As the shock-absorbing cartilage discs between our vertebrae degenerate due to aging, accidents or overuse, severe back pain can result. While some scientists have developed purely synthetic replacement discs, a recent test on goats indicates that bioengineered discs may be a better way to go.

Although the replacement of degraded intervertebral discs with synthetic ones does help alleviate pain, scientists at the University of Pennsylvania claim that the implants don't match the function or range-of-motion of real cartilage, plus some of them don't last very long. That's where the researchers' bioengineered discs may make a big difference.

Still in the animal-trial phase, the discs are made by first obtaining a lab animal's mesenchymal stem cells (cells that can form into cartilage) and then adding them to a scaffolding-like matrix made up of hydrogel and polymer, which is sandwiched between two polymer endplates. The stem cells proceed to propagate into that matrix, gradually replacing it with actual cartilage. What ultimately results is a disc composed of the animal's own cartilage, which can then be surgically substituted for one of their existing discs.

Previously, an earlier miniaturized version of the disc was implanted into the spinal column of live rats' tails, and was still successfully functioning after five weeks. Those discs were officially known as disc-like angle ply structures, or DAPS.

In a more recent trial, though, the new-and-improved endplate-modified DAPS (eDAPS) were still going strong after 20 weeks in rats' tails, with the discs reportedly "maintaining their structure and showing near-native mechanical properties." More importantly, when larger eDAPS were implanted into the cervical spine of goats (procedure pictured above), they were likewise good eight weeks later, as their mechanical properties "either matched or exceeded those of the native goat cervical disc."

Goats were chosen due to the fact that the dimensions of their cervical spinal discs are similar to those of humans, plus (as compared to rats) the animals have a semi-upright posture. Plans now call for longer-term goat studies, with an eye towards eventual human trials.

"This is a major step: to grow such a large disc in the lab, to get it into the disc space, and then to have it to start integrating with the surrounding native tissue. That's very promising," says Prof. Robert L. Mauck, co-senior author of a paper on the research. "The current standard of care does not actually restore the disc, so our hope with this engineered device is to replace it in a biological, functional way and regain full range of motion."

The paper was recently published in the journal Science Translational Medicine.

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