By: Alison Motluk, NewScientist.com news service

Stem cells derived from human menstrual blood have, in mice, prevented limbs with restricted blood flow from withering. Trials in humans facing amputations are expected to start next year.

Last November, scientists working for MediStem Laboratories, in San Diego, California, announced that they had discovered adult stem cells within the menstrual blood collected from two women. They claimed the cells were shed from the endometrium, which lines the uterus and has to be rebuilt every month.

Now Thomas Ichim, of MediStem, and his team have published a proof-of-principle study in mice, showing that the endometrial stem cells revitalise damaged limbs in much the same way that bone-marrow-derived stem cells do.

The researchers induced "critical limb ischaemia" � damagingly low blood flow in the legs of 16 healthy mice. Immediately after, then again on days 2 and 4, the researchers injected half of the animals with 1 million endometrial stem cells in the hind-limb muscle, just below the injury. By day 14, tissue in the legs of the control mice had begun to die. The limbs of the treated mice, by contrast, were all alive, although two of them had some difficulty walking.

The finding suggests, say the authors, that endometrial stem cells can stimulate blood-vessel growth. Endometrial stem cells appear not to provoke an immune reaction, opening the possibility of developing an "off the shelf" cell population.

Some 150,000 people in the US lose limbs to critical limb ischaemia every year, and there is no cure. Ichim hopes to begin trials in this patient population sometime next year. "These are people who are going to get their legs amputated," he says.

Caroline Gargett, who studies menstrual stem cells at Monash University in Clayton, Australia, thinks it's too early to be studying these cells in humans but applauds the mouse results. "I do think cells coming out of menstrual blood are highly regenerative," she says.

Journal reference: Journal of Translational Medicine (DOI: 10.1186/1479-5876-6-45)