BACKGROUND: Each month the endometrium becomes inflamed, and the luminal portion is shed during menstruation. The subsequent repair is remarkable, allowing implantation to occur if fertilization takes place. Aberrations in menstrual physiology can lead to common gynaecological conditions, such as heavy or prolonged bleeding. Increased knowledge of the processes involved in menstrual physiology may also have translational benefits at other tissue sites. METHODS: Pubmed and Cochrane databases were searched for all original and review articles published in English until April 2015. Search terms included 'endometrium', 'menstruation', 'endometrial repair', 'endometrial regeneration' 'angiogenesis', 'inflammation' and 'heavy menstrual bleeding' or 'menorrhagia'. RESULTS: Menstruation occurs naturally in very few species. Human menstruation is thought to occur as a consequence of preimplantation decidualization, conferring embryo selectivity and the ability to adapt to optimize function. We highlight how current and future study of endometrial inflammation, vascular changes and repair/regeneration will allow us to identify new therapeutic targets for common gynaecological disorders. In addition, we describe how increased knowledge of this endometrial physiology will have many translational applications at other tissue sites. We highlight the clinical applications of what we know, the key questions that remain and the scientific and medical possibilities for the future. CONCLUSIONS: The study of menstruation, in both normal and abnormal scenarios, is essential for the production of novel, acceptable medical treatments for common gynaecological complaints. Furthermore, collaboration and communication with specialists in other fields could significantly advance the therapeutic potential of this dynamic tissue.
Expression and function of the follicle-stimulating hormone receptor (FSHR) in females were long thought to be limited to the ovary. Here, however, we identify extragonadal FSHR in both the human female reproductive tract and the placenta, and test its physiological relevance in mice. We show that in nonpregnant women FSHR is present on: endothelial cells of blood vessels in the endometrium, myometrium, and cervix; endometrial glands of the proliferative and secretory endometrium; cervical glands and the cervical stroma; and (at low levels) stromal cells and muscle fibers of the myometrium. In pregnant women, placental FSHR was detected as early as 8-10 wk of gestation and continued through term. It was expressed on: endothelial cells in fetal portions of the placenta and the umbilical cord; epithelial cells of the amnion; decidualized cells surrounding the maternal arteries in the maternal decidua; and the stromal cells and muscle fibers of the myometrium, with particularly strong expression at term. These findings suggest that FSHR expression is upregulated during decidualization and upregulated in myometrium as a function of pregnancy. The presence of FSHR in the placental vasculature suggests a role in placental angiogenesis. Analysis of genetically modified mice in which Fshr is lacking in fetal portions of the placenta revealed adverse effects on fetoplacental development. Our data further demonstrate FSHB and CGA mRNAs in placenta and uterus, consistent with potential local sources of FSH. Collectively, our data suggest heretofore unappreciated roles of extragonadal FSHR in female reproductive physiology.
The marked cyclical physiological angiogenesis in the developing follicle, corpus luteum and endometrium implies a critical role in health and disease. Our approach to understanding its regulation has been to localise and quantify the temporal changes in putative angiogenic factors, and their receptors, in human and non-human primate tissue and to use antagonists to dissect their role by specific inhibition at defined periods during the ovulatory cycle in non-human primates in vivo . The course of angiogenesis throughout the cycle and the cellular and molecular effects of inhibitory treatments have been investigated in the marmoset ovary and uterus, whereas consequences on pituitary–ovarian function have been monitored in macaques. Inhibition of vascular endothelial growth factor (VEGF) at the time of follicle recruitment or selection prevents endothelial cell proliferation, leading to inhibition of follicular development. VEGF inhibition during the early luteal phase prevents angiogenesis and restricts development of the luteal microvasculature. Inhibition of angiogenesis at all stages of the cycle leads to profound suppression of ovarian function. Even during the ‘post-angiogenic’ period of the luteal phase, inhibition of VEGF precipitates a suppression of progesterone secretion, pointing to additional roles for VEGF in the ovary. In the endometrium, oestrogen drives endometrial angiogenesis through VEGF. Thus, oestrogen can restore angiogenesis after ovariectomy, but not in the presence of VEGF inhibitors. These investigations enhance our understanding of the regulation of angiogenesis in the ovary and uterus and inform studies on conditions with abnormal vascularisation, such as polycystic ovary syndrome, endometriosis, uterine fibroids and menstrual dysfunction.
