Expression of stathmin in human uterus and decidualizing endometrial stromal cells

Exchange protein directly activated by cAMP (EPAC) promotes transcriptional activation of the decidual prolactin gene via CCAAT/enhancer-binding protein in human endometrial stromal cells

Protein kinase A (PKA) signalling accompanies elevated intracellular cAMP levels during endometrial stromal cell (ESC) decidualisation. Exchange protein directly activated by cAMP (EPAC), an alternate mediator of cAMP signalling, promotes PKA analogue-induced decidualisation; however, the precise mechanism by which EPAC and PKA co-operatively stimulate decidualisation has not been characterised. To examine the role of CCAAT/enhancer-binding protein (C/EBP) in EPAC- and PKA-mediated decidualisation of primary human ESCs, a reporter plasmid containing the 332bp region upstream from the transcription initiation site of the decidual prolactin (dPRL) gene was generated and the promoter activity was evaluated using a luciferase assay. The dPRL promoter activity was increased by treatment of transfected ESCs with the PKA-selective cAMP analogue N6-phenyl-cAMP (Phe) and enhanced further by co-treatment with the EPAC-selective cAMP analogue 8-(4-chlorophenyltio)-2'-O-methyl cAMP (CPT). Treatment with forskolin, an adenylyl cyclase activator, had a similar effect on reporter activity. Site-directed mutagenesis of the C/EBPβ- and/or C/EBPδ-binding site in the dPRL promoter abolished Phe/CPT-mediated elevation of the reporter activity. EPAC2 knockdown markedly reduced Phe-stimulated C/EBPβ and C/EBPδ mRNA levels, as well as forkhead box O1 (FOXO1) protein levels. These results suggest that EPAC signalling enhances PKA-mediated dPRL expression in ESCs by acting on C/EBP response elements in the promoter region of the gene.

Distinct changes in the proteome profile of endometrial tissues in polycystic ovary syndrome compared with healthy fertile women

RESEARCH QUESTION

What is the molecular basis of infertility related to uterine dysfunction in women with polycystic ovary syndrome (PCOS)?

DESIGN

In this study, differences in protein expression between PCOS and normal endometrium were identified using a proteomic approach based on two-dimensional electrophoresis (2-DE) coupled with mass spectrometry (MS). The proteome of endometrium were analysed during the proliferative (on day 2 or 3 before ovulation, n = 6) and luteal phases (on day 3-5 after ovulation, n = 6) from healthy women and PCOS patients (12-14 days after spontaneous bleeding, n = 12). The differentially expressed proteins were categorized based on the biological process using the DAVID bioinformatics resources.

RESULTS

Over 803 reproducible protein spots were detected on gels, and 150 protein spots showed different intensities between PCOS and normal women during the proliferative and luteal phases. MS analysis detected 70 proteins out of 150 spots. For four of the 70 proteins, 14-3-3 protein, annexin A5, SERPINA1 and cathepsin D, 2-DE results were validated and localized by Western blot and immunohistochemistry, respectively, and their gene expression profiles were confirmed by real-time quantitative PCR. The obtained results corresponded to the proteomic analysis. The differentially expressed proteins identified are known to be involved in apoptosis, oxidative stress, inflammation and the cytoskeleton.

CONCLUSIONS

The processes related to the differentially expressed proteins play important roles in fecundity and fecundability. The present study may reveal the cause of various endometrial aberrations as a limiting factor for achieving pregnancy in PCOS women.

