Alphavbeta3 Integrin Expression and Pinopod Formation in Normal and Out-of-phase Endometria of Fertile and Infertile Women

Background: There is scanty and contradictory information regarding the comparison of traditional histological dating criteria of the endometrium with the expression of the new markers of endometrial receptivity such as alphavbeta3 integrin and pinopods. Also, definite data with respect to the potential correlation existing between these different new markers in defining the putative window of implantation are lacking.

Methods: The temporal relationship between alphavbeta3 integrin expression and pinopod formation in normal and out-of-phase endometrial biopsies from normal healthy women (n = 12) and infertile patients (n = 36) was investigated. Two endometrial biopsies (postovulatory day +7 to +8 and 4 days later) were performed during a single menstrual cycle in each subject. Estradiol and progesterone serum concentrations were quantified on the same days as endometrial sampling.

Results: No statistically significant difference regarding alphavbeta3 integrin expression, pinopod formation, and hormone concentrations was found between fertile controls and infertile patients irrespective of endometria being in-phase or out-of-phase. Although a coordinate high level of expression of alphavbeta3 integrin and pinopod on postovulatory days 7-8 was observed, there was an evident lack of temporal co-expression of these markers over the luteal phase in the endometrial samples investigated.

Conclusions: There is a clear dissociation in the temporal expression of the most cited markers postulated to frame the window of implantation. The functional significance (if any) of these new markers remains to be established.