Uterine Pinopodes in Spontaneous and Artificial Cycles: Relationship to Implantation Window (IW)

Background: The implantation window (IW) may be altered under different conditions. In oocyte donation (OD), where manipulation of hormones is possible implantation rates (IR), are higher. Pinopodes are protrusions of the apical surfaces of the uterine luminal epithelium, reported by Psychoyos and Nikas (Asst. Reprod Rev 4:26-32, 1994) to appear on Cycle Day (D), 19-20 in spontaneous cycles, (SC). The aim of this study was to investigate whether the pinopodes can serve as markers for the IW (D 19-21) and determine possible differences between spontaneous vs. artificial cycles, (AC), of patients undergoing OD. Methods: Endometrial biopsies (EB x ) were obtained from 13 oocyte recipients twice during Mock cycles on D 20 and D 26. They received Estrace 2, 4, 6 mg/d as of D 1-7, 8-11, 12-14, and on D 15 started 50 mg progesterone. Sixteen SC infertile women were also evaluated and had EBx on D 20 (LH+6) and D 26 (LH+12). The EB x were obtained by Pipelle (Prodimed, France) A portion was fixed in 2.5% glutaraldehyde in 0.1 phosphate buffer for Electon Microscopy (EM) and the rest for histological study to evaluate endometrium for being in or out of phase, (Noyes Criteria)Results:On D 20 pinopodes are present in 75% of SC and only 25% of AC. By histologic evaluation 25% of SC are in phase while none of AC. These data can be interpreted as suggesting a delay in the IW which may be the reason for higher implantation rates in AC of oocyte donors. Conclusion: The data support the idea that pinopodes may be markers of IW since they appear on D 20 in most SC. The results suggest that IW may be chronologically shifted possibly accounting for higher pregnancy rates in OD where AC are used