Osteopontin and αvβ3 integrin expression in the endometrium of infertile and fertile women

Osteopontin and its receptor αvβ3 integrin have recently been proposed as a major complex to promote embryo attachment, and thus they would be useful as markers of endometrial receptivity. In the current study αvβ3 integrin and osteopontin expression and co-expression in in-phase and out-of-phase endometrial biopsies from normal healthy women (n = 12) and infertile patients (n = 107) were investigated. Two endometrial biopsies (post-ovulatory day +6 to +8, and 4 days later) were performed during a single menstrual cycle in each subject. Oestradiol and progesterone serum concentrations were quantified on the same days as endometrial sampling. No statistically significant difference regarding αvβ3 integrin and osteopontin expression and their co-expression was found between fertile controls and infertile patients irrespective of endometria being in-phase or out-of-phase, infertility factors detected or whether patients became spontaneously pregnant or not. Although a co-ordinate high concentration of both glycoproteins on post-ovulatory day 8 onwards was observed, there was an evident lack of temporal co-expression of these markers during the implantation window. It is concluded that the functional significance of the osteopontin: αvβ3 integrin complex as a marker of endometrial receptivity and implantation potential in women seems to be untenable.