Transgene expression in mouse airway epithelium by aerosol gene therapy with PEI-DNA complexes

Gene therapy targeted at the respiratory epithelium holds therapeutic poten tial for diseases such as cystic fibrosis and alpha anti-trypsin deficiency . A variety of approaches such as intranasal or intratracheal instillation and aerosol delivery have been utilized to target genes to the airways. Pol yethylenimine (PEI), a linear or branched polycationic polymer, has been us ed for delivery of genes to various organs. In this study, using fluorescei n isothiocyanate (FITC)-labeled branched PEI, we initially examined the loc alization of PEI in the lungs after aerosol delivery to Balb/C mice. Furthe r, after aerosol delivery of PEI-CAT DNA, in situ immunostaining for chlora mphenicol acetyl transferase (CAT) protein was used to localize the transge ne expression within the lungs. Immunohistochemistry for CAT, as well as lo calization of FITC-labeled PEI, revealed that after aerosol delivery, the P EI-DNA complexes deposit and subsequently transfect most of the epithelial cells in the conducting airways (including the peripheral airways). High le vels of CAT were detected at 24 h after aerosol exposure and significant CA T expression was detected in the lungs up to 28 days after a single aerosol exposure. The data suggest that aerosol delivery of PEI-DNA complexes coul d be effective for the treatment of pulmonary diseases such as cystic fibro sis and cu-l anti-trypsin deficiency.