Signaling of Glial Cell Line-Derived Neurotrophic Factor and Its Receptor GFRα1 Induce Nurr1 and Pitx3 to Promote Survival of Grafted Midbrain-Derived Neural Stem Cells in a Rat Model of Parkinson Disease

Glial cell line-derived neurotrophic factor (GDNF) and its receptor GFR alpha 1 have been implicated in the survival of ventral midbrain dopaminergic (DA) neurons, but the molecular mechanisms by which GDNF generates DA neurons in grafted midbrain-derived neural stem cells (mNSCs) are not understood. Midbrain-derived neural stem cells isolated from rat embryonic mesencephalon (embryonic day 12) were treated with GDNF or in combination with GFR alpha 1 small interfering RNA. Reverse transcription-polymerase chain reaction, Western blot, and immunocytochemistry were used to test the expression of the orphan nuclear receptor Nurr1 and the transcription factor Pitx3 and newborn tyrosine hydroxylase (TH)-positive cells. Treatment of mNSCs with GDNF increased mNSCs' sphere diameter, reduced expression of caspase 3, and increased expression of Bcl-2. Glial cell line-derived neurotrophic factor-treated mNSCs enhanced Nurr1 and Pitx3 expression and the fraction of TH-, TH/Pitx3-, and TH/Nurr1-positive cells in culture. Grafted GDNF-treated mNSCs significantly decreased apomorphine-induced rotation behavior in 6-hydroxydopamine-lesioned rats. Glial cell line-derived neurotrophic factor-treated mNSCs showed increased numbers of TH/Pitx3- and TH/Nurr1-postivie cells. The effect elicited by GDNF was inhibited by small interfering RNA- mediated knockdown of GFR alpha 1. Our data demonstrate the contribution of GDNF to DA neuron development and may also elucidate pathogenetic mechanisms in Parkinson disease and contribute to the development of novel therapies for the disorder.