Die Bedeutung der Expression von CD44 und dessen Splice-Varianten CD44v5 und CD44v6 in hypertrophiertem Ligamentum flavum für die Ausprägung einer lumbalen Spinalkanalstenose

Background: The most common spinal disorder in the elderly is lumbar spinal stenosis (LSS), which results in part from ligamentum flavum (LF) hypertrophy. Although prior histologic and immunochemical studies have been performed in this area, the pathophysiology of loss of elasticity and hypertrophy is not completely understood. The purpose of this immunohistological study is to elucidate the role of CD44 and its splice variants CD44v5 and CD44v6 in the hypertrophied LF obtained from patients with lumbar spinal stenosis (LSS). Materials and methods: LF samples of 38 patients with LSS were harvested during spinal decompression. Twelve LF samples obtained from patients with disc herniation and no visible degeneration on preoperative MRI were obtained as controls. Samples were dehydrated and embedded in paraffin. For immuno-histochemical determination, slices were stained with antibodies against CD44, CD44v5, and CD44v6 stained with DAB. LF hypertrophy and minimal Cross-Sectional Area (CSA) were measured with T1-weighted MRI. Results: CD44 and CD44v5 expression were significantly increased in the hy-pertrophy group. CD44v6 expression was not significantly increased. In the hypertrophy group, LF thickness was significantly increased while CSA was significantly decreased. There was a statistical correlation between LF thickness, mCSA, CD44, and CD44v5 expression in the hypertrophy group. Conclusions: LF hypertrophy is accompanied by increased CD44 and CD44v5 expression. CD44v6 expression is not enhanced in LF hypertrophy. Our study provides a molecular mechanism for biomechanical changes observed in LSS that are not explained by morphologic characteristics alone.