ObjectiveTo investigate the effects of icariin (ICA) on serum bone turnover markers expressions and histological changes of cartilage and subchondral bone in mouse osteoarthritis (OA) model.MethodsEighty 8-week-old male C57BL/6J mouse were randomly divided into 8 groups (n=10). The OA model was established by anterior cruciate ligament transaction (ACLT). Group A: sham operation/early-stage normal saline administration; group B: sham operation/early-stage ICA administration; group C: ACLT/early-stage normal saline administration; group D: ACLT/early-stage ICA administration; group E: sham operation/late-stage normal saline administration; group F: sham operation/late-stage ICA administration; group G: ACLT/late-stage normal saline administration; group H: ACLT/late-stage ICA administration. Each animal received either ACLT or simply opening joint capsule, respectively. For groups B and D, ICA was given by gavage [10 mg/(kg·day)] on the first day after ACLT. For groups F and H, ICA was given with the same volume at 4 weeks after operation. The blood serum of the mouse was collected and prepared at 8 weeks after operation. Serum bone turnover markers and cytokines, including C-telopeptide of type I collagen (CTX), osteocalcin (OC), interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and IL-1β, were measured by ELISA. Tissue samples from the knee were stained by alcian blue/hematoxylin & orange G (AB/H&OG). Histological changes of cartilage and subchondral bone were observed and evaluated by Osteoarthritis Research Society International (OARSI) scoring system.ResultsComparison between each group with early-stage administration (groups A, B, C, and D): Compared with groups A and B, the levels of CTX and OC in group C were significantly reduced (P<0.05); the levels of IL-6, TNF-α, and IL-1β and OARSI score was significantly increased (P<0.05). Compared with group C, the levels of CTX and OC in group D were significantly increased (P<0.05); the level of IL-6 was significantly reduced (P<0.05); the levels of TNF-α and IL-1β were not changed (P>0.05), and OARSI score was significantly reduced (P<0.05). Histological observation showed that the tibial cartilage loss was significantly improved. Comparison between each group with late-stage administration (groups E, F, G, and H): Compared with groups E and F, the levels of CTX and OC in group G were significantly reduced (P<0.05); the levels of IL-6, TNF-α, and IL-1β and OARSI score were significantly increased (P<0.05). Compared with group G, the level of CTX in group H were increased (P<0.05); the levels of OC, IL-6, TNF-α, and IL-1β and OARSI score were not changed (P>0.05). Histological observation showed that the tibial cartilage loss had no changes after late-stage ICA administration.ConclusionICA plays protective effects on subchondral bone, hyaline, and calcified cartilage. Meanwhile, ICA can improve bone remodeling in subchondral bone of OA to some extent. The consistent changes of serum bone markers and pathological morphology suggest that early intervention of ICA on OA is more effective.