Background: Lumbar spinal canal stenosis (LSCS) is one of the most common spinal disorders in the elderly, and ligamentum flavum (LF) hypertrophy is an important cause of LSCS. Matrix metalloproteinase 13 (MMP13) can degrade fibrillar collagens and elastic microfibrils, and is involved in inflammation and fibrosis. The purpose of this study was to compare the expression of MMP13 in the LF from LSCS patients with diabetes mellitus [DM (+)] with that in the LF from patients without DM [DM (-)] and to analyze the relationship among DM, MMP13 expression, and LF hypertrophy. Methods: LFs from 11 DM (+) and 24 DM (-) LSCS patients were analyzed in this study. Histology analysis using hematoxylin and eosin and Masson's trichrome stain was performed for each LF. The expression of MMP13 was analyzed by quantitative real-time PCR. The thickness of LF was measured by CT. Results: In the LF from DM (+) LSCS patients, the elastic fibers were more disorganized and had lower volumes than in the LF from DM (-) LSCS patients, while more fibrotic tissue was observed in the LF from DM (+) than from DM (-) LSCS patients. MMP13 expression was significantly higher in the LF from DM (+) LSCS patients (0.46 ± 0.61 vs. 0.05 ± 0.09, P = 0.002). The LF from the DM (+) LSCS patients was significantly thicker than that from the DM (-) LSCS patients (5.0 ± 0.9 vs. 3.1 ± 0.8 mm, P < 0.01), and the thickness was correlated with the expression of MMP13 (correlation coefficient = 0.43, P = 0.01, Pearson's correlation test). Conclusion: DM-related MMP13 expression can be one of the factors contributing to fibrosis and hypertrophy of the LF. Further research on the mechanism of this process may lead to new therapies for LF hypertrophy.
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