Scientists have successfully been able to reverse heart failure in animals, after uncovering a previously-unknown part of the organ that is totally self-healing.
The team, from the Texas Heart Institute, focused on the role of Hippo - a “recently identified” signalling pathway that humans have installed from birth to stop their organs growing too big.
But is also responsible for stopping the heart regenerating after a heart attack.
During cardiac arrest, blood flow stops into the heart, and when the muscle is starved of oxygen, parts of it can die.
Unfortunately this muscle is unable to regenerate (like other parts of the body) and instead just forms fibroblast scar tissue.
This scar tissue then weakens over time, and causes heart failure - one of the leading causes of death in the UK, according to the British Heart Foundation, which reports that diseases of the cardiovascular system were responsible for 158,000 deaths in 2015 (latest data available).
Professor James Martin, of the Texas Heart Institute, said: “Heart failure remains the leading cause of mortality from heart disease. The best current treatment for this condition is implantation of a ventricular assist device or a heart transplant, but the number of hearts available for transplant is limited.”
So the team wanted to look at how they could fully reverse the problematic effects of a heart attack, rather than just bypass them with a device.
They wanted to achieve this by silencing the activity of Hippo, that is inhibiting cell proliferation, an evolutionary block limiting the potential for necessary regrowth.
John Leach, first author, said: “When patients are in heart failure there is an increase in the activity of the Hippo pathway….this led us to think that if we could turn Hippo off, then we might be able to induce improvement in heart function.”
The study, published in the journal Nature, used a mouse model to test the effect of turning off Hippo, and they found that the effect was two-fold.
On one side, it induces heart muscle cells to proliferate and survive in the injured heart, and on the other side, it induces an alteration of the fibrosis (although further studies are needed to see exactly how this works).
“Once we reproduced a severe stage of injury in the mouse heart, we inhibited the Hippo pathway.”
And after just six weeks the team observed that the injured hearts had recovered their pumping function to the level of the control, healthy hearts, according to Leach.
Heart failure is a long-term condition that tends to get gradually worse over time. It can’t usually be cured, but the symptoms can often be controlled for many years, according to the NHS.