Jemma Evans

Fresh versus frozen embryo transfer: backing clinical decisions with scientific and clinical evidence

BACKGROUND Improvements in vitrification now make frozen embryo transfers (FETs) a viable alternative to fresh embryo transfer, with reports from observational studies and randomized controlled trials suggesting that: (i) the endometrium in stimulated cycles is not optimally prepared for implantation; (ii) pregnancy rates are increased following FET and (iii) perinatal outcomes are less affected after FET. METHODS This review integrates and discusses the available clinical and scientific evidence supporting embryo transfer in a natural cycle. RESULTS Laboratory-based studies demonstrate morphological and molecular changes to the endometrium and reduced responsiveness of the endometrium to hCG, resulting from controlled ovarian stimulation. The literature demonstrates reduced endometrial receptivity in controlled ovarian stimulation cycles and supports the clinical observations that FET reduces the risk of ovarian hyperstimulation syndrome and improves outcomes for both the mother and baby. CONCLUSIONS This review provides the basis for an evidence-based approach towards changes in routine IVF, which may ultimately result in higher delivery rates of healthier term babies.

Inflammation, leukocytes and menstruation.

Menstruation has many of the features of an inflammatory process. The complexity and sequence of inflammatory-type events leading to the final tissue breakdown and bleeding are slowly being unravelled. Progesterone has anti-inflammatory properties, and its rapidly declining levels (along with those of estrogen) in the late secretory phase of each non-conception cycle, initiates a sequence of interdependent events of an inflammatory nature involving local inter-cellular interactions within the endometrium. Intracellular responses to loss of progesterone (in decidualized stromal, vascular and epithelial cells) lead to decreased prostaglandin metabolism and loss of protection from reactive oxygen species (ROS). Increased ROS results in release of NFκB from suppression with activation of target gene transcription and increased synthesis of pro-inflammatory prostaglandins, cytokines, chemokines and matrix metalloproteinases (MMP). The resultant leukocyte recruitment, with changing phenotypes and activation, provide further degradative enzymes and MMP activators, which together with a hypoxic environment induced by prostaglandin actions, lead to the tissue breakdown and bleeding characteristic of menstruation. In parallel, at sites where shedding is complete, microenvironmentally-induced changes in phenotypes of neutrophils and macrophages from pro- to anti-inflammatory, in addition to induction of growth factors, contribute to the very rapid re-epithelialization and restoration of tissue integrity.

The Microenvironment of Human Implantation: Determinant of Reproductive Success.

Successful implantation requires synchronous development of embryo and endometrium. Endometrial receptivity results from progesterone‐induced differentiation of endometrial cells, generally achieved during the mid‐secretory phase of the cycle. Failure to properly develop receptivity results in failed or inadequate implantation and hence no ongoing pregnancy. The blastocyst undergoes final development, apposition, attachment and initiates invasion of the endometrial epithelium within the uterine cavity. Thus, the microenvironment provided by uterine fluid, particularly glandular secretions, is essential for implantation. Analysis of endometrial fluid has identified cytokines, chemokines, proteases, antiproteases and other factors that modulate blastocyst functions relevant to implantation. Exosomes/microvesicular bodies released from the endometrium (and likely also the embryo) are present in uterine fluid. These can transfer miRNA, proteins and lipids between cells, thus providing endometrial–embryo communication in the peri‐implantation period. Understanding the uterine microenvironment, and its effects on endometrial–embryo interactions, will provide opportunities to modify current infertility treatments to improve success rates.

Defective Soil for a Fertile Seed? Altered Endometrial Development Is Detrimental to Pregnancy Success

