Differential Expression of Alternatively Spliced Transcripts of HLA-G in Human Preimplantation Embryos and Inner Cell Masses

Exosomes as modulators of embryo implantation

Exosomes, known as extracellular vehicles (EVs), are found in biological fluids. They have the capability to carry and transfer signaling molecules, such as nucleic acids and proteins, facilitating intercellular communication and regulating the gene expression profile in target cells. EVs have the potential to be used as biomarkers in diagnosis, prognosis and also as feasible therapeutic targets. The available evidence suggests that exosomes play critical roles in the reproductive system, particularly during implantation, which is widely recognized as a crucial step in early pregnancy. A proper molecular dialogue between a high-quality embryo and a receptive endometrium is essential for the establishment of a normal pregnancy. This review focuses on the key role of exosomes originated from various sources, including the embryo, seminal fluid, and uterus fluid, based on the available evidence. It explores their potential applications as a novel approach in assisted reproductive technologies (ART).

Roles of immune microenvironment in the female reproductive maintenance and regulation: novel insights into the crosstalk of immune cells

Female fertility decline is an accumulative consequence caused by complex factors, among them, the disruption of the immune profile in female reproduction stands out as a crucial contributor. Presently, the effects of immune microenvironment (IME) on the female reproductive process have attracted increasing attentions for their dynamic but precisive roles. Immunocytes including macrophages, dendritic cells, T cells, B cells and neutrophils, with diverse subpopulations as well as high plasticity functioned dynamically in the process of female reproduction through indirect intercellular communication via specific cytokine release transduced by molecular signal networks or direct cell-cell contact to maintain the stability of the reproductive process have been unveiled. The immune profile of female reproduction in each stage has also been meticulously unveiled. Especially, the application of single-cell sequencing (scRNA-seq) technology in this process reveals the distribution map of immune cells, which gives a novel insight for the homeostasis of IME and provides a research direction for better exploring the role of immune cells in female reproduction. Here, we provide an all-encompassing overview of the latest advancements in immune modulation within the context of the female reproductive process. Our approach involves structuring our summary in accordance with the physiological sequence encompassing gonadogenesis, folliculogenesis within the ovaries, ovulation through the fallopian tubes, and the subsequent stages of embryo implantation and development within the uterus. Our overarching objective is to construct a comprehensive portrayal of the immune microenvironment (IME), thereby accentuating the pivotal role played by immune cells in governing the intricate female reproductive journey. Additionally, we emphasize the pressing need for heightened attention directed towards strategies that focus on immune interventions within the female reproductive process, with the ultimate aim of enhancing female fertility.

Association of parental HLA-G polymorphisms with soluble HLA-G expressions and their roles on recurrent implantation failure: A systematic review and meta-analysis

Introduction

HLA-G plays a central role in immune tolerance at the maternal-fetal interface. The HLA-G gene is characterized by low allelic polymorphism and restricted tissue expression compared with classical HLA genes. HLA-G polymorphism is associated with HLA-G expression and linked to pregnancy complications. However, the association of parental HLA-G polymorphisms with soluble HLA-G (sHLA-G) expression and their roles in recurrent implantation failure (RIF) is unclear. The study aims to systematically review the association of HLA-G polymorphisms with RIF, the association of sHLA-G expression with RIF, and the association of HLA-G polymorphisms with sHLA-G expressions in patients attending in-vitro fertilization (IVF) treatment.

Methods

Studies that evaluated the association of HLA-G polymorphisms with RIF, the association between sHLA-G expression with RIF, and the association between HLA-G polymorphisms with sHLA-G expressions in patients attending IVF treatment were included. Meta-analysis was performed by random-effect models. Sensitivity analysis was performed by excluding one study each time. Subgroup analysis was performed based on ethnicity.

Results

HLA-G 14bp ins variant is associated with a lower expression of sHLA-G in seminal or blood plasma of couples attending IVF treatment. The maternal HLA-G*010101 and paternal HLA-G*010102 alleles are associated with RIF risk compared to other alleles. However, single maternal HLA-G 14bp ins/del polymorphism, HLA-G -725 C>G/T polymorphism, or circulating sHLA-G concentration was not significantly associated with RIF in the general population. HLA-G 14bp ins/ins homozygous genotype or ins variant was associated with a higher risk of RIF in the Caucasian population.

Discussion

Specific HLA-G alleles or HLA-G polymorphisms are associated with sHLA-G expression in couples attending IVF treatment. Several HLA-G polymorphisms may be related to RIF, considering different ethnic backgrounds. A combined genetic effect should be considered in future studies to confirm the association of HLA-G polymorphisms and sHLA-G expressions in relation to RIF.

The impact of soluble HLA-G in IVF/ICSI embryo culture medium on implantation success

The HLA-G molecule is widely accepted as an important factor for pregnancy success. Its expression has been detected in the extravillous trophoblasts. Soluble HLA-G (sHLA-G) was found in the genital tract, pre-implanted embryos as well as in seminal fluid. In this study, we investigated the concentration of sHLA-G (sHLA-G1 and sHLA-G5) in media from 344 single cultured embryos following in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI). The level of sHLA-G (U/ml) was tested with a sandwich enzyme-linked immunosorbent assay (ELISA) kit. We correlated sHLA-G secretion with ovarian stimulation protocols, the type of embryo transfer (fresh or frozen cycle) and the quality of the embryos. The ovarian stimulation protocol affects the secretion of sHLA-G by the embryo. Embryos obtained from the long agonist protocol secreted more sHLA-G than those originating from the short antagonist protocol (p = 0.0001). Embryos whose transfer resulted in a clinical pregnancy and/or live birth secreted more sHLA-G compared to those whose transfer ended without pregnancy. This was particularly observable in embryos following the long ovarian stimulation protocol and from a frozen embryo cycle. In conclusion, sHLA-G secreted by the embryo has an impact on implantation and live birth and could be a developmental potential marker of the embryo. Its concentration depends on the ovarian stimulation protocol used.

Immunity at maternal-fetal interface: KIR/HLA (Allo)recognition

Both KIR and HLA are the most variable gene families in the human genome. The recognition of the semi-allogeneic embryo-derived trophoblasts by maternal decidual NK (dNK) cells is essential for the establishment of the functional placenta. This recognition is based on the KIR-HLA interactions and trophoblast expresses a specific HLA profile that constitutes classical polymorphic HLA-C and non-classical oligomorphic HLA-E, HLA-F, and HLA-G molecules. This review highlights some features of the KIR/HLA-C (allo)recognition by decidual NK (dNK) cells as a main immune cell population specifically enriched at maternal-fetal interface during human early pregnancy. How KIR/HLA-C axis operates in pregnancy disorders and in the context of transplacental infections is discussed as well. We summarized old and new data on dNK-cell functional plasticity, their selective expression of KIR and fetal maternal/paternal HLA-C haplotypes present. Results showed that KIR-HLA-C combinations and the corresponding axis operate differently in each pregnancy, determined by the variability of both maternal KIR haplotypes and fetus' maternal/paternal HLA-C allotype combinations. Moreover, the maturation of NK cells strongly depends on if or not HLA allotypes for certain KIR are present. We suggest that the unique KIR/HLA combinations reached in each pregnancy (normal and pathological) should be studied according to well-defined guidelines and unified methodologies to have comparable results ease to interpret and use in clinics.

