Expression of complement regulatory proteins on human eggs and preimplantation embryos

Proteomic and Bioinformatic Analysis of Decellularized Pancreatic Extracellular Matrices

Tissue microenvironments are rich in signaling molecules. However, factors in the tissue matrix that can serve as tissue-specific cues for engineering pancreatic tissues have not been thoroughly identified. In this study, we performed a comprehensive proteomic analysis of porcine decellularized pancreatic extracellular matrix (dpECM). By profiling dpECM collected from subjects of different ages and genders, we showed that the detergent-free decellularization method developed in this study permits the preservation of approximately 62.4% more proteins than a detergent-based method. In addition, we demonstrated that dpECM prepared from young pigs contained approximately 68.5% more extracellular matrix proteins than those prepared from adult pigs. Furthermore, we categorized dpECM proteins by biological process, molecular function, and cellular component through gene ontology analysis. Our study results also suggested that the protein composition of dpECM is significantly different between male and female animals while a KEGG enrichment pathway analysis revealed that dpECM protein profiling varies significantly depending on age. This study provides the proteome of pancreatic decellularized ECM in different animal ages and genders, which will help identify the bioactive molecules that are pivotal in creating tissue-specific cues for engineering tissues in vitro.

Proteome reprogramming of endometrial epithelial cells by human trophectodermal small extracellular vesicles reveals key insights into embryo implantation

Embryo implantation into the receptive endometrium is critical in pregnancy establishment, initially requiring reciprocal signalling between outer layer of the blastocyst (trophectoderm cells) and endometrial epithelium; however, factors regulating this crosstalk remain poorly understood. Although endometrial extracellular vesicles (EVs) are known to signal to the embryo during implantation, the role of embryo-derived EVs remains largely unknown. Here, we provide a comprehensive proteomic characterisation of a major class of EVs, termed small EVs (sEVs), released by human trophectoderm cells (Tsc-sEVs) and their capacity to reprogram protein landscape of endometrial epithelium in vitro. Highly purified Tsc-sEVs (30-200 nm, ALIX⁺ , TSG101⁺ , CD9/63/81⁺ ) were enriched in known players of implantation (LIFR, ICAM1, TAGLN2, WNT5A, FZD7, ROR2, PRICKLE2), antioxidant activity (SOD1, PRDX1/4/6), tissue integrity (EZR, RAC1, RHOA, TNC), and focal adhesions (FAK, ITGA2/V, ITGB1/3). Functionally, Tsc-sEVs were taken up by endometrial cells, altered transepithelial electrical resistance, and upregulated proteins implicated in embryo attachment (ITGA2/V, ITGB1/3), immune regulation (CD59, CD276, LGALS3), and antioxidant activity (GPX1/3/4, PRDX1/2/4/5/6): processes that are critical for successful implantation. Collectively, we provide critical insights into Tsc-sEV-mediated regulation of endometrial function that contributes to our understanding of the molecular basis of implantation.

Embryo-maternal communication in dogs: Immune system related factors

In the bitch, establishment of pregnancy is believed to be mainly initiated by the free-floating embryo in the uterus that is under progesterone influence. As in other species, the active participation of the embryo is no longer questioned. Secretory products are transported to the embryo-maternal interface and contribute to extra-cellular matrix (ECM) degradation, a change in the intrauterine immune milieu towards a reduction of immune cells and a change in lymphocyte subsets, cell differentiation, angiogenesis, and the balance between proliferation and apoptosis. For cell-to-cell communication between embryo and maternal tissue, biomolecules inclusive microRNAs might be transported and exchanged via extracellular vesicles (EVs) as in other species. Maternal acceptance of the fetal allograft is vital for the establishment of pregnancy. Findings so far indicate that the embryo avoids attacks from the maternal system via passive and active mechanisms. One hypothesis is that expression or suppression of surface molecules help the canine embryo to hide from the maternal immune system on one side and to actively destroy cytotoxic immune cells on the other side; there are further clues that the canine embryo blocks activation of intrauterine leukocytes. Intracellular repair mechanisms via heat shock proteins (HSP) are candidates under investigation. The presence and function of immunomodulatory intrauterine cells like Treg cells and their interaction with the embryo have been intensely studied in other species but remains to be investigated in the canine preimplantation uterus.

