Analysis of spatial and temporal expression patterns of bone morphogenetic protein family members in the rat uterus over the estrous cycle

Roles of bone morphogenetic proteins in endometrial remodeling during the human menstrual cycle and pregnancy

BACKGROUND

During the human menstrual cycle and pregnancy, the endometrium undergoes a series of dynamic remodeling processes to adapt to physiological changes. Insufficient endometrial remodeling, characterized by inadequate endometrial proliferation, decidualization and spiral artery remodeling, is associated with infertility, endometriosis, dysfunctional uterine bleeding, and pregnancy-related complications such as preeclampsia and miscarriage. Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor-β (TGF-β) superfamily, are multifunctional cytokines that regulate diverse cellular activities, such as differentiation, proliferation, apoptosis, and extracellular matrix synthesis, are now understood as integral to multiple reproductive processes in women. Investigations using human biological samples have shown that BMPs are essential for regulating human endometrial remodeling processes, including endometrial proliferation and decidualization.

OBJECTIVE AND RATIONALE

This review summarizes our current knowledge on the known pathophysiological roles of BMPs and their underlying molecular mechanisms in regulating human endometrial proliferation and decidualization, with the goal of promoting the development of innovative strategies for diagnosing, treating and preventing infertility and adverse pregnancy complications associated with dysregulated human endometrial remodeling.

SEARCH METHODS

A literature search for original articles published up to June 2023 was conducted in the PubMed, MEDLINE, and Google Scholar databases, identifying studies on the roles of BMPs in endometrial remodeling during the human menstrual cycle and pregnancy. Articles identified were restricted to English language full-text papers.

OUTCOMES

BMP ligands and receptors and their transduction molecules are expressed in the endometrium and at the maternal-fetal interface. Along with emerging technologies such as tissue microarrays, 3D organoid cultures and advanced single-cell transcriptomics, and given the clinical availability of recombinant human proteins and ongoing pharmaceutical development, it is now clear that BMPs exert multiple roles in regulating human endometrial remodeling and that these biomolecules (and their receptors) can be targeted for diagnostic and therapeutic purposes. Moreover, dysregulation of these ligands, their receptors, or signaling determinants can impact endometrial remodeling, contributing to infertility or pregnancy-related complications (e.g. preeclampsia and miscarriage).

WIDER IMPLICATIONS

Although further clinical trials are needed, recent advancements in the development of recombinant BMP ligands, synthetic BMP inhibitors, receptor antagonists, BMP ligand sequestration tools, and gene therapies have underscored the BMPs as candidate diagnostic biomarkers and positioned the BMP signaling pathway as a promising therapeutic target for addressing infertility and pregnancy complications related to dysregulated human endometrial remodeling.

Bone morphogenetic protein signaling is a possible therapeutic target in gynecologic cancer

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor β (TGFβ) superfamily. BMPs play crucial roles in embryogenesis and bone remodeling. Recently, BMP signaling has been found to have diverse effects on different types of tumors. In this review, we summarized the effects of BMP signaling on gynecologic cancer. BMP signaling has tumor-promoting effects on ovarian cancer (OC) and endometrial cancer (EC), whereas it has tumor-suppressing effects on uterine cervical cancer (UCC). Interestingly, EC has frequent gain-of-function mutations in ACVR1, encoding one of the type I BMP receptors, which are also observed in fibrodysplasia ossificans progressiva and diffuse intrinsic pontine glioma. Little is known about the relationship between BMP signaling and other gynecologic cancers. Tumor-promoting effects of BMP signaling in OC and EC are dependent on the promotion of cancer stemness and epithelial-mesenchymal transition (EMT). In accordance, BMP receptor kinase inhibitors suppress the cell growth and migration of OC and EC. Since both cancer stemness and EMT are associated with chemoresistance, BMP signaling activation might also be an important mechanism by which OC and EC patients acquire chemoresistance. Therefore, BMP inhibitors are promising for OC and EC patients even if they become resistant to standard chemotherapy. In contrast, BMP signaling inhibits UCC growth in vitro. However, the in vivo effects of BMP signaling have not been elucidated in UCC. In conclusion, BMP signaling has a variety of functions, depending on the types of gynecologic cancer. Therefore, targeting BMP signaling should improve the treatment of patients with gynecologic cancer.

BMP7 Functions to Regulate Proliferation of Dermal Papilla Cells in Hu Sheep

Bone morphogenetic proteins (BMPs) are the structurally similar and highly conserved type of functional proteins that play an important role in hair follicle growth and development. BMP7 was a differentially expressed gene in different patterns of Hu sheep lambskin identified using Agilent microarray. Since hair follicle is the basis of pattern formation of lambskin, and its growth and development is governed by dermal papilla cells (DPCs), to clarify the role of BMP7 and hair follicle, our study was designed to investigate the regulation between BMP7 and DPCs. Firstly, the CDS region of BMP7 was cloned by 3'Race and PCR in Hu sheep and performed serious of bioinformatic analysis. Then, the effects of BMP7 on DPCs were analyzed after overexpression and interference of BMP7 in dermal papilla cells by CCK8, EdU, and PI assay. Additionally, qPCR was also conducted to clarify the relationship between BMP7 and the TGF-β/Smad signaling pathway. A total of 1,296 bp of the BMP7 CDS region sequence was sucessfully cloned in Hu sheep, encoding a signal peptide of 431 amino acids, molecular weight was 49,316.9Da and the isoelectric point (Pi) was 7.75. Nucleotide sequencing analysis of BMP7 revealed that Hu sheep had high homology with Bos taurus, Homo sapiens, and Canis lupus familiaris. Structure domain prediction showed that TGF-β superfamily domain exist between 330th-431th amino acid, BMP7 protein is a secreted protein. In BMP7 up-regulated DPCs, DPCs proliferation rate and cell cycle were significantly higher than that of NC group (P < 0.05). Meanwhile, the expression level of Smad3, Smad4, Samd6, and TGF-β1 in TGF-β/Smad signaling pathway were significantly lower than that in NC group (P < 0.05). In BMP7 down-regulated DPCs, it presented the opposite result. In conclusion, our study showed that BMP7 had a positive effect on DPCs by accelerating the proliferation and cell cycle of DPCs, and hypothesized that regulate hair follicles growth and development via TGF-β/Smad signaling pathway. These findings may provide a synergistic target for the subsequent research of hair follicle growth and development.

