A prototype spinal cord implant being printed. (Image courtesy of the University of Minnesota.)
Researchers at the University of Minnesota have made a prototype of a 3D-printed implant with living cells that could alleviate spinal cord injuries.
The project was the result of a collaboration between engineers (who handled the 3D printing aspect) and medical researchers (who handled the development of the cells). “Everything came together at the right time,” said Ann Parr, a medical researcher and one of the coauthors of the study. “We were able to use the latest cell bioengineering techniques developed in just the last few years and combine that with cutting-edge 3D printing techniques.”
In their prototype, the researchers start with adult cells, and essentially “rewrite” them to become neuronal stem cells, “undifferentiated” cells that can become any kind of neuron. Then, the engineers print these cells onto a silicone guide, using a technique in which the same machine prints both the guide and the cells. The scaffold was printed layer by layer, along with hydrogel, a special ink that coats and preserves the stem cells.
The implant is filled with tiny scaffold channels that guide the cells’ axons, the long “stems” of the nerve cells. When the implant is inserted into a person’s spine, the cells in it will connect to the healthy tissue on either side of the spinal injury. The initial cells will be taken directly from the patient to reduce the likelihood that the patient’s body will reject the implant.
While the technology to print live cells into plastic implants already existed, the tricky part was printing with delicate neuronal stem cells. “The hard part is keeping the cells happy and alive,” said Michael McAlpine, the study’s other lead coauthor. “We tested several different recipes in the printing process. The fact that we were able to keep about 75 percent of the cells alive during the 3D printing process and then have them turn into healthy neurons is pretty amazing.”
While the prototype still needs to be tested on animals, it looks hopeful for the nearly 285,000 people in the United States who suffer from spinal cord injuries. “This is a very exciting first step in developing a treatment to help people with spinal cord injuries,” Parr said. “Currently, there aren’t any good, precise treatments for those with long-term spinal cord injuries.”
The implant probably won’t allow people to walk, but that’s not the researchers’ goal. “There’s a perception that people with spinal cord injuries will only be happy if they can walk again,” Parr said. “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.”