Potential Use of Embryonic Stem Cells for the Treatment of Mouse Parkinsonian Models: Improved Behavior by Transplantation of In Vitro Differentiated Dopaminergic Neurons from Embryonic Stem Cells

Abstract

Background and Aims. The purpose of the present study was to examine the efficacy of transplantation of mouse embryonic-stem-(ES)-cell-derived tyrosine hydroxylase-positive (TH+) cells into Parkinsonian mice using behavioral tests and immunohistochemical evaluation.Methods. Undifferentiated ES cells carrying the enhanced green fluorescent protein (EGFP) gene were differentiated into a cell population containing TH+ neurons using a five-step in vitro differentiation method. These ES-cell-derived cells were used as allografts in Parkinsonian mice, made by administering injections of 6-hydroxydopamine (6-OHDA). Fifteen hemiparkinsonian mice were divided into three groups. Four weeks after 6-OHDA injection, mice in groups 1, 2, and 3 received phosphate-buffered saline, 1 × 104 graft cells, and 1 × 105 graft cells, respectively, into their dopamine-denervated striata.Results. Improved rotational behavior was observed in the graft-transplanted groups (groups 2 and 3) 2 weeks after transplantation. Mice in group 2 displayed a continuous maintenance of reduced rotational behavior, while those in group 3 showed ipsilateral rotation toward the lesioned side at 4, 6, and 8 weeks after transplantation. Tumor formation was observed in one mouse in group 3. TH+ cells were found at the grafted sites 8 weeks after transplantation in mice in groups 2 and 3, some of which were immunopositive to GFP, demonstrating the presence of dopaminergic neurons derived from the ES cells.Conclusion. Transplantation of in vitro differentiated ES cells changed rotational behavior in Parkinsonian mice. Our results suggest the potential availability of ES cells for Parkinson's disease.