Complement in Human Pre-implantation Embryos: Attack and Defense

It is essential for early human life that mucosal immunological responses to developing embryos are tightly regulated. An imbalance of the complement system is a common feature of pregnancy complications. We hereby present the first full analysis of the expression and deposition of complement molecules in human pre-implantation embryos. Thus, far, immunological imbalance has been considered in stages of pregnancy following implantation. We here show that complement activation against developing human embryos takes place already at the pre-implantation stage. Using confocal microscopy, we observed deposition of activation products on healthy developing embryos, which highlights the need for strict complement regulation. We show that embryos express complement membrane inhibitors and bind soluble regulators. These findings show that mucosal complement targets human embryos, and indicate potential adverse pregnancy outcomes, if regulation of activation fails. In addition, single-cell RNA sequencing revealed cellular expression of complement activators. This shows that the embryonic cells themselves have the capacity to express and activate C3 and C5. The specific local embryonic expression of complement components, regulators, and deposition of activation products on the surface of embryos suggests that complement has immunoregulatory functions and furthermore may impact cellular homeostasis and differentiation at the earliest stages of life.

Preimplantation embryos cooperate with oviductal cells to produce embryotrophic inactivated complement-3b

Human oviductal epithelial (OE) cells produce complement protein 3 (C3) and its derivatives, C3b and inactivated complement-3b (iC3b). Among them, iC3b is the most potent embryotrophic molecule. We studied the production of iC3b in the oviductal cell/embryo culture system. In the immune system, C3 convertase converts C3 into C3b, and the conversion of C3b to iC3b requires factor I (fI) and its cofactors, such as factor H or membrane cofactor protein. Human oviductal epithelium and OE cells expressed mRNA and protein of the components of C3 convertase, including C2, C4, factor B, and factor D. The OE cell-conditioned medium contained active C3 convertase activity that was suppressed by C3 convertase inhibitor, H17 in a dose and time-dependent manner. Although the oviductal epithelium and OE cells produced fI, the production of its cofactor, factor H required for the conversion of C3b to iC3b, was weak. Thus, OE cell-conditioned medium was inefficient in producing iC3b from exogenous C3b. On the contrary, mouse embryos facilitated such conversion to iC3b, which was taken up by the embryos, resulting in the formation of more blastocysts of larger size. The facilitatory activity was mediated by complement receptor 1-related gene/protein Y (Crry) with known membrane cofactor protein activity on the trophectoderm of the embryos as anti-Crry antibody inhibited the conversion and embryotrophic activity of C3b in the presence of fI. In conclusion, human oviduct possesses C3 convertase activity converting C3 to C3b, and Crry of the preimplantation embryos may be involved in the production of embryotrophic iC3b on the surface of the embryos.

Restriction of GAGE protein expression to subpopulations of cancer cells is independent of genotype and may limit the use of GAGE proteins as targets for cancer immunotherapy

The GAGE cancer testis antigen gene family encodes products that can be recognized by autologous T cells, and GAGE proteins have been suggested as potential targets for cancer immunotherapy. Analysis of GAGE expression in tumours has primarily been performed at the level of gene transcription, whereas little is known about GAGE expression at the protein level. To evaluate the potential of GAGE proteins as targets for cancer-specific immunotherapy, we studied the expression of these proteins in normal and malignant cells/tissues using a novel panel of monoclonal antibodies. Immunohistochemical analysis of more than 250 cancer specimens demonstrated that GAGE proteins were frequently expressed in numerous cancer types and correlated with the expression of the cancer testis antigens MAGE-A1 and NY-ESO-1. Significant intercellular and subcellular differences in GAGE protein levels were observed, and most GAGE-positive tumours also contained cancer cells lacking GAGE expression. Studies of genetically homogenous cell lines with similar intercellular heterogeneous GAGE expression showed that GAGE expression was not associated with a specific genotype, but defined a phenotypically distinct population of cells. Surprisingly, in normal tissues we found that GAGE proteins were not restricted to testis, but were also present in a subset of oocytes of resting primordial follicles and in maturing oocytes. This is the first time that a cancer testis antigen has been reported in postfoetal oocytes. The lack of GAGE expression in a subset of cancer cells within GAGE-positive tumours has decisive implications for the development of GAGE-targeted cancer therapy.

Complement and complement regulators in the male reproductive system

Spermatozoa are almost unique among cells in that they must survive transplantation into a foreign host in order to perform their physiological role. The biggest hurdle to overcome is innate immune defence that will target the invaders in the female genital tract. Complement is a major player in innate immunity and is present in the female genital tract. Spermatozoa must therefore evade complement attack if they are to reach their goal. Complement evasion is achieved by the presence of complement regulators both in seminal plasma and on the spermatozoa. Here we discuss the parts played by complement and complement regulators in permitting spermatozoa to survive long enough to reach the oocyte, in clearance of the excess spermatozoa that have outlived their usefulness and in aiding activation of spermatozoa to engage the oocyte. In particular, we focus on the unique distribution patterns of complement regulators on spermatozoa, patterns that strongly suggest roles in spermatozoal development and oocyte binding. An understanding of these roles will inform studies of their contribution to fertility and infertility in man.

