Implication of HLA-G in Human Embryo Implantation

Mesenchymal stem cells in ischemic tissue regeneration

Diseases caused by ischemia are one of the leading causes of death in the world. Current therapies for treating acute myocardial infarction, ischemic stroke, and critical limb ischemia do not complete recovery. Regenerative therapies opens new therapeutic strategy in the treatment of ischemic disorders. Mesenchymal stem cells (MSCs) are the most promising option in the field of cell-based therapies, due to their secretory and immunomodulatory abilities, that contribute to ease inflammation and promote the regeneration of damaged tissues. This review presents the current knowledge of the mechanisms of action of MSCs and their therapeutic effects in the treatment of ischemic diseases, described on the basis of data from in vitro experiments and preclinical animal studies, and also summarize the effects of using these cells in clinical trial settings. Since the obtained therapeutic benefits are not always satisfactory, approaches aimed at enhancing the effect of MSCs in regenerative therapies are presented at the end.

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.

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.

The Importance of HLA Assessment in "Off-the-Shelf" Allogeneic Mesenchymal Stem Cells Based-Therapies

The need for more effective therapies of chronic and acute diseases has led to the attempts of developing more adequate and less invasive treatment methods. Regenerative medicine relies mainly on the therapeutic potential of stem cells. Mesenchymal stem cells (MSCs), due to their immunosuppressive properties and tissue repair abilities, seem to be an ideal tool for cell-based therapies. Taking into account all available sources of MSCs, perinatal tissues become an attractive source of allogeneic MSCs. The allogeneic MSCs provide "off-the-shelf" cellular therapy, however, their allogenicity may be viewed as a limitation for their use. Moreover, some evidence suggests that MSCs are not as immune-privileged as it was previously reported. Therefore, understanding their interactions with the recipient's immune system is crucial for their successful clinical application. In this review, we discuss both autologous and allogeneic application of MSCs, focusing on current approaches to allogeneic MSCs therapies, with a particular interest in the role of human leukocyte antigens (HLA) and HLA-matching in allogeneic MSCs transplantation. Importantly, the evidence from the currently completed and ongoing clinical trials demonstrates that allogeneic MSCs transplantation is safe and seems to cause no major side-effects to the patient. These findings strongly support the case for MSCs efficacy in treatment of a variety of diseases and their use as an "off-the-shelf" medical product.

Evaluation of HLA-G Expression in Multipotent Mesenchymal Stromal Cells Derived from Vitrified Wharton's Jelly Tissue

BACKGROUND

Mesenchymal Stromal Cells (MSCs) from Wharton's Jelly (WJ) tissue express HLA-G, a molecule which exerts several immunological properties. This study aimed at the evaluation of HLA-G expression in MSCs derived from vitrified WJ tissue.

METHODS

WJ tissue samples were isolated from human umbilical cords, vitrified with the use of VS55 solution and stored for 1 year at -196 °C. After 1 year of storage, the WJ tissue was thawed and MSCs were isolated. Then, MSCs were expanded until reaching passage 8, followed by estimation of cell number, cell doubling time (CDT), population doubling (PD) and cell viability. In addition, multilineage differentiation, Colony-Forming Units (CFUs) assay and immunophenotypic analyses were performed. HLA-G expression in MSCs derived from vitrified samples was evaluated by immunohistochemistry, RT-PCR/PCR, mixed lymphocyte reaction (MLR) and immunofluorescence. MSCs derived from non-vitrified WJ tissue were used in order to validate the results obtained from the above methods.

RESULTS

MSCs were successfully obtained from vitrified WJ tissues retaining their morphological and multilineage differentiation properties. Furthermore, MSCs from vitrified WJ tissues successfully expressed HLA-G.

CONCLUSION

The above results indicated the successful expression of HLA-G by MSCs from vitrified WJ tissues, thus making them ideal candidates for immunomodulation.

Tissue-specific Differentiation Potency of Mesenchymal Stromal Cells from Perinatal Tissues

Human perinatal tissue is an abundant source of mesenchymal stromal cells(MSCs) and lacks the ethical concerns. Perinatal MSCs can be obtained from various tissues as like amnion, chorion, and umbilical cord. Still, little is known of the distinct nature of each MSC type. In this study, we successfully isolated and cultured MSCs from amnion(AMSCs), chorion(CMSCs), and umbilical cord(UC-MSCs). Proliferation potential was different among them, that AMSCs revealed the lowest proliferation rate due to increased Annexin V and senescence-associated β-galactosidase positive cells. We demonstrated distinct characteristic gene expression according to the source of the original tissue using microarray. In particular, genes associated with apoptosis and senescence including CDKN2A were up-regulated in AMSCs. In CMSCs, genes associated with heart morphogenesis and blood circulation including HTR2B were up-regulated. Genes associated with neurological system processes including NPY were up-regulated in UC-MSCs. Quantitative RT-PCR confirmed the gene expression data. And in vitro differentiation of MSCs demonstrated that CMSCs and UC-MSCs had a more pronounced ability to differentiate into cardiomyocyte and neural cells, respectively. This study firstly demonstrated the innate tissue-specific differentiation potency of perinatal MSCs which can be helpful in choosing more adequate cell sources for better outcome in a specific disease.

