Improved efficiency of gene transfer to the transplanted lung by retrograde vascular gene delivery

Experiments were designed to evaluate the efficiency of antegrade compared to retrograde vascular gene transfection of donor lungs used for transplantation. Rat donor lungs (n = 5/group) were transduced with an adenoviral vector encoding for β-galactosidase (AdβGal), either antegrade in the pulmonary artery (Group A, 3 x 10⁸ pfu, Group B, 3 x 10⁹ pfu) or retrograde into the pulmonary vein (Group C, 3 x 10⁸ pfu), immediately after pneumoplegia. After storage at 4°C for 1 h, the transduced lungs were transplanted orthotopically in syngeneic animals. The lungs were assessed for transgene expression by ELISA and X-Gal-staining at day 7 after operation. Inflammation was graded based on the extent of inflammatory cell infiltration. Transgene expression was similar between Groups A (1.7 ± 0.7 ng/mg protein) and B (2.1 ± 1.0 ng/mg protein). With retrograde delivery, there was a four-fold (8.3 ± 2.6 ng/mg protein) increase (P < 0.05) in transgene expression compared to either group A or B. In all groups, pneumocytes were transduced most frequently. The degree of inflammation correlated positively with the extent of transgene expression (r = 0.75, P < 0.01). The efficiency of vascular gene delivery to transplanted lungs can be improved by retrograde delivery of the vector via the pulmonary vein. Transgene expression predominates in pneumocytes following both antegrade and retrograde delivery. The severity of inflammation in the transplanted lung appears to correlate with the extent of transgene expression.