SPP1 and arthritic joint disease: In addition, overexpression of OPN has been described in several basic inflammatory processes, such as arthritis [23], myocardial remodeling after infarction [24], kidney interstitial fibrosis after obstructive uropathy [25], wound healing [26], and several types of cancer [27], where it is demonstrated that OPN gene polymorphism and OPN levels play important roles in immune- and inflammatory-mediated diseases, including AS.