Background Synchronous development of the endometrium (to achieve a receptive state) and of the embryo is essential for successful implantation and ongoing pregnancy. Endometrial receptivity exists only for a finite time in a menstrual cycle and the endometrium is refractory to embryo implantation outside of this window. Administration of hormones to stimulate multifollicular development within the ovary, integral to the majority of assisted reproduction (ART) protocols, dramatically alters the hormonal milieu to which the endometrium is exposed versus normal menstrual cycles. Endometrial maturation may be profoundly affected by this altered endocrine environment. Aim Compare endometrial histology in fertile women, fertile women undergoing hormonal stimulation for oocyte donation and infertile women undergoing fresh embryo transfers in an ART cycle with further comparisons between women who did or did not become pregnant. Examine the presence of leukocytes and markers of endometrial maturation. Methods Endometrial histology was examined by hematoxylin and eosin staining with a semi quantitative scoring method developed to compare histological appearance of tissues. The presence of leukocytes and developmental markers was examined by immunohistochemistry and scored. Results Endometrial histology was dramatically altered upon stimulation for ART. However, those women who became pregnant presented with significantly less alterations in histological endometrial maturation. Numbers and activation status of leukocyte populations were also altered within the endometria stimulated for ART, with neutrophils undergoing degranulation, usually observed only pre-menstrually. Conclusion We propose that such developmental changes render the endometrium hostile to the embryo and that modifications to ART protocols should be considered to take account of the requirement for endometrial receptivity and hence increase pregnancy rates.

Decidualized Human Endometrial Stromal Cells Are Sensors of Hormone Withdrawal in the Menstrual Inflammatory Cascade

ABSTRACT Menstruation is a complex process dependent on premenstrual release of inflammatory mediators and proteolytic enzymes from endometrial cells. Endometrial leukocytes are traditionally considered to be the major source of the inflammatory factors. However, evidence is emerging to suggest a role for decidualized endometrial stromal cells in the premenstrual inflammatory cascade. We sought to determine if withdrawal of hormone support (estrogen and progesterone) from decidualized endometrial stromal cells, in a model mimicking the precise timing leading to menstruation, activated inflammatory signaling pathways and downstream release of inflammatory mediators. Human endometrial stromal cells decidualized gradually over 12 days of estradiol and progestin treatment as evidenced by an increase in prolactin secretion. Withdrawal of hormone support from decidualized stromal cells resulted in a decrease in cytoplasmic IkappaB and a progressive increase in nuclear accumulation of NF-kappaB, as demonstrated by Western immunoblot and immunocytochemical analyses. Concomitant with nuclear translocation of NF-kappaB, hormone withdrawal led to production of a host of inflammatory mediators by the decidualized stromal cells, including IFN-alpha, IL-6, CCL11, GM-CSF, CCL2, IL1-RA, CXCL10, CXCL8, IL-12, IL-15, VEGF, and CCL5. Elevation of inflammatory mediators was not observed, however, upon hormone withdrawal in cells treated with the NF-kappaB inhibitor BAY 11–7085. Decidualized stromal cells are likely highly sensitive sensors of changing hormone levels. This provides a mechanism by which decidualized stromal cells may recruit inflammatory leukocytes into the premenstrual endometrium and contribute to the intense inflammation underlying this unique physiological process.

Fertile ground: human endometrial programming and lessons in health and disease

The human endometrium is a highly dynamic tissue that is cyclically shed, repaired, regenerated and remodelled, primarily under the orchestration of oestrogen and progesterone, in preparation for embryo implantation. Humans are among the very few species that menstruate and that, consequently, are equipped with unique cellular and molecular mechanisms controlling these cyclic processes. Many reproductive pathologies are specific to menstruating species, and studies in animal models rarely translate to humans. Abnormal remodelling and regeneration of the human endometrium leads to a range of reproductive complications. Furthermore, the processes regulating endometrial remodelling and implantation, including those controlling hormonal impact, breakdown and repair, stem/progenitor cell activation, inflammation and cell invasion have broad applications to other fields. This Review presents current knowledge regarding the normal and abnormal function of the human endometrium. The development of biomarkers for prediction of uterine diseases and pregnancy disorders and future avenues of investigation to improve fertility and enhance endometrial function are also discussed.

Endometrial signals improve embryo outcome: functional role of vascular endothelial growth factor isoforms on embryo development and implantation in mice

