Dynamic compression counteracts IL-1β-induced release of nitric oxide and PGE2 by superficial zone chondrocytes cultured in agarose constructs

Objective: To examine the effect of IL-1beta-induced .NO and PGE(2) release by stimulated superficial and deep chondrocyte/agarose constructs subjected to mechanical compression. Design: Chondrocyte sub-populations were seeded separately in agarose constructs and cultured unstrained, within a 24-well tissue culture plate, for 48 h in medium supplemented with IL-1beta and/or L-N-(1-iminoethyl)-ornithine (L-NIO). In a separate experiment, superficial and deep cell containing constructs were subjected to 15% dynamic compressive strain at 1 Hz, for 48 h, in the presence or absence of IL-1beta and/or L-NIO. Nitrite was measured using the Griess assay, PGE2 release was determined using an EIA kit and [H-3]-thymidine and (SO4)-S-35 incorporation were assessed by TCA and alcian blue precipitation, respectively. Results: The current data reveal that IL-1beta significantly enhanced NO and PGE(2) release for superficial chondrocytes, an effect reversed with L-NIO. NO and PGE(2) levels did not significantly change by deep cells in the presence of IL-1beta and/or L-NIO. For both cell sub-populations, IL-1beta inhibited cell proliferation whereas proteoglycan synthesis was not affected. Dynamic compression inhibited the release of NO and PGE(2) in the presence and absence of IL-1beta, for cells from both sub-populations. L-NIO reduced NO and enhanced PGE(2) release for superficial zone chondrocytes, an effect not observed for deep cells in response to dynamic compression. The magnitude of stimulation of [3H]-thymidine incorporation was similar for both cell sub-populations and was not influenced by L-NIO, indicating an NO-independent pathway. The dynamic compression-induced stimulation of (SO4)-S-35 incorporation was enhanced with L-NIO for IL-1beta-stimulated deep cells, indicating an NO-dependent pathway. Conclusion: The present findings suggest that dynamic compression inhibits NO and PGE(2) release in IL-1beta-stimulated superficial cells via distinct pathways, a significant finding that may contribute to the development of intervention strategies for the treatment of inflammatory joint disorders. (C) 2003 Published by Elsevier Ltd on behalf of OsteoArthritis Research Society International.