After a heart attack, your heart can become weak to the point that it's no longer able to effectively supply the rest of your body with blood. This means bad times, especially since patients with severe heart failure have to rely on mechanical devices or transplants, but stem cells derived from a patient's own skin could potentially provide a cure.
Israeli researchers have been able to harvest skin cells from patients with heart failure and convince them to transform into heart cells. And fully functional heart cells at that — the new cells beat just like the real thing. In fact, even though the heart cells are derived from the skin cells of patients who are 50 or 60 years old, the researchers report that the newly created cells are "the equivalent to the stage of [the patient's] heart cells when he was just born."
Since the stem cells used in this experiment come from skin, there's no worries about ethics or morals or anything like that. Apparently, all it takes to reprogram a skin cell into a stem cell is the addition of three genes plus some acid, and with a little tweaking, the cells can be convinced to differentiate into just about whatever you want, including operational heart tissue. The brand new heart tissue was introduced to some existing heart tissue in a petri dish, and and after just a few days, both the new and the old heart cells were beating away in sync. The final step was to implant the new tissue into living rat hearts to see if it would establish connections with existing tissue, and it did.
This research is just a very preliminary first step towards creating custom tissue to solve medical problems, and even the most optimistic projections put this sort of thing at 10-15 years away from being available as a treatment for humans. Still, you could argue that the first step (as the test of an idea or a proof of concept) is the most important and most difficult one, and everything that comes after that is just details. That's what we're hoping for, anyway.