Walking pattern analysis after unilateral 6-OHDA lesion and transplantation of foetal dopaminergic progenitor cells in rats

Functional sensorimotor recovery after transplantation of mesencephalic dopaminergic (DAergic) neurons has been well documented in the rat 6-hydroxydopamine (6-OHDA) model of Parkinson's disease. However, the functional restoration of more specific gait-related patterns such as skilled walking, balance, and individual limb movements have been insufficiently studied. The purpose of this study was to investigate the behavioural effects of intrastriatal DA grafts on different aspects of normal and skilled walking in rats following unilateral 6-OHDA lesions of the medial forebrain bundle. Rats were subjected to drug-induced rotation, detailed footprint analysis, and assessment of skilled walking in the ladder rung walking test prior and after the transplantation of E14 ventral mesencephalon-derived progenitor cells. Good DAergic graft survival, as revealed by immunohistochemistry, was accompanied by a compensation of drug-induced rotational asymmetries. Interestingly, the analysis of walking patterns displayed a heterogeneous graft-induced response in skilled and non-skilled limb use. Grafted animals made fewer errors with their contralateral limbs in skilled walking than the sham-transplanted rats, and they improved their ipsi- and contralateral limb rotation. However, the parameter distance between feet showed a delayed recovery, and the stride length was not affected by the DA grafts at all. These findings indicate that ectopic intrastriatal transplantation of E14 ventral mesencephalon-derived cells promotes recovery of gait balance and stability, but does not ameliorate the shuffling gait pattern associated with 6-OHDA lesions. A full restoration of locomotor gait pattern might require a more complete and organotypic reconstruction of the mesotelencephalic DAergic pathway.