Effects of budesonide and surfactant in preterm fetal sheep

Abstract

Mechanical ventilation causes lung injury and systemic inflammatory responses in preterm sheep and is associated with bronchopulmonary dysplasia (BPD) in preterm infants. Budesonide added to surfactant decreased BPD by 20% in infants. We wanted to determine the effects of budesonide and surfactant on injury from high tidal volume (V_T) ventilation in preterm lambs. Ewes at 125 ± 1 days gestational age had fetal surgery to expose fetal head and chest with placental circulation intact. Lambs were randomized to 1) mechanical ventilation with escalating V_T to target 15 ml/kg by 15 min or 2) continuous positive airway pressure (CPAP) of 5 cmH₂O. After the 15-min intervention, lambs were given surfactant 100 mg/kg with saline, budesonide 0.25 mg/kg, or budesonide 1 mg/kg. The fetuses were returned to the uterus for 24 h and then delivered and ventilated for 30 min to assess lung function. Budesonide levels were low in lung and plasma. CPAP groups had improved oxygenation, ventilation, and decreased injury markers compared with fetal V_T lambs. Budesonide improved ventilation in CPAP lambs. Budesonide decreased lung weights and lung liquid and increased lung compliance and surfactant protein mRNA. Budesonide decreased proinflammatory and acute-phase responses in lung. Airway thickness increased in animals not receiving budesonide. Systemically, budesonide decreased monocyte chemoattractant protein-1 mRNA and preserved glycogen in liver. Results with 0.25 and 1 mg/kg budesonide were similar. We concluded that budesonide with surfactant matured the preterm lung and decreased the liver responses but did not improve lung function after high V_T injury in fetal sheep.

Keywords: airway; bronchopulmonary dysplasia; inflammation; mechanical ventilation; preterm.

Fig. 1.

Lung physiology after delivery and pressure-volume curves. CPAP, continuous positive airway pressure; V_T, tidal volume; Bud 1, budesonide 1 mg/kg; Bud 0.25, budesonide 0.25 mg/kg. A: peak inspiratory pressures (PIP) for animals at 30 min of mechanical ventilation. B: $P{a}_{CO}{}_{{}_2}$ values at 30 min. C: ventilation efficiency index (VEI) as calculated {VEI = [3800/(PIP·rate·$P{a}_{CO}{}_{{}_2}$)]} at 30 min. D: open chest pressure-volume inflation and deflation curves of post mortem lungs; n = 5–8 animals/group. *P < 0.05 vs. CPAP + Saline.

Fig. 2.

Proinflammatory cytokine and acute-phase mRNA in peripheral lung tissue. CPAP, continuous positive airway pressure; V_T, tidal volume; V_T15, V_T for 15 min; Bud 1, budesonide 1 mg/kg; Bud 0.25, budesonide 0.25 mg/kg. Interleukin (IL)-1β (A), IL-6 (B), IL-8 (C), and monocyte chemotactic protein-1 (MCP-1; D) mRNA in peripheral lung tissue. Acute-phase response genes early growth response protein-1 (Egr-1; E), serum amyloid A3 (SAA; F), chitinase-3-like protein-1 (CHI3L1; G), and epiregulin (EREG; H) mRNA responses in the lung. Values are means ± SE with unventilated control (UVC) set at 1; n = 5–8 animals/group. +P < 0.05 vs. UVC; *P < 0.05 vs. CPAP + Saline; tP < 0.05 vs. V_T15 +Saline.

Fig. 3.

Large-airway images. Representative images of airways and peripheral lung stained with Sirius Red-Fast Green FCF with picric acid (×20). CPAP, continuous positive airway pressure; V_T, tidal volume; Bud 1, budesonide 1 mg/kg; Bud 0.25, budesonide 0.25 mg/kg. A: unventilated controls have epithelial layer of ciliated cells and thin collagen layer (staining red) below epithelium and thin septum of the peripheral lung tissue. B: animals receiving CPAP + Saline have mild thickening of airways and mild congestion in peripheral lungs, finding not seen in animals receiving CPAP and budesonide (C). D: mechanical ventilation with V_T 15 ml/kg caused congestion of the lungs and thickening of the airways. These changes were not seen with Bud 0.25 (E) or Bud 1 (F). Quantification of blinded segments provided in Table 2; n = 5 animals per group. Scale bar, 100 μm.

Fig. 4.

Lung and liver mRNA values. CPAP, continuous positive airway pressure; V_T, tidal volume; V_T15, V_T for 15 min; Bud 1, budesonide 1 mg/kg; Bud 0.25, budesonide 0.25 mg/kg. Lung (A–E): mRNA for surfactant proteins A (SFTPA; A), SFTPB (B), SFTPC (C), and SFTPD (D). Aquaporin 5 (AQ5; E) and epithelial sodium channel (ENaC; F) mRNA in the lung tissue. G: ATP-binding cassette sub-family A member 3 (ABCA3) transporter mRNA in lung. Liver (H–K): proinflammatory cytokine monocyte chemoattractant protein-1 (MCP-1; H) and IL-1β mRNA (I) in liver tissue. Acute-phase response genes serum amyloid A3 (SAA3; J) and chitinase-3-like protein-1 (CHI3L1; K) mRNA responses in the liver. Values are means ± SE with unventilatedcontrol (UVC) set at 1; n = 5–8 animals/group. +P < 0.05 vs. UVC; *P < 0.05 vs. CPAP + Saline; tP < 0.05 vs. V_T15 +Saline.