The zebrafish is capable of regenerating at least 20 percent of its own heart after it has been surgically removed, Harvard researchers report in tomorrow's issue of Science.
"The discovery is that zebrafish hearts regenerate," explains study co-author Dr. Mark Keating, an investigator with the Howard Hughes Institute of the Harvard Medical School and Children's Hospital in Boston. "It's never been shown that any vertebrate can regenerate heart muscle, and we found that zebrafish do it with little or no scarring."
What's exciting about this research, adds Didier Stainier, an associate professor in the department of Biochemistry and Biophysics at the University of California, San Francisco, is learning "that heart regeneration can happen at all."
Keating and his colleagues knew that zebrafish could regenerate their spinal cords, retinas and fins and wanted to see if they were capable of regenerating their heart muscle as well. So, they surgically removed 20 percent of the heart from 1- to 2-year-old adult zebrafish. Initially, it appeared as if the area was going to scar, but between nine and 30 days after the surgery, new cardiac cells began to grow. By the 30th day, the researchers report a contiguous wall of muscle had formed in the surgically altered hearts. By day 60, the hearts had grown back to normal, with little to no scarring, and were functioning normally as well.
If such damage were to occur in humans, scars would form, rather than new heart muscle, Keating says.
Next, the researchers tested zebrafish with a dysfunctional gene known to stop fin regeneration. One of the functions of this gene is to let cells divide and proliferate. In these zebrafish, regeneration of the heart did not occur, Keating says.
Keating notes these experiments support the idea that there is competition between regeneration and scarring. "If we can enhance heart cell proliferation, maybe we can overcome scarring [in humans]," he adds.
"If we're talking about regenerating organs or creating them from scratch, we need to understand the mechanisms at work in the zebrafish," Stainier says. "This study puts us closer, but we're nowhere near gene therapy that would regenerate the heart. That's still many steps away."
One area the authors would like to investigate further, Keating says, is whether the zebrafish heart can regenerate after it has an injury similar to a human heart attack.
What To Do
Because any therapy that might eventually come from this research is many years away, keep your heart healthy now with these tips on preventing heart disease from the U.S. Centers for Disease Control and Prevention and Louisiana State University.