Cellular and epigenetic features of a young healthy and a young osteoarthritic cartilage compared with aged control and OA cartilage

Abstract

Osteoarthritis (OA) is generally a disease of the elderly population, but can occur in young patients in exceptional cases. This study compares the cellular and epigenetic features of primary old-age OA with those of secondary OA in a 23-year-old patient with developmental dysplasia of the hip. In addition, control cartilage from a 14-year-old was compared with that from patients with a fracture of the neck of femur (#NOF) to establish to what extent the latter is a useful control for OA. Articular cartilage was obtained from discarded femoral heads after hip arthroplasty. MMP-3, MMP-9, MMP-13, and ADAMTS-4 were immunolocalized and the methylation status of specific promoter CpG sites was determined. Both primary and secondary OA were characterized by loss of aggrecan, formation of clones, and abnormal expression of the proteases that correlated with epigenetic DNA demethylation. The latter indicated that the abnormal expression of the cartilage-degrading proteases was not due to a short-term up-regulation, but a heritable, permanent alteration in gene expression. Comparing cell densities in young and old control cartilage estimated an age-related cell loss of $1% per year. In aged #NOF cartilage, some superficial-zone chondrocytes expressed the proteases, but the majority of cells were immunonegative and their promoters were hypermethylated. The cellular and epigenetic features of the intermediate and deep zones of #NOF cartilage are thus similar to those of young healthy cartilage, justifying the use of #NOF cartilage as control cartilage for OA, providing the superficial zone is removed. ß

Early Cartilage Degeneration in a Rat Experimental Model of Developmental Dysplasia of the Hip

“…In spite of provision of adequate and suitable management in the early stages of the disease, the incidence rate of long-term degenerative OA remains higher than in the normal population [22,27]. These studies suggest that DDH is one of the predisposing factors for OA and the reasons may be mechanical.…”

Regulated Transcription of Human Matrix Metalloproteinase 13 (MMP13) and Interleukin-1β (IL1B) Genes in Chondrocytes Depends on Methylation of Specific Proximal Promoter CpG Sites

“…Human Primary Chondrocyte Culture and 5-Aza-dC Treatment-For culture and in vitro analysis, only deep-zone primary non-OA chondrocytes were utilized, as described (21). Before treatment, chondrocytes were cultured for 48 h at an average density of 16 ϫ 10 3 cells/cm 2 in a 25-cm 2 flask in 5 ml of ␣-modified Eagle's medium supplemented with 10% FBS (Invitrogen), 1% insulin-transferrin-selenium (Sigma-Aldrich), 100 units/ml of penicillin, and 100 g/ml of streptomycin (Lonza) and 100 g/ml of ascorbic acid (Sigma-Aldrich).…”

“…Moreover, only a few reports have addressed how methylation of individual CpG sites influences the promoter activity of a specific gene (6,10,11), and the relative contributions of the methylation status of each individual CpG site to the transcriptional regulation of a given gene in vivo remain largely unexplored. In addition, although epigenetic gene regulation has been broadly investigated in other contexts, little is known about the specific impact of this mechanism of gene control in musculoskeletal diseases (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29).…”

Dual function of β-catenin in articular cartilage growth and degeneration at different stages of postnatal cartilage development

“…OA manifests as dysplasia and general degeneration of the cartilage [3,4]; however, the molecular mechanisms underlying cartilage development and degeneration remain to be fully elucidated. Recent studies have shown that β-catenin plays a critical role throughout chondrogenesis and chondrocyte maturation [5][6][7].…”