Electroporation-mediated gene delivery of surfactant protein B (SP-B) restores expression and improves survival in mouse model of SP-B deficiency

Surfactant Protein B Deficiency is a rare but lethal monogenetic, congenital lung disease of the neonate that is unresponsive to any treatment except lung transplantation. Based on the potential that gene therapy offers to treat such intractable diseases, our objective was to test whether an electroporation-based gene delivery approach could restore surfactant protein B expression and improve survival in a compound knockout mouse model of surfactant protein B deficiency. Surfactant protein B expression can be shut off in these mice upon withdrawl of doxycycline, resulting in decreased levels of surfactant protein B within four days and death due to lung dysfunction within four to seven days. Control or one of several different human surfactant protein B-expressing plasmids was delivered to the lung by aspiration and electroporation at the time of doxycycline removal or four days later. Plasmids expressing human surfactant protein B from either the UbC or CMV promoter expressed surfactant protein B in these transgenic mice at times when endogenous surfactant protein B expression was silenced. Mean survival was increased 2-to 5-fold following treatment with the UbC or CMV promoter-driven plasmids, respectively. Histology of all surfactant protein B treated groups exhibited fewer neutrophils and less alveolar wall thickening compared to the control groups, and electron microscopy revealed that gene transfer of surfactant protein B resulted in lamellar bodies that were similar in the presence of electron-dense, concentric material to those in surfactant protein B-expressing mice. Taken together, our results show that electroporation-mediated gene delivery of surfactant protein B-expressing plasmids improves survival, lung function, and lung histology in a mouse model of surfactant protein B deficiency and suggest that this may be a useful approach for the treatment of this otherwise deadly disease.