The process of implantation, necessary for all viviparous birth, consists of tightly regulated events, including apposition of the blastocyst, attachment to the uterine lumen, and differentiation of the uterine stroma. In rodents and primates the uterine stroma undergoes a process called decidualization. Decidualization, the process by which the uterine endometrial stroma proliferates and differentiates into large epithelioid decidual cells, is critical to the establishment of fetal-maternal communication and the progression of implantation. The role of bone morphogenetic protein 2 (Bmp2) in regulating the transformation of the uterine stroma during embryo implantation in the mouse was investigated by the conditional ablation of Bmp2 in the uterus using the (PR-cre) mouse. In rodents and primates the process of implantation consists of attachment and invasion of the uterine luminal epithelium. Successful embryo implantation in these species requires the rapid remodeling of the uterine stromal cells in a process termed decidualization (as reviewed previously [30]). Decidualization is a process characterized by morphological and functional changes in the uterine stromal cells that is characterized by endometrial stroma proliferation and differentiation into large epithelioid decidual cells. This process is critical for establishment of a fetal-maternal interface during implantation. Although the expression of many genes, including steroid hormone receptors, cytokines, growth factors, and several developmental factors, has been implicated in this process, direct in vivo evidence of gene function has been limited. This is largely due to the fact that the ablation of many of the genes implicated in this process result in early lethality or other developmental consequences that preclude further study. Here we investigate the role of a member of the bone morphogenetic protein family, Bmp2, in the process of embryo implantation.Bone morphogenetic proteins (Bmps) are multifunctional growth factors that belong to the transforming growth factor ␤ (TGF-␤) superfamily. The roles of Bmps in embryonic development and cellular functions in postnatal and adult animals have been extensively studied in recent years. The activity of Bmp growth factors was first described in the induction of bone formation (56). Bmp2 was identified later as a soluble factor capable of inducing ectopic cartilage and bone formation in vivo when implanted into muscular tissues (58, 61). Numerous studies have characterized the role of Bmp2 as an essential osteoblast and osteoclast differentiation factor (reviewed in reference 5). Mice with a targeted deletion of Bmp2 are embryonic lethal due to a failure of proamniotic canal closure in the majority of mice or abnormal cardiac development in the surviving mice (67). In the uterus of pregnant mice, Bmp2 expression is absent in the preimplantation period and during implantation is initially detected in the stroma surrounding the site of blastocyst attachment. As implantation progresses, expression of Bmp2 ...

The hedgehog family of morphogens are regulators of cell proliferation, differentiation and cell-cell communication. These morphogens have been shown to have important roles in organogenesis, spermatogenesis, stem cell maintenance and oncogenesis. Indian hedgehog (encoded by Ihh) has been shown to be expressed in the uterine epithelium under the control of the steroid hormone, progesterone. Although in vivo and in vitro studies have shown that progesterone achieves its effects on uterine function through epithelial-stromal cross-talk, molecular mediator(s) for this cellular communication pathway have not been elucidated. Using new experimental approaches that ablate Ihh specifically in Pgr-positive uterine cells of the mouse, we demonstrate that Ihh is an essential mediator of Pgr action in the uterus, and expression of this factor is critical in mediating the communication between the uterine epithelium and stroma required for embryo implantation.

The segmental premature aging disease, Hutchinson-Gilford Progeria (HGPS) is caused by a truncated and farnesylated form of Lamin A. In a mouse model for HGPS, a similar Lamin A variant causes the proliferative arrest and death of post-natal but not embryonic fibroblasts. Arrest is due to an inability to produce a functional extracellular matrix (ECM), as growth on normal ECM rescues proliferation. The defects are associated with inhibition of canonical Wnt signaling, due to reduced nuclear localization and transcriptional activity of Lef1, but not Tcf4, in both mouse and human progeric cells. Defective Wnt signaling, affecting ECM synthesis, maybe critical to the etiology of HGPS as mice exhibit skeletal defects and apoptosis in major blood vessels proximal to the heart. These results establish a functional link between the nuclear envelope/lamina and the cell surface/ECM and may provide insights into the role of Wnt signaling and the ECM in aging.

