Chorionic Type IT

This type of IT is located in the chorion laeve (fetal membrane). Unlike implantation site intermediate trophoblastic cells, the functional role of chorionic-type intermediate trophoblastic cells remains speculative. Chorionic-type IT may contribute to the synthesis of extracellular matrix, which is required to maintain the tensile strength of the fetal membrane (23). It is also possible that chorionic-type IT acts as a biological and mechanical barrier to the maternal immune system and is important for fetal allograft survival. Chorionic-type intermediate trophoblastic cells express HLA-G and p63, but hPL and CD146 are expressed only focally (Table 1) (5,24). Chorionic-type intermediate trophoblastic cells are believed to differentiate from CT, but the molecular mechanisms that underlie this process are unknown. aNp63 is expressed by CT and TAp63 is expressed by chorionic-type intermediate trophoblastic cells. It is conceivable that an isoform switch from aNp63 to TAp63 may be important for the transformation of CT into chorionic-type IT in the fetal membranes (8). Further, in vitro studies are required to determine whether this interpretation is correct.

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