Fig. 1

Dynamic biogenesis and release of EVs in the endometrial luminal epithelium during early pregnancy. Upper panel: Schematic representation of the superficial endometrium. The uterine luminal epithelium is composed of a population of polarized cells. The apical surface of luminal epithelial cell faces the uterine lumen. The basal lamina is located close to the complex stromal compartment, which is filled with different cells and structures, including stromal cells, blood vessels, and glands. Left panel: Cross sections of luminal epithelium on day 12 of pregnancy showing tall columnar epithelial cells with well-developed microvilli on the apical surface. A A large population of EVs (yellow arrows) docking on the microvilli was observed. B MVBs (black arrows) were located at the apical site of the cell. MVBs contained inside a population of heterogeneously sized EVs (higher magnification). Right panel: Cross sections of luminal epithelium on day 16 of pregnancy show tall columnar epithelium with well-developed microvilli. C Characteristic secretory areas, containing vesicles were located close to the desmosome at the apical site of the luminal epithelial cells. D EVs (yellow arrows) were still docking on the microvilli. E MVBs (black arrows) were found at the apical site of the cell, fused with the plasma membrane. MVBs contained inside a population of EVs ready to be released into the extracellular space (higher magnification). AS – apical surface, BL – basal lamina, BS – basal surface, BV – blood vessel, D – desmosome, DP – day of pregnancy, G – Golgi apparatus, L – lysosome, LE – luminal epithelium, M – mitochondria, MV – microvilli, MVBs – multivesicular bodies, N – nucleus, PM – plasma membrane, RER – rough endoplasmic reticulum, SA – secretory areas, SER – smooth endoplasmic reticulum, ST – stromal cell, TJ – tight junction, TGN – Trans Golgi network, Vs – vesicles