The stem cell research community is increasingly headed in the direction of finding ways to reverse or work around the age-related decline in regenerative capacity, driven by changes in stem cells and their niches: "Since patients with heart failure are normally elderly, their cardiac stem cells aren't very healthy. We modified these biopsied stem cells and made them healthier. It is like turning back the clock so these cells can thrive again. ... Modified human stem cells helped the signaling and structure of the heart cells, which were biopsied from elderly patients. Researchers modified the stem cells in the laboratory with PIM-1, a protein that promotes cell survival and growth. Cells were rejuvenated when the modified stem cells enhanced activity of an enzyme called telomerase, which elongates telomere length. Telomeres are 'caps' on the ends of chromosomes that facilitate cell replication. Aging and disease results when telomeres break off. ... There is no doubt that stem cells can be used to counter the aging process of cardiac cells caused by telomere degradation. ... The technique increased telomere length and activity, as well as increasing cardiac stem cell proliferation, all vital steps in combating heart failure. While human cells were used, the research was limited to the laboratory. Researchers have tested the technique in mice and pigs and found that telomere lengthening leads to new heart tissue growth in just four weeks. ... Modifying aged human cardiac cells from elderly patients adds to the cell's ability to regenerate damaged heart muscle, making stem cell engineering a viable option."