Surgically-induced knee joint instability in rats by transection of the Anterior Cruciate Ligament (ACLT), partial medial Meniscectomy (pMx) or a combination of both (ACLTpMx), is one of the most commonly used experimental animal models of osteoarthritis (OA), see [1],[2]. It shows very similar anatomical location and histopathological features as the human disease. The model is suitable for studying basic pathophysiological aspects of OA and for the pharmaceutical development of disease-modifying drugs.
The severity of joint destruction can best be demonstrated in coronal histological sections of the whole knee joint; stained with Safranin-O-Fast Green (or Hematoxilin-Eosin, see related APP no. 10026). The most important histopathological hallmarks are surface fibrillation and erosion of the articular cartilage, decrease in chondrocyte number, loss of proteoglycan staining and a sclerosis (thickening) of the subchondral bone plate.
Traditionally, the evaluation of the severity of joint damage is done by subjective semi-quantitative grading of the different histopathological features using defined scoring systems, see [3]. However, even with ‘blinding’ of the observers and sample randomization, this methodology is prone to bias, suffers from low sensitivity to change and requires considerable experience in histopathology. On the other hand, quantitative digital histomorphometry of cartilage destruction and subchondral bone sclerosis can offer an objective, less time consuming and more sensitive assessment of OA histopathology, see [4].
This APP can be used for quantifying a number of parameters relating to joint damage: Cartilage volume/area, surface fibrillation and proteoglycan loss (intensity measure). The APP has been verified in both age-dependency studies and treatment studies.