Already the prized as engines of repair, stem cells have now been engineered to contain a gene that enhances their healing properties by summoning extra blood of vessels to newly formed of tissue. Using the same technique, it should be possible to add other genes to stem cells to make them more efficient at different tasks.

Stem cells have the potential to repair the most tissues in the body. However, new tissue needs new blood vessels to feed it, and stem cells don’t always produce enough of the proteins that encourage blood vessels to grow. So Daniel Anderson at the Massachusetts Institute of Technology exposed human bone marrow stem cells to biodegradable nanoparticies carrying the human gene for vascular endothelial growth factor (VEGF), which attracts blood vessels to injury sites.

When the modified cells were injected into mice whose hind limbs had been injured, the tissue that regrew to repair the damage had three times the blood vessel density of similar tissue in mice given unmodified cells. Four weeks later, only 20 per cent of the mice given modified cells had lost limbs, compared with 60 per cent in mice that received unmodified cells.

Anderson says the nanoparticies could be used to ferry other genes into stem cells to make them more efficient at repair. “It represents a proof of principle for gene enhancement strategies,” agrees Duncan Stewart of the Ottawa Hospital Research Institute in Canada.