VIABILITY AND SURVIVAL OF HNT NEURONS DETERMINE DEGREE OF FUNCTIONAL RECOVERY IN GRAFTED ISCHEMIC RATS

WE recently reported behavioral improvements following intrastriatal t ransplantation of cryopreserved cultured human neuroteratocarcinoma-de rived cells (hNT neurons) in rats with cerebral ischemia induced by oc clusion of the middle cerebral artery. In the present study, the viabi lity and survival of hNT neurons were evaluated immediately prior to t he transplantation surgery and at 3 months post-transplantation in isc hemic rats. Cryopreserved hNT neurons were routinely thawed, and trypa n blue exclusion viability counts revealed 52-95% viable hNT neurons b efore transplantation. Monthly behavioral tests, starting at 1 month a nd extending to 3 months post-transplantation, revealed that ischemic animals that were intrastriatally transplanted with hNT neurons (simil ar to 40 000) and treated with an immunosuppressive drug displayed nor malization of asymmetrical motor behavior compared with ischemic anima ls that received medium alone. Within-subject comparisons of cell viab ility and subsequent behavioral changes revealed that a high cell viab ility just prior to transplantation surgery correlated highly with a r obust and sustained functional improvement in the transplant recipient . Furthermore, histological analysis of grafted brains revealed a posi tive 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 deri ved from cell lines to enhance graft-induced functional effects. (C) 1 998 Lippincott Williams & Wilkins.