BACKGROUND: Total saponins of Panax ginseng (TSPG) exhibits neuroprotection against Parkinson's disease in the substantia nigra.OBJECTIVE: To investigate the effects of TSPG on human embryonic neural stem cells (NSCs) proliferation and differentiation into dopaminergic neurons using in vitro studies, and to observe NSC differentiation in a mouse model of Parkinson's disease, as well as behavioral changes before and after transplantation.DESIGN, TIME AND SETTING: In vitro neural cell biology trial and in vivo randomized, controlled animal trial were performed at the Institute of Basic Medical Sciences, Chongqing Medical University between September 2004 and December 2007.MATERIALS: TSPG (purity > 95%) was isolated, extracted, and identified by Chongqing Academy of Chinese Materia Medica. Recombinant human basic fibroblast growth factor (bFGF)and recombinant human epidermal growth factor (EGF) were purchased from PeproTech, USA. A total of 25 C57/BL6J mice, aged 18-20 weeks were included. Twenty were used to establish a Parkinson's disease model with i.p. injection of MPTP (1-methyl-4-phenyl-1, 2, 3,6-tetrahydropyridine) and TSPG alone or combined with interleukin-1 (IL-1)-treated NSCs prior to transplantation into the corpus striatum. The remaining five mice were pretreated for 3 days with TSPG prior to MPTP injection, serving as the TSPG prevention group.METHODS: Primary NSCs were isolated, cultured and purified from embryonic cerebral cortex.Immunocytochemistry was employed to detect specific antigen expression in the NSCs. In vitro experiment: (1) to induce proliferation, NSCs were treated with TSPG, EGF+bFGF, or TSPG+EGF+bFGF, respectively; (2) to induce dopaminergic neuronal differentiation, NSCs were treated with TSPG, IL-1, or TSPG+IL-1, respectively.MAIN OUTCOME MEASURES: In vitro experiment: the effects of TSPG on NSCs proliferation were evaluated with flow cytometry and M'IT assay. Tyrosine hydroxylase expression was determined by immunocytochemistry assay to observe effects of TSPG on dopaminergic neuronal differentiation. In vivo experiment: differentiation of grafted NSCs in the mouse brain was determined by immunohistochemical staining. Behavioral changes were evaluated by spontaneous activity frequency, memory function, and score of paralysis agitans.RESULTS: (1) NSCs were cultured and passaged for more than three passages.Immunocytochemistry revealed positive nestin staining, as well as neurofilament protein and glial fibrillary acidic protein. (2) TSPG significantly increased NSC proliferation, in particular when combined with EGF and bFGF, which was twice as effective as FGF or bFGF alone. TSPG also induced dopaminergic differentiation in NSCs, in particular when TSPG was added together with IL-1, resulting in an effect five times greater than that of IL-1 alone. (3) At day 30 following transplantation, most NSCs in the TSPG prevention group differentiated into dopaminergic neurons, and the scores of paralysis agitans, spontaneous activity, and memory function were significantly increased compared with TSPG alone or TSPG+IL-1 groups (P < 0.05).CONCLUSION: TSPG stimulated NSC proliferation, in particular when combined with FGF and bFGF. TSPG significantly induced dopaminergic neuronal differentiation of NSCs, and the effect was greater when combined with IL-1. In addition, TSPG greatly improved behavior in the Parkinson's disease mouse model following NSC transplantation. Following NSC transplantation,TSPG pretreatment exhibited superior efficacy over either TSPG alone or TSPG in combination with IL-1, in terms of behavioral improvements in the Parkinson's disease mouse model.