Is the zona pellucida an intrinsic source of signals activating maternal recognition of the developing mammalian embryo?

Effect of human peripheral blood mononuclear cells (hPBMCs) on mouse endometrial cell proliferation: a potential therapeutics for endometrial regeneration

OBJECTIVES

The persistently thin endometrium is a major cause of repeated implantation failure; however, there is no definite treatment for it yet. This study aimed to confirm the potential of human peripheral blood mononuclear cells (hPBMCs) as a therapeutic agent for endometrial regeneration.

DESIGN

Experimental study Participants/Materials, Setting, Methods: To assess the in vitro effect of hPBMC, the human primary endometrial epithelial cell lines SNU-685 and SNU-1077 were co cultured with or without 1×10^5 hPBMCs for 24 hours. To evaluate the in vivo effect, either 1×10^5 hPBMCs in PBS or PBS alone were injected into the left uterine horn of NOD-SCID mice, and the right untreated uterine horn was used as control.

RESULTS

Co-culture with hPBMCs stimulated significant proliferation in both SNU-685 and SNU-1077 cell lines (p=0.002 and 0.044, respectively). Moreover, treatment with hPBMCs significantly increased the thickness in all parts of the endometrium compared with that in the untreated control uterine horn (proximal: 1.69±0.19 vs. 1.00±0.10, p=0.009; middle: 1.51±0.14 vs. 1.00±0.12, p=0.010; distal: 1.72±0.22 vs. 1.00±0.12, p=0.003, respectively). Compared with the PBS injection group, the hPBMC injection group had significantly thickened endometrium in the middle (P=0.036) and distal segments (P=0.002) of the uterine horn. Immunohistochemical analysis revealed the presence of exogenously injected hPBMCs in the uterus of recipient mice. hPBMC-recipient mice had cyclic uterus with normal histology in the endometrium.

LIMITATIONS

hPBMCs were not applied directly to a mouse model with thin endometrium, so further study is needed.

CONCLUSION

The beneficial effect of hPBMCs on endometrium may suggest their clinical feasibility for the safe treatment of infertile patients with persistently thin endometrium.

Embryos, cancers, and parasites: Potential applications to the study of reproductive biology in view of their similarity as biological phenomena

Background

At present, there are so many living things on the earth. Most of these organisms have a reproductive strategy called sexual reproduction. Among organisms that reproduce sexually, mammals have an extremely complex and seemingly unnatural method of reproduction, or viviparity.

Methods

As an approach to understanding the nature of viviparity, the author have tried to outline the common life phenomena of embryos, cancers, and parasites based on the literature to date, with internal parasites as the keyword.

Main findings

Embryo, cancer, and parasite are constituted as a systemic interaction with the host (mother). Based on these facts, the author proposed the hypothesis that in the case of mammals, "the fetus is essentially harmful to the mother", and that the parasitic fetus grows by skillfully evading the mother's foreign body exclusion mechanism.

Conclusion

Comparative studies of "embryos", "cancers", and "parasites" as foreign bodies have the potential to produce unexpected discoveries in their respective fields. It is important to consider the evolutionary time axis that the basic structure of our mammalian body arose over 200 million years from the Mesozoic Triassic, the period immediately after the Paleozoic Era, when life on Earth became massively extinct.

Domestic cat embryos generated without zona pellucida are capable of developing in vitro but exhibit abnormal gene expression and a decreased implantation rate

