Biological features of placental programming

Abstract

The placenta is a key organ in programming the fetus for later disease. This review outlines nine of many structural and physiological features of the placenta which are associated with adult onset chronic disease. 1) Placental efficiency relates the placental mass to the fetal mass. Ratios at the extremes are related to cardiovascular disease risk later in life. 2) Placental shape predicts a large number of disease outcomes in adults but the regulators of placental shape are not known. 3) Non-human primate studies suggest that at about mid-gestation, the placenta becomes less plastic and less able to compensate for pathological stresses. 4) Recent studies suggest that lipids have an important role in regulating placental metabolism and thus the future health of offspring. 5) Placental inflammation affects nutrient transport to the fetus and programs for later disease. 6) Placental insufficiency leads to inadequate fetal growth and elevated risks for later life disease. 7) Maternal height, fat and muscle mass are important in combination with placental size and shape in predicting adult disease. 8) The placenta makes a host of hormones that influence fetal growth and are related to offspring disease. Unfortunately, our knowledge of placental growth and function lags far behind that of other organs. An investment in understanding placental growth and function will yield enormous benefits to human health because it is a key player in the origins of the most expensive and deadly chronic diseases that humans face.

Keywords: Birthweight; Chronic disease; Inflammation; Placenta; Programming; Trophoblast.

Figure 1

The risk of coronary heart disease based on the weight ratio of placenta and fetus. [5]

Figure 2

The primary elements that lead to a pro-inflammatory state in both fetal and postnatal life. Beginning left, pro-inflammatory molecules affect placental inflammatory gene expression depending on the physiological status of the mother. A pro-inflammatory placenta leads to compromised immune function in the fetus along with elevated levels of oxidative stress. The outcome is a fetus that suffers “smoldering, cold inflammation” that may persist and make it more likely that the offspring will be more vulnerable for adult-onset chronic disease.