STUDY QUESTION Does vascular endothelial growth factor (VEGF) have important roles during early embryo development and implantation? SUMMARY ANSWER VEGF plays key roles during mouse preimplantation embryo development, with beneficial effects on time to cavitation, blastocyst cell number and outgrowth, as well as implantation rate and fetal limb development. WHAT IS KNOWN ALREADY Embryo implantation requires synchronized dialog between maternal cells and those of the conceptus. Following ovulation, secretions from endometrial glands increase and accumulate in the uterine lumen. These secretions contain important mediators that support the conceptus during the peri-implantation phase. Previously, we demonstrated a significant reduction of VEGFA in the uterine cavity of women with unexplained infertility. Functional studies demonstrated that VEGF significantly enhanced endometrial epithelial cell adhesive properties and embryo outgrowth. STUDY DESIGN, SIZE, DURATION Human endometrial lavages (n = 6) were obtained from women of proven fertility. Four-week old Swiss mice were superovulated and mated with Swiss males to obtain embryos for treatment with VEGF in vitro. Preimplantation embryo development was assessed prior to embryo transfer (n = 19-30/treatment group/output). Recipient F1 female mice (8-12 weeks of age) were mated with vasectomized males to induce pseudopregnancy and embryos were transferred. On Day 14.5 of pregnancy, uterine horns were collected for analysis of implantation rates as well as placental and fetal development (n = 14-19/treatment). PARTICIPANTS/MATERIALS, SETTING, METHODS Lavage fluid was assessed by western immunoblot analysis to determine the VEGF isoforms present. Mouse embryos were treated with either recombinant human (rh)VEGF, or VEGF isoforms 121 and 165. Preimplantation embryo development was quantified using time-lapse microscopy. Blastocysts were (i) stained for cell number, (ii) transferred to wells coated with fibronectin to examine trophoblast outgrowth or (iii) transferred to pseudo pregnant recipients to analyze implantation rates, placental and fetal development. MAIN RESULTS AND THE ROLE OF CHANCE Western blot analysis revealed the presence of VEGF121 and 165 isoforms in human uterine fluid. Time-lapse microscopy analysis revealed that VEGF (n = 22) and VEGF121 (n = 23) treatment significantly reduced the preimplantation mouse embryo time to cavitation (P < 0.05). VEGF and VEGF165 increased both blastocyst cell number (VEGF n = 27; VEGF165 n = 24: P < 0.001) and outgrowth (n = 15/treatment: 66 h, P < 0.001; 74, 90, 98 and 114 h, P < 0.01) on fibronectin compared with control. Furthermore, rhVEGF improved implantation rates and enhanced fetal limb development (P < 0.05). LIMITATIONS, REASONS FOR CAUTION Due to the nature of this work, embryo development and implantation was only examined in the mouse. WIDER IMPLICATIONS OF THE FINDINGS The absence or reduction in levels of VEGF during the preimplantation period likely affects key events during embryo development, implantation and placentation. The potential for improvement of clinical IVF outcomes by the addition of VEGF to human embryo culture media needs further investigation. STUDY FUNDING/COMPETING INTERESTS This study was supported by a University of Melbourne Early Career Researcher Grant #601040, the NHMRC (L.A.S., Program grant #494802; Fellowship #1002028; N.J.H., Fellowship # 628927; J.E.; project grant #1047756) and L.A.S., Monash IVF Research and Education Foundation. N.K.B. was supported by an Australian Postgraduate Award. Work at PHI-MIMR Institute was also supported by the Victorian Governments Operational Infrastructure Support Program. There are no conflicts of interest to declare.

Dynamic changes in hyperglycosylated human chorionic gonadotrophin throughout the first trimester of pregnancy and its role in early placentation

