Chronic hypoxia in pregnant mice impairs the placental and fetal vascular response to acute hypercapnia in BOLD-MRI hemodynamic response imaging

Yehuda Ginosar*, Zohar Bromberg, Nathalie Nachmanson, Ilana Ariel, Galina Skarzinski, Lital Hagai, Uriel Elchalal, Joel Shapiro, Rinat Abramovitch

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Introduction: Brief hypercapnic challenge causes acute placental hypoperfusion with fetal brain sparing on BOLD-MRI. We hypothesize that this non-invasive imaging strategy can distinguish between normal pregnancy and chronic placental hypoperfusion (using the maternal hypoxia model). Methods: Eighteen pregnant female ICR mice were randomized to three groups: normoxia, late-onset hypoxia (12%O2;E13.5–17.5) and early-onset hypoxia (12%O2;E10.5–17.5). On E17.5, animals were imaged in a 4.7-T Bruker-Biospec MRI scanner. Fast coronal True-FISP was performed to identify organs of interest (placenta and fetal heart, liver and brain). BOLD-MRI was performed at baseline and during a 4-min hypercapnic challenge (5%CO2). %-change in placental and fetal signal was analyzed from T2*-weighted gradient echo MR images. Following MRI, fetuses and placentas were harvested, weighed and immuno-stained. Results: In normoxic mice, hypercapnia caused reduction in BOLD-MRI signal in placenta (−44% ± 7%; p < 0.0001), fetal liver (−32% ± 7%; p < 0.0001) and fetal heart (−54% ± 12%; p < 0.002), with relative fetal brain sparing (−12% ± 5%; p < 0.0001). These changes were markedly attenuated in both hypoxia groups. Baseline fetal brain/placenta SI ratio was highest in normoxic mice (1.14 ± 0.017) and reduced with increasing duration of hypoxia (late-onset hypoxia: 1.00 ± 0.026; early-onset hypoxia: 0.91 ± 0.016; p = 0.02). Both hypoxic groups exhibited fetal growth restriction with prominent placental glycogen-containing cells, particularly in early-onset hypoxia. There was increased fetal neuro- and intestinal-apoptosis in early-onset hypoxia only. Conclusions: BOLD-MRI with brief hypercapnic challenge distinguished between normoxia and both hypoxia groups, while fetal neuroapoptosis was only observed after early-onset hypoxia. This suggests that BOLD-MRI with hypercapnic challenge can identify chronic fetal asphyxia before the onset of irreversible brain injury.

Original languageEnglish
Pages (from-to)29-38
Number of pages10
JournalPlacenta
Volume110
StatePublished - Jul 2021

Bibliographical note

Publisher Copyright:
© 2021

Keywords

  • Animals
  • Fetal asphyxia
  • Fetal growth restriction
  • Hypercapnia
  • Hypoxia
  • Magnetic resonance imaging
  • MESH terms): mice
  • Placenta
  • Pregnancy

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