The expression of alpha(v) and beta(3) integrin subunits in the normal human Fallopian tube epithelium suggests the occurrence of a tubal implantation window

The co-expression of alpha(1)beta(1), alpha(4)beta(1) and alpha(nu)beta(3) integrins in the human endometrium coincides with the implantation window T he alpha(nu)beta(3) integrin is expressed in the apical surface of the lumi nal epithelium and may serve to anchor trophoblast cells in the adhesion ph ase of implantation. Using immunohistochemistry, we compared the expression of alpha, alpha(1), alpha(4) and beta(3) integrin subunits in samples of n ormal human Fallopian tube and endometrium obtained from five women in the non-receptive period (luteal phase days 2-4) and from another five women in the receptive period (luteal phase days 6-8), The staining was quantified visually on a scale of 0 to ++, according to the intensity and density of s tained cells. The alpha(nu) subunit is expressed in the Fallopian tube epit helium during both periods in a pericellular distribution. The beta(3) subu nit is also expressed in the same location, but it is up-regulated during t he period of endometrial receptivity, The other subunits are expressed in l ocalizations which are not relevant to trophoblast adhesion and exhibit lit tle or no difference in the level of expression between the non-receptive a nd receptive periods. Based on these results we postulate that the expressi on of the beta(3) subunit in the human tubal epithelium is under the same s ystemic controlling signals as in the endometrium and that the normal tubal epithelium may have an implantation window, at about the same time as the endometrium, that affords the opportunity for trophoblast attachment should a 5-7 day embryo be unduly retained in the tube.