Low back pain is one of the major causes of high socioeconomic costs world-wide in the developed nations. About 80% of the Swiss population suffer at least once in their lifetime from severe low back pain. Correlative evidence points towards a link between low back pain and degenerative disc disease (DDD). Genetics, but also epigenetic factors, like endplate calcification, mechanical overloading or endplate fractures, play a critical role in the risk of development of DDD. The degeneration of the IVD is accompanied by increased cell death, activation of catabolic enzymes, and finally also biochemical changes of the extracellular matrix. Previous in vivo and in vitro studies indicate relatively moderate cellular responses to uniaxial compressive loading, possibly due to the lack of shear and other complex forces. Here, we propose to increase the complexity of the mechanical loading regime by the addition of axial torsion during organ culture. It is known that pure torsion of ~2° will increase disc height, and decrease intra- discal pressure. The project aims to demonstrate the importance of combined mechanical force and motion to the cell activity and metabolism of IVD cells. The “twisting” motion increases risk for disc herniation by several orders of magnitudes.

Significance of Research. This in vitro organ culture system of intact IVDs allows control of parameters associated with disc degeneration. Combined axial torsion and cyclic compression have never been investigated at the disc cell level in situ in the intervertebral disc. The results gained from these experiments may provide insights into the mechanisms leading to disc degeneration and may help in finding therapy strategies to prevent or to delay DDD.

The biomechanical study on torsion of intervertebral discs is supported by the SNF grant # 310030-127586/1.