The Association of HLA-G Gene Polymorphism and Its Soluble Form With Male Infertility

Successful reproduction depends on many factors. Male factors contribute to infertility in approximately 50% of couples who fail to conceive. Seminal plasma consists of secretions from different accessory glands containing a mixture of various cytokines, chemokines, and growth factors, which together can induce a local immune response that might impact on a male’s as well as a female’s fertility. Human leukocyte antigen (HLA)-G expression has been suggested as an immunomodulatory molecule that influences pregnancy outcome. The HLA-G gene encodes either membrane-bound or/and soluble proteins. The aim of this study was the evaluation of HLA-G polymorphisms and their impact on soluble HLA-G (sHLA-G) production. We tested the HLA-G polymorphism in three positions: rs1632947: c.-964G>A; rs1233334: c.-725G>C/T in the promoter region; rs371194629: c.∗65_∗66insATTTGTTCATGCCT in the 3′ untranslated region. We tested two cohorts of men: 663 who participated in in vitro fertilization (test material was blood or sperm), and 320 fertile controls who possessed children born after natural conception (test material was blood). Since 50% of men visiting assisted reproductive clinics have abnormal semen parameters, we wondered if men with normal sperm parameters differ from those with abnormal parameters in terms of HLA-G polymorphism and secretion of sHLA-G into semen. We found that certain rs1632947-rs1233334-rs371194629 HLA-G haplotypes and diplotypes were associated with male infertility, while others were protective. Normozoospermic men with the A-C-del haplotype and A-C-del/A-C-del diplotype secreted the most sHLA-G into semen (574.1 IU/mL and 1047.0 IU/mL, respectively), while those with the G-C-ins haplotype and G-C-ins/G-C-ins diplotype – the least (80.8 IU/mL and 75.7 IU/mL, respectively). Men with the remaining haplotypes/diplotypes secreted sHLA-G at an intermediate level. However, only in one haplotype, namely G-C-ins, did we observe strong significant differences in the concentration of sHLA-G in the semen of men with teratozoospermia compared to men with normal sperm parameters (p = 0.009). In conclusion, fertile men differ in the profile of HLA-G polymorphism from men participating in IVF. Among all HLA-G haplotypes, the most unfavorable for male fertility is the G-C-ins haplotype, which determines the secretion of the lowest concentration of the soluble HLA-G molecule. This haplotype may reduce sperm parameters.

HLA-G: An Important Mediator of Maternal-Fetal Immune-Tolerance

Maternal-fetal immune-tolerance occurs throughout the whole gestational trimester, thus a mother can accept a genetically distinct fetus without immunological aggressive behavior. HLA-G, one of the non-classical HLA class I molecules, is restricted-expression at extravillous trophoblast. It can concordantly interact with various kinds of receptors mounted on maternally immune cells residing in the uterus (e.g. CD4+ T cells, CD8+ T cells, natural killer cells, macrophages, and dendritic cells) for maintaining immune homeostasis of the maternal-fetus interface. HLA-G is widely regarded as the pivotal protective factor for successful pregnancies. In the past 20 years, researches associated with HLA-G have been continually published. Indeed, HLA-G plays a mysterious role in the mechanism of maternal-fetal immune-tolerance. It can also be ectopically expressed on tumor cells, infected sites and other pathologic microenvironments to confer a significant local tolerance. Understanding the characteristics of HLA-G in immunologic tolerance is not only beneficial for pathological pregnancy, but also helpful to the therapy of other immune-related diseases, such as organ transplant rejection, tumor migration, and autoimmune disease. In this review, we describe the biological properties of HLA-G, then summarize our understanding of the mechanisms of fetomaternal immunologic tolerance and the difference from transplant tolerance. Furthermore, we will discuss how HLA-G contributes to the tolerogenic microenvironment during pregnancy. Finally, we hope to find some new aspects of HLA-G in fundamental research or clinical application for the future.

Soluble human leukocyte antigen-G is a potential embryo viability biomarker and a positive predictor of live-births in humans

PROBLEM

Human infertility affects 15-20% of reproductive-age couples and it is mitigated by assisted reproductive technology (ART) approaches. Poor biological viability of embryos contributes to implantation failure and live birth rate (LBR). This study is aimed to examine whether or not embryo-secreted soluble human leukocyte antigen-G (sHLA-G) is (i) associated with developing embryos and (ii) able to predict successful pregnancy outcome.

METHOD OF STUDY

A retrospective, multicentric study using 539 human embryo spent medium samples (E-SMs), analysed for sHLA-G levels by ELISA. Correlation analysis was performed on sHLA-G levels with developing embryonic stages, their quality scores and pregnancy outcome in terms of LBR.

RESULTS

Of 539 E-SMs analysed, 445 had detectable sHLA-G (83%) with levels varying within and across clinics and, between stages of embryonic development. Levels of sHLA-G (ng/mL) were significantly (P < .05) different in E-SMs of cleavage-stage embryos versus blastocysts. There was an insignificant correlation between the sHLA-G levels and morphology scores of embryos. But, sHLA-G levels showed a positive correlation with grades of blastocysts and importantly, its levels were significantly (P < .05) higher in live-birth vis-a-vis no-birth cases. Also, levels were higher in live-births out of blastocysts-ETs versus cleavage-stage-embryo transfers. Altered levels were observed with embryos, which resulted in miscarriages. Overall, a significant (P < .0001) association of sHLA-G with live births was observed.

CONCLUSION

Embryo-derived sHLA-G can be a valuable embryo viability, independent, biomarker, which can predict live-birth outcome and it could be useful as an adjunct to existing criteria for elective single embryo transfer.

