August 7, 2001
Some laboratory mice have displayed an astonishing ability to regenerate damaged heart tissue, scientists said yesterday. The finding could open a new avenue for treating heart disease and other illnesses and injuries in people.
Researchers at the Wistar Institute in Philadelphia found that mice of a type first bred several decades ago and used to study autoimmune diseases were able to regrow healthy heart tissue with little scarring after serious heart damage.
Dr. Ellen Heber-Katz, who led the study, said the exact mechanism at work was not known. But she said the mice appeared somehow to have retarded the formation of scar tissue, growing healthy tissue instead. The study is being published in The Proceedings of the National Academy of Sciences.
Dr. Heber-Katz said the findings suggested that all mammals, including humans, might possess this regenerative capability and that methods could be developed to tap it.
Scientists knew that some amphibians and reptiles could regenerate heart tissue, limbs, the spinal cord and the retina, but they had never seen this ability in mammals.
Dr. Heber-Katz and her colleagues noticed in 1998 that larger-than-usual laboratory mice known as MRL mice were able to heal small holes in their ears without scarring. They traced this trait to multiple genes on five chromosomes.
Mammals, including people, form scar tissue after cardiac damage like that caused by a heart attack. This scarring permanently impairs heart function. But certain amphibians can regrow heart tissue after injury. Dr. Heber-Katz's team decided to explore whether their mice could regenerate heart tissue.
The researchers damaged the right ventricle of the mice's hearts. But instead of forming scar tissue, the mice generated new cells that were indistinguishable from neighboring healthy heart cells.
In normal mice, only 1 percent to 3 percent of the heart cells near the injury could divide. In the MRL mice, up to 20 percent of the heart cells divided in response to injury.
Dr. Heber-Katz said that the mice had an unusual ability to grow tissue that normally does not grow back in mammals. "We have dividing cells replacing damaged tissue in the heart so it looks normal," she said. "It appears to function normally. That's amazing."
Regeneration of heart tissue in the special mice took place without the use of drugs, transplanted cells or tissues like stem cells or any other intervention. Many scientists are working on ways to use stem cells — primitive cells that can transform into other cell types — to regenerate tissue and organs damaged by disease or injury.
The researchers are trying to nail down the specific genetic and molecular differences between the MRL mice and other strains. Such differences could lead to the identification of drug compounds for improved healing in heart disease, as well as other types of ailments and injuries, the researchers said.
Dr. Heber-Katz said the mice appeared
to mobilize an enzyme to break down the scar immediately and prevent the
buildup of extensive scar tissue. She said that if scientists could discover
how to prevent the immediate formation of scar tissue, the human heart
might be able to regenerate healthy tissue as well.
Copyright 2001 The New York Times
Copyright 2001 The New York Times Company