The removal of the zona pellucida has been used to improve the in vitro development of domestic cat embryos generated by IVF and SCNT. However, the in vivo development of domestic cat embryos generated without the zona pellucida has not been evaluated. The objective of this study was to evaluate the effects of zona pellucida removal on the in vitro and in vivo development of domestic cat embryos generated by IVF. For this purpose, two experimental groups were created: 1) domestic cat embryos cultured in vitro (Zona-intact group, ZI) and 2) domestic cat embryos cultured in vitro without the zona pellucida (Zona-free group, ZF). Domestic cat embryos were generated by IVF and cultured in vitro for 8 days. In the ZF group, the zona pellucida was removed after IVF, and embryos were cultured using the well of the well system (WOW). Cleavage, morula and blastocyst rates were evaluated in both groups. The diameter and total cell number of blastocysts were assessed. Relative expression of pluripotency (OCT4, SOX2 and NANOG), differentiation (CDX2 and GATA6) and apoptotic markers (BAX and BCL2) was evaluated in blastocysts. Finally, to evaluate in vivo development, embryos at days 5, 6 and 7 of development were transferred into recipient domestic cats, and ultrasonography was performed to evaluate implantation. No differences were observed in the cleavage, morula or blastocyst rates between embryos from the ZI and ZF groups. The diameter (mean ± SD) of blastocysts from the ZF group was greater (253.4 ± 83.3 μm) than that from the ZI group (210.5 ± 78.5 μm). No differences were observed in the relative expression of OCT4, CDX2 or GATA6. However, the relative expression of SOX2 and NANOG was significantly reduced in ZF blastocysts compared to ZI blastocysts. Furthermore, the relative expression of BAX was higher in ZF blastocysts than in ZI blastocysts. Finally, four pregnancies were confirmed after the transfer of ZI embryos (n = 110). However, no pregnancies were observed after the transfer of ZF embryos at the morula or blastocyst stage (n = 56). In conclusion, domestic cat embryos cultured without the zona pellucida were able to develop in vitro until the blastocyst stage. However, the removal of the zona pellucida negatively affected the gene expression of pluripotency and apoptosis markers, and ZF embryos were unable to implant. This might indicate that the removal of the zona pellucida is detrimental for the implantation and in vivo development of domestic cat embryos.

Intrauterine Infusion of TGF-β1 Prior to Insemination, Alike Seminal Plasma, Influences Endometrial Cytokine Responses but Does Not Impact the Timing of the Progression of Pre-Implantation Pig Embryo Development

Seminal plasma (SP) in the female genital tract induces changes that affect multiple reproductive processes. One of the active components in SP is the transforming growth factor β1 (TGF-β1), which has major roles in embryo development and pregnancy. Embryo transfer (ET) technology is welcomed by the pig industry provided that embryo quality at embryo collection as well as the fertility and prolificacy of the recipients after the ET is increased. This study evaluated different intrauterine infusion treatments at estrus (40 mL of SP, TGF-β1 cytokine in the extender, or the extender alone (control)) by mimicking an ET scenario in so-called "donor" (inseminated) and "recipient" (uninseminated) sows. On day 6 (day 0-onset of estrus), all "donors" were laparotomized to determine their pregnancy status (presence and developmental stage of the embryos). In addition, endometrial explants were collected from pregnant "donors" and cyclic "recipients," incubated for 24 h, and analyzed for cytokine production. SP infusions (unlike TGF-β1 infusions) positively influenced the developmental stage of day 6 embryos. Infusion treatments differentially influenced the endometrial cytokine production, mainly in donors. We concluded that SP infusions prior to AI not only impacted the porcine preimplantation embryo development but also influenced the endometrial cytokine production six days after treatment, both in donors and recipients.

Blastocyst-Bearing Sows Display a Dominant Anti-Inflammatory Cytokine Profile Compared to Cyclic Sows at Day 6 of the Cycle

Simple Summary

A proper uterine environment is basic for obtaining optimal embryo transfer outputs in domestic species, including the pig. However, scarce information is available about the uterine immune response of recipient (uninseminated) sows when receiving embryos during embryo transfer. Endometrial cytokine profile is among the main factors regulating uterine receptivity to embryos. In this study, using Luminex MAP^® technology, we found important differences in the endometrial production in most of the 16 cytokines analyzed between recipient sows and embryo-bearing (inseminated) sows six days after estrus, with a predominant cytokine anti-inflammatory environment in the embryo-bearing endometria. These observations suggest that insemination components and/or early embryos induce an endometrium immune-tolerant cytokine profile at Day 6 of the cycle. The findings could contribute importantly to design strategies to maximize the reproductive performance of recipients after embryo transfer in swine.

