Figure 4. HUVEC-MSC interactions require the α₆ integrin subunit.

(a) Capillary networks were formed by HUVEC (red) and MSC (green) co-cultures and allowed to mature for 7 days. (b) Two days after incubating the cultures containing intact capillary networks with an anti-α₆ integrin antibody, the association of MSCs with the capillary networks was disrupted. Scale bar = 50 μm. (c) The percentage area occupied by MSCs near and around capillaries was quantified in control cultures at day 7, 9, and 11, and compared to cultures incubated with anti-α₆ integrin antibody (GoH3) for each time point. A total of 10 fluorescent images were quantified per condition (*** p < 0.001). (d, e) Phase contrast images from day 3 HUVEC-MSC co-cultures within MFDs in the absence (control, left) or presence (right) of the anti-α₆ integrin antibody show that blocking α₆ integrin also prevents the recruitment of MSCs to the perivascular niche. Capillary networks were formed in the gels channels on the left side, and MSCs cultures were initiated on the right. Anti-α₆ integrin antibody was added to main channel on the right-hand side only, proximal to the MSCs. Scale bar = 100 μm.