Effects of hypoxia on anabolic and catabolic gene expression and DNA methylation in OA chondrocytes

Abstract

chondrocytes (ACs) and its regulatory mechanisms remain unclear. This study aimed to explore epigenetic regulatory mechanisms of age-related SOX9 expression in ACs of mice, spanning from the embryonic stage to 18 months of age. Methods: The hip and shoulder joints of wild type BALB/c mice were harvested at embryonic day 16.5 and 1, 2, 6, 12 and 18 months for histopathological and immunohistochemical analyses. Femoral and humeral head cartilage from the same age groups was used for chondrocyte isolation, gene expression, methylated DNA immunoprecipitation or chromatin immunoprecipitation assays to examine epigenetic changes in the promoter region of the Sox9 gene. siRNA-mediated knockdown of the histone lysine-specific demethylases-1 gene (Lsd1) and 5-azacytidine treatment were performed in cultured ACs. Results: Sox9 mRNA and protein were highly expressed in ACs during joint development but significantly decreased at 2-18 months of age. No histopathological features of osteoarthritis were observed in examined joints by 18 months. Epigenetic DNA methylation and histone methylation are both associated with the age-dependent SOX9 expression. Knockdown of Lsd1 is sufficient to up-regulate SOX9 expression in ACs of adult mice through increased recruitment of H3K4me2 (a histone modification for transcriptional activation) in the promoter region of the Sox9 gene. However, the reduction of DNA methylation in the Sox9 promoter region induced by 5-azacytidine treatment in cultured ACs did not increase Sox9 expression. The data suggest that reduction of SOX9 expression in ACs of adult mice is primarily regulated by H3K4me2. Conclusions: These results suggest that SOX9 expression in mouse ACs is significantly decreased after the completion of joint development due to reduced demands for SOX9. This developmental switch in SOX9 expression in mouse articular cartilage is primarily regulated by epigenetic histone methylation.

Functional Restoration of Amyotrophic Lateral Sclerosis Patient-Derived Mesenchymal Stromal Cells Through Inhibition of DNA Methyltransferase

“…DNMT3A and DNMT3B known as the de novo DNA methyltransferases are able to transfer methyl group to unmethylated CpGs in DNA (Li and Zhang 2014). Aberrant DNA methylation patterns in the genome are associated with various pathological processes and age-related diseases, including cancer, neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, osteoarthritis, type 2 diabetes, and renal disease (Ammal Kaidery et al 2013;De Jager et al 2014;Alvarez et al 2014;Hoile et al 2014). In ALS patients, increased expression of DNMT1 and DNMT3A has been observed in motor cortex tissues and spinal cord motor neurons (Chestnut et al 2011).…”

DNA Methylation Profiling in Chondrocyte Dedifferentiation In Vitro

“…To date, the mechanisms underlying the chondrocyte dedifferentiation remain largely unknown. Recently, several studies have suggested that epigenetic regulation plays a vital role in chondrocyte phenotype changes (Alvarez et al, ; Haseeb et al, ). So far, DNA methylation, histone modification, and non‐coding RNA such as microRNAs (miRNAs) are the three major epigenetic modifications.…”

Scaffold With Natural Calcified Cartilage Zone for Osteochondral Defect Repair in Minipigs

“…19 As a result, cartilage and subchondral bone were separated into relatively independent physiological environments by this thin structure. These independent environments that are different from the subchondral bone might help to maintain the phenotype of cartilage from degeneration, 2,42 and may provide an explanation for why the cartilage tissue in the non-CCZ group was ultimately replaced by fibrocartilage.…”

“…In addition, the CCZ isolated the osteochondral unit into 2 different parts: avascular, hypoxic hyaline cartilage, and aerobic subchondral bone. 2,42 In normal physiological conditions, articular cartilage tissue is under 1% to 6% O 2 tension compared with atmospheric air (21%). It is suggested that a low oxygen tension condition is essential for chondrocyte survival 35 and is able to enhance marrow stem cell chondrogenic differentiation.…”