For about a decade, scientists have experimented with the use of stem cells to try and repair the heart, mostly in animals and mostly using stem cells derived from bone marrow.

CNN: It's amazing what the human heart can do

The researchers showed that it could be used to grow mesenchymal stem cells (MSCs), a kind of primitive cell derived from bone marrow that can be easily grown in culture.

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During the next six months, they discovered that up to 2.2% of mature liver cells (hepatocytes) in the female mice were derived from the donated bone marrow.

BBC: First steps towards artificial organs