Synchronous Expression of Pinopodes and Alpha V Beta 3 and Alpha 4 Beta 1 Integrins in the Endometrial Surface Epithelium of Normally Menstruating Women During the Implantation Window

Objective: To use histology, scanning electron microscopy (SEM) and immunohistochemistry to examine the expression of pinopodes, and alpha v beta 3 and alpha 4 beta 1 integrins in the same endometrial biopsies.

Study Design: A prospective observational study. Fifteen consecutive regularly menstruating women with normal hormone profiles were followed for detection of ovulation and then biopsied twice, on postovulatory days luteinizing hormone (LH) +6 and LH +8. Measurements included abundance and development stage of pinopodes and a semiquantitative assessment of intensity of antibody staining for integrins.

Results: All biopsies observed under light microscopy showed an in-phase endometrium. Pinopodes were found developing mostly on day LH +6 and were fully developed on day LH +8. The expression of alpha v beta 3 dimer increased significantly from day LH +6 to day LH +8, while alpha 4 beta 1 dimer did not show any significant change during the same period. Fully developed pinopodes and strong intensity of alpha v beta 3 integrin were the most common findings.

Conclusion: These results indicate a coordinated, synchronous change in morphology and adhesion molecule expression of endometrial epithelial cells on day LH +8 of a normal menstrual cycle.