title: Effects of glucocorticoid exposure on growth and structural maturation of the heart of the preterm piglet.
abstract: Inadequate maintenance of systemic blood flow in neonates following preterm birth is associated with increased morbidity and mortality, and may be due in part to structural immaturity of the myocardium. Maternal glucocorticoid administration is associated with improved cardiovascular function, and possibly promotes structural maturation of the myocardium. This study assessed the structural maturity of the myocardium in male and female preterm and term piglets, and preterm piglets exposed to a regimen of maternal glucocorticoids as used clinically. In preterm, term and glucocorticoid exposed preterm piglets cardiomyocyte maturity was examined by measuring the proportion of binucleated myocytes and the volumes of single living ventricular cardiomyocytes with fluorescence microscopy. Ventricular apoptosis and proliferation were measured by immunohistochemistry. Preterm piglet hearts had fewer binucleated myocytes, smaller myocytes, and more proliferative and fewer apoptotic nuclei than term hearts. Maternal glucocorticoid treatment resulted in increased binucleation with no increase in myocyte volume, and levels of proliferation and apoptosis that were more similar to the term heart. Atrial weights were increased and in female piglets there was an increase in the ratio of left to right ventricular weight. The observed changes in atrial mass and myocyte structural maturation correlated with changes in cardiac function of isolated hearts of littermates. In conclusion, the association between increased myocardial maturation following glucocorticoid exposure, improved cardiac function in littermates, and clinical improvement in human neonatal cardiac function exposed to antenatal glucocorticoids, suggests that glucocorticoid exposure contributes to improved cardiovascular function in preterm infants by promoting myocardial structural maturity.
authors.affiliation: The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.
authors.forename: Min Young
authors.initials: MY
authors.lastname: Kim
authors.affiliation: The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.
authors.forename: Yvonne A
authors.initials: YA
authors.lastname: Eiby
authors.affiliation: The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia; Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, Australia; School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, Australia.
authors.forename: Eugenie R
authors.initials: ER
authors.lastname: Lumbers
authors.affiliation: The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.
authors.forename: Layne L
authors.initials: LL
authors.lastname: Wright
authors.affiliation: Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Gibson
authors.affiliation: The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Barnett
authors.affiliation: The University of Queensland, UQ Centre for Clinical Research, Brisbane, Australia.
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Lingwood
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D001623:Betamethasone / Q000494:pharmacology*; D002467:Cell Nucleus / Q000187:drug effects / Q000648:ultrastructure; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005865:Gestational Age; D005938:Glucocorticoids / Q000494:pharmacology*; D006334:Heart Function Tests / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development; D008297:Male; D009206:Myocardium / Q000166:cytology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects*; D009924:Organ Culture Techniques; D013552:Swine
chemical_list: D005938:Glucocorticoids; D001623:Betamethasone