Bae-Li Hsi

Dynamics of human sperm acrosome reaction: relation with in vitro fertilization

OBJECTIVE Acrosomal status has been studied on human sperm prepared for in vitro fertilization (IVF) and related to the rate of fertilization. DESIGN AND PATIENTS A group of 41 men with normal classical semen parameters, included in the IVF program of University of Nice for feminine tubal obstruction (n = 37) or unexplained infertility (n = 4), were evaluated in a prospective study and compared with a control group of 10 fertile donors. MAIN OUTCOME MEASURES Evaluation of acrosome status (spontaneous and A23187-induced acrosome loss) after 6 hours incubation in Ménézos B2 medium was made by flow cytometry on suspended cells with a new immunofluorescence test recently reported by the authors based on a monoclonal antibody GB24. RESULTS Spontaneous acrosome loss remained low even after 6 hours capacitation (mean + 1 SD, 6.5% + 4.9%). Response to A23187 increased with the duration of preincubation with a marked response after 6 hours (29.5% + 8.9%). Low spontaneous acrosome loss (less than mean + 1 SD) and high response to A23187 (greater than mean - 1 SD) were observed in 25 out of 26 cases of group A with a high fertilization rate (greater than 50% fertilized oocytes). A high level of spontaneous acrosome loss and/or a lack of response to A23187 was observed in 2 of 7 cases of group B (fertilization rate less than 50%) and 6 of 8 cases of group C (unexplained unsuccessful fertilization). CONCLUSION Impaired acrosomal status can be associated with unexplained unsuccessful fertilization.

Differential expression of complement regulatory proteins on subpopulations of human trophoblast cells

Trophoblast cells forming the reactive interface between the mother and her semiallogeneic fetus risk attack by cellular and humoral elements of the maternal immune system. Biochemical, molecular, and immunohistologic studies have identified membrane cofactor protein (MCP) and decay accelerating factor (DAF) on trophoblast cells, which could assist in preventing lysis of the cells by complement-activating maternal antibodies. In this immunocytochemical study, differential expression of these two members of the family of complement regulatory proteins on subpopulations of human trophoblast cells and other types of cells in first and third trimester placentas was demonstrated. Staining with anti-MCP was particularly strong on villous cytotrophoblast cells and giant cells in first trimester tissues in comparison with other types of cells. In contrast, staining with anti-DAF was strong on proliferating cytotrophoblast in first trimester tissues, and on basal plate cytotrophoblast and decidual cells in term tissues. Placental villous mesenchymal cells but not trophoblast cells expressed a third regulatory protein, complement receptor 1. These observations support the postulate that complement regulatory proteins are critical to protection of the fetal allograft, and suggest specific requirements for trophoblast cells according to stage of differentiation and anatomic location.

Monoclonal antibodies to human amnion

Mouse hybridoma cell lines secreting monoclonal antibodies to human amnion were established. The reactivities of eight of these monoclonal antibodies (GB1, GB3, GB4, GB5, GB6, GB9, GB10 and GB11) on human skin and term extra-embryonic tissues, which included reflected amniochorions, basal plates, placentae, chorionic plates and umbilical cords, are reported. GB1, GB4, GB5, GB6, GB9 and GB11 showed various reactivity patterns on the epithelial cells of amnion, chorion and skin at different stages of differentiation. In addition, GB9 and GB11 showed extracellular reactivities; GB9 detected chorionic villi which were usually surrounded by fibrinoid and GB11 reacted with fibrinoid structures in the placentae and chorion laeve. GB10 recognized connective tissues in fetal mesenchyme and adult dermis. This study demonstrates the expression of many shared antigens between tissues derived from the extra-embryonic ectoderm and adult skin. These monoclonal antibodies will provide useful tools for further investigations of epithelial differentiation and transformation.

Expression of Complement Regulatory Proteins on Human Eggs and Preimplantation Embryos

PROBLEM: To investigate the relation between the complement system and reproduction, expression of complement regulatory proteins (C3b receptors and inhibitor of the membrane attack complex) were screened on unfixed human eggs and preimplantation embryos.

