title: Lung parenchyma at maturity is influenced by postnatal growth but not by moderate preterm birth in sheep.
abstract: BACKGROUND
  We have recently shown that moderate preterm birth, in the absence of respiratory support, altered the structure of lung parenchyma in young lambs, but the long-term effects are unknown.
  
  
  OBJECTIVE
  To determine whether structural changes persist to maturity, and whether postnatal growth affects lung structure at maturity in sheep.
  
  
  METHODS
  At approximately 1.2 years after birth, lung parenchyma of sheep born 14 days before term (n = 7) was stereologically compared with that of controls born at term (n = 8, term approx. 146 days).
  
  
  RESULTS
  Preterm birth per se had no significant effect on lung volume, alveolar number and size, and thicknesses of the alveolar walls and blood-gas barrier. After combining the preterm and term groups, we examined the effects of postnatal growth rates on lung parenchyma. Slower-growing sheep (SG; n = 7: 4 preterm, 3 term) were compared with faster-growing sheep (FG; n = 8: 3 preterm, 5 term). At approximately 1.2 years, the right lung volume, relative to body weight, was significantly lower in SG than FG sheep (p < 0.05) and alveolar number was significantly lower by approximately 44%. The total alveolar internal surface area of the right lung of SG sheep was 38% smaller than in FG sheep; it was also significantly lower when related to both lung and body weight.
  
  
  CONCLUSIONS
  Our data suggest that moderate preterm birth does not cause persistent alterations in lung parenchyma. However, slow postnatal growth in low-birth-weight sheep results in smaller lungs with fewer alveoli and a lower alveolar surface area relative to body weight.
authors.affiliation: Department of Medical Biosciences, University of the Western Cape, Bellville, South Africa.
authors.forename: Gert
authors.initials: G
authors.lastname: Maritz
authors.forename: Megan
authors.initials: M
authors.lastname: Probyn
authors.forename: Robert
authors.initials: R
authors.lastname: De Matteo
authors.forename: Ken
authors.initials: K
authors.lastname: Snibson
authors.forename: Richard
authors.initials: R
authors.lastname: Harding
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development; D008168:Lung / Q000254:growth & development* / Q000473:pathology; D008297:Male; D023421:Models, Animal; D009929:Organ Size; D011247:Pregnancy; D047928:Premature Birth; D011650:Pulmonary Alveoli / Q000254:growth & development; D012756:Sheep