Specific and Aspecific Molecular Checkpoints as Potential Targets for Dismantling Tumor Hierarchy and Preventing Relapse and Metastasis Through Shielded Cytolytic Treatments

I have recently theorized that several similarities exist between the tumor process and embryo development. Starting from an initial cancer stem cell (CSC0), similar to an embryonic stem cell (ESC), after implantation in a niche, primary self-renewing CSCs (CSC1s) would arise, which then generate secondary proliferating CSCs (CSC2s). From these epithelial CSCs, tertiary mesenchymal CSCs (CSC3s) would arise, which, under favorable stereotrophic conditions, by asymmetric proliferation, would generate cancer progenitor cells (CPCs) and then cancer differentiated cells (CDCs), thus giving a defined cell heterogeneity and hierarchy. CSC1s-CSC2s-CSC3s-CPCs-CDCs would constitute a defined "tumor growth module," able to generate new tumor modules, forming a spherical avascular mass, similar to a tumor sphere. Further growth in situ of this initial tumor would require implantation in the host and vascularization through the overexpression of some aspecific checkpoint molecules, such as CD44, ID, LIF, HSP70, and HLA-G. To expand and spread in the host tissues, this vascularized tumor would then carry on a real growth strategy based on other specific checkpoint factors, such as those contained in the extracellular vesicles (EVs), namely, microRNAs, messenger RNAs, long non-coding RNAs, and integrins. These EV components would be crucial in tumor progression because they can mediate intercellular communications in the surrounding microenvironment and systemically, dictating to recipient cells a new tumor-enslaved phenotype, thus determining pre-metastatic conditions. Moreover, by their induction properties, the EV contents could also frustrate in time the effects of cytolytic tumor therapies, where EVs released by killed CSCs might enter other cancer and non-cancer cells, thus giving chemoresistance, non-CSC/CSC transition (recurrence), and metastasis. Thus, antitumor cytotoxic treatments, "shielded" from the EV-specific checkpoints by suitable adjuvant agents, simultaneously targeting the aforesaid aspecific checkpoints should be necessary for dismantling the hierarchic tumor structure, avoiding recurrence and preventing metastasis.

Effect of bisphenol A on alterations of ICAM-1 and HLA-G genes expression and DNA methylation profiles in cumulus cells of infertile women with poor response to ovarian stimulation

This study aimed to investigate the relationship between follicular fluid Bisphenol A (BPA) concentrations with alterations of ICAM-1 and HLA-G genes and proteins expression as well as methylation profiles in the cumulus cells of poor ovarian response (POR) women based on their healthy lifestyle habit. Eighty women under the age of 35 were divided into two groups: 1-POR without using plastic containers (n = 40) and 2-POR with using plastic containers (n = 40). The ICAM-1 and HLA-G genes and protein expressions were examined by the quantitative PCR and western blotting technique. The methylation pattern was investigated by the methylation-specific PCR. Total BPA in follicular fluid was measured with high-performance liquid chromatography technique and the detection limit was 1.14 ng/ml. ICAM-1 and HLA-G genes were differentially expressed between the two groups studied. ICAM-1, HLA-G genes, and protein expressions in group 1 were up-regulated compared to the second group (P < 0.05). While DNA methylation status in group 1 were decreased compared to the other group (P < 0.05). The concentration of BPA in the follicular fluid of group 1 was lower compared to the second group (P < 0.05). The oocyte quality and clinical pregnancy ratio showed significantly higher in group 1 than in the other ones (P < 0.05). The alteration of ICAM-1 and HLA-G gene expressions in POR women is probably related to BPA concentration. As a result Lifestyle habits may also affect the methylation pattern and protein levels in the cumulus cells of POR women. Additionally, lifestyle habits may be considered as a marker for ovulation, oocyte maturation, preimplantation, and clinical pregnancy process.

Cytokines in embryonic secretome as potential markers for embryo selection

Despite performing certain morphological assessments for selecting the best embryo for transfer, the results have not been satisfactory. Given the global tendency for performing quick and noninvasive tests for embryo selection, great efforts have been made to discover the predictive biomarkers of embryo implantation potential. In recent years, many factors have been detected in embryo culture media as a major source of embryo secretions. Previous studies have evaluated cytokines, miRNAs, extracellular vesicles, and other factors such as leukemia inhibitory factor, colony-stimulating factor, reactive oxygen species, soluble human leukocyte antigen G, amino acids, and apolipoproteins in these media. Given the key role of cytokines in embryo implantation, these factors can be considered promising molecules for predicting the implantation success of assisted reproductive technology (ART). The present study was conducted to review embryo-secreted molecules as potential biomarkers for embryo selection in ART.

Roles of HLA-G in the Maternal-Fetal Immune Microenvironment

During pregnancy, the maternal uterus and fetus form a special microenvironment at the maternal-fetal interface to support fetal development. Extravillous trophoblasts (EVTs), differentiated from the fetus, invade into the decidua and interact with maternal cells. Human leukocyte antigen (HLA)-G is a non-classical MHC-I molecule that is expressed abundantly and specifically on EVTs in physiological conditions. Soluble HLA-G (sHLA-G) is also found in maternal blood, amniotic fluid, and cord blood. The abnormal expression and polymorphisms of HLA-G are related to adverse pregnancy outcomes such as preeclampsia (PE) and recurrent spontaneous abortion (RSA). Here we summarize current findings about three main roles of HLA-G during pregnancy, namely its promotion of spiral artery remodeling, immune tolerance, and fetal growth, all resulting from its interaction with immune cells. These findings are not only of great significance for the treatment of pregnancy-related diseases but also provide clues to tumor immunology research since HLA-G functions as a checkpoint in tumors.

HLA-G Expression in Human Mesenchymal Stem Cells (MSCs) Is Related to Unique Methylation Pattern in the Proximal Promoter as well as Gene Body DNA

Multipotent human mesenchymal stem cells (MSCs) harbor clinically relevant immunomodulation, and HLA-G, a non-classical MHC class I molecule with highly restricted tissue expression, is one important molecule involved in these processes. Understanding of the natural regulatory mechanisms involved in expression of this elusive molecule has been difficult, with near exclusive reliance on cancer cell lines. We therefore studied the transcriptional control of HLA-G in primary isolated human bone marrow- (BM), human embryonic stem cell-derived (hE-), as well as placenta-derived MSCs (P-MSCs), and found that all 3 types of MSCs express 3 of the 7 HLA-G isoforms at the gene level; however, fibroblasts did not express HLA-G. Protein validation using BM- and P-MSCs demonstrated expression of 2 isoforms including a larger HLA-G-like protein. Interferon-γ (IFN-γ) stimulation upregulated both gene and protein expression in MSCs but not the constitutively expressing JEG-3 cell line. Most interestingly in human MSCs and placental tissue, hypomethylation of CpG islands not only occurs on the HLA-G proximal promoter but also on the gene body as well, a pattern not seen in either of the 2 commonly used choriocarcinoma cell lines which may contribute to the unique HLA-G expression patterns and IFN-γ-responsiveness in MSCs. Our study implicates the importance of using normal cells and tissues for physiologic understanding of tissue-specific transcriptional regulation, and highlight the utility of human MSCs in unraveling the transcriptional regulation of HLA-G for better therapeutic application.

A long road/read to rapid high-resolution HLA typing: The nanopore perspective

Next-generation sequencing (NGS) has been widely adopted for clinical HLA typing and advanced immunogenetics researches. Current methodologies still face challenges in resolving cis-trans ambiguity involving distant variant positions, and the turnaround time is affected by testing volume and batching. Nanopore sequencing may become a promising addition to the existing options for HLA typing. The technology delivered by the MinION sequencer of Oxford Nanopore Technologies (ONT) can record the ionic current changes during the translocation of DNA/RNA strands through transmembrane pores and translate the signals to sequence reads. It features simple and flexible library preparations, long sequencing reads, portable and affordable sequencing devices, and rapid, real-time sequencing. However, the error rate of the sequencing reads is high and remains a hurdle for its broad application. This review article will provide a brief overview of this technology and then focus on the opportunities and challenges of using nanopore sequencing for high-resolution HLA typing and immunogenetics research.

