Nasal ventilation alters mesenchymal cell turnover and improves alveolarization in preterm lambs.
BACKGROUND
Bronchopulmonary dysplasia (BPD) is a frequent cause of morbidity in preterm infants that is characterized by prolonged need for ventilatory support in an intensive care environment. BPD is characterized histopathologically by persistently thick, cellular distal airspace walls. In normally developing lungs, by comparison, remodeling of the immature parenchymal architecture is characterized by thinning of the future alveolar walls, a process predicated on cell loss through apoptosis.


OBJECTIVE
We hypothesized that minimizing lung injury, using high-frequency nasal ventilation to provide positive distending pressure with minimal assisted tidal volume displacement, would increase apoptosis and decrease proliferation among mesenchymal cells in the distal airspace walls compared with a conventional mode of support (intermittent mandatory ventilation).


METHODS
Accordingly, we compared two groups of preterm lambs: one group managed by high-frequency nasal ventilation and a second group managed by intermittent mandatory ventilation. Each group was maintained for 3 days.


RESULTS
Oxygenation and ventilation targets were sustained with lower airway pressures and less supplemental oxygen in the high-frequency nasal ventilation group, in which alveolarization progressed. Thinning of the distal airspace walls was accompanied by more apoptosis, and less proliferation, among mesenchymal cells of the high-frequency nasal ventilation group, based on morphometric, protein abundance, and mRNA expression indices of apoptosis and proliferation.


CONCLUSIONS
Our study shows that high-frequency nasal ventilation preserves the balance between mesenchymal cell apoptosis and proliferation in the distal airspace walls, such that alveolarization progresses.
Department of Pediatrics, Division of Neonatology, University of Utah Health Sciences Center, Williams Building, PO.Box 581289, Salt Lake City, UT 84158, USA. kurt.albertine@hsc.utah.edu
Brent
B
Reyburn
Marlana
M
Li
Drew B
DB
Metcalfe
Nicholas J
NJ
Kroll
Jeremy
J
Alvord
Albert
A
Wint
Mar Janna
MJ
Dahl
Jiancheng
J
Sun
Li
L
Dong
Zheng-Ming
ZM
Wang
Christopher
C
Callaway
Robert A
RA
McKnight
Laurie
L
Moyer-Mileur
Bradley A
BA
Yoder
Donald M
DM
Null
Robert H
RH
Lane
Kurt H
KH
Albertine
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology*; D001997:Bronchopulmonary Dysplasia / Q000473:pathology*; D053148:Caspase 3 / Q000378:metabolism; D002455:Cell Division / Q000502:physiology*; D045422:Continuous Positive Airway Pressure; D005865:Gestational Age; D006612:High-Frequency Ventilation; D006801:Humans; D007231:Infant, Newborn; D007385:Intermittent Positive-Pressure Ventilation; D008648:Mesoderm / Q000473:pathology*; D010100:Oxygen / Q000097:blood; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000473:pathology*; D012756:Sheep; D013990:Tidal Volume / Q000502:physiology
D018809:Proliferating Cell Nuclear Antigen; D053148:Caspase 3; D010100:Oxygen