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The cytotrophoblast (or layer of Langhans) is the inner layer of the trophoblast. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo. The cytotrophoblast is considered to be the trophoblastic stem cell because the layer surrounding the blastocyst remains while daughter cells differentiate and proliferate to function in multiple roles. There are two lineages that cytotrophoblastic cells may differentiate through: fusion and invasive. The fusion lineage yields syncytiotrophoblast and the invasive lineage yields interstitial cytotrophoblast cells.〔Handwerger, S. (2010). "New insights into the regulation of human cytotrophoblast cell differentiation." ''Molecular and Cellular Endocrinology'', 323(1), 94-104.〕 Cytotrophoblastic cells play an important role in the implantation of a newly fertilized egg in the uterus. ==Fusion Lineage== The formation of all syncytiotrophoblast is from the fusion of two or more cytotrophoblasts via this fusion pathway. This pathway is important because the syncytiotrophoblast plays an important role in fetal-maternal gas exchange, nutrient exchange, and immunological and metabolic functions. An undifferentiated cytotrophoblastic stem cell will differentiate into a villous cytotrophoblast, which is what constitutes primary chorionic villi, and will eventually coalesce into villous syncytiotrophoblast. The formation of syncytiotrophoblast from cytotrophoblast is a terminal differentiation step of trophoblastic cells.〔Bischof, P., & Irminger-Finger, I. (2005). "The human cytotrophoblastic cell, a mononuclear chameleon." ''International Journal of Biochemistry & Cell Biology'', 37(1), 1-16.〕 Syncytialization of cytotrophoblastic cells can be induced ''in vitro'' through multiple signalling molecules including epidermal growth factor, glucocorticoids, and human chorionic gonadotropin.〔Dakour, J., Li, H., Chen, H., & Morrish, D. W. (1999). "EGF promotes development of a differentiated trophoblast phenotype having c-myc and junB proto-oncogene activation." ''Placenta'', 20, 119–126.〕〔Cronier, L., Alsat, E., Hervé, J. C., Delèze, J., & Malassiné, A. (1998). "Dexamethasone stimulates gap junctional communication, peptide hormone production and differentiation of human term trophoblast." ''Trophobl''. Res., 11, 35–49.〕〔Yang, M., Lei, Z. M., & Rao, Ch. V. (2003). "The central role of human chorionic gonadotropin in the formation of human placental syncytium." ''Endocrinology'', 144, 1108–1120.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cytotrophoblast」の詳細全文を読む スポンサード リンク
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