Neuromuscular diseases are caused by problems in the way muscle cells, motor neurons, and peripheral cells interact. Researchers from the Max Delbrück Center for Molecular Medicine in the Helmholtz Association sought to create human-specific cell culture models to find effective therapies for neuromuscular diseases and study how motor neurons in the spinal cord interact with muscle cells. The researchers report they have developed a self-organizing neuromuscular junction model using pluripotent stem cells. They say their model will allow high-throughput drug screening for different neuromuscular diseases and allow them to study the most promising candidates in patient-specific organoids.
Their findings are published in Nature Communications in an article titled, “Efficient generation of a self-organizing neuromuscular junction model from human pluripotent stem cells.”
“The complex neuromuscular network that controls body movements is the target of severe diseases that result in paralysis and death,” the researchers wrote. “Here, we report the development of a robust and efficient self-organizing neuromuscular junction (soNMJ) model from human pluripotent stem cells that can be maintained long-term in simple adherent conditions.”
The researchers led by Mina Gouti, PhD, head of the Stem Cell Modeling of Development and Disease Lab at the Max Delbrück Center, had already developed a three-dimensional neuromuscular organoid (NMO) system. “One of our goals is to use our cultures for large-scale drug testing,” said Gouti. “The three-dimensional organoids are very large and can’t be grown for a long time in the 96-well culture dish that we use to perform high-throughput drug screening studies.”
Their self-organizing neuromuscular junction model using pluripotent stem cells “will allow us to perform high-throughput drug screening for different neuromuscular diseases and then study the most promising candidates in patient-specific organoids,” explained Gouti.
To establish the 2D self-organizing neuromuscular junction model, the researchers first had to understand how motor neurons and muscle cells develop in the embryo.
“We tested a number of hypotheses. We found that the types of cells we needed for functional neuromuscular connections originated from neuromesodermal progenitor cells,” said Alessia Urzi, a doctoral student and lead author of the paper. Urzi found the right combination of signaling molecules that cause human stem cells to mature into functional motor neurons and muscle cells with the necessary connections between the two. “It was exciting to see the muscle cells contracting under the microscope,” said Urzi. “That was a clear sign we were on the right track.”
To test the validity of the model, Urzi used human iPSCs from patients with spinal muscular atrophy, a severe neuromuscular disease that affects children in the first year of their life. The neuromuscular cultures generated from the patient-specific induced pluripotent stem cells showed severe problems with the contraction of the muscle resembling the patient’s pathology.
Looking toward the future, Gouti and her team want to perform high-throughput drug screening to identify novel treatments for patients with spinal muscular atrophy and amyotrophic lateral sclerosis. “We want to start by seeing if we can achieve more successful outcomes using new combinations of drugs to improve the life of patients with complex neuromuscular diseases,” concluded Gouti.