Exercise Promotes Neurite Extensions from Grafted Dopaminergic Neurons in the Direction of the Dorsolateral Striatum in Parkinson’s Disease Model Rats

BACKGROUND: Cell transplantation is expected to be a promising treatment for Parkinson’s disease (PD), in which re-innervation of the host striatum by grafted dopamine (DA) neurons is essential. In particular, the dorsolateral part of the striatum is important because it is the target of midbrain A9 DA neurons, which are degenerated in PD pathology. The effect of exercise on the survival and maturation of grafted neurons has been reported in several neurological disease models, but never in PD models. OBJECTIVE: We investigated how exercise influences cell transplantation for PD, especially from the viewpoint of cell survival and neurite extensions. METHODS: Ventral mesencephalic neurons from embryonic (E12.5) rats were transplanted into the striatum of adult 6-OHDA-lesioned rats. The host rats then underwent treadmill training as exercise after the transplantation. Six weeks after the transplantation, they were sacrificed, and the grafts in the striatum were analyzed. RESULTS: The addition of exercise post-transplantation significantly increased the number of surviving DA neurons. Moreover, it promoted neurite extensions from the graft toward the dorsolateral part of the striatum. CONCLUSIONS: This study indicates a beneficial effect of exercise after cell transplantation in PD.