Characterization of collagen-induced arthritis (CIA) in wild-type and APP/PS1 mice. (A) Wild-type (Tg-) and APP/PS1 (Tg+) mice were subjected to injection with vehicle (Tg-vehicle, n = 16; Tg+ vehicle, n = 14), or with CII in CFA (Tg-CIA, n = 18; Tg+ CIA, n = 22) to induce CIA. Edema was observed at the right hind paw, which received the second injection of CII in CFA and was measured at indicated time points after injection. *, significant difference from relevant control. (B) ELISA of plasma IL-1β and TNF-α over 4 weeks after second injection with vehicle or CII in CFA in wild-type mice (n = 6 per group). (C) Bright-field photomicrographs showing ankle joints stained with hematoxylin and eosin in 6-month-old wild-type mice treated with vehicle (top row) or CIA (bottom row): left, low power of ankle joint (Arrows, bone; Scale bar = 2 mm); middle, high power of cartilage (Arrow heads, chondrocyte; Scale bar = 50 μm); right, high power of synovium (Scale bar = 200 μm). Note severe bone erosion, degradation of cartilage and chondrocytes, and intensive proliferation of synovial tissue in ankle joint 4 months after injection of CIA.