Stathmin 1 plays a role in endometrial decidualisation by regulating hypoxia inducible factor-1α and vascular endothelial growth factor during embryo implantation

The aim of the present study was to explore the potential mechanism underlying stathmin 1 (Stmn1) regulation of embryo implantation, as a continuation of previous proteomic research. Adult healthy female mice were mated naturally with fertile males. Murine uterine tissue was collected during the peri-implantation period. Local expression of Stmn1 during embryo implantation was detected by immunohistochemistry (IHC), which showed that Stmn1 was extensively expressed in endometrial glandular epithelium, vascular endothelium, luminal epithelium and the underlying stromal cells at the implantation site on Day 5. The role of Stmn1 during embryo implantation was evaluated by transient knockdown of Stmn1 in vivo using short interference (si) RNA, and some associated factors including Akt, phosphorylated (p-) Akt, hypoxia-inducible factor (HIF)-1α, prolactin (PRL), insulin-like growth factor binding protein (IGFBP) 1 and vascular endothelial growth factor (VEGF) were examined by western blotting analysis and ELISA. The number of embryos implanted after Stmn1-siRNA infusion into the lumen of one uterine horn was lower than that with normal pregnancies (2.2 ± 1.5 vs 8.6 ± 0.5 respectively; P < 0.05). The expression of VEGF, HIF-1α, p-Akt and the decidualisation biomarkers PRL and IGFBP 1 was upregulated at the implantation site on Day 5, but downregulated after Stmn1-siRNA infusion. These findings suggest that during embryo implantation, knockdown of Stmn1 suppresses decidualisation by inhibiting the expression of p-Akt, HIF-1α and VEGF, thus leading to impaired embryo implantation. These findings provide clues for understanding the complicated process of embryo implantation and the potential role of Stmn1 during embryo implantation.

Placental development in a mouse model of spinal muscular atrophy

Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder, leading to fatal loss of motor neurons. It is caused by loss of function of the SMN gene, which is expressed throughout the body, and there is increasing evidence of dysfunction in non-neuronal tissues. Birthweight is one of most powerful prognostic factors for infants born with SMA, and intrauterine growth restriction is common. In the SMNΔ7 mouse model of SMA, pups with the disease lived 25% longer when their mothers were fed a higher fat, "breeder" diet. The placenta is responsible for transport of nutrients from mother to fetus, and is a major determinant of fetal growth. Thus, the present study tested the hypothesis that placental development is impaired in SMNΔ7 conceptuses. Detailed morphological characterization revealed no defects in SMNΔ7 placental development, and expression of key transcription factors regulating mouse placental development was unaffected. The intrauterine growth restriction observed in SMA infants likely does not result from impaired placental development.

A mass spectrometric insight into the origins of benign gynecological disorders

Applications of mass spectrometry (MS) are rapidly expanding and encompass molecular and cellular biology. MS aids in the analysis of in vivo global molecular alterations, identifying potential biomarkers which may improve diagnosis and treatment of various pathologies. MS has added new dimensionality to medical research. Pioneering gynecologists now study molecular mechanisms underlying female reproductive pathology with MS-based tools. Although benign gynecologic disorders including endometriosis, adenomyosis, leiomyoma, and polycystic ovarian syndrome (PCOS) carry low mortality rates, they cause significant physical, mental, and social detriments. Additionally, some benign disorders are unfortunately associated with malignancies. MS-based technology can detect malignant changes in formerly benign proteomes and metabolomes with distinct advantages of speed, sensitivity, and specificity. We present the use of MS in proteomics and metabolomics, and summarize the current understanding of the molecular pathways concerning female reproductive anatomy. Highlight discoveries of novel protein and metabolite biomarkers via MS-based technology, we underscore the clinical application of these techniques in the diagnosis and management of benign gynecological disorders. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:450-470, 2017.

Decreased stathmin-1 expression inhibits trophoblast proliferation and invasion and is associated with recurrent miscarriage

