Pinopodes as markers of endometrial receptivity in clinical practice

Clinical evidence indicates the existence in the human of a narrow window o f uterine receptivity which opens during the mid-luteal phase. At the same time, formation of pinopodes on the apical membranes of the endometrial epi thelial cells occurs. To develop a specific marker for receptivity in clini cal practice, the kinetics of pinopode formation has been,investigated thro ugh sequential endometrial biopsying in natural, hormone replacement and st imulated cycles. The results show that pinopodes last <48 h in all cycles, and the timing of their formation depends both on the hormonal treatment ap plied and on the patient's individual response. On average, pinopodes form earlier in stimulated cycles and later in hormone replacement cycles, compa red with natural cycles. Pinopode expression is strongly correlated with im plantation following embryo transfer and furthermore, detection of pinopode s in assessment cycles may be extremely useful for the assessment of recept ivity on an individual basis to optimize embryo transfer, resulting in incr eased implantation rates. Finally, pinopodes seem to be correlated well wit h other cellular and molecular events occurring in the mid-luteal endometri um.