STUDY QUESTION What is the in situ localization and function of hyperglycosylated hCG (hCG-H) in first trimester pregnancy tissues? SUMMARY ANSWER HCG-H localizes to the syncytiotrophoblast, cytotrophoblast and invasive extravillous trophoblast within the maternal decidua and promotes invasion during the first trimester of pregnancy. WHAT IS KNOWN ALREADY Serum levels of hCG-H decline dramatically throughout the first trimester of pregnancy. As hCG-H is produced by choriocarcinoma cells, it is proposed to regulate trophoblast invasion. STUDY DESIGN, SIZE, DURATION Tissues were collected from elective first trimester pregnancy terminations. Placental villous and decidua basalis were collected from Week 6 to Week 12 of gestation (n = 49). PARTICIPANTS/MATERIALS, SETTING, METHODS Tissues were collected from elective first trimester surgical pregnancy terminations to determine localization, abundance and function of hCG-H. Placental villous outgrowth studies determined the impact of neutralizing endogenous hCG-H on trophoblast function. Real-time proliferation, migration and invasion assays using JEG-3 choriocarcinoma cells further elucidated the role of hCG-H in trophoblast function. MAIN RESULTS AND THE ROLE OF CHANCE HCG-H localized to syncytiotrophoblast layer of the placental villous from gestational weeks 6-9; thereafter hCG-H localized as a discrete layer between syncytio- and cyto-trophoblast layers. Immunoreactive hCG-H was also observed within the cytotrophoblast layer in Week 7-8 of gestation. HCG-H abundance decreased within placental villous from Weeks 6-12 of gestation (n = 3 placentas per gestational weeks 6-12). HCG-H also localized to anchoring villi within maternal decidua, extravillous trophoblasts invading into the maternal decidua and endovascular trophoblasts remodeling maternal blood vessels. Treatment of primary first trimester villous explants with hCG-H neutralizing antibody reduced trophoblast outgrowth (n = 3 placentas, P < 0.05). Treatment of a trophoblast cell line with neutralizing antibody reduced trophoblast invasion (n = 4, P < 0.05) but did not affect migration or proliferation. LIMITATIONS, REASONS FOR CAUTION Functional invasion and migration assays performed using cell lines. Not possible to perform such assays with primary human material. WIDER IMPLICATIONS OF THE FINDINGS HCG-H is an important autocrine factor facilitating trophoblast invasion in the first trimester of pregnancy. Targeting hCG-H may prove useful in the treatment of pathologic pregnancies, such as ectopic pregnancies, or pregnancy complications including pre-eclampsia and gestational trophoblast diseases. STUDY FUNDING/COMPETING INTERESTS This work was supported by the Victorian Government Operational Infrastructure Support Program. J.E. is supported by NHMRC project grant #1047756, L.A.S. and E.D. by NHMRC Fellowships #1002018 and #550905 respectively and E.M. by an NHMRC Early Career Fellowship #611827. The authors have no conflicts of interest relating to this work.

Alternate roles for immune regulators: establishing endometrial receptivity for implantation.

Many immune regulators are now identified as having key roles at the embryo–maternal interface. Importantly, a cohort of cytokines, chemokines and growth factors are produced by the endometrial glands and secreted into the uterine cavity where they act both on the blastocyst and on the endometrial surface, changing adhesive capacity, modifying blastocyst development and outgrowth and providing chemoattraction, in addition to their previously known functions in immune regulation. As implantation progresses to highly controlled invasion of the trophoblast through the maternal decidua, similar factors produced by glands, decidual cells and cells of the innate immune system are critical for guiding the trophoblast to the maternal vasculature and establishing a functional placenta. Disturbance to production or action of such mediators can result in loss of uterine receptivity (manifesting as infertility) or disorders of early pregnancy including recurrent miscarriage and preeclampsia.

Hyperglycosylated hCG: a Unique Human Implantation and Invasion Factor

Human chorionic gonadotropin (hCG), as one of the first embryonic products, has been extensively investigated for its role in implantation and placental development. Discovery of an over‐glycosylated form of this hormone, hyperglycosylated hCG (hCG‐H), has provided an additional level of complexity in our understanding of the implantation and placentation process; the structure, activity and functional implications of alterations in hCG isoforms throughout pregnancy are still being characterized. HCG‐H comprises up to 90% of total hCG measurable in serum and urine during the first 2–3 weeks of pregnancy when invasive trophoblast activity is high, dropping to negligible proportions, less than 5%, of total hCG at the end of the first trimester. Functionally, hCG‐H promotes trophoblast invasion during early pregnancy and has potential roles in immune cell modulation and endothelial function within the uterus at the time of pregnancy initiation. Altered levels of hCG‐H are characteristics of pregnancy complications of altered trophoblast function and inadequate placentation, such as pre‐eclampsia, and also over‐abundance of invasive cytotrophoblasts, such as Downs syndrome. Improving our basic knowledge of the functional role‐specific hCG isoforms plays in the complex cascade of events involved in implantation and placental development, and determining dynamic changes in the structure and activity of hCG isoforms throughout gestation will facilitate evidence‐based decisions in assisted reproduction/in vitro fertilization based on the potential of embryos to implant, provide biomarkers for diagnosis of pregnancy complications associated with altered placental development and enhance understanding of how hCG isoforms may influence receptivity of the endometrium.