TOPICS > Health

After Heart Attack, Turning Scar Tissue Back Into Beating Heart Cells

April 18, 2012 at 12:00 AM EDT
A study published Wednesday in the journal Nature revealed that scientists have managed to convert damaged tissue into functioning heart muscle by inducing mild heart attacks on lab mice then coaxing their hearts into rebuilding themselves. In collaboration with KQED's QUEST program, correspondent Spencer Michels reports.

GWEN IFILL: Next, a development that could be good news for millions of heart attack victims. Scientists announced they have managed to convert damaged tissue into functioning heart muscle.

The research appeared today in the science journal Nature.

NewsHour correspondent Spencer Michels has our story, produced in collaboration with KQED San Francisco’s QUEST program.

And a note: Some of the pictures of the medical procedures are graphic.

SPENCER MICHELS: In hospitals all over the country, doctors try to keep alive the more than five million Americans with damaged hearts, a result of heart attacks. Damage means their hearts can no longer beat at full capacity.

When the heart muscle cells are deprived of oxygen during an attack, scar tissue forms in the heart, tissue that doesn’t beat like other heart cells do. Now, in what they consider a dramatic development, scientists at the Gladstone Institutes in San Francisco have figured out a way to transform scar-forming cardiac cells into beating heart muscle in mice, and hope they can replicate the feat in humans.

Deepak Srivastava directs cardiovascular and stem cell research at Gladstone, an independent biomedical research institution. He led the team that published results in Nature and explained the challenge and what he called the breakthrough.

DR. DEEPAK SRIVASTAVA, Gladstone Institutes: From the moment an embryo is three weeks old until the day an organism dies, the heart never takes a break.

The heart cell is unique in that it incorporates some features of brain cells, and some features of muscle cells all together. It’s actually an amazing thing to see cells in a dish that just without any stimulus just start contracting. And it’s that property that allows the cells in unison to generate force and pump blood through the body.

SPENCER MICHELS: Though doctors can save most patients’ lives after a heart attack, they can’t always preserve all of their heart function.

DR. DEEPAK SRIVASTAVA: An individual may have trouble walking up a flight of stairs. They may have to stop several times trying to walk across the street to get to work.

There are a variety of approaches we use right now to help people who are left with damaged hearts. But none of them actually get to the root of the problem, which is replacing that damaged heart muscle. And that’s where our focus has been at Gladstone.

And you have enough for how many mice today?

WOMAN: So I have enough for like three mice.

SPENCER MICHELS: Researchers here have discovered a way to coax mouse hearts into rebuilding themselves. In their experiments, they first give lab mice a mild heart attack.

DR. DEEPAK SRIVASTAVA: We do a more limited type of heart attack that doesn’t result in too many symptoms in the mice and doesn’t cause death. So we first anesthetize the mice, so they don’t feel any of the pain.

It’s almost out.

There are billions of muscle cells in the heart that are important for the squeeze of the heart. But there’s an equal number of cells that are really there to support the muscle cells, and sort of form the architecture of the organ.

The support cells are the ones that actually make the scar after a heart attack, and the breakthrough we have made is that we have found a way to genetically engineer these cells to make new muscle, instead of scar.

SPENCER MICHELS: First, the researcher mimics a heart attack by cutting off blood to parts of the heart. Then, she injects three genes that will transform the scar cells into beating heart muscle cells.

DR. DEEPAK SRIVASTAVA: Three months after the injury, what we find is quite remarkable. Using ultrasounds on these animals, what we see is that the heart’s function is greatly restored.

The ultrasound provides us an image of the walls of the heart and the valves in the heart, and shows how it squeezes and relaxes with each heartbeat. It’s very close to normal in the amount of blood it’s able to pump out to the rest of the body. There’s still some scar. We can see that, but embedded within the scar tissue is new muscle.

SPENCER MICHELS: This new research has impressed Yerem Yeghiazarians, director of the Translational Cardiac Stem Cell Program at the University of California, San Francisco, though he had some questions.

DR. YEREM YEGHIAZARIANS, University of California, San Francisco: So what we need to know is if we can do the same thing using non-retroviral techniques with small molecules, if we can replicate the experiments in larger animal models and eventually do this safely in humans, because if we can do that, that could potentially revolutionize the way we treat our patients with weakened hearts either after a heart attack or other causes for cardiac failure.

It is the first time that anybody has described this as a novel way of treating damaged hearts, because up to this point, there are no medications and no devices that replace a scar in the heart with beating functional heart muscle cells.

SPENCER MICHELS: Srivastava admits there is a long road ahead before the procedure can save human lives.

DR. DEEPAK SRIVASTAVA: We have to make sure that it’s scalable to the size of a human heart where, where instead of thousands of cells that we might need to regenerate in the mouse, we may need millions in the human heart.

The second thing that we have to do is to make sure that this will be a safe approach. And for that, we will likely use a larger animal model that’s closer to human, such as a pig. And then the final thing that we really have to work out is, what is the best way to deliver the reprogramming genes into the cells of the heart.

SPENCER MICHELS: Srivastava estimates it will be six or seven years before treatments might be available for humans.

GWEN IFILL: On our website, we have more reporting on the science behind the genetic technique researchers are using to repair hearts. That’s in a blog post from our colleagues at KQED QUEST on the NewsHour home page.