Koji Koyama

Functional aspects of CD52 in reproduction

CD52 is a GPI-anchored protein present in lymphocytes and male reproductive tissues (mrt) including mature sperm and seminal plasma. It has been shown that mrt-CD52 is synthesized in epithelial cells of the epididymis and vas deferens, but not in the testis. The mrt-CD52 is transported to mature sperm during sperm transition in the male reproductive tract. Lymphocyte CD52 functions to stimulate suppressor T cell induction, while mrt-CD52 is associated with seminogelin and involved in clot formation and liquefaction of semen. In a landmark study, a monoclonal antibody (Mab H6-3C4) from peripheral B lymphocytes of a patient with complement-dependent sperm-immobilizing antibody in the serum has been generated. Using Mab H6-3C4, the carbohydrate moiety of CD52 as an epitope for infertility-related antigen was identified. Mab H6-3C4 also shows strong complement-dependent sperm-immobilizing activity. This suggests CD52 may have a function in protecting sperm from complement activation. Indeed, purified mrt-CD52 from human sperm interferes with the classical pathway, but not lectin-binding or alternative pathways, of the complement systems. Recently, we found CD52 in ovulated cumulus cells from the female reproductive tissues (frt). The frt-CD52 is not recognized by Mab H6-3C4, suggesting that it harbors distinct carbohydrate antigenicity. Further studies are necessary to determine the molecular features and biological functions of CD52 in male and female reproductive tissues.

Harmful effects of anti-zona pellucida antibodies in folliculogenesis, oogenesis, and fertilization

The zona pellucida (ZP) is an extracellular matrix that surrounds the mammalian oocyte and plays an important role in normal folliculogenesis and fertilization. Because of its strong immunogenicity and its possible relation with premature ovarian failure, we conducted the present study to examine whether or not anti-ZP antibodies impaired folliculogenesis. Mouse preantral follicles were cultured with anti-ZP antibodies to evaluate the effects on follicle growth and antral formation. The cultured follicles were also examined by electron microscope and assessed for oocyte maturation, fertilization capacity, and embryo development. The results showed that follicles cultured with anti-ZP antibodies had a smaller diameter than the controls. Also, these antibodies reduced antral formation, mucification, maturation of oocytes (metaphase II), and fertilization rates. Morphologically, ZP thickness was lower in the anti-ZP antibody groups. The quantity of granulosa cell microvillous processes that transverse the ZP was diminished in follicles cultured with anti-ZP antibodies. In conclusion, anti-ZP antibodies were harmful to the normal development of mouse follicles and oocytes in vitro. These antibodies may be a cause of premature ovarian failure syndrome because they disrupt the gap junctions between the oocyte and granulosa cells and, as a consequence, damage the bidirectional communication necessary for normal folliculogenesis.

CD52 is synthesized in cumulus cells and secreted into the cumulus matrix during ovulation.

Problem  Early studies have shown that an antibody to male reproductive tissue CD52 is a pathogenic factor of infertility. The molecule contains a unique carbohydrate antigen that induces antibodies interfering with sperm function. However, the characteristic properties of CD52 in female reproductive tissues are not known. We examined the expression and localization of CD52 in mature expanded cumulus masses.

In vitro growth and maturation of mouse oocyte‐granulosa cell complex from cryopreserved ovaries and achievement of pup birth

Ovarian tissue banking is a feasible strategy for fertility preservation for young women after cancer treatments. Ovarian tissue, after thawing, is used for several options; orthotopic grafting (normal site), autologous heterotopic grafting and collection of ovarian follicles for culture. Recent reports of live birth encouraged clinicians and researchers to apply this technology to premature ovarian failure (POF) resulting from strong cancer therapy. Grafting, however, carries a risk of malignant cell recurrence. For safety, development of a culture method is necessary but optimum culturing conditions for less-developed follicles abundant in the ovary are not well known. In the present article, the current status of ovarian tissue cryopreservation, and in vitro oocyte growth and maturation from the preserved ovaries are reviewed.

Ovarian Tissue Banking

ABSTRACT Ovarian tissue cryopreservation is an effective method for protecting against infertility as well as preservating endangered animal species. The technique is particularly sought after as a strategy against ovarian failure caused by aggressive chemotherapy in young women with cancer. There are two uses for cryopreserved ovarian tissues after thawing: grafting and culture. Grafting carries the risk of reintroduction of disease. This article describes the status of ovarian cryopreservation in humans and the other animals and also details the successful birth of a pup from preantral follicle oocytes derived from a mouse cryopreserved ovary followed by in vitro growth, in vitro maturation and in vitro fertilization-embryo transfer (IVF-ET).