The role of adhesion molecules in implantation

Implantation is a biologic phenomena which requires a communication between two different organisms and consists of three consecutive phases: apposition, adhesion and invasion. This first social and physical interaction between the embryo and the endometrium is a paradox that the reproductive medicine has not yet been resolved. The most curious aspect of implantation is that at first sight, it occurs under the control of hundreds of molecules and mechanisms which have not been clearly described. Adhesion molecules represent the most interesting and most complicated aspects of this matter. The aim of this study is investigate the effects of adhesion molecules which play a role during the endometrial receptivity and implantation stages in rat endometrium. With this purpose, female rats (n=20) at the fifth, sixth, and seventh gestational days were sacrificed (experimental gorup) to study the period of implantation. Histological studies revealed that the first decidual reaction was observed on the fifth pregnancy day. TGF-oc, laminin, collagen IV, fibronectin, integrin oc3, ocv, pi were stained strongly during the sixth day of pregnancy that was considered to be the receptive period in the enlarged desidual reaction regions. During the seventh day that was considered to be the implantation period, increased immunoreactivities of laminin, oc3, pi, TGF-oc, IL-ip and TNF-oc in the epithelium of endometrium and trophoblast cells were observed. While immunoreactivity of MUC-1, an anti-adhesive molecule, was observed strongly in the normal uterus epithelium, it was decreased on the sixth day, and disappeared on the seventh day. In conclusion, the decidualization process just begins on the fifth day of gestation and laminin, collagen IV and fibronectin that has observed to be intensively expressed in this region on the sixth day may play a major role in the proliferation of decidual cells. MUC1 molecule which is strongly expressed in the non-pregnant uterus has decreased on the sixth day and allowed the release of the adhesion molecules enabling the attachment of the embryo. While adhesion molecules of laminin collagen IV, fibronectin, integrin oc3, ocv and pi play an important role in the adhesion phase, TGF- oc, collagen IV, IL-ip and TNF-oc display function in the invasion phase.