Document Type : Full Research Paper
Author
Associate Professor, BioMedical Engineering School, Amir Kabir University of Technology
Abstract
The influence of compression on intervertebral disc cells has been examined in a number of previous studies. However, in most of these studies hydrostatic pressure was used at low levels, and few studies reported the effects of high pressures within a large range of frequencies on intervertebral disc cells response. The aim of the study was to test the hypothesis that frequency dependent hydrostatic pressure stimulates collagen synthesis in the intervertebral disc cells to a certain level. Hydrostatic pressure was applied to the intervertebral disc cells in a monolayer culture using a custom-made piston chamber pressure vessel. Briefly, cells were harvested from the intervertebral discs in the lumbar region of a pig, plated, and grown to confluence in culture flasks; they were then trypsinized and re-attached to 35mm culture dishes. With cyclic, hydrostatic loading, the cells were exposed to varied pressures and frequencies for 20 minutes a day for 3 and 7 days (the controls received no loading). The intracellular collagen was labeled with 3[H]-proline after loading on days 2 and 6. Following treatments on days 3 and 7, both the media and cells were frozen separately. Scintillation counting determined the amount of collagen incorporated in the cells and released into the media; these values were normalized by DNA. In this culture system, the results indicated significant differences (P<0.05) in cell response at different loading conditions. Compared to the control group there was a significant decrease in released collagen at high loading amplitude and low frequency (5MPa, 1Hz) which increased significantly at high loading frequencies (5MPa, 15Hz) indicating anabolic response at high pressures which became catabolic at high frequencies.
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