"These are from Justin," says Ruth McCarrick-Walmsley, as she slides a dish of cells under a microscope. The view through the eyepiece includes an array of silvery cells, fanned out in curved lines, looking like a school of fish. These bone progenitor cells, derived from an eight-year-old's baby teeth, represent a major advance in finding a cure for a rare, devastating disease that has stymied research for years.
Fibrodysplasia ossificans progressiva, or FOP, is the only disease known to turn one differentiated tissue into another. "It truly is a metamorphosis," says Fred Kaplan, an orthopedics professor at the University of Pennsylvania—the muscles, ligaments and tendons gradually become bone, locking people in deformed poses.
In Kaplan's office, photographs of people with FOP cover his shelves and walls. "These are pictures of patients of mine," Kaplan says with pride, "they're really my children from all over the world." Kaplan has personally seen ...
