X-Message-Number: 31660
Date: Fri, 01 May 2009 09:10:23 -0700
From: hkhenson <>
Subject: Heart renewal study

Healing Heart

Damage to the heart through aging or disease 
often leads to chronic heart failure due to loss 
and insufficient regeneration of heart muscle 
cells (cardiomyocytes). Absence of regeneration 
in the heart has been attributed to the inability 
of muscle cells to divide, coupled with the 
absence of a muscle-producing stem cell 
population. Now, a Report in the 3 Apr 2009 
Science provides strong evidence that some 
cardiomyocyte renewal can occur. To determine the 
ages of human heart cells, 


<http://www.info-aaas.org/util/link.jsp?e=6isk9LxiL1JpBWJFMOUpopJ6IAd6-tq_t1FUU17vmE4HHOEgqTGJr7zXQjL40YMRv&s=1Srd_3Epu&v=2aaBJFyfg9VGQ9w..A>Bergmann
et al. used a clever system based on radiocarbon 
dating of DNA. Nuclear bomb tests during the Cold 
War released high concentrations of carbon-14 
into the atmosphere until the tests were banned 
in 1963. Since atmospheric carbon is taken up by 
plant cells through photosynthesis and 
subsequently by human cells and their DNA 
(because humans eat plants and other animals that 
eat plants), the C-14 concentration in human 
cells formed in different years mirrors differing 
atmospheric C-14 levels. By comparing the age of 
cardiomyocyte DNA to the patient's chronological 
age, one can estimate the extent to which the 
cardiomyocyte population has turned over (senior 
author J. Frisen discussed the technique in a 
related 


<http://www.info-aaas.org/util/link.jsp?e=59NjMrf6iykdcnOKJtJ8yV1xfzHJOOFPQQl656_NBMK5aGS2MpNxLej1Qm8iMr593&s=1Srd_3Epu&v=2aaBJFyfg9VGQ9w..A>podcast
interview). Using this approach, the team found 
that cardiomyocytes do renew, albeit slowly, at a 
rate of 1% per year at age 25, declining to 0.45% 
at age 75. This means that fewer than 50% of 
heart muscle cells are exchanged during a normal 
life span. An accompanying 


<http://www.info-aaas.org/util/link.jsp?e=47YNycyl_p6XJlMxZ4G3rDzMe18Y1Yi1gTvSMG7hIJATAfMTk&s=1Srd_3Epu&v=2aaBJFyfg9VGQ9w..A>Perspective
by C. E. Murray and R. T. Lee noted that "even 
though cardiomyocyte turnover rate is low in the 
adult heart, the fact that is occurs at all 
suggests that it can potentially be therapeutically exploited."

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=31660