Marker genes of decidualization: activation of the decidual prolactin gene

Abstract

Decidualization of human endometrial stromal (ES) cells in vitro is induced by cAMP analogues and ligands that elevate cellular cAMP levels in a manner resembling the gonadotrophins, prostaglandin E2 and relaxin (RLX). This differentiation process is marked by the onset of decidual prolactin (PRL) production in the late luteal phase of the cycle. Using transfection assays and a primary ES cell culture system, we have demonstrated that decidual PRL gene transcription is driven by an alternative upstream promoter (dPRL), approximately 6 kb upstream of the pituitary transcription start site. In primary cell cultures, RLX not only acutely but also permanently elevated cellular cAMP levels and induced PRL secretion after 6 days. Northern and Western blot analyses revealed all regulatory subunit isoforms (RIalpha, RIbeta, RIIalpha, RIIbeta) and catalytic subunits Calpha and Cbeta of protein kinase A (PKA) in ES cells. Transcript levels of PKA subunit isoforms are not altered during decidualization, but in decidualized ES cells exposed to elevated cellular cAMP levels by stimulation with RLX for >6 days, RIalpha protein levels were significantly reduced, whereas levels of all other forms remained unchanged. Reducing the availability of R subunits changed the R:C subunit ratio in favour of C and increased kinase activity. In transient transfections of undifferentiated ES cells, the dPRL promoter was activated by 8-Br-cAMP and by C subunit (Cbeta) of PKA. This induction, and the differentiation-dependent activity of the dPRL promoter in transfected decidualized cells, was effectively abolished by the co-expression of protein kinase inhibitor (PKI). A fragment of 332 bp of 5'-flanking region of the dPRL transcription start site was sufficient to mediate full inducibility by cAMP. cAMP activation of the dPRL promoter in ES cells was biphasic as an initial weak induction within 12 hours was followed by a subsequent, much more intense induction after 12 hours. The secondary induction was not seen with a control construct driven by a consensus cAMP response element (CRE) linked to a minimal promoter. The early response of the dPRL promoter depended upon a non-palindromic CRE at position -12 and mutation of this sequence led to omission of the early, but not of the delayed, induction. The major activation of the dPRL promoter depended upon a different region between position -332 and -270 since its deletion significantly reduced inducibility by cAMP. Its action was probably indirect as its kinetics differed from classic CRE-mediated responses, and it was specific to ES cells.

Involvement of Stathmin in Proliferation and Differentiation of Immortalized Human Endometrial Stromal Cells

“…We then showed that suppression of stathmin Thus, our study supports previous observations suggesting that stathmin may be involved in the proliferation and/ or differentiation of primary endometrial cells in humans [16]. Ovarian steroids induce endometrial stromal cell differentiation by activating the cAMP pathways and stromal cells that are freshly isolated from normal endometrial tissues decidualize when treated with either progesterone plus estradiol or db-cAMP [15]. In fact, several endometrial cell lines respond to steroid treatment [20]; however, the EtsT cell line does not decidualize upon treatment with progesterone plus estradiol (data not shown).…”

“…These types of studies have shown that when uterine endometrial stromal cells transform into decidualized stromal cells, they are altered morphologically and begin to secrete specific decidual proteins [14]. In vitro studies have also shown that stromal cell preparations decidualize when exposed to ovarian steroids (progesterone and estradiol) or agents that activate the cAMP pathway [15]. In our previous report, we also used primary endometrial stromal cell cultures to explore the role of stathmin in decidualization.…”

Expression of the Metastasis Suppressor KAI1 in Decidual Cells at the Human Maternal-Fetal Interface

“…A persistent elevation of intracellular cAMP in stromal cells is essential for acquisition and maintenance of the decidual phenotype. 1,43 In the late secretory phase of the menstrual cycle, endometrial stromal cells are exposed to a variety of local and endocrine factors that bind to G-protein coupled receptors and stimulate the production of cAMP, including prostaglandin E 2 , relaxin, corticotropin-releasing hormone, and the gonadotropins luteinizing hormone and follicle stimulating hormone. 1 In pregnancy, the decidua is exposed to vast amounts of human chorionic gonadotropin (hCG) secreted by the syncytiotrophoblast, and signaling through the luteinizing hormone/hCG receptor involves cAMP as a second messenger.…”

Potential roles of decidual prolactin in early pregnancy

“…(Data derived from Wang et al, 1998. ) cAMP−protein kinase A signalling pathway (reviewed in Telgmann and Gellersen, 1998). cAMP alone can induce prolactin production in endometrial monolayers and this effect is synergistically enhanced by medroxyprogesterone acetate (Brosens et al, 1999).…”