Proceedings of The Physiological Society
University of Cambridge (2008) Proc Physiol Soc 11, PC38
Morphological adaptations of the mouse placenta with maternal undernutrition
O. R. Vaughan1, A. L. Fowden1, P. M. Coan1
1. Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge, United Kingdom.
The placenta is the primary source of nutrients for fetal growth in late gestation. When adverse conditions like undernutrition (UN) compromise the placenta, fetal growth is restricted but often the fetal to placental weight ratio is greater than normal (1). However, the causes of this increased placental efficiency remain unknown. This study examines the effect of gestational undernutrition on the morphological adaptations of the main fetal layers of the mouse placenta; the junctional zone (Jz) and the labyrinthine zone (Lz) responsible for hemotrophic nutrition (2). Singly housed pregnant mice were fed either 23% casein (control, CT, n=56) diet or 80% of CT intake (UN, n=57) during pregnancy. On day (d) 16 and 19 of pregnancy (term=20d) after cervical dislocation, placentas closest to the mean placental weight in each litter were fixed, embedded, sectioned and stained before stereological analysis (CT, n=4-7;UN, n=5-8) (3). Results are means ± SE. Statistical significance of diet was assessed by Student’s t-test. Placental weight and volume were significantly less in UN than CT mice at both ages while UN fetal weight was only lower relative to CT at 19d (Table 1). At 16d placental efficiency measured as f:p weight ratio was significantly greater for UN than CT groups, whereas at 19d, the opposite was found (Table 1). At 16d but not 19d, Jz volume was significantly less in UN than CT placentas. At 19d, undernutrition significantly reduced absolute Lz volume but had no effect on Jz and Lz volumes as percentages of total volume (Table 1). The results show that, at 16d UN restricts Jz growth, which may explain partly the increased placental efficiency as more maternal resources may reach the fetus. However, by 19d, the UN placenta is less efficient than CT. This may be due to the lack of Lz growth in UN placentas and, hence, reduced fetal nutrient provision. Therefore, placental development can, adapt to compensate for poor nutritional conditions at 16d but these adaptations are insufficient to maintain normal fetal growth to 19d.
Where applicable, experiments conform with Society ethical requirements