Promotion of survival and regeneration of nigral dopamine neurons in a ratmodel of Parkinson's disease after implantation of embryonal carcinoma-derived neurons genetically engineered to produce glial cell line-derived neurotrophic factor

Object. The P19 embryonal carcinoma-derived cell line consists of undiffere ntiated multipotential cells, which irreversibly differentiate into mature neurons after exposure to retinoic acid (RA), In the present study, the aut hors genetically engineered P19 cells to produce glial cell line-derived ne urotrophic factor (GDNF), and grafted the cells in a rat model that had bee n rendered parkinsonian. Methods. Undifferentiated P19 cells were grown in vitro and transduced with GDNF complementary DNA. The level of GDNF released from the transduced cel ls was measured using an enzyme-linked immunosorbent assay, and its neurotr ophic activities were assessed by testing the effects on rat embryonic dopa mine (DA) neurons in culture. After having been exposed to RA for 48 hours and allowed to differentiate into postmitotic neurons, the GDNF gene-transd uced cells were implanted into the midbrain of immunosuppressed rats. A uni lateral nigrostriatal lesion was then induced by intrastriatal infusions of 6-hydroxydopamine. Immunohistochemical analyses performed 4 weeks postgraf ting revealed that the GDNF-producing cells expressed several neuronal mark ers without evidence of overgrowth. The grafts expressed GDNF protein and p revented the death of nigral DA neurons. Furthermore, the GDNF-producing ce lls implanted 4 weeks after nigrostriatal lesions restored the expression o f tyrosine hydroxylase in injured DA neurons and induced their dendritic sp routing. Conclusions. The results indicate that the P19 cell line transduced with th e GDNF gene can stably secrete functional levels of GDNF, even after being converted to postmitotic neurons. Because it is has been established that G DNF exerts trophic effects on DA neurons, the means currently used to deliv er GDNF into the brain could be a viable strategy to prevent the death of n igral DA neurons in cases of Parkinson's disease.