The regulation of IGFBP3 by BMP2 has a role in human endometrial remodeling

In mammals, bone morphogenetic protein 2 (BMP2) is a critical regulator of endometrial decidualization and early implantation. Insulin-like growth factor-binding protein 3 (IGFBP3) is highly expressed in the endometrium and at the maternal-fetal interface in multiple species, including humans. BMP2-induced IGFBP3 signaling has been confirmed to have a role in trophoblast cell invasion; however, the involvement of this signaling pathway in endometrial remodeling remains poorly understood. To determine the roles of BMP2 in regulating IGFBP3 expression during the transformation of endometrial stromal cells, we employed immortalized human endometrial stromal cells (HESCs) and primary human decidual stromal cells (HDSCs) as study models. We showed that BMP2 significantly increased the expression of IGFBP3 in a dose- and time-dependent manner in both HESCs and primary HDSCs. Additionally, the BMP2-induced upregulation of IGFBP3 is mediated by the inhibitor of DNA-binding 1 (ID1), and knockdown of ALK3 completely abolished BMP2-induced upregulation of ID1. Moreover, BMP2 increased the expression of matrix metalloproteinases 2 (MMP2) and promoted cell migration in HESCs and primary HDSCs. Knockdown of either IGFBP3 or ID1 significantly suppressed the basal and the BMP2-induced increase in MMP2 expression as well as the cell migration in both cell models. These data demonstrated that BMP2 upregulated the expression of ID1, which in turn induced the expression of IGFBP3, and these BMP2-induced cell activities were most likely mediated by the ALK3 type I receptor. The increased expression of IGFBP3 promoted the MMP2 expression and cell migration in both HESCs and HDSCs. These findings deepen our understanding of a newly identified mechanism by which BMP2 and IGFBP3 regulate endometrial remodeling in humans, which provides insight into potential therapies for endometrium-related diseases and pregnancy-induced complications.

Epithelium morphogenesis and oviduct development are regulated by significant increase of expression of genes after long-term in vitro primary culture – a microarray assays

The correct oviductal development and morphogenesis of its epithelium are crucial factors influencing female fertility. Oviduct is involved in maintaining an optimal environment for gametes and preimplantation embryo development; secretory oviductal epithelial cells (OECs) synthesize components of oviductal fluid. Oviductal epithelium also participates in sperm binding and its hyperactivation. For better understanding of the genetic bases that underlay porcine oviductal development, OECs were isolated from porcine oviducts and established long-term primary culture. A microarray approach was utilized to determine the differentially expressed genes during specific time periods. Cells were harvested on day 7, 15 and 30 of in vitro primary culture and their RNA was isolated. Gene expression was analyzed and statistical analysis was performed. 48 differentially expressed genes belonging to “tube morphogenesis”, “tube development”, “morphogenesis of an epithelium”, “morphogenesis of branching structure” and “morphogenesis of branching epithelium” GO BP terms were selected, of which 10 most upregulated include BMP4, ARG1, SLIT2, FGFR1, DAB2, TNC, EPAS1, HHEX, ITGB3 and LOX. The results help to shed light on the porcine oviductal development and its epithelial morphogenesis, and show that after long-term culture the OECs still proliferate and maintain their tube forming properties.

The characterization and potential roles of bone morphogenetic protein 7 during spermatogenesis in Chinese mitten crab Eriocheir sinensis

Bone morphogenetic proteins (BMPs), which belong to the transforming growth factor-β superfamily, have been implicated in various biological and physiological processes, especially in the gonad development. However, scarce studies were focused on the roles of BMPs in the reproductive system of crustaceans. In this study, the whole gene encoding BMP7 protein was cloned and characterized firstly in Chinese mitten crab Eriocheir sinensis. The bioinformatics analysis of the deduced amino acid sequence showed that Es-BMP7 was composed of prodomain/latency-associated peptide and the TGF-β characteristic domain. The sequence conservation and phylogenetic analysis were also conducted. Quantitative real-time PCR was conducted indifferent tissues. The highest expression in testis indicated the potential role of BMP7 to male gonad development. Western blot results showed the different translational levels of BMP7 in different tissues. In-situ hybridization revealed that the expression of es-bmp7 signals presented in a bimodal manner: highest in spermatogonia, decreased in spermatocytes and stage I spermatids, disappeared in stage II spermatids, and showed up again in stage III spermatids and mature sperm. To further verify the potential roles during spermatogenesis, immunofluorescence was conducted and results showed the similar expression tendency with in situ hybridization. The protein signal was highest in the cytoplasm of spermatogonia, continued to decline in the cytoplasm of spermatocytes and the following stages, and weak signal was found in the mature sperm. Taken together, our results revealed that Es-BMP7 might play a part in testis development in Eriocheir sinensis, presumably by maintaining the self-renewal of spermatogonia and promoting the germ cell differentiation/meiotic mitosis, or facilitating the successful fertilization.

