Developmental programming of the ovine placenta.

The pattern of intrauterine growth and size at birth, in particular, programmes the structure and function of tissues later in life in many species, which has important implications for the incidence of adult-onset generative diseases in human populations. In mammals, the main determinant of intrauterine growth is the placental supply of nutrients which, in turn, depends on the size, morphology, transport characteristics and endocrine function of the placenta. However, compared to somatic tissues, little is known about the developmental programming of the placenta. This review examines the epigenetic regulation of placental phenotype with particular emphasis on the nutrient transfer capacity of the ovine placenta and environmental factors shown to cause developmental programming of other tissues. Overall, the placenta is responsive to environmental factors and uses a number of different strategies to adapt its phenotype to help support fetal growth during adverse intrauterine conditions. It is, therefore, not just a passive conduit for nutrient transfer to the fetus but alters its nutrient supply capacity dynamically to optimise fetal nutrient acquisition. Thus, the placental epigenome provides both a memory of environmental conditions experienced during development and an index of the future well being of the offspring.