Everyone has a backstory. Chances are it’s also a back pain story, because estimates say about two-thirds of adults in the United States will suffer from back or neck pain during their lifetimes. Many instances of back pain are caused by damage or degeneration of the intervertebral disks—the squishy little hockey pucks that sit between vertebrae, helping our spinal columns move and absorb shocks.
Severe intervertebral disk degeneration is often treated with spinal fusion surgery, in which a damaged disk is removed and the adjacent vertebrae are welded together to form one solid bone. This leads to some loss of flexibility in the spine and increases the risk of other disks degenerating from compensating for the lost disk. Researchers have used tissue engineering to grow healthy disklike structures in the lab, but few studies have actually tested how these replacement disks perform over time when they’re implanted in living organisms.
So in a new study, scientists injected cow stem cells into cylinders of polymer gel and sandwiched the cylinders between two foam end-plates to simulate the mechanics and biochemistry of intervertebral disks. Then, they implanted the disks into the tail spines of 14 rats, and larger versions into the necks of seven goats. They observed the animals’ movement and health postsurgery for several weeks, then euthanized the animals and examined how the engineered disks held their shape while being subjected to compressing forces compared to the animals’ native disks.
Not only did the disks become stable and well-integrated into the native tissue of the animals’ spinal columns several weeks postsurgery, they were able to withstand stress forces just as effectively as the animals’ native disks, the team reports today in Science Translation Medicine. Although the researchers say there is still considerable work to be done before tests begin in humans, the fact that large animals like goats responded well to the treatment is a step forward for backs everywhere.