Uterine ALK3 is essential during the window of implantation

The window of implantation is defined by the inhibition of uterine epithelial proliferation, structural epithelial cell remodeling, and attenuated estrogen (E2) response. These changes occur via paracrine signaling between the uterine epithelium and stroma. Because implantation defects are a major cause of infertility in women, identifying these signaling pathways will improve infertility interventions. Bone morphogenetic proteins (BMPs) are TGF-β family members that regulate the postimplantation and midgestation stages of pregnancy. In this study, we discovered that signaling via activin-like kinase 3 (ALK3/BMPR1A), a BMP type 1 receptor, is necessary for blastocyst attachment. Conditional knockout (cKO) of ALK3 in the uterus was obtained by producing Alk3(flox) (/flox)-Pgr-cre-positive females. Alk3 cKO mice are sterile and have defects in the luminal uterine epithelium, including increased microvilli density and maintenance of apical cell polarity. Moreover, Alk3 cKO mice exhibit an elevated uterine E2 response and unopposed epithelial cell proliferation during the window of implantation. We determined that dual transcriptional regulation of Kruppel-like factor 15 (Klf15), by both the transforming growth factor β (TGF-β) transcription factor SMAD family member 4 (SMAD4) and progesterone receptor (PR), is necessary to inhibit uterine epithelial cell proliferation, a key step for embryo implantation. Our findings present a convergence of BMP and steroid hormone signaling pathways in the regulation of uterine receptivity.

Bone Morphogenetic Protein-6 (BMP-6) Stimulates the Antrum Formation by the Regulation of its Signalling Pathway in Caprine Pre-antral Follicles Cultured In Vitro

BMP-6 has been found to be important to ovarian cells and oocyte, as well as to uterus. Thus, this study investigated the effect of bone morphogenetic protein (BMP-6) and recombinant follicle-stimulating hormone (rFSH) alone or in combination on the in vitro culture (IVC) of isolated caprine secondary follicles (Experiment 1) and the mRNA levels for BMP receptors/Smad signalling pathway (BMPR1A, BMPR2, SMAD1, SMAD4, SMAD5, SMAD6, SMAD7 and SMAD8) in vivo and in vitro using BMP-6 (Experiment 2). Secondary follicles were cultured in αMEM(+) alone (control medium) or supplemented with BMP-6 at 1 or 10 ng/ml and rFSH alone or the combination of both BMP-6 concentrations and rFSH. The results from Experiment 1 showed that the antrum formation rate was higher in the BMP-6 at 1 ng/ml (p < 0.05) than in MEM. In Experiment 2, the mRNA expression for BMPR2, SMAD1, SMAD5 and SMAD6 was detected in non-cultured control and after in vitro culture (MEM and 1 ng/ml BMP-6); while the expression of SMAD7 and SMAD8 mRNA was only detected after IVC, SMAD4 was only detected in the BMP-6 at 1 ng/ml treatment. In conclusion, the low BMP-6 concentration positively influenced antrum formation and ensured normal mRNA expression for BMP receptor and Smads after IVC of caprine secondary follicles.

Expression of bone morphogenetic protein 2, 4, and related components of the BMP signaling pathway in the mouse uterus during the estrous cycle

The objective was to investigate the expression of bone morphogenetic protein (BMP) family members in the mouse uterus during the estrous cycle by real-time polymerase chain reaction (PCR) and immunohistochemistry. Uterine samples from Swiss ICR mice were collected and dissected free of surrounding tissue. One uterine horn was snap frozen in liquid nitrogen immediately after collection and stored at -80 °C for RNA extraction, and the other was fixed in 40 mg/ml paraformaldehyde at room temperature for immunolocalization of BMP2 protein. Real-time PCR analysis showed that the expression level of Bmp2 was significantly higher at proestrus than at estrus and metestrus (P<0.05). The relative abundance of Bmp4 exhibited significant fluctuations, but there were no statistically significant differences between the expression levels of Bmp2 and Bmp4 (P>0.05). The expression levels of Bmpr1a and Bmpr2 remained unchanged during estrous cycles. However, the level of Bmpr1b mRNA decreased significantly at estrus (P<0.05), increasing subsequently at metestrus. Furthermore, the level of Bmpr1b mRNA was significantly lower than those of Bmpr1a and Bmpr2 mRNA at the corresponding stages (P<0.05). All three receptor-regulated Smads (R-Smads) detected were differentially expressed in the mouse uterus and the expression levels of Smad1 and Smad5 were significantly higher than that of Smad8 (P<0.05). In addition, the expression level of Smad4 did not change substantially throughout the estrous cycle. Immunohistochemical experiments revealed that BMP2 protein was differentially expressed and localized mainly in the uterine luminal and glandular epithelial cells throughout the estrous cycle. In conclusion, our results provide information about the variation in the mRNA levels of Bmp2 and Bmp4 and related components of the BMP signaling pathway. The data provide quantitative and useful information about the roles of endometrial BMP proposed and demonstrated by others, such as the degradation and remodeling of the endometrium.