Fetal trophoblasts invade endometrium and establish a complex interaction with the maternal microenvironment during early pregnancy. However, the molecular mechanisms regulating trophoblast migration and invasion at the maternal-fetal interface remain poorly understood. Immunohistochemistry and immunoblotting have shown that stathmin-1 (STMN1) was down-regulated significantly in placental villi tissue and trophoblasts from patients with recurrent miscarriage. In vitro, overexpression of STMN1 promoted human trophoblast proliferation, migration, and invasion, whereas knockdown of STMN1 inhibited these processes. In addition, knockdown of STMN1 down-regulated N-cadherin and up-regulated E-cadherin in trophoblasts, whereas E-cadherin was up-regulated and N-cadherin was down-regulated in recurrent miscarriage villi tissue. Knockdown of STMN1 attenuated cytoplasmic-nuclear translocation of β-catenin and in turn down-regulated trophoblast matrix metalloproteases. Furthermore, tumor necrosis factor-α (TNF-α) down-regulated STMN1 expression, and serum TNF-α expression correlated inversely with trophoblast STMN1 levels. Interestingly, M1 macrophage-derived TNF-α reduced trophoblast migration and invasion, and an anti-TNF-α antibody reversed this effect. Collectively, this study indicated that STMN1 may play a key role in regulating trophoblast invasion, and that impaired STMN1 expression may lead to abnormal trophoblast invasion and result in recurrent miscarriage.

Identification of stathmin 1 during peri-implantation period in mouse endometrium by a proteomics-based analysis

In this work we aimed to identify the differentially expressed proteins and their potential roles during peri-implantation period through proteomics-based approach. Adult healthy female mice were mated naturally with fertile males to produce pregnancy. The models of pseudopregnancy, delayed implantation, and artificial decidualization were established. The protein profile between pre-implantation (D1) and implantation (D5) period was compared by two-dimensional electrophoresis (2-DE) and identified by mass spectrometry (MS). 2-DE yielded comparative images presenting over 500 protein spots in D1 and D5 mouse endometrium. 15 proteins were identified, of which stathmin 1, Apo-A1, hnRNP H3, transgelin 2 and arginase 1 were validated by western blotting. Stathmin 1 expression did not change in pseudopregnancy, but activation of implantation, or induction of decidualization increased it dramatically. Under non-pregnant status, progesterone alone or in combination with17β-estradiol increased it dramatically. Our results clarified the protein profile in mouse endometrium during implantation. The specific expression profile of stathmin 1 suggested that it should be involved in implantation and serve as a potential regulator of this process. These findings may contribute to the better understanding of the molecules events during embryo implantation, and subsequently improve the ability to treat infertility.

Possible Role of α1-Antitrypsin in Endometriosis-Like Grafts From a Mouse Model of Endometriosis

Previous study indicated that bleeding into the peritoneum may accelerate inflammatory response in endometriosis-like grafts in mice. To identify changes in protein levels in the grafts from mice that underwent unilateral ovariectomy (uOVX), which causes bleeding from ovarian arteries and vein, the grafts were generated by injecting a suspension of human endometrial cells in BALB/c nude female mice, and protein profile changes were compared with non-uOVX control mice. The level of α1-antitrypsin (α1-AT) decreased in grafts from nude mice that underwent uOVX. The levels of phosphorylated Akt, mammalian target of rapamycin, S6K, regulatory factors for cell survival, and of phosphorylated nuclear factor κB, an inflammatory mediator, were higher in endometriosis-like grafts from the uOVX group than from the control. The grafts were mostly comprised of stromal cells. The bioactivity of α1-AT was assessed by investigating cytokine expression in protease-activated receptor (PAR) 1/2 agonists-stimulated stromal cells. The PARs promoted the expression of interleukin 8 (IL-8), but treatment with α1-AT blocked IL-8 expression dose dependently. Knocking down α1-AT expression increased the constitutive IL-6, IL-8, and cyclooxygenase 2 expression as well as PAR1 agonist-stimulated IL-6 expression. These findings support the notion that decreased α1-AT protein in the grafts constituted with human endometrial cells in mice may have exacerbated inflammation in endometriosis-like grafts, suggesting the possible involvement of α1-AT in the pathophysiology of endometriosis.