Objective To compare the expression of hypoxia inducible factor 1α (HIF1α) and micro–blood vessels in endometrium around the time of embryo implantation in women with recurrent miscarriage and fertile controls. Design Retrospective study. Setting University hospitals. Patient(s) Sixty women: 24 with recurrent miscarriage and 36 with proven fertility. Intervention(s) Endometrial biopsy samples obtained precisely 7 days after luteinization hormone (LH) surge in a natural cycle. Main Outcome Measure(s) Immunohistochemical analysis to determine expression of HIF1α and micro–blood vessels as identified by von Willebrand factor (vWF) in endometrium; semiquantitative analysis using H -score analysis of staining intensity for HIF1α in the luminal epithelium, glandular epithelium, and stroma, separately; number, diameter, and volume of vWF-positive endometrial micro-vessels as counted by Image J software. Result(s) The luminal epithelial and stromal expression of HIF1α in women with recurrent miscarriage was higher than found in the fertile controls, with the change in the luminal epithelium reaching the highest statistical significance. There was no statistically significant difference in HIF1α expression in glandular epithelium between the two groups. An increased number as well as volume of micro–blood vessels was observed in women with recurrent miscarriage although the mean diameter of the micro–blood vessels did not statistically significantly differ between the two groups. Conclusion(s) We have found an aberrant expression of HIF1α and micro–vessel number and volume in the peri-implantation endometrium of women with recurrent miscarriage, suggesting that altered hypoxia and vascularization status may account for the endometrial contribution to recurrent miscarriage.
Abstract The eutopic endometrium in women suffering from endometriosis is different in many ways from that of healthy controls. Both proliferative and secretory eutopic endometria exhibit changes in endometriosis with heterogeneous responses. In addition, nerve fibres appear in the endometrium and myometrium of these women. The endometrium is a rich source of pro-angiogenic factors and vascular events are often disrupted in endometriosis with an overall increase in angiogenesis. A number of investigations have shown that endometriosis is likely the most common cause of endometrial receptivity defects. Endometriosis is also associated with relative 17β-hydroxysteroid dehydrogenase type II deficiency and these molecular aberrations indicate that local oestrogen production sustains ectopic implants. Recently it has been shown that endometriosis, as a chronic inflammatory disorder, disrupts co-ordinated progesterone response throughout the reproductive tract, including the endometrium, leading to a condition of ‘progesterone resistance’. Investigators have searched for biomarkers of endometriosis, but these investigations are fraught with methodological difficulties. In conclusion, molecular phenotyping of the endometrium is changing the disease paradigm, from being foremost an oestrogen-dependent disease to a disorder characterized primarily by progesterone resistance. In recent years, research on the pathogenesis of endometriosis has been focused on alterations in the uterus and particularly the eutopic endometrium. The eutopic endometrium in women suffering from endometriosis is different in many ways from that of healthy controls. Both proliferative and secretory eutopic endometria exhibit changes in endometriosis with heterogeneous responses. The endometrium is a rich source of pro-angiogenic factors and vascular events are often disrupted in endometriosis with an overall increase in angiogenesis. A number of investigations have shown that endometriosis is likely the most common cause of endometrial receptivity defects. Recently, it has been shown that endometriosis, as a chronic inflammatory disorder, disrupts co-ordinated progesterone response throughout the reproductive tract, including the endometrium, leading to a condition of ‘progesterone resistance’. Investigators have searched for biomarkers of endometriosis, but these investigations are fraught with methodological difficulties. In conclusion, molecular phenotyping of the endometrium is changing the disease paradigm; from being foremost an oestrogen-dependent disease to a disorder characterized primarily by progesterone resistance.
