Immunohistochemical expression of endometrial L-selectin ligand is higher in donor egg recipients with embryonic implantation.

Objective: To correlate L-selectin ligand (LSL) expression in human endometrium with embryonic implantation.

Design: Retrospective cohort analysis.

Setting: University-based fertility center.

Patient(s): Donor egg recipients (DERs) who underwent programmed hormonal replacement for ET with prior mock cycle luteal phase endometrial biopsy.

Intervention(s): Immunohistochemical expression of LSL using MECA-79 antibody was examined. Slides were scored with a new scoring system, the IHC-Level (range 0-4) as follows: strength of staining-absent (0), weak (1), or strong (2); plus distribution of staining-absent (0), <50% of tissue (1), and >50% (2). Cellular apex and cytoplasm were scored independently in both the endometrial glandular and surface epithelium.

Main Outcome Measure(s): Endometrial LSL expression in pregnant versus nonpregnant patients.

Result(s): MECA-79 IHC-Level of the apex of surface epithelium was significantly higher for pregnant versus nonpregnant DERs (3.8 vs. 3.4). When controlling for embryo morphology, there continues to be a significant difference in apex score on surface epithelium (3.8 vs. 3.3, respectively). The new scoring system results correlated with an established scoring system, the HSCORE.

Conclusion(s): We demonstrate significantly higher expression of LSL at the apex of human endometrial surface epithelium obtained from DERs with embryonic implantation. Furthermore, we present the IHC-Level, a method of evaluating immunohistochemistry that may be applied to other markers of endometrial receptivity.