Frequency response of pig intervertebral disc cells subjected to dynamic hydrostatic pressure.
The pathogenesis of vibration-induced disorders of intervertebral disc at the cellular level is largely unknown. Dynamic loads with frequencies close to that of the in vivo human spine resonant frequency (4-6 Hz) have a destructive effect, which may induce extracellular disc matrix (ECM) degradation. To investigate this issue, three-dimensional (3D) alginate cultures of normal pig intervertebral disc nucleus and inner annulus cells were tested under dynamic hydrostatic loading. Alginate cultures of each region were divided into six groups; five groups were exposed to cyclic hydrostatic pressures of frequencies 1, 3, 5, 8, and 10 Hz with the same amplitude (1 MPa), and group 6 was the control group (no loading). Cultures of different groups were loaded for 3 days (30 min daily) in a hydraulic chamber. Effects of loading frequency on disc collagen and protein metabolism were investigated by measuring 3H-proline-labeled proteins associated with the cells in the extracellular matrix and release of 3H-proline-labeled molecules into culture medium. The results indicated a poor synthesis rate and more degradation near the 5 Hz frequency. The repeatability of experiments was verified by performing two experiments with the same protocol. Both experiments indicated that a threshold frequency of around 5 Hz disrupted protein metabolism.
Kasra
Mehran
M
Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada L8S 4L7, and Department of Orthopaedics and Rehabilitation, University of Iowa Hospitals and Clinics, Iowa City 52242, USA. kasram@mcmaster.ca
Merryman
W David
WD
Loveless
Kristen N
KN
Goel
Vijay K
VK
Martin
James D
JD
Buckwalter
Joseph A
JA
D000818:Animals; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D006874:Hydrostatic Pressure / Q000009:adverse effects*; D007403:Intervertebral Disc / Q000166:cytology / Q000378:metabolism; D013122:Spinal Diseases / Q000209:etiology*; D013552:Swine; D014732:Vibration / Q000009:adverse effects*
D016326:Extracellular Matrix Proteins