Histology of PCA. Tissue was fixed at initial harvest (freshly isolated), and after 12 days culture in the bioreactor following pre-treatment with vehicle control (agarose gel, VEH), collagenase, elastase, or both in combination (CCE). Purple indicates elastin fibres; brown indicates α-SMA-positive regions. L = lumen, M = media, A = adventitia. Low power (× 50 magnification) images of (A) freshly isolated PCA and (B) VEH, scale bars = 200 μm. Higher power magnification (× 100) of PCA pre-treated with (C) VEH, (D) collagenase, (E) elastase and (F) CCE, scale bars = 200 μm. Arrowheads in (E) and (F) indicate sparse areas of preserved, thinned elastin.