a, mRNA levels of putative oxysterol-binding nuclear receptors in chondrocytes treated with IL-1β, TNFα, cholesterol, 25-HC or 7α,25-HC for 36 h (n = 5), in damaged regions of cartilage from humans with OA (versus undamaged regions; n = 4), and in cartilage from DMM-operated mice (versus sham-operated mice; n = 5). b, RT–PCR and qRT–PCR (n = 5) analyses of ROR isoforms in chondrocytes treated with IL-1β or TNFα for 36 h. c, d, Representative immunostaining images of RORα and RORγ in damaged and undamaged regions of cartilage from the same patient (c; n = 10) and sham- or DMM-operated mice (d; n = 7). e, Left, saturation fluorescent polarization assays assessing the binding of 22-NBD cholesterol (200 nM) to increasing amounts of full-length recombinant RORα protein. Right, competition fluorescent polarization assays to determine the competition of the indicated concentrations of cholesterol, 25-HC, and 7α,25-HC with 22-NBD cholesterol (200 nM) for binding to full-length recombinant RORα protein (5 nM; n = 4). f, qRT–PCR analysis of the indicated molecules in chondrocytes infected with Ad-RORα (n = 5). g, ChIP assays for RORα binding to the promoter of each target gene in chondrocytes infected with 800 MOI of Ad-C (C) or Ad-RORα (R) (n = 5). Means ± s.e.m. with two-tailed t-test (a) and with one-way ANOVA and Bonferroni test (b, f). n indicates the number of biologically independent samples, mice per group, or human specimens. Exact P values (for P < 0.001) can be found in the accompanying Source Data. For gel source data, see Supplementary Fig. 1. Scale bars, 25 μm.