The role of exchange protein directly activated by cyclic AMP 2-mediated calreticulin expression in the decidualization of human endometrial stromal cells

Decidualization of human endometrial stromal cells (ESCs) accompanied by the production of prolactin (PRL) and IGF-binding protein (IGFBP) 1 and rounded-cell morphology is indispensable for the establishment and maintenance of pregnancy. Protein kinase A (PKA)-mediated cAMP signaling is known to be crucial for decidualization. We previously reported that activation of a cAMP mediator, called Exchange protein directly activated by cAMP (EPAC) promotes cAMP analog- or ovarian steroid-induced decidualization in cultured human ESCs. In addition, small interfering RNA-mediated knock-down of the EPAC subtypes, EPAC1 or EPAC2, or knock-down of Rap1, a downstream factor of EPAC signaling, blocked functional and morphological decidualization of ESCs. However, factors downstream of EPAC2 other than Rap1 have not been determined. The present study was undertaken to identify additional downstream targets of EPAC2 associated with decidualization. Using proteomic analysis, we identified calreticulin (CRT) as a potential target of EPAC2. Knock-down of CRT expression in cultured ESCs significantly inhibited PKA-selective cAMP analog- or PKA-selective cAMP analog plus EPAC-selective cAMP analog-induced PRL and IGFBP1 expression. Furthermore, CRT knock-down suppressed the ovarian steroid-stimulated PRL and IGFBP1 expression and morphological differentiation, and silencing of EPAC2 or CRT significantly increased senescence-associated β-galactosidase activity with enhanced p21 expression and decreased p53 expression. These results suggest that EPAC2 and CRT are associated with cellular senescence in ESCs. In conclusion, we demonstrate here that EPAC2-mediated CRT expression is essential for the functional and morphological differentiation of ESCs into decidual cells. Furthermore, both EPAC2 and CRT might prevent ESCs from undergoing abnormal cellular senescence during decidualization.

Regulation of decidualization in human endometrial stromal cells through exchange protein directly activated by cyclic AMP (Epac)

INTRODUCTION

Human endometrial stromal cells (ESCs) undergo differentiation during the decidualization process. Decidualization is characterized by their enhanced production of IGF binding protein-1 (IGFBP-1), prolactin (PRL), and the forkhead transcriptional factor FOXO1, and transformation into more rounded cells, during the secretory phase of the menstrual cycle and subsequent pregnancy. Protein kinase A (PKA)-mediated cAMP signaling is crucial for this process. The present study was undertaken to examine the involvement of a mediator of cAMP signaling, exchange protein directly activated by cAMP (Epac), in decidualization of cultured ESCs.

RESULTS

Treatment of ESCs with the Epac-selective cAMP analog 8-CPT-2-OMe-cAMP (CPT) had no effect on IGFBP-1, PRL, and FOXO1 mRNA expression. However, CPT potentiated IGFBP-1 and PRL expression stimulated by the PKA-selective cAMP analog N(6)-Phe-cAMP (Phe) and activated Rap1, a downstream regulator of Epac signaling. Knock-down of Epac1, Epac2, or Rap1 significantly inhibited the Phe- or Phe/CPT-induced increase in IGFBP-1 and PRL expression, as well as Rap1 activation. Furthermore, CPT enhanced IGFBP-1 and PRL expression and the morphological differentiation induced by ovarian steroids, whereas Epac1, Epac2, or Rap1 knock-down suppressed these events.

CONCLUSION

These data provide evidence for the involvement of the Epac/Rap1 signaling pathway in cAMP-mediated decidualization of human ESCs.

Critical role of TRPC1-mediated Ca²⁺ entry in decidualization of human endometrial stromal cells

