When a MRL mouse’s finger is cut lower than the tip it is able to form a structure but not the full digit. Amphibians can regenerate limbs. Mammals can’t. Now two teams of bioscientists are out to correct our evolutionary shortcoming under a recent $7.6-million Darpa grant. The current goal is to produce a mammalian blastema—the cell bud that forms a new amphibian limb. In four years, Darpa wants a regrown mouse finger. Human research is the logical next step. Darpa funds will help scientists bolster preexisting research on the genetic and cellular processes of tissue regeneration. “Even if we fail,” says Muneoka, a team leader, “we’ll get better wound-healing. Mammals can already regrow limbs—to a point. Young children who lose fingertips can remake bone and tissue perfectly.
The scientists believe that a mixture of cellular and extracellular components —maybe hormones, vita- min A, fibroblasts—could be applied to fresh amputations to steer them toward regeneration. “We grow a whole human in nine months,” Badylak says. “A limb should be nothing”