Selenium (Se) is a trace element that plays important role in antioxidant defense in the brain. Sodium selenite (NaSeO) is an inorganic salt of Se which has an antioxidant function. In the present study, we investigated the effect of Sodium selenite on the expression of important neuronal microRNAs during neural differentiation of bone marrow-derived stem cells (BMSCs).
Mesenchymal stem cells were collected from rat bone marrow and cultured in the Dulbecco’s Modified Eagle Medium (DMEM) medium. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay was conducted to determine the toxicity of NaSeO. For neural induction, BMSCs were divided into control, NaSeO containing (10 ng/mL) and Na2SeO free groups and cultured in DMEM medium supplemented with Isobutyl-l-methylxanthine (IBMX), Fibroblast growth factor 2 (FGF2), B27, Retinoic acid, and brain derived neurotrophic factor (BDNF) for 14 days. At the end of the differentiation, immunostaining against Microtubule associated protein 2 (Map-2) and Choline acetyltransferase (ChAT) proteins was performed. Also, the total RNA is extracted from control and neural differentiated cells using a special kit, and the expression of miR-9, miR-124, and miR-29a was analyzed using real-time polymerase chain reaction (RT-PCR).
Increasing NaSeO concentrations had increasing toxicity; therefore, the concentration of 10 ng/mL was used as a supplement during neural differentiation. Examination of the expression of Map-2 and ChAT proteins showed that NaSeO increased the expression of them and consequently the neuronal differentiation of BMSCs. NaSeO also significantly increased the expression of miR-9, miR-124, and miR-29a in BMSCs undergoing neuronal differentiation.
Our results suggest that the protective effect of selenium on neural differentiation of stem cells may be mediated through neuron specific microRNAs. This result further highlights the importance of selenium supplementation in preventing neuronal diseases.

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