EXPRESSION OF HUMAN GROWTH-HORMONE FUSION GENES IN CULTURED LUNG ENDOTHELIAL-CELLS AND IN THE LUNGS OF MICE

We sought to develop genetic therapy for acute lung diseases by introd ucing genes into lung cells in vivo that were only transiently express ed. To that end, we introduced a gene encoding a physiologically relev ant secreted human protein into bovine lung endothelial cells in cultu re and into the lungs of mice using the technique of lipofection. We e xposed cultured endothelial cells to a plasmid containing the coding r egion for human growth hormone (hGH) driven by a metallothionein (MT) promoter. In cells lipofected with the plasmid containing the MT promo ter, expression of the hGH gene in medium was low (peak = 30 ng hGH/24 h/60-mm dish), but expression was markedly increased by addition of e ither dexamethasone (peak = 91) or cadmium (peak = 120). Lipofection w ith the same construct except a thymidine kinase promoter showed no ca dmium response. We gave mice 5,000 ppm ZnSO4 in their drinking water a nd 24 h later injected intravenously plasmid containing the MT promote r complexed to liposomes. Mice were killed 1, 3, and 5 days after inje ction, and hGH production by minced lung, liver, and kidneys was deter mined in vitro. Neither kidneys nor liver produced detectable hGH. How ever, hGH was produced by the lungs, beginning on day 1, peaking on da y 3 (approximately 1.0 ng hGH/24 h/g tissue), and declining by day 5. Lungs from mice injected either with DNA alone or with liposome alone did not produce hGH. mRNA specific for hGH was demonstrated in the lun gs by polymerase chain reaction amplification of cDNA followed by agar ose gel electrophoreses. We conclude that a functioning foreign gene e ncoding a physiologically relevant secreted human protein can be intro duced into lung endothelium in culture and into the lungs of intact an imals; expression of the gene can be controlled by selection of promot er regions. In vivo transient transfection of lung cells could make ge ne therapy applicable to a wide variety of diseases of the lungs, incl uding diseases not due primarily to genetic abnormalities.