Nonviral glial cell-derived neurotrophic factor gene transfer enhances survival of cultured dopaminergic neurons and improves their function after transplantation in a rat model of Parkinson's disease

Transplantation of dopaminergic fetal mesencephalic tissue into the striatu m is currently being developed for treatment of patients with advanced Park inson's disease. Ethical concerns regarding the use of human fetal tissue, and the limited availability as well as poor survival and differentiation o f dopaminergic neurons after transplantation have reduced the extent and ou tcome of this approach so far. With the purpose of finding means to increas e the yield of dopaminergic neurons in transplants, and to reduce the amoun t of fetal tissue needed for each transplanted patient, we transfected rat fetal ventral mesencephalic (VM) tissue grown as organotypic free-floating roller tube (FFRT) cultures with a vector encoding human glial cell-derived neurotrophic factor (hGDNF), For transfer of an episomal expression vector (pRep7-GDNF8) a nonviral, nonliposomal cationic transfection technique was applied and optimized. Recombinant hGDNF expression resulted in a higher n umber of TH-positive neurons in the cultures as measured 6 days after trans fection, Ventral mesencephalic cultures expressing hGDNF were then grafted into the striatum of unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats. Grafting of genetically modified VM cultures resulted in earlier functiona l recovery compared with grafting nontransfected cultures. We conclude that organotypic free-floating roller tube cultures can be successfully transfe cted to produce hGDNF with effects on TH-expressing neurons in vitro and fu nctional effects after grafting in a rat Parkinson's disease model.