Biological clocks may be turned back: image via evif.netSteve Horvath, a professor of human genetics and biostatistics at University of California, Los Angeles (UCLA), has invented a new biological clock that accurately keeps time of nearly all tissues in the human body and how fast they age. His clock, reported in the October 21, 2013 online issue of Genome Biology, helps us understand not only how we age, but how our biological clocks can be turned back.
Horvath's biological clock is based on the rate of methylation, a natural chemical process that modifies our DNA. He studied 121 sets of data collected by other scientists who had previously studied methylation in healthy and cancerous human tissue. With 8000 samples of 51 types of tissue at hand, Horvath focused on 353 markers that change with age, and he charted the methylation of DNA from birth to 101 years of age.
Horvath was himself surprised that after repeatedly testing his new biological clock, it kept matching the chronological age of the tissue. There were exceptions, though, particularly in women's breast tissue, which apparently ages 36 years faster than other tissues in a woman's body. This may explain why breast cancer is the most common cancer in women.
Another finding of this study is that our biological clocks tick faster when we are young; at chronological age 20, they start to slow down.
The most hopeful news that came out of this study is that when adult stem cells were reprogrammed to embryonic-like stem cells, their clocks turned back completely. In principle, this means that pluripotent cells can rewind the body's clock back to zero.
Further studies will focus on which molecular or biochemical functions make the 'Horvath clock" possible and whether stopping the clock stops the aging process. Horvath will also investigate if his clock works on mice.
Sources: RD Mag, Explore Stem Cells