Your seat at the Additive Manufacturing Advantage awaits! Register free for AMA: Energy and AMA: Automotive & Mobility.
Researchers at the University of Minnesota (UMN) have designed a new approach to repairing damaged spinal cords.
Published in Advanced Healthcare Materials, the researchers combined 3D printed scaffolds with spinal neural progenitor cells (sNPCs) that assembled into organoid-like structures and were able to improve partial movement in rats with complete spinal cord injuries. Although still in early stages, the findings offer a glimpse of how engineered tissue structures might eventually help patients who currently have no way to regain lost nerve function.
Spinal cord injury affects more than 300,000 people in the US, often leading to permanent paralysis. While medical care has improved survival and quality of life, treatments that restore lost connections remain out of reach.
Previous studies have shown that sNPCs, can form new links with host tissue when transplanted. But injected cells on their own tend to scatter and lack the structure needed to form organized networks. Led by Ann M. Parr, MD, PhD, Professor of Neurosurgery, the Minnesota team set out to solve this by giving the cells a framework that could guide their growth.
Guiding neurons with silicone scaffolds
For this project, the researchers turned to a custom-built 3D printer equipped with multiple extrusion heads to create scaffolds made of silicone. Each scaffold contained tiny channels designed to imitate the architecture of the spinal cord.
Human induced pluripotent stem cells were first converted into sNPCs, then printed into these channels with a supportive gel. The channels directed the growth of axons and dendrites along defined paths, encouraging the cells to assemble into structures resembling natural spinal cord tissue. In this way, the scaffold provided both support and instruction, shaping how the cells matured.
In the lab, the scaffolds proved capable of sustaining cells for over a year. Within weeks, the sNPCs differentiated into several types of neurons normally found in the spinal cord, including those essential for motor control. Imaging revealed axons filling the scaffold channels and spreading across the surface to form interconnected networks.
Gene analysis showed that the 3D environment produced a broader range of spinal specific neurons than flat cultures, and electrical testing confirmed that the neurons were not only surviving but functioning, firing signals in ways consistent with mature cells.
Encouraged by these results, the team tested the scaffolds in rats with severed spinal cords. Two organoid scaffolds were placed into the gap left by the injury.
Over twelve weeks, the treated animals gradually regained some movement in their hind limbs, while those given empty scaffolds or no scaffold showed little progress. Electrical recordings reinforced the behavioral results, showing that signals from the brain were able to cross the injury site and activate muscles more effectively in the treated rats.
Detailed examination after the study ended provided further insight. A majority of the implanted cells (~63%) matured into neurons, while a portion became oligodendrocytes, and the neurons integrated with the host spinal cord. These neurons projected axons both above and below the injury, forming synapses with existing cells.
In several cases, they developed organized bundles of fibers suggesting the potential for relay-like systems across the damaged area, rather than full relay restoration. The researchers emphasize that the work is still at an early stage, noting that the current tests were limited to animals and relied on silicone scaffolds that cannot remain in the body permanently.
Future studies will focus on biodegradable materials that dissolve as natural tissue forms. They also plan to add other cell types, including dorsal neurons, to restore sensory as well as motor function, and to refine scaffold designs to better mimic the spinal cord’s layered structure.
AM research in spinal repair
The precision of 3D printing allows scientists to design scaffolds that guide nerve growth, offering a structured path to recovery after spinal trauma.
Recently, researchers at Royal College of Surgeons in Ireland (RCSI) University of Medicine and Health Sciences and Trinity College Dublin created a 3D printed spinal implant that blends a soft, tissue-like matrix with conductive fibers designed to deliver electrical stimulation across damaged nerves.
Produced through melt electrowriting, the implant uses polycaprolactone fibers coated with MXene nanosheets, arranged in low-, medium-, and high-density networks to fine-tune conductivity. In lab tests, neurons grew more robustly on MXene-coated fibers, while astrocytes were less reactive and microglia showed no inflammation. Medium-density scaffolds offered the best balance, supporting longer axon growth and more mature neurons under electrical stimulation, pointing to a promising avenue for spinal repair.
Elsewhere, scientists at the University of California San Diego’s School of Medicine and Institute of Engineering in Medicine (IEM) designed a rapid 3D printed spinal cord implant that helped restore movement in rats with serious injuries. The tiny 2 mm scaffolds were printed in just 1.6 seconds, with 200 µm channels that directed stem cell growth and encouraged axons to reconnect across damaged tissue.
Once implanted, the structures supported blood vessel growth and led to notable recovery of hind limb function. To test clinical feasibility, the researchers also printed larger, four-centimeter implants based on MRI data in under 10 minutes, marking an important step toward human applications.
Help choose the 2025 3D Printing Industry Awards winners – sign up for the Expert Committee now!
To stay up to date with the latest 3D printing news, don’t forget to subscribe to the 3D Printing Industry newsletter or follow us on LinkedIn.
While you’re here, why not subscribe to our Youtube channel? Featuring discussion, debriefs, video shorts, and webinar replays.
Featured image shows custom 3D printed silicone scaffold. Photo via McAlpine Research Group / UMN.