When a child gets a heart transplant, what happens to the old one?
At Children's Hospital Colorado, old hearts are deposited (with the parent’s permission) into a bank of diseased heart tissue that researchers like Children's Colorado Transplant Cardiologist, Shelley Miyamoto, MD, have been gathering for more than 20 years.
This is because in an extreme deep freeze, the heart's cells can stay intact for a very long time allowing tests and research to be done long after the heart has been deposited. For example, even years later, lab technicians can slice heart tissues into strips just a few micrometers thick and test the effects of a possible drug for pediatric heart failure — something that, right now, doesn’t exist.
In fact, only one drug trial for heart failure in children has ever been conducted. "And the shocking thing about that trial," says Dr. Miyamoto, "was that this drug had been proven in multiple trials to be effective in adults, but in children it produced no improvement."
The difference in treating children's hearts
Children's hearts fail for many reasons, most of them congenital. It's an array of rare conditions few researchers study, but Dr. Miyamoto is one of the only researchers in the world who does. Working with University of Colorado School of Medicine adult cardiologist Brian Stauffer, MD, and molecular biologist Carmen Sucharov, PhD, Dr. Miyamoto uses lab techniques and clinical data to compare child and adult heart disease at the molecular level.
The differences are crucial: a heart drug called Milrinone, for example, is dangerous when used chronically in adults. Dr. Miyamoto's team recently proved it safe and effective in children even over a long period of time — a period, say, like the protracted, uncertain wait on the transplant list. The distinction could save lives.
"It hasn’t worked to extrapolate from the adult data," Dr. Miyamoto says. "There's been no improvement in transplant-free survival for kids in 30 years, and that's not okay."
Changing the game
Dr. Miyamoto's team was recently the first to describe the role of non-coding proteins called micro-RNAs as biomarkers of potential heart recovery: the relative presence of these proteins in diseased hearts predicts recovery an astonishing 66 to 88% of the time.
That power to predict could go a long way toward subverting the enormous burden of waiting for a transplant. "The pediatric field is lagging far behind the adult field," says Dr. Miyamoto. "But it's a start."
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