Mice that had been genetically engineered to develop tumours failed to do so. Instead, the animals grew up to be huge and very hairy. And when the tips of the pups’ toes were clipped off in a routine tagging procedure, they often grew back. What was different about these mice was that they carried a protein, Lin28a, which is generally produced only in developing embryos. Lin28a has already garnered attention for its involvement in the functioning of stem cells and in cancer. A study published today in Cell1 now shows that this protein can improve tissue repair — even in adults. In mice genetically modified to produce the protein throughout their lives, the animals’ hair grew faster than normal and puncture wounds in their ears healed almost completely. “We were just so shocked that such a small change in this gene could have profound effects on a complex regenerating tissue,” says Hao Zhu, a cell biologist at the University of Texas Southwestern Medical Center in Dallas and an author on the study.
Resetting cells using embryonic genes has been seen before, most prominently in the creation of cells known as induced pluripotent stem cells, which acquire an embryonic-like state after a suite of genes is activated. But the latest study reveals that such de-ageing changes can be made not just in cultured cells, but in developed tissues within an organism. It suggests that it might be possible to make older tissues behave more like young ones, which are much better at repairing damage. In mammalian fetuses, for example, even deep wounds can heal without scarring.