Humans with severe spinal cord injuries have been offered hope by scientists who have successfully treated rats with the same condition.

Using 3D printing to create the scaffolding around which stem cells can implanted, researchers from the University of California, San Diego, helped rats to regain significant motor control in their hind legs.

The implants contain dozens of tiny channels, just 200-micrometres wide, which guide neural stem cells and axon growth along the spinal cord injuries.

Due to the biocompatible design of the scaffolding, the body's blood vessel system can naturally grow so that the nerve fibres are kept alive and fed with nutrients as well as discharge waste.

According to the team, the printing technology it used was capable of creating each implant in less than two seconds per each device - whereas traditional printers would have taken several hours.


Their work was published in the journal Nature and explains how the team printed a spinal cord which was loaded with neural stem cells.

In the tests on rats, the scaffolds helped the animals regrow tissue and the stem cells nerve fibres inside of the scaffolding expanded out into the host spinal cord.

Image: The 3D printed implant used as scaffolding. Pic: Jacob Koffler, Wei Zhu, UC San Diego

Professor Mark Tuszybski, a trained doctor and scientist who directs the Translational Neuroscience Institute at UC San Diego School of Medicine and senior co-author of the paper, hailed the study.

"In recent years and papers, we've progressively moved closer to the goal of abundant, long-distance regeneration of injured axons in spinal cord injury, which is fundamental to any true restoration of physical function," said Professor Tuszynski.

The team describes axons as "the long, threadlike extensions on nerve cells that reach out to connect to other cells".

"The new work puts us even closer to real thing," added Dr Kobi Koffler, a co-author of the paper and an assistant project scientist in Professor Tuszynski's lab.

It puts research even closer to the real thing "because the 3D scaffolding recapitulates the slender, bundled arrays of axons in the spinal cord," Dr Koffler said.

"It helps organise regenerating axons to replicate the anatomy of the pre-injured spinal cord."

Professor Shaochen Chen, another of the paper's co-authors and a professor of nanoengineering and a faculty member in the Institute of Engineering in Medicine at UC San Diego, explained the printing technology.

"Like a bridge, it aligns regenerating axons from one end of the spinal cord injury to the other," said Dr Chen.

"Axons by themselves can diffuse and regrow in any direction, but the scaffold keeps axons in order, guiding them to grow in the right direction to complete the spinal cord connection."