In the history of science there frequently is a scientist who has an idea that nearly all other scientists think is nonsense. It takes time and a lot of research usually for enough evidence to be pile up to convince the world that the creative scientist is correct. And now we have research results that show an idea put forth in 1987 by Dr. Piero Anversa, now of the Harvard Medical School , was absolutely correct. He asserted that new heart cells replace old ones. In other words, that hearts regenerate themselves.
Dr. Anversa said that heart muscle cells are renewed so fast that a person dying at age 80 has replaced the heart four times over. If correct, that is absolutely amazing, when conventional wisdom was that you die with the same heart cells that you were born with.
On the other hand, consider that a zebrafish can regenerate large regions of its heart after injury. What if a similar response could be induced in people?
Think for a minute. With this new understanding comes the potential for people who have had heart attacks, like me, who have had some heart muscle die from lack of blood flow and oxygen, now to have some hope that new tissue can renew their hearts. There is an incredible opportunity for researchers to seek drugs or other means that could accelerate human heart cell replacement.
The latest research actually confirmed Anyersa's idea qualitatively but not quantitatively. Swedish scientists worked very hard to measure the amount of carbon-14 in heart cells, actually the DNA in cells. That amount is used to measure the cell's birth date because the level of carbon-14 in the atmosphere falls each year. So, it becomes possible to figure out the percent of cells that have changed over time in a particular heart.
A team of researchers led by Dr. Jonas Frisen of the Karolinska Institute in Stockholm found that about 1 percent of the heart muscle cells are replaced every year at age 25, but that the rate gradually falls to less than half a percent per year by age 75. This means that about half of the heart's muscle cells are exchanged in the course of a normal lifetime. All told, we've renewed about 40 percent of our heart cells by age 70, Frisen said.
Interestingly, Dr. Loren Field, a heart expert at the Indiana University School of Medicine, has found that heart muscle cells regenerated in mice at the same rate that Dr. Frisen found in people.
Actually back in 2001 other researchers under the direction of Anyersa at New York Medical College published research results that also strongly indicated heart cell regeneration. They examined heart muscle cells taken from patients four to 12 days after they had suffered a heart attack, sampling both the zone near the site of the heart attack and parts farther away from the damaged muscle tissue. To determine whether the heart was healing or not, the team looked for a protein known as Ki67, which is expressed in the nuclei of cells during division. They found that cells from the heart attack border zone multiplied 70 times faster than those in a normal heart; and that cells farther away from the diseased zone multiplied 24 times faster than normal. But these findings did not get the attention that the new Swedish results have attracted in the scientific community.
Back then Anyersa said: "If we can prove the existence of cardiac stem cells and make these cells migrate to the region of tissue damage. We could conceivably improve the repair of damaged heart muscle and reduce heart failure."
But these latest results show much less new heart tissue over a lifetime than Anversa predicted. More importantly, however, is that the basic notion of heart renewal has been strongly confirmed and widely accepted, opening up a new wide door for research into making damaged hearts rehabilitate themselves fast enough to reduce dependency on drugs, pacemakers and implanted defibrillators, as well as greater chances of longer lives. One possibility is the transplantation of cells into hearts to foster new muscle growth, just like Anyersa envisioned.
Indeed, there is more good news just reported. In another corner of the big world of science research at University of Texas Southwestern Medical Center new findings in mice suggest that introducing the protein molecule TB4 systemically after a heart attack encourages new growth and repair of heart cells. Researchers there say the clinical implications of this are enormous because of the potential to reverse damage inflicted on heart cells after a heart attack." The thinking was that introduction of TB4 might activate new vessel growth in the adult heart. In the mouse study researchers found that the molecule encourages cardiac regeneration by inhibiting death in heart cells after an injury such as a heart attack and by stimulating new blood vessel growth. "We observed that by injecting this protein systemically, there was increased cardiac function after a heart attack," said Dr. Ildiko Bock-Marquette.
Considering all these results, healing broken hearts now has a lot more than poetic and spiritual meaning. Of course, people who get heart attacks and suffer some heart damage when they are relatively young have more time to undergo natural heart healing, with or without some help from newly developed drugs or cells.