title: Retinoic acid rescues deficient airway innervation and peristalsis of hypoplastic rat lung explants.
abstract: BACKGROUND
  Bronchial peristalsis modulates lung growth and is deficient in hypoplastic nitrofen-exposed rat lung explants. Retinoic acid (RA) rescues lung hypoplasia. This study examines whether decreased bronchial innervation contributes to this developmental deficiency and if RA is able to recover bronchial innervation and motility.
  
  
  METHODS
  After IRB approval, pregnant rats received either 100 mg nitrofen or vehicle on gestational day 9.5 (E9.5). Embryonic lung primordia harvested on E13 were cultured for 72 h and RA was added daily to the medium when appropriate. Lung growth was assessed by counting the number of terminal buds and measuring explant surface, total DNA and protein in control, control + RA, nitrofen and nitrofen + RA groups. Peristaltic contractions were recorded for 10 min under an inverted microscope. Lung explants stained for anti-protein gene product 9.5 (PGP 9.5) and smooth muscle α-actin were examined under a confocal microscope for depicting the specific relationship between neural and smooth muscle cells. PGP 9.5 and smooth muscle α-actin levels were quantified by Western blot analysis for assessing the neural and muscle cell expressions. Comparisons between groups were made with non-parametric tests.
  
  
  RESULTS
  The number of terminal buds, the explants' surface and the DNA and protein contents were significantly decreased in nitrofen-exposed lungs in comparison with controls. In contrast, these measurements were normal in explants exposed to both nitrofen and RA. Bronchial peristalsis (contractions/min) was significantly decreased in nitrofen-exposed lungs in comparison with controls; in contrast, in nitrofen + RA lungs it was similar to controls. In all study groups, the airways were surrounded by smooth muscle and ensheathed in a plexus of nerve fibers containing ganglia. PGP 9.5 protein levels were decreased in nitrofen-exposed lungs, but they normalized when RA was added. No differences were found in α-actin protein levels. Explants exposed only to RA were similar to control.
  
  
  CONCLUSIONS
  Lung growth, bronchial innervation and peristalsis are decreased in nitrofen-exposed lung explants and are rescued by RA. If deficient airway innervation contributing to dysmotility and pulmonary hypoplasia can be pharmacologically rescued, new relatively simple prenatal interventions could be envisioned.
authors.affiliation: Department of Pediatric Surgery and Research Laboratory, Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Federica
authors.initials: F
authors.lastname: Pederiva
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Martinez
authors.forename: Juan A
authors.initials: JA
authors.lastname: Tovar
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006548:Hernia, Diaphragmatic / Q000139:chemically induced / Q000188:drug therapy; D007641:Keratolytic Agents / Q000627:therapeutic use*; D008168:Lung / Q000002:abnormalities / Q000187:drug effects / Q000254:growth & development / Q000294:innervation; D008297:Male; D009924:Organ Culture Techniques; D010528:Peristalsis / Q000187:drug effects / Q000502:physiology; D010575:Pesticides / Q000633:toxicity; D010647:Phenyl Ethers / Q000633:toxicity; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014212:Tretinoin / Q000627:therapeutic use*; D043222:Ubiquitin Thiolesterase / Q000032:analysis
chemical_list: D000199:Actins; D007641:Keratolytic Agents; D010575:Pesticides; D010647:Phenyl Ethers; D014212:Tretinoin; C489034:UCHL1 protein, rat; D043222:Ubiquitin Thiolesterase; C007350:nitrofen