Abstract
European Union directives authorize the use of sewage sludge in agriculture and regulate its use in such a way as to improve the nutrient content of soils. Grazing animals allow access to grassland three weeks after the application of sludge. Sewage sludge is used as an organic fertilizer, however, it can contain potentially toxic elements, such as heavy metals and organic contaminants (PAHs, PCBs and PCDD/Fs), that can affect soil quality and be transmitted to grazing animals and then to the food chain. Consequently, processed sewage sludge provides a good model to investigate the effects of real-life exposure to complex cocktails of environmental chemicals (ECs), including endocrine disrupting compounds (EDCs). The aim of this study is to determine whether exposure of pregnant ewes and in utero and post natal life exposed adult ewes to theses environmental chemicals (via sewage sludge fertilizer by comparison to inorganic fertilizer), disrupts fetal ovary development leading to defects in the resulting adults. Fetal ovaries (110dpc) and adult ovaries (18 mouths) were collected and subjected to histological assessment and transcriptome analyses by using quantitative real-time RT-PCR on several key genes and 15K sheep oligo-microarray hybridization (Agilent). In the adult female offspring ovaries, the most striking effects were a decrease in numbers and health of ovarian follicles. From molecular biology, transcript levels of the germ cell-specific receptor cKIT was significantly increased (1.4-fold, p=0.032) and mRNA quantities for steroidogenic enzymes tended to be increased (1.8-fold StAR, 2.9-fold, p=0.014 CYP11A1, 2.72-fold CYP19). In the other hand, several transcripts were down-regulated like ESR2 (0.66-fold, p=0.036), the actin-modulator GSN (0.36-fold, p=0.04) and Cdc42EP5 (0.64-fold, p=0.022). Changes in GSN and Cdc42EP5 may have an incidence on establishment of oocyte maturation and developmental competence. Strikingly, switching the mother from control to EC-exposure pastures at conception caused different changes to the fetal ovary (110 dpc), such as a dramatic increase in follistatin in that group only. Whole of theses results show that in utero and/or post natal exposure to a complex cocktail of ECs affects ovarian gene expression that persists into adulthood and may contribute to alter the female reproductive function. (poster)
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