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Stem cells may trigger immune repair to mend hearts

2 December 2019
Appeared in BioNews 1026

Stem cell therapies may become redundant in repairing cardiac function after a heart attack, suggests a new study in mice.

It showed how stem cell treatments can heal hearts by triggering an immune response – which can be achieved by using a chemical instead.

'This work is paradigm-shifting because it demonstrates a mechanism to explain a perplexing phenomenon that has intrigued cardiologists as a result of decades of cardiac stem cell trials,' Dr Jonathan Epstein at the University of Pennsylvania's Perelman School of Medicine in Philadelphia told The Scientist.

Stem cell therapies to repair damaged heart tissue are currently being tested in human clinical trials. In these treatments, human stem cells are injected into the heart and this leads to an improvement in heart function. However, how this works is not fully understood.

One possibility is that the injected stem cells are incorporated into the heart tissue and repair the damage. However, the latest study, published in the journal Nature, suggests that this may not be the case. Instead, the study indicated that the repair is actually a result of triggering the innate immune response.

Researchers injected different types of stem cell or a chemical inducer (zymosan) of the innate immune response into an experimental mouse model of heart disease. They saw improvement in heart function that was similar in all cases, and showed that this repair occurs via activation of macrophage cells of the innate immune system. 

'The innate immune response acutely altered cellular activity around the injured area of the heart so that it healed with a more optimised scar and improved contractile properties,' said Dr Jeffery Molkentin at the University of Cincinnati and Cincinnati Children's Hospital Medical Centre, Ohio, who led the study. 'The implications of our study are very straightforward and present important new evidence about an unsettled debate in the field of cardiovascular medicine.'

The work could open up new possibilities for optimising the treatments currently in development, as well as alternative new therapies.

'If there is a chemical off-the-shelf, it would be a much more feasible therapy [than stem cell transplants],' Dr Kory Lavine at Washington University in St Louis, Missouri, told Nature News.

Activation of the Immune System Underlies Cardiac Cell Therapies
The Scientist |  27 November 2019
An acute immune response underlies the benefit of cardiac stem-cell therapy
Nature |  27 December 2019
Stem-cell therapies use immune system to repair broken hearts
Nature News |  27 November 2019
Stem cell therapy helps broken hearts heal in unexpected way
Science Daily |  27 November 2019
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