Evaluation of a Monoclonal Antibody, BC‐1, Which Identifies an Antigen Expressed on the Surface Membrane of Human Extravillous Trophoblast

ABSTRACT: This paper describes a new Mab BC‐1 which is directed at a cell surface antigen expressed by extravillous cytotrophoblast and not by villous cytotrophoblast, so it is useful for distinguishing between the two populations. The antigen recognised by BC‐1 is trypsin‐resistant, which allows it to be used for flow cytometric analysis of living trophoblast isolated by enzymic disaggregation. However, BC‐1 is not trophoblast‐specific but cross‐reacts with some other tissues, in particular endothelial cells and peripheral blood monocytes. The nature of this antigen has not been established.

Detection of class I MHC mRNA in subpopulations of first trimester cytotrophoblast cells by in situ hybridization

Class I MHC mRNA has been identified in both villous and extravillous cytotrophoblast cells in first trimester placentas by in situ hybridization. In this report, we expand those observations to additional morphologically and anatomically distinct subpopulations of trophoblast cells in early placentas using the same experimental approach. In the transition zone of first trimester placental villi, where cytotrophoblast cells are proliferating to form new villi or to migrate into adjacent tissue, both cytotrophoblast cells beneath the uninterrupted syncytium and the proliferating cytotrophoblast cells contained class I mRNA whereas a layer of cytotrophoblast cells proximal to the villus core did not contain class I mRNA. In the placental bed, migrating cytotrophoblast cells contained high levels of class I mRNA as determined by the intensity of staining. In contrast, multinucleated giant trophoblast cells contained little specific message. Alterations in levels of class I mRNA seem therefore to be associated with trophoblast proliferation, migration and differentiation.

Topographical expression of class I major histocompatibility complex antigens on human amniotic epithelium

The expression of class I major histocompatibility complex (MHC) antigens on different regions of human amnion was studied by the avidin-biotin-complex immunoperoxidase (ABC) technique using monoclonal antibodies. In contrast to previous reports, the use of higher affinity monoclonal antibodies and the sensitive immunoperoxidase method has allowed the identification of class I MHC antigens on the amniotic epithelium. The level of expression is different between cells from various parts of the amnion, with the amniotic epithelium from the edge of the placenta consistently showing the strongest reactivity. Some of the class I MHC antigens expressed by the amnion are similar to those expressed by extravillous trophoblast cells in that both show much weaker or no reactivity with the monoclonal antibody 61D2.

Monoclonal antibody GB17 recognizes human syncytiotrophoblast

A monoclonal antibody, GB17, was obtained from a hybridoma produced following murine immunization with isolated human term syncytiotrophoblastic microvilli. Immunohistological studies demonstrated the GB17 antigen to be present on syncytiotrophoblast of human term, first- and second trimester placenta, but not on human extravillous trophoblast or baboon placental trophoblast. Other normal adult human tissues and transformed cell lines tested were non-reactive with this antibody. Radio-iodinated term syncytiotrophoblastic microvillous protein was immunoprecipitated by GB17, and shown by sodium dodecyl sulfate--polyacrylamide gel electrophoresis to migrate as a single protein band at 175 kDa. The restricted tissue specificity suggests that the GB17 antigen could be useful for the development of a contragestational vaccine.

Human amnion cells: modulation of expression of specific antigens

Antigen expression by fetal cells near the mother is of interest because of the possibility that some antigens may stimulate beneficial maternal immune responses or may prevent the development of harmful responses. The recent generation of monoclonal antibodies to amnion and trophoblast antigens together with the finding that class I histocompatibility antigen (HLA) expression by amnion cells can be manipulated provided an opportunity to determine if any relationships exist among expression of HLA, amnion antigens, and trophoblast antigens. The results of the present study demonstrate that: class I HLA and amnion-specific antigens are co-expressed by IFN-gamma-modulated amnion cells, so neither prevents expression of the other; EGF enhances expression of two amnion-specific antigens; amnion cells do not express transferrin receptors, placental alkaline phosphatase, or other antigens normally associated with trophoblasts following exposure to IFN-gamma and/or EGF. The results demonstrate independent modulation of expression of class I HLA, two amnion-specific antigens, and some trophoblast-associated antigens on amnion epithelial cells.