Until yesterday. That's when a group of scientists from the University of California, Los Angeles announced in the journal Genome Biology finding a way of reading a cell's age. It has to do with molecules that accumulate on the cell's DNA.
Steve Horvath, who led the study, started out with 8,000 samples from 51 tissues aged from pre-birth to 101. In the end, he found a group of 353 molecular tags on the DNA that correlate with the age of the cell. Essentially, a scientist can look at which of those 353 molecules are present or absent from a cell's DNA and know the age of the individual that cell came from.
In a press release from UCLA, Horvath said:
"To fight aging, we first need an objective way of measuring it. Pinpointing a set of biomarkers that keeps time throughout the body has been a four-year challenge."To be clear, what they found is a way of measuring a cells age, not manipulating it's age. As a story in Forbes does an excellent job of explaining, discovering the clock doesn't mean scientists know how to wind it backword--at least not in you and me.
One interesting point Horvath and his team discovered (and something that brings us back to what's near and dear to our hearts at CIRM), is that the process of converting a mature cell into a reprogrammed stem cell resets that clock. So, our groups of scientists working to develop therapies based on reprogrammed iPS cells are working with cells that, as far as their clocks are concerned, were reborn.
We have a list on our website showing all of our projects working with these freshly reborn iPS cells.