Free Axial Vibrations At 0 to 200 Hz Positively Affect Extracellular Matrix Messenger Ribonucleic Acid Expression in Bovine Nucleus Pulposi

Study Design. Bovine caudal intervertebral discs (IVDs) were exposed to free axial vibration for 10 to 60 minutes at 0 to 0.5g and 0 to 200 Hz. Expression of messenger ribonucleic acid for aggrecan, collagen type I, collagen type II, biglycan, decorin, and versican were assayed, as was apoptosis. Objective. To determine the vibration conditions which are most effective in altering intervertebral disc IVD gene expression. Summary of Background Data. Various studies have suggested widely varying effects of vibration in the IVD, ranging from harmful ( increased risk of degeneration) to beneficial ( increased analgesia) to neutral ( no effect). Methods. Vibration was applied using a custom designed voice coil system, which generated controlled motion in the axial direction. Gene expression in the nucleus pulposus was assessed using RT-PCR and the SYBR green chemistry; apoptosis was assessed using TUNEL staining. Results. Expression of messenger ribonucleic acids for biglycan, collagen type I, collagen type II, decorin, and versican were significantly affected by vibration duration, frequency, and amplitude. Aggrecan was unaffected. Of the 3 factors, amplitude had the largest and widest effect. Conclusion. Expression of extracellular matrix genes was significantly upregulated at high amplitudes (>0.4 g) in as little as 10 minutes. This may indicate a potential therapeutic stimulus; periodic application of controlled vibration could positively influence matrix maintenance. Further studies on the protein level and long-term effects are warranted.