Immunofluorescence staining of CD31, an EC marker, on both surface layers (~90μm thickness on each side), middle core sections (~400 μm thickness) of the valve tissue; 1^st row: Static Controls; 2^nd row: Flex; 3^rd row: Flow; 4^th row: Flex-Flow conditioning; 5^th row: porcine heart valve as Positive control.

<p>Among the experimental groups, CD31-expressing cells were visible within the superficial layers (top and bottom layers) of the engineered tissues, in solely the flex flow group. b) Quantification of positive staining (green; from images in part a) for CD31signal-intensity in four experimental groups; Samples exposed to flex-flow expressed a significantly higher level of positive CD31 (p < 0.05) in comparison to the control group. PHV was treated as the positive control.