Evaluation of fetoplacental oxygenation in a rat model of gestational diabetes mellitus using BOLD-MRI at 7.0-T

Objective: To compare the differences in blood oxygen level-dependent (BOLD) parameters following maternal hyperoxia between normal pregnancy and pregnancy in the rat model of gestational diabetes mellitus (GDM). Methods: GDM was induced by high-fat and sucrose diet (HFS) combined with an intraperitoneal injection of streptozotocin (STZ). On embryonic day 19 (E19), the two groups of pregnant rats were imaged using a 7.0-T animal MRI scanner. TurboRARE was initially used to localize the fetoplacental units (FPUs). Next, multiple gradient echo BOLD was performed during the air and oxygen inhalation periods. T2* map was then generated, and the baseline T2* and absolute changes in T2* value (ΔT2*, difference between T2*oxy and T2*air) were calculated. Following the MRI scan, the placentas and fetuses were aseptically stripped, weighed, and immunostained. Results: Nine rats were used in this study. After maternal oxygen inhalation, T2* increased significantly in all subjects in both groups. The ΔT2* for the placenta (5.97 vs. 7.81 msec; P = 0.007) and fetal brain (2.23 vs. 3.97 msec; P = 0.005) differed significantly between the GDM and control groups. Histochemical detection of placental glycogen content and inflammatory cytokines (IL-6 and TNF-α) showed significantly higher levels in the GDM than in the normal placenta. Conclusions: BOLD-MRI revealed abnormalities in the fetoplacental response to maternal hyperoxygenation in rats with GDM. We believe that this approach can potentially be used to evaluate placental dysfunction and assess the state of the fetus during pregnancy with GDM.