A and B, Overexpression of Cx43 induces ESC up-regulation of IL-11 in the absence of hormone treatment. Transgenic expression of Cx43 dose responsively up-regulates IL-11 secretion, with 2.0 μg per 6-cm dish approaching approximately 50% the magnitude of secretion after 7 days of exposure to E/P/c (panel A). The combination of recombinant Cx43 and decidual hormones have a more than additive effect on IL-11 secretion (panel B). *, P < .05, t tests (different from corresponding controls). C, Overexpression of Cx43 up-regulates VEGF and IL-11 production in ESCs. Transfection of 1.0 μg Cx43 vector DNA per 6-cm dish increased VEGF secretion by 2.3-fold and IL-11 by 7.2-fold, but these responses were lower than those induced by E/P/c for 7 days (H), *, P < .05, t tests (different from control). Additive effects were noted when transfection was combined with E/P/c treatment (Cx43+H), **, P < .05, t tests (different from corresponding Cx43 transfection controls [Cx43]).