Object: Glial cell line-derived neurotrophic factor (GDNF) has been shown to confer neuroprotective effects on dopaminergic neurons. The authors investigated the effects of GDNF on 6-hydroxydopamine (6-OHDA)-treated dopaminergic neurons in vitro and in vivo.
Methods: First, the authors examined how 1, 10, or 100 ng/ml of GDNF, administered to cells 24 hours before, simultaneously with, or 2 or 4 hours after 6-OHDA was added, affected dopaminergic neurons. In a primary culture of E14 murine ventral mesencephalic neurons, earlier treatment with the higher dosage of GDNF suppressed 6-OHDA-induced loss of dopaminergic neurons better than later treatment. Next, the authors examined whether continuous infusion of GDNF at earlier time points would demonstrate a greater neuroprotective effect in a rat model of Parkinson disease (PD). They established a human GDNF-secreting cell line, called BHK-GDNF, and encapsulated the cells into hollow fibers. The encapsulated cells were unilaterally implanted into the striatum of adult rats 1 week before; simultaneously with; or 1, 2, or 4 weeks after 6-OHDA was given to induce lesions of the same striatum. With the earlier transplantation of a BHK-GDNF capsule, there was a significant reduction in the number of amphetamine-induced rotations displayed by the animals. Rats that had received earlier implantation of BHK-GDNF capsules displayed more tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta and a tendency for glial proliferation in the striatum.
Conclusions: These neuroprotective effects may be related to glial proliferation and signaling via the GDNF receptor alpha1. The results of this study support a role for this grafting technique in the treatment of PD.