HLA-G as a new tumor biomarker: detection of soluble isoforms of HLA-G in the serum and saliva of patients with colorectal cancer

INTRODUCTION

Recent medical investigations suggest that HLA-G, due to its tolerogenic properties, can be used as a biomarker in the diagnosis, treatment, and prognosis of different neoplasms. This observational prospective pilot study aims at detecting sHLA-G in the serum and saliva of patients diagnosed with colorectal cancer (CRC). For this purpose, we compared the expression of sHLA-G from patients with a control sample from a healthy population.

MATERIALS AND METHODS

Using the specific enzyme-linked immunosorbent assay (ELISA) method, the expression of sHLA-G in the serum and saliva samples from patients affected by CRC (n = 20) and in a control sample (n = 10) were analyzed.

RESULTS

The data showed that in patients with CRC, salivary sHLA-G values were significantly higher than in the control group (18.84 U/ml versus 6.3 U/ml, p = 0.036). In addition, higher levels of sHLA-G were observed in the saliva of patients with CRC in more advanced stages, compared with patients in early stages (24.2 U/ml vs. 8.1 U/ml, p = 0.019). A significant correlation was observed between the concentration of sHLA-G in the serum and saliva of the analyzed samples (Spearman correlation 0.7, p = 0.004).

CONCLUSIONS

This study demonstrates, for the first time, the possibility of detecting sHLA-G in the saliva of patients with CRC, resulting in a less invasive alternative to venipuncture. Likewise, we propose that sHLA-G could be an attractive molecular target based on its significant high levels in advanced stages.

Similarities Between Embryo Development and Cancer Process Suggest New Strategies for Research and Therapy of Tumors: A New Point of View

Here, I propose that cancer stem cells (CSCs) would be equivalent to para-embryonic stem cells (p-ESCs), derived from adult cells de-re-programmed to a ground state. p-ESCs would differ from ESCs by the absence of genomic homeostasis. A p-ESC would constitute the cancer cell of origin (i-CSC or CSC0), capable of generating an initial tumor, corresponding to a pre-implantation blastocyst. In a niche with proper signals, it would engraft as a primary tumor, corresponding to a post-implantation blastocyst. i-CSC progeny would form primary pluripotent and slow self-renewing CSCs (CSC1s), blocked in an undifferentiated state, corresponding to epiblast cells; CSC1s would be tumor-initiating cells (TICs). CSC1s would generate secondary CSCs (CSC2s), corresponding to hypoblast cells; CSC2s would be tumor growth cells (TGCs). CSC1s/CSC2s would generate tertiary CSCs (CSC3s), with a mesenchymal phenotype; CSC3s would be tumor migrating cells (TMCs), corresponding to mesodermal precursors at primitive streak. CSC3s with more favorable conditions (normoxia), by asymmetrical division, would differentiate into cancer progenitor cells (CPCs), and these into cancer differentiated cells (CDCs), thus generating a defined cell hierarchy and tumor progression, mimicking somito-histo-organogenesis. CSC3s with less favorable conditions (hypoxia) would delaminate and migrate as quiescent circulating micro-metastases, mimicking mesenchymal cells in gastrula morphogenetic movements. In metastatic niches, these CSC3s would install and remain dormant in the presence of epithelial/mesenchymal transition (EMT) signals and hypoxia. But, in the presence of mesenchymal/epithelial transition (MET) signals and normoxia, they would revert to self-renewing CSC1s, reproducing the same cell hierarchy of the primary tumor as macro-metastases. Further similarities between ontogenesis and oncogenesis involving crucial factors, such as ID, HSP70, HLA-G, CD44, LIF, and STAT3, are strongly evident at molecular, physiological and immunological levels. Much experimental data about these factors led to considering the cancer process as ectopic rudimentary ontogenesis, where CSCs have privileged immunological conditions. These would consent to CSC development in an adverse environment, just like an embryo, which is tolerated, accepted and favored by the maternal organism in spite of its paternal semi-allogeneicity. From all these considerations, novel research directions, potential innovative tumor therapy and prophylaxis strategies might, theoretically, result.

Secretome of in vitro cultured human embryos contains extracellular vesicles that are uptaken by the maternal side

Communication between embryo and maternal endometrium occurs during a specific time frame in which implantation is possible. Here we demonstrate for the first time that conditioned media from non-manipulated human embryos cultured in vitro for 3 days or up to the blastocyst stage contain extracellular vesicles (EVs) with a diameter of 50 to 200 nm and bearing the traditional microvesicle and exosome marker proteins CD63, CD9 and ALIX. The embryonic origin of these EVs has been confirmed by the presence of stemness gene transcripts and their enrichment in the non-classical HLA-G protein. NANOG and POU5F1 transcripts were shown to be contained in vesicles deriving from embryos at different stages of development. In line with a higher detection rate of the HLA-G protein in blastocysts compared to cleavage stage embryos, a significantly higher amount of HLA-G was found in vesicles accumulated in spent media from day 3 to day 5 of development compared to those isolated from the earlier stage. Uptake of dye-labeled embryo-derived EVs by human primary endometrial epithelial and stromal cells was also demonstrated with a fluorescence intensity signal significantly higher for cells treated with vesicles derived from blastocysts. Based on these findings, EV exchange may be suggested as an emerging way of communication at the maternal-fetal interface.

Bronchial Epithelial Cells from Asthmatic Patients Display Less Functional HLA-G Isoform Expression

Not all asthmatic patients adequately respond to current available treatments, such as inhaled corticosteroids or omalizumab^®. New treatments will aim to target the bronchial epithelium-immune response interaction using different pathways. HLA-G is involved in immunomodulation and may promote epithelial cell differentiation and proliferation. HLA-G protein has several isoforms generated by alternative splicing that might have differential functionalities. HLA-G protein expression and genetic polymorphisms have been reported to be associated with asthma. Our hypothesis is that bronchial epithelium from asthmatic patients displays less functional HLA-G isoforms. HLA-G transcriptional isoforms were quantified by real-time PCR in human bronchial epithelium cells (HBEC) grown in air-liquid interface culture obtained from five healthy controls (HC), seven patients with mild asthma (MA), and seven patients with severe asthma (SA). They were re-differentiated, and IL-13 exposure was used as a proxy for a pro-inflammatory cytokine. HLA-G protein expression was assessed by western blot analysis. HLA-G allele was typed by direct sequencing. Our results showed that both MA and SA display less functional HLA-G isoforms than HC (p < 0.05); in vitro HBEC re-differentiation from SA displays a particular isoform expression profile compared to MA and HC (p = 0.03); HLA-G*01:06 frequency in MA and SA was significantly higher than in the healthy population (p = 0.03 and p < 0.001, respectively); and IL-13 exposure had no impact on HLA-G expression. Our results support that an impaired expression of HLA-G isoforms in asthmatic patients could contribute to the loss of inflammation control and epithelium structural remodeling. Therefore, HLA-G might be an interesting alternative target for asthmatic patients not adequately responding to current drugs.

