In vivo assessment of the placental anatomy and perfusion in a mouse model of intrauterine inflammation

Background: Magnetic resonance imaging (MRI) provides useful markers to examine placental function. MRI features of placental injury due to intrauterine inflammation-a common risk during pregnancy, are not well known.

Purpose: To investigate the capability of structural MRI and intravoxel incoherent motion (IVIM) imaging in examining acute placental injury in a mouse model of intrauterine inflammation, as well as gestation-dependent placental changes.

Study type: Prospective study.

Animal model: Pregnant CD1 mice were scanned on embryonic day 15 (E15, n = 40 placentas from six dams) and E17. On E17, mice were subjected to intrauterine injury by exposure to lipopolysaccharide (LPS, n = 25 placentas from three dams) or sham injury (n = 25 placentas from three dams).

Field strength/sequence: In vivo MRI was performed on an 11.7T Bruker scanner, using a fast spin-echo sequence and a diffusion-weighted echo-planar imaging (EPI) sequence.

Assessment: T₂ -weighted MRI was acquired to evaluate placental volume. IVIM imaging was performed in a restricted field-of-view using 15 b-values from 10-800 s/mm² , based on which, the pseudodiffusion fraction (f), pseudodiffusion coefficient (D*), and tissue water coefficient (D) were estimated with a two-step fitting procedure.

Statistical tests: Two-way analysis of variance (ANOVA) was used to evaluate the group differences.

Results: The placental volume increased by ∼21% from E15 to E17 (P < 0.01), and a 15% volume loss was observed at 6 hours after LPS exposure (P < 0.01). IVIM parameters (f, D*, and f·D*) were similar between the E15 and E17 sham groups (P > 0.05), which was significantly reduced in the LPS-exposed placentas compared to the shams (P < 0.001). D values decreased from E15 to E17 (P < 0.05), which were further reduced after LPS exposure (P < 0.05). Changes in placental area and vascular density were histologically identified in the LPS-exposed group, along with gestation-dependent changes.

Data conclusion: Our results suggested structural MRI and IVIM measurements are potential markers for detecting acute placental injury after intrauterine inflammation.

Level of evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1260-1267.