Dynamic compression counteracts IL-1β-induced release of nitric oxide and PGE 2by superficial zone chondrocytes cultured in agarose constructs

Abstract

Objective: To examine the effect of IL-1β-induced NO and PGE 2release 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-1β 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-1β and/or l-NIO. Nitrite was measured using the Griess assay, PGE 2release was determined using an EIA kit and [ 3H]-thymidine and 35SO 4incorporation were assessed by TCA and alcian blue precipitation, respectively. Results: The current data reveal that IL-1β significantly enhanced NO and PGE 2release for superficial chondrocytes, an effect reversed with l-NIO. NO and PGE 2levels did not significantly change by deep cells in the presence of IL-1β and/or l-NIO. For both cell sub-populations, IL-1β inhibited cell proliferation whereas proteoglycan synthesis was not affected. Dynamic compression inhibited the release of NO and PGE 2in the presence and absence of IL-1β, for cells from both sub-populations. l-NIO reduced NO and enhanced PGE 2release 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 35SO 4incorporation was enhanced with l-NIO for IL-1β-stimulated deep cells, indicating an NO-dependent pathway. Conclusion: The present findings suggest that dynamic compression inhibits NO and PGE 2release in IL-1β-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.