Combined tissue engineering provides new hope for spinal disc herniations

A promising new tissue engineering approach may one day improve outcomes for patients who have undergone discectomy – the primary surgical remedy for spinal disc herniations. Tested in live sheep for more than six weeks, the technique is among the first to address damage to both components of intervertebral discs: the tough outer ring, or annulus fibrosus (AF), and the gelatinous inner core, the nucleus pulposus (NP). A spinal disc herniates when the AF ruptures, resulting in a bulbous protrusion of NP tissue that can impinge nearby spinal nerves. This nerve pressure can cause substantial pain and, in extreme cases, loss of sensation and motor control. To relieve this pressure, a surgeon may perform a discectomy to remove the protruding NP tissue. However, there are currently no approved methods to restore lost NP tissue or to repair damage to the ruptured AF, leaving patients at risk of additional herniations and further disc degeneration. Prior tissue engineering work has suggested that repairing the AF or the NP alone is not enough – both components must be restored to ensure a positive outcome. Stephen Sloan and colleagues addressed this using a tissue engineering approach based on biomolecules present in healthy connective tissue, cartilage, muscle and skin. By injecting hyaluronic acid into the NP of live sheep that had undergone lumbar discectomy, the researchers improved the hydration and structural integrity of NP tissue. Then, during the same surgery, the researchers applied a crosslinked collagen patch to locally repair the wounded AF tissue. After six weeks of testing, their combined method substantially improved the structure and function of the sheep’s spinal discs. Sloan et al. suggest that, with further development and testing, their method could one day inform strategies to improve outcomes for human discectomy patients.

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