LIPOSPERMINE-BASED GENE-TRANSFER INTO THE NEWBORN MOUSE-BRAIN IS OPTIMIZED BY A LOW LIPOSPERMINE DNA CHARGE RATIO

Nonviral, plasmid-based gene transfer into somatic tissues offers the prospect of various simple and safe therapeutic possibilities as well as applications in fundamental research, Although cationic lipids disp lay efficient transfection activities in many in vitro systems, only l ow success rates using these vectors in vivo have been reported, We su cceeded in defining conditions providing high levels of in vivo transf ection in the brains of newborn mice, Our hypothesis was that conditio ns favorable for in vitro transfection (highly positively charged part icles) were unlikely to be appropriate for in vivo conditions, When us ing the cationic lipid dioctadecylamido glycylspermine (Transfectam, D OGS) with a cytomegalovirus (CMV)-luciferase reporter gene, the best l evels of transfection were obtained when using a low ratio of positive charges (supplied by the DOGS) to negative charges (carried by the DN A), Moreover, addition of the neutral lipid dioleoylphosphatidyl ethan olamine (DOPE) significantly enhanced transfection, Expression of the transgene diminished over time, independently of lipopolysaccharide co ntent of the plasmid preparation used, This suggests that either a mit otic population of cells was preferentially transfected, or that promo ter silencing was occurring, Histological examination of the spatial d istribution of a P-galactosidase-expressing transgene showed numerous groups of transfected cells both within the striatal parenchyma and in the: paraventricular area, Thus, DNA-lipid complexes bearing overall charges close to neutrality open promising possibilities for modulatin g gene expression in the developing central nervous system and for the rapy in the brain.