Abstract STUDY QUESTION Do platelets play any role in the development of adenomyosis? SUMMARY ANSWER As in endometriosis, adenomyotic lesions show significantly increased platelet aggregation, increased expression of transforming growth factor (TGF)-β1, phosphorylated Smad3, markers of epithelial-mesenchymal transition (EMT) and fibroblast-to-myofibroblast transdifferentiation (FMT), and smooth muscle metaplasia (SMM), in conjunction with increased fibrosis as compared with normal endometrium. WHAT IS KNOWN ALREADY Both EMT and FMT are known to play vital roles in fibrogenesis in general and in endometriosis in particular. EMT has been implicated in the development of adenomyosis. SMM is universally seen in endometriosis and also in adenomyosis, and is correlated positively with the extent of fibrosis. However, there has been no published study on the role of platelets in fibrogenesis in adenomyosis, even though adenomyotic lesions undergo repeated cycles of tissue injury and repair, which suggests the involvement of platelets and their possible roles in fibrogenesis. STUDY DESIGN, SIZE, DURATION Cross-sectional studies of ectopic endometrial and control endometrial tissue samples from three sets of women with and without adenomyosis (n= 34 and 20, 12 and 10, and 8 and 8, respectively) were carried out from 2014 to 2015. PARTICIPANTS/MATERIALS, SETTING, METHODS Immunohistochemistry analysis of ectopic endometrial tissues from women with (n= 34) and without (n= 20) adenomyosis with respect to biomarkers of EMT, FMT and highly differentiated smooth muscle cells as well as TGF-β1, phosphorylated Smad3, markers of proliferation, angiogenesis and extracellular matrix (ECM) deposits. Masson trichrome staining, Van Gieson staining and Pico-Sirius staining were performed to evaluate and quantify the extent of fibrosis in lesions. Progesterone receptor isoform B (PR-B) staining also was performed. In addition, CD42b-positive platelets in ectopic (n= 12) and control (n= 10) endometrium were counted by confocal microscopy and compared. The protein expression levels of TGF-β1 and phosphorylated Smad3 in both ectopic (n= 8) and control (n= 8) endometrium were measured by western blot analysis. Immunofluorescent staining of both platelets and hepatocyte growth factor (HGF) was also performed for adenomyotic tissue samples (n= 10). MAIN RESULTS AND THE ROLE OF CHANCE Adenomyotic lesions had a significantly higher extent of platelet aggregation and increased staining for TGF-β1 and phosphorylated Smad3 (both P-values <0.001 versus control). In addition, E-cadherin staining was decreased while vimentin staining in adenomyotic epithelial cells was increased, along with increased staining of proliferating cell nuclear antigen, vascular endothelial growth factor and CD31 (all P-values <0.001), markers of proliferation and angiogenesis. Staining for α-SMA, a marker for myofibroblast, desmin, smooth muscle myosin heavy chain and oxytocin receptor was significantly increased in adenomyotic lesions versus control, concomitant with increased staining of collagen I and lysyl oxidase (all P-values <0.001). Histochemistry analysis indicates that the extent of fibrosis is high in adenomyotic lesions (P < 0.001), and the extent appeared to correlate negatively with the microvessel density (P < 0.05). PR-B staining was significantly decreased in adenomyotic lesion as compared with control endometrium (P < 0.001). Platelets and HGF were co-localized mostly in the stromal component of adenomyotic lesions, near the glandular epithelium. LIMITATIONS, REASONS FOR CAUTION The results are limited by the cross-sectional nature of the study and the use of histochemistry and immunohistochemistry analyses only, but nonetheless is a validation of our previous finding in mouse experiments. WIDER IMPLICATIONS OF THE FINDINGS The data presented are consistent with the notion that platelet-induced activation of the TGF-β/Smad signaling pathway may be a driving force in EMT, FMT and SMM in the development of adenomyosis, leading to fibrosis. This study provides the first piece of evidence that adenomyotic lesions are wounds that undergo repeated injury and healing, and, as such, platelets play critical roles in the development of adenomyosis by promoting proliferation, angiogenesis, increasing ECM deposits, and SMM, resulting in fibrosis. Platelets may also be involved in uterine hyperactivity and myometrial hyperinnervation. Our results provide one explanation as to why adenomyosis is a challenge for medical treatment, and shed new light onto the pathophysiology of adenomyosis. STUDY FUNDING/COMPETING INTERESTS Support for data collection and analysis was provided by grants from the National Science Foundation of China. None of the authors has anything to disclose.
