Building muscles

A two-step protocol for selecting reprogrammed precursor cells from muscular dystrophy patients may open new avenues for research.
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Microscopy image of the cross-section of the muscle of a mouse after receiving a graft of human induced myoblasts (in green) developed by Guo et al. Image credit: Jing Yan and Katelyn Daman (CC BY 4.0)

Muscular dystrophies are a group of inherited genetic diseases characterised by progressive muscle weakness. They lead to disability or even death, and no cure exists against these conditions.

Advances in genome sequencing have identified many mutations that underly muscular dystrophies, opening the door to new therapies that could repair incorrect genes or rebuild damaged muscles. However, testing these ideas requires better ways to recreate human muscular dystrophy in the laboratory.

One strategy for modelling muscular dystrophy involves coaxing skin or other cells from an individual into becoming ‘induced pluripotent stem cells’; these can then mature to form almost any adult cell in the body, including muscles. However, this approach does not usually create myoblasts, the ‘precursor’ cells that specifically mature into muscle during development. This limits investigations into how disease-causing mutations impact muscle formation early on.

As a response, Guo et al. developed a two-step protocol of muscle maturation followed by stem cell growth selection to isolate and grow ‘induced myoblasts’ from induced pluripotent stem cells taken from healthy volunteers and muscular dystrophy patients. These induced myoblasts can both make more of themselves and become muscle, allowing Guo et al. to model three different types of muscular dystrophy. These myoblasts also behave as stem cells when grafted inside adult mouse muscles: some formed human muscle tissue while others remained as precursor cells, which could then respond to muscle injury and start repair.

The induced myoblasts developed by Guo et al. will enable scientists to investigate the impacts of different mutations on muscle tissue and to better test treatments. They could also be used as part of regenerative medicine therapies, to restore muscle cells in patients.