Does the Arg-Gly-Asp (RGD) adhesion sequence play a role in mediating sperm interaction with the human endosalpinx?

BACKGROUND Sperm from several species, including the human, make direct contact with the endosalpinx. Although this is known to be beneficial to sperm function, the specific mechanisms mediating the adhesion are poorly understood. METHODS Short linear oligopeptides containing the amino acid sequence Arg-Gly-Asp (RGD) or a scrambled sequence (GRGES) were incorporated into an established sperm-endosalpingeal binding assay. In addition, the ability of fluorescent latex beads coated with an RGD oligopeptide to bind specifically to sperm and/or epithelium was also determined. RESULTS Significantly fewer sperm associated per field of isthmic epithelium in the presence of 62.5 micro mol/l GRGDTP (1.18 +/- 0.41; mean +/- SEM, P < 0.05) and 250 micro mol/l RGDV (1.17 +/- 0.29; P < 0.01) compared with the control incubation (3.34 +/- 0.45). There was no difference in sperm binding to ampullary epithelium in the presence of any of the oligopeptides tested. Moreover, no beads were observed bound to sperm whereas significantly more RGD-coupled beads bound to isthmic epithelium compared with ampullary epithelium (1.47 +/- 0.26 versus 0.72 +/- 0.16 P < 0.01) and this increased in a dose-dependent manner. CONCLUSIONS These findings indicate that the recognition between the RGD sequence and integrin receptors may contribute to the interaction between sperm and the human endosalpinx in the isthmic but not in the ampullary region of the uterine tube.