Influence of prenatal hypoxia and postnatal hyperoxia on morphologic lung maturation in mice.

BACKGROUND:Oxygen supply as a lifesaving intervention is frequently used to treat preterm infants suffering additionally from possible prenatal or perinatal pathogen features. The impact of oxygen and/or physical lung injury may influence the morphological lung development, leading to a chronic postnatal lung disease called bronchopulmonary dysplasia (BPD). At present different experimental BPD models are used. However, there are no systematic comparative studies regarding different influences of oxygen on morphological lung maturation. OBJECTIVE:We investigated the influence of prenatal hypoxia and/or postnatal hyperoxia on morphological lung maturation based on stereological parameters, to find out which model best reflects morphological changes in lung development comparable with alterations found in BPD. METHODS:Pregnant mice were exposed to normoxia, the offspring to normoxia (No/No) or to hyperoxia (No/Hyper). Furthermore, pregnant mice were exposed to hypoxia and the offspring to normoxia (Hypo/No) or to hyperoxia (Hypo/Hyper). Stereological investigations were performed on all pups at 14 days after birth. RESULTS:Compared to controls (No/No) 1) the lung volume was significantly reduced in the No/Hyper and Hypo/Hyper groups, 2) the volume weighted mean volume of the parenchymal airspaces was significantly higher in the Hypo/Hyper group, 3) the total air space volume was significantly lower in the No/Hyper and Hypo/Hyper groups, 4) the total septal surface showed significantly lower values in the No/Hyper and Hypo/Hyper groups, 5) the wall thickness of septa showed the highest values in the Hypo/Hyper group without reaching significance, 6) the volume density and the volume weighted mean volume of lamellar bodies in alveolar epithelial cells type II (AEII) were significantly lower in the Hypo/Hyper group. CONCLUSION:Prenatal hypoxia and postnatal hyperoxia differentially influence the maturation of lung parenchyma. In 14 day old mice a significant retardation of morphological lung development leading to BPD-like alterations indicated by different parameters was only seen after hypoxia and hyperoxia

Human umbilical cord blood mononuclear cells in a double-hit model of bronchopulmonary dysplasia in neonatal mice.

BACKGROUND: Bronchopulmonary dysplasia (BPD) presents a major threat of very preterm birth and treatment options are still limited. Stem cells from different sources have been used successfully in experimental BPD, induced by postnatal hyperoxia. OBJECTIVES: We investigated the effect of umbilical cord blood mononuclear cells (MNCs) in a new double-hit mouse model of BPD. METHODS: For the double-hit, date mated mice were subjected to hypoxia and thereafter the offspring was exposed to hyperoxia. Human umbilical cord blood MNCs were given intraperitoneally by day P7. As outcome variables were defined: physical development (auxology), lung structure (histomorphometry), expression of markers for lung maturation and inflammation on mRNA and protein level. Pre- and postnatal normoxic pups and sham treated double-hit pups served as control groups. RESULTS: Compared to normoxic controls, sham treated double-hit animals showed impaired physical and lung development with reduced alveolarization and increased thickness of septa. Electron microscopy revealed reduced volume density of lamellar bodies. Pulmonary expression of mRNA for surfactant proteins B and C, Mtor and Crabp1 was reduced. Expression of Igf1 was increased. Treatment with umbilical cord blood MNCs normalized thickness of septa and mRNA expression of Mtor to levels of normoxic controls. Tgfb3 mRNA expression and pro-inflammatory IL-1β protein concentration were decreased. CONCLUSION: The results of our study demonstrate the therapeutic potential of umbilical cord blood MNCs in a new double-hit model of BPD in newborn mice. We found improved lung structure and effects on molecular level. Further studies are needed to address the role of systemic administration of MNCs in experimental BPD

Stereological variables used for the characterization of lung parenchyma and its morphological maturity.

<div><p>a) Boxblots of the volume density of septa serving as an indirect measure for the development of sacculi and or alveoli.</p> <p>b) Boxplots of the volume density of air spaces serving as an indirect measure for the enfolding of air spaces and the degree of septal thickness.</p> <p>c) Boxplots of the surface density of septa serving as an indirect measure for alveolarization. The higher the septal surface density the higher is the formation of secondary septa as sign for alveolarization. P values obtained by the Mann-Whitney-Rank Sum Test. Significant differences compared to controls are stated.</p> <p>d) Boxplots of the thickness of septa as a measure for the morphological septal maturity. Decrease of the mean barrier septal thickness goes along with increased differentiation of septa. P values obtained by the Mann-Whitney-Rank Sum Test. P< 0.03 compared to controls, p<0.095 compared to the sham treated double-hit.</p></div

Schematic design of the experimental procedure.

<p>In the control group, the animals were constantly kept under normoxic conditions. In the double-hit groups, dams were exposed to hypoxia from day E14 to E18. After birth, the animals were kept in hyperoxia from day P1 to P14. The experimental double-hit group was given 2 x 10⁵ umbilical cord blood MNCs intraperitoneally. The double-hit control was sham treated, being given 0.9% NaCl solution.</p

Pulmonary parenchyma and alveolar epithelial cells type II (AE II) of 14 days old controls (a, b), double-hit sham treated (c,d) and double-hit cell treated animals (e, f).

<p>Pulmonary parenchyma and alveolar epithelial cells type II (AE II) of 14 days old controls (a, b), double-hit sham treated (c,d) and double-hit cell treated animals (e, f).</p