Inhibitory role of REV-ERBα in the expression of bone morphogenetic protein gene family in rat uterus endometrium stromal cells

Uterus circadian rhythms have been implicated in the gestation processes of mammals through entraining of the clock proteins to numerous downstream genes. Bone morphogenetic proteins (BMPs), having clock-controlled regulatory sites in their gene promoters, are expressed in the uterus during decidualization, but the regulation of the Bmp gene expression is poorly understood. The present study was designed to dissect the physiological roles of the uterus oscillators in the Bmp expression using the uterus endometrial stromal cells (UESCs) isolated from Per2-dLuc transgenic rats on day 4.5 of gestation. The in vitro decidualization of UESCs was induced by medroxyprogesterone acetate and 2-O-dibutyryl cAMP. A significant decline of Per2-dLuc bioluminescence activity was induced in decidual cells, and concomitantly, the expression of canonical clock genes was downregulated. Conversely, the expression of the core Bmp genes Bmp2, Bmp4, Bmp6, and Bmp7 was upregulated. In UESCs transfected with Bmal1-specific siRNA, in which Rev-erbα expression was downregulated, Bmp genes, such as Bmp2, Bmp4, and Bmp6 were upregulated. However, Bmp1, Bmp7, and Bmp8a were not significantly affected by Bmal1 silencing. The expression of all Bmp genes was enhanced after treatment with the REV-ERBα antagonist (SR8278), although their rhythmic profiles were differed from each other. The binding of REV-ERBα to the proximal regions of the Bmp2 and Bmp4 promoters was revealed by chromatin immunoprecipitation-PCR analysis. Collectively, these results indicate that the Bmp genes are upregulated by the attenuation of the cellular circadian clock; in particular, its core component REV-ERBα functions as a transcriptional silencer in the Bmp gene family.

Expression of repulsive guidance molecule b (RGMb) in the uterus and ovary during the estrous cycle in rats

Repulsive guidance molecule b (RGMb; a.k.a. Dragon), initially identified in the embryonic dorsal root ganglion, is the first member of the RGM family shown to enhance bone morphogenetic protein (BMP) signaling by acting as a BMP co-receptor. BMP signaling has been demonstrated to play an important role in the reproductive organs. Our previous study found that RGMb was expressed in the reproductive axis, but whether RGMb expression in reproductive organs changes across the estrous cycle remains unknown. Here, we show in the rat that RGMb mRNA expression in the uterus was significantly higher during metesterus and diestrus than during proestrus and estrus. Western blotting indicated that RGMb protein was significantly lower during estrus compared with the other three stages. Immunohistochemistry revealed that RGMb protein was mainly localized to the uterine luminal and glandular epithelial cells of the endometrium. RGMb mRNA and protein in the ovary remained unchanged during the estrous cycle. RGMb protein was expressed in the oocytes of all follicles. Weak staining for RGMb protein was also found in corpora lutea. RGMb was not detected in granulosa cells and stromal cells. Taken together, RGMb expression in the uterus and ovary across the estrus cycle demonstrate that RGMb may be involved in the regulation of uterine function, follicular development as well as luteal activity.

Improvement of ovarian response and oocyte quality of aged female by administration of bone morphogenetic protein-6 in a mouse model

BACKGROUND

Advancing female age remains a difficult problem in infertility treatment. Ovarian angiogenesis plays an important role in follicular development and the activation of ovarian angiogenesis has been emerged as a new strategy for the improvement of age-related decline of oocyte quality. BMP-6 affect gonadotropin signals in granulosa cells and it promotes normal fertility by enabling appropriate response to LH and normal oocyte quality. BMP-6 has a potential role in regulation of angiogenesis and regulates the expression of inhibitor of DNA-binding proteins (Ids). Ids involved in the control and timing of follicle selection and granulosa cells differentiation. Especially, Id-1 is well-characterized target of BMP-6 signaling. Therefore, this study investigated whether co-administration of BMP-6 during superovulation process improves ovarian response, oocyte quality and expression of Id-1 and vascular endothelial growth factor (VEGF) in the ovary of aged female using a mouse model.

METHODS

Aged C57BL/6 female mice (26-31 weeks old) were superovulated by injection with 0.1 mL of 5 IU equine chorionic gonadotropin (eCG) containing recombinant mouse BMP-6 at various doses (0, 0.01, 0.1, 1, and 10 ng), followed by injection with 5 IU human chorionic gonadotropin (hCG) 48 h later. Then, the mice were immediately paired with an individual male. The aged control group was superovulated without BMP-6. Young mice of 6-9 weeks old were superovulated without BMP-6 as a positive control for superovulation and in vitro culture of embryos. Eighteen hours after hCG injection, zygotes were retrieved and cultured for 4 days. Both ovaries of each mouse were provided in the examination of ovarian expression of Id-1 and VEGF by reverse transcriptase-polymerase chain reaction, western blot, and immunohistochemistry.

RESULTS

Administration of 0.1 ng BMP-6 significantly increased the number and blastocyst formation rate of oocytes ovulated and ovarian expression of Id-1 and VEGF compared to aged control mice. These increased levels were comparable to those of young control mice.

CONCLUSIONS

This result suggests that BMP-6 during ovulation induction plays an important role in improvement of oocyte quality and ovarian response of aged female, possibly by regulating of ovarian Id-1 and VEGF expression.

Ovarian adipocytokines are associated with early in vitro human embryo development independent of the action of ovarian insulin

PURPOSE

We aimed to characterize the association between levels of serum and follicular fluid (FF) adipocytokines, reflected by the leptin to adiponectin ratio (L:A ratio), and oocyte quality and in vitro embryo development in women undergoing assisted reproduction. We also aimed to assess whether follicular hormonal pathways mediate this interaction.

