Gait analysis and pain response of two rodent models of osteoarthritis

The purpose of this study was to compare the gait parameters recorded on the CatWalk and the mechanical sensitivity with von Frey filaments of two putative models of osteoarthritis over a one month period, and to evaluate the effect of celecoxib on these parameters. Animals underwent either a surgical sectioning of the anterior cruciate ligament with partial medial menisectomy (ACLT+pMMx) to create a joint instability model or received an intra-articular injection of monoiodoacetate (MIA) as a putative inflammatory joint pain model. Animals were assessed for four consecutive weeks and knee joints were then evaluated histologically. Spinal cord lumbar enlargements were harvested for selected neuropeptide analysis (substance P (SP) and calcitonin gene related peptide (CGRP)). With the MIA model, significant changes persisted in selected dynamic gait parameters throughout the study in the injured limb as well as with the von Frey filaments. The ACLT+pMMx model in contrast showed no clear differential response between both hind limb for both gait parameters and pain-related behavior with von Frey filaments occurred only on the last day of the study. Neuropeptide analysis of spinal cord lumbar enlargements revealed a significant increase in CGRP concentration in both models and an increase in SP concentration only in the MIA model. Histological evaluation confirmed the presence of articular cartilage lesions in both models, but they were much more severe in the MIA model. Celecoxib had an effect on all selected gait parameters at the very beginning of the study and had an important alleviating effect on mechanical allodynia. These results suggest that the MIA model may be more appropriate for the evaluation of short term pain studies and that celecoxib may modulate mechanical allodynia through central sensitization mechanisms.