Effects of hibernation or cryopreservation on the survival and integration of striatal grafts placed in the ibotenate-lesioned rat caudate-putamen.

Tissue storage prior to intracerebral transplantation would represent a major advantage when conducting clinical transplantation trials in that the procurement of the embryonic donor tissue and the timing of neurosurgery could be planned more efficiently. In the present study, the effects of storing rat embryonic striatal tissue at either +4 degrees C or below freezing temperature prior to grafting to the adult striatum, were assessed with regard to transplant survival, morphology and integration. Eleven days following a unilateral injection of ibotenic acid into the head of the caudate-putamen, a control group of rats received grafts of striatal primordium prepared immediately after dissection from rat embryos (embryonic day 16). A second group of rat embryonic striatal tissue was stored at 4 degrees C (hibernation) for 5 days and then transplanted. A third group of the striatal donor tissue was cryopreserved in liquid nitrogen for 5 days before implantation surgery. Six to seven weeks following transplantation surgery, the grafts were analysed in brain sections processed for acetylcholinesterase histochemistry, DARPP-32 (dopamine and cyclic AMP regulated phosphoprotein with a molecular weight of 32 kDa) and tyrosine hydroxylase (TH) immunocytochemistry. The mean total graft volume and the relative size of the AChE-positive regions were not significantly different between the three groups. Striatal-specific graft regions, positively stained for AChE and DARPP-32, generally exhibited TH immunoreactivity, suggesting that they had received dopaminergic afferents from the host brain. We conclude that embryonic rat striatal tissue can be cryopreserved or hibernated over 5 days without significant impairment in the yield of striatal neurons following intrastriatal implantation and without markedly affecting transplant morphology.