Submitted on January 5, 2009
Revised on March 11, 2009
Accepted on March 27, 2009
The initiation and maturation of cilia generated flow in the newborn and postnatal mouse airway
Richard John Bruce Francis1, Bishwanath Chatterjee2, Niki T Loges3, Hanswalter Zentgraf4, Heymut Omran5, and Cecilia W. Lo6*
1 National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD
2 NHLBI. NIH
3 University Hospital Freiburg Mathildenstraße 1, D-79106 Freiburg, Germany
4 German Cancer Research Center
5 University Hospital Freiburg Mathildenstraße 1
6 NIH/NHLBI
* To whom correspondence should be addressed. E-mail: loc{at}nhlbi.nih.gov.
Mucociliary clearance in the adult trachea is well characterized, but there is limited data in newborns. Cilia generated flow was quantified across longitudinal sections of mouse tracheal from birth through postnatal day (PND) 28 by tracking fluorescent microsphere speed and directionality. The percentage of ciliated tracheal epithelial cells, as determined by immunohistochemistry, was shown to increase linearly between PND 0-21 (R2=0.94). While directionality measurements detected patches of flow starting at PND 3, uniform flow across the epithelia was not observed until PND 7 at a ~35% ciliated cell density. Flow became established at a maximal rate at PND 9 and beyond. A linear correlation was observed between the percentage of ciliated cells versus flow speed (R2=0.495) and directionality (R2=0.975) between PND 0-9. Cilia beat frequency (CBF) was higher at PND 0 than all subsequent time points, but cilia beat waveform was not noticeably different. Tracheal epithelia from a mouse model of PCD harboring a Mdnah5 mutation showed ciliated cell density was unaffected, but no cilia generated flow was detected. Cilia in mutant airways were either immotile, or with slow dyssynchronous beat and abnormal ciliary waveform. Overall, our studies showed the initiation of cilia generated flow is directly correlated with an increase in epithelial ciliation, with the measurement of directionality being more sensitive than speed for detecting flow. The higher CBF observed in newborn epithelia suggests unique physiology in the newborn trachea, indicating possible clinical relevance to the pathophysiology of respiratory distress seen in newborn PCD patients.
