3D printed live neuronal cells. Image courtesy of the University of Minnesota.

Approximately 300,000 people in the United States live with spinal cord injury (SCI), and 17,000 new cases are reported every year. With no cure, the primary treatment option for people with SCI is rehabilitation with a physical therapist combined with medications to control the pain. Given the relatively permanent nature of these injuries, a new study conducted by Dr. Michael McAlpine and Dr. Ann Parr’s groups at the University of Minnesota is particularly exciting. These scientists have developed a 3D-printing technique to generate a network of neuronal cells in the lab, which they hope will be useful to treat patients with long term SCI. This is the first instance of printing and differentiating neuronal stem cells in a lab. Let’s take a look at how they did it!

The investigators started with induced pluripotent stem cells derived from adult cells (ex. blood, skin etc…), which were then used to bioprint the neurons of interest. They not only printed neurons, but also neuronal support cells called oligodendrocytes, which are responsible for ensuring that neurons can transmit messages efficiently. The uniqueness of their approach lies in their printing process, where the cells were printed in the context of a silicone mold. The silicone “guide” promoted neuronal differentiation as well as provided a scaffold for the scientists to spatially organize the architecture of the cells they generated. Both spatial organization and the presence of the neuronal support cells is particularly important because previous studies have shown that while injecting rodents with neural stem cells has improved SCI, the longevity of these results was compromised by a lack of support system for the injected cells. Therefore, the ability to generate both a functional cell type as well as a spatially accurate structure is important to make this neuronal printing system relevant for treating patients.

To confirm that printed cells were functional, the investigators used calcium flux assays, which demonstrated that the neuronal networks generated were able to communicate with each other. Not only were the cells healthy and functional, but their viability was exceptional: 75% of the cells stayed alive, which is remarkable for cells printed in a laboratory.

While there is still a long way to go before this type of treatment can used to treat SCI in humans, the potential for helping people with long term spinal cord injury is significant. Dr. Parr states:

“We’ve found that relaying any signals across the injury could improve functions for the patients. There’s a perception that people with spinal cord injuries will only be happy if they can walk again. In reality, most want simple things like bladder control or to be able to stop uncontrollable movements of their legs. These simple improvements in function could greatly improve their lives.”

The possibility of implanted neuronal stem cells being effective to treat SCI is also being investigated with the CIRM-funded Asterias trial. To check out more information about this work, read our blog post here and the clinical trial details here.