Cyclic and characteristic expression of phosphorylated Akt in human endometrium and decidual cells in vivo and in vitro.

BACKGROUND Akt is activated by phosphorylation and plays an important role in cell survival and maintenance of structure. METHODS We investigated whether phosphorylated Akt was characteristically expressed in human endometrium in vivo and whether insulin-like growth factor-I (IGF-I) can activate Akt using cultured decidualized human stromal cells in vitro, using immunohistochemistry and Western blotting analysis. RESULTS The levels of phosphorylated Akt protein increased markedly in the decidual tissues from ectopic pregnancy. The expression of phosphorylated Akt protein in stromal cells increased with the decidualization. The decidual cells showed strong cytoplasmic staining for phosphorylated Akt. However, cultured decidualized human stromal cells diminished phosphorylated Akt expression compared to control cells. IGF-I administration to decidualized human stromal cells significantly recovered pAkt expression. The effect of IGF-I on decidualized human stromal cells was blocked by an inhibitor of phosphatidylinositol-3 kinase (PI3K) (LY294,002). These results suggest that IGF-I may activate Akt via PI3K in human endometrium and decidua. The expression of phosphorylated Akt in stromal cells was only detected in the functional layer, where tissue remodelling occurs during menstruation or implantation. CONCLUSIONS Akt activation may be involved in cell survival and extracellular matrix remodelling in human endometrium and decidua.