Oestrogen deficiency and oxidative stress are the main factors responsible for postmenopausal and age-related bone loss. In addition, epigenetic mechanisms and in particular miRNAs, are becoming increasingly recognised as significant molecular regulators of bone cells. Our aim was to investigate how oestrogens and oxidative stress alone or in combination influence the expression of miRNAs in osteoblasts. An osteoblast cell line HOS was transfected with a plasmid containing oestrogen receptor α and exposed to 17β-estradiol (E2) and/or hydrogen peroxide. Western blotting was used to confirm the successful transfection and the AOX1 gene expression was measured in order to verify the establishment of oxidative stress. Nanostring nCounter technology was used to obtain the expression profile of 800 miRNAs. Our results revealed only a slight influence of E2 on miRNA expression, while the impact of hydrogen peroxide was significantly larger. We observed downregulation of miR-338-3p after E2 treatment. Hydrogen peroxide on the other hand positively affected expression of miR-132-3p and miR-630 among other, while downregulating miR-133 and miR-214-3p among other. miR-133, miR-214-3p and miR-338-3p have already been shown to have important roles in osteoblast biology. Of note, E2 exhibited no protective effect when co-treated with hydrogen peroxide. Even though the investigated stimuli and miRNA have been studied separately in osteoblasts before, our results are the first to show that oxidative stress exhibits a significant impact on miRNA expression in osteoblasts.
Disclosure: The authors declared no competing interests. The study was funded by grants BI-HR/14-15-032, ARMR19, P3-0298 and J3-5511.