Identification, characterization and localization of three proteins expressed by the porcine oviduct

At estrus, the oviduct undergoes endocrine-induced changes which provide an essential microenvironment for maturation of gametes, fertilization and embryonic development. Several oviduct expressed proteins which interact with gametes or embryos, including the oviduct-specific, estrogen-dependent glycoprotein (OGP), have been identified and characterized. The objective of the present study was to identify, characterize and localize other proteins expressed by the porcine oviduct during estrus that may function in an autocrine or paracrine manner to enhance fertilization and embryonic development. Oviducts were collected during the estrous cycle or early pregnancy, flushed and divided into functional segments, and portions of the infundibulum, ampulla and isthmus were fixed for immunocytochemical analysis or cultured. Culture media was semi-purified by heparin-agarose affinity chromatography, proteins were transferred to polyvinylidene fluoride (PVDF) membrane after two-dimensional (2D)-SDS-PAGE and three different proteins were identified, excised and subjected to N-terminal amino acid analysis. These proteins were identified as complement component C3b, the carboxy-terminal propeptide of alpha 1 (III) procollagen (PIIICP), and the heavy chain variable region of IgA. Electrophoresis and fluorography of media from Days 0 to 12 of early pregnancy or the estrous cycle revealed both spatial and temporal expression of C3b and IgA heavy chain but not PIIICP by the oviduct. Further, all three proteins were identified in oviduct fluid by electrophoresis, immunoblot or immunoprecipitation analysis. Complement component C3b and IgA heavy chain were immunolocalized in all three oviduct segments on all days; however, temporal and spatial differences were demonstrated. Staining was greater in the infundibulum and during estrus for all three identified proteins. In summary, three proteins expressed by the oviduct at estrus and during early pregnancy were identified; characterization and localization suggest they may play a critical role in protecting the luminal environment, participating in ECM remodeling and gamete interactions.

Potential involvement of C(3) complement factor in amphibian fertilization

We have assessed the potential involvement of C(3), the third complement factor, and its receptor in Bufo arenarum fertilization. We show that a polyclonal antibody against a B. arenarum C(3)-like factor (C(3)Ba) reacts specifically with components of the extracellular matrix (ECM) of coelomic eggs and the cell membrane of uterine eggs. Interestingly, we have identified a 163 kD protein immunoreactive with a monoclonal antibody against the CD11b alpha chain of the human C(3) receptor on the cell membrane of the animal pole of uterine eggs, the site of entry of the sperm, but not in coelomic eggs (CR3Ba). Treatment of coelomic eggs with a pars recta oviductal-like protease, trypsin, induced the translocation of C(3)Ba from the ECM to the cell membrane. Furthermore, inhibition of CR3Ba by trypan blue, as well as inhibition of C(3)Ba by anti-C(3)Ba on uterine eggs impaired fertilization, whereas identical treatment on sperm cells did not alter percentage fertilization. Our results suggest, (A) that changes in the localization of C(3)Ba from the ECM to the cell membrane may be triggered by trypsin-like proteases during passage of eggs through the oviduct; and (B) that C(3)Ba/CR3Ba may be involved in B. arenarum fertilization.

Decay accelerating factor in guinea-pig reproductive organs

Decay accelerating factor (DAF, CD55) expressed in human reproductive organs and gametes is thought to play a pivotal role in protection against autologous complement activation in the genital tract. To further investigate the role of DAF in reproduction, we analysed DAF distribution in reproductive organs using guinea-pigs that express multiple DAF isoforms. In males, significant staining was observed in testis on the elongated spermatids and spermatozoa. Levels of DAF mRNA with a shorter 3' untranslated region were significantly enhanced in testis from 9 weeks of age, indicating the presence of DAF mRNA and protein synthesis of spermatozoa DAF in late haploid germ cells. Epididymal spermatozoa appeared to express DAF on the inner acrosomal membrane as well as over their entire surface. Significant DAF expression was also observed on the epithelium of seminal vesicles from 4 weeks of age, with no increase thereafter in the mRNA. C3 mRNA was not detected in this tissue. In females, DAF was detected on the plasma membranes of oocytes through follicle development and on the apical region of uterine epithelium, although the levels of DAF mRNA in these tissues were low. In addition, DAF was selectively expressed on the apical region of ciliated oviductal epithelial cells. The apical region of the ciliated cells comprising the efferent ductule epithelium was also stained significantly, even at 12 days of age, while other epididymal epithelial cells were hardly stained at any age, suggesting that DAF is constitutively expressed on cilia.

