Morphologic and apoptotic changes of cervical posterior longitudinal ligament fibroblasts in response to in vitro mechanical stretch

Abstract

To investigate the effect of mechanical stretch force on the morphologic and apoptotic changes of fibroblasts derived from the OPLL (ossification of posterior longitudinal ligaments) patients. The third passage cells were collected and subjected to 10% elongations cyclic mechanical stretching for 6 h and 24 h with Flexercell 4000(TM) strain unit. Their morphologic changes were observed and the post-stretching apoptotic rates quantified by flow cytometer. The gene expressions of alkaline phosphatase (ALP), collagen types I (COL I) and osteocalcin (OC) were examined. The treated cells were arranged along the vertical direction of force. Stretch force led to a slight increase of apoptosis rate at 6 h and a significant increase of apoptosis rate at 24 h. No significant difference in cellular senescence was observed between control group and treated group. The mRNA expressions of ALP, COL I and OC were positively up-regulated by cyclic stretch at 24 h. Stretching force can affect the cellular morphology, promote the osteogenic differentiation and enhance the cellular apoptosis.