Lectin-like, oxidized low-density lipoprotein receptor-1-deficient mice show resistance to age-related knee osteoarthritis

The lectin-like, oxidized low-density lipoprotein (ox-LDL) receptor-1 (LOX-1)/ox-LDL system contributes to atherosclerosis and may be involved in cartilage degeneration. The purpose of this study was to determine whether the LOX-1/ox-LDL system contributes to age-related osteoarthritis (OA) in vivo, using LOX-1 knockout (LOX-1 KO) mice. Knee cartilage from 6, 12, and 18-month old (n = 10/group) C57Bl/6 wild-type (WT) and LOX-1 KO mice was evaluated by determining the Osteoarthritis Research Society International (OARSI) score of Safranin-O stained samples. The prevalence of knee OA in both mouse strains was also investigated. Expression levels of LOX-1, ox-LDL, runt-related transcription factor-2 (Runx2), type-X collagen (COL X), and matrix metalloproteinase-13 (MMP-13) in the articular chondrocytes were analyzed immunohistologically. No significant difference was observed in the mean scores of WT (2.00±0.61) and LOX-1 KO mice (2.00±0.49) at 6 months of age (P=1.00, n=10). At 12 and 18 months of age, the mean scores of LOX-1 KO mice (3.75±0.93 and 5.50±0.78) were significantly lower than those of WT mice (5.25±1.14 and 9.00±1.01; P<0.001 in both cases; n=10). The prevalence of OA in LOX-1 KO mice was lower than that in WT mice at 12 and 18 months of age (40 vs 70%, 70 vs 90%, respectively; n=10). The expression levels of Runx2, COL X, and MMP-13 in articular chondrocytes significantly decreased in LOX-1 KO, mice compared with those in WT mice. The study indicated that the LOX-1/ox-LDL system in chondrocytes plays a role in the pathogenesis of age-related knee OA, which is potentially a target for preventing OA progression.