Scientists have revealed a mechanism that causes heart cells to age and identified a drug that can rejuvenate them, according to a study published today in eLife. The drug is now in clinical trials. The results provide the first direct evidence that aging increases proton leakage in heart cells. The findings could lead to new treatments to shore up the leaky membranes and restore heart function. The eLife paper is titled, Reduction of elevated proton leak rejuvenates mitochondria in the aged cardiomyocyte.