Decidualization is an ovarian steroid-induced remodeling/differentiation process of uterus essential for embryo implantation and placentation. Here, we investigated the possible involvement of enhanced Ca²⁺ dynamics in the decidualization process in human endometrial stromal cells (hESC) in its connection with a recently emerging nonvoltage-gated Ca²⁺ entry channel superfamily, the transient receptor potential (TRP) protein. Combined application of 17β-estradiol (E₂) (10 nM) and progesterone (P₄) (1 μM) for 7-14 d resulted in morphological changes of hESC characteristic of decidualization (i.e. cell size increase), whereas sole application of E₂ exerted little effects. A 7- to 14-d E₂/P₄ treatment greatly increased the expression level of decidualization markers IGF binding protein-1 (IGFBP-1) and prolactin and also up-regulated the expression of TRPC1, a canonical TRP subfamily member that has been implicated in store-operated Ca²⁺ influx (SOC) in other cell types. In parallel with this up-regulation, SOC activity in hESC, the nuclear translocation of phosphorylated cAMP responsive element binding protein (p-CREB) and the expression of Forkhead box protein 01 were enhanced significantly. Small interfering RNA knockdown of TRPC1 counteracted the E₂/P₄-induced up-regulation of IGFBP-1 and prolactin and enhancement of SOC activity together with the inhibition of hESC size increase, p-CREB nuclear translocation, and FOXO1 up-regulation. Coadministration of SOC inhibitors SK&F96365 or Gd³⁺ with E₂/P₄ also suppressed the up-regulation of IGFBP-1 and hESC size increase. Similar inhibitory effects were observed with extracellularly applied TRPC1 extracellular loop 3-directed antibody, which is known to bind a near-pore domain of TRPC1 channel and block its Ca²⁺ transporting activity. These results strongly suggest that up-regulation of TRPC1 protein and consequent enhancement of SOC-mediated Ca²⁺ influx may serve as a crucial step for the decidualization process of hESC probably via p-CREB-dependent transcriptional activity associated with FOXO1 activation.

Proteomic analysis of pregnancy-related proteins from pig uterus endometrium during pregnancy

Many important molecular events associated with implantation and development occur within the female reproductive tract, especially within the uterus endometrium, during pregnancy periods. The endometrium includes the mucosal lining of the uterus, which provides a suitable site for implantation and development of a fertilized egg and fetus. To date, the molecular cascades in the uterus endometrium during pregnancy periods in pigs have not been elucidated fully. In this study, we compared the functional regulated proteins in the endometrium during pregnancy periods with those in non-pregnant conditions and investigated changes in expression patterns during pregnancy (days 40, 70, and 93) using two-dimensional gel electrophoresis (2-DE) and western blotting. The functional regulated proteins were identified and discovered from differentially expressed proteins in the uterus endometrium during pregnancy. We discovered 820 protein spots in a proteomic analysis of uterus endometrium tissues with 2-DE gels. We identified 63 of the 98 proteins regulated differentially among non-pregnant and pregnant tissues (matched and unmatched spots). Interestingly, 10 of these 63 proteins are development-, cytoskeleton- and chaperon-related proteins such as transferrin, protein DJ-1, transgelin, galectin-1, septin 2, stathmin 1, cofilin 1, fascin 1, heat shock protein (HSP) 90β and HSP 27. The specific expression patterns of these proteins in the endometrium during pregnancy were confirmed by western blotting. Our results suggest that the expressions of these genes involved in endometrium function and endometrium development from early to late gestation are associated with the regulation of endometrium development for maintaining pregnancy.

Reduced stathmin-1 expression in natural killer cells associated with spontaneous abortion

Female CBA/J mice impregnated by male DBA/2J mice (CBA/J×DBA/2J matings) are prone to spontaneous abortion, although the reason for this is unclear. In this study, the stathmin-1 expression pattern was evaluated in uterine natural killer (uNK) cells purified from CBA/J×DBA/2J matings. Results were compared with those in a CBA/J×BALB/c control group that yields successful pregnancies. The mean ± SD percentage of stathmin-1(+) cells in the CD49b(+) uNK cell population was lower in CBA/J×DBA/2J mice (0.7% ± 0.4%) than in control CBA/J×BALB/c mice (4.9% ± 1.5%, P < 0.01) using flow cytometry, and the intracellular stathmin-1 level in uNK cells was lower in CBA/J×DBA/2J mice than in control mice using Western blot analysis. Co-localization of lectin from Dolichos biflorus agglutinin (DBA-lectin) and stathmin-1 was confirmed using multivision immunohistochemical analysis. The frequency of stathmin-1(+)DBA-lectin(+) cells was lower in CBA/J×DBA/2J mice than in CBA/J×BALB/c mice. A similar trend in the frequency of stathmin-1(+)CD56(+) cells was seen in patients with unexplained spontaneous abortion compared with normal early pregnancy. A neutralizing antibody against stathmin-1 further increased the percentage of embryo loss in CBA/J×DBA/2J matings. These results provide evidence that stathmin-1 expression in uNK cells at the maternal-fetal interface may help modulate uNK cell function and may be beneficial for a successful pregnancy.

