Porcine aortic valves demonstrate altered expression of HA homeostatic markers with age. Expression patterns of HAS2 (A1–4), HYAL1 (B1–4), KIAA1199 (C1–4), CD44 (D1–4), RHAMM (E1–4), TSG6 (F1–4) and pERK1/2 (G1–4) in valves classified as young (1–3 month old), adult (6–9 month old) or aged (>2 year old) are shown. Arrows and arrowheads denote cell and ECM expression respectively. Parentheses mark the regions of expression. †: vs young p<0.05; ‡: vs adult p<0.05. f, fibrosa; s, spongiosa; v, ventricularis. The orientation provided by the use of f, s, v in panels A-D apply to all the microscopic image panels in this figure. Scale bar: 200 μm.