The majority of a muscle is formed from bundles of muscle fibres which are long cells containing many nuclei. Muscles also contain many other types of cells, including stem cells. Stem cells are part of the body’s repair system. They can generate other types of cells and can also make copies of themselves. Skeletal muscles contain a type of stem cell called satellite cells. When muscle fibres are damaged they send chemical signals to satellite cells telling them to form new muscle fibres or to fuse with existing fibres to repair the damage. At the same time some satellite cells copy themselves to ensure enough stem cells are available to continue to repair and replace muscle fibres in the future.

There are a number of different types of stem cells that scientists think may be used in different ways to develop treatments for Duchenne. The main stem-cell-based approaches currently being investigated are:

* Producing healthy muscle fibres: Scientists hope that if stem cells without the genetic defect that causes Duchenne can be delivered to patients’ muscles, they may generate working muscle fibres to replace the patient’s damaged ones.

* Reducing inflammation: In Duchenne, damaged muscles become very inflamed. This inflammation speeds up muscle degeneration. Scientists believe certain types of stem cells may release chemicals that reduce inflammation, slowing the progress of the disease.

There are currently no stem-cell-based therapies for Duchenne. Research has provided some exciting avenues for potentially effective future treatments. A lot of work is still needed to determine whether these treatments will be safe and effective in humans. The main challenges scientists still need to address are:

* Preventing immune rejection of transplanted cells

* Delivering cells in the bloodstream to reach all affected muscles

* Overcoming the low engraftment of transplanted cells. With bone marrow transplantation, for example, the disease cells are removed. In Duchenne the diseased muscle cannot be removed and so transplanted cells lack "space" to engraft.