Pseudomonas aeruginosa Quorum Sensing Molecule N-(3-Oxododecanoyl)-L-Homoserine-Lactone Induces HLA-G Expression in Human Immune Cells

HLA-G is a nonclassical class I human leukocyte antigen (HLA) involved in mechanisms of immune tolerance. The objective of this study was to determine whether N-(3-oxododecanoyl)-l-homoserine lactone (3O-C12-HSL), a quorum sensing molecule produced by Pseudomonas aeruginosa, could modify HLA-G expression to control the host immune response. We evaluated the ability of 3O-C12-HSL to induce HLA-G expression in primary immune cells, monocytes (U937 and THP1), and T-cell lines (Jurkat) in vitro and analyzed the cellular pathway responsible for HLA-G expression. We studied the HLA-G promoter with a luciferase assay and interleukin-10 (IL-10) and p38/CREB signaling with enzyme-linked immunosorbent assay and immunofluorescence, respectively. We observed that 3O-C12-HSL is able to induce HLA-G expression in human monocytes and T cells. We showed that the induction of HLA-G by 3O-C12-HSL is p38/CREB and IL-10 dependent. 3O-C12-HSL treatment is able to arrest only the U937 cell cycle, possibly due to the peculiar expression of the ILT2 receptor in the U937 cell line. Our observations suggest HLA-G as a mechanism to create a protected niche for the bacterial reservoir, similar to the role of HLA-G molecules during viral infections.

Soluble ligands and their receptors in human embryo development and implantation

Extensive evidence suggests that soluble ligands and their receptors mediate human preimplantation embryo development and implantation. Progress in this complex area has been ongoing since the 1980s, with an ever-increasing list of candidates. This article specifically reviews evidence of soluble ligands and their receptors in the human preimplantation stage embryo and female reproductive tract. The focus will be on candidates produced by the human preimplantation embryo and those eliciting developmental responses in vitro, as well as endometrial factors related to implantation and receptivity. Pathways to clinical translation, including innovative diagnostics and other technologies, are also highlighted, drawing from this collective evidence toward facilitating joint improvements in embryo quality and endometrial receptivity. This strategy could not only benefit clinical outcomes in reproductive medicine but also provide broader insights into the peri-implantation period of human development to improve fetal and neonatal health.

OMICS: Current and future perspectives in reproductive medicine and technology

Many couples present fertility problems at their reproductive age, and although in the last years, the efficiency of assisted reproduction techniques has increased, these are still far from being 100% effective. A key issue in this field is the proper assessment of germ cells, embryos and endometrium quality, in order to determine the actual likelihood to succeed. Currently available analysis is mainly based on morphological features of oocytes, sperm and embryos and although these strategies have improved the results, there is an urgent need of new diagnostic and therapeutic tools. The emergence of the - OMICS technologies (epigenomics, genomics, transcriptomics, proteomics and metabolomics) permitted the improvement on the knowledge in this field, by providing with a huge amount of information regarding the biological processes involved in reproductive success, thereby getting a broader view of complex biological systems with a relatively low cost and effort.

HLA-G as a tolerogenic molecule in transplantation and pregnancy

HLA-G is a nonclassical HLA class I molecule. In allogeneic situations such as pregnancy or allograft transplantation, the expression of HLA-G has been related to a better acceptance of the fetus or the allograft. Thus, it seems that HLA-G is crucially involved in mechanisms shaping an allogeneic immune response into tolerance. In this contribution we focus on (i) how HLA-G is involved in transplantation and human reproduction, (ii) how HLA-G is regulated by genetic and microenvironmental factors, and (iii) how HLA-G can offer novel perspectives with respect to therapy.

Expression and potential roles of HLA-G in human spermatogenesis and early embryonic development

As one of the non-classical major histocompatibility complex(MHC)-1 antigens, Human Leukocyte Antigen G (HLA-G), has been suggested as a prognostic marker to identify the embryo developmental potential. In the present study, we investigated the potential roles of HLA-G in human spermatogenesis and early embryonic development. Quantitative real-time PCR analysis revealed that HLA-G's expression was increased with increased Johnsen score in testicular tissues. There was no significant difference in HLA-G mRNA expression between testicular tissues with Johnsen score of 8–9 and normal sperm from ejaculated semen. HLA-G mRNA expression was detected in human zygotes, embryos and blastocysts but not in unfertilized oocytes. In testicular tissues where sperm was obtained by testicular sperm extraction (Johnsen score was 8 to 9), there were no correlations between HLA-G mRNA expression and fertilization, cleavage and high-quality embryo rates. At 48–72 h post-fertilization, HLA-G expression was higher in fast growing embryos. HLA-G specific siRNA injection into zygotes not only slowed down embryonic cleavage rate at 48 h post-fertilization, but also down-regulated the expression of embryo metabolism related gene (SLC2A1) and cell cycle-regulated gene (CCND2). Taken together, our findings suggested that HLA-G plays significant roles in human spermatogenesis and early embryonic development.

Soluble human leukocyte antigen-g5 activates extracellular signal-regulated protein kinase signaling and stimulates trophoblast invasion

Soluble human leukocyte antigen-G (HLA-G) is a non-classical class Ib HLA molecule that is secreted from blastocysts. Soluble HLA-G modulates the immune tolerance of the mother and can be used as a prognostic factor for the clinical pregnancy rate. However, the underlying mechanism of how soluble HLA-G5 affects pregnancy remains largely unknown. We hypothesized that soluble HLA-G5 promotes successful implantation and pregnancy by modulating trophoblast invasion through receptor binding and activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Recombinant HLA-G5 protein over-expressed in E. coli BL21 was purified to near homogeneity. We studied the expression of HLA-G5 and its receptors, the leukocyte immunoglobulin-like receptor subfamily B1 (LILRB1) and killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), in primary trophoblasts and trophoblastic (JAr and JEG-3) cell lines by florescence-labeled HLA-G5. HLA-G5 was detected in the primary trophoblasts and JEG-3 cells. The LILRB1 and KIR2DL4 receptors were expressed in both primary trophoblasts and trophoblastic cell lines. HLA-G5 stimulated cell invasion (p<0.05) and increased urokinase (uPA) and matrix metalloproteinases (MMPs) transcripts and their activity (p<0.05) in trophoblastic cells. HLA-G5 activated the ERK signaling pathway and induced ERK1/2 phosphorylation in the trophoblastic cell lines. Addition of ERK inhibitors (U0126 and PD98059) nullified the stimulatory effect of HLA-G5 on trophoblastic cell invasion. Taken together, HLA-G5 induced trophoblast invasion by binding to KIR2DL4 and LILRB1, by increasing uPA and MMPs expressions and by activating the ERK signaling pathway.

