title: Late-gestation tracheal occlusion in the fetal lamb causes rapid lung growth with type II cell preservation.
abstract: BACKGROUND
  Fetal tracheal occlusion (TO) results in varying degrees of lung growth. This study examines whether gestational age influences lung growth response following TO.
  
  
  METHODS
  Fetal lambs (term = 145 days) underwent TO early (108 days, n = 6) or late (122 days, n = 6) in gestation. Aspirated lung fluid volume (LFV) and intratracheal pressure (ITP) were recorded daily. Two weeks after TO, the fetuses were sacrificed. Lung growth was assessed by lung weight and stereologic volumetry. Type II cellular density was assessed by computer-assisted morphometry using antisurfactant protein B antibody.
  
  
  RESULTS
  After early TO, ITP remained below 2 mm Hg for all but one of the first 5 days. In late TO, ITP rose to 4.8 +/- 1.7 mm Hg by Day 1 and remained elevated. LFV remained lower after early than after late TO (P < 0.05) for 8 days. Thereafter, pressure and volume reached similar levels in both TO groups; both were significantly higher than their respective controls (P < 0.05). Parenchymal fraction (1 - air-space fraction) was significantly smaller after late TO (22.8 +/- 1.2%) than after early TO (31.3 +/- 0.5%). Type II density was 38.0 +/- 12.4 x 10(6)/mL after early TO and 84.0 +/- 24.3 x 10(6)/mL in control (P < 0.05); the difference between late TO and control was not significant.
  
  
  CONCLUSIONS
  Late tracheal occlusion in fetal lambs caused more rapid lung growth than earlier TO, although ultimate lung size was similar in both groups. Late TO also resulted in greater air-space fraction and better preservation of the type II cell population than early TO. Late-gestation tracheal occlusion may therefore be preferable to prolonged occlusion initiated earlier.
authors.affiliation: Division of Pediatric Surgery, Brown University School of Medicine, Providence, Rhode Island 02905, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Liao
authors.forename: F I
authors.initials: FI
authors.lastname: Luks
authors.forename: G J
authors.initials: GJ
authors.lastname: Piasecki
authors.forename: Y K
authors.initials: YK
authors.lastname: Wild
authors.forename: K
authors.initials: K
authors.lastname: Papadakis
authors.forename: M E
authors.initials: ME
authors.lastname: De Paepe
mesh_terms: D000402:Airway Obstruction / Q000503:physiopathology*; D000818:Animals; D001826:Body Fluids / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D005260:Female; D005865:Gestational Age; D008168:Lung / Q000166:cytology* / Q000196:embryology* / Q000378:metabolism; D009929:Organ Size; D011312:Pressure; D011663:Pulmonary Surfactants / Q000378:metabolism; D012756:Sheep; D014133:Tracheal Diseases / Q000503:physiopathology*
chemical_list: D011663:Pulmonary Surfactants