In a finding that may open new approaches to treating heart disease, Swedish scientists have succeeded in measuring a highly controversial property of the human heart: the rate at which its muscle cells are renewed during a person’s lifetime.
The finding overturns what has long been conventional wisdom: that the heart cannot produce new muscle cells and so people die with the same heart they were born with.
About 1 percent of heart muscle cells are replaced every year at age 25, and that rate gradually falls to less than half a percent per year by age 75, a team of researchers led by Jonas Frisen of the Karolinska Institute in Stockholm concluded.
The upshot is that about half of the heart’s muscle cells are exchanged in the course of a normal lifetime, the Swedish group calculates. Its results were to be published on Friday in the journal Science.
“I think this will be one of the most important papers in cardiovascular medicine in years,” said Charles Murry, a heart researcher at the University of Washington in Seattle. “It helps settle a longstanding controversy about whether the human heart has any ability to regenerate itself.”
If the heart can generate new muscle cells, researchers can hope to develop drugs that might accelerate the process, since the heart fails to replace cells that are killed in a heart attack.
The dogma that the heart cannot generate new muscle cells has been challenged since 1987 by a somewhat lonely skeptic, Piero Anversa, now of the Harvard Medical School. Anversa maintains that heart muscle cells are renewed so fast that a person dying at age 80 has replaced the heart four times over. Many other researchers have doubted this assertion.
Cell turnover rates can easily be measured in animals by making their cells radioactive and seeing how fast they are replaced. Such an experiment, called pulse-labeling, could not ethically be done in people.
But Frisen realized several years ago that nuclear weapons tested in the atmosphere until 1963 had in fact labeled the cells of the entire world’s population.
The nuclear blasts generated a radioactive form of carbon, known as carbon-14. The amount of carbon-14 in the atmosphere has gradually diminished since 1963, when above-ground tests were banned, because it has been incorporated into plants and animals or diffused into the oceans.
In the body, carbon-14 in the diet gets into the DNA of new cells and stays unchanged for the life of the cell.
Because the level of carbon-14 in the atmosphere falls each year, the amount of carbon-14 in the DNA can serve to indicate the cell’s birthdate, Frisen found.
Four years ago he used his new method to assess the turnover rate of various tissues in the body, concluding that the average age of the cells in an adult’s body might be as young as seven to 10 years. But there is a wide range of ages — from the rapidly replaced cells of the blood and gut to the mostly permanent cells of the brain.
Frisen has successfully applied his method to the heart muscle cells, but had to navigate a series of technical obstacles created by the special behavior of the cells. Many have two nuclei, instead of the usual one, and within these double nuclei the DNA may be duplicated again.
“I was really impressed at the level of rigor they put into this analysis,” Murry said, calling it a “scientific tour de force.”
The finding that heart muscle cells do regenerate, though at a considerably slower rate than Anversa predicted, is a “reasonable conclusion to a hotly contested issue,” Murry said.
“Anversa went out on a limb, and I think he was partly right,” he said.
Loren Field, a heart expert at the Indiana University School of Medicine, said he had found that heart muscle cells regenerated in mice at the same rate that Frisen had found in people.
Despite the controversy created by Anversa’s claims, there has long been agreement that there is a low but detectable rate of cell renewal in the heart, Field said.
The goal now, in his view, is “to try to tickle the system to enhance it.”
Anversa, for his part, said he was “ecstatic” at Frisen’s confirmation of his view that the heart could generate new muscle cells, but suggested that the new measurements might have underestimated the rate at which new cells are formed.
Since heart muscle cells contract 70 times a minute, they seem likely to need renewing more often than Frisen’s measurements suggest, he said.
“Now let’s discuss the magnitude of the process, and that will let us think about how we can apply this concept to heart failure,” Anversa said.
Frisen said he did not agree that the rate of regeneration had been underestimated. He said it would now be worth trying to understand how the regeneration of heart muscle cells was regulated.
A zebrafish, for instance, can regenerate large regions of its heart after injury, and possibly a similar response could be induced in people.
It could also be that the heart does generate many new muscle cells after a heart attack but that the cells fail to establish themselves.
Drugs that kept any such new cells alive could be helpful, Frisen said.
Saudi Arabian largesse is flooding Egypt’s cultural scene, but the reception is mixed. Some welcome new “cooperation” between two regional powerhouses, while others fear a hostile takeover by Riyadh. In Cairo, historically the cultural capital of the Arab world, Egyptian Minister of Culture Nevine al-Kilany recently hosted Saudi Arabian General Entertainment Authority chairman Turki al-Sheikh. The deep-pocketed al-Sheikh has emerged as a Medici-like patron for Egypt’s cultural elite, courted by Cairo’s top talent to produce a slew of forthcoming films. A new three-way agreement between al-Sheikh, Kilany and United Media Services — a multi-media conglomerate linked to state intelligence that owns much of
The US and other countries should take concrete steps to confront the threats from Beijing to avoid war, US Representative Mario Diaz-Balart said in an interview with Voice of America on March 13. The US should use “every diplomatic economic tool at our disposal to treat China as what it is... to avoid war,” Diaz-Balart said. Giving an example of what the US could do, he said that it has to be more aggressive in its military sales to Taiwan. Actions by cross-party US lawmakers in the past few years such as meeting with Taiwanese officials in Washington and Taipei, and
The Republic of China (ROC) on Taiwan has no official diplomatic allies in the EU. With the exception of the Vatican, it has no official allies in Europe at all. This does not prevent the ROC — Taiwan — from having close relations with EU member states and other European countries. The exact nature of the relationship does bear revisiting, if only to clarify what is a very complicated and sensitive idea, the details of which leave considerable room for misunderstanding, misrepresentation and disagreement. Only this week, President Tsai Ing-wen (蔡英文) received members of the European Parliament’s Delegation for Relations
Denmark’s “one China” policy more and more resembles Beijing’s “one China” principle. At least, this is how things appear. In recent interactions with the Danish state, such as applying for residency permits, a Taiwanese’s nationality would be listed as “China.” That designation occurs for a Taiwanese student coming to Denmark or a Danish citizen arriving in Denmark with, for example, their Taiwanese partner. Details of this were published on Sunday in an article in the Danish daily Berlingske written by Alexander Sjoberg and Tobias Reinwald. The pretext for this new practice is that Denmark does not recognize Taiwan as a state under