Effects of polychlorinated biphenyls (PCBs) on the development of sheep blastocysts

Introduction: PCBs are ubiquitary pollulants, that can act as disrupting-endocrine compounds. Thanks to theirlipophilic nature and the absence of a metabolic pathway for degradation, PCBs can accumulate in mammaliantissues, including female genital tract. Thus, they represent an important factor of risk for female reproductivecapacity and for embryonic development. Our aim was to evaluate whether a short exposure to PCBs can influencethe development of sheep blastocyst stage embryos.Methods: Hatched blastocysts produced in vitro our previously described protocols has been incubated with themixture of 60 congeners of PCBs (Aroclor 1254) at two different concentrations (20 ng/ml and 40 ng/ml) for 48h.The concentration of PCBs has been selected in respect to those found in functional reproductive organs (follicularfluid and uterine secretions) in women chronically exposed to PCBs. Following the exposure, the analysis ofembryos has been performed by gross morphology, ultrastructure, and immunocytochemistry.Results and Discussion: Gross morphological observation revealed an extended necrosis and vacuolation inblastocysts treated with Aroclor-1254. The ultrastructural analysis confirmed the presence of marked cytoplasmicvacuolation and revealed the presence of mitochondria with loss of cristae, increased matrix density and reductionof size in PCBs treated blastocysts. In the cytoplasm, an number of lipid droplets of increased diameter andnumerous large single membrane-bound vacuoles has been observed. A dose dependent significant increase inapoptotic cells (TUNEL) has been observed in embryos incubated with 20 ng/ml (237/1438;16%) and 40 ng/ml(470/1623; 29%) vs. control (112/1130;10%) and vehicle treated (110/1130;10%) control groups (P<0.02). Similarly,Bromodeoxiuridine incorporation, assay confirm a dose dependent decrease in growth of embryos incubated with20 ng/ml (1305/2814; 46%) and 40 ng/ml (456/1381; 33%) comparing to both, untreated control (518/863; 60%) andvehicle (553/916; 60%) groups (P<0.03). Our results show that even a short exposure to PCBs can effect embryodevelopment.[...]