ATLANTA (Reuters Health) Mar 13 - Japanese researchers have harvested endometrial stem cells from human menstrual blood. These stem cells have "an extremely higher potential" as a source of cardiomyocytes compared with bone marrow-derived mesenchymal stem cells, they reported at a late-breaker clinical trials session here Sunday at the 55th Scientific Sessions of the American College of Cardiology.

The findings were presented by Dr. Shunichiro Miyoshi on behalf of his colleagues at Keio University School of Medicine, Tokyo. The researchers collected menstrual blood from six women and harvested endometrial stem cells.

They were able to obtain 30 million stem cells from a single menstrual blood cell, compared with a rate of approximately one million stem cells from marrow-derived blood cells, making them a better source of cardiomyocytes, Dr. Miyoshi told Reuters Health.

The endometrial stem cells expressed a high level of cardiac-specific genes. After 5 days of cardiomyocyte induction, about half of the cells contracted "spontaneously, rhythmical and synchronously, suggesting the presence of electrical communication" between the cells, Dr. Miyoshi announced.

Measurements of membrane potential showed action potentials with cardiac pacemaker potential. The cells stained positive for cardiac troponin-I with a striation pattern. After 5 days of induction, these cells made up 24.6% of the total population of stem cells.

Dr. Miyoshi said that marrow-derived stem cells have improved cardiac function, but primarily through neovascularization rather than through cardiomyogenesis. He emphasized that it is important that these cells are derived from younger patients, rather than autologous cells derived from the typically older patients with heart failure. The cells from younger donors should have longer cell division time, reaching senescence later than cells harvested from older donors.