Decreased expression of fibroblast growth factor-4 and associated dysregulation of trophoblast differentiation in mouse blastocysts exposed to high D-glucose in vitro

Aims/hypothesis. Paracrine interactions are thought to operate between the inner cell mass and trophectoderm cell lineages to co-ordinate their expansion and differentiation during embryo implantation. We aimed to determine whether hyperglycaemia could interfere with this regulatory process. Methods. Mouse blastocysts were pre-exposed to either control or high concentrations of D-glucose for 24 h in vitro and tested for their ability to attach and spread over a fibronectin-coated culture substrate. Quantitative immunocytochemistry was done on blastocysts to assess the protein expression of Fibroblast Growth Factor-4, a growth factor preferentially produced by the inner cell mass and thought to restrict trophectoderm differentiation into giant trophoblasts. Experiments were then done combining the pre-exposure to high D-glucose with the addition of recombinant fibroblast growth factor-4. Results. Compared with control blastocysts, high D-glucose prc-treated embryos were found to form 18% larger trophoblast outgrowths. These blastocysts also showed a 30% reduction in the expression of fibroblast growth factor-4 protein by inner cell mass cells as they were outgrowing. The trophoblast surface area per outgrowth and the trophoblast nuclear area were corrected when the addition of recombinant fibroblast growth factor-4 was combined with the pre-exposure to high D-glucose. Conclusion/interpretation. The data suggests that trophectoderm differentiation is impaired by high D-glucose and that this effect is secondary to a deficiency in fibroblast growth factor-4 protein in the inner cell mass. These observations add a novel perspective to the study of the peri-implantation embryopathy associated with maternal diabetes.