Introduction:Implantation begins with attachment of the blastocyst's trophectoderm to the endometrium luminal epithelium. The trophectoderm cells then differentiate into trophoblast lineages that will eventually contribute to the placenta. Carriers of balanced reciprocal translocations have an increased risk for repeated implantation failures.We have recently derived human embryonic stem cells (hESC) carrying unbalanced t(11;22) translocation, and showed that they can differentiate into cells from all three germ layers, but fail to differentiate into βhCG secreting trophoblast cells.
Aim:To study the molecular mechanisms leading to impaired trophoblast differentiation in translocated hESCs and to compare the attachment of trophoblast cells from t(11;22) and control hESCs to endometrium cells.
Materials and Methods:Translocated and control hESCs werein vitrodifferentiated into trophoblasts. Differentiation was assessed by βhCG secretion and expression of trophoblast markers. hESCs differentiated into trophoblasts were than aggregated to create trophoblast vesicles (TBV), that will be used for functional assays of attachment and invasion to endometrial cells
Results:Differentiated control-hESCs expressed all trophoblast genes examined; CDX2, KRT7, GCM1, PPARG, KLF4, TP63 and CGA, and secreted increasing levels ofbhCG. In contrast, differentiated translocated-hESCs displayed reduced and delayed expression of the trophoblastic genes, concomitant with their failure to secretebhCG. TBVs derived from control-hESCs expressed extravillous trophoblast markers, and constantly secreted βhCG. These control TBVs are currently compared to translocated TBVs.
Conclusions:Our results suggest that impaired expression of trophoblastic genes in t(11;22) cells prevents correct trophoblast differentiation, leading to reduced βhCG expression and probably to implantation failure in translocation carriers.
