Wednesday 15 February 2012
New type of muscle stem cell identified
A new scientific publication from the Myology group of the University Pierre et Marie Curie in Paris has recently identified a new population of muscle stem cells. This study shows that these muscle stem cells called ‘progenitor interstitial cells' (PICs) can be isolated from the muscles of very young mice. Once they are isolated and grown in the laboratory, PICs are able to form new muscle when they are reintroduced into the damaged muscles of mice. They showed that PICs can repair muscle as efficiently as satellite cells, the professional muscle stem cells. This work has identified a new source of stem cells in the muscle that may have potential for the development of therapies for muscle disease in the future. However, whether PICs are present in adult muscles and contribute to their regeneration in muscle disease, are all questions that need further study.
Contents:
- What is the idea behind this study and what did the study show?
- What does this mean for patients?
- Further information and links
What is the idea behind this study and what did the study show?
Regeneration and repair of damaged muscles relies on the activity of resident stem cells. Stem cells are a reservoir of cells that, when activated, are instructed to form new tissue. In the case of skeletal muscle, this regenerative capacity has been mainly attributed to a type of muscle stem cell, called satellite cells. These cells are found close to the muscle fibre and are considered the master muscle stem cells. Just recently, cells other than satellite cells have been shown to be helping with muscle regeneration. However, up until now these cells had not been identified and located.
In this study performed by the group of Dr. Sassoon, the scientists looked at the muscles of mice during the first two to three weeks after birth. They found a new type of muscle stem cell located between the muscle fibres, in what is called the ‘interstitium' of the muscle, so the authors called them Progenitor Interstitial Cells, or PICs.
They showed that PICs are more abundant at birth and their number declines in adults, just as for satellite cells. They isolated them from the muscles of young mice and tested the cell's behaviour in the laboratory. These experiments showed that these cells behave like satellite cells, forming new muscle fibres. Next, they tested if PICs could do this when in the mice. So, they reintroduced PICs into the muscle of mice that had been damaged and they showed that PICs are able to form new muscle tissue as efficiently as satellite cells.
What does this mean for patients?
In muscle diseases such as Duchenne muscular dystrophy the muscles weaken and start to waste away. The muscle is lost because the body cannot adequately regenerate and/or repair itself during the progression of the disease. Therefore, promoting the regeneration ability of muscle stem cells would be one way to prevent muscle loss.
Until now satellite cells were considered the main type of cells involved in skeletal muscle regeneration. However, in muscle affected by muscle disease and in aged muscles, satellite cells are eventually exhausted and show a limited regenerative ability. The identification of a new muscle stem cell type represents a new possibility for therapeutic approaches. These cells could be exploited to regenerate diseased or aged muscles. Moreover, the fact that PICs can be easily isolated and grown in the laboratory makes them possible candidates for cell-therapy. It may be possible to increase the numbers of PICs in the laboratory and then reintroduce them to repopulate damaged muscles.
Nevertheless, before this becomes real and applicable to patients a lot of further work needs to be done. For example, the role of PICs in adult muscle has yet to be investigated. The number of PICs declines after birth and their contribution in adult skeletal muscle regeneration is still unknown. Moreover, PICs have only up to now been identified in mice. Whether these cells are also present in human muscles and whether they could also be isolated from humans is a topic for further study.
Further information and links
The full original paper was published in the journal Nature Cell Biology and is available for free through our partnership with Patient Inform. The article is written in technical language with no summary in layman's terms. Click here to access the full article.
More information about the Myology group headed by Dr David Sassoon and their research on muscle stem cells. Dr Sassoon also coordinates Endostem, a group of researchers working towards stem cell therapies for degenerative muscle disease.
This scientific work was supported by funding from the European Community's Seventh Framework Programme project OPTISTEM.
This summary was produced in collaboration with Optistem and any questions can be directed to: optistem-comms@ed.ac.uk
Read about the stem cell research funded by the Muscular Dystrophy Campaign.
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