IN-VIVO GENE-TRANSFER BY INTRAVENOUS ADMINISTRATION OF STABLE CATIONIC LIPID DNA COMPLEX

Purpose. A stable cationic lipid/DNA complex has been developed for in vivo gene transfer. The formulation capitalizes on a previously descr ibed procedure to obtain stable lipid/DNA complexes for in vitro gene transfer (1). Methods. Conditions for DNA/lipid complex formation were modified to yield a DNA concentration of 1 mg/ml. Heat stable alkalin e phosphatase (AP) under a CMV promoter was used as a reporter gene. R esults. The resulting complex was completely insensitive to serum inac tivation. Tail vein injection of a 80 mu g DNA into Balb C mice yielde d significant levels of reporter enzyme activity in the lung, heart, s pleen, muscle, and liver. Less AP activity was observed in the kidney. No AP activity was observed in blood, bone marrow or brain. A titrati on of the lipid (DOSPA) to DNA-nucleotide ratio showed the optimal mol ar ratio for in vivo gene transfer to be 1/1. Using this ratio in a do se response study showed approximately 80 mu g of DNA/mouse yielded th e highest level of gene expression. Using this dose at a 1/1 lipid to DNA nucleotide ratio, the time course for alkaline phosphatase activit y was determined. Maximal AP activity was observed 24 hours after inje ction for all tissues. By day 5, the activity dropped approximately 10 fold for all tissues. By day 7, residual activity was detected in the lung, heart, and muscle. Histology of the lung showed both interstiti al and endothelial cells to be transfected. In all other tissues, howe ver, endothelial cells were the only transfected cell type. Conclusion s. These results demonstrate that reformulation of an existing cationi c lipid can result in the formation of a stable lipid/DNA complex, whi ch is able to reproducibly transfect lung, heart, spleen, and liver up on intravenous administration.