Progesterone and estrogen are critical regulators of uterine receptivity. To facilitate uterine remodeling for embryo attachment, estrogen activity in the uterine epithelia is attenuated by progesterone; however, the molecular mechanism by which this occurs is poorly defined. COUP-TFII (chicken ovalbumin upstream promoter transcription factor II; also known as NR2F2), a member of the nuclear receptor superfamily, is highly expressed in the uterine stroma and its expression is regulated by the progesterone–Indian hedgehog–Patched signaling axis that emanates from the epithelium. To further assess COUP-TFII uterine function, a conditional COUP-TFII knockout mouse was generated. This mutant mouse is infertile due to implantation failure, in which both embryo attachment and uterine decidualization are impaired. Using this animal model, we have identified a novel genetic pathway in which BMP2 lies downstream of COUP-TFII. Epithelial progesterone-induced Indian hedgehog regulates stromal COUP-TFII, which in turn controls BMP2 to allow decidualization to manifest in vivo. Interestingly, enhanced epithelial estrogen activity, which impedes maturation of the receptive uterus, was clearly observed in the absence of stromal-derived COUP-TFII. This finding is consistent with the notion that progesterone exerts its control of implantation through uterine epithelial-stromal cross-talk and reveals that stromal-derived COUP-TFII is an essential mediator of this complex cross-communication pathway. This finding also provides a new signaling paradigm for steroid hormone regulation in female reproductive biology, with attendant implications for furthering our understanding of the molecular mechanisms that underlie dysregulation of hormonal signaling in such human reproductive disorders as endometriosis and endometrial cancer.

Endometrioid adenocarcinoma is the most frequent form of endometrial cancer, usually developing in pre-and peri-menopausal women. β-catenin abnormalities are common in endometrioid type endometrial carcinomas with squamous differentiation. To investigate the role of β-catenin (Ctnnb1) in uterine development and tumorigenesis, mice were generated which expressed a dominant stabilized β-catenin or had β-catenin conditionally ablated in the uterus by crossing the PR Cre mouse with the Ctnnb1 f(ex3)/+ mouse or Ctnnb1 f/f mouse, respectively. Both of the β-catenin mutant mice have fertility defects and the ability of the uterus to undergo a hormonally induced decidual reaction was lost. Expression of the dominant stabilized β-catenin, PR cre/+ Ctnnb1 f(ex3)/+ , resulted in endometrial glandular hyperplasia, whereas ablation of β-catenin, PR cre/+ Ctnnb1 f/f , induced squamous cell metaplasia in the murine uterus. Therefore, we have demonstrated that correct regulation of β-catenin is important for uterine function as well as in the regulation of endometrial epithelial differentiation.

Progesterone (P4) acting through its cognate receptor, the progesterone receptor (PR), plays an important role in uterine physiology. The PR knockout (PRKO) mouse has demonstrated the importance of the P4-PR axis in the regulation of uterine function. To define the molecular pathways regulated by P4-PR in the mouse uterus, Affymetrix MG U74Av2 oligonucleotide arrays were used to identify alterations in gene expression after acute and chronic P4 treatments. PRKO and wild-type mice were ovariectomized and then treated with vehicle or 1 mg P4 every 12 h. Mice were killed either 4 h after the first injection (acute P4 treatment) or after the fourth injection of P4 (chronic P4 treatment). At the genomic level, the major change in gene expression after acute P4 treatment was an increase in the expression of 55 genes. Conversely, the major change in gene expression after chronic P4 treatment was an overall reduction in the expression of 102 genes. In the analysis, retinoic acid metabolic genes, cytochrome P 450 26a1 (Cyp26a1), alcohol dehydrogenase 5, and aldehyde dehydrogenase 1a1 (Aldh1a1); kallikrein genes, Klk5 and Klk6; and specific transcription factors, GATA-2 and Cited2 [cAMP-corticosterone-binding protein/p300-interacting transactivator with glutamic acid (E) and aspartic acid (D)-rich tail], were validated as regulated by the P4-PR axis. Identification and analysis of these responsive genes will help define the role of PR in regulating uterine biology.

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Normal endometrial function requires a balance of progesterone (P4) and estrogen (E2) effects. An imbalance caused by increased E2 action and/or decreased P4 action can result in abnormal endometrial proliferation and, ultimately, endometrial adenocarcinoma, the fourth most common cancer in women. We have identified mitogen-inducible gene 6 (Mig-6) as a downstream target of progesterone receptor (PR) and steroid receptor coactivator (SRC-1) action in the uterus. Here, we demonstrate that absence of Mig-6 in mice results in the inability of P4 to inhibit E2-induced uterine weight gain and E2-responsive target genes expression. At 5 months of age, the absence of Mig-6 results in endometrial hyperplasia. Ovariectomized Mig-6 d/d mice exhibit this hyperplastic phenotype in the presence of E2 and P4 but not without ovarian hormone. Ovariectomized Mig-6 d/d mice treated with E2 developed invasive endometrioid-type endometrial adenocarcinoma. Importantly, the observation that endometrial carcinomas from women have a significant reduction in MIG-6 expression provides compelling support for an important growth regulatory role for Mig-6 in the uterus of both humans and mice. This demonstrates the Mig-6 is a critical regulator of the response of the endometrium to E2 in regulating tissue homeostasis. Since Mig-6 is regulated by both PR and SRC-1, this identifies a PR, SRC-1, Mig-6 regulatory pathway that is critical in the suppression of endometrial cancer.estrogen ͉ endometrial cancer ͉ progesterone ͉ progesterone receptor ͉ SRC-1