Phase-contrast images were acquired on a Zeiss microscope (Axiovert 25) at 10x (NA 0.25) or 20x (NA 0.3) magnification, using a Zeiss CCD camera (Axiocam MRC) and Zeiss Mr. Grab 1.0 software. Quantification of cell area and circularity was performed using Fiji/ImageJ (version 1.52e).
For confocal microscopy of fixed cells, cells were prepared on coverslips as previously described [39] , and images were acquired on an inverted confocal microscope (Leica AOBS or SP8) using 20x (NA 0.7) dry, 40x (NA 1.25) oil, and 63x (NA 1.32) oil objectives (Leica). Images were processed using Leica Application Suite X and Fiji/ImageJ (version 1.52e) software.
For confocal microscopy of sprouting assays, fibrin gels with beads were permeabilized for 5 mins in 0.5% Triton X-100, and blocked in 5% BSA in PBS containing 1 mM CaCl2 and 0.5 mM MgCl2 for 2 h at RT. Afterwards the gels were washed 3 times with PBS++ and DAPI and phalloidin were incubated overnight at 4 °C. The following day the gels were washed 3 times with PBS++ for 10 min. The beads were visualized using a 25x long-distance water objective on a Leica SP5 confocal microscope, creating z-stacks of 1.5 µm per slice, resulting in 150-200 slices per bead. A maximum projection of the image stacks was created using Fiji/ImageJ.
For confocal microscopy of fixed cells, cells were prepared on coverslips as previously described [39] , and images were acquired on an inverted confocal microscope (Leica AOBS or SP8) using 20x (NA 0.7) dry, 40x (NA 1.25) oil, and 63x (NA 1.32) oil objectives (Leica). Images were processed using Leica Application Suite X and Fiji/ImageJ (version 1.52e) software.
For confocal microscopy of sprouting assays, fibrin gels with beads were permeabilized for 5 mins in 0.5% Triton X-100, and blocked in 5% BSA in PBS containing 1 mM CaCl2 and 0.5 mM MgCl2 for 2 h at RT. Afterwards the gels were washed 3 times with PBS++ and DAPI and phalloidin were incubated overnight at 4 °C. The following day the gels were washed 3 times with PBS++ for 10 min. The beads were visualized using a 25x long-distance water objective on a Leica SP5 confocal microscope, creating z-stacks of 1.5 µm per slice, resulting in 150-200 slices per bead. A maximum projection of the image stacks was created using Fiji/ImageJ.