Endometrial receptivity: changes in cell-surface morphology

Area of Science:

• Reproductive Biology
• Cell Biology
• Gynecology

Background:

• Ovulation and fertilization initiate embryonic development and endometrial differentiation.
• Corpus luteum progesterone production is crucial for these processes.
• Successful pregnancy requires synchronous embryonic development and endometrial receptivity, culminating in blastocyst implantation.

Purpose of the Study:

• To investigate the morphological changes in the endometrium during the implantation window.
• To identify and characterize pinopodes as a potential marker for endometrial receptivity.
• To determine the timing and variability of pinopode formation in natural, stimulated, and artificial menstrual cycles.

Main Methods:

• Sequential endometrial biopsies were collected from women.
• Scanning electron microscopy was used to visualize endometrial surface morphology.
• Pinopode formation and timing were analyzed in relation to the menstrual cycle.

Main Results:

• Pinopodes, characterized by flower-like membrane projections, form transiently (1-2 days) during the implantation window.
• The number of pinopodes positively correlates with successful implantation.
• Pinopode formation timing varied: days 19-20 in stimulated cycles, days 20-21 in natural cycles, and days 21-22 in artificial cycles, with significant inter-individual variation (up to 5 days).

Conclusions:

• A narrow and discrete implantation window exists in humans, marked by pinopode formation.
• Pinopode detection is a promising clinical tool for assessing endometrial receptivity.
• Understanding pinopode dynamics can aid in optimizing fertility treatments and improving pregnancy outcomes.