© 2005 Elsevier Inc.
The cells in our body are continually replaced, especially those exposed to the harsher environments of the skin or intestine. Even cells in tissues that generally experience less turnover often regenerate after an injury. While scientists believe other cells in the human body, such as those in the brain, have longer life spans, they still don't know much about how often cell replacement occurs, if at all.
Molecular proliferation markers can capture the number of cells in a cycle at any given time but still fail to elucidate the number of mature cells that are actually produced or end up contributing to the tissue, notes Kirsty Spalding of the Medical Nobel Institute in Sweden. And, such methods use modified nucleotides and retroviruses that are toxic and cannot be used for human studies.
Inspired by archaeologists' use of 14C dating, Spalding and colleagues from the Karolinska...