Nearly 300,000 Americans have sustained some form of spinal cord injury (SCI), and effective therapies to promote recovery of neural function are lacking. Our vision is to create an off-the-shelf spinal cord implant to replace the injured tissue.
We used the natural spinal cord architecture as a template to design a scaffold that mimics the intact cord. We chose materials with mechanical properties that are similar to the spinal cord properties in order to allow superior integration. We then used rapid 3D printing technology that can fabricate the implant in one continuous print, rather then layers as being done by common inkjet 3D-printers. The interface between each layer is a mechanically weak area; our method produce a more stable structure. A 2-mm implant was printed within 1.6 seconds, ~1,000 times faster, and with better resolution, than inkjet 3D-printing technology. We further loaded the implants with with neural stem cells that are able to differentiate and create new neurons that can connect to the intact, nerves in the spinal cord. Thus, a relay is formed through the implant, where host nerves penetrate the implant and connect to the neural stem cells, which in turn transfer the incoming commands (from the brain) to the target muscles. We grafted 2-mm implants, loaded with neural stem cells, into sites of severe spinal cord injury in rats. After a few months, new spinal cord tissue had regrown completely across the injury and connected the severed ends of the host spinal cord. Treated rats regained significant functional motor improvement in their hind legs.
In the future, our technology would be part of the personalized medicine approach where 3D-printed spinal cord scaffolds would be fabricated according to an MRI of the injured patient. The implant would fit precisely into the injury site and integrate seamlessly, supporting regain of lost functions.