2.8. Histologic Inflammation Scoring System

A histologic inflammation scoring system was developed in order to have a semi-quantitative measure that can be used to compare outcomes of pathology in therapeutic studies. Based on a previous study [9], our scoring system focused on the following tissue categories: joint space, including articular cartilage and synovium; skeletal muscle and soft tissue, including tendons and fascia; periosteum; and cortical bone. A microscopic evaluation of bone and joint tissue assessed inflammatory reaction and injury in (1) the synovium, (2) articular cartilage, (3) skeletal muscle and soft tissue, (4) periosteum, and (5) cortical bone. The scoring for each component ranged from zero to two, with zero indicating no injury or inflammation, two representing significant injury and inflammation and one representing intermediate involvement with respect to inflammation or injury. Histologic evaluation assigned a maximum value of two points for muscle and soft tissue injury and inflammation, two points for synovitis, two points for articular cartilage erosion, two points for bone and periosteal reaction, and two points for cortical bone erosions for a total range in score of 0–10 per mouse. The scoring system was based on the maximal degree of inflammation and injury seen at day 7.