Cartilage collagen damage in hip osteoarthritis similar to that seen in knee osteoarthritis; a case–control study of relationship between collagen, glycosaminoglycan and cartilage swelling

Abstract

BackgroundIt remains to be shown whether OA shares molecular similarities between different joints in humans. This study provides evidence for similarities in cartilage molecular damage in osteoarthritic (OA) joints.MethodsArticular cartilage from osteoarthritic hip joints were analysed and compared to non-OA controls regarding collagen, glycosaminoglycan and water content. Femoral heads from 16 osteoarthritic (OA) and 20 reference patients were obtained from hip replacement surgery due to OA and femoral neck fracture, respectively. Cartilage histological changes were assessed by Mankin grading and denatured collagen type II immunostaining and cartilage was extracted by α-chymotrypsin. Hydroxyproline and Alcian blue binding assays were used to measure collagen and glycosaminoglycan (GAG) content, respectively.ResultsMankin and immunohistology scores were significantly higher in hip OA samples than in reference samples. Cartilage water content was 6% higher in OA samples than in references. 2.5 times more collagen was extracted from OA than from reference samples. There was a positive association between water content and percentage of extractable collagen pool (ECP) in both groups. The amounts of collagen per wet and dry weights did not differ statistically between OA and reference cartilage. % Extractable collagen was not related to collagen per dry weight in either group. However when collagen was expressed by wet weight there was a negative correlation between % extractable and collagen in OA cartilage. The amount of GAG per wet weight was similar in both groups but the amount of GAG per dry weight was higher in OA samples compared to reference samples, which suggests a capacity for GAG biosynthesis in hip OA cartilage. Neither of the studied parameters was related to age in either group.ConclusionsIncreased collagen extractability and water content in human hip cartilage is associated with OA pathology and can be observed at early stages of the degenerative hip OA process. Our results suggest a common degradative pathway of collagen in articular cartilage of different joints. Furthermore, the study suggests that biochemical changes precede more overt OA changes and that chondrocytes may have a capability to compensate molecular loss in the early phase of OA.

Altered swelling and ion fluxes in articular cartilage as a biomarker in osteoarthritis and joint immobilization: a computational analysis

“…In the OA study, simulation results showed an increment of cartilage swelling for advanced grades of OA disease. This has recently been confirmed experimentally [2,56], and associated with weakening of the collagen network and subsequent reduction of PG content. The results obtained here show that changes in mechano-electrochemical properties of the matrix may serve as a biomarker for progression of cartilage degeneration, making the present model a helpful tool to predict the behaviour and therefore the degree of tissue degeneration, thus avoiding complex chemical analyses of the subsequent extraction of cartilage.…”

Relationship between T1rho magnetic resonance imaging, synovial fluid biomarkers, and the biochemical and biomechanical properties of cartilage

“…However, the percentage of degraded collagen in the tissue, as measured using chymotrypsin digestion, and in the synovial fluid, as measured using the C2C assay, was increased. Previous studies have also shown increased collagen degeneration in OA tissue using chymotrypsin digestion (Bank et al, 1997; Hosseininia et al, 2013). Our findings highlight the complexity of factors and interactions that contribute to the T2 relaxation time.…”

“…In order to solubilize extractable or cleaved collagen in the tissue, the second half of each explant was digested overnight in 1 mg/mL α-chymotrypsin (Sigma) at 37 °C (Hosseininia et al, 2013). After chymotrypsin digestion, the supernatant was collected and stored at −20 °C and the remaining tissue was papain digested overnight at 65 °C (Rowland et al, 2013).…”

Assessment of hyaline cartilage matrix composition using near infrared spectroscopy

“…Hydroxyproline which is one of the three major amino acids present in the collagen protein chain is frequently used to estimate the total collagen content in samples (Hosseininia et al, 2013;McAlinden et al, 2014). The amount of collagen in the cartilage powders averaged 72.9% weight/dry weight (w/dw) in adult articular cartilage, 64.1% w/dw in young articular cartilage and 41.5% w/dw in nasal cartilage.…”