YKL-40 in human lumbar herniated disc and its relationships with nitric oxide and cyclooxygenase-2.

The basic pathophysiology of intervertebral disc degeneration and low back pain remains unclear. It has been hypo-thesized a role of biochemical mediators of inflammation and tissue degradation in intervertebral disc degeneration and herniation.Chitinase 3-like protein 1 (YKL-40) is a glycoprotein mainly secreted by chondrocytes which has been proposed as a possible marker of inflammation and/or cartilage alterations. OBJECTIVES:To investigate the YKL-40 presence in human lumbar disc tissue culture and its possible relationships with some substances relevant in inflammation such as cyclooxygenase-2 (COX-2) and nitric oxide (NO). PATIENTS AND METHODS: We analyzed lumbar discs from 19 patients who underwent surgery for lumbar disc herniation at L4-L5 or L5-S1 levels. The specimens were cultured and incubated for 72 hours. At the end of incubation, the supernatants were assayed for presence and concentration of YKL-40, COX-2 and NO. RESULTS: YKL-40 was detectable in all the samples analyzed. Mean (± SD) concentration was 1.54 ± 1.29 ng/ml/mg compared to dry weight. COX-2 and NO levels were 25.25 ± 11.42 pg/ml/mg and 1.3 ± 1.8 µM/mg x 10-2, respectively. A correlation was found between YKL-40 and COX-2 (r = 0.579, p < 0.05) and YKL-40 and NO (r = 0.509, p < 0.05). CONCLUSIONS: To our knowledge, this is the first report demonstrating YKL-40 release by intervertebral disc culture. It may contribute to better clarify the role of this protein in the pathophysiology of discal degeneration and inflammation as confirmed by its relationships with COX-2 and NO in disc tissue culture.