Mechanical ventilation down-regulates surfactant protein A and keratinocyte growth factor expression in premature rabbits

Surfactant-associated proteins (SP-A, SP-B, and SP-C) are critical for the endogenous function of surfactant. Keratinocyte growth factor (KGF) and vascular endothelial growth factor (VEGF) are key regulators of lung development. The objective of this study was to evaluate the effects of early mechanical ventilation on the expression of these important regulatory proteins in a preterm rabbit model. Premature fetuses were delivered at 29 d of gestation and randomized to necropsy at birth, i.e. no ventilation (NV), spontaneous breathing (SB), or mechanical ventilation (MV) for 16 h. MV animals were further randomized to treatment with dexamethasone (dex). Our findings showed that SB rabbits increased their expression of SP-A mRNA and protein after birth compared with NV controls. MV significantly attenuated this response in the absence of dex. Exposure to dex elevated SP-B mRNA expression in both SB and MV rabbits. KGF protein levels were markedly increased in SB animals compared with MV counterparts. VEGF levels were similar in SB and MV animals, but were significantly increased compared with NV controls. These data suggest that MV alters surfactant-associated protein and growth factor expression, which may contribute to injury in the developing lung.