Morphological and molecular changes in the murine placenta exposed to normobaric hypoxia throughout pregnancy.
Chronic hypoxia is a common complication of pregnancy, arising through malperfusion of the placenta or pregnancy at high altitude. The present study investigated the effects of hypoxia on the growth of the placenta, which is the organ that interfaces between the mother and her fetus. Mice were housed in an hypoxic environment for the whole of gestation. An atmosphere of 13% oxygen induced fetal growth restriction (1182 ± 9 mg, n = 90 vs. 1044 ± 11 mg, n = 62, P < 0.05) but enhanced placental weight (907 ± 11 mg, n = 90 vs. 998 ± 15 mg, n = 62,P < 0.05). Stereological analyses revealed an increase in the volume of maternal blood spaces in the placenta, consistent with increased flow. At the molecular level, we observed activation of the protein kinase B (Akt)-mechanistic target of rapamycin growth and proliferation pathway. Chronic hypoxia also triggered mild endoplasmic reticulum stress, a conserved homeostatic response that mediates translational arrest through phosphorylation of eukaryotic initiation factor 2 subunit α. Surprisingly, although subunits of the mitochondrial electron transport chain complexes were reduced at the protein level, there was no evidence of intracellular energy depletion. Finally, we demonstrated sex-specific placental responses to chronic hypoxia. Placentas from male fetuses were heavier (1082 ± 2 mg, n = 30 vs. 928 ± 2 mg, n = 34, P < 0.05) and less susceptible to hypoxia-induced oxidative stress than those from females. Their capacity to adapt may explain why male fetuses were significantly less growth restricted at embryonic day 18.5 than their female counterparts. These findings are consistent with the concept that male fetuses are more aggressive with respect to their nutrient demands, which may place them at greater risk of adverse outcomes under limiting conditions.
Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
Hannah
H
Matheson
Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.|Birth Center and the Division of Woman and Baby, University Medical Center Utrecht, Utrecht, The Netherlands.
Jan H W
JH
Veerbeek
Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.|Department of Obstetrics and Gynaecology, University of Cambridge, The Rosie Hospital, Cambridge, UK.|National Institute for Health Research, Cambridge Comprehensive Biomedical Research Centre, Cambridge, UK.
D Stephen
DS
Charnock-Jones
Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
Graham J
GJ
Burton
Centre for Trophoblast Research, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
Hong Wa
HW
Yung
D000818:Animals; D059865:Endoplasmic Reticulum Stress; D005260:Female; D005311:Fetal Hypoxia / Q000378:metabolism* / Q000473:pathology; D020567:Fetal Weight; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010920:Placenta / Q000378:metabolism* / Q000473:pathology; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012737:Sex Factors; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
C546843:mTOR protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C531557:eIF2alpha kinase, mouse