Tissue factor expression and methylation regulation in differentiation of embryonic stem cells into trophoblast

Expression of tissue factor and thrombomodulin in the placentas of pregnancies affected by early-onset and late-onset preeclampsia

AIM

To analyze the differential genetic expression and protein localization of thrombomodulin (THBD) and tissue factor (F3) in the placentas of pregnancies affected by preeclampsia.

METHODS

We assessed the expression of THBD and F3 by immunohistochemistry and real-time polymerase chain reaction (PCR) in placentas from 20 PE cases: 10 early-onset PE placentas, 10 late-onset PE placentas, and 10 control cases (normal pregnancies).

RESULTS

In cases, we found higher THBD and F3 RNA levels in placental tissue. Protein expression in controls differed from that in late-onset PE placentas, which had lower THBD levels in syncytiotrophoblasts and amniotic cells. Likewise, late-onset PE placentas exhibited comparatively lower F3 expression in the perivillous fibrin. In contrast, early-onset PE had high F3 expression in the subdecidual fibrin. We found no significant differences in the F3/THBD ratio between the groups.

CONCLUSION

Our study supports evidence that shows the involvement of F3 and THBD in placental disorders. Furthermore, this finding contributes to a better understanding of the physio-pathological role that these molecules may play in the development of this heterogeneous disease.

Specification of trophoblast from embryonic stem cells exposed to BMP4

Trophoblast (TB) comprises the outer cell layers of the mammalian placenta that make direct contact with the maternal uterus and, in species with a highly invasive placenta, maternal blood. It has its origin as trophectoderm, a single epithelial layer of extra-embryonic ectoderm that surrounds the embryo proper at the blastocyst stage of development. Here, we briefly compare the features of TB specification and determination in the mouse and the human. We then review research on a model system that has been increasingly employed to study TB emergence, namely the BMP4 (bone morphogenetic protein-4)-directed differentiation of human embryonic stem cells (ESCd), and discuss why outcomes using it have proved so uneven. We also examine the controversial aspects of this model, particularly the issue of whether or not the ESCd represents TB at all. Our focus here has been to explore similarities and potential differences between the phenotypes of ESCd, trophectoderm, placental villous TB, and human TB stem cells. We then explore the role of BMP4 in the differentiation of human pluripotent cells to TB and suggest that it converts the ESC into a totipotent state that is primed for TB differentiation when self-renewal is blocked. Finally we speculate that the TB formed from ESC is homologous to the trophectoderm-derived, invasive TB that envelopes the implanting conceptus during the second week of pregnancy.

Expression of flTF and asTF splice variants in various cell strains and tissues

Tissue factor (TF) expressed at the protein level includes two isoforms: The membrane-bound full-length TF (flTF) and the soluble alternatively spliced TF (asTF). flTF is the major thrombogenic form of TF, whereas asTF is more closely associated with tumor growth, angiogenesis, metastasis and cell growth. In order to further investigate the different expression and functions of TF splice variants, the expression of these two splice variants were detected in numerous cell strains and tissues in the present study. Quantitative polymerase chain reaction was used to measure the transcript levels of the TF variants in 11 human cell lines, including cervical cancer, breast cancer, hepatoblastoma, colorectal cancer and umbilical vein cells, and five types of tissue specimen, including placenta, esophageal cancer, breast cancer, cervical cancer (alongside normal cervical tissues) and non-small cell lung cancer (alongside adjacent and normal tissues). Furthermore, the effects of chenodeoxycholic acid (CDCA) and apolipoprotein M (apoM) on the two variants were investigated. The results demonstrated that flTF was the major form of TF, and the mRNA expression levels of flTF were higher than those of asTF in all specimens tested. CDCA significantly upregulated the mRNA expression levels of the two variants. Furthermore, overexpression of apoM promoted the expression levels of asTF in Caco-2 cells. The mRNA expression levels of asTF in cervical cancer tissues were significantly higher than in the corresponding normal tissues. To the best of our knowledge, the present study is the first to compare the expression of flTF and asTF in various samples. The results demonstrated that CDCA and apoM may modulate TF isoforms in different cell lines, and suggested that asTF may serve a role in the pathophysiological mechanism underlying cervical cancer development. In conclusion, the TF isoforms serve important and distinct roles in pathophysiological processes.