The content of the following proteins tended to be increased in tendinopathy: aggrecan (3 positive studies out of 4), fibronectin (3 of 3 studies), tenascin C (TNC) (2 of 3 studies), cyclooxygenase (COX)-2 (3 of 3 studies), collagen I (11 of 15 studies) and III (13 of 14 studies), MMP-1 (6 of 12 studies), -9 (7 of 7 studies), and -13 (4 of 7 studies), TIMP-1 (4 of 7 studies), and vascular endothelial growth factor (VEGF) (4 of 7 studies). The gene discussed is ACAN; the disease is disease of the tendon.