BACKGROUND: The aim of this study was to identify a primate model of degenerative knee osteoarthritis (KOA) that may be more relevant for research studies on degenerative KOA in humans.

MATERIAL AND METHODS: Sixteen specific-pathogen-free (SPF) male cynomolgus monkeys (Macaca fascicularis) were divided into group A (n=8), an old group (22.0–25.3 years of age), and group B (n=8), a young group (3.0–5.2 years of age). For each primate, the behavior was observed, knee circumference was measured, knee joint X-rays were performed, and peripheral blood white blood cell (WBC) counts were measured, and the Kellgren and Lawrence (K-L) system was used for the classification of osteoarthritis. An enzyme-linked immunoassay (ELISA) was performed on knee joint fluid to measure levels of interleukin (IL)-1β, transforming growth factor (TGF)-β1, and matrix metalloproteinase (MMP)13. Changes in articular cartilage were evaluated using the Brittberg score and the Mankin histopathology grading score, respectively. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot were used to measure the expression of the NOTCH3, JAG1, and ACAN genes in knee cartilage specimens, and the findings in the two groups of primates were compared.

RESULTS: Seven old aged primates in group A were compared with group B, and showed significant differences in WBC count, synovial fluid IL-1β, TGF-β1, and MMP13 levels, expression levels of the NOTCH3, JAG1, and ACAN genes in knee cartilage specimens, and in the Brittberg and Mankin scores (all, P<0.05).

CONCLUSIONS: Cynomolgus monkeys (Macaca fascicularis) might be a model for age-related degenerative KOA.

Keywords: Cartilage, Articular, Macaca fascicularis, Osteoarthritis, Receptors, Notch