Assessment of the Efficacy of <i>In Vivo</i> CFTR Protein Replacement Therapy in CF Mice

Abstract

Cystic Fibrosis (CF) is caused by mutations in the CF gene that lead, for the most part, to mislocalization of the protein product, the cystic fibrosis transmembrane conductance regulatory (CFTR). CFTR is a chloride channel normally situated in the apical membrane of epithelial cells where it contributes to transepithelial ion transport. In this study we demonstrated the feasibility of in vivo transfer of purified CFTR protein via phospholipid liposomes into the apical membrane of nasal epithelia of CFTR knockout mice. Membrane incorporation of immunogold-labeled CFTR could be visualized by electron microscopy and correction of CF-related defects in ion transport measured by nasal potential difference (PD) measurements in about one-third of the animals treated. Although these initial results are promising, effectiveness of this therapeutic approach appears to be limited by the inefficient incorporation of CFTR into the apical epithelial cell membrane. Cystic fibrosis results when CFTR (the cystic fibrosis transmembrane conductance regulator) protein is absent from, or dysfunctional at the apical membrane of epithelial cells where it normally contributes to transepithelial fluid transport. As a possible complement to CFTR gene replacement, we assessed the feasibility of in vivo transfer of purified CFTR protein via phospholipid liposomes into the nasal epithelial cells of CFTR knockout mice. In this report, we show that membrane incorporation of CFTR and correction of CF-related defects in ion transport are achieved in about one-third of the protein-treated animals.