In the quest to restore function after spinal cord injury, researchers at University of California San Diego have come up with a unique tool — a 3D-printed scaffold. This “bioprint” custom scaffold is intended to serve as bridge to place, guide and protect stem cells, enabling them to grow into nerves that can span across the injury.
The UCSD research started making headlines when the study was published in the January 2019 issue of Nature Medicine.
A Jan. 24 article in University of California News explains that 3D printing enables the researchers to take an MRI scan of a lab rat’s spinal cord injury, then run it through a computer program and into a 3D bio-printer. That creates a custom hydrogel bioprint implant precisely matching the injured area of a spinal cord. The next step is to fill the implant with stem cells, then fit it into the injured area of the spinal cord, where it acts as a scaffold across the injury site. The implant provides a clear pathway for the stem cells to grow new nerve cells, which should form connections across the injury site.
The advanced abilities and precision of the 3D bioprinters used in this study allow each printed spinal cord implant to incorporate dozens of tiny 200-micrometer-wide channels (twice the width of a human hair) that guide stem cell and axon growth along the length of the spinal cord injury. The bioprinters, made by Allegro 3D Bioprinting, can create a 2-milimeter-size implant for the rats in the in just 1.6 seconds.
To test the bioprinting process on a human scale, researchers took MRI scans of human spinal cord injuries and printed 4-centimeters-long bio-implants in under 10 minutes.
The inside of the bioprint implant mimics the thin bundled arrays of axons in the spinal cord, and like a pathway or bridge, the implant aligns regenerating axons from one end of the spinal cord injury to the other. This is a big deal because axons by themselves are rather haphazard and can regrow in any direction. The bioprint implant keeps stem cells and axons in order, on the path and growing in the right direction to complete the spinal cord connection.
The environment in and around a spinal cord injury is often toxic and inflammatory, not a safe place for stem cells to be out on their own. This is another area where the bioprint implant shines, as it provides a stable environment that supports the survival of stem cells and shields them from the toxic inflammatory environment of a spinal cord injury.
To date the study has been limited to rats. Researchers grafted 2-millimeter implants, loaded with stem cells, into sites of severe spinal cord injured rats. Within several 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.
The researchers are in the process of improving the technology of this study and testing it on larger animal models to prepare for human testing.
Additional steps include adding proteins to the spinal cord implants that should increase stimulation of stem cell survival and axon outgrowth.
The research study was a joint venture between UC San Diego School of Medicine and UCSD’s Jacobs School of Engineering — in this case bioengineering. And co-senior authors include Mark Tuszynski, professor of neuroscience and director of the UCSD Translational Neuroscience Institute, and co-senior author Shaochen Chen, professor of nanoengineering at the UC San Diego Jacobs School of Engineering and faculty member of the Institute of Engineering in Medicine at UC San Diego.
These 3D bioprints are another important step in the right direction, and unlock yet more doors on the long research journey to — I’m hesitant to use the word cure — restoring function following SCI.