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Cell Therapy Technique Tested to Regenerate Back Discs

Lori Setton, foreground, with co-author Robby Brooks

Lori Setton, foreground, with co-author Robby Brooks (Duke University)

Biomedical engineers at Duke University in Durham, North Carolina developed a new biomaterial to deliver cells that repair the cushions between spinal discs and relieve the pain when that material degenerates. The team led by biomedical engineering professor Lori Setton — with colleagues from Duke, Singapore, and Taiwan — published their proof-of-concept findings last week online in the journal Biomaterials (paid subscription required).

Setton and colleagues aimed to find a technique that could deliver live cells in a synthesized replacement material to the nucleus pulposus, the gel-like material that fits between spinal discs and absorbs and distributes the pressure from movements of the torso or limbs. Weakening the nucleus pulposus results in a herniated disc, a painful condition in the neck or lower back that becomes more common as people age.

The Duke team says some companies offer cell therapies to delay disc degeneration that involve re-implantation of nucleus pulposus or stem cells, but those methods have problems keeping the cells concentrated at the injection site and thus are limited in their effectiveness. To overcome this problem, the researchers synthesized a substance that acts like a protein found in nucleus pulposus known as laminin that binds to and enables the implanted cells to last longer at the injection site.

Delivering the cells and laminin to the spine required development of another material, this one containing the common water-soluble polymer compound polyethylene glycol and hydrogels attached to chemically modified laminin. The individual materials can be injected as liquids, but when they combine after injection, form into a gel that holds the cells in place.

Setton’s team tested the process on rats, using the rats’ tails as models for the spine. The researchers tagged the nucleus pulposus cells with a luminous biomarker to monitor the location of the cells. They then injected the gel components and cells into the tails, holding the needle in place for one minute before removal.

By tracking the luminous biomarker in the injections, the Duke team found the solution begins to solidify in about five minutes and becomes set as a gel in about 20 minutes. After 14 days, more cells remained at the injection site than current methods that use a liquid suspension. First author Aubrey Francisco says with current methods, all injected nucleus pulposus cells leak from the site after three or four days.

More work remains before the technique can be tested in human trials. The process needs to be optimized, for example, to deliver cells to larger spines like those in humans.

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