Figure 5

Vessel loops with scarce interendothelial contacts, open lumens, and intravascular pillars. Pillars (arrows) are covered by CD34⁺ ECs (corresponding to the inner layer of the loop) and show a core whose connective content (collagen, pericytes and interstitial cells) depends on pillar size. The loop open lumen (LP) is connected to that of the mother vessel (v) and surrounds an ITS (A,B). Nascent pillars are also observed (C and J, arrowhead). Note that pillars/ITSs are isolated in the vessel lumen (H and I, arrows) or adhered to the vessel wall, with a planar (F) or meso-like morphology (G), or to other pillars/ITSs, arranged linearly or grouped irregularly (J,K). The zones of adherence are shown at higher magnification in inserts of (J,K) (arrows). Double-staining with anti-CD34 (brown) and αSMA (red). Bar: (A–K) 8 µm.