ObjectiveTo study the effects of conventional mechanical ventilation (CMV) with low tidal volume on developmental porcine lungs by examining the expression of growth factors and inflammatory mediators.MethodsTwelve preterm piglets born at 99 days of gestational age, 12 term neonatal piglets and 11 young piglets ( 4-5-weeks old) were randomly placed on CMV or were not ventilated (control group). The ventilator settings were adjusted to provide a tidal volume of 6-8 mL/kg in order to maintain a normal blood-gas value. After 6 hrs (preterm piglets) or 24 hrs (neonatal and young piglets) of mechanical ventilation, the mRNA expression of growth factors PDGF-B, IGF-I, KGF, HGF, VEGF and TGF-β1 and proinflammatory cytokines IL-1β, IL-6, IL-8 and TNF-α in the lung tissue was measured using RT-PCR. Growth factor protein expression was measured with immunohistochemistry.ResultsIn preterm piglets, the CMV group had increased mRNA expression of PDGF-B (5.11±0.10 vs 4.88±0.01), IL-1β (4.95±0.27 vs 4.08±0.37), IL-6 (4.76±0.27 vs 4.00±0.28) and IL-8 (5.31±0.57 vs 4.15±0.46), but decreased IGF-I mRNA expression (3.54±0.13 vs 3.80±0.11) compared with those in the control group (P<0.05 or 0.01). In term neonatal piglets and young piglets, there were no significant differences in the mRNA expression of growth factors and proinflammatory cytokines between the CMV and control groups.ConclusionsCMV caused inflammatory injury in immature lungs by increasing the expression of proinflammatory cytokines and PDGF-B and decreasing IGF-I expression. However, CMV had no effects on pulmonary expression of growth factors and inflammatory mediators in term neonatal piglets and young piglets.