IN-UTERO GENE-TRANSFER INTO THE PULMONARY EPITHELIUM

In early gestation the internal surface of the lung is structurally si mple and an ideal target for somatic gene transfer(1-3). The transfer of genes into the growing lung would be particularly useful in the pre natal correction of cystic fibrosis, which has devastating pulmonary c omplications. In addition, in utero gene therapy has the potential to immunotolerize the individual, and thereby to avoid the immune reactio ns now seen with the current generation of adenoviral vectors(4,5). We injected a replication-defective adenoviral vector containing the lac Z reporter gene (Ad5.CMVlacZ) into the amniotic fluid of rat pups on t he 16th day of gestation(6-9). At 16 days of gestation, rat lungs are equivalent in maturity to those of a 22-week human fetus as their airw ays are lined with undifferentiated multipotential stem cells. The pup s showed high-level reporter gene expression in their airways a week f ollowing birth (13 days following infection). The expression was maint ained during a time when the lung volume increased approximately 20-fo ld, alveolarization occurred, and the epithelial cells differentiated( 2,3). These data establish gene targeting of undifferentiated fetal ce lls as an effective means of gene therapy.