HUVEC only morphologies in collagen hydrogels. A-D CD31 immunofluorescence images showing EC morphologies (CD31=green, DAPI=blue) at day 7 (a) and day 14 (b) (scale bar=100 μm). C-E show higher magnification images of different morphologies, multipolar (C –day 7), flattened (D-day 14), cobblestone (E- day 14) F: Cell height was quantified using confocal images. G: Cell morphologies were quantified at day 7 and 14, ⁎p<0.05, error bars=s.d. H: Confocal images of the distribution of cells at day 7 (upper panel) and day 14 (bottom panel). Images taken 33 um close to the ventral surface of a 3 mm thick collagen hydrogel.