Striatal
transplantation of dopaminergic (DA) neurons or neural stem cells (NSCs) has been reported to improve the symptoms of
Parkinson's disease (PD), but the low rate of cell survival, differentiation, and integration in the host brain limits the therapeutic efficacy. We investigated the therapeutic effects of intracranial
co-
transplantation of mesencephalic NSCs stably overexpressing human glial-derived neurotrophic factor (
GDNF-mNSCs) together with fetal DA neurons in the
6-OHDA rat model of PD. Striatal injection of mNSCs labeled by the contrast enhancer superparamagnetic
iron oxide (SPIO) resulted in a hypointense signal in the striatum on T2-weighted magnetic resonance images that lasted for at least 8 weeks post-injection, confirming the long-term survival of injected stem cells in vivo.
Co-
transplantation of
GDNF-mNSCs with fetal DA neurons significantly reduced
apomorphine-induced rotation, a behavioral endophenotype of PD, compared to
sham-treated controls, rats injected with mNSCs expressing empty vector (control mNSCs) plus fetal DA neurons, or rats injected separately with either control mNSCs,
GDNF-mNSCs, or fetal DA neurons. In addition, survival and differentiation of mNSCs into DA neurons was significantly greater following
co-
transplantation of
GDNF-mNSCs plus fetal DA neurons compared to the other treatment groups as indicated by the greater number of cell expressing both the mNSCs lineage tracer
enhanced green fluorescent protein (eGFP) and the DA neuron marker
tyrosine hydroxylase. The success of cell-based therapies for PD may be greatly improved by
co-
transplantation of fetal DA neurons with mNSCs genetically modified to overexpress trophic factors such as
GDNF that support differentiation into DA cells and their survival in vivo.