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Researchers shed light on role of human cardiac stem cells in organ aging
Kajstura J. Circ Res. 2010;107:1374-1386.
Porrello E. Circ Res. 2010;107:1292-1294.
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Myocardial aging in men and women may be associated with time-dependent increase of human cardiac stem cells and cardiomyocytes, new study data suggest.
In the study, researchers measured the interaction of myocyte replacement, cellular senescence, growth inhibition and apoptosis in human hearts of normal women (n=32) and men (n=42) who died from causes other than CVD between the ages of 19 and 104 years.
The researchers found that a progressive loss of telomeric DNA in human cardiac stem cells occurs with aging. “Although the pool of functionally competent [human cardiac stem cells] expands with time and generates a larger myocyte progeny, the newly formed cardiomyocytes inherit short telomeres and rapidly reach the senescent cell phenotype,” they wrote.
Also revealed in their findings was the larger pool of functionally competent human cardiac stem cells and younger myocytes present in the female heart when compared with the male myocardium, with the replicative potential being higher and telomeres longer in female human cardiac stem cells. Specifically, myocyte turnover was found to occur at an annual rate of 10% at 20 years of age, 14% at 60 years and 40% at 100 years in the female heart, whereas those same ages corresponded with a myocyte turnover of 7%, 12% and 32%, respectively, in men.
For the researchers, this documented that cardiomyogenesis involves a large and progressively increasing number of parenchymal cells with aging, and from 20 to 100 years of age, the myocyte compartment is replaced 15 times in women and 11 times in men.
Enzo R. Porrello, PhD, and Eric N. Olson, PhD, with the department of molecular biology, University of Texas Southwestern Medical Center, Dallas, wrote in an article accompanying the study that the findings will provoke interest and prompt reconsideration of the biological processes that contribute to cardiac senescence.
“Although the present study by Kajstura et al is unlikely to completely resolve ongoing debates regarding the degree of myocyte repopulation in the human heart, this study provides some fascinating clues that point toward a previously unrecognized role for cardiac stem cells in the aging process,” they said.
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