Spinal cord injuries affect more than 300,000 people in the United States, according to the National Spinal Cord Injury Statistical Center. These injuries are often life-changing, leading to partial or complete paralysis. Once the spinal cord is damaged, nerve cells die, and fibers cannot naturally regrow across the injured area. Current treatments mainly focus on preventing further harm and helping patients manage complications. Unfortunately, no therapy has yet been able to fully restore lost movement or sensation.
For years, scientists have looked at regenerative medicine as a possible solution. Stem cells in particular offer hope, because they can turn into many different types of cells, including neurons. But guiding these cells to grow in an organized way and connect properly with the existing nervous system remains a major challenge.
A Printed Scaffold for Healing
Researchers at the University of Minnesota have developed a new approach that may overcome some of these challenges. Their team designed a small, 3D-printed scaffold made of silicone, only 2 millimeters long. This scaffold contains tiny channels that mimic the natural structure of the spinal cord.
To test this, the scientists used human induced pluripotent stem cells (iPSCs). These are stem cells created from ordinary human cells that can be reprogrammed into many different cell types. The team turned them into specialized spinal neural progenitor cells (sNPCs) and placed them inside the scaffold along with a supportive gel.
When grown in the lab, these cells developed into miniature spinal cord tissues known as organoids. The organoids included different types of neurons and stayed active for more than a year. According to lead researcher Guebum Han, the scaffold directs how the nerve fibers grow, creating a “relay system” that can bridge the damaged part of the spinal cord.
Testing in Rats
The next step was to test the method in animals. The researchers implanted scaffolds into rats that had complete spinal cord injuries. Over a 12-week period, they observed promising results:
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Neurons grew axons both above and below the injury, bridging the gap.
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The new cells connected with the rats’ own spinal tissue and formed working synapses.
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The rats with implants showed much better movement compared to those without.
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Electrical tests confirmed that nerve signals were successfully traveling across the injury site.
By the end of the study, most of the implanted cells had turned into neurons. Some also developed into other essential spinal cord cells such as oligodendrocytes and astrocytes, showing the same type of cellular diversity found in normal spinal tissue.
Moving Toward Human Use
Senior author Ann Parr, professor of neurosurgery at the University of Minnesota, highlighted the long-term importance of the study. She explained that regenerative medicine is opening new possibilities for spinal cord research, and their lab is excited to explore ways to translate these “mini spinal cords” into treatments for patients.
The team is now working on several improvements. They want to make the scaffolds biodegradable, so they naturally break down in the body after healing. They are also developing automated printing systems that can produce scaffolds large enough for human-sized injuries. Another future goal is to include sensory neurons, which could restore not only movement but also sensation in patients with spinal cord injuries.
Key Takeaways
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Researchers tested the method on 18 female rats with complete spinal cord injuries; 5 of them received the organoid scaffolds.
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The scaffold was 3D printed from silicone and measured 2 mm long, with three channels for guiding growth.
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Human stem cell–derived progenitor cells survived, grew into neurons, and restored movement in rats without the need for immune suppression.
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Rats regained significant mobility, and nerve signals were restored across the injury.
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The research was supported by the National Institutes of Health and the Minnesota Spinal Cord Injury and TBI Research Grant Program.
Conclusion
The University of Minnesota team has successfully combined 3D printing and stem cell technology to repair spinal cord injuries in rats. Their method allowed new neurons to bridge the injury site, reconnect with host tissue, and restore mobility. While much more testing is needed before human trials, this study shows a hopeful path forward. If refined and proven safe, such technology could one day help people with spinal cord injuries regain movement and independence.
