Abstract
A reliable method to induce neural progenitor/stem cells (NPCs) into dopaminergic (DAergic) neurons as well as the mechanism involved has not yet been established. To induce DAergic differentiation from NPCs, cell cycle blockers in G1/S phase and the factors up-regulated in DA-depleted striatum were used. Treatment of a G1/S phase blocker, desferoxamine (DFO), significantly increased the expression of TGFβ1 mRNA 24 h after the differentiation, while TGFβ2 and β3 mRNAs expression did not change. Treatment of DFO increased the production of trasnforming growth factor beta (TGFβ) followed by nuclear translocation of smad 3, and inhibition of TGFβ signal decreased the number of β-tubulin III-positive neurons. Treatment with the factors up-regulated in DA-depleted striatum (IL-1β, LIF, GDNF, pleiotrophin) increased the number of tyrosine hydroxylase (TH)-positive cells compared with controls. Increases in DA in the medium were confirmed by high performance liquid chromatography. As an increase in hypoxia inducible factor (HIF)-1α protein was found, we investigated HIF-1α effect on differentiation of NPCs to DAergic neurons. Inhibition of HIF-1α caused a decrease in TH-positive cells. Data suggest that neuronal differentiation is induced by cell cycle regulation in G1/S phase mediated by TGF-β and DAergic differentiation was induced by LIF or pleiotrophin mediated by HIF-1α. [J Physiol Sci. 2008;58 Suppl:S152]
