Figure 2.

Progression of MIA-induced OA on the behavioral and molecular levels.

Notes: (A) Disturbed weight bearing for the hind limbs of rats injected with 3 mgs MIA. Loading incapacitance was measured via the DWB test before MIA injection and every second day during 28 days of OA development. The bars represent body mass-normalized weight bearing difference between MIA-treated ipsilateral and non-injected contralateral hind limbs (n=12). (B, C) Alterations in gene expression of cartilage turnover markers in osteoarthritic rats during disease progression. Transcripts levels for Sox9 and Comp in joint tissue samples were measured by quantitative polymerase chain reaction. mRNA samples were collected 2, 7, 14, 21 and 28 days after OA induction. The results are normalized to Hprt1 and presented as a relative change of mRNA levels in comparison to day 2 (n=8–10). (D, E) Changes in SOX9 and COMP protein expression measured by Western blotting assay. Samples were collected before MIA injection and 2, 7, 14, 21 and 28 days after OA induction. The results are presented as fold change (mean ± SEM) in comparison to the intact group (n=5). Representative bands from each group are presented below the charts. The data were analyzed with one-way analysis of variance followed by Bonferroni’s multiple comparison post hoc test; values with p<0.05 were considered significant. *Denotes significant differences vs intact animals (before OA induction) at p<0.05, **denotes significant differences vs intact animals (before OA induction) at p<0.01, ***denotes significant differences vs intact animals (before OA induction) at p<0.005, ****denotes significant differences vs intact animals (before OA induction) at p<0.001. ^##denotes significant differences vs day 2 post-MIA injection at p<0.01, ^###denotes significant differences vs day 2 post-MIA injection at p<0.005, ^####denotes significant differences vs day 2 post-MIA injection at p<0.001, ^$denotes significant differences vs indicated bar at p<0.05, ^$$denotes significant differences vs indicated bar at p<0.01.

Abbreviations: COMP, cartilage oligomeric matrix protein; DWB, dynamic weight bearing; MIA, monoiodoacetate; OA, osteoarthritis.