Time course of apoptotic cell death within mesencephalic cell suspension grafts: Implications for improving grafted dopamine neuron survival

The vast majority (congruent to 90%) of embryonic mesencephalic dopamine (D A) neurons die following transplantation to the striatum. Recent reports in dicate that at least a subpopulation of grafted cells undergo apoptotic cel l death at early times following implantation. This study examines the temp oral pattern and magnitude of apoptotic cell death following the implantati on of mesencephalic cell suspension grafts Two techniques, a modified termi nal deoxynucleotide-mediated nucleotide end labeling (TUNEL) technique and cresyl violet staining, are used to assess apoptotic cell death by detectio n of its biochemical and morphological identifiers, respectively. Male, Fis cher 344 rats were examined at 1, 4, 7, and 28 days following implantation of embryonic day 14 (E14) ventral mesencephalic cells to the DA-denervated striatum. Results indicate that the overwhelming majority of apoptotic cell death occurs within the first 7 days after transplantation. However, the i mpact of the apoptosis that occurs over the first week following grafting o nly appears to limit grafted tyrosine hydroxylase-immunoreactive (THir) neu ron survival during the first 4 days. No significant differences between th e survival rates of THir neurons at 4 days after grafting and at 28 days af ter grafting were found. Therefore, it appears that the critical interval d uring which an estimated 90% of grafted DA neurons die is during the first 4 days postimplantation and that a major contributor to this cell death is apoptosis. (C) 2000 Academic Press.