Time sequence of VE-cadherin movement on human umbilical vein tissue during PMN transmigration.

A PMN (stained with FM 1-43, red) was transmigrating through living human umbilical vein tissue that was previously immunostained with VE-cadherin antibody (Alexa Fluor 488, green). The PMN transmigration site (triangle) was located at the boundary between 2 adjacent endothelial cells. This PMN was originally located on top of the vascular endothelium at 0 minute and displayed as a faint red image in panel A (arrowhead). It was already underneath the vascular endothelium at 2 minutes (I-K). (D,H,L) These panels are black-and-white pictures from depth-combined VE-cadherin images obtained at 0 minute, 1 minute, and 2 minutes, respectively. VE-cadherin clusters surrounding the transmigration site moved to opposite ends at 1 minute (E-H) and moved back to their original locations at 2 minutes (I-L). When this PMN transmigration process was completed, the resealed bicellular boundary was essentially the same as before (compare D and L). After transendothelial migration, this PMN moved laterally underneath the vascular endothelium without penetrating deeply into the smooth muscle layers. Its location (arrow) was about 80 μm away from the transmigration site at 8 minutes (M-P).