Abstract
BackgroundIn the fusion pathway of trophoblast differentiation, stem villous cytotrophoblast cells proliferate and daughter cells differentiate and fuse with existing syncytiotrophoblast to maintain the multi-nucleated layer. Integrin-linked kinase (ILK) is highly expressed in 1st and 2nd trimester villous cytotrophoblast cells, yet barely detectable in syncytiotrophoblast, thus we examined the potential role of ILK in aiding trophoblast fusion.MethodsThe temporal/spatial expression and activity of ILK were determined in BeWo cells undergoing syncytialization by immunoblot and immunofluorescence analyses. BeWo cells were also transfected with pEGFP expression vectors containing wildtype or two mutant ILK cDNA constructs. The incidence of cell fusion in transfected cells grown under syncytialization conditions was then scored by the presence or absence of E-cadherin immunostaining. Beta-hCG expression in transfected cells, a marker of syncytiotrophoblast hormonal differentiation, was also similarly assessed.ResultsILK catalytic activity increased and ILK began to increasingly localize to BeWo cell nuclei during syncytialization in correlation with increased pAkt and Snail protein expression. Syncytialization was also significantly elevated (p < 0.05) in BeWo cells expressing constitutively active (ca)-ILK vs cells containing empty vector or dn-ILK. Furthermore, cytoplasmic Beta-hCG expression markedly increased (p < 0.05) in cells expressing wt- and ca-ILK.ConclusionILK-facilitated syncytialization is dependent, at least in part, on ILK catalytic activity while hormonal differentiation appears dependent on both ILK-associated protein interactions and catalytic activity. This study demonstrates that ILK plays a novel role in BeWo syncytialization and differentiation, perhaps through an ILK-Akt-Snail pathway, and implicates ILK in the same process in villous cytotrophoblasts in vivo.
Highlights
In the fusion pathway of trophoblast differentiation, stem villous cytotrophoblast cells proliferate and daughter cells differentiate and fuse with existing syncytiotrophoblast to maintain the multi-nucleated layer
Morphometric analyses have indicated that in the first trimester there is an excess of villous cytotrophoblast cells fusing with the syncytiotrophoblast – likely necessary for the metabolic integrity of the syncytiotrophoblast [7], Ellery et al [8] has recently demonstrated that a proportion of nuclei in the syncytiotrophoblast are actively engaged in transcription in accordance with the high metabolic and secretory activity of the tissue
(page number not for citation purposes) http://www.rbej.com/content/7/1/51 phoblast choriocarcinoma and is well known to undergo syncytialization upon forskolin treatment [32]. This cell line model is ideal for experiments because syncytialization can be controlled with syncytialization of up to 80% [33]. They can be grown under proliferating conditions indefinitely where they exhibit an epithelial phenotype or under syncytialization conditions where it is well known that BeWo cells express markers of syncytiotrophoblast such as β-human chorionic gonadotropin (β-hCG), syncytin, and markedly decreased E-cadherin and desmoplakin expression [15,24,33,34,35,36]
Summary
In the fusion pathway of trophoblast differentiation, stem villous cytotrophoblast cells proliferate and daughter cells differentiate and fuse with existing syncytiotrophoblast to maintain the multi-nucleated layer. In the cytotrophoblast layer, polarized stem cytotrophoblast cells proliferate and daughter cells differentiate and fuse with existing syncytiotrophoblast to maintain the multi-nucleated layer [reviewed by [6]]. Since the villous cytotrophoblast and syncytiotrophoblast comprise the epithelial covering of the chorionic villi that is in contact with maternal blood, any disturbances in the processes of cytotrophoblast proliferation and fusion of cytotrophoblast with overlying syncytiotrophoblast can seriously perturb the turnover and function of the syncytiotrophoblast layer and may contribute to development of fetal growth restriction or preeclampsia [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
