For the first time, living tissue cells from an animal have been changed into their previous state as embryonic stem cells by researchers at the Spanish National Cancer Research Centre in Madrid.

For the first time, living tissue cells inside an animal have been changed into their previous state as embryonic stem cells by researchers at the Spanish National Cancer Research Centre in Madrid.

The study used genetically modified mice that reacted to a specific drug by reversing the development of their tissue.

Cells that had regressed into being embryonic quickly turned into tumors in the mice, because they were given no genetic information as to which body part to form into.

Professor Robin Ali, from the Institute of Ophthalmology in London, who is also working with stem cell technology said: “This is a really elegant study with important implications for the field. It will be a monumental task to prove this is safe, as what you're doing is innately dangerous, but it is exciting as it's potentially a new strategy for regenerative medicine.”

This kind of research is a long way from having clinical applications, but the idea of being able to regress different damaged tissue back to its embryonic stage means that it could potentially be used in treatment for heart attacks or strokes.