Cell and material interactions: adhesion. (A) Integrin-blocking assay revealed that RGD-dependent vacuolation and lumen formation within AHA hydrogels are regulated by α_Vβ₃ and α₅β₁ integrins, but not by α₂β₁ integrins. (B) Real-time RT-PCR analysis reveals fibronectin expression of encapsulated ECFCs and confocal analysis detected some fibronectin deposited within the synthetic matrix (fibronectin in green; actin in red; nuclei in blue). (C) Confocal analysis revealed the membrane localization of MMP-1, and MMP-2 (both in green; actin in red; nuclei in blue) in the branching and sprouting ECFCs. Significance levels were set at: #P > .05, *P < .05, and **P < .01. Scale bars are 20 μm.