Objective To investigate the expression pattern of proinflammatory, anti-inflammatory, and angiogenic cytokines and their effect on various mediators of endometrial receptivity in women with idiopathic recurrent spontaneous miscarriage (IRSM). Design A prospective study. Setting Tertiary care hospital and reproductive health research unit. Patient(s) Thirty-six women with IRSM (<35 years) and 30 fertile women as controls matched by age and body mass index undergoing sterilization. Intervention(s) Endometrial biopsies in all women corresponding to the window of implantation. Main Outcome Measure(s) Assessment of endometrial expression of proinflammatory, anti-inflammatory, and angiogenic cytokines, mediators of matrix turnover and angiogenesis, markers of receptivity. Result(s) A statistical significantly higher level of proinflammatory cytokines, mediators of matrix turnover and angiogenesis, and a reduced expression of anti-inflammatory and angiogenic cytokines were observed in women with IRSM. Additionally, the markers of endometrial receptivity were poorly expressed in women with IRSM. Conclusion(s) Aberrant expression of proinflammatory, anti-inflammatory, and angiogenic cytokines during implantation window in women with IRSM is one of the key factors that adversely affect endometrial development, as evidenced by the inadequate expression of various endometrial receptivity markers.
Establishment and maintenance of pregnancy in equids is only partially understood. To provide new insights into early events of this process, we performed a systematic analysis of transcriptome changes in the endometrium at Days 8 and 12 of pregnancy. Endometrial biopsy samples from pregnant and nonpregnant stages were taken from the same mares. Composition of the collected biopsy samples was analyzed using quantitative stereological techniques to determine proportions of surface and glandular epithelium and blood vessels. Microarray analysis did not reveal detectable changes in gene expression at Day 8, whereas at Day 12 of pregnancy 374 differentially expressed genes were identified, 332 with higher and 42 with lower transcript levels in pregnant endometrium. Expression of selected genes was validated by quantitative real-time RT-PCR. Gene set enrichment analysis, functional annotation clustering, and cocitation analysis were performed to characterize the genes differentially expressed in Day 12 pregnant endometrium. Many known estrogen-induced genes and genes involved in regulation of estrogen signaling were found, but also genes known to be regulated by progesterone and prostaglandin E2. Additionally, differential expression of a number of genes related to angiogenesis and vascular remodeling suggests an important role of this process. Furthermore, genes that probably have conserved functions across species, such as CRYAB, ERRFI1, FGF9, IGFBP2, NR2F2, STC1, and TNFSF10, were identified. This study revealed the potential target genes and pathways of conceptus-derived estrogens, progesterone, and prostaglandin E2 in the equine endometrium probably involved in the early events of establishment and maintenance of pregnancy in the mare.
Implantation is a key stage during pregnancy, as the fate of the embryo is often decided upon its first contact with the maternal endometrium. Around this time, DCs accumulate in the uterus; however, their role in pregnancy and, more specifically, implantation, remains unknown. We investigated the function of uterine DCs (uDCs) during implantation using a transgenic mouse model that allows conditional ablation of uDCs in a spatially and temporally regulated manner. Depletion of uDCs resulted in a severe impairment of the implantation process, leading to embryo resorption. Depletion of uDCs also caused embryo resorption in syngeneic and T cell-deficient pregnancies, which argues against a failure to establish immunological tolerance during implantation. Moreover, even in the absence of embryos, experimentally induced deciduae failed to adequately form. Implantation failure was associated with impaired decidual proliferation and differentiation. Dynamic contrast-enhanced MRI revealed perturbed angiogenesis characterized by reduced vascular expansion and attenuated maturation. We suggest therefore that uDCs directly fine-tune decidual angiogenesis by providing two critical factors, sFlt1 and TGF-beta 1, that promote coordinated blood vessel maturation. Collectively, uDCs appear to govern uterine receptivity, independent of their predicted role in immunological tolerance, by regulating tissue remodeling and angiogenesis. Importantly, our results may aid in understanding the limited implantation success of embryos transferred following in vitro fertilization.