Lipid mediated gene delivery in the adult rat brain: quantitative analysisof expression

Gene transfer into the adult brain is potentially an attractive alternative to commonly employed transgenic approaches. DNA-lipid complexes have been used to obtain brain gene transfer, but data are sparse to indicate to what extent this results in significant expression of functional protein. Here, an expression construct encoding the functional reporter, chloramphenicola cetyl-transferase (CAT), was complexed to a novel biodegradable lipid, and delivered into the rat brain. CAT-activity was assayed in tissue extracts t o allow a precise quantitation of functional enzyme protein. Following bila teral intraventricular (i.c.v.) injection, robust enzyme activity was found in all brain regions studied, peaking at 4 weeks. Other routes of administ ration, e.g. intra-parenchymal injection or chronic infusion of complexes, resulted in marginal or no activity. Presence of CAT mRNA and plasmid DNA i n tissue extracts was confirmed at 4 weeks post i.c.v. administration. In a greement with previous studies, labelled lipid-DNA complexes were mainly fo und in the ventricular ependyma. Present data support the feasibility of li pid mediated brain gene transfer, and outline some of its anatomical and te mporal limitations. (C) 1999 Elsevier Science Ltd. All rights reserved.