A POWERFUL NONVIRAL VECTOR FOR IN-VIVO GENE-TRANSFER INTO THE ADULT MAMMALIAN BRAIN - POLYETHYLENIMINE

Nonviral gene transfer into the central nervous system (CNS) offers th e prospect of providing safe therapies for neurological disorders and manipulating gene expression for studying neuronal function, However, results reported so far have been disappointing, We show that the cati onic polymer polyethylenimine (PEI) provides unprecedentedly high leve ls of transgene expression in the mature mouse brain, Three different preparations of PEI (25-, 50-, and 800-kD) were compared for their tra nsfection efficiencies in the brains of adult mice, The highest levels of transfection were obtained with the 25-kD polymer, With this prepa ration, DNA/PEI complexes bearing mean ionic charge ratios closest to neutrality gave the best results, Under such conditions, and using a c ytomegalovirus (CMV)-luciferase construction, we obtained up to 0.4 10 (6) RLU/mu g DNA (equivalent to 0.4 ng of luciferase), which is close to the values obtained using PEI to transfect neuronal cultures and th e more easily transfected newborn mouse brain (10(6) RLU/mu g DNA), Wi despread expression (over 6 mm(3)) of marker (luciferase) or functiona l genes (belt) was obtained in neurons and glia after injection into t he cerebral cortex, hippocampus, and hypothalamus. Transgene expressio n was found more than 3 months post-injection in cortical neurons, No morbidity was observed with any of the preparations used, Thus, PEI, a low-toxicity vector, appears to have potential for fundamental resear ch and genetic therapy of the brain.