Spontaneous production of nitric oxide (NO), prostaglandin (PGE(2)) and neutral metalloproteinases (NMPs) in media of explant cultures of equine synovial membrane and articular cartilage from normal and osteoarthritic joints

Nitric oxide (NO), prostaglandin E-2 (PGE(2)), and the activity of neutral metalloproteinases (NMPs) were measured in conditioned media of equine syno vial membrane and articular cartilage explant cultures from horses with nor mal joints (n = 7) and from horses affected with moderate (n = 7) or severe osteoarthritis (n = 14) as judged by macroscopic appearance. Normal articu lar cartilage appeared glossy and bluish-white, was of normal thickness and showed no evidence of discolouration, fibrillation or other cartilage disc ontinuity. Slight discolouration and fibrillation or minor clefts or the ca rtilage were considered as moderate OA, whereas erosions of articular carti lage down to the subchondral bone were considered as cases of severe OA. Explant cultures of equine synovial membrane and articular cartilage releas ed the local mediators, NO and PGE(2), as well as detectable levels of NMP activity into culture media. Concentrations of NO were higher in articular cartilage explants compared to synovial membrane explants, whereas concentr ations of PGE(2) were higher in synovial membrane explants. The NMPs with c ollagenolytic activities were similar in both explant cultures, whereas gel atinolytic activities were higher in synovial membrane explant cultures and caseinolytic activities were generally higher in articular cartilage expla nt cultures. Furthermore it was shown that concentrations or enzyme activit ies increased according to the severity of disease of the joints. Concentra tions for NO, collagenolytic and gelatinolytic NMPs were relatively stable, whereas PGE(2) and caseinolytic NMP concentrations increased over time in culture.