In adulthood, our hearts generally can’t grow again in response to injury. Emory cardiology researchers Ahsan Husain and Nawazish Naqvi and their colleagues have been chipping away at this biological edifice in animal models, demonstrating that it is possible to remove constraints that prevent the heart from growing new muscle cells.
Husain and Naqvi’s teams accomplished this by combining the thyroid hormone T3 — already FDA approved — with siRNA-based inhibition of an enzyme called DUSP5. Their latest paper, published in the journal Theranostics, applies the combination in an animal model of drug-induced heart failure.
The anticancer drug doxorubicin is notorious for its cardiotoxicity, yet it is a mainstay of treatment for breast cancer in adults and several types of cancer in children. Cardiotoxicity affects a fraction of breast cancer patients treated with doxorubicin (20 percent in some studies) and severely impacts mortality and quality of life.
In the mouse model, doxorubicin generates severe heart failure, with a 40 percent drop in left ventricular ejection fraction (LVEF), a measure of the heart’s pumping capacity. In response to the combination of T3 and DUSP5 siRNA, a large increase in LVEF is seen. The researchers also report that the treatment has a marked effect on the health of the animals, restoring their activity levels, grooming and posture. See the video for an example of a mouse heart treated with the T3/DUSP5 siRNA combination.
The results are potentially applicable to other situations when doctors would want to regrow or repair cardiac muscle. Husain reports plans for a clinical study in patients with drug-induced or other forms of heart failure, supported by a generous gift from the Atlanta-based ten Broeke Family Foundation.
After a heart attack, cardiac muscle cells die because they are deprived of blood and oxygen. In an adult human, those cells represent a dead end. They can’t change their minds about what kind of cell they’ve become.
In newborn babies, as well as in adult fish, the heart can regenerate after injury. Why can’t the human heart be more fishy? At Emory, researcher Jinhu Wang is seeking answers, which could guide the development of regenerative therapies.
“If we want to understand cardiac regeneration in mammals, we can look at it from the viewpoint of the fish,” he says.
A lot of research in regenerative medicine focuses on the potential of stem cells, which have not committed to become one type of tissue, such as brain, skin or muscle. Wang stresses that the ability of zebrafish hearts to regenerate does not originate from stem cells. It comes from the regular tissues. The cells are induced to go back in time and multiply, although their capacity to regenerate may vary with the age of the animal, he says.
Jinhu Wang, PhD manages an impressive set of fish tanks
Zebrafish hearts are simpler than mammals’: theirs have just two chambers, while ours have four. Nobel Prize winner Christiane Nusslein-Vollhard has promoted the use of zebrafish as a genetic model in developmental biology. Its embryos are transparent, making it easy to spot abnormalities.
Wang’s fish room in the basement of Emory’s Rollins Research Center contains more than 1000 fish tanks, with different sizes of cage for various ages and an elaborate water recycling system. The adult fish eat brine shrimp that are stored in vats in one corner of the lab. Read more
It is a privilege to work at Emory and learn about and report on so much quality biomedical research. I started to make a top 10 for 2014 and had too many favorites. After divertingÂ some of these topics into the 2015 crystal ball,Â I corralledÂ them into themes.
The entire heart muscle in young children may hold untapped potential for regeneration, new research suggests.
For decades, scientists believed that after a child’s first few days of life, cardiac muscle cells did not divide. Instead, the assumption was that the heart could only grow by having the muscle cells become larger.
CracksÂ were alreadyÂ appearingÂ in that theory. But new findings in mice, published May 8 inÂ Cell, provide a dramatic counterexample — with implications for the treatment of congenital heart disorders in humans. Read more