Abstract

In the context of porcine embryo transfer (ET) technology, understanding the tightly regulated local uterine immune environment is crucial to achieve an adequate interaction between the transferred embryos and the receiving endometrium. However, information is limited on the uterine immune status of cyclic-recipient sows when receiving embryos during ET. The present study postulated that the anti- and proinflammatory cytokine profile 6 days after the onset of estrus differs between endometria from uninseminated cyclic sows and blastocyst-bearing sows. On Day 6 of the cycle, endometrial explants were collected from sows inseminated or not inseminated during the postweaning estrus and cultured for 22 h. The culture medium was then analyzed for the contents of a total of 16 cytokines using Luminex MAP^® technology. The results showed important differences in the endometrial production of most cytokines between the sow categories, with a predominant anti-inflammatory environment displayed by the blastocyst-bearing endometria. These findings suggest that sperm, seminal plasma (SP) and/or early embryos modify the uterine environment by inducing an immune-tolerant cytokine profile already visible at Day 6. Whether the SP or some of its active components may help to develop strategies to maximize the reproductive performance of recipients after ET needs further investigation.

Intrauterine administration of autologous hCG- activated peripheral blood mononuclear cells improves pregnancy outcomes in patients with recurrent implantation failure; A double-blind, randomized control trial study

We aimed to investigate the effect of intrauterine administration of autologous hCG-activated PBMCs in RIF women with low Th-17/Treg cell ratio. 248 women with a history of implantation failure volunteered to receive PBMC-therapy. After immunologic consultation and doing flow cytometry analysis, 100 women with at least three IVF/ET failure who had low Th-17/Treg ratio in comparison with healthy control were enrolled in this study. These 100 patients were randomly divided into two groups as PBMC receiving (n = 50) and controls (n = 50). Then PBMCs were obtained from patients and treated with hCG for 48 h. Afterward, PBMCs were administered into the uterine cavity of the patient in the study group, two days before ET. The concentration of inflammatory cytokines was examined in the supernatant of cultured PBMCs after 2, 24, and 48 h of incubation using the ELISA method. The frequency of Th-17, Treg, and the Th-17/Treg ratio was significantly lower in RIF women than the healthy controls (P < 0.0001). The secretion of inflammatory cytokines was significantly higher after 48 h compared to 2 and 24 h (P < 0.0001). The pregnancy and live birth rate were significantly increased in women undergoing the PBMC-therapy compared to control (PBS-injecting) group (P = 0.032 and P = 0.047, respectively). The miscarriage rate was considerably lower in PBMC-therapy group (P = 0.029). Our findings suggest that intrauterine administration of autologous in vitro hCG-activated PBMCs improves pregnancy outcomes in patients with at least three IVF/ET failures.

Promoting Roles of Embryonic Signals in Embryo Implantation and Placentation in Cooperation with Endocrine and Immune Systems

Embryo implantation in the uterus is an essential process for successful pregnancy in mammals. In general, the endocrine system induces sufficient embryo receptivity in the endometrium, where adhesion-promoting molecules increase and adhesion-inhibitory molecules decrease. Although the precise mechanisms remain unknown, it is widely accepted that maternal–embryo communications, including embryonic signals, improve the receptive ability of the sex steroid hormone-primed endometrium. The embryo may utilize repulsive forces produced by an Eph–ephrin system for its timely attachment to and subsequent invasion through the endometrial epithelial layer. Importantly, the embryonic signals are considered to act on maternal immune cells to induce immune tolerance. They also elicit local inflammation that promotes endometrial differentiation and maternal tissue remodeling during embryo implantation and placentation. Additional clarification of the immune control mechanisms by embryonic signals, such as human chorionic gonadotropin, pre-implantation factor, zona pellucida degradation products, and laeverin, will aid in the further development of immunotherapy to minimize implantation failure in the future.

Platelet-rich plasma or blood-derived products to improve endometrial receptivity?

