Japanese researchers from Keio University School of Medicine in Tokyo and colleagues from the National Institute for Child Health and Development in Tokyo, Tokyo Women’s Medical University, and Kanazawa University showed that cells from menstrual blood may be helpful in repairing damaged heart tissue.

Nine women volunteered to donate menstrual blood from which the researchers harvested the precursor cells, called mesenchymal cells (MMCs) and cultivated them for a month, putting them together with heart cells from rats. About 20 percent of these cells began beating spontaneously and eventually formed sheets of heart muscle tissue.

The success rate is 100 times higher than the 0.2 to 0.3 percent for stem cells taken from human bone marrow, researcher Shunichiro Miyoshi, a cardiologist at Keio University's school of medicine, told French news agency AFP.

“There may be a system in the near future that allows women to use it for their own treatment,” Miyoshi said.

He further added that the cells can be stored for a long time in a tube the size of a finger and cultivated when necessary.

"In proper storage, we would be able to stock up a tremendous count of cells in a small space. If they are not used for 100 years, they could stay there for 200 years or 300 years" waiting for a perfect match, he said.

According to the study, rats who had suffered heart attacks improved after they received the menstrual blood cells. However, Miyoshi was “not entirely happy” with the results of the experiment.

“I guess this can't be ready for clinical use yet. There should be a definite factor that turns the cells into a heart and we want to find it,” he said.

The study’s findings appeared in the online edition of the U.S. journal Stem Cell.