Environment and intergenerational health axis
Scientist have come to see the reproductive system as a “sensor” of favorable and unfavorable conditions and this concept has led to a new field of study within CRDSI: the link between the environment and intergenerational health. In this context, diary reproduction represent a very interesting case. Indeed, the objective of dairy producers is to induce gestation during the milk production peak in order for parturition to occur at the end of the lactation period. However, it appears that a cow’s fertility is low during this critical period. This decrease in fertility is thought to be associated with foetal oocyte programming during which the mother’s metabolism status sends an adaptive signals to the foetus that results in a decrease in fertility in the offspring. The biological, cellular and molecular processes involved are still unknown but the epigenetic origin of the adaptation to a particular environment is currently favored.
This link between reproductive functions, the quality of the environment and offspring performance is getting more evident in human. Indeed, various studies demonstrate an increased risk of developing different diseases following, for example, in vitro fertilization or when pregnancy conditions are not suitable or even when parents are overweight. In vitro fertilization is also associated to an increased risk of developing diseases associated to imprinted genes such as Beckwith-Wiedemann, Silver Russel, Angelmann or Prader Willi syndromes. Imprinted genes are defined as genes for which only one of the two alleles (coming from either the mother or the father) is expressed. The expression of the two alleles is responsible for various syndromes and it seems that the environment in which the early embryo develops will influence the establishment of epigenetic marks that control imprinting. It is also becoming evident that early and foetal development represent a sensitive window of plasticity toward genome programming, which can have long term impacts. Adaptation to the environmental conditions by his mother could thus be responsible for metabolic disorders later in the adult’s life. It has also been demonstrated that parents’ life habits, either on the mother’s or father’s side, influence the quality of gametes and the epigenetic marks in their genome. Some of the marks that have been observed to change in parents exposed to different environmental condition are also detected in the embryo formed by these gametes. This creates a paradigm shift according to which misadaptation to one’s environment has the potential to be transmitted to the offspring and create intergenerational impacts due to life circumstances. Among these circumstances are the parents’ metabolic status and diet but also exposition to the different environmental toxins. The study of the intergenerational transmission of lifestyle habits and of the disruptions created by an exposition to toxicological products found in the environment are emerging research sectors that closely involve the biological processes of reproduction.
As such, many members of CRDSI have in the past few years added many aspects related to the influence of environmental conditions on the reproductive functions and gamete quality to their research curriculum. On the eco-toxicological side, Janice Bailey has been working on the impact of organochloride contamination in the North on sperm and oocyte quality an on its potential to induce pathologies in the offspring. Marc-André Sirard studies the genomic and epigenetic impacts of many chlorination products on the porcine embryo as a model. Géraldine Delbès complements this research by studying the impact of ozonation by-products in water treatment on testicular functions while Jacques J. Tremblay works on the impact of plasticizer, known endocrine disruptors, on the same functions. The reproductive process implies great changes at the cellular and molecular levels and since these event occur during critical steps in the conception of a new organism, the reproductive process represents an opportunity window for genetic/epigenetic dysregulation that can lead to disease development.
The teams ofClaude Robertand Marc-André Sirard also work on studying the impact of growth conditions on the young embryo, on its quality and on its genetic and epigenetic programming with a special focus the potential deviation in these programs that could lead to consequences in adult life. These work take into consideration disturbance occurring during the first week of life while Emmanuel Bujold and Nils Chaillet study a larger window by considering the influence of pregnancy conditions during the first months of life. The objectives of their work is to study the very early clinical signs leading to the development of perinatal diseases such a preeclampsia. Continuing along the time scale,Yves Tremblay’s research program is dedicated to the sudden infant death syndrome which affects boys more often than girls. This work show that lung development is governed not only by sexual hormones but also by complex impacts of environmental determinants.