METHODS

We prospectively collected FF from up to four individual preovulatory follicles (n = 76) and fasting sera from women (n = 31) without endocrinopathies undergoing in vitro fertilization (IVF) at a university-based center for assisted reproduction. Leptin, total adiponectin, insulin, insulin-like growth factor 1 (IGF-1), and ovarian steriods were measured using enzyme immunoassay. Oocyte maturity, fertilization, and embryo development were assessed.

RESULTS

FF leptin was similar to serum levels while FF adiponectin was lower. FF leptin (27.10 ± 4.05 ng/mL) and the L:A ratio (11.48E-3 ± 2.57E-3) were related to FF insulin (R (2) = 0.370 and 0.419, p < 0.001) but not to ovarian steroids or IGF-1, whereas FF adiponectin ( 4.22 ± 0.52 ug/mL) correlated only with leptin (R (2) = -0.138, p = 0.001). Oocytes from a high FF L:A ratio environment were 81 % (RR 1.81 [95%CI 0.97-3.37]) more likely to undergo successful cleavage and 117 % (RR 2.17 [95 % CI 1.06-4.44]) more likely to obtain viable cleavage morphology compared to a low FF L:A ratio environment, even when adjusted for FF insulin, an independent predictor of cleavage.

CONCLUSIONS

Certain adipocytokines, particularly the L:A ratio in the FF of the preovulatory follicle, are related to successful in vitro embryo development. This action may be independent of FF insulin.

Immunohistochemical analysis of bone morphological protein signaling pathway in human myometrium

We assessed by immunohistochemistry the expression of the phosphorylated (activated) form of Smad1 and 5 (P-SMAD1/5), of Noggin and of two smooth muscle cell markers (α-SMA and SM22) in a series of human myometrium samples and in a smooth muscle cell line derived from human myometrium (HUt-SMC, PromoCell, USA). Myometrium samples were removed from two cadavers (a fetus at 26 weeks of gestation and a neonate) and from ten non-menopausal women who underwent hysterectomy for adenomyosis and leiomyoma. P-SMAD1/5 expression was never detected in myometrium (both normal and pathological specimens), but only as a nuclear positive staining in glandular and luminal epithelial cells in sections in which also the endometrial mucosa was present. Noggin was strongly expressed especially in myometrium and adenomyosis samples from non-menopausal patients in comparison to the neonatal and fetal myometrium specimens in which muscle cells were less positive. In more than 95% of HUt-SMCs, α-SMA and Desmin were co-expressed, indicating a pure smooth muscle phenotype. When progesterone was added to the culture medium, no P-SMAD1/5 expression was detected, whereas the expression Noggin and SM22, a marker of differentiated smooth muscle cells, increased by 3 fold (p=0.002) and 4.3 fold (p=0.001), respectively (p=0.002). Our results suggest that, in non-menopausal normal human myometrium, the BMP pathway might be inhibited and that this inhibition might be enhanced by progesterone, which increases the differentiation of smooth muscle cells (SM22 levels). These findings could help in the identification of new mechanisms that regulate uterine motility.

Co-expression of bone morphogenetic protein 6 with estrogen receptor a in endometriosis

BACKGROUND

Bone morphogenetic protein 6 (BMP-6) has decisive role in controlling multiple organogenetic processes, as well as modulating cell differentiation and proliferation. Considering those pleiotropic effects, we focused on determining expression of that multifunctional growth factor in ectopic endometriotic tissues.

MATERIALS AND METHODS

In this prospective study, 85 consecutive women with endometriosis were included. All patients underwent gynecological operations due to endometriosis associated problems and tissue specimens were collected from ectopic endometriotic lesions. Immunohistochemical staining of paraffin sections for both BMP-6 and estrogen receptors a (ERa) was performed in all 85 cases using an avidin-biotin-peroxidase procedure.

RESULTS

Ectopic endometrium showed intense cytoplastic immunoreactivity to BMP-6 in both epithelium and stroma. In addition, we have demonstrated that BMP-6 expression is highly associated with strong expression of ERa.

DISCUSSION

The availability of BMP-6 in the ectopic endometrium may be at least partly involved in the mechanisms of attachment, survival and expansion of endometriosis. Moreover, the statistically significant correlation in expression of BMP-6 and ERa demonstrated in this study may be associated with the development of rich in estrogen microenvironment, but requires further investigation. In conclusion, this is the first study in our knowledge demonstrating strong expression of BMP-6 in endometriosis.

Dynamic expression of bone morphogenetic protein 4 in reproductive organs of female mice

Various members of the bone morphogenetic protein (BMP) family have been shown to regulate mammalian follicular development by affecting granulosa cell proliferation and steroidogenesis. In situ hybridization studies have shown expression of BMPR1A, BMPR1B, and BMPR2 in the granulosa cells and oocyte of most of the follicles in the ovary, suggesting that these cells have the capacity to respond to BMP signaling. Although much is known about BMP4 signaling, its expression pattern in the female reproductive tract (FRT) is still unclear. The objective of the current study was to characterize the expression of BMP4 and its downstream target proteins (pSMAD1/5/8) in the FRT. In the ovary, BMP4 protein was detected in all the stages of follicular development. Staining for pSMAD1/5/8 was observed in granulosa cells and oocytes of all the stages of follicular development including primordial follicles, suggesting that these follicles are responsive to autocrine/paracrine BMP signaling. In the uterus, BMP4 and pSMAD1/5/8 staining was observed in all three compartments and strongest expression was observed during the estrus phase. BMP4- and pSMAD1/5/8-specific staining was also observed in oviductal epithelium. Different forms (apparent MW: 50, 35, and 15  kDa) of BMP4 were detected in mouse ovary by western blot analysis. In conclusion, these results have defined BMP4 and pSMAD1/5/8 protein expression in the mouse FRT and highlighted the importance of BMP4 in folliculogenesis.

