SAN DIEGO -- Researchers from San Diego State University's Heart Institute rejuvenated damaged cardiac tissue removed from older heart-failure patients, using modified stem cells, the university announced Thursday.

University officials said the research could eventually lead to new treatments for heart-failure patients.

"Since patients with heart failure are normally elderly, their cardiac stem cells aren't very healthy,'' said Sadia Mohsin, a post-doctoral research scholar and one of the study's authors. "We modified these biopsied stem cells and made them healthier. It's like turning back the clock so these cells can thrive again.''

Researchers used stem cells modified with a protein called PIM-1 to increase the activity of the enzyme telomerase, which can lengthen telomeres.

 Telomeres --- DNA sequences on the ends of chromosomes -- keep the chromosomes from losing DNA base pairs during cellular replication but lose base pairs themselves during the process. If telomeres become too short, the chromosome can't replicate.

According to Moshin, modifying aged cardiac cells added to the cells' ability to regenerate damaged heart muscle.

"This is an especially exciting finding for heart failure patients,'' Moshin said in a statement. "Right now we can only offer medication, heart transplantation or stem cell therapies with modest regenerative potential. But PIM-1 modification offers a significant advance for clinical treatment.''

While the research involved human cells, the work 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,'' according to a university statement.

The study, supported by the National Institutes of Health, was presented this week at the American Heart Association's Basic Cardiovascular Sciences 2012 Scientific Sessions and published in the Journal of the American College of Cardiology.