Multi-unit sustained vibration loading platform for biological tissues: design, validation and experimentation.

The relationships between mechanical inputs and resulting biological tissue structure, composition, and metabolism are critical to detailing the nuances of tissue mechanobiology in both healthy and injured tissues. Developing a model system to test the mechanobiology of tissues ex-vivo is a complex task, as controlling chemical and mechanical boundary layers in-vitro are difficult to replicate. A novel multi-unit vibration loading platform for intervertebral discs was designed and validated with both independent electronic data and experimental loading of 6 bovine intervertebral discs (IVDs) and an equal number of unloaded controls. Sustained vibration was applied using closed-loop positional control of pushrods within four independent bioreactors with circulating phosphate buffered saline. The bioreactors were designed to be modular with removable components allowing for easy cleaning and replacement. The loading regime was chosen to maximize target mRNA expression as reported in previous research. Aggrecan, decorin, and versican mRNA all reported statistically significant increases above control levels. Biglycan, collagen type I and II showed no significant difference from the control group. Further study is required to determine the resulting effect of increased mRNA expressions on long-term disc health. However these results indicate that this research is past the proof of concept stage, supporting future studies of mechanobiology utilizing this new device. The next stage in developing this novel loading platform should consider modifying the tissue grips to explore the effects of different directional loading on different gene expression, and also loading different types of tissues.

Disc strain and resulting positive mRNA expression from application of a noninvasive treatment.

STUDY DESIGN: Bovine caudal intervertebral discs were exposed to a noninvasive vibrating intervention for 10 minutes at amplitudes of 0 or 0.5 to 5 g and frequencies of 0, 16, 50 to 80, and a combined 16+50 to 80 Hz treatment. Expression of mRNA for aggrecan, collagen type I, collagen type II, biglycan, decorin, and versican were assayed. OBJECTIVE: To determine if the intervention is effective in altering intervertebral disc gene expression. SUMMARY OF BACKGROUND DATA: Studies have variously suggested either an increased risk of disc degeneration with vibrations, no effect, analgesic effect, or even positive effects within certain loading parameters. The KKT intervention is in clinical use for spinal ailment pain reduction. METHODS: The intervention was applied in a clinic emulation set-up. Gene expression in the nucleus pulposus was assessed using real-time RT-PCR and SYBR Green chemistry. RESULTS: Expression of mRNAs for aggrecan, collagen type II, and versican were significantly effected by the intervention. Collagen type I, biglycan, and decorin were uneffected. CONCLUSION: Expression of the extracellular matrix genes were significantly up-regulated when vibrated with the intervention under specific loading patterns, indicating a potential therapeutic stimulus. Further studies on the protein-level and long-term effects are warranted. Previous studies have indicated a mixed effect of vibrations in the human spine. In this study, a clinical intervention using vibrations was applied to bovine intervertebral discs, and gene expression in the nucleus pulposus was measured. Several extracellular matrix genes were up-regulated, suggesting a potential therapeutic effect.