Wrapping HUVECs reorganize pericytes on host vessels. (A) Pericytes (blue, NG2 staining) appear normal around unwrapped, intact host vessels (row 1). Wrapping by HUVECs dramatically changes pericyte morphology (rows 2-4), but pericytes around maturing HUVEC vessels appear more normal (row 5). “Box 1” and “Box 2” show details of the areas within the white boxes in the “Wrapped host” panel. Empty and filled arrowheads highlight unwrapped and wrapped regions, respectively. Note that the disruption of host pericytes requires complete and tight wrapping by the HUVECs, not casual alignment as shown on the host vessel with empty arrowheads in “Box 1.” Whole-mount IHC stain; 60×/1.1 NA oil objective (rows 1, 3, 4 and 5) and 20×/0.95 NA water objective (row 2); scale bar represents 120 μm for row 2 and 40 μm for all the other rows. (B) When wrapping around host vessels (blue, mCD31 staining), HUVECs (green, GFP transduction) often lay on top of pericytes (red, NG2 staining) with little colocalization between the 2 (ie, very few pixels are yellow in the “Merged” panel). Filled arrowheads indicate where wrapping is taking place. Note that pericyte morphology on the wrapped host vessel is more abnormal in “Spot 2.” Whole-mount IHC stain; 20×/0.95 NA water objectie at 4.0× digital zoom; scale bar represents 30 μm.