Effect of glucosamine on the development of CIOA. CIOA was induced by injection of 1 U/mouse collagenase at Day 0 and Day 2. After seven days, CIOA mice were orally treated with PBS (CIOA; n = 15), with glucosamine hydrochloride (20 mg/kg/daily; CIOA + Glu1; n = 15) or glucosamine sulfate (20 mg/kg/daily; GS, n = 10) for 20 days, or with glucosamine hydrochloride (20 mg/kg/daily) started with the second collagenase injection and lasted 20 days (20 mg/kg/daily; CIOA + Glu2; n = 10). A control group of non-arthritic mice were fed with PBS (healthy; n = 9). (a) Representative joint sections stained with H&E showed fissures and fractures in cartilage and bone matrix of CIOA mice at Day 30, attenuated by Glu1 and Glu2, but not by GS; magnification × 40. Staining with Toluidine blue (b) and Safranin O (c) demonstrated GAGs and PG loss in CIOA that was less pronounced in Glu1-treated CIOA mice; magnification × 100. Glu1 and Glu2 significantly reduced the osteophyte areas in CIOA mice, while GS was not effective (d). Data are expressed as the mean ± SD from the evaluation of five joint sections/group; Student's t-test; **P <0.01 vs CIOA group. (e) Glu1 and Glu2 significantly decreased the total histological score in CIOA mice and nonsignificantly by GS. Total histological score was calculated using the semi-quantitative grading and staging system. Data are expressed as the mean ± SD from the evaluation of 10 joints/group; Student's t-test; ***P <0.001 vs CIOA group.