MIT engineers have developed a microfluidic device that replicates the neuromuscular junction, the crucial connection between nerves and muscles. The device, about the size of a quarter, contains a single muscle strip and a small set of motor neurons. The researchers were able to influence and observe the interaction between the two in a realistic (realistic) three-dimensional matrix.
The researchers genetically modified the neurons in the device to respond to light. By projecting light onto (these) neurons, these cells can be precisely stimulated, sending signals to fire muscle fibers. The researchers also measured the force with which the muscles within the device twitched or contracted after being stimulated. Novel microfluidic device replicating the neuromuscular junction. The device contains small clusters of neurons (green) and individual muscle fibers (red).
The bottom fluorescence image shows a motor neuron emitting axons toward the muscle strip across a distance of about 1 mm. The findings, published online August 3, 2016 in the journal Science Advances, may help scientists understand and identify drugs to treat amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease) and other neuromuscular-related diseases.
“The neuromuscular junction is involved in many disabling diseases, some of which are brutal and deadly, and many have yet to be discovered,” said Sebastien Uzel, a graduate student in MIT’s Department of Mechanical Engineering who led the study. “We hope to be able to form the neuromuscular junction in vitro, so that help us understand certain disease activity.” SebasTIen Uzel is now a postdoc at the Wyss Institute at Harvard University.
Since the 1970s, scientists have proposed numerous methods to simulate neuromuscular junctions in the laboratory. Most of these experiments involved growing muscle and nerve cells on petri dishes or small glass substrates. But such an environment is a far cry from the in vivo state, where muscle and nerve cells live in complex three-dimensional environments, often at great distances. “Think of a giraffe,” Uzel said. “The axons from neurons in the spinal cord need to travel a very large distance to connect with the leg muscles.”
To reconstruct a more realistic neuromuscular junction in vitro, Uzel and colleagues constructed a microfluidic device with two important properties: 1. a three-dimensional environment; 2. a compartment that isolates muscles and nerves, thereby simulating two The natural state of separation in the human body. The researchers suspended muscle and neuronal cells in compartments, which were then filled with gel to simulate a three-dimensional environment.
To grow muscle fibers, the research team used muscle precursor cells obtained from mice, which were then differentiated into muscle cells. They injected cells into microfluidic compartments, where they grew and fused to form individual muscle strips. Likewise, they differentiated motor neurons from stem cells and placed the resulting aggregates of nerve cells in a second compartment. Before differentiating the two types of cells, the researchers genetically modified the nerve cells using optogenetic (optogeneTIcs) technology.
Light “allows you to precisely control the cells you want to activate,” said study co-author Roger Kamm, Ceciland Ida Green Distinguished Professor of Mechanical and Bioengineering at MIT. In such a small space, electrodes cannot achieve this.
Finally, the researchers added another feature to the device: force sensing. To measure muscle contractions, they constructed two tiny elastic struts inside the muscle cell compartment, which are located around the muscle fibers and are able to be wrapped by the growing muscle fibers. As the muscles contract, the struts are squeezed together, creating displacements that the researchers were able to measure and convert into mechanical forces.