Quantified colocalization reveals heterotypic histocompatibility class I antigen associations on trophoblast cell membranes: relevance for human pregnancy

Human placental syncytiotrophoblasts lack expression of most types of human leukocyte antigen (HLA) class I and class II molecules; this is thought to contribute to a successful pregnancy. However, the HLA class Ib antigens HLA-G, -E, and -F and the HLA class Ia antigen HLA-C are selectively expressed on extravillous trophoblast cells, and they are thought to play a major role in controlling feto-maternal tolerance. We have hypothesized that selective expression, coupled with the preferential physical association of pairs of HLA molecules, contribute to the function of HLA at the feto-maternal interface and the maternal recognition of the fetus. We have developed a unique analytical model that allows detection and quantification of the heterotypic physical associations of HLA class I molecules expressed on the membrane of human trophoblast choriocarcinoma cells, ACH-3P and JEG-3. Automated image analysis was used to estimate the degree of overlap of HLA molecules labeled with different fluorochromes. This approach yields an accurate measurement of the degree of colocalization. In both JEG-3 and ACH-3P cells, HLA-C, -E, and -G were detected on the cell membrane, while the expression of HLA-F was restricted to the cytoplasm. Progesterone treatment alone induced a significant increase in the expression level of the HLA-G/HLA-E association, suggesting that this heterotypic association is modulated by this hormone. Our data shows that the cell-surface HLA class I molecules HLA-G, -E, and -C colocalize with each other and have the potential to form preferential heterotypic associations.

HLA-G regulates the invasive properties of JEG-3 choriocarcinoma cells by controlling STAT3 activation

The expression of human leucocyte antigen-G (HLA-G) in trophoblasts plays a crucial role in successful embryonic implantation, and reduced HLA-G expression might contribute to adverse obstetric outcomes. In this study, we silenced HLA-G expression using RNA interference in JEG-3 cells, resulting in a notably attenuated invasion capacity of the cells in a Transwell assay; however, no alterations in cell proliferation or apoptosis were observed. The down-regulation of HLA-G dampened the activation of signal transducer and activator of transcription 3 (STAT3), whereas the up-regulation of HLA-G promoted STAT3 activation and invasion in JEG-3 cells treated with human galectin-1. Most importantly, interleukin-6 (IL-6), but not galectin-1, was shown to rescue invasion deficiency in a dose-dependent manner. Thus, we demonstrate that HLA-G is able to regulate JEG-3 cell invasion by influencing STAT3 activation, which may underlie the implantation defects accompanying HLA-G hypo-expression in pre-eclampsia.

Matrix metalloproteinase-2 (MMP-2) generates soluble HLA-G1 by cell surface proteolytic shedding

Human leukocyte antigen-G (HLA-G) molecules are non-classical HLA class I antigens with an important role in pregnancy immune regulation and inflammation control. Soluble HLA-G proteins can be generated through two mechanisms: alternative splicing and proteolytic release, which is known to be metalloprotease mediated. Among this class of enzymes, matrix metalloproteinases (MMPs) might be involved in the HLA-G1 membrane cleavage. Of particular interest are MMP-2 and MMP-9, which regulate the inflammatory process by cytokine and chemokine modulation. We evaluated the effect of MMP-9 and MMP-2 on HLA-G1 membrane shedding. In particular, we analyzed the in vitro effect of these two gelatinases on the secretion of HLA-G1 via proteolytic cleavage in 221-G1-transfected cell line, in JEG3 cell line, and in peripheral blood mononuclear cells. The results obtained by both cell lines showed the role of MMP-2 in HLA-G1 shedding. On the contrary, MMP-9 was not involved in this process. In addition, we identified three possible highly specific cleavage sites for MMP-2, whereas none were detected for MMP-9. This study suggests an effective link between MMP-2 and HLA-G1 shedding, increasing our knowledge on the regulatory machinery beyond HLA-G regulation in physiological and pathological conditions.

Galectin-1 influences trophoblast immune evasion and emerges as a predictive factor for the outcome of pregnancy

Galectin-1 (gal-1) is expressed at the feto-maternal interface and plays a role in regulating the maternal immune response against placental alloantigens, contributing to pregnancy maintenance. Both decidua and placenta contribute to gal-1 expression and may be important for the maternal immune regulation. The expression of gal-1 within the placenta is considered relevant to cell-adhesion and invasion of trophoblasts, but the role of gal-1 in the immune evasion machinery exhibited by trophoblast cells remains to be elucidated. In this study, we analyzed gal-1 expression in preimplantation human embryos and first-trimester decidua-placenta specimens and serum gal-1 levels to investigate the physiological role played by this lectin during pregnancy. The effect on human leukocyte antigen G (HLA-G) expression in response to stimulation or silencing of gal-1 was also determined in the human invasive, proliferative extravillous cytotrophoblast 65 (HIPEC65) cell line. Compared with normal pregnant women, circulating gal-1 levels were significantly decreased in patients who subsequently suffered a miscarriage. Human embryos undergoing preimplantation development expressed gal-1 on the trophectoderm and inner cell mass. Furthermore, our in vitro experiments showed that exogenous gal-1 positively regulated the membrane-bound HLA-G isoforms (HLA-G1 and G2) in HIPEC65 cells, whereas endogenous gal-1 also induced expression of the soluble isoforms (HLA-G5 and -G6). Our results suggest that gal-1 plays a key role in pregnancy maternal immune regulation by modulating HLA-G expression on trophoblast cells. Circulating gal-1 levels could serve as a predictive factor for pregnancy success in early human gestation.

Evidence that miR-133a causes recurrent spontaneous abortion by reducing HLA-G expression

Human leukocyte antigen (HLA)-G is thought to confer fetal-maternal tolerance and play a crucial role in ensuring a successful pregnancy. There is increasing evidence that HLA-G is regulated at the post-transcriptional level. This study investigated the role of miR-133a in regulating HLA-G expression and the pathogenesis of recurrent spontaneous abortion (RSA). Twelve patients (25-30 years) with RSA at 7 gestational weeks were screened by array-based comparative genome hybridization: 16.7% were found to have an abnormal karyotype and all induced abortion (IA) patients had normal karyotype. The villi of RSA and IA patients with normal karyotype were further screened by miRNA microarrays. Multi-software prediction and real-time PCR confirmed that miR-133a was most likely to bind to HLA-G 3' untranscribed region (UTR). Relevance analysis showed that, compared with IA villi, miR-133a was greatly overexpressed in RSA villi with normal karyotype (P<0.01), but not in abnormal RSA villi. A luciferase reporter assay suggested that miR-133a interacted with HLA-G 3' UTR. Overexpression of miR-133a in JEG-3 cells decreased HLA-G expression at the protein level, with no effect on mRNA. These findings provide strong evidence that miR-133a regulates HLA-G expression by reducing translation and is involved in the pathogenesis of RSA.

