A potentially revolutionary breakthrough in the medical field was published in Thursday's edition of the scientific journal 'Cell'. It's achievement? Finding a hormone that may hold the key to giving us a younger heart.

Researchers with Harvard University at Brigham and Women's Hospital have been working with mice in an attempt to understand how the heart ages. What they have been looking for amounts to something of a modern day fountain of youth.

"There have been factors found that are suggested to be aging factors," noted Dr. Richard T. Lee, one of the leaders of the study, "but there has not been identification of a circulating factor that can go the other way, of turning the old tissue into younger tissue."

So the researchers started looking for hormones that could be administered in an attempt to give the mice healthier hearts. They came across one such hormone called GDF-11, and after giving it to the mice, were amazed at the results.

"The change was unbelievably obvious," observed Lee. "Usually we do quite sophisticated quantitative analyses of hearts and the shapes of the cells and things like that. ... You could see what happened from the very first experiment."

Generally when a heart gets older it will expand and harden as compared to its younger version. The hormone appears to keep the heart from becoming too rigid and actually shrinks it back down to its previous size, ensuring a more stable, youthful blood flow.

"When old mouse hearts are exposed to this hormone at the levels the young mice have, then their hearts go back quite dramatically to the appearance of the young mouse heart in just a few weeks," Lee said.

Admittedly, the researchers were not expecting to see such impressive results so quickly. Most of their surprise stems from the fact that this experiment is proving some of our basic assumptions about the heart completely wrong.

"The heart is not known for being a regenerative organ. So I actually secretly suspected that we would not see any effect in these experiments," another leader of the study Amy Wagers said.

More work will still have to be done to see if the same effect will be recognized in humans, though the initial results are very promising. Don't expect a younger heart any time soon though, as the trials for GDF-11's effectiveness in the human population won't even begin for another 4-5 years.