FIG. 4.

Microvascular network recruitment to islets. (A) Progression of microvascular network formation around a rat islet day by day. Cells were evenly dispersed in the gel immediately after seeding, and gradually formed a mostly interconnected network by day 5, assembling around the islets. Two million RFP-HUVECs were cocultured with AT-MSCs at a 5:1 ratio in a fibrin gel with integrated GFP rat islets. Scale bars, 200 μm. (B) Confocal image of microvascular network surrounding an islet after 5 days of culture. For projections, see Supplementary Video S2A and B. Scale bar, 100 μm. (C) Distribution of vascular network coverage immediately around islets at days 1 and 4. For analysis of network area coverage around islets, the regions that were analyzed contained the islet and the area extending 100 μm from the islet boundary. FIJI was used to automatically threshold and analyze the images. The vascular density around the islets increased significantly from day 1 (12.3% ± 0.5%) to day 4 (20.0% ± 0.9%) (p-value <0.00001, N = 37 islets). Red horizontal lines indicate vascular area coverage throughout the entire fibrin gel, this change was not significant. (10.9% ± 0.35% and 12.7% ± 1.06% at days 1 and 4, respectively. p-value <0.065699, n = 6 gels.) ***p < 0.001.