Down-regulated expression of vimentin induced by mechanical stress in fibroblasts derived from patients with ossification of the posterior longitudinal ligament.

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The aim of this study was to investigate the potential role of vimentin in the signal transduction pathways initiated by mechanical stimulation that contribute to ossification of the posterior longitudinal ligament of the spine (OPLL). We investigated the effects of in vitro cyclic stretch on cultured spinal ligament cells derived from OPLL (OPLL cells) and non-OPLL (non-OPLL cells) patients. The expression levels of the osteoblast-specific genes encoding osteocalcin (OCN), alkaline phosphatase (ALP), and type I collagen (COL I) were assessed by semi-quantitative reverse transcription-polymerase chain reaction. Vimentin protein expression in OPLL cells was detected by Western blotting. Small interfering RNA (siRNA) interference targeting vimentin was performed in OPLL cells induced by mechanical stress, and the expression levels of OCN, ALP and COL I were assessed. In response to mechanical stretch, the expression levels of OCN, ALP, and COL I were increased in OPLL cells, whereas no change was observed in non-OPLL cells. Furthermore, knockdown of vimentin protein expression by siRNA resulted in an increase in the mRNA expression levels of OCN, ALP, and COL I. The down-regulation of vimentin induced by mechanical stress plays an important role in the progression of OPLL through the induction of osteogenic differentiation in OPLL cells.