Moving toward regeneration

The skin, the blood, and the lining of the gut—adult stem cells replenish them every day. But stem cells really show off their healing powers in planarians, those humble flatworms fabled for their ability to rebuild any missing body part.

Scientists first hypothesized in the late 1800s that planarian stem cells, which normally gather near the worms’ midlines, can travel toward wounds. But the next century produced evidence both for and against that idea. Armed with modern tools, Howard Hughes Medical Institute and Stowers Investigator Alejandro Sánchez Alvarado, PhD, decided to revisit the question.

When they tracked stem cells in the flatworm Schmidtea mediterranea, Sánchez Alvarado’s team found the worms’ stem cells—known as neoblasts—march out, multiply, and start rebuilding tissues lost to amputation. “We were able to demonstrate that fully potent stem cells can mobilize when tissues undergo structural damage,” says Sánchez Alvarado. “And these processes are probably happening to both you and me as we speak, but are very difficult to visualize in organisms like us.”

Stem cells hold the potential to provide an unlimited source of specialized cells for regenerative therapy for a wide variety of diseases, but delivering human stem cell therapies to the right location in the body remains a major challenge. The ability to follow individual neoblasts opens the door to uncovering the molecular cues that help planarian stem cells navigate to the injury site, and ultimately may allow scientists to provide therapeutic stem cells with guideposts to their correct destination.

The study was published in the October 1, 2012, issue of Development.