E-Poster Presentation ESA-SRB-ANZBMS 2021

Osteoarthritis (OA) is associated with tissue damage and loss of function, which can be observed in preclinical studies. One OA mouse model, a single intra-articular injection of bacterial collagenase, can lead to matrix depletion in the femorotibial joint. An acute inflammatory response starts immediately; however, onset and progression of structural changes has not been described. The aim of this study was to investigate bone structure changes during OA progression using a collagenase-induced OA mouse model and micro-computed tomography (microCT). A single intra-articular injection of bacterial collagenase solution was used to induce OA in the knee joint of C57Bl/10 mice (n=48 OA and n=24 controls). Mice were culled weekly (6 OA, 3 control) and scanned with microCT (vivaCT80, Scanco Medical, 10μm, 70 kVp; 57 μA) for 8 weeks (72 scans). Bone morphometry analysis was performed to quantify subchondral trabecular and cortical bone. Three-factor ANOVA was performed to determine the effect of time (weeks), site (lateral, medial) and group (OA, control). Bone volume (Tb.BV) of the femoral trabecular region was generally lower in OA samples than controls, and significantly lower in weeks 2, 4, and 7 (Figure 1a). In week 7 and 8 there is a noticeable downward shift in OA bone volume. This is linked to a higher trabecular spacing and lower trabecular number (data not shown). The same trend was observed in both medial and lateral compartments. The femoral cortical region showed significant differences from week 1, e.g. lower Ct.BV (Figure 1b) in OA samples compared to controls. These differences are visible in microCT images of typical control (Figure 1c) and OA samples (Figure 1d) from weeks 2 and week 7. These findings imply bone remodelling activity occurs simultaneously with the acute inflammatory response in this model, which will be more thoroughly investigated in follow-up studies.