehlers-Danlos syndrome is a heritable connective-tissue disorder caused by defects in fibrillar-collagen metabolism. Mutations in the type V collagen genes account for up to 50 percent of cases of classic Ehlers-Danlos syndrome, but many other cases are unexplained. We investigated whether the deficiency of the tenascins, extracellular-matrix proteins that are highly expressed in connective tissues, was associated with the Ehlers-Danlos syndrome. METHODS: We screened serum samples from 151 patients with the classic, hypermobility, or vascular types of the Ehlers-Danlos syndrome; 75 patients with psoriasis; 93 patients with rheumatoid arthritis; and 21 healthy persons for the presence of tenascin-X and tenascin-C by enzyme-linked immunosorbent assay. We examined the expression of tenascins and type V collagen in skin by immunohistochemical methods and sequenced the tenascin-X gene. RESULTS: Tenascin-X was present in serum from all normal subjects, all patients with psoriasis, all patients with rheumatoid arthritis, and 146 of 151 patients with the Ehlers-Danlos syndrome. Tenascin-X was absent from the serum of the 5 remaining patients with Ehlers-Danlos syndrome, who were unrelated. Tenascin-X deficiency was confirmed in these patients by analysis of skin fibroblasts and by immunostaining of skin. The expression of tenascin-C and type V collagen was normal in these patients. All five of these patients had hypermobile joints, hyperelastic skin, and easy bruising, without atrophic scarring. Tenascin-X mutations were identified in all tenascin-X-deficient patients; one patient had a homozygous tenascin-X gene deletion, one was heterozygous for the deletion, and three others had homozygous truncating point mutations, confirming a causative role for tenascin-X and a recessive pattern of inheritance. CONCLUSIONS: Tenascin-X deficiency causes a clinically distinct, recessive form of the Ehlers-Danlos syndrome. This finding indicates that factors other than the collagens or collagen-processing enzymes can cause the syndrome and suggests a central role for tenascin-X in maintaining the integrity of collagenous matrix.