In a new study led by Miguel Constância published in the journal Developmental Cell, Ionel Sandovici and colleagues report the identification of a key signal that a fetus uses to control its supply of nutrients from the placenta.
In mammals, the fetus receives nutrients and oxygen via blood vessels in the placenta, a temporary, specialized organ that evolved around 150-200 million years ago. The placenta contains cells from both the growing baby and the mother and acts as the interface between them, allowing exchange of molecular signals, nutrients and more. As it grows, the fetus must access more nutrients and one of the ways this can happen is by promoting the growth of a bigger and better blood vessel network in the placenta. In humans, placental blood vessels reach a total length of approximately 320 kilometres at term. Not much has been known about how the fetus communicates this increasing need for food to the mother. Between 10% and 15% of babies grow poorly in the womb and reduced growth of blood vessels in the placenta is often seen in these cases.
In this study, the team uncovers IGF2 (insulin like growth factor 2) as a molecular signal that the fetus produces to encourage the growth of blood vessels within the placenta and establishes its mechanisms of action on the cells that line the inner surface of the vessels, called endothelial cells. In humans, levels of IGF2 in the umbilical cord progressively increase between 29 weeks of gestation and term: too much IGF2 is associated with too much growth, while not enough IGF2 is associated with too little growth. Babies that are too large or too small are more likely suffer or even die at birth, and have a higher risk of developing diabetes and heart problems as adults.
Sandovici, I et al. The Imprinted Igf2-Igf2r Axis is Critical for Matching Placental Microvasculature Expansion to Fetal Growth. Developmental Cell; 10 Jan 2022: DOI: 10.1016/j.devcel.2021.12.005