Researchers have discovered that cells taken from the muscles of adult mice have a remarkable ability to form into many different types of blood cells hinting that muscle cells could constitute a hitherto untapped therapeutic resource, in lieu of appropriate bone marrow.

Once transplanted into other adult mice, the muscle cells in question, which were extracted by mincing mouse muscle and digesting it with enzymes, generated blood cells ten to fourteen times more quickly than whole bone marrow. And they continued to contribute to all the major blood lineages for at least three months. Furthermore, when the cells were transplanted a second time from these mice into secondary recipients, they retained their ability to regenerate.

This discovery, reported in the Proceedings of the National Academy of Sciences1, is the latest instalment in the extremely fast-moving stem cell story. Stem cells are the subject of massive research effort, because, by definition, they have potential. They are cells that haven’t decided yet what they are going to be when they grow up. Like all bright young things, their future is a wealth of possibilities, and their fate is determined by a combination of basic aptitudes, early conditioning and environmental influence.

A neuronal stem cell, for example, could, depending on where it finds itself, blossom into any one of the myriad cell types it takes to make a brain. A 'haematopoietic' stem cell, as the basic building blocks of blood are properly called, could become a platelet, a red cell, or one of several types of white blood cell. Usually, haematopoietic stem cells hark from the bone marrow -- this is why blood disorders like leukaemia are often treated with bone marrow transplants.

But the curious thing here is that the cells discovered by A Goodell, and colleagues, of Baylor College of Medicine, Houston, Texas, came from muscles. The researchers speculate that these multi-talented cells might actually be skeletal muscle stem cells. These make up between one and six percent of all muscle cells, usually proliferating when a bit of muscle growth or repair is called for.

If what was involved here was indeed skeletal muscle stem cells (and this will take some proving), then, the researchers hypothesise, muscle and blood stem cells may be more similar than was previously thought -- their fate depending more on where they are than where they came from. This, and a slew of other recent work suggests, as Goodell's team put it, "that stem cells derives from adult tissues may retain a previously unrecognised degree of plasticity".

Jackson, K.A., Mi, T. & Goodell, M.A. Hematopoietic potential of stem cells isolated from murine skeletal muscle PNAS 96, 14482-14486 (1999).