The expression of genes in human preimplantation embryos

The study of gene expression in human preimplantation embryos is establishing itself as a necessary dimension of developmental biology and medical genetics. Transcripts identified in human preimplantation embryos include housekeeping genes, transcription and growth factor genes, sex-determining genes, tissue-specific genes and novel genes, as well as genes of unknown function. Strategies are being developed which will eventually permit the most sophisticated gene expression studies on single human embryos of co-ordinated transcription and translational regulation. There is both a need for international co-operation for the systematic construction of expression maps and a need to establish databases of expression patterns during different stages of human development. Understanding how genes are regulated in humans is essential for understanding both normal development and disease. Until recently, studies of gene expression and regulation during embryogenesis were almost exclusively limited to prokaryotes and to eukaryotes other than man. The introduction of artificial reproductive technologies in conjunction with the development of recombinant molecular technologies applicable to single cells has made possible the study of human development at its earliest stages (Pergament and Bonnicksen, 1994). Although there are still enormous technical challenges, robust strategies have been, and continue to be, developed for connecting DNA sequence to such endophenotypes as timing and level of genes expression at the single cell level. Questions currently being asked in human developmental genetic studies concern the pronucleus, the zygote and the preimplantation embryo: what genes are expressed? When are they expressed? What functions do they perform and how, in sequence or in combination? And, what elements control and regulate their expression? This review provides an overview of current knowledge about the expression of different embryonic genes during early human development and discusses future prospects, which includes a need for international co-operation similar to the Human Genome Project.

HLA expression on immature and mature human germ cells

Human leukocyte antigens (HLA) are membrane-bound glycoproteins encoded by the human major histocompatibility complex located on chromosome 6. They are known to function in immnunologic recognition and, with regard to reproduction, a number of non-immune functions have been proposed. Although the expression patterns of the major histocompatibility antigens have been extensively studied at the maternal fetal interface, there are still controversial reports on the expression of these molecules by human gametes and preimplantation stages. This brief review focuses on recent studies where the expression and distribution of HLA on human spermatogenic cells (spermatogonia, primary and secondary spermatocytes, spermatids, spermatozoa), primary and secondary oocytes, and preimplantation embryos have been investigated. These results, and their possible implications for the fertilization process and further embryonic development, will be presented.

Detection of complement C1q receptors on human spermatozoa

Clq, the first component of the classical complement pathway, is known to play roles in promoting phagocytic events, in addition to its role in activation of complement. Although the molecular events in fertilization leading to the entrance of the spermatozoan into the egg are not well understood, ultrastructural observations suggest that the process is quasi-phagocytic in nature. There is increasing evidence that complement components might play roles in fertilization. Previously, we have shown that C1q promoted the agglutination of capacitated human sperm as well as their adhesion to zona-free hamster eggs. In the present experiments, human spermatozoa were solubilized and, following their phase separation in Triton X-114, subject to 1-D polyacrylamide gel electrophoresis and immunoblotting for the presence of C1q receptors. Both gC1q-R and cC1q-R were detected. In addition, the ability of C1q to promote sperm agglutination was shown to be dependent upon capacitation, suggesting the increased expression of C1q receptors during this process.

Human autoantibodies recognizing human and mouse preimplantation stages

PROBLEM

To find out whether autoantibodies against human preimplantation stages are present in some human sera and, if so, whether the antibodies could be capable to affect the egg development and/or to trigger an activation of the complement system at the procedures of assisted conception.

METHODS

1. Immunohistochemistry on blots of human preimplantation stages. 2. Immunohistochemistry on paraffin sections of human and mouse preimplantation stages. 3. Culture of mouse morulae to analyze complement activation.

RESULTS

1. Some human sera contained autoantibodies against human preimplantation stages. 2. Human-mouse cross-reacting antibodies against preimplantation stages occurred. 3. Immune complexes, formed on mouse preimplantation stages, activated the complement systems in egg cultures, resulting in a damaging of the eggs.

CONCLUSION

The presence of natural autoantibodies to preimplantation stages may be associated with reproduction failure, caused by a direct effect by the autoantibodies and/or an activation of the uterine complement system by the immune complexes formed.