Quantitative imaging of cartilage and bone morphology, reactive oxygen species, and vascularization in a rodent model of osteoarthritis.

Objective: To assess temporal changes in cartilage and bone morphology, reactive oxygen species (ROS), and vascularization in rats with monosodium iodoacetate (MIA)-induced osteoarthritis (OA), using advanced imaging methodologies.

Methods: Right knees of 8-week-old male Wistar rats were injected with 1 mg MIA in 50 μl saline and left knees were injected with 50 μl saline as controls. After 1, 2, and 3 weeks (n = 5 at each time point), changes in cartilage morphology and composition were quantified using equilibrium partitioning of an ionic contrast agent microfocal computed tomography (μCT), and changes in subchondral and trabecular bone were assessed by standard μCT. ROS were characterized by in vivo fluorescence imaging at 1, 11, and 21 days (n = 5 at each time point). Three weeks following fluorescence imaging, alterations in knee joint vascularity were quantified with μCT after perfusion of a vascular contrast agent.

Results: Femoral cartilage volume, thickness, and proteoglycan content were significantly decreased in MIA-injected knees compared with control knees, accompanied by loss of trabecular bone and erosion of subchondral bone surface. ROS quantities were significantly increased 1 day after MIA injection and subsequently decreased gradually, having returned to normal by 21 days. Vascularity in whole knees and distal femora was significantly increased at 21 days after MIA injection.

Conclusion: Contrast-enhanced μCT and fluorescence imaging were combined to characterize articular cartilage, subchondral bone, vascularization, and ROS, providing unprecedented 3-dimensional joint imaging and quantification in multiple tissues during OA progression. These advanced imaging techniques have the potential to become standardized methods for comprehensive evaluation of articular joint degeneration and evaluation of therapeutic efficacy.