A collaboration between Lawrence Livermore National Laboratory, Karolinska Institute, Université Claude Bernard Lyon, Lund University and Lund University Hospital, analyzed heart biopsies for Carbon-14 content of people born before, during and after the period of above ground testing of nuclear weapons. By using temporal analysis of historical content of 14C in relation to what was in the DNA of cardiac tissue, the researchers discovered that people regenerate heart cells naturally, but the rate slows down over time. Between ages 25 and 75, the average annual regeneration rate goes from one to just under half of one percent.
From Lawrence Livermore NL:
Carbon 14 atmospheric concentration levels remained relatively stable until the Cold War, when above-ground nuclear bomb tests caused a sharp increase, or peak, which decreased slowly after the end of above-ground testing in 1963. This spike in carbon 14 in the atmosphere serves as a chronometer of the past 55 years.
Because DNA is stable after a cell has gone through its last cell division, the concentration of carbon 14 in DNA serves as a date mark for when a cell was born and can be used to date cells in humans.
The team determined the ages of heart cells by determining the time at which the sample’s carbon 14 concentration corresponded to the atmospheric concentration. Buchholz [Lawrence Livermore National Laboratory scientist] 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 analyzing 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,” Buchholz 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.”
Cardiac muscles have a striated appearance and their contraction in the heart propels blood from the atria and ventricles to the blood vessels of the circulatory system.
The limited recovery in humans after a heart injury, such as a heart attack, demonstrates failing regeneration of heart cells. But the team concluded 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.
Abstract in Science…
Read more: Healing heart attack victims, one cell at a time …
From the press release:
A team of Caltech scientists managed to create specialized DNA “seeds” that can activate a mixture of DNA to combine into a preprogrammed pattern. This ability to create self assembling DNA structures, known as algorithmic crystals, that can be coded for in advance, may lead to all sorts of scientific and clinical uses.
