Nuclear pore complex proteins mark the implantation window in human endometrium

Area of Science:

• Cell Biology
• Reproductive Biology
• Histology

Background:

• Nucleolar channel systems (NCSs) are transient organelles in human endometrial epithelial cells.
• Current characterization is limited to electron microscopy, hindering their use as biomarkers.
• NCSs are found in postovulatory endometrium, a phase relevant to uterine receptivity.

Purpose of the Study:

• To develop a light microscopic method for detecting NCSs.
• To characterize the prevalence and cellular distribution of NCSs.
• To validate NCSs as potential markers for uterine receptivity.

Main Methods:

• Immunofluorescence staining using monoclonal antibody 414 targeting nuclear pore complexes.
• Microscopic examination of 95 human endometrial biopsies.
• Analysis of NCS presence, morphology, and distribution within endometrial epithelial cells.

Main Results:

• NCSs were detected via immunofluorescence in approximately 50% of human endometrial epithelial cells.
• NCSs were specific to endometrial epithelial cells across all tested cell types, tissues, and species.
• NCSs were identified within a specific 6-day window (days 19-24) of the menstrual cycle, overlapping the implantation window.

Conclusions:

• A robust immunodetection assay for NCSs has been established, enabling light microscopic identification.
• NCSs are specific to human endometrial epithelial cells and appear during a defined period of uterine receptivity.
• NCSs represent potential biomarkers for assessing endometrial receptivity and facilitating further research.