Effect of adenovector-mediated gene transfer of keratinocyte growth factor on the proliferation of alveolar type II cells in vitro and in vivo.

Alveolar type II cell proliferation occurs after lung injury and is thought to minimize the subsequent fibrotic response. Keratinocyte growth factor (KGF) has been shown to be a potent growth factor for rat alveolar type II cells. In this study, we created a replication-deficient, recombinant human type 5 adenovirus vector expressing human KGF (Ad5-KGF) to produce alveolar type II cell hyperplasia in vivo. In rat type II cells in vitro, Ad5-KGF at a multiplicity of infection (MOI) of 2, 4, and 8 plaque-forming units (PFU)/cell increased thymidine incorporation 13.3-, 16.8-, and 20. 8-fold, respectively. The KGF concentration in the medium increased up to 26.0 +/- 1.0 ng/ ml. We then instilled 10(9) PFU of Ad5-KGF, Ad5-LacZ, or phosphate-buffered saline into Fischer 344 rats and analyzed the lungs 2, 3, 7, 14, 21, and 28 d later. Ad5-KGF produced extensive alveolar type II cell hyperplasia on Days 2, 3, and 7. Surfactant protein (SP)-A and SP-D in lavage and SP-D in serum increased more in the Ad5-KGF group than in the Ad5-LacZ and PBS groups on Days 2 and 3. KGF was readily detectable for up to 7 d in lavage fluid, although only a modest number of cells expressed KGF messenger RNA as detected by in situ hybridization. These data show that Ad5-KGF stimulates extensive alveolar type II cell proliferation in vivo.