SERPINE1 and arthritic joint disease: In human synovial tissue obtained from patients with OA and RA both uPA and PAI-1 mRNA expression was increased [32], and in mice with antigen-induce arthritis uPA mRNA expression in synovial tissue quickly increased and peaked around 4 h, while PAI-1 was increased in the first 3 days after induction of arthritis [19].