Multiple components in serum contribute to hepatic transgene expression by lipoplex in mice.

Background: Interaction of cationic liposome/plasmid DNA complex (lipoplex) with serum was not a limiting factor for in vivo transfection. After intraportal injection of lipoplex, hepatic transgene expression was enhanced by interaction with serum in mice. In the present study, we analyzed the mechanism of enhanced hepatic transgene expression of lipoplex by interaction with serum components.

Methods: Lipoplexes were incubated with several serum components for 5  min at 37  ° C before administration. Transfection efficiency of lipoplexes was measured 6  h after intraportal injection of lipoplex in mice.

Results: Depletion of divalent cation from serum decreased hepatic transgene expression. The addition of calcium ion to divalent cation-depleted serum restored transgene expression. Heat-inactivated serum and bovine serum albumin diminished the enhancing effect of serum on hepatic transgene expression. On the other hand, removal of anionic proteins from serum using an anion-exchanging column was critical for the enhancing effect of serum on transgene expression. Among the serum components tested, fibronectin and complement component C3 enhanced hepatic transgene expression.

Conclusions: Hepatic transgene expression by lipoplex was enhanced by interaction with multiple components in serum. Interaction of lipoplex with serum could be an important factor for successful in vivo gene transfer. Hence, the information obtained in the present study is valuable for the future development of effective gene carriers.