Using thousands of tissue samples from open access datasets, Steven Horvath, PhD, has created a calculator that predicts the age of tissue using chemical changes to DNA. Research published in the open access journal Genome Biology explains how the calculator works.
Horvath, a professor of human genetics and biostatistics at UCLA, used data from 7,844 samples in 82 publicly available datasets to create a calculator which predicts the age of healthy tissue using information about changes in DNA methylation. Traditionally, changes to telomeres, the bits of genetic code at the end of chromosomes, are used to tell the age of tissues. Horvath shows that DNA methylation is a much more accurate measure.
DNA methylation is a chemical change that is made to DNA throughout life. Previous studies have shown that as people get older, certain changes to the methylation of DNA accumulate. This article demonstrates that, in almost all healthy tissues and cell types, the accumulation happens at a predictable rate and explains how the DNA methylation data and the actual age of tissues in 39 datasets can be used to work out that rate and create a calculator.
Some tissue types were shown to buck this trend, however. Breast tissue appeared older than expected, while heart tissue appeared younger. Analysis of an additional 5,826 cancer tissue samples showed that certain types of brain, breast, and colorectal cancers had an accelerated rate of DNA aging, giving hints about how cancer affects tissue and suggesting new methods to diagnose certain cancer types. Read the article.