Generation of mice expressing only the long form of the prolactin receptor reveals that both isoforms of the receptor are required for normal ovarian function.

Prolactin (PRL), a pleiotropic hormone essential for maintenance of corpus luteum (CL) function and pregnancy, transduces its signal through two types of receptors, a short form (PRLR-S) and a long form (PRLR-L). Both types of receptors are expressed in the CL, yet their individual roles are not well defined. We have shown previously that female transgenic mice expressing only PRLR-S display total infertility characterized by defective follicular development and early degeneration of CL, suggesting that expression of PRLR-L is a prerequisite for normal follicular development and maintenance of CL.

Prolactin signaling mechanisms in ovary.

Prolactin is a hormone that is essential for normal reproduction and signals through two types of receptors. Not only is the classical long form of the prolactin receptor identified, but so are many short form receptors in rodents and human tissues. Mouse mutagenesis studies have offered insight into the biology of prolactin family, providing compelling evidence that the different isoforms have independent biological activity.

The stimulation of HSD17B7 expression by estradiol provides a powerful feed-forward mechanism for estradiol biosynthesis in breast cancer cells.

Our laboratory has previously cloned and purified an ovarian protein found to be a novel 17β-hydroxysteroid dehydrogenase type 7 enzyme (HSD17B7) (formerly prolactin receptor-associated protein) that converts the weak estrogen, estrone, to the highly potent estradiol. The regulation of this enzyme has not yet been explored. In this report, we show high expression of HSD17B7 in human ductal carcinoma and breast cancer cell lines and present evidence for a strong up-regulation of this enzyme by estradiol at the level of mRNA, protein expression, and promoter activity in MCF-7 cells.

Inhibition of MAPK by prolactin signaling through the short form of its receptor in the ovary and decidua: involvement of a novel phosphatase.

Prolactin (PRL) is essential for normal reproduction and signals through two types of receptors, the short (PRL-RS) and long (PRL-RL) form. We have previously shown that transgenic mice expressing only PRL-RS (PRLR(-/-)RS) display abnormal follicular development and premature ovarian failure. Here, we report that MAPK, essential for normal follicular development, is critically inhibited by PRL in reproductive tissues of PRLR(-/-)RS mice.

Prolactin signaling through the short isoform of the mouse prolactin receptor regulates DNA binding of specific transcription factors, often with opposite effects in different reproductive issues.

Background: It has been well established that prolactin (PRL) signals through the long form of its receptor (PRL-RL) and activates the Jak/Stat pathway for transcription of PRL target genes. However, signaling pathways mediated through the short PRL-R isoform (PRL-RS) remains controversial. Our recent finding that PRL signaling through PRL-RS represses two transcription factors critical for follicular development lead us to examine other putative PRL/PRL-RS target transcription factors in the decidua and ovary, two well-known target tissues of PRL action in reproduction.

Prolactin independent rescue of mouse corpus luteum life span: identification of prolactin and luteinizing hormone target genes.

The corpus luteum (CL) plays a central role in the maintenance of pregnancy in rodents, mainly by secreting progesterone. Female mice lacking prolactin (PRL) receptor (R) are sterile due to a failure of embryo implantation, which is a consequence of decreased luteinizing hormone (LH) receptor expression in the CL and inadequate levels of progesterone. We attempted to treat PRLR(-/-) females with human chorionic gonadotropin (hCG) and showed a de novo expression of LHR mRNA in the corpora lutea.

Regulation of transcription factors and repression of Sp1 by prolactin signaling through the short isoform of its cognate receptor.

Prolactin (PRL) affects the development and function of the reproductive system by binding to two types of receptors, which differ by the size of their intracellular domain in rodents. Whereas the signaling pathway through the long form of the receptor (PRL-RL) is well characterized, signaling through the short form (PRL-RS) remains obscure. In this investigation, we examined transcription factors regulated by PRL in the ovary and decidua of mice expressing only PRL-RS in a PRL receptor null background.

Prolactin receptor-associated protein/17beta-hydroxysteroid dehydrogenase type 7 gene (Hsd17b7) plays a crucial role in embryonic development and fetal survival.

Our laboratory has previously cloned and purified a protein named PRAP (prolactin receptor-associated protein) that was shown to be a novel 17beta-hydroxysteroid dehydrogenase (HSD) enzyme with dual activity. This enzyme, renamed HSD17B7 or PRAP/17beta-HSD7, converts estrone to estradiol and is also involved in cholesterol biosynthesis. The major site of its expression is the corpus luteum of a great number of species including rodents and humans.

