Immunophilin FK506-binding protein 52 (FKBP52) is a cochaperone that binds to the progesterone receptor (PR) to optimize progesterone (P 4 )-PR signaling. We recently showed that Fkbp52-deficient (Fkbp52 −/− ) mice have reduced uterine PR responsiveness and implantation failure which is rescued by excess P 4 supplementation in a genetic background-dependent manner. This finding led us to hypothesize that FKBP52 has functions in addition to optimizing PR activity. Using proteomics analysis, we found that uterine levels of peroxiredoxin-6 (PRDX6), a unique antioxidant, are significantly lower in Fkbp52 −/− mice than in WT and PR-null (Pgr −/− ) mice. We also found that Fkbp52 −/− mice with reduced uterine PRDX6 levels are susceptible to paraquat-induced oxidative stress (OS), leading to implantation failure even with P 4 supplementation. The same dose of paraquat did not interfere with implantation in WT mice. Moreover, treatment with antioxidants α-tocopherol and N-acetylcysteine (NAC) attenuated paraquat-induced implantation failure in P 4 -treated Fkbp52 −/− mice. Functional analyses using mouse embryonic fibroblasts show that Fkbp52 deficiency associated with reduced PRDX6 levels promotes H 2 O 2 -induced cell death, which is reversed by the addition of NAC or by forced expression of PRDX6, suggesting that Fkbp52 deficiency diminishes the threshold against OS by reducing PRDX6 levels. These findings provide evidence that heightened uterine OS in Fkbp52 −/− females with reduced PRDX6 levels induces implantation failure even in the presence of excess P 4 . This study shows that FKBP52-PRDX6 signaling protects pregnancy from overt OS.embryo implantation | mouse | uterus

No abstract

Although placental development and implantation depend on the coordination of trophoblast proliferation, differentiation and invasion, little is known about the cell cycle regulators that govern the control of these events. The hypothesis that the coordinated expression of cell cycle progression and inhibition factors will determine whether cytotrophoblasts proliferate or undergo cell cycle arrest or cell cycle exit allowing subsequent differentiation was tested. The cell cycle promotors cyclin A, cyclin B1, PCNA, Ki67 and the cell cycle inhibitors p21, p27 and p57 were immunolocalized in tissue sections of first trimester pregnancies (weeks 6 and 9-12). Double staining with cytokeratin 7 allowed unambiguous identification of extravillous cytotrophoblast (EVT) in the decidua. Villous cytotrophoblasts were immunolabelled for Ki67 and cyclin A but only few were stained with anti-cyclin B1. The syncytiotrophoblast was devoid of immunoreactivity for any of the cell cycle progression factors. It expressed especially p21, whereas p27 and p57 were predominantly found in villous cytotrophoblasts. PCNA, Ki67, cyclin A and cyclin B1 were immunolocalized in proximal and distal EVTs of anchoring villi and in EVT which had invaded the upper decidual segments. All EVTs strongly expressed p27 and p57, but not p21. These data clearly suggest different functions for p21, p27 and p57 in placental development with distinct roles for p21 and p57 in syncytiotrophoblast and EVT differentiation, respectively. p27 appears to be involved in both the processes. The results may also challenge the concept of differential mitotic activity in the proximal and distal parts of the first trimester cytotrophoblast cell column, but more functional studies are clearly needed. The presence of p27 and p57 in EVT cells, which invade the deciduas deeply, may account for the loss of mitogenic potential of these cells.