Pergamon Cell Transplantation, Vol. 4, No. 1, pp. 141-154,1995 Copyright 0 1995 Elsevier Science Ltd Printed in the USA. All rights reserved 0963-6897/95 $9.50 + .OO 0963-6897(94)00048-4 Original Contribution THE INFLUENCE OF DONOR AGE ON THE SURVIVAL OF SOLID AND SUSPENSION INTRAPARENCHYMAL HUMAN EMBRYONIC NIGRAL GRAFTS THOMAS B. FREEMAN,*?’ PAUL R. SANBERG,*~$ G. MICHAEL NAUERT,~ BARBARA D. Boss,1 DENNIS SPECTOR,~ C. WARREN OLANOW,~~ AND JEFFREY H. KORDOWER# *Division of Neurosurgery, TDepartment of Pharmacology and Experimental Therapeutics, SDepartment of Psychiatry, University of South Florida, Columbia Drive, Suite 730, Tampa, FL 33606, !jWoman’s Center, Tampa, FL, THana Biologics, Inc., Alameda, CA; IIDepartment of Neurology, Mount Sinai Medical Center, New York, NY, and #Department of Neurological Sciences, Rush Presbyterian Medical Center, Chicago, IL 0 Abstract - In many species, graft survival and graft- derived behavioral recovery are affected by the embryonic donor age. We compared the ability of solid and suspension grafts of human embryonic mesencephalic dopaminergic (DA) neurons at different embryonic stages to survive intra- parenchymal transplantation into 6-OHDA lesioned immu- nosuppressed rats. Suspension grafts survived best when donor age was between postconception (PC) days 34 and 56. Transplants displayed numerous healthy tyrosine hydroxy- lase immunoreactive (TH-IR) neurons which sent extensive neuritic processes into the host striatum. Suspension grafts survived poorly when donor age was greater than 65 days. Solid implants displayed comparable viability of TH-IR neu- rons when donor age was between 44 and 65 days. No solid grafts contained TH-IR cells when donor tissue was older than 72 days. The suspension and solid methods of transplan- tation resulted in comparable survival of robust grafts, but solid grafts resulted in more intergraft variability than sus- pension grafts, particularly among the more marginal im- plants. Our results demonstrate that the upper limit for survival of human embryonic DA suspension grafts corre- lates well with the period of development of the human ni- grostriatal pathway. The “window” for donor age of solid human embryonic DA grafts appears to be extended by about 9 days in comparison to suspension grafts. These data sug- gest that the upper age limit for grafting human mesence- phalic DA neurons should be PC day 56 for suspension grafts, and PC day 65 for solid implants. Older donors are likely to produce grafts with fewer surviving DA neurons. 0 Keywords - Parkinson’s disease; Transplant; Fetal; Do- pamine; Nigra. INTRODUCTION The optimal donor age for rat nigral suspension grafts occurs after DA neurons have developed in the mes- encephalon but before the initiation of axonal exten- sion and nigrostriatal pathway formation (5,7,58,61). Similarly, donor age has been demonstrated to be im- portant for suspension graft survival in multiple other species including mouse, rabbit, pig and monkey (1,2, 4,6,13,19,22,25,30,37&I). Microdissection of the sub- stantia nigra (SN) after the period of nigrostriatal path- way formation axotomizes the mesencephalic DA neurons, presumably greatly reducing their viability following transplantation (5,7,58,59). The period of development of mesencephalic DA neurons and the nigrostriatal pathway has recently been established (29,74). The human embryonic SN be- gins development at PC week 5 l/2 to 6 l/2, and the nigrostriatal bundle begins formation at PC week 8. The sequence of events and region of development of the nigrostriatal system in man are similar to what is observed in all other species. The duration of human nigral ontogeny, however, is significantly prolonged, lasting 4 l/2 wk. Based on these ontogeny studies, it was hypothesized that human nigral suspension grafts are most likely to be viable if tissue is obtained during the period following development of the SN but be- fore the development of the nigrostriatal projections (27,29). Of note, it has been demonstrated empirically that human mesencephalic suspension grafts trans- planted into immunosuppressed rodents are viable and induce behavioral recovery when obtained up until PC week 9 (14). Fetal nigral tissue can be transplanted intraparen- chymally as either solid pieces (22,27,28,64,71,72) or as a dispersed suspension of cells (5,7,8,58). The “win- ACCEPTED 9/6/94. 141 ‘To whom correspondence should be addressed.