The use of platelet-rich plasma (PRP) to improve endometrial receptivity is gaining increasing attention in assisted reproduction technologies. The authors report that autologous PRP intrauterine administration improves pregnancy and birth rates, particularly in cases of patients presenting poor endometrial growth. Different groups of scientists proposed a similar approach years ago using whole blood-derived products also to improve endometrial receptivity. The important role played by cytokines and growth factors during embryo implantation has been well-known for a long time. These signaling molecules are present and released by blood cells during physiological, normal endometrial growth and implantation. Similar blood mediators are released from platelet granules upon a blood vessel injury. Methods described for PRP preparation for intrauterine administration are not precise, and they seem to be similar to those used to prepare peripheral blood-derived products. Thus, it is possible that when preparing PRP from whole blood, the final plasma product used as "PRP" contains platelets in addition to the important cytokines and growth factors released by the peripheral blood mononuclear cells present in the whole blood. Precise knowledge of the identity, concentration, and effects of the individual blood factors, their origin, whether platelets or blood mononuclear cells, will greatly contribute to improve and to make results obtained in fertility treatments more repeatable.

Oviduct epithelium induces interferon-tau in bovine Day-4 embryos, which generates an anti-inflammatory response in immune cells

Recent studies indicate that communication between the bovine embryo and the mother begins in the oviduct. Here, we aimed to investigate the effect of embryos on bovine oviducts for their immune responses using an in vitro model. First, zygotes were cultured with or without bovine oviduct epithelial cells (BOECs) for 4 days, when embryos had reached the 16-cell stage. At that time, we detected interferon-tau (IFNT) in embryos co-cultured with BOECs, but not in embryos cultured alone. Next, peripheral blood mononuclear cells (PBMCs) were incubated either in media from embryo alone cultures or from co-cultures of embryos with BOECs. The medium from embryo alone cultures did not modulate PBMCs gene expression; whereas the embryo-BOEC co-culture medium increased interferon-stimulated genes (ISGs: ISG15, OAS1, MX2), STAT1, PTGES and TGFB1 but suppressed IL17 expression in PBMCs. Both IFNT-treated BOEC culture medium and IFNT-supplemented fresh medium alone without BOEC, modulated PBMCs gene expressions similar to those by the embryo-BOEC co-culture medium. Further, specific antibody to IFNT neutralized the effect of embryo-BOEC co-culture medium on PBMCs gene expression. Our results indicate that BOECs stimulate embryos to produce IFNT, which then acts on immune cells to promote an anti-inflammatory response in the oviduct.

Bovine embryo induces an anti-inflammatory response in uterine epithelial cells and immune cells in vitro: possible involvement of interferon tau as an intermediator

Recent observations suggest that the bovine uterus starts to react to the early embryo immediately after its arrival from the oviduct. The present study aimed to investigate the effect of the early developing embryo on the immune-related gene profile in bovine uterine epithelial cells (BUECs) in vitro, and to further examine the impact of conditioned media (CM), either from embryo-BUEC co-culture or embryo culture alone, on gene expression in peripheral blood mononuclear cells (PBMCs). First, BUECs were co-cultured with morulae (n = 10) for D5-D9 (D0 = IVF), and gene expression in BUECs was analyzed. Subsequently, PBMCs were cultured in CM from embryo-BUEC co-culture or D5-D9 embryo culture, and gene expression was evaluated. In BUECs, the embryo induced interferon (IFN)-stimulated genes (ISGs: ISG15, OAS1, and MX2), a key factor for IFN-signaling (STAT1), and type-1 IFN receptors (IFNAR1 and IFNAR2), with suppression of NFkB2, NFkBIA and pro-inflammatory cytokines (TNFA and IL1B). The embryo also stimulated PTGES and PGE2 secretion in BUECs. In PBMCs, both CM from embryo-BUEC co-culture and embryo culture alone induced ISGs, STAT1 and TGFB1, while suppressing TNFA and IL17. Similarly, interferon tau (IFNT) at 100 pg/ml suppressed NFkB2, TNFA and IL1B in BUECs, and also stimulated TGFB1 and suppressed TNFA in PBMCs. Our findings suggest that the bovine embryo, in the first four days in the uterus (D5-D9), starts to induce an anti-inflammatory response in epithelial cells and in immune cells. IFNT is likely to act as one of the intermediators for induction of the anti-inflammatory response in the bovine uterus.

