CNS-DERIVED NEURAL PROGENITOR CELLS FOR GENE-TRANSFER OF NERVE GROWTH-FACTOR TO THE ADULT-RAT BRAIN - COMPLETE RESCUE OF AXOTOMIZED CHOLINERGIC NEURONS AFTER TRANSPLANTATION INTO THE SEPTUM

A CNS-derived conditionally immortalized temperature-sensitive neural progenitor (CINP) cell line was used to generate NGF-secreting cells s uitable for intracerebral transplantation. The cells were transduced b y repeated retroviral infection, using a vector containing the mouse N GF cDNA under the control of the LTR promoter. Subcloning at the permi ssive temperature (33 degrees C) identified a highly NGF-secreting clo ne (NGF-CINP), which contained multiple copies of the transgene and re leased NGF at a rate of 2 ng/hr/10(5) cells in vitro, both at 33 and 3 7 degrees C, which was approximately 1 order of magnitude higher than what was possible to achieve in the heterogeneously infected cell cult ures. After transplantation to the brain, the NGF-CINPs differentiated into cells with a predominant glia-like morphology and migrated for a distance of 1-1.5 mm from the implantation site into the surrounding host tissue, without any signs of overgrowth and tumor formation. Graf ts of NGF-CINP cells implanted into the septum of adult rats with comp lete fimbria-fornix lesion blocked over 90% of the cholinergic cell lo ss in the medial septum and grafts placed in the intact striatum induc ed accumulation of low-affinity NGF receptor positive fibers around th e implantation site. Expression of the NGF transgene in vivo was demon strated by RT-PCR at 2 weeks after grafting. It is concluded that the immortalized neural progenitors have a number of advantageous properti es that make them highly useful experimental tools for gene transfer t o the adult CNS.