School of Engineering and Materials Science
Research Student Awards
PhD Thesis: Role of nitric oxide and PGE2 in chondrocyte mechano transduction.
Author: CHOWDHURY, TT
Both mechanical loading and the pro-inflammatory mediator, IL-1, are known to regulate metabolic processes in articular cartilage through pathways mediated by NO and PGE2. The work presented in this thesis, uses a well characterised model system involving isolated chondrocytes cultured in agarose constructs to test the hypothesis that dynamic compression alters the synthesis of NO and PGE2 production by IL-1 stimulated articular chondrocytes.
The present findings demonstrate that in IL-1 stimulated cultured full depth chondrocytes, NO and PGE2 synthesis was enhanced, cell proliferation and proteoglycan synthesis were inhibited. With the exception of the latter, these effects were reversed by the NOS inhibitor, L-NIO. Data, in the form of absolute and percentage changes, demonstrate that dynamic compression abrogates the effects of IL-1 on chondrocytes by suppressing both NO and PGE2 synthesis by approximately 50 -60 %. Inhibitor experiments indicated that dynamic compression-induced inhibition of PGE2 synthesis and stimulation of proteoglycan synthesis were NO mediated, while compression-induced stimulation of cell proliferation was NO independent.
In a further study, the application of dynamic compression to chondrocytes from the superficial and deep zones of articular cartilage was investigated. Absolute levels of NO and PGE2 were 40 - 60 % higher for IL-1 stimulated superficial cells than the deep cells. Dynamic compression of superficial cells abolished these effects and L-NIO reduced NO production even further. By contrast, for superficial cells, PGE2 synthesis was enhanced with L-NIO. Absolute levels of cell proliferation and proteoglycan synthesis were found to be 2 - 3 fold greater for the deep cells, although no significant differences were found between the percentage changes.
A preliminary examination at the molecular level, demonstrated that IL-1 stimulated cultured chondrocytes, expressed iNOS and mRNA by RT-PCR analysis. In addition, culturing the chondrocytes within the cell-straining apparatus, enhanced iNOS mRNA expression, and this response was largely removed with L-NIO.
The inhibition of NO and PGE2 by dynamic compression is a finding of major significance that could contribute to the development of novel strategies for the treatment of degenerative disorders of articular cartilage.