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 expans ion and differentiation during embryo implantation. We aimed to determine w hether hyperglycaemia could interfere with this regulatory process. Methods. Mouse blastocysts were pre-exposed to either control or high conce ntrations of D-glucose for 24 h in vitro and tested for their ability to at tach and spread over a fibronectin-coated culture substrate. Quantitative i mmunocytochemistry 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 i nto giant trophoblasts. Experiments were then done combining the pre-exposu re to high D-glucose with the addition of recombinant fibroblast growth fac tor-4. Results. Compared with control blastocysts, high D-glucose prc-treated embr yos 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 w ith the pre-exposure to high D-glucose. Conclusion/interpretation. The data suggests that trophectoderm differentia tion is impaired by high D-glucose and that this effect is secondary to a d eficiency in fibroblast growth factor-4 protein in the inner cell mass. The se observations add a novel perspective to the study of the peri-implantati on embryopathy associated with maternal diabetes.