Spiral Arteriole Remodeling In Rat Deep Placenta Bed: The Progression Changes Of The Early, Trophoblast-Independent Vessel Remodeling.



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In early pregnancy, maternal uterine vessels carrying blood to the placenta are modified to support the development of the placenta. Vessels expand as their walls become disorganized. Trophoblast replaces the original vessel wall. To better understand vessel remodeling, we analyze the changes of the cell type in the vessel wall and categorize those changes. The rats’ uterine vessel remodeling stages of histology sections are defined as follows. (1) Unremodeled vessels have organized endothelium and thick media (>10 um). (2) In early remodeling, the media thinned (5-10 um) and endothelium swollen and protruded into the vessel lumen. (3) The endothelium was monolayer, the media layer was 1-5um or discontinuous, and fibrinoid appeared around the vessel’s periphery. (4) Trophoblasts were replacing the smooth muscle. The average vessel diameter increased throughout the stages with large variability. The immunohistochemistry section has one more stage with trophoblast fully around the vessel and media starts to break down at stage 2. In conclusion, arterioles' smooth muscle and endothelium start to remodel at the same time, well before embryonic tissue (trophoblast) is present. This study helps us understand the sequence of changes during remodeling. Future studies will investigate the maternal factors acting in this remodeling.



Reproductive biology, Placenta, rat, blood vessel, trophoblast, Smooth muscle