EphrinB is phosphorylated at sites of contact between endothelial cells and MSC. (A) Cell surface and interior rendering of representative confocal images showing MSC (red) contacting HUVEC (green), and p-EphrinB (white) at points of contact between HUVEC and MSC after 1-hour incubation on Matrigel. Subpanels iii and iv are the result of clipping to show the cell interior. (B) Representative microscopy images from H&E staining of a sectioned Matrigel plug (oval structure limited by a drawn black line), showing vessels containing remnants of red cells (red structures) and the overlying skin (original magnification ×1.2); and fluorescence immunostaining of human CD31 and p-EphrinB in sequential sections from the boxed area within the Matrigel plug containing HUVEC and GFP-MSC retrieved from the mouse after 7 days (original magnification ×20). (C) Three-dimensional rendering of confocal images from 2 segments of the boxed vessel wall in panel B showing the relationship between CD31⁺ endothelium, GFP-labeled MSC, and p-EphrinB. Images reflect clipping and rotation to show relationships between cell types and p-EphrinB. Scale bars in panels A and C represent 50 μm.