Mechanisms and time course of cell death in embryonic nigral tissue and intrastriatal transplants

Abstract: Parkinson’s disease (PD) is the second most common neurodegenerative disorder and severely affects about one in a hundred persons over the age of fifty years. In PD, there is a reduced striatal concentration of the neurotransmittor dopamine, mainly caused by a degeneration of the dopaminergic neurons in the substantia nigra. Transplantation of embryonic dopamine neurons has been developed as an alternative treatment for PD. Donor tissue dissection, mechanical dissociation, and intracerebral injection, can be divided into four phases that range from removal of embryos from the uterus to graft maturation. The transplantation procedure can be devided into four phases; i.e. embryo retrieval (phase 1); tissue dissection and dissociation (phase 2); injection of donor tissue into a recipient and a few days after injection (phase 3); and finally graft maturation (phase 4). Only a small fraction (5-20%) of the implanted dopaminergic neurons, grafted as a cell suspension into adult rats, will survive the transplantation procedure. The aim of the present thesis was to investigate the cause of cell death of the transplanted neurons during the four phases and to develop strategies to increase the neuronal survival. Several different methods were used to detect cell damage and death at various time points after tissue dissection and dissociation. We used transmission electron microscopy, vital staining, and electron paramagnetic resonance. The graft tissue was also evaluated at different time points after intrastriatal implantation, with markers for calpain activity and fragmanted DNA. The main results of the present thesis can be summarised as follows: 1) cell death occurs before implantation of the embryonic ventral mesencephalic tissue; 2) the majority of the transplanted dopaminergic neurons die within a few days after grafting; 4) addition of the antioxidant resveratrol to cell suspensions or transplantation into hypothermic hosts can result in an increased survival of embryonic mesencephalic neurons.