Research Reveals Inner Working of Spinal Discs

A neurosurgeon using pencil pointing at lumbar vertebra model in medical office. Lumbar spine x-ray on computer screen on background.

Remedies and solutions for back and neck pain are improving every day, and this is in large part to the hard work of researchers. All around the world, scientists are working to better understand the mechanics of the spine in hopes that what they learn can be harnessed and applied to improve patient treatments. A recent discovery by a team at the University of Pennsylvania has provided new insight into what happens when spinal discs are injured and may lead to the prevention of long-term damage.

According to the study, which was published in the journal Nature Biomedical Engineering, much of the long-term damage that happens when spinal discs are injured occurs on the outside of the disc. Though much of our attention has previously focused on the soft inner portions, the Penn Medicine team found that when a back injury occurs, changing the healing process that occurs in the discs’ outer shell may prevent the degenerative process that leads to chronic back pain.

According to Edward Bonnevie, PhD, a post-doctoral fellow in Penn Medicine’s McKay Orthopaedic Research Laboratory, the team’s discovery may lead to an entirely different approach to treating back injuries. “Most spine research focuses on the inner part of the disc, but our work highlights the fact that we need to treat the whole disc, and we believe doing so may lead to the identification of new targets for therapy.”

The group explains its findings by describing the spinal discs as being similar to water balloons, comparing the cells in the inner portion to the water and the cells in the outer portion as being similar to the rubbery outer surface that is always stretched.

In focusing on this outer surface, they found that when a disc is herniated and loses some of its inner pressure, the area of cells that are normally stretched become disorganized.

In response, they repair themselves, but do so in a way that leaves a new kind of tissue that is more rigid. They also found that when these cells are badly injured they die far more quickly than do other cells in the body, and because there is so little blood supply to the cells in the disc, regeneration is challenging.

Upon their discovery, the researchers tested whether it was possible to slow the process through the use of a biological inhibitor of cell contraction. In doing so they were able to “relax” the spinal disc cells following injury so that the healing response was put on pause. In doing so, the team believes physicians will have more time to treat the patient and minimize long-term damage.

Senior author Robert L. Mauck, PhD, a professor of Orthopaedic Surgery and director of the McKay Lab, concluded the study by writing, “These data show us that treating disc injuries very soon after injury is essential, before this transition in phenotype occurs and the scar tissue forms. This could be done using inhibitors like fasudil applied systemically, or potentially in combination with surgical implantation of biomaterials that are designed to restore the native tissue structure and function.”

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