This study identified the organ and cellular distribution of cationic liposome-DNA complexes injected intravenously into CD-1 mice for gene delivery. DOTIM-cholesterol liposomes were labeled with the fluorescent dye CM-Dil and complexed with plasmid DNA encoding the chloramphenicol acetyltransferase reporter gene. The distribution of the complexes was examined in 29 organs and tissues by fluorescence, confocal, and electron microscopy from 5 min to 24 h after injection. The complexes formed clusters in blood, which were cleared within 20 min. Complexes visible by fluorescence microscopy were taken up by endothelial cells, leukocytes, and macrophages and did not leave the vasculature except in the spleen. At 5 min, the complexes formed a patchy coating on the endothelial surface, but by 4 h, they were internalized into endosomes and lysosomes in organ- and vessel-specific patterns. Uptake by capillary endothelial cells was greatest in the lung, ovary, and anterior pituitary, less in muscle and the heart, and nearly absent in the brain and pancreatic islets. In lymph nodes and intestinal Peyer's patches, the uptake was sparse in capillaries but abundant in high endothelial venules. In the liver and spleen, most of the uptake was in Kupffer cells and macrophages. Measurements of chloramphenicol acetyltransferase reporter gene expression were generally consistent with the pattern of uptake by endothelial cells. The uptake and gene expression were accompanied by a decrease in circulating leukocytes and platelets. Overall, our results showed that the complexes were internalized by endothelial cells in organ- and vessel-specific patterns that did not match any previously identified properties of the microvasculature. The unusual distribution of endothelial cell uptake may be explained by a heterogeneously distributed membrane receptor for which the complexes are ligands.

We compared the efficacy of gene transfer in vitro and in CFTR to mice and rats. We observed a lack of positive correvivo using various formulations of DNA-lipid complexes lation between those DNA-EDMPC formulations that delivbased on the novel cationic lipid EDMPC (1,2-dimyristoylered DNA most efficiently in vitro and those that worked best sn-glycero-3-ethylphosphocholine, chloride salt). In vitro in vivo. Intralobar DNA delivery to rodents mediated by studies analyzed delivery of marker genes to four estab-EDMPC was efficient. The high level of gene delivery by lished cell lines, including two of pulmonary origin. The in DNA-EDMPC formulations demonstrates that efficient lipidvivo analysis used intralobar delivery of marker genes and mediated gene transfer to the lung is possible.

As the sequencing of the human genome proceeds, the need for a new screen for in vivo function is becoming apparent. Many investigators are turning to various transgenic models as a means of studying function. However, these approaches are very time consuming, with a transgene-expressing mouse model often taking months to establish. We have developed an efficient system for delivering genes in vivo, which allows the gene product to be studied as early as 24 h after introduction into the mouse model. The delivery system employs a novel cationic lipid, 1-[2-(9-(Z)-octadecenoyloxy)ethyl]-2-(8-(Z)-heptadecenyl)-3- (hydroxyethyl)imidazolinium chloride (DOTIM), and a neutral lipid, cholesterol, complexed with an expression vector containing the reporter gene chloramphenicol acetyl transferase (CAT). After a single intravenous injection of these complexes, several tissues were seen to express the transgene. High, persistent expression in the vascular endothelial cells in the mouse lung was obtained. Delivery of DNA in vivo has been evaluated by quantitative polymerase chain reaction and protein expression by CAT activity assays. In vivo studies showed reproducible expression in more than 500 mice injected via the tail vein. An early peak of expression was followed by lower, but sustained, expression for > 50 days. Transgene expression of CAT could also be identified by immunohistochemistry staining in mouse lung and appeared to be located within the capillaries. The pattern of in vivo expression could be modulated and targeted to specific organs by altering the lipid-DNA formulation. New expression vectors with altered introns and polyadenylation sites further improved expression. The expression reported here may be sufficient in magnitude, duration, and flexibility to be an attractive alternative, in some cases, to establishing transgenic animals by stable gene transfer.