Quantitative evaluation of very early cartilage damage in experimental osteoarthritis using scanning electron microscopy

To describe parametric changes observed using scanning electron microscopy (SEM) in very early stages in posttraumatic osteoarthritis (OA) models in mice. Mice (5/group) had their knees subjected to anterior cruciate ligament transection (ACLT), ACLT plus meniscectomy (MNCT) or sham surgery, sacrificed after 3, 7 or 14 days, had the articular cartilage evaluated under optical microscopy using Osteoarthritis Research Society International (OARSI) parameters as well as cartilage thickness, roughness, and a damage index using SEM. Alterations of the cartilage under optical microscopy were not significantly relevant among groups. SEM analysis revealed reduction of femoral and tibial cartilage thickness in ACLT and MNCT groups at 7 and 14 days, with increased cartilage roughness in MNCT group as early as 3 days postsurgery, being sustained up to 14 days. Articular damage index was significantly higher at 14 days post surgery in ACLT and MNCT vs control groups. This is the first demonstration of very early quantitative changes in the cartilage of mice subjected to posttraumatic experimental OA using SEM, revealing increased roughness and thickness as early as 3 days post surgery. These changes may be used as early surrogates for later joint damage in experimental OA.