Spinal discs made of engineered living tissue implanted in large animal model.

Approximately half the adult population in the United States is suffering from back or neck pain for which treatment and care costs result in an estimated 195 billion USD a year.  Current treatments include spinal fusion surgery and mechanical replacement devices, and while these treatments provide symptomatic relief, they do not restore native disc structure, range of motion, or offer limited long-term efficacy.  Therefore, new therapies are highly desired.  Now a study from researchers at Penn Medicine bioengineers personalised spinal discs which were then implanted to provide long-term function in the largest animal model ever evaluated for tissue-engineered disc replacement.  The team state that their results provide translational evidence that the cells of patients suffering from neck and back pain could be used to build a new spinal disc in the lab to replace a deteriorated one.  The study is published in the journal Science Translational Medicine.

Previous studies show that tissue engineering involves combining the patients’ or animals’ own stems cells with biomaterial scaffolds in the lab to generate a composite structure which is then implanted into the spine to act as a replacement disc. Past studies from the lab developed a tissue engineered replacement disc, moving from in vitro basic science endeavors to small animal models where the team have successfully demonstrated the integration of their engineered discs, known as disc-like angle ply structures (DAPS), in rat tails for five weeks.  The current study extends the time period in the rat model up to 20 weeks and up to 8 weeks in vivo in the goat cervical disc space, with revamped engineered discs, known as endplate-modified DAPS, or eDAPS.

The current study sandwiches hydrogel and polymer materials seeded with cartilage or mesenchymal stem cells between acellular polymer endplates to simulate the mechanics and biochemistry of intervertebral discs. The disks were implanted into the tail spines of 14 rats, and larger versions into the necks of seven goats.  Results show the disks are stable and well-integrated into the native tissue of the animals’ spinal columns several weeks post-surgery, and were able to withstand stress forces just as effectively as the animals’ native disks.

The lab state that they demonstrated successful total disc replacement in the goat cervical spine, with the matrix distribution either retained or improved within the large-scale eDAPS after four weeks.  They go on to add that MRI results also suggest that disc composition at eight weeks was maintained or improved, and that the mechanical properties either matched or exceeded those of the native goat cervical disc.

The team surmise that they have used tissue engineering to grow healthy disk-like structures in the lab, and successfully implanted those discs into a large animal model.  For the future, the researchers state the next step will be to conduct longer-term studies to further characterize the function of the eDAPS in the goat model, as well as model the degeneration of spinal discs in humans and to test how their engineered discs perform in that context.

Source: Penn Medicine


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