Intratracheal Keratinocyte Growth Factor Enhances Surfactant Protein B Expression in Mechanically Ventilated Preterm Pigs

Abstract

Background: Bronchopulmonary dysplasia is a devastating disease of the premature newborn with high morbidity and mortality. Surfactant deficient preterm lungs are susceptible to ventilator induced lung injury, thereby developing bronchopulmonary dysplasia. Despite surfactant therapy and newer ventilation strategies, associated morbidity and mortality remains unchanged. Enhancing surfactant production and reducing ventilator induced lung injury in premature infants are critical. Recombinant keratinocyte growth factor previously been studied to treat adult respiratory distress syndrome. We hypothesized that administering recombinant human keratinocyte growth factor when initiating mechanical ventilation would help stimulate type II cell proliferation and surfactant production. Recombinant human keratinocyte growth factor may also help mitigate ventilator induced lung injury hereby reducing epithelial to mesenchymal transition, a possible precursor to later development of bronchopulmonary dysplasia. Methods: To test our hypothesis, we delivered preterm pigs via cesarean section on day 102. We performed intubation and ventilation for 24 hr. using intermittent positive pressure ventilation. After ventilation began, pigs randomly received intratracheal recombinant human keratinocyte growth factor (20 μg/kg; n=6) or sham treatment (0.5 ml 0.9% saline; n= 6). We recorded physiology data and arterial blood gases during ventilation. After 24 hr. pigs were extubated and received oxygen via nasal cannulation 12 hr. before euthanasia to collect lungs for histopathology and immunohistochemistry. Immunohistochemistry staining was graded and analyzed for surfactant protein B and epithelial to mesenchymal transition markers. Data were analyzed using t-test and Fisher’s exact test. Continuous variables analyzed using ANOVA.Results: Compared with control pigs, recombinant human keratinocyte growth factor pretreated pigs had improved ventilation with higher tidal volumes and required less oxygen (FiO2) during mechanical ventilation for similar peak pressures demonstrating improved lung compliance. Recombinant human keratinocyte growth factor pretreated pig lungs showed increased surfactant protein B expression (p< 0.05) and significantly reduced TGF-β (p< 0.05), a prominent marker for epithelial to mesenchymal transition. Conclusions: Intratracheal recombinant human keratinocyte growth factor administered at initiation of mechanical ventilation enhances surfactant production, reduce lung injury by mitigation of the changes by epithelial mesenchymal transition, thereby improving outcomes. Thus, recombinant human keratinocyte growth factor may represent a potential therapeutic strategy to prevent bronchopulmonary dysplasia.