Influence of anabolic combinations of an androgen plus an estrogen on biochemical pathways in bovine uterine endometrium and ovary

The application of anabolic steroids in food producing animals is forbidden in the EU since 1988, but the abuse of such drugs is a potential problem. The existing test systems are based on known compounds and can be eluded by newly emerging substances. The examination of physiological effects of anabolic hormones on different tissues to indirectly detect misuse might overcome this problem. Two studies were conducted with post-pubertal 24-months old Nguni heifers and pre-pubertal female 2-4 weeks old Holstein Friesian calves, respectively. The animals of the accordant treatment groups were administered combinations of estrogenic and androgenic compounds. The measurement of the gene expression pattern was undertaken with RT-qPCR. Target genes of different functional groups (receptors, angiogenesis, steroid synthesis, proliferation, apoptosis, nutrient metabolism and others) have been quantified. Several biochemical pathways were shown to be influenced by anabolic treatment. Both studies identified significant regulations in steroid and growth factor receptors (AR, ERβ, LHR, FSHR, Flt-1, PR, IGF-1R, Alk-6), angiogenic and tissue remodeling factors (VEGFs, FGFs, BMPs, ANGPT-2, MMPs, TIMP-2, CTSB), steroid synthesis (S5A1, HSD17, CYP19A1), proliferation (TNFα, IGF-1, IGFBPs, p53, c-fos; CEBPD, c-kit), apoptosis (CASP3, FasL, p53) and others (C7, INHA, STAR). Several genes were regulated to opposite directions in post-pubertal compared to pre-pubertal animals. PCA for Nguni heifers demonstrated a distinct separation between the control and the treatment group. In conclusion, anabolics modify hormone sensitivity and steroid synthesis, and they induce proliferative effects in the whole reproductive tract (uterus and ovary) as well as anti-angiogenic effects in the ovary. However, the extent will depend on the developmental stage of the animals.

Granulosa cell-expressed BMPR1A and BMPR1B have unique functions in regulating fertility but act redundantly to suppress ovarian tumor development

Bone morphogenetic proteins (BMPs) have diverse roles in development and reproduction. Although several BMPs are produced by oocytes, thecal cells, and granulosa cells of developing follicles, the in vivo functions of most of these ligands are unknown. BMP signals are transduced by multiple type I and type II TGFbeta family receptors, and of the type I receptors, BMP receptor 1A (BMPR1A) and BMP receptor 1B (BMPR1B) are known to be expressed in rodent granulosa cells. Female mice homozygous null for Bmpr1b are sterile due to compromised cumulus expansion, but the function of BMPR1A in the ovary is unknown. To further decipher a role for BMP signaling in mouse granulosa cells, we deleted Bmpr1a in the granulosa cells of the ovary and found Bmpr1a conditional knockout females to be subfertile with reduced spontaneous ovulation. To explore the redundant functions of BMP receptor signaling in the ovary, we generated Bmpr1a Bmpr1b double-mutant mice, which developed granulosa cell tumors that have evidence of increased TGFbeta and hedgehog signaling. Thus, similar to SMAD1 and SMAD5, which have redundant roles in suppressing granulosa cell tumor development in mice, two type I BMP receptors, BMPR1A and BMPR1B, function together to prevent ovarian tumorigenesis. These studies support a role for a functional BMP signaling axis as a tumor suppressor pathway in the ovary, with BMPR1A and BMPR1B acting downstream of BMP ligands and upstream of BMP receptor SMADs.

Transforming growth factor beta isoforms regulation of Akt activity and XIAP levels in rat endometrium during estrous cycle, in a model of pseudopregnancy and in cultured decidual cells

BACKGROUND

During the estrous cycle, the rat uterine endometrium undergoes many changes such as cell proliferation and apoptosis. If implantation occurs, stromal cells differentiate into decidual cells and near the end of pregnancy, a second wave of apoptosis occurs. This process called decidual regression, is tightly regulated as is it crucial for successful pregnancy. We have previously shown that TGF-beta1, TGF-beta2 and TGF-beta3 are expressed in the endometrium during decidual basalis regression, but although we had demonstrated that TGF- beta1 was involved in the regulation of apoptosis in decidual cells, the ability of TGF- beta2 and TGF-beta3 isoforms to trigger apoptotic mechanisms in these cells remains unknown. Moreover, we hypothesized that the TGF-betas were also present and regulated in the non-pregnant endometrium during the estrous cycle. The aim of the present study was to determine and compare the specific effect of each TGF-beta isoform in the regulation of apoptosis in sensitized endometrial stromal cells in vitro, and to investigate the regulation of TGF-beta isoforms in the endometrium during the estrous cycle in vivo.

