An Australian company is doing just that. In Stage II clinical trials in the United States, Mesoblast Ltd. (ASX: MSB) showed that its stem cell-based therapy, Revascor, showed sustained improvement in heart muscle function six months after patients received the minimal dose of the drug in a single injection. Ultimately, more-powerful pluripotent stem cells will do the same thing even more efficiently, but this product could come to market first. The company is currently presenting its findings at the American Heart Association annual conference.

Researchers at the Northwestern University Feinberg School of Medicine have also been trying to repair damaged hearts through stem cell therapies. In a double-blind placebo-controlled study, they transplanted adult stem cells into patients with severe angina and heart disease. The results were astonishing: Patients that had received the stem cell treatment doubled the amount of time they were able to walk without feeling pain, and overall experienced less pain over the course of the day. The stem cell therapy caused new blood vessels to grow in the heart tissue, supplying the muscle with a more adequate blood supply.

Also, University of California researchers have found some of the molecular triggers that lead to aging in muscle tissue. Researchers took biopsies from the quadriceps of the participant’s muscle at the beginning of the study and then immobilized it in a cast for two weeks. Immobilized muscle tends to atrophy. After removing the casts, the participants went through an exercise regimen to restore the lost muscle mass and further biopsies were taken.

They found that the actual number of adult stem cells responsible for tissue regeneration is halved in old muscle compared with young muscle. They also found that younger participants had four times more regenerative cells working at repairing the muscle compared with older subjects in the study. They knew from previous studies that there are biochemical signals that tell stem cells where to go to repair muscle tissue and that these signals decline as part of aging.

The molecular receptor on the adult stem cells, called Notch, causes growth when it is activated. These cells also have a molecular receptor for the TGF-beta protein that reduces the stem cell’s ability to divide when it is excessively activated. Past studies in mice revealed that aging causes a decline in the Notch receptor and an increase in the amount of TGF-beta. This state causes a decline in the ability of the stem cells to rebuild tissue.

The latest study showed that these pathways found in mice are also present in humans. However, this study also showed for the first time the importance of another biochemical regulator of the activity of the Notch receptor. Known as MAPK, this enzyme is well-known for its function in forming organs in a wide variety of animals, from worms to insects and mammals and now to humans. The researchers discovered that when they raised old human muscle in a culture and forced the activation of this enzyme, the ability of the muscle to regenerate was improved. This is a technology with enormous financial promise.