The influence of enrichment devices on development of osteoarthritis in a surgically induced murine model.

This study measured the influence of three different environmental enrichment devices (EEDs) on the severity of osteoarthritis (OA) in a surgically induced murine model. The development of OA requires joint movement after surgical instability induced by destabilization of the medial meniscus at 10 weeks of age. We evaluated the hypothesis that animals behavioral activity levels may influence the severity of the disease by investigating the effect of different EEDs on mouse activity and correlating this to OA severity. Thirty male 129S6/SvEvTac mice were housed in groups of five and provided with nesting material and one of three different EEDs: a heavy plastic tube (CPVC), Shepherd Shack (SS), or Tecniplast Mouse House (TMH). We videorecorded the cages throughout the study and constructed an ethogram. Eight weeks after surgery we euthanized the mice and performed a histologic examination of the knees to score the severity of OA based on the different housing systems, correlating the scores with behavioral activity levels for each cage. OA was higher in the mice with CPVC and TMH devices in their cages, whereas the mice with SS devices exhibited less cartilage damage; however, although we observed increased behavioral activity in mice with the CPVC tube and TMH and less in mice with the SS, the statistical results were not significant. The histological results of OA and the ethogram correlated to support our hypothesis that the type of EED plays an indirect role in the severity of the disease by modifying the activity levels of mice. In activity-dependent studies, the impact of an EED needs to be evaluated before change the environment.