Adenoviral gene transfer to the neonatal rat pulmonary circulation

BACKGROUND: Gene delivery to the pulmonary circulation has been studied in adult animals, but has not been extensively investigated in neonates. METHODS: We tested the ability of recombinant, replication-defective adenovirus to transduce the pulmonary circulation when delivered by percutaneous ventricular puncture. Five-day-old rat pups were injected with 10(7) to 10(10) particles (approximately 10(5) to 10(8) pfu) in 30 micro l total volume. RESULTS: Using RT-PCR, we detected transgene expression in both lung and liver at all dosages. However, whereas only 1/6 pups injected with 10(7) particles had detectable expression, 8/9 pups in the two highest dose groups had detectable expression. In the highest dose group expression was approximately 5-fold greater in lung than liver, though in the lower dose groups no difference between lung and liver was found. Expression decreased by only 25% from day 4 through the last time point at day 28 in lung, whereas liver expression was undetectable in 7 of 9 samples on day 28. Histopathological examination demonstrated expression both within the media of large arteries and in small, peripheral arteries and capillaries, with a concentration of expression in the most distal areas of both the lungs and liver. No evidence of inflammation was seen. CONCLUSIONS: We conclude that the neonatal pulmonary circulation can be effectively transduced using systemic adenoviral vector injection, has more sustained expression than liver, and may be a target for therapeutic gene delivery.