Small poly-L-lysines improve cationic lipid-mediated gene transfer in vascular cells in vitro and in vivo

The potential of two small poly-L-lysines ( sPLLs), low molecular
weight sPLL ( LMW-L) containing 7 - 30 lysine residues and L18 with
18 lysine repeats, to enhance the efficiency of liposome-mediated
gene transfer ( GT) with cationic lipid DOCSPER {[}1,3-
dioleoyloxy- 2-( N-5-carbamoyl-spermine)-propane] in vascular
smooth muscle cells ( SMCs) was investigated. Dynamic light
scattering was used for determination of particle size. Confocal
microscopy was applied for colocalization studies of sPLLs and
plasmid DNA inside cells. GT was performed in proliferating and
quiescent primary porcine SMCs in vitro and in vivo in porcine
femoral arteries. At low ionic strength, sPLLs formed small
complexes with DNA ( 50 100 nm). At high ionic strength, large
complexes ( 11 mu m) were observed without any significant
differences in particle size between lipoplexes ( DOCSPER/ DNA) and
lipopolyplexes ( DOCSPER/ sPLL/ DNA). Both sPLLs were colocalized
with DNA inside cells 24 h after transfection, protecting DNA
against degradation. DOCSPER/ sPLL/ DNA formulations enhanced GT in
vitro up to 5- fold, in a porcine model using local periadventitial
application up to 1.5- fold. Both sPLLs significantly increased
liposome- mediated GT. Poly-L-lysine L18 was superior to LMW-L
since it enabled maximal GT at a 10-fold lower concentration. Thus,
sPLLs may serve as enhancers for GT applications in SMCs in vitro
and in vivo using local delivery. Copyright (c) 2007 S. Karger AG,
Basel.