Abstract
Introduction: Increased levels of IL-6 and IL-8 have been found in intervertebral disc (IVD) tissue from patients undergoing fusion for discogenic low back pain. The stimuli that induce these mediators in degenerate discs remain unknown. Impaired diffusion of nutrients and wastes to and from the nucleus pulposus (NP) is believed to be an important factor in the degenerative process. The oxygen tension and pH in the NP of degenerating discs are significantly decreased.
Aims: The aims of this study were to (1) demonstrate the ability of porcine NP to respond to a proinflamma-tory stimulus (lipopolysaccharride) in vitro, (2) investigate the effects of pH, pO2 and glucose concentration on NP proinflammatory mediator secretion and (3) determine if methylprednisolone or indomethacin can block NP proinflammatory mediator secretion.
Methods: IVDs were harvested from 6-month old pigs and dissected under sterile conditions in the laboratory. 200mg samples of NP were cultured under optimal conditions (control), in a 1% O2 environment, at pH6 and in culture medium without glucose for 72 hours. Blocking experiments were performed by culturing LPS-stimulated samples with either methylprednisolone or indomethacin for 24 hours. IL-6 and IL-8 levels were estimated by ELISA.
Results: Time and dose-response curves were generated for each experiment (results not shown). Results for the optimum dose and at 72 hours incubation were note.
Data = mean ± standard deviation. Statistical analysis was by students t test. A significant result between control and stimulated groups is indicated by: * p=0.024m, † p=0.0007 or ‡ p=0.012.
Methylprednisolone (2mg/ml) caused a significant (p=0.044) 30-fold reduction in IL-6 production and a significant (p=0.00004) 500-fold reduction in IL-8 levels as compared with nucleus pulposus cultured with 5 μg/ml LPS alone for 24 hours.
Addition of 500 μM indomethacin significantly (p=0.04) decreased IL-6 production by a factor of 120 and IL-8 levels by a factor of 50 (p=0.00004).
Necrotic cell death, as measured by lactate dehydrogenase (LDH) concentration, was not significant in any of the experiments.
The abstracts were prepared by Mr Ray Moran. Correspondence should be addressed to him at Irish Orthopaedic Associaton, Secretariat, c/o Cappagh National Orthopaedic Hospital, Finglas, Dublin 11.
