Harvard Medical School researchers used human progenitor cells (taken from blood or bone marrow, and able to form different cell types) to grow a network of new blood vessels (capillaries) in a mouse.

The harvested cells were mixed with growth-promoting chemicals and then implanted in mice. Within seven days the human cells grew into fully functional blood vessels that joined up with the host animal’s blood vessels and started transporting blood.

The research could help treat conditions that involve damage to a tissue’s blood supply, such as the damage to the heart after a heart attack. It could also help lab-grown organs to be implanted successfully.