Enhancement of sensorimotor behavioral recovery in hemiparkinsonian rats with intrastriatal, intranigral, and intrasubthalamic nucleus dopaminergic transplants

Abstract

One of the critical variables that influences the efficacy of clinical neural transplantation for Parkinson's disease (PD) is optimal graft placement. The current transplantation paradigm that focuses on ectopic placement of fetal grafts in the striatum (ST) fails to reconstruct the basal ganglia circuitry or normalize neuronal activity in important basal ganglia structures, such as the substantia nigra (SN) and the subthalamic nucleus (STN). The aim of this study was to investigate a multitarget neural transplantation strategy for PD by assessing whether simultaneous dopaminergic transplants in the ST, SN, and STN induce functional recovery in hemiparkinsonian rats. Forty-six female Wistar rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal pathway were randomly divided into eight groups and received lesions only or injections of 900,000 embryonic rat ventral mesencephalic cells in the (1) ST, (2) SN, (3) STN, (4) ST and SN, (5) ST, SN, and STN, (6) ST and STN, or (7) SN and STN. The number of cells transplanted was equally divided among grafting sites. Animals with two grafts received 450,000 cells in each structure, and animals with three grafts received 300,000 cells per structure. Recovery was assessed by amphetamine-induced rotations and the stepping tests. Graft survival was assessed using tyrosine hydroxylase immunohistochemistry. At 8 weeks after transplantation, simultaneous dopaminergic transplants in the ST, SN, and STN induced significant improvement in rotational behavior and stepping test scores. Intrastriatal transplants were associated with significant recovery of rotational asymmetry, whereas SN and STN transplants were associated with improved forelimb function scores. These results suggest that restoration of dopaminergic activity to multiple basal ganglia targets, such as the ST and SN, or the ST and STN, promotes a more complete functional recovery of complex sensorimotor behaviors. A multitarget transplant strategy aimed at optimizing dopaminergic reinnervation of the basal ganglia may be crucial in improving clinical outcomes in PD patients.

Fig. 1.

Timeline representing the sequence of procedures conducted during this experiment.

Fig. 2.

Representative TH-immunostained coronal tissue sections of a rat striatum (A), substantia nigra (C), and subthalamic nucleus (E) transplanted with FVM cell suspension. B, D, andF represent high-power views of the grafts. Scale bar (shown in F): A, C,E, 1000 μm; B, D,F, 400 μm.

Fig. 3.

A, Representative sagittal section of a rat brain transplanted with simultaneous intrastriatal, intranigral, and intrasubthalamic nucleus dopaminergic cell suspensions. Dense TH-IR areas representing the grafts are seen in the ST, SN, and STN. B, High-power view of the intrastriatal graft. C, High-power view of the intrasubthalamic nucleus transplants. D, High-power view of the intranigral transplants. Scale bar (shown in D):A, 1000 μm; B, C,D, 400 μm.

Fig. 4.

Rotational behavior of rats after lesion (black bars) and 4 (striped bars) and 8 weeks after transplantation (white bars) of fetal ventral mesencephalic cells. Each bar represents the mean + SD rotations per minute; *p < 0.05 compared with rotational scores after lesion.

Fig. 5.

Right and left forelimb initiation times for the stepping test before 6-OHDA lesions (black bars), after lesion (gray bars), and 8 weeks after transplantation (white bars). Each bar represents the mean + SD scores for initiation time; *p < 0.05 compared with scores for the lesion-only group 8 weeks after transplantation; **p < 0.05 compared with scores before lesions.

Fig. 6.

Right and left adjusting step scores for the stepping test before 6-OHDA lesions (black bars), after lesion (gray bars), and 8 weeks after transplantation (white bars). Each bar represents the mean + SD adjusting step scores. **p< 0.0002 compared with scores after lesion; *p < 0.01 compared with scores before lesion.