Photoacoustic imaging for in vivo quantification of placental oxygenation in mice.

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Accurate analysis of placental and fetal oxygenation is critical during pregnancy. Photoacoustic imaging (PAI) combines laser technology with ultrasound in real time. We tested the sensitivity and accuracy of PAI for analysis of placental and fetal oxygen saturation (sO2) in mice. The placental labyrinth (L) had a higher sO2 than the junctional zone plus decidua region (JZ+D) in C57Bl/6 mice. Changing maternal O2 from 100 to 20% in C57Bl/6 mice lowered sO2 in these regions. C57Bl/6 mice were treated with the NO synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME) from gestational day (GD) 11 to GD18 to induce hypertension. L-NAME decreased sO2 in L and JZ+D at GD14 and GD18 in association with fetal growth restriction and higher blood pressure. Hypoxia-inducible factor 1α immunostaining was higher in L-NAME vs control mice at GD14. Fetal sO2 levels were similar between l-NAME and control mice at GD14 and GD18. In contrast to untreated C57Bl/6, L-NAME decreased placental sO2 at GD14 and GD18 vs GD10 or GD12. Placental sO2 was lower in fetal growth restriction in an angiotensin-converting enzyme 2 knockout mouse model characterized by placental hypoxia. On phantom studies, patterns of sO2 measured directly correlated with those measured by PAI. In summary, PAI enables the detection of placental and fetal oxygenation during normal and pathologic pregnancies in mice.-Yamaleyeva, L. M., Sun, Y., Bledsoe, T., Hoke, A., Gurley, S. B., Brosnihan, K. B. Photoacoustic imaging for in vivo quantification of placental oxygenation in mice.