METHODS

Rats with regular estrous cycle (4 days) were killed at different days of estrous cycle (diestrus, proestrus, estrus and metestrus). Pseudopregnancy was induced with sex steroids in ovariectomized rats and rats were killed at different days (days 1-9). Uteri were collected and either fixed for immunohistochemical staining (IHC) or processed for RT-PCR and Western analyses. For the in vitro part of the study, rats were ovariectomized and decidualization was induced using sex steroids. Endometrial stromal decidual cells were purified, cultured and treated with different concentrations of TGF-beta isoforms.

RESULTS

Our results showed that all three TGF-beta isoforms are present, but are localized differently in the endometrium during the estrous cycle and their expression is regulated differently during pseudopregnancy. In cultured stromal cells, we found that TGF-beta3 isoform induced Smad2 phosphorylation, indicating that the Smad pathway is activated by TGF-beta3 in these cells. Furthermore, TGF-beta2 and TGF-beta3 induced a dose-dependant increase of apoptosis in cultured stromal cells, as demonstrated by Hoechst nuclear staining. Noteworthy, TGF-beta2 and TGF-beta3 reduced the level of the anti-apoptotic XIAP protein, as well as the level of phosphorylated/active Akt, a well known survival protein, in a dose-dependent manner.

CONCLUSION

Those results suggest that TGF-beta might play an important role in the remodelling endometrium during the estrous cycle and in the regulation of apoptosis in rat decidual cells, in which inhibition of Akt survival pathway might be an important mechanism involved in the regulation of apoptosis.

[Cloning and bioinformatic analysis of bone morphological protein 7 (BMP7) in rabbit]

On the basis of known partial coding DNA sequence (GenBank accession No. AF413111), we tried to clone the full mRNA of rabbit BMP7 gene by sub-cloning and RACE methods. Then after, bioinformatic analysis on the acquired sequences were conducted. The sequencing results showed that the all cloned sequences could be assembled into a 1 654 bp long DNA fragment, which contained the near full coding cDNA for the propetide, full coding cDNA for the mature protein, and full length of 3'UTR of rabbit BMP7. The newly cloned sequences extended the 5'and 3'ends of known partial DNA sequence by 395 bp and 628 bp, respectively. Sequence comparisons revealed that the full length of coding cDNA of rabbit BMP7 was 91.89% and 89.32% identical to that of human and mouse, while the deduced amino acids was 96.51% and 96.01% identical, respectively. The 3'UTR of rabbit BMP7 was 446 bp in length, 57.38% and 45.57% identical to that of human or mouse, respectively. In addition, there were two closely arranged AATAAA sites in the 3'UTR of rabbit BMP7 gene, as well as in human BMP7. The deduced mature protein of rabbit BMP7 had the seven conservative cysteines and a TGF-b family signature, which were the characters of all BMPs. Our results suggested that the main part of rabbit BMP7 had been successively cloned. The alternation of polyadenization sites in the 3'UTR of rabbit BMP7 maybe related to the posttranscriptional regulation of the gene.

A distinct cohort of the TGFbeta superfamily members expressed in human endometrium regulate decidualization

BACKGROUND

Successful blastocyst implantation requires the differentiation of human endometrial stromal cells (HESC), a process known as decidualization. Activin A, a transforming growth factor beta (TGFbeta) superfamily member, enhances HESC decidualization and localizes to decidual cells in human endometrium. Other TGFbeta superfamily members, including BMP2, BMP4, BMP7, GDF5, GDF8, GDF11, TGFbetas and Nodal, may also play a role during decidualization. This study aimed to identify these TGFbeta family members in human endometrium, and to determine whether they are involved in human decidualization.

METHODS

Protein localization of TGFbeta family members was examined in secretory phase human endometrium and first trimester decidua by immunohistochemistry. mRNA expression was examined in HESC. Activin inhibitors (Activin-M108A/SB431542) with differing specificities for the other TGFbeta members under consideration were applied during HESC decidualization in vitro. The secretion levels of potential TGFbeta superfamily members were measured during decidualization, and recombinant proteins added to examine their effect.

RESULTS

This study has identified BMP2, BMP4, BMP7, GDF5, GDF8 and GDF11 but not Nodal in secretory phase human endometrium, but only BMP2, GDF5 and TGFbeta1 protein were detected in decidual cells. All ligands except Nodal were expressed by cultured HESC. Both inhibitors significantly reduced decidualization validating the role of activin, but potentially also other TGFbeta members, during decidualization. BMP2 and TGFbeta1 secretion increased during HESC decidualisation and exogenous administration of these proteins significantly enhanced decidualization in vitro.

CONCLUSIONS

Like activin, BMP2 and TGFbeta1 are likely to be involved in HESC decidualization. This is the first study to identify and localize BMP4, BMP7, GDF5, GDF8 and GDF11 in secretory phase human endometrium. Understanding the factors critical for the implantation process is needed for improving fertility and pregnancy outcomes.

Bmp2 is critical for the murine uterine decidual response

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. Bmp2 gene ablation was confirmed by real-time PCR analysis in the PR-cre; Bmp2fl/fl (termed Bmp2d/d) uterus. While littermate controls average 0.9 litter of 6.2+/-0.7 pups per month, Bmp2d/d females are completely infertile. Analysis of the infertility indicates that whereas embryo attachment is normal in the Bmp2d/d as in control mice, the uterine stroma is incapable of undergoing the decidual reaction to support further embryonic development. Recombinant human BMP2 can partially rescue the decidual response, suggesting that the observed phenotypes are not due to a developmental consequence of Bmp2 ablation. Microarray analysis demonstrates that ablation of Bmp2 leads to specific gene changes, including disruption of the Wnt signaling pathway, Progesterone receptor (PR) signaling, and the induction of prostaglandin synthase 2 (Ptgs2). Taken together, these data demonstrate that Bmp2 is a critical regulator of gene expression and function in the murine uterus.

