137 THE EFFECT OF ANTI-CD44 ON EMBRYO IMPLANTATION IN RABBITS

Abstract

Cellular adhesion molecules are thought to be responsible in embryo attachment in human and animals. Blastocyst attachment to the lining of the mammalian uterus during early implantation involves the initial apposition of the trophoblast to the uterine epithelial surface. A number of cell surface molecules have been implicated in the initial attachment reaction between trophectoderm and maternal surface epithelium, these include heparin-binding epidermal growth factor (HB-EGF), trophinin, CD44, integrins and extra cellular matrix molecules such as osteopontin (OPN) each of which exhibit elevated levels of expression at the time of implantation. CD44 is a membrane glycoprotein that is present in a variety of isoforms and is considered to be the major cell surface receptor for hyaluronan. The aim of these work was to study the effect of CD44 on embryo implantation. The rabbit is potentially an excellent model for study of implantation because it is an obligate ovulator, and therefore pregnancy can be precisely timed. Adult New Zealand rabbit females (n = 12) were naturally inseminated with a buck of proven fertility. The day of coitus was counted as ‘Day 0’ of pregnancy. To determine the effect of CD44 at the time of implantation, the animals were divided in three groups: group A (four animals): received 100 μg of anti-CD44/mL in an intraperitoneal injection on day 4.5 of pregnancy; group B (four animals), via mid-ventral laparotomies on day 6.5 p.c animals received an injection of 20 μg of anti-CD44 on the right horn (0.5 mL each, from the ovarian end to the cervix). All these treatments were performed in the right horn. Each animal served as her own control with the left uterine horn receiving 0.5 mL of saline. Group C (four animals): This was the control group; two animals received an injection of 2 mL of saline and the other two received 0.5 mL of saline in each uterine horn. Finally, each animal was sacrificed on Day 10 of the pregnancy, the uterus was removed, and the number of implants were counted in each uterine horn. In the group A: a mean of 4.5 ± 0.47 s.e.m implants were found in the right and on the left side. In group B, a profound reduction in implantation sites was found with the anti-CD44 injected into the uterine horn, a mean of 0 implants in the right uterine horn compared with 3.5 implants on the left side P < 0.0001. Group C showed 4.25 implants on the right horn and 5.5 on the left horn; no statistical differences were found. Conclusion: the intraperitoneal injection of the anti-CD44 slightly reduced the number of embryos implanted but this reduction was not statistically significant. Anti-CD44 injected intrauterine affected seriously the embryo survival at the time of implantation.