In what may eventually hold great significance for patients who have suffered myocardial damage as a result of a heart attack, a study has shown that cells in a human heart can develop into adulthood and their age is, on average, six years younger than the individual.
Scientists from the Lawrence Livermore National Laboratory, the Karolinska Institute, Universite Claude Bernard Lyon, Lund University, and Lund University Hospital made these findings by using the amount of carbon 14 in the atmosphere from above-ground nuclear testing in the 1950s and 1960.
Lead researcher Bruce Buchholz, however, point out that as humans age, the percentage of new heart cells decreases markedly.
By age 25, renewal of heart cells gradually decrease from 1 percent turning over annually to .45 percent by the age of 75. About 50 percent of the heart cells a human is born with will regenerate during a lifetime.
Buchholz used the Laboratory's Center for Accelerator Mass Spectrometry to measure the amount of carbon 14 in DNA to establish the age of cardiac muscle cells in humans.
The researcher revealed that the study group determined the ages of heart cells by determining the time at which the sample''s carbon 14 concentration corresponded to the atmospheric concentration.
Buchholz and colleagues found that people born around or after the nuclear bomb tests corresponded to atmospheric concentrations several years after the subjects'' birth, indicating substantial postnatal DNA syntheses.
“By analysing individuals born at different times before 1955, it is possible to establish the age up to which DNA synthesis occurs, or whether it continues beyond that age,” the researcher said.
In the study, carbon 14 concentrations were elevated in subjects compared to those people born up to 22 years before the beginning of nuclear bomb tests.
“DNA of myocardial cells is synthesized many years after birth, indicating that cells in the human heart do, in fact, renew into adulthood,” Buchholz said.
“At the age of 50, 55 percent of the heart's cells remain from the time around birth and 45 percent have been generated later,” the researcher added.
While the limited recovery in humans after a heart injury or attack indicates failing regeneration of heart cells, the researchers say that the renewal of heart cells, as indicated by the mixing of carbon 14 in the DNA, suggest that the development of pharmacological strategies to stimulate this process may be a rational alternative or complement to cell transplantation strategies for heart cell replacement.