Expression of bone morphogenetic protein 2 in normal spontaneous labor at term, preterm labor, and preterm premature rupture of membranes

OBJECTIVE

Genome-wide screening studies of the chorioamniotic membranes unexpectedly identified an increase in the expression of bone morphogenetic protein 2 in spontaneous labor at term. The objective of this study was to determine whether bone morphogenetic protein 2 messenger RNA and protein expression are altered in the chorioamniotic membranes of patients with term labor, preterm labor, and preterm premature rupture of membranes.

STUDY DESIGN

Chorioamniotic membranes were obtained from patients at term (with and without labor), with preterm labor (with and without histologic chorioamnionitis), and with preterm premature rupture of membranes (with and without histologic chorioamnionitis). The expression of bone morphogenetic protein 2 was studied by real-time quantitative reverse transcriptase-polymerase chain reaction (n = 88) and immunohistochemistry (n = 124). Nonparametric statistics were used for analysis. Primary amnion cells obtained from women at term not in labor were treated with bone morphogenetic protein 2 to examine whether there was increased prostaglandin E2 expression.

RESULTS

The median bone morphogenetic protein 2 messenger RNA and protein expression were significantly higher in the membranes of patients with spontaneous labor at term than in those of patients not in labor at term (P < .001 for both). Bone morphogenetic protein 2 messenger RNA and protein expression were increased in patients with preterm labor with histologic chorioamnionitis than in those without histologic chorioamnionitis (P < .05 and P < .001, respectively). There was no difference in bone morphogenetic protein 2 messenger RNA and protein expression in patients with preterm premature rupture of membranes, regardless of chorioamnionitis (P = .13 and P = .08, respectively). There was a correlation between bone morphogenetic protein 2 and cyclooxygenase 2 protein expression in chorioamniotic membranes (R = .34; P < .001).

CONCLUSION

Bone morphogenetic protein 2 messenger RNA and protein expression are increased in the chorioamniotic membranes of patients with spontaneous labor at term and patients with preterm labor associated with histologic chorioamnionitis. Its expression pattern and biologic effects strongly suggest that bone morphogenetic protein 2 is involved in human parturition.

Tissue, cell and stage specificity of (epi)mutations in cancers

Most (epi)mutations in cancers are specific to particular tumours or occur at specific stages of development, cell differentiation or tumorigenesis. Simple molecular mechanisms, such as tissue-restricted gene expression, seem to explain these associations only in rare cases. Instead, the specificity of (epi)mutations is probably due to the selection of a restricted spectrum of genetic changes by the cellular environment. In some cases, the resulting functional defects might be constrained to be neither too strong nor too weak for tumour growth to occur; that is, they lie within a 'window' that is permissive for tumorigenesis.

Localization and action of Dragon (repulsive guidance molecule b), a novel bone morphogenetic protein coreceptor, throughout the reproductive axis

Bone morphogenetic proteins (BMPs) play important roles in reproduction including primordial germ cell formation, follicular development, spermatogenesis, and FSH secretion. Dragon, a recently identified glycosylphosphatidylinositol-anchored member of the repulsive guidance molecule family, is also a BMP coreceptor. In the present study, we determined the tissue and cellular localization of Dragon in reproductive organs using immunohistochemistry and in situ hybridization. Among reproductive organs, Dragon was expressed in testis, epididymis, ovary, uterus, and pituitary. In the testis of early postnatal mice, Dragon was found in gonocytes and spermatogonia, whereas in immature testes, Dragon was only weakly expressed in spermatogonia. Interestingly, pregnant mare serum gonadotropin treatment of immature mice robustly induced Dragon production in spermatocytes. In adult testis, Dragon was found in spermatocytes and round spermatids. In the ovary, Dragon was detected exclusively within oocytes and primarily those within secondary follicles. In the pituitary, Dragon-expressing cells overlapped FSH-expressing cells. Dragon was also expressed in a number of cell lines originating from reproductive tissues including Ishikawa, Hela, LbetaT2, MCF-7, and JEG3 cells. Immunocytochemistry and gradient sucrose ultracentrifugation studies showed Dragon was localized in lipid rafts within the plasma membrane. In reproductive cell lines, Dragon expression enhanced signaling of exogenous BMP2 or BMP4. The present studies demonstrate that Dragon expression is dynamically regulated throughout the reproductive tract and that Dragon protein modulates BMP signaling in cells from reproductive tissues. The overlap between Dragon expression and the functional BMP signaling system suggests that Dragon may play a role in mammalian reproduction.

Apoptosis in the ovary: molecular mechanisms

Cell death was first described in rabbit ovaries (Graaffian follicles), the phenomenon being called 'chromatolysis' rather than apoptosis. In humans, the ovarian endowment of primordial follicles is established during fetal life. Apoptotic cell death depletes this endowment by at least two-thirds before birth, executed with the help of several players and pathways conserved from worms to humans. To date, apoptosis has been reported to be involved in oogenesis, folliculogenesis, oocyte loss/selection and atresia. Several pro-survival and pro-apoptotic molecules are involved in ovarian apoptosis with the delicate balance between them being the determinant for the final destiny of the follicular cells. This review critically analyses the current knowledge about the biological roles of these molecules and their relevance to the dynamics of follicle development. It also presents the existing literature and assesses the gaps in our knowledge.