Concise review: combining human leukocyte antigen G and mesenchymal stem cells for immunosuppressant biotherapy

Both human leukocyte antigen G (HLA-G) and multipotential mesenchymal stem/stromal cells (MSCs) exhibit immunomodulatory functions. In allogeneic tranplantation, the risks of acute and chronic rejection are still high despite improvement in immunosuppressive treatments, and the induction of a state of tolerance to alloantigens is not achieved. Immunomodulatory properties of MSCs and HLA-G in human allogeneic tranplantation to induce tolerance appears attractive and promising. Interestingly, we and others have demonstrated that MSCs can express HLA-G. In this review, we focus on the expression of HLA-G by MSCs and discuss how to ensure and improve the immunomodulatory properties of MSCs by selectively targeting MSCs expressing HLA-G (MSCs(HLA-G+)). We also discuss the possible uses of MSCs(HLA-G+) for therapeutic purposes, notably, to overcome acute and chronic immune rejection in solid-organ allogeneic transplantation in humans. Since MSCs are phenotypically and functionally heterogeneous, it is of primary interest to have specific markers ensuring that they have strong immunosuppressive potential and HLA-G may be a valuable candidate.

Non-classical transcriptional regulation of HLA-G: an update

Human leucocyte antigen-G (HLA-G) plays a key role in maternal–foetal tolerance and allotransplantation acceptance and is also implicated in tumour escape from the immune system. The modulation of HLA-G expression can prove to be very important to therapeutic goals in some pregnancy complications, transplantation, cancer and possibly autoimmune diseases. In spite of substantial similarities with classical HLA-class I genes, HLA-G is characterized by a restricted tissue-specific expression in non-pathological situations. HLA-G expression is mainly controlled at the transcriptional level by a unique gene promoter when compared with classical HLA-class I genes, and at the post-transcriptional level including alternative splicing, mRNA stability, translation and protein transport to the cell surface. We focus on the characteristics of the HLA-G gene promoter and the factors which are involved in HLA-G transcriptional modulation. They take part in epigenetic mechanisms that control key functions of the HLA-G gene in the regulation of immune tolerance.

MicroRNA signature and regulatory functions in the endometrium during normal and disease states

During the menstrual cycle, human endometrium undergoes extensive cyclic morphologic and biochemical modifications in preparation for embryo implantation. These processes are highly regulated by ovarian steroids and various locally expressed gene products and involve inflammatory reaction, apoptosis, cell proliferation, angiogenesis, differentiation (tissue formation), and tissue remodeling. MicroRNAs (miRNAs) have emerged as key regulators of gene expression, and their altered and/or aberrant expression has been associated with establishment and progression of various disorders, including tumorigenesis. This review highlights the endometrial expression of miRNAs and their potential regulatory functions under normal and pathologic conditions such as endometriosis, dysfunctional uterine bleeding, and endometrial cancer. Given the key regulatory function of miRNAs on gene expression stability, understanding the underlying mechanisms of how endometrial miRNAs are regulated and identifying their specific target genes and their functions might lead to the development of preventive and therapeutic strategies by regulating specific target genes associated with such reproductive disorders.

Immunogenetics of pregnancy: role of a 14-bp deletion in the maternal HLA-G gene in primiparous pre-eclamptic Brazilian women

The etiology and pathogenesis of pre-eclampsia (PE) involve a combination of maternal-fetal genetic and immunologic factors. The immunologic maladaptation theory of PE predicts that the maternal immune system does not tolerate the semi-allogeneic fetus. Human leukocyte antigen-G (HLA-G) is expressed in some types of immune cells as well as in the fetal-maternal interface by trophoblasts, playing an immunoregulatory role. Here we have evaluated a 14-bp deletion polymorphism in the 3'-untranslated region of exon 8 of HLA-G gene in pregnant PE women and controls. HLA-G genotypes in both control and PE women were in Hardy-Weinberg equilibrium. The healthy pregnant and PE women had similar genotype frequencies (p = 0.789). This was similarly observed when PE women were subgrouped accordingly to severity of disease (p = 0.646). However, the primiparous PE women presented a tendency toward higher frequency of the 14-bp deletion allele (0.442) compared with the primiparous healthy women (0.286), p = 0.09. Our data suggest that the maternal 14-bp deletion of HLA-G is not associated with the risk for PE but that it could affect the development of PE in primiparous women.

Predicting human embryo viability: the road to non-invasive analysis of the secretome using metabolic footprinting

Infertility affects an increasing number of couples and for many the treatment of choice is IVF. However, the success rate remains relatively low, and, as typically two or more embryos are implanted, successful pregnancy often leads to multiple pregnancies with attendant complications. The major limitation in clinical IVF is the inability to predict which embryos are most viable, with the highest chance of implantation and development to a live baby. In principle, embryos can be selected for transfer based on data obtained at the genomic, transcriptomic, proteomic and/or metabolomic levels; however, these measurements cannot always be made directly on the embryo without invasive biopsy of cells. Alternative strategies are needed and this review considers the range of possibilities, with a focus on the analysis of the secretome from human embryos using metabolic footprinting.