The immunosuppressive molecule HLA-G and its clinical implications

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex (MHC) class I molecule that, through interaction with its receptors, exerts important tolerogenic functions. Its main physiological expression occurs in placenta where it seems to participate in the maternal tolerance toward the fetus. HLA-G has been studied as a marker of pregnancy complications such as abortion or pre-eclapmsia. Although HLA-G is not expressed in most adult tissues, its ectopic expression has been observed in some diseases such as viral infections, autoimmune disorders, and especially cancer. HLA-G neo-expression in cancer is associated with the capability of tumor cells to evade the immune control. In this review, we will summarize HLA-G biology and how it participates in these physiopathological processes. Special attention will be paid to its role as a diagnostic tool and also as a therapeutic target.

Pervasive haplotypic variation in the spliceo-transcriptome of the human major histocompatibility complex

The human major histocompatibility complex (MHC) on chromosome 6p21 is a paradigm for genomics, showing remarkable polymorphism and striking association with immune and non-immune diseases. The complex genomic landscape of the MHC, notably strong linkage disequilibrium, has made resolving causal variants very challenging. A promising approach is to investigate gene expression levels considered as tractable intermediate phenotypes in mapping complex diseases. However, how transcription varies across the MHC, notably relative to specific haplotypes, remains unknown. Here, using an original hybrid tiling and splice junction microarray that includes alternate allele probes, we draw the first high-resolution strand-specific transcription map for three common MHC haplotypes (HLA-A1-B8-Cw7-DR3, HLA-A3-B7-Cw7-DR15, and HLA-A26-B18-Cw5-DR3-DQ2) strongly associated with autoimmune diseases including type 1 diabetes, systemic lupus erythematosus, and multiple sclerosis. We find that haplotype-specific differences in gene expression are common across the MHC, affecting 96 genes (46.4%), most significantly the zing finger protein gene ZFP57. Differentially expressed probes are correlated with polymorphisms between haplotypes, consistent with cis effects that we directly demonstrate for ZFP57 in a cohort of healthy volunteers (P = 1.2 × 10(-14)). We establish that alternative splicing is significantly more frequent in the MHC than genome-wide (72.5% vs. 62.1% of genes, P ≤ 1 × 10(-4)) and shows marked haplotypic differences. We also unmask novel and abundant intergenic transcription involving 31% of transcribed blocks identified. Our study reveals that the renowned MHC polymorphism also manifests as transcript diversity, and our novel haplotype-based approach marks a new step toward identification of regulatory variants involved in the control of MHC-associated phenotypes and diseases.

Long-lasting inhibitory effects of fetal liver mesenchymal stem cells on T-lymphocyte proliferation

Human bone marrow mesenchymal stem cells (BM-MSC) are multipotent progenitor cells that have transient immunomodulatory properties on Natural Killer (NK) cells, Dendritic Cells (DC), and T cells. This study compared the use of MSC isolated from bone marrow and fetal liver (FL-MSC) to determine which displayed the most efficient immunosuppressive effects on T cell activation. Although both types of MSC exhibit similar phenotype profile, FL-MSC displays a much more extended in vitro life-span and immunomodulatory properties. When co-cultured with CD3/CD28-stimulated T cells, both BM-MSC and FL-MSC affected T cell proliferation by inhibiting their entry into the cell cycle, by inducing the down-regulation of phospho-retinoblastoma (pRb), cyclins A and D1, as well as up-regulating p27^kip1expression. The T cell inhibition by MSC was not due to the soluble HLA-G5 isoform, but to the surface expression of HLA-G1, as shown by the need of cell-cell contact and by the use of neutralizing anti-HLA-G antibodies. To note, in a HLA-G-mediated fashion, MSC facilitated the expansion of a CD4^low/CD8^low T subset that had decreased secretion of IFN-γ, and an induced secretion of the immunomodulatory cytokine IL-10. Because of their longer lasting in vitro immunosuppressive properties, mainly mediated by HLA-G, and their more efficient induction of IL-10 production and T cell apoptosis, fetal liver MSC could be considered a new tool for MSC therapy to prevent allograft rejection.

Efficient derivation and concise gene expression profiling of human embryonic stem cell-derived mesenchymal progenitors (EMPs)

New potential sources of stem cells for clinical application include bone marrow mesenchymal stem cells (BMMSCs), human embryonic stem cells (hESCs), and induced pluripotent stem cells (iPS). However, each source is not without its own concerns. While research continues in an effort to overcome these problems, the generation of mesenchymal progenitors from existing hESC lines may circumvent many of these issues. We report here a simple and efficient method of generating hESC-derived mesenchymal progenitors (EMPs) and transcriptome profiling using a concise, custom-designed, oligomnucleotide gene expression microarray. Characterization of EMPs shows that these cells are similar to BMMSCs in terms of differentiation capacity as well as cell surface marker expression. In addition, EMPs express several ESC markers and HLA-G, a nonclassical MHC class I molecule with immunomodulatory properties. Morevoer, EMPs possess significantly enhanced proliferative ability over BMMSCs during which karyotypic stability was maintained. Although derived from hESCs, EMPs do not form any tumors in immunocompromised mice. To efficiently profile gene expression in multiple samples, we designed an oligoarray to probe just over 11,000 genes highly expressed in stem cells. We found that the transcriptome of EMPs is more similar to BMMSCs than hESCs. Both cell types highly express genes involved in processes related to the cytoskeleton, extracellular matrix, and cell adhesion, but EMPs show higher expression of genes involved in cell proliferation whereas BMMSCs showed higher expression of immune-related genes. Based on our data, EMPs may be an accessible source of mesenchymal progenitor for therapeutic use.

Evaluation of HLA-G5 plasmatic levels during pregnancy and relationship with the 14-bp polymorphism

PROBLEM

Plasmatic HLA-G levels increase during pregnancy, but the contribution of each different isoform has not been elucidated yet.

METHOD OF STUDY

HLA-G5 was analyzed by ELISA in 19 controls, 79 women in the first 8 weeks of pregnancy and in nine women monthly until delivery. Genotyping for the 14-bp polymorphism was performed by PCR amplification of exon 8.

RESULTS

HLA-G5 was detected in plasma from 80% of pregnant women. The levels did not change during pregnancy, and there were no differences compared to control non-pregnant women. There was a high interindividual variation that was maintained throughout the pregnancy. The presence of +14-bp allele was associated with HLA-G5 positivity. Pregnant women who were heterozygotic to 14-bp polymorphism had significantly higher levels of HLA-G5 compared to -14 bp/-14-bp homozygotic.

CONCLUSION

Plasmatic HLA-G5 levels do not change during pregnancy and its concentration depends on 14-bp polymorphism.

The importance of HLA-G expression in embryos, trophoblast cells, and embryonic stem cells

The nonclassical HLA-G molecule is a trophoblast-specific molecule present in almost every pregnancy. It differs from classical HLA class I molecules by the low degree of allelic variants and the high diversity of protein structures. HLA-G is reported to be a tolerogenic molecule that acts on cells of both innate and adaptive immunity. At the maternal-fetal interface HLA-G seems to be responsible largely for the reprogramming of local maternal immune response. This review will focus on the HLA-G gene expression profile in pregnancy, in preimplantation embryos, and in human embryonic stem cells with emphasis on the structural diversity of the HLA-G protein and its potential functional and diagnostic implications.