Stathmin, a microtubule regulatory protein, is associated with hypoxia-inducible factor-1alpha levels in human endometrial and endothelial cells

Local hypoxia that occurs during menstruation triggers angiogenesis that is crucial for cyclical remodeling of the endometrium during the menstrual cycle. Hypoxia is thought to be important for the expression of vascular endothelial growth factor (VEGF) via its transcriptional factor, hypoxia inducible factor (HIF)-1alpha, in the endometrium. The activation of the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway may modulate HIF-1alpha protein levels. Stathmin, a microtubule regulatory protein, was expressed in the stroma, glandular epithelium, and vascular endothelium in human endometrium. In this study, we examined a possible role of stathmin in hypoxia-induced HIF-1alpha and VEGF expression in primary isolated and immortalized human endometrial stromal cells, glandular epithelial cells, and human umbilical venous endothelial cells (HUVEC). Knocking down stathmin expression using small interfering RNA caused microtubule stabilization and inhibited hypoxia-induced VEGF mRNA expression via the reduction of HIF-1alpha protein levels in endometrial cells and HUVEC. Treatment of the cells with a PI3K inhibitor, wortmannin, inhibited the expression of VEGF mRNA and the accumulation of HIF-1alpha protein. Silencing of stathmin expression repressed the activation (phosphorylation) of Akt in endometrial cells and HUVEC. These results suggest that endometrial stathmin is linked to HIF-1alpha protein accumulation and VEGF expression through the PI3K/Akt signaling pathway and may be involved in regeneration of the endometrium during the menstrual cycle in human uterine cells.

[Role of implantation-related factors, stathmin and insulin-like growth factor-binding protein 7 in reproductive endocrinology]

Successful implantation and placentation require that trophoblasts adhere to the uterine epithelium and penetrate the decidualized endometrium. However, the biochemical mechanisms of the establishment of pregnancy including these phenomena have not yet to be definitively elucidated. We have found that stathmin, a cytosolic phosphoprotein that regulates microtubule dynamics, and insulin-like growth factor-binding protein (IGFBP)-related protein 1 (IGFBP-rP1, now called IGF-binding protein 7) were highly expressed in the endometrium around the time of implantation and decidualization. In this article, we review our recent findings of the research regarding the functions of these implantation-associated proteins in endocrine physiology and pharmacology. Analysis of the expression of both factors in rodent and human uterus has revealed that both factors are crucial for the process of endometrial stromal cell differentiation.

Involvement of stathmin in proliferation and differentiation of immortalized human endometrial stromal cells

Uterine endometrial stromal cells differentiate into decidual cells during the late secretory phase of the menstrual cycle and pregnancy. However, the biochemical mechanisms of decidualization have yet to be definitively elucidated. In the present study, we transfected primary human endometrial stromal cell with a temperature-sensitive mutant of simian virus 40 large T antigen and thereby established an immortalized stromal cell line (EtsT) in order to examine the role of stathmin, a cytosolic phosphoprotein that regulates microtubule dynamics, in stromal cell differentiation. When treated with the decidual stimulus dibutyryl-cAMP (db-cAMP) or forskolin, the fibroblastic cell-shaped EtsT cells transformed into large- and round-shaped cells and secreted large amounts of the decidual markers prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1). Analysis of the stathmin protein levels in the db-cAMP- and forskolin-treated EtsT cells revealed that the total and phosphorylated protein levels dropped as decidualization progressed. Suppression of stathmin expression by transfection with small interfering RNA (siRNA) suppressed EtsT cell proliferation. It also abolished db-cAMP-induced PRL and IGFBP-1 mRNA expression and protein secretion. Thus, stathmin expression can be considered an integral factor regulating the initial stage of the process of human endometrial stromal cell differentiation.