3D-Printed Neuromuscular Structure Is Created in Rat

University of Illinois' “spinobot” may have developed a partial peripheral nervous system.

Researchers from the University of Illinois used the 3D printing process known as stereolithography to polymerize hydrogel structures as part of engineering the world’s first fully functional 3D neuromuscular structure. The 3D-printed neuromuscular structure was connected to a section of a neonatal rat’s spinal cord of. The researchers were able to drive and alter the frequency and variation of muscle contractions by neurochemical modulation.

According to the research paper on the experiment, “Emergence of functional neuromuscular junctions in an engineered, multicellular spinal cord-muscle bioactuator,” the hydrogel skeleton was built like a small bridge consisting of three parts: two pillar structures on either side and a flexible beam component drawn across them. (Image courtesy of the University of Illinois.)

The 3D-printed hydrogel was seeded to the pillar-like structures with a gel containing myoblasts (an embryonic cell that becomes muscle cells) and a cell-extracellular matrix (cell-ECM) containing a mixture of fibrinogen, thrombin, myoblasts and Matrigel. For reference, a cell-ECM is a three-dimensional interconnection of macromolecules that provide biochemical and physical support to their surrounding cells.

After experimentation began, the skeletomuscular system of the biobot (dubbed “spinobot”) spontaneously contracted. Researchers measured the active tension of the contractions at 0–40μN.

The experiment was performed outside of the rat’s body (ex vivo) and neuromodulation to the 3D-printed neuromuscular structure and the rat’s own skeletomuscular system was performed by applying the neurotransmitter glutamate, which produced different sequences and patterns of variations in the frequency of muscle contractions.

These contractions occurred on the neuromuscular structure near the first and second lumbar regions of the neonatal rat’s spine, possibly forming functional neuromuscular junctions with the hindlimb central pattern generator.

Bottom Line

If the neuromuscular junctions (a type of mammalian synapse) formed with the hindlimb central pattern generator (which contains internal spine circuitry), then the experiment may have shown that a partial development of a peripheral nervous system occurred.

In other words, the world’s first Franken-rat.