TOKYO -- A health ministry task force has conditionally approved a university team's plan to treat heart disease with sheets of muscle cells created from induced pluripotent stem (iPS) cells in a first study of its kind. The decision raises hope of advancements in treatment involving large numbers of cells, though there remain concerns that any complications could deal a blow to research.
The groundbreaking study will be conducted by a team of researchers at Osaka University, led by professor Yoshiki Sawa, a specialist in cardiovascular surgery. They will place thin, round sheets of heart muscle cells, created with iPS cells taken from other people, onto the hearts of three patients suffering from serious heart failure.
The sheets, each just 0.05 millimeters thick, are expected to release a wider diversity of cytokines -- proteins that can act on heart muscles and lead to the creation of new blood vessels -- than previous sheets made from patients' leg muscle cells.
Sawa stresses that "all conceivable safety checks have been performed." Because the sheets are made from other people's cells, patients in the study will have to be given immunosuppressants, but the treatment costs and preparation time are expected to be reduced compared to methods using the patients' own cells.
One cause for apprehension is the fact that the transplanted sheets will contain around 100 million cells -- far more than the hundreds of thousands in previous studies treating intractable eye diseases. While the heart is less susceptible to cancer than other organs, researchers cannot rule out the possibility that if immature cells that have not completely turned into muscle cells become mixed up in the sheets, they could turn cancerous or result in benign tumors forming.
Experts say that if the research goes smoothly, then it could provide a boost for other research using large numbers of cells. But at the same time, any serious problems could halt regenerative medical research using iPS cells altogether.
Sawa commented, "Even if a tumor does develop, because the cells come from another person, it is expected that it will disappear after the suppressants are withdrawn and the person's natural immune system kicks in."
That issue aside, the question of how to evaluate the effectiveness of the treatment remains. In an overseas science journal last year, institutions including Tohoku University announced the results of a three-year follow-up study on 730 patients whose heart pumping functions were similar to those targeted in the latest research. That study found that about 40 percent of patients showed improvements after taking standard medicines alone. The purpose of the latest research is to test the safety of the treatment, but since the patients will also continue to take such medicines, the question of how to assess the effectiveness of the sheets from here on is likely to arise.
(Japanese original by Suzuko Araki and Momoko Suda, Science and Environment News Department)