Purpose of the study: Sufficient oxygen supply to bone tissue is essential for normal bone development and efficient bone repair. Hypoxia and hypoxia-inducible factor 1Ž (HIF1Ž) signaling pathway have been shown to exhibit profound effects on proliferation, differentiation as well as gene and protein expression in osteoblasts, osteoclasts and mesenchymal stem cells; however, as epigenetic mechanisms also perform an important regulatory role in these cells, our aim was to elucidate whether hypoxia mimetic deferoxamine could influence epigenetic mechanisms in bone cells by modulating the gene expression levels of chromatin-modifying enzymes. Materials and methods: Osteoblast cell line HOS was exposed to deferoxamine, a widely used hypoxia mimetic, and expression profile of 40 genes associated with histone acetylation, deacetylation and DNA methylation was determined using quantitative real time polymerase chain reaction (qPCR) array followed by individual qPCR analyses. In addition, genes associated with hypoxia response,RANK/RANKL/OPG system, WNT/Ž-catenin signaling pathway and oxidative stress were also analyzed. Results: We observed induced expression of histone deacetylase 9 (HDAC9) and suppressed expression of K(lysine) acetyltransferase 5 (KAT5) and DNA methyltransferase 3A (DNMT3A) demonstrating for the first time that expression of genes encoding chromatin-modifying enzymes could be influenced by hypoxia mimetic in HOS cells. Conclusions: Based on our results we can conclude that hypoxia mimetic deferoxamine influences expression of histone acetylation- and DNA methylation-associated genes in osteoblasts and that further studies of hypoxia-induced epigenetic changes in bone cells should be undertaken.
COBISS.SI-ID: 3879793
Adrenergic stimulation is important for osteoclast differentiation and bone resorption. Previous research shows that this happens through [alpha]2-adrenergic receptor (AR), but there are conflicting evidence on presence and role of [alpha]2A-AR in bone. The aim of this study was to investigate the presence of [alpha]2A-AR and its involvement in neuro-endocrine signalling of bone remodelling in humans. Real-time polymerase chain reaction (PCR) and immunohistochemistry were used to investigate [alpha]2A-AR receptor presence and localization in bone cells. Functionality of rs553668 and rs1800544 single nucleotide polymorphism SNPs located in [alpha]2A-AR gene was analysed by qPCR expression on bone samples and luciferase reporter assay in human osteosarcoma HOS cells. Using real-timePCR, genetic association study between rs553668 A)G and rs1800544 C)GSNPs and major bone markers was performed on 661 Slovenian patients with osteoporosis. [alpha2A-AR is expressed in osteoblasts and lining cells but not in osteocytes. SNP rs553668 has a significant influence on [alpha]2A-AR mRNA level in human bone samples through the stability of mRNA. [alpha]2A-AR gene locus associates with important bone remodelling markers (BMD, CTX, Cathepsin K and pOC). The results of this study are providing comprehensive new evidence that [alpha]2A-AR is involved in neuro-endocrine signalling of bone turnover and development of osteoporosis. As shown by our results the neurological signalling is mediated through osteoblasts and result in bone resorption. Genetic study showed association of SNPs in [alpha]2A-AR gene locus with bone remodelling markers, identifying the individuals with higher risk of development of osteoporosis.
COBISS.SI-ID: 3887217