The Effect of in vivo High Molecular Weight Hyaluronan Treatment on Airway Reactivity in a Neonatal Mouse Model of Continuous Positive Airway Pressure (CPAP)

Abstract

Although continuous positive airway pressure (CPAP) is a commonly used mode of respiratory support in the care of pre‐term infants, its long‐term effects on lung development and airway reactivity are largely unknown. Previously, we developed a neonatal mouse model of CPAP and showed that it caused a long‐term increase in airway reactivity to methacholine challenge. In the current study we tested the hypotheses that hyaluronan (HA), a major component of lung extracellular matrix, plays a role in the airway hyper‐reactivity (AHR) following neonatal CPAP and whether it can be prevented by exogenous administration of high molecular weight HA. Neonatal mice received CPAP (6cm H2O) for 3 hours per day for the first 7 postnatal days. Control animals experienced the same conditions as experimental animals only with no CPAP. On days 3 and 7, a subset of mice in each group received sub‐cutaneous injections of 1% high molecular weight HA (>1000kD, 20μl/g). Two weeks after CPAP ended (postnatal (P) age 21 days), mice were sacrificed and lungs prepared for measurements of airway reactivity to increasing doses of methacholine (0.25μM‐8μM) using the precision cut lung slice method. Airway reactivity to methacholine was increased in P21 mice that received CPAP during the first postnatal week compared to untreated control mice. Gel electrophoresis analysis of whole lung homogenates revealed CPAP also increased total lung HA levels. Immunohistochemical staining of HA with an antibody selective for the hyaluronan binding protein (HABP) showed increased HA expression around the airways within or in the vicinity of airway smooth muscle. However, mice that also received high molecular weight HA during CPAP displayed decreased reactivity to methacholine challenge when compared to airways from animals that received CPAP alone. High molecular weight HA administration also prevented the increased total HA expression caused by CPAP. We conclude that lung HA plays a role in the long‐term increase in AHR following neonatal CPAP, although exogenous administration of high molecular weight HA appears to be protective against such adverse effects of CPAP. These data may have important implications for the way CPAP may contribute to the pathophysiology of wheezing disorders commonly seen in preterm infants.Support or Funding InformationNHLBI PO1HL107147