ABB  Vol.3 No.6 A , October 2012
Increased resistance to apoptosis during differentiation and syncytialization of BeWo choriocarcinoma cells
Abstract: Transition from mononuclear villous cytotrophoblast into multinuclear syncytiotrophoblast in the human placenta is accompanied by changes in apoptosis-related proteins and an apparent increased resistance to induced apoptosis. We investigated the specific nature and timing of changes in Bcl-2, Bax, p53, and caspases 3 and 8 in forskolin-treated BeWo choriocarcinoma cells, a model for villous cytotrophoblast differentiation. BeWo cells were treated with forskolin or vehicle alone for up to 72 h and evaluated at 24 h intervals for syncytialization and quantitative expression specific apoptosis-related proteins and mRNAs. Syncytialization was quantified using fluorescent staining of intercellular membranes and enumeration of the percentage of nuclei in multinucleate cells, and differential localization of apoptosis-related proteins to multinuclear or mononuclear cells was determined by quantitative immunofluorescence. Forskolin treatment for up to 72 h resulted in 80% syncytialization, increased expression of Bcl-2 protein (P < 0.01) and mRNA (P < 0.05), and significantly decreased expression of protein and mRNA for Bax, p53, and caspases 3 and 8. Syncytialized cells expressed higher levels of Bcl-2 protein concurrent with increased resistance to cisplatin-induced apoptosis. Thus, syncytialization of BeWo cells was accompanied by altered transcription of apoptotic-related proteins characteristic of increased apoptosis resistance secondary to increased expression of the anti-apoptotic protein Bcl-2 and diminish expression of pro-apoptotic proteins.
Cite this paper: Wei, B. , Xu, C. and Rote, N. (2012) Increased resistance to apoptosis during differentiation and syncytialization of BeWo choriocarcinoma cells. Advances in Bioscience and Biotechnology, 3, 805-813. doi: 10.4236/abb.2012.326100.

[1]   Straszewski-Chavez, S.L., Abrahams, V.M. and Mor, G. (2005) The role of apoptosis in the regulation of trophoblast survival and differentiation during pregnancy. Endocrine Reviews, 26, 877-897.

[2]   Heazell, A.E.P. and Crocker, I.P. (2008) Live and let die-regulation of villous trophoblast apoptosis in normal and abnormal pregnancies. Placenta, 29, 772-783.

[3]   Huppertz, B., Frank, H.G., Kingdom, J.C., Reister, F. and Kaufmann, P. (1998) Villous cytotrophoblast regulation of the syncytial apoptotic cascade in the human placenta. Histochemistry and Cell Biology, 110, 495-508.

[4]   Huppertz, B., Frank, H.G., Reister, F., Kingdom, J., Korr, H. and Kaufmann, P. (1999) Apoptosis cascade progresses during turnover of human trophoblast: analysis of villous cytotrophoblast and syncytial fragments in vitro. Laboratory Investigation, 79, 1687-1702.

[5]   Ratts, V.S., Tao, X.J., Webster, C.B., et al. (2000) Expression of BCL-2, BAX and BAK in the trophoblast layer of the term human placenta: a unique model of apoptosis within a syncytium. Placenta, 21, 361-366.

[6]   Huppertz, B., Tews, D.S. and Kaufmann, P. (2001) Apoptosis and syncytial fusion in human placental trophoblast and skeletal muscle. International Review of Cytology, 205, 215–253.

[7]   Danihel, L., Gomolcak, P., Korbel, M., et al. (2002) Expression of proliferation and apoptotic markers in human placenta during pregnancy. Acta Histochemica, 104, 335-338.

[8]   Ishihara, N., Matsuo, H., Murakoshi, H., Laoag-Fernandez, J.B., Samoto, T. and Maruo, T. (2002) Increased apoptosis in the syncytiotrophoblast in human term placentas complicated by either preeclampsia or intrauterine growth retardation. American Journal of Obstetrics and Gynecology, 186, 158-166.

[9]   Ishihara, N., Matsuo, H., Murakoshi, H., Laoag-Fernandez, J., Samoto, T. and Maruo, T. (2000) Changes in proliferative potential, apoptosis and Bcl-2 protein expression in cytotrophoblasts and syncytiotrophoblast in human placenta over the course of pregnancy. Endocrine Journal, 47, 317-327.

[10]   Ka, H. and Hunt, J.S. (2003) Temporal and spatial patterns of expression of inhibitors of apoptosis in human placentas. American Journal of Pathology, 163, 413-422.

[11]   Black, S., Kadyrov, M., Kaufmann, P., Ugele, B., Emans, N. and Huppertz, B. (2004) Syncytial fusion of human trophoblast depends on caspase 8. Cell Death and Differentiation, 11, 90-98.

[12]   Huppertz, B., Frank, H.G. and Kaufmann, P. (1999) The apoptosis cascade -morphological and immunohistochemical methods for its visualization. Anatomy and Embryology (Berl), 200, 1-18.

[13]   Yusuf, K., Smith, S.D., Sadovsky, Y. and Nelson, D.M. (2002) Trophoblast differentiation modulates the activity of caspases in primary cultures of term human trophoblasts. Pediatric Research, 52, 411-415.

[14]   Hu, C., Smith, S.D., Pang, L., Sadovsky, Y. and Nelson, D.M. (2006) Enhanced basal apoptosis in cultured term human cytotrophoblasts is associated with a higher expression and physical interaction of p53 and Bak. Placenta, 27, 978-983.

[15]   Rote, N.S., Chang, J., Katsuragawa, H., Ng, A.K., Lyden, T.W. and Mori, T. (1995) Expression of phosphatidylserine-dependent antigens on the surface of differentiating BeWo human choriocarcinoma cells. American Journal of Reproductive Immunology, 33, 114-121.

[16]   Das, M., Xu, B., Lin, L., Chakrabarti, S., Shivaswamy, V. and Rote, N.S. (2004) Phosphatidylserine efflux and intercellular fusion in a BeWo model of human villous cytotrophoblast. Placenta, 25, 396-407.