From the Philadephia Enquirer, a look at one corner of the regenerative medicine research community: "when tendons are damaged in a fetal mouse, they grow back almost like new. In a recent breakthrough, researchers found that this occurs even when the fetal tissue is transplanted into an adult. Now they are starting to figure out why, in hopes of someday helping people heal better. At the University of Pennsylvania, two main avenues are being explored: Experiments with lab animals suggest that part of the answer lies with certain 'growth factors' secreted by fetal cells. And scientists are trying to give the healing process an artificial boost by implanting 'scaffolds' - pieces of stretchy fabric that guide the orderly growth of new, healthy cells. ... The work is part of a broader field, less than two decades old, called tissue engineering - coaxing the repair or regrowth of bodily tissues through a combination of artificial and natural means. Scientists in the booming field have made headway with heart valves, bladders, liver and skin cells. ... Fifteen years ago, tissue engineering was considered science fiction. Now it's reality."