Variation in fetal growth may be associated with genetic or environmental factors. In litter-bearing animals local and/or systemic reciprocal or destructive effects may exist when sibling embryos/fetuses from different genetic background are carried in the same litter or when embryonic loss in mid-pregnancy exerts factors that might influence the growth of the survivors. This study was conducted to examine the influence of natural occurring absorptions on the adjacent fetuses in pregnant mice at late-gestation using non-invasive Arterial Spin Labeling (ASL) MRI as a measure of directional blood flow and ex-vivo fluorescence studies of placentas as a measure of blood volume (Figure 1A).

Spontaneous resorptions occurred anywhere along the uterine horn (p=0.6931). Fetuses that had an absorbed neighbor had significantly lower ASL values (1.1±0.4 vs. 3.0±0.2, p= 0.0009) and lower fluorescence signals (536±81 vs. 946±40, p=0.0083), compared to fetuses which had “normal neighbors” (Fig.1 B and C). This suggests that in a system of multiple fetuses there are communication levels that exist between embryos/fetuses that may cause non-genetic variability. Knowledge of these effects can reduce experimental variability and increase the chance of measuring reproducible results.

 

Figure1: (A) experimental approach: Female ICR mice were analyzed using 3 imaging modalities: non-invasive ASL MRI, in vivo uterine horns intravital microscopy and ex vivo analysis of the placental maternal blood volume. (B) ASL values in placentas of fetuses located near vital fetuses, compared to those near absorbed fetuses. (C) Fluorescence signal in placentas of fetuses located near vital fetuses, compared to those near absorbed fetuses.

Authors

Avni R¹, Raz T¹, Garbow J², Neeman M¹ 

1Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel

2 Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri, USA