Effect of slab detachment day on vasculogenesis and microvessel alignment. (A-D) Representative images of CD31 stains (red) of thick longitudinal sections of slabs cultured in defined medium that were never detached and harvested at day 3 (A), or that were detached at day 1 (B), day 2 (C), or day 3 (D) and harvested at day 6. The long axes of the slabs are vertical. PCs are green and nuclei are blue. Scalebars = 100 μm. (E-G) Measures of slab compaction (width at the middle of the slab; E), fibrin fibril alignment (birefringence; F), and microvessel alignment (anisotropy index; G) indicated that all of the detached slabs compacted and that both the fibrin and the microvessels became aligned. (H-J) Measures of microvessel properties, including total microvessel length per area (H), average structure length (I), and PC recruitment (J), suggested that the aligned microvascular networks present in the slabs detached on day 3 were equivalent to those of the day 3 controls. *p < 0.05. $p < 0.05 in comparison to the control.