For decades, cardiac researcher James McCully, PhD, has been spellbound by the idea of using mitochondria, the “batteries” of the body’s cells, as a therapy to boost heart function. Finally, a clinical trial at Boston Children’s Hospital is bringing his vision — a therapy called mitochondrial transplantation — to life.
Mitochondria, small structures inside all of our cells, synthesize the essential energy that our cells need to function. In the field of cardiac surgery, a well-known condition called ischemia often damages mitochondria and its mitochondrial DNA inside the heart’s muscle cells, causing the heart to weaken and pump blood less efficiently. Ischemia, a condition of reduced or restricted blood flow, can be caused by congenital heart defects, coronary artery disease and cardiac arrest.
For the smallest and most vulnerable patients who are born with severe heart defects, a heart-lung bypass machine called extracorporeal membrane oxygenation (ECMO) can help restore blood flow and oxygenation to the heart. But even after blood flow has returned, the mitochondria and their DNA remain damaged.
“In the very young and the very old, especially, their hearts are not able to bounce back,” says McCully.
Ischemia can be fatal for the tiniest patients
After cardiac arrest, for instance, a child’s mortality rate jumps to above 40 percent because of ischemia’s effects on mitochondria. If a child’s heart is too weak to function without the support of ECMO, his or her risk of dying increases each additional day spent connected to the machine.
But what if healthy mitochondria could come to the rescue and replace the damaged ones? …
For a tissue graft to survive in the body — whether it’s a surgical graft or bioengineered tissue — it needs to be nourished by blood vessels, and these vessels must connect with the recipient’s circulation. While scientists know how to generate blood vessels for engineered tissue, efforts to get them to connect with the recipient’s vessels have mostly failed.
“Surgeons will tell you that when putting tissue in a new location in the body, the small blood vessels don’t connect at the new site,” says Juan Melero-Martin, PhD, a researcher in Cardiac Surgery in Boston Children’s Hospital. “If you want to engineer a tissue replacement, you’d better understand how the vessels get connected, because if the vessels go, the graft goes.”
Melero-Martin and colleagues have uncovered several strategies to help these connections form, as they describe online today in Nature Biomedical Engineering. The strategies could help improve the success of such procedures as heart patching, bone grafting, fat transplants and islet transplantation. …
Tertiary care centers such as the Boston Children’s Hospital Heart Center have led the way in groundbreaking surgical innovations for years, pushing boundaries and correcting ever more complex abnormalities.
But innovation is also making a difference when it comes to more “common” procedures.
“We’re always trying to make the less complex procedures shorter and less invasive,” says Sitaram Emani, MD, director of the Complex Biventricular Repair Program at the Heart Center. “Making surgery and recovery less painful and disruptive for all of our patients is a priority.”