Dual Positive Regulation of Embryo Implantation by Endocrine and Immune Systems--Step-by-Step Maternal Recognition of the Developing Embryo

In humans, HCG secreted from the implanting embryo stimulates progesterone production of the corpus luteum to maintain embryo implantation. Along with this endocrine system, current evidence suggests that the maternal immune system positively contributes to the embryo implantation. In mice, immune cells that have been sensitized with seminal fluid and then the developing embryo induce endometrial differentiation and promote embryo implantation. After hatching, HCG activates regulatory T and B cells through LH/HCG receptors and then stimulates uterine NK cells and monocytes through sugar chain receptors, to promote and maintain pregnancy. In accordance with the above, the intrauterine administration of HCG-treated PBMC was demonstrated to improve implantation rates in women with repeated implantation failures. These findings suggest that the maternal immune system undergoes functional changes by recognizing the developing embryos in a stepwise manner even from a pre-fertilization stage and facilitates embryo implantation in cooperation with the endocrine system.

Effects of seminal plasma and the presence of a conceptus on regulation of lymphocyte-cytokine network in porcine endometrium

Infusion of seminal plasma in the uterus is known to elicit an instant inflammatory response in the porcine uterus, but whether or not it prepares a uterine immunological response to the presence of conceptuses is not well understood. Seminal plasma induced long-term modulatory effects and conceptus-induced immune changes in leukocyte populations were measured by flow cytometry and mRNAs for various cytokines by quantitative reverse-transcriptase PCR in porcine endometrium collected on Days 6 and 13 from cycling and pregnant animals or from animals given seminal plasma infusions. Seminal plasma infusion induced long-term modulatory effects, resulting in significantly more endometrial FoxP3-positive T-regulatory and T-helper cells 6 days after infusion as compared to cycling and pregnant animals. The number of T-cytotoxic and T-null cells did not change between the studied groups. The early molecular effects of seminal plasma were not observed at 13-days post-infusion, although animals on Day 13 of pregnancy did show significantly more T-cells (of any type investigated). Seminal plasma also showed a delayed effect on cytokine expression, specifically exhibiting a significant increase in interleukin 10 (IL10) and a decrease in granulocyte macrophage colony-stimulating factor (GMCSF) gene expression on Day 13 as compared to Day 6 of cycling or pregnant gilts. The results indicate a delayed regulatory effect of seminal plasma on immune responses in the porcine uterus, which are similar to immune changes generated by implanting conceptuses.

Infertility and Immunocontraception based on zona pellucida

The zona pellucida (ZP) is an extracellular matrix surrounding ovarian oocytes, ovulated eggs and preimplantation embryos. It plays several important roles at different stages of reproduction. Its constituent glycoproteins are expressed specifically in the ovary. It is thus possible to produce autoantibodies to ZP proteins that interfere with reproductive functions including folliculogenesis, fertilization and implantation. First, this article describes the history of anti-ZP antibodies detected in women with idiopathic infertility. Second, the current relationship between anti-ZP antibodies and infertility is discussed in relation to assisted reproductive medicine. Third, we introduce the latest studies of animal experiments involving the ZP. Finally, immunocontraceptive vaccine development using various ZP antigens is reviewed.

