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We recently reported behavioral improvements following intrastriatal transplantation of cryopreserved cultured human neuroteratocarcinoma-derived cells (hNT neurons) in rats with cerebral ischemia induced by occlusion of the middle cerebral artery. In the present study, the viability and survival of hNT neurons were evaluated immediately prior to the transplantation surgery and at 3 months post-transplantation in ischemic rats. Cryopreserved hNT neurons were routinely thawed, and trypan blue exclusion viability counts revealed 52-95% viable hNT neurons before transplantation. Monthly behavioral tests, starting at 1 month and extending to 3 months post-transplantation, revealed that ischemic animals that were intrastriatally transplanted with hNT neurons (approximately 40000) and treated with an immunosuppressive drug displayed normalization of asymmetrical motor behavior compared with ischemic animals that received medium alone. Within-subject comparisons of cell viability and subsequent behavioral changes revealed that a high cell viability just prior to transplantation surgery correlated highly with a robust and sustained functional improvement in the transplant recipient. Furthermore, histological analysis of grafted brains revealed a positive correlation between number of surviving hNT neurons and degree of functional recovery. In concert with similar reports on fetal tissue transplantation, we conclude that high cell viability is an important criterion for successful transplantation of cryopreserved neurons derived from cell lines to enhance graft-induced functional effects.

The aim of this study was to explore whether brain-derived neurotrophic factor (BDNF) can improve neuronal survival in cell cultures of rat dentate gyrus subjected to a hypoglycaemic insult. Glucose deprivation for 15 h caused severe neuronal loss (about 70%). BDNF added either 24 h before or 4 h after onset of hypoglycaemia completely protected granule cells against this insult-induced damage. Nerve growth factor (NGF) had similar effects. These findings support the hypothesis that the rapid upregulation of BDNF mRNA in dentate granule cells after brief periods of hypoglycaemic coma and other insults is a local protective mechanism.