Fig. 1

Evaluation of AIA in rats. a, b Representative photos of non-injected (left) hind paw on day 26 after induction (a, Normal; b, AIA). c The changes of secondary hind paw swelling on different time points. d, e Typical histopathological photos of knee joint sections with HE staining (×100; d, Normal; e, AIA). In the HE fig. of knee joint from AIA rats, typical pathological characteristics resembling RA including synovial hyperplasia (dotted arrow), cartilage damage (arrow), vascular proliferation (*) and excessive inflammatory cell infiltration could be apparently found. f Results of pathological assessments on knee joint damage for every pathological index including synovial hyperplasia, cartilage damage, vascular proliferation and inflammatory cell infiltration. Data are mean ± SEM (n = 15). ^** p < 0.01 compared with the normal group