Prolactin signaling through the short form of its receptor represses forkhead transcription factor FOXO3 and its target gene galt causing a severe ovarian defect.

Prolactin (PRL) is a hormone with over 300 biological activities. Although the signaling pathway downstream of the long form of its receptor (RL) has been well characterized, little is known about PRL actions upon activation of the short form (RS). Here, we show that mice expressing only RS exhibit an ovarian phenotype of accelerated follicular recruitment followed by massive follicular death leading to premature ovarian failure.

Involvement of cyclin D3, CDKN1A (p21), and BIRC5 (Survivin) in interleukin 11 stimulation of decidualization in mice.

Interleukin 11 receptor alpha (Il11ra) null mice are infertile due to defective decidualization and abnormal trophoblast invasion. We have previously shown in these mice that downregulation of decidual proteinase inhibitors plays a role in uncontrolled trophoblast invasion. However, the decidua is abnormally smaller in pseudopregnant Il11ra null mice, where trophoblast invasion is not a factor.

Decidual prolactin silences the expression of genes detrimental to pregnancy.

Although the main role of prolactin (PRL) in pregnant rodents is to sustain progesterone production by the corpus luteum, progesterone treatment of PRL or PRL receptor (PRL-R) null mice is unable to prevent fetal loss. We have previously shown that the rat decidua is a site of PRL production and action. In this report, we examined the hypothesis, using PRL null mice and rat decidual cell culture, that the absence of this hormone leads to the expression in the decidua of genes detrimental to pregnancy.

The molecular control of corpus luteum formation, function, and regression.

The corpus luteum (CL) is one of the few endocrine glands that forms from the remains of another organ and whose function and survival are limited in scope and time. The CL is the site of rapid remodeling, growth, differentiation, and death of cells originating from granulosa, theca, capillaries, and fibroblasts. The apparent raison d'etre of the CL is the production of progesterone, and all the structural and functional features of this gland are geared toward this end.

The role of interleukin-11 in pregnancy involves up-regulation of alpha2-macroglobulin gene through janus kinase 2-signal transducer and activator of transcription 3 pathway in the decidua.

IL-11 expressed by endometrial stromal cells is crucial for normal pregnancy. IL-11 receptor alpha (IL-11Ralpha) null mice are infertile due to abnormal development of the placenta. In these mice, the mesometrial decidual tissue, which is the site of trophoblast invasion, thins and disappears at mid-pregnancy.

Rat decidual cell cultures.

Pregnancy requires profound reorganization of the different tissues forming the uterus. Growth and differentiation of the uterine endometrial cells give rise to the decidual tissue, a transitory organ, which plays a key role in fetal survival. In this chapter, we describe a technique for the dispersion and the separation of the two different decidual cell subpopulations with high yield and viability.

Cloning and characterization of a 5' regulatory region of the prolactin receptor-associated protein/17{beta} hydroxysteroid dehydrogenase 7 gene.

Prolactin receptor-associated protein (PRAP) originally cloned in our laboratory was shown to be a novel, luteal isoform of 17beta hydroxysteroid dehydrogenase 7 (17betaHSD7). In this study, we cloned the promoter region of rat PRAP/17betaHSD7 and investigated the mechanisms regulating both basal activity and LH-induced repression of this promoter. Truncated and site-specific mutants of PRAP/17betaHSD7 promoter identified two enhancer regions that contained highly conserved Sp1 binding site and bound Sp1 from nuclear extracts of both corpora lutea and a rat luteal cell line.

PGF2alpha induced differential expression of genes involved in turnover of extracellular matrix in rat decidual cells.

In the rat, the decidual tissue is an important component for maternal recognition of pregnancy. Decidualization can be induced by either the implantation of the blastocyst or by artificial stimuli. The process of decidua formation or decidualization, is characterized by growth and differentiation of endometrial stromal cells.

Prostaglandin F(2alpha) (PGF(2alpha)) and prolactin signaling: PGF(2alpha)-mediated inhibition of prolactin receptor expression in the Corpus luteum.

It is well established that prolactin (PRL) sustains, whereas prostaglandin F(2alpha) (PGF(2alpha)) curtails, progesterone production by the rodent corpus luteum (CL). We have previously shown that PGF(2alpha) inhibits the expression of several luteal genes stimulated by PRL, whereas it stimulates other genes inhibited by this hormone. We have also found that PGF(2alpha) stimulation of 20alpha-hydroxysteroid dehydrogenase (20alphaHSD), an enzyme that catabolizes progesterone, at the end of pregnancy is accompanied by a dramatic decrease in PRL receptor (PRL-R) expression.

