Location: Arkansas Children's Nutrition CenterTitle: Bone morphogenetic protein 2 (BMP2) and krüppel-like factor 9 (KLF9) cross-regulation in uterine stromal cells promotes timing of uterine endometrial receptivity Author
Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2009
Publication Date: 6/15/2009
Citation: Pabona, J.M., Simmen, F.A., Simmen, R.C. 2009. Bone morphogenetic protein 2 (BMP2) and Krüppel-like factor 9 (KLF9) cross-regulation in uterine stromal cells promotes timing of uterine endometrial receptivity [abstract]. Biology of Reproduction. 81:394. Interpretive Summary:
Technical Abstract: An out-of-phase uterus is considered to be a major cause of infertility in mammals. Delayed on-time implantation of developing blastocysts, due to asynchronous endometrial development, results in reduced litter size in mice. The dysregulation of events in the transition from a pre-receptive to a receptive uterus, and in the subsequent formation of decidual cells that support early embryo development is also considered to underlie endometriosis-associated infertility. Our laboratory has identified a novel progesterone receptor (PGR) co-activator protein, designated Krüppel-like Factor 9/Basic Transcription Element Binding Protein 1 (KLF9/BTEB1), whose absence in mice is associated with subfertility due to decreased number of implanting embryos. In the peri-implantation mouse uterus, loss of Klf9 expression leads to altered patterns of proliferation and apoptosis and aberrant P-responsiveness of uterine gene expression in all endometrial compartments. Since Klf9 expression occurs predominantly in the pre-receptive stroma, this suggests a role for KLF9 in stromal-epithelial cross-talk important for endometrial receptivity. To dissect the regulatory role of stromal KLF9 for embryo implantation, we used immortalized human endometrial stromal cell line (HESC) treated with 8-bromo-cAMP, 17ß-estradiol, and medroxyprogesterone acetate (cAME) to mimic stromal progression from a proliferative to a differentiated state. Induction of HESC into a decidualized state with cAME-treatment was accompanied by a progressive decrease in KLF9 protein levels and coincident increase in Bmp2, decidual markers insulin-like binding protein-1 (Igfbp1) and prolactin (Prl), and Pgr transcript levels. Small interfering RNA-mediated silencing of Klf9 decreased Pgr, and increased Bmp2 expression, with no effects on Igfbp1 and Prl. To test the existence of a negative regulatory loop between Klf9 and Bmp2, recombinant BMP2 (100 ng/ml) was added to HESC and the expression levels of Klf9 and other stromal genes were evaluated 48 h later. Whereas BMP2 exposure increased Igfbp1 and Prl, downstream target Wnt4, and KLF9-related member Klf13 expression, that for Klf9 and Pgr (A/B, B) was significantly attenuated (>50%) by this treatment. In mouse uteri of early pregnancy (dpc0.5=vaginal plug), the pattern of Bmp2 expression (dpc4.5>dpc3.5=dpc2.5) was inversely associated with that of Klf9 (dpc2.5>dpc3.5>dpc4.5) and followed that of Igfbp1. Klf9 null mutants showed higher uterine Bmp2 expression at dpc3.5 but not at dpc2.5 and dpc4.5 when compared to WT, and this coincided with increased Klf13 transcript levels. Results suggest that KLF9 negative regulation of Bmp2 expression and BMP2 positive regulation of Klf13 are permissive to the timely progression of stromal and epithelial proliferation prior to decidual formation. Since de-repression of Bmp2 is requisite for endometrial receptivity, KLF9's function as a molecular brake for BMP2 could be manipulated to advance uterine receptivity in clinical conditions where delayed endometrial maturation may lead to unsuccessful outcome.