Cell proliferation and apoptosis in experimental lung hypoplasia.
OBJECTIVE
Current treatment for lethal pulmonary hypoplasia in congenital diaphragmatic hernia (CDH) may be hampered by uncertainty over its origin. Herniation of abdominal organs into the chest was thought to produce lung hypoplasia by compression. Experimental CDH models suggest that disturbed lung growth precedes these events. Mammalian development comprises cell differentiation, proliferation and programmed cell death or apoptosis. Could lung hypoplasia in CDH result from alterations in these processes well before visceral herniation takes place? The aim of this study was to compare cell proliferation and apoptosis in normal and hypoplastic embryonic lungs before normal diaphragmatic closure using a CDH model.


METHODS
Sprague-Dawley rats were given 100 mg of nitrofen on day 9.5 of pregnancy to create lung hypoplasia and CDH in newborns (term, 22 days). Control rats received olive oil. Cell proliferation in embryonic lung specimens was measured by bromodeoxyuridine (BrdU) incorporation at 13.5 to 15.5 days' gestation, before normal diaphragmatic closure in this species (day 16.5). Apoptosis was measured by the in situ end-nick labelling (TUNEL) method in lung sections obtained from rat embryos of 13.5 to 16.5 days' gestation.


RESULTS
High levels of cell proliferation were seen in both normal control and nitrofen-exposed lungs. However, 24 hours before normal diaphragmatic closure, nitrofen-exposed lungs had significant reductions in cell proliferation on day 15.5 of gestation (P = .009 v controls). Apoptosis occurred at low levels throughout the developmental stages examined (< 0.3%) without significant differences encountered between the study groups.


CONCLUSIONS
These findings have shown high rates of cell division during normal lung development before diaphragmatic closure. Decreased levels over this critical period in gestation may contribute to early lung anomalies in the nitrofen CDH model. Strategies to promote cell proliferation in the fetal lung may therefore hold future promise in human CDH. Apoptosis appears not to play a major role in hypoplastic lung development. Therapies to inhibit apoptosis would seem unlikely to improve this early lung growth.
Jesudason
E C
EC
Department of Paediatric Surgery, Institute of Child Health, Alder Hey Children's Hospital and The School of Biological Sciences, University of Liverpool, England.
Connell
M G
MG
Fernig
D G
DG
Lloyd
D A
DA
Losty
P D
PD
D000818:Animals; D017209:Apoptosis; D001973:Bromodeoxyuridine / Q000378:metabolism; D002455:Cell Division; D004247:DNA / Q000378:metabolism; D005865:Gestational Age; D006548:Hernia, Diaphragmatic / Q000150:complications / Q000196:embryology* / Q000473:pathology; D065630:Hernias, Diaphragmatic, Congenital; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008168:Lung / Q000002:abnormalities / Q000196:embryology* / Q000473:pathology; D010647:Phenyl Ethers; D051381:Rats; D017207:Rats, Sprague-Dawley
D010647:Phenyl Ethers; D004247:DNA; D001973:Bromodeoxyuridine; C007350:nitrofen