The involvement of apoptotic regulators during in vitro decidualization.

Objectives: The uterus responds to an implanting blastocyst by undergoing extensive tIssue modification leading to decidualization. This modification includes differentiation and apoptosis of epithelial as well as stromal cell compartments. It is generally accepted that the decidual cell regression pattern is similar to the pattern of initial differentiation, suggesting that decidual cell death is the end point of timed differentiation.

Prolactin regulation of estrogen receptor expression.

The ability of the rat corpus luteum to respond to estrogen requires prolactin (PRL), which can stimulate the expression of the estrogen receptor (ER). This review will focus on the signaling mechanisms by which this occurs. Transcription of the genes encoding both ERalpha (Esr1) and ERbeta (Esr2) is stimulated by PRL through the Jak2-Stat5 pathway and Stat5-response elements that are located in each of the Esr promoters.

The cyclin-dependent kinase inhibitors p27Kip1 and p21Cip1 cooperate to restrict proliferative life span in differentiating ovarian cells.

The timing of cellular exit from the cell cycle during differentiation is specific for each cell type or lineage. Granulosa cells in the ovary establish quiescence within several hours after the ovulation-inducing luteinizing hormone surge, whereas they undergo differentiation into corpora lutea. The expression of Cdk inhibitors p21(Cip1/Waf1) and p27(Kip1) is up-regulated during this process, suggesting that these cell cycle inhibitors are involved in restricting proliferative capacity of differentiating granulosa cells.

In vivo hormonal environment leads to differential susceptibility of the corpus luteum to apoptosis in vitro.

We evaluated the involvement of the in vivo hormonal environment on the ability of the rat corpus luteum (CL) to undergo apoptosis. Gel electrophoretic DNA fragmentation analysis revealed no apoptosis in CL isolated either the 2 last days of pregnancy (Days 21 and 22) or throughout the 4 days following parturition, suggesting that the number of cells undergoing apoptosis at the same time is not sufficient to allow for visualization of DNA breakdown. In contrast, CL incubated in serum-free medium underwent significant apoptosis, as evaluated by chromatin condensation and DNA fragmentation, regardless of their developmental stage in pregnancy.

Decidual activin: its role in the apoptotic process and its regulation by prolactin.

Successful pregnancy requires profound differentiation and reorganization of the uterine tissues including, as pregnancy progresses, extensive apoptosis of decidual tissue to accommodate the developing conceptus. We have previously shown a positive correlation between expression of activin A and apoptosis in the decidua and have also shown that expression of activin A occurs at the time when prolactin (PRL) receptors disappear from decidual cells. The goals of this study were to examine whether activin A plays a role in decidual apoptosis and whether expression of activin A in the decidua is regulated by PRL and placental lactogens.

Progesterone promotes survival of the rat corpus luteum in the absence of cognate receptors.

Progesterone production by the corpus luteum (CL) is essential for preparation of the endometrium for implantation and for the maintenance of gestation. Progesterone modulates its own production and opposes functional luteal regression induced by exogenous agents, such as prostaglandin F(2alpha). In the present study, we evaluated whether progesterone is also capable of interfering with the process of structural luteal regression, which is characterized by a decrease in weight and size of the gland because of programmed cell death (i.

Pituitary hypoplasia and lactotroph dysfunction in mice deficient for cyclin-dependent kinase-4.

The lactotroph undergoes dynamic regulation of cell cycle progression during pregnancy, as well as throughout the development of the pituitary. We recently reported that female mice with targeted disruption of Cdk4, one of the G(1)-regulatory cyclin-dependent kinases, are unable to support embryo implantation because of defective progesterone secretion from the corpus luteum. In this study, we demonstrate that this phenotype is not attributable to a primary defect in the corpus luteum but is a consequence of defective prolactin (PRL) production caused by inappropriate development of the pituitary lactotroph population.

Androstenedione interferes in luteal regression by inhibiting apoptosis and stimulating progesterone production.

Androgens, in concert with lactogenic hormones, contribute to the maintenance of function of the corpus luteum (CL) in pregnant rats. Whereas some of the androgenic actions in the CL are clearly mediated by intracrine conversion to estrogen, pure androgenic effects are also implicated in the regulation of this transient endocrine gland. In this report, we have established, to our knowledge for the first time, the expression of androgen receptor (AR) mRNA and protein throughout gestation in the rat CL.