HUMAN FETAL ASTROCYTES AS AN EX-VIVO GENE-THERAPY VEHICLE FOR DELIVERING BIOLOGICALLY-ACTIVE NERVE GROWTH-FACTOR

The therapeutic use of neurotrophic factors for neurodegenerative dise ases is promising, however, optimal methods for continuous delivery of these substances to the human central nervous system (CNS) remains pr oblematic. One approach would be to graft genetically engineered human cells that continuously secrete high levels of a biologically produce d and processed neurotrophic factor. This ex vivo gene therapy approac h has worked well in animal models of neurodegenerative diseases using a variety of nonneuronal ceh types to deliver the transgene. In our s tudies, we have been investigating the potential of astrocytes, a cell type normally present in the CNS, as a vehicle for ex vivo gene thera py. Here, we demonstrate that astrocytes in the human fetal cortex can be isolated and efficiently infected with an amphotropic retrovirus h arboring mouse beta-nerve growth factor (NGF). These transduced astroc ytes express high levels of NGF mRNA and secrete bioactive NGF protein as demonstrated by stimulation of neurite outgrowth from adrenal chro maffin cells. NGF ELISA showed that these astrocytes secrete NGF prote in at a rate of 41 ng/day per 10(5) cells after 2 weeks in vitro, wher eas NGF is undetectable ire medium conditioned by normal astrocytes. T hese data suggest that human fetal astrocytes can be used for deliveri ng biologically produced neurotrophic factors to the human CNS.