This is a microscopic view of the lab-grown human muscle.
Image credit: Duke University
"The beauty of this work is that it can serve as a test bed for clinical trials in a dish," says study leader Nenad Bursac, associate professor of biomedical engineering at Duke.
"We are working to test drugs' efficacy and safety without jeopardizing a patient's health and also to reproduce the functional and biochemical signals of diseases - especially rare ones and those that make taking muscle biopsies difficult."
Bursac and his team says there is a strong focus on the development of in vitro models for use in medical research, motivated by ethical factors - such as reducing animal testing - and the need to improve health outcomes in human patients.
In June last year, Medical News Today reported on the creation of lab-grown miniature human hearts by researchers from Abertay University in the UK, while another study revealed how researchers from the University of Texas successfully grew human lungs from the cells of deceased children.
But Bursac and his team say while much progress has been made in creating in vitro models for liver, lung and cardiac tissues, there has been little progress toward the development of human skeletal muscle.
"This is of particular concern as there are a wide range of metabolic, neuromuscular and dystrophic disorders involving skeletal muscle that are under investigation and still lacking therapies," they note.
Lab-grown muscle 'closely mimics responses of native human muscle'
For their study, published in the journal eLife, the researchers isolated "myogenic precursors" from human muscle biopsies. These are cells that have not yet developed into muscle tissue, but have advanced beyond stem cells.
Next, the team increased the abundance of myogenic precursors by more than 1,000, before subjecting them to a "hydrogel molding technique" originally created for rodent cells. This involved placing the cells into a 3D scaffolding consisting of a hydrogel, which allowed the cells to become adjoined, functioning muscle tissue that the researchers call "myobundles."
The team then subjected the myobundles to electrical pulses and found that it contracted in response - something they say has never been seen in lab-grown human muscle. This showed that the signaling pathways in the muscle were fully functional.
The video below shows the muscle tissue contracting when exposed to electrical stimulation:
The researchers also assessed the myobundles' response to an array of drugs - including statins, used to lower cholesterol, and clenbuterol, a fat-burning drug most commonly used by athletes.
They found the statins caused abnormal fat build-up at high doses, while clenbuterol increased muscle wastage at high doses. The researchers say both of these effects have been seen in humans. In addition, they note clenbuterol does not trigger muscle wasting in rodents at the doses used in this study, indicating that the muscle was demonstrating a fully human response.
Commenting on their creation, the researchers say:
"Overall, these results suggest that myobundles closely mimic the functional responses of native human muscle through multiple signaling pathways and could provide a preclinical assay for predictive screening of novel therapeutics for a broad range of muscle-related disorders."
Bursac says the team wants to use their lab-grown human muscle to develop personalized medication for patients with muscle-related conditions. "We can take a biopsy from each patient, grow many new muscles to use as test samples and experiment to see which drugs would work best for each person," he explains.
They are also looking at creating lab-grown contracting human muscles from induced pluripotent stem cells rather than cells taken from human biopsies, which could ease the challenges presented by certain muscular diseases.
"There are a some diseases, like Duchenne muscular dystrophy, for example, that make taking muscle biopsies difficult," says Bursac. "If we could grow working, testable muscles from induced pluripotent stem cells, we could take one skin or blood sample and never have to bother the patient again."
In September 2014, MNT reported on a study published in Nature Medicine, in which researchers from the Sanford-Burnham Medical Research Institute in La Jolla, CA, revealed they may have found a way to trigger tissue repair in damaged muscles, which could lead to new treatments for muscle-wasting disorders.