The effect of heat shock protein 70 on the survival of dopaminergic neurons : In vitro and in vivo trial with transgenic mice

Abstract

In conjunction with neural grafting, around 90% of harvested embryonic dopaminergic (DA) neurons die during the tissue preparation and the first week after implantation. Recently, we demonstrated that the degeneration in dissected cells starts already before embryo retrieval and tissue preparation. Heat shock protein 70 (HSP70) is a well-known molecular chaperone with antiapoptotic properties. We evaluated the impact of HSP70 overexpression on the survival of embryonic ventral mesencephalic DA neurons in vitro and in vivo employing neurons from HSP70 overexpressing transgenic mice and wild type control donors. We studied the cell viability with trypan blue exclusion at different time points up to 8 h after the dissociation, and the survival of grafted embryonic ventral mesencephalic DA neurons 3 weeks after the transplantation. Dissociated embryonic ventral mesencephalic cells from HSP70 overexpressing transgenic and wild-type mice were xenografted into adult immunosuppressed rats. The numbers of surviving DA neurons were evaluated stereologically 3 weeks after transplantation. Cell viability remained at over 80% in cell suspensions from HSP70-overexpressing transgenic mice although the cell numbers decreased to 50–60% at 8 h. But, there was a marked decrease in the viability (to 60–70%) and the number of cells (to 30 to 40%) in cell suspensions from wild-type mice at 8 h. Data regarding the impact of HSP70 overexpression on cell viability and survival of embryonic ventral mesencephalic cells in the host brain will also be presented. We suggest that induction of HSP70 overexpression can be a possible strategy to improve survival of the transplanted ventral mesencephalic DA neurons.