LIPOSOME-MEDIATED GENE-TRANSFER TO LUNG ISOGRAFTS

Objectives: Our objectives were to determine the feasibility, efficacy , and safety of in vivo and ex vivo liposome-mediated gene transfer to lung isografts, Methods: Fischer rats were divided into three main gr oups: (I) Nontransplant setting: Liposome-chloramphenicol acetyl trans ferase cDNA was intravenously injected, and lungs were harvested at di fferent time points: 2, 6, 12, and 24 hours; 2, 5, 8, and 21 days (n = 3), Chloramphenicol acetyl transferase activity was determined in lun gs, hearts, livers, and kidneys, The distribution and type of transfec ted cells were evaluated by in situ hybridization, Lung toxicity was a ssessed by arterial oxygen tension, histology, and tumor necrosis fact or-alpha levels, (2) In vivo graft transfection: Left lungs were trans planted 6 hours, 4 hours, and 15 minutes after intravenous injection a nd were assessed for chloramphenicol acetyl transferase activity and a rterial oxygen tension on postoperative day 2, (3) Ex vivo graft trans fection: Grafts were infused ex vivo with either 660 mu g (n 3) or 330 mu g (n = 3) of DNA complexed to liposomes and stored at 10 degrees C for 4 hours, Chloramphenicol acetyl transferase activity was assessed 44 hours after transplantation. Results: Transgene expression was det ected in endothelial cells, macrophages, and interstitial cells, Chlor amphenicol acetyl transferase activity was present as early as 2 hours , increased significantly between 6 hours and 8 days, and then decreas ed to minimal levels by 21 days, Chloramphenicol acetyl transferase ac tivity was greatest in donor lungs and hearts and minimal in livers an d kidneys, Arterial oxygen tension was normal in treated animals. Infl ammation was minimal, and tumor necrosis factor-alpha levels increased only sevenfold in treated animals, Conclusion: In vivo and ex vivo li posome-mediated gene transfer to lung isografts allows significant tra nsgene expression with minimal effects on graft function.