Early developing pig embryos mediate their own environment in the maternal tract

The maternal tract plays a critical role in the success of early embryonic development providing an optimal environment for establishment and maintenance of pregnancy. Preparation of this environment requires an intimate dialogue between the embryo and her mother. However, many intriguing aspects remain unknown in this unique communication system. To advance our understanding of the process by which a blastocyst is accepted by the endometrium and better address the clinical challenges of infertility and pregnancy failure, it is imperative to decipher this complex molecular dialogue. The objective of the present work is to define the local response of the maternal tract towards the embryo during the earliest stages of pregnancy. We used a novel in vivo experimental model that eliminated genetic variability and individual differences, followed by Affymetrix microarray to identify the signals involved in this embryo-maternal dialogue. Using laparoscopic insemination one oviduct of a sow was inseminated with spermatozoa and the contralateral oviduct was injected with diluent. This model allowed us to obtain samples from the oviduct and the tip of the uterine horn containing either embryos or oocytes from the same sow. Microarray analysis showed that most of the transcripts differentially expressed were down-regulated in the uterine horn in response to blastocysts when compared to oocytes. Many of the transcripts altered in response to the embryo in the uterine horn were related to the immune system. We used an in silico mathematical model to demonstrate the role of the embryo as a modulator of the immune system. This model revealed that relatively modest changes induced by the presence of the embryo could modulate the maternal immune response. These findings suggested that the presence of the embryo might regulate the immune system in the maternal tract to allow the refractory uterus to tolerate the embryo and support its development.

Immunopharmacology of ulipristal as an emergency contraceptive

A new progesterone antagonist, ulipristal has been made available as an emergency contraceptive. Ulipristal’s major mechanism of action as an emergency contraceptive has been ascribed to its ability to delay ovulation beyond the life span of the sperm. This paper analyzes the potential action of ulipristal (1) when unprotected intercourse and administration of ulipristal occur outside the fertility window and (2) when unprotected intercourse and administration of ulipristal occur at or within 24 hours of ovulation. When unprotected intercourse and the use of a single low dose of ulipristal occur outside of the fertility window, ulipristal behaves like a placebo. When unprotected intercourse and the use of a single low dose of ulipristal occur within the fertility window but before ovulation, ulipristal behaves like an emergency contraceptive by delaying ovulation and thereby preventing fertilization. When unprotected intercourse and the administration of ulipristal occur at or within 24 hours of ovulation, then ulipristal has an abortifacient action. It is proposed that the abortifacient mechanism of a low dose of ulipristal taken after fertilization but before implantation is due to the ability of ulipristal to block the maternal innate immune system to become immunotolerant to the paternal allogenic embryo. Progesterone’s critical immunotolerant actions involving early pregnancy factor, progesterone-induced blocking factor, and uterine natural killer cells are compromised by ulipristal.

Intrauterine administration of autologous peripheral blood mononuclear cells increases clinical pregnancy rates in frozen/thawed embryo transfer cycles of patients with repeated implantation failure

Intrauterine administration of autologous peripheral blood mononuclear cells (PBMC) activated by HCG in vitro are reported to improve implantation rates in patients with repeated failure of IVF-ET. In this study, we examined the effects of intrauterine administration of freshly isolated PBMC on clinical pregnancy and the implantation rates of patients who received frozen/thawed embryo transfer by prospective cohort study. Patients who had not achieved a successful pregnancy despite at least one or more IVF-ET sessions were enrolled in this study (n = 253, 253 cycles). Based on the patient's treatment preferences, PBMC were freshly isolated from each patient and then administered to the intrauterine cavity of that patient. Frozen/thawed embryo transfer was performed and the success of implantation in the PBMC-treated group (n = 83, 83 cycles) was compared with that in the non-treated control groups (n = 170, 170 cycles). There were no significant differences in the clinical pregnancy rate (34.9% vs. 32.9%), implantation rate (21.6% vs. 21.1%) and live birth delivery rate (21.7% vs. 21.8%) between PBMC-treated and non-treated groups. However, when the analyses were restricted to patients who had three or more implantation failures, the clinical pregnancy rate and the implantation rate in the PBMC-treated group (42.1% and 25.0%, p<0.05; n = 19 and 32, respectively) were significantly higher than those in the non-treated group (16.7% and 9.4%, p<0.05; n = 36 and 64, respectively). These findings indicate that intrauterine administration of autologous PBMC freshly isolated from patients, effectively improves embryo implantation in patients with three or more IVF failures.