Temporal production of nitric oxide and prostaglandin E-2 in media of explant cultures of equine synovial membrane and articular cartilage

The local mediators nitric oxide (NO) and prostaglandin E-2 (PGE(2)) play a role in the cascade of extracellular matrix breakdown in articular cartila ge. In the present study the spontaneous production of NO and PGE(2) in exp lant cultures of equine synovial membrane and articular cartilage and their concentration over time in culture was investigated and correlated. Synovi al membrane and articular cartilage was harvested from metacarpophalangeal joints of 33 horses during arthroscopic surgery (n = 4) or after being slau ghtered/euthanised for reasons other than infectious or metabolic disease ( n = 29). Tissues were cultured as explant cultures in the presence of 4 mi Ham's F-12 medium, supplemented with streptomycin (100 mug/ml) and penicill in (100 U/ml) and incubated in a 5% CO2 and water saturated atmosphere for 8 days. Results showed that generally equine synovial membrane produced les s NO than articular cartilage explant cultures with comparable wet weights/ ml of media, but significantly more PGE(2) (P < 0.05). The concentrations o f both mediators were relatively stable over the first 4 days of culture, a t least in the group of 25 mg wet weight/ml of media. In this group, there was a weak tendency noticed for NO to decrease, and PGE(2) to increase over time with day 4 being the intersection for both. Tissue cultures of articu lar cartilage with 12.5 mg wet weight/ml of culture media produced less rel iable results, especially with NO measurements, which was thought to be ass ociated with the sensitivity of the assay. It is recommended to collect con ditioned media for the measurements of NO and PGE(2) within the first 4 day s of explant culture, since after this time period culture effects may mask the results at least for NO measurements. Both mediators may be factors th at play an important role in the local mediation of joint inflammations.