Pharmacological inhibition of DNA methyltransferase 1 promotes neuronal differentiation from rodent and human nasal olfactory stem/progenitor cell cultures.

Nasal olfactory stem and neural progenitor cells (NOS/PCs) are considered possible tools for regenerative stem cell therapies in neurodegenerative diseases. Neurogenesis is a complex process regulated by extrinsic and intrinsic signals that include DNA-methylation and other chromatin modifications that could be experimentally manipulated in order to increase neuronal differentiation. The aim of the present study was the characterization of primary cultures and consecutive passages (P2-P10) of NOS/PCs isolated from male Swiss-Webster (mNOS/PCs) or healthy humans (hNOS/PCs). We evaluated and compared cellular morphology, proliferation rates and the expression pattern of pluripotency-associated markers and DNA methylation-associated gene expression in these cultures. Neuronal differentiation was induced by exposure to all-trans retinoic acid and forskolin for 7 days and evaluated by morphological analysis and immunofluorescence against neuronal markers MAP2, NSE and MAP1B. In response to the inductive cues mNOS/PCs expressed NSE (75.67%) and MAP2 (35.34%); whereas the majority of the hNOS/PCs were immunopositive to MAP1B. Treatment with procainamide, a specific inhibitor of DNA methyltransferase 1 (DNMT1), increases in the number of forskolin'/retinoic acid-induced mature neuronal marker-expressing mNOS/PCs cells and enhances neurite development in hNOS/PCs. Our results indicate that mice and human nasal olfactory stem/progenitors cells share pluripotency-related gene expression suggesting that their application for stem cell therapy is worth pursuing and that DNA methylation inhibitors could be efficient tools to enhance neuronal differentiation from these cells.