Adaptive responses of early embryos to their microenvironment and consequences for post-implantation development

Abstract

Early embryos are adaptive to the environment they encounter during development and this facilitates embryo resilience to environmental insults. However, it is clear from findings in nonhuman species that adaptive plasticity during early development can have adverse consequences manifesting over the long-term in formation of the post-natal and adult phenotype, and that this occurs via partially characterized programming phenomena. Environmental effectors resulting in adaptive changes to embryos discovered to date include amino acid nutrition, oxygen concentration (both hypoxic and hyperoxic) and growth factor exposure. Other environmental factors known to influence programming of early development have yet to be fully evaluated for their long-term consequences, an area which still requires much work. The mechanisms involved in translation of environmental adaptations to long-term programming are only now being elucidated. Epigenetic mechanisms, especially DNA methylation of imprinted genes, have been associated with adaptive responses to altered environments. Other proposed mechanisms involve temporal gene expression patterns perturbed at critical events during development, such as implantation and early placental morphogenesis. The contribution of programming in early embryos to phenotypic variation and, more importantly, potential health status of resulting offspring has particular relevance to health and diet at the time of conception and to children born following assisted reproductive technologies, especially where embryonic manipulations in artificial environments are involved. ©2006 Eurekah.com and Springer Science+Business Media.