The role of HLA-G in immunity and hematopoiesis

The non-classical HLA class I molecule HLA-G was initially shown to play a major role in feto-maternal tolerance. Since this discovery, it has been established that HLA-G is a tolerogenic molecule which participates to the control of the immune response. In this review, we summarize the recent advances on (1) the multiple structures of HLA-G, which are closely associated with their role in the inhibition of NK cell cytotoxicity, (2) the factors that regulate the expression of HLA-G and its receptors, (3) the mechanism of action of HLA-G at the immunological synapse and through trogocytosis, and (4) the generation of suppressive cells through HLA-G. Moreover, we also review recent findings on the non-immunological functions of HLA-G in erythropoiesis and angiogenesis.

HLA-G expression in human embryonic stem cells and preimplantation embryos

Human leukocyte Ag-G, a tolerogenic molecule that acts on cells of both innate and adaptive immunity, plays an important role in tumor progression, transplantation, placentation, as well as the protection of the allogeneic fetus from the maternal immune system. We investigated HLA-G mRNA and protein expression in human embryonic stem cells (hESC) derived from the inner cell mass (ICM) of blastocysts. hESC self-renew indefinitely in culture while maintaining pluripotency, providing an unlimited source of cells for therapy. HLA-G mRNA was present in early and late passage hESC, as assessed by real time RT-PCR. Protein expression was demonstrated by flow cytometry, immunocytochemistry, and ELISA on an hESC extract. Binding of HLA-G with its ILT2 receptor demonstrated the functional active status. To verify this finding in a physiologically relevant setting, HLA-G protein expression was investigated during preimplantation development. We demonstrated HLA-G protein expression in oocytes, cleavage stage embryos, and blastocysts, where we find it in trophectoderms but also in ICM cells. During blastocyst development, a downregulation of HLA-G in the ICM cells was present. This data might be important for cell therapy and transplantation because undifferentiated hESC can contaminate the transplant of differentiated stem cells and develop into malignant cancer cells.

Comprehensive analysis of MHC class I genes from the U-, S-, and Z-lineages in Atlantic salmon

BACKGROUND

We have previously sequenced more than 500 kb of the duplicated MHC class I regions in Atlantic salmon. In the IA region we identified the loci for the MHC class I gene Sasa-UBA in addition to a soluble MHC class I molecule, Sasa-ULA. A pseudolocus for Sasa-UCA was identified in the nonclassical IB region. Both regions contained genes for antigen presentation, as wells as orthologues to other genes residing in the human MHC region.

RESULTS

The genomic localisation of two MHC class I lineages (Z and S) has been resolved. 7 BACs were sequenced using a combination of standard Sanger and 454 sequencing. The new sequence data extended the IA region with 150 kb identifying the location of one Z-lineage locus, ZAA. The IB region was extended with 350 kb including three new Z-lineage loci, ZBA, ZCA and ZDA in addition to a UGA locus. An allelic version of the IB region contained a functional UDA locus in addition to the UCA pseudolocus. Additionally a BAC harbouring two MHC class I genes (UHA) was placed on linkage group 14, while a BAC containing the S-lineage locus SAA (previously known as UAA) was placed on LG10. Gene expression studies showed limited expression range for all class I genes with exception of UBA being dominantly expressed in gut, spleen and gills, and ZAA with high expression in blood.

CONCLUSION

Here we describe the genomic organization of MHC class I loci from the U-, Z-, and S-lineages in Atlantic salmon. Nine of the described class I genes are located in the extension of the duplicated IA and IB regions, while three class I genes are found on two separate linkage groups. The gene organization of the two regions indicates that the IB region is evolving at a different pace than the IA region. Expression profiling, polymorphic content, peptide binding properties and phylogenetic relationship show that Atlantic salmon has only one MHC class Ia gene (UBA), in addition to a multitude of nonclassical MHC class I genes from the U-, S- and Z-lineages.

Human leukocyte antigen-G molecules are constitutively expressed by synovial fibroblasts and upmodulated in osteoarthritis

Human leukocyte antigen (HLA)-G molecules are nonclassical HLA class I antigens expressed as membrane bound and soluble isoforms (sHLA-G) with a restricted tissue distribution and anti-inflammatory functions. Because inflammation is involved in the pathogenesis of osteoarthritis (OA), we have analyzed the expression and production of HLA-G molecules in in vitro cultured synovial fibroblasts (SFs) from OA patients and control subjects. We have analyzed the levels of sHLA-G1 and HLA-G5 isoforms by immunoenzymatic assay (enzyme-linked immunosorbent assay) in the SF culture supernatants from six OA patients and six control subjects in 70-day in vitro cultures and after the addition of lipopolysaccharide or recombinant interleukin (IL)-10 (rIL-10). We have confirmed HLA-G modulation by cytofluorimetry and immunofluorescence. The results have demonstrated the spontaneous production of sHLA-G1 molecules by both OA and control SFs. The expression was confirmed by cytofluorimetry and immunofluorescence. OA SFs produce both sHLA-G1 and HLA-G5 molecules during the first 23 days of culture and higher levels of sHLA-G1 during the first 40 days of in vitro culture and after lipopolysaccharide or rIL-10 activation compared with control SFs. The production of HLA-G1 molecules, constitutively expressed by control and OA SFs, is significantly increased in OA, suggesting a possible mechanism to counteract the inflammation of the synovial joints.

Cell bio-imaging reveals co-expression of HLA-G and HLA-E in human preimplantation embryos

The non-classical major histocompatibility complex (MHC) class Ib antigens, termed HLA-G and HLA-E, have been associated with fetal maternal tolerance. The role of HLA-G in the preimplantation embryo remains unclear although immunoprotection, adhesion and cell signalling mechanisms have been suggested. Unlike HLA-G, HLA-E protein expression has not been previously studied in preimplantation embryos. Embryos and model trophoblast cell lines JEG-3 and BeWo were labelled with the HLA-G- and HLA-E-specific monoclonal antibodies MEMG9 and MEME07. Flow cytometry, confocal microscopy and single particle fluorescence imaging techniques were employed to investigate the spatial and temporal expression of these receptors. Lipid raft analysis and adhesion assays were performed to investigate the role of these receptors in cell membrane domains and in promoting adhesion by cell-to-cell contact. HLA-E and HLA-G were co-localized in the trophectoderm of day 6 blastocysts. Analysis on trophoblast cell lines revealed that 37% of HLA-G and 41% of HLA-E receptors were co-localized as tetramers or higher order homodimer clusters. HLA-G receptors did not appear to play a role in either cell adhesion or immunoreceptor signalling via lipid raft platforms on the cell membrane. A possible role of HLA-G and HLA-E in implantation via immunoregulation or modulation of uterine maternal leukocytes is discussed.