Stem cells repair damaged heart muscle in monkeys

Researchers in Japan have used stem cells from a matched donor to repair damaged heart muscle in macaque monkeys.

Although the use of donor stem cells required immunosuppressive drugs to avoid rejection, this approach could be quicker, cheaper and more practical than using stem cells from the patient themselves, heart experts say.

In the study, published in Nature, researchers injected 400 million immune-matched induced pluripotent stem cells (iPS cells) from one macaque into the hearts of five macaques with heart failure. They found that the new heart cells replaced 16 percent of the damaged heart muscle, which then pumped more efficiently.

'We found that monkey cardiac muscle cells derived from induced pluripotent stem cells survived in the damaged monkey heart and electrically coupled with the host heart,' lead researcher Professor Yuji Shiba of Shinshu University, Japan, told ResearchGate. 'In addition, the heart's ability to contract was partially recovered by the transplantation.'

The goal of regenerative medicine has been to take a patients' own cells, convert them to stem cells, and then grow new tissues that can be transplanted back into the patient.

'Ideally, immune rejection would be eliminated if the cells could be derived from the same patient, but this is costly and time consuming at a time when the patient requires immediate treatment,' Dr Sam Boateng of Reading University, who was not involved in the study, told The Guardian.

The present study shows that using a matched donor for the stem cells could be a practical alternative.

'[This] strengthens the case that a bank of pre-prepared matched iPS cells could be used to treat patients, without relying on the long process of reprogramming and differentiating the patient's own cells. This makes iPS cell therapies much more feasible and potentially less expensive,' said Professor Sian Harding of Imperial College London, who was not involved in the study.

The researchers hope to conduct a trial in humans, but must first iron out some problems. All of the monkeys developed abnormal heart rhythms in the first few weeks after transplantation, but Professor Shiba said that these were 'transient and non-lethal'. 'I think we can manage this side effect in the clinic,' he added.

Professor Sir Martin Evans of the University of Cardiff, who was not involved in the study, called the abnormal heart rhythms 'a serious complication which has been seen in some previous studies and deserves further study', but said that the study was a move in the right direction.