Involvement of gap junctional communication and connexin expression in trophoblast differentiation of the human placenta.

Gap junctional intercellular communication (GJIC) permits coordinated cellular activities during development and differentiation processes, and its dysfunction or mutation of connexin genes have been irnplicated in pathologies. In the human placenta, two distinct differentiation pathways of cytotrophoblastic cell coexist leading to a double model: fusion phenotype (villous trophoblast) and proliferative/invasive phenotype (extravillous trophoblast). This review focuses on current knowledge on the connexin expression and the irnplication of GJIC in trophoblastic differentiation. Experimental evidence obtained in hurnan placenta demonstrates the involvement of connexin 43-gap junctions in the trophoblastic fusion process and of a connexin switch during the spatially and ternporally controlled proliferation/invasion process.