Highlights

  • A new technique allows scientists to measure the biological age of different types of cells, such as liver and brain cells.
  • Measuring biological age with this new technique may help uncover which type of cells age fastest and contribute to age-related diseases like Alzheimer’s and fatty liver disease.
  • The new technique may also be used in future research to determine in which cell types and tissues rejuvenation interventions work best.

Epigenetic clocks that assess biological age, based on DNA methylation patterns of blood cells, have been around since Altos Labs’ Steve Horvath first developed them in 2013. These clocks have been used to predict risks for age-related diseases and life expectancy. As epigenetic clock precision advances, researchers have developed a new way to use them to assess the age of specific cell types, offering a new way to evaluate the age of tissues.

As published in Aging, Teschendorff and colleagues from the Chinese Academy of Sciences in China unveil a new way to assess biological age in individual cell types. This new technique has given insight into what cell types age fastest and drive age-related conditions like Alzheimer’s and liver disease. As such, brain cells called glia age fastest in patients with Alzheimer’s, suggesting these cells play critical roles in neurodegeneration. Furthermore, in liver diseases, such as fatty liver disease, an aging assessment for liver cells showed accelerated aging, suggesting this clock may work better to uncover liver problems than previous methods. Future research using this technique may lead to more precise health assessments and identifications of cell targets for aging intervention therapies.

Standard methods that measure biological age rely on analyzing the bulk of cell types from a given tissue, such as blood. This can make high-precision age estimates difficult since some cell types increase and others decrease in abundance throughout all tissues with age. Moreover, analyzing the bulk of cell types at once in a given tissue with current methods makes it nearly impossible to understand aging processes in specific cell types and how each contributes to aging.

Certain Cell Types Age Faster in Age-Related Diseases

Using their new cell-type resolution epigenetic clock, Teschendorff and colleagues assessed DNA samples from human brain cells. Based on an advanced computer model, their technique measured changes in DNA methylation in samples from healthy individuals and those with Alzheimer’s. The overarching goal of this technique was to understand how aging in specific cell types may contribute to Alzheimer’s disease.

Interestingly, the China-based researchers found that certain brain cells—specifically, glia—age faster in people with Alzheimer’s. This finding suggests that the aging of certain cell types plays a critical role in neurodegeneration.

Similarly, Teschendorff and colleagues analyzed DNA samples from liver cells of healthy individuals and those with liver diseases like fatty liver disease and obesity. The clock for liver cells showed accelerated aging for patients with liver diseases, suggesting that the new technique may serve as a more precise tool for detecting liver dysfunction.

“The construction of such cell-type specific clocks will be critical to advance our understanding of biological aging at cell-type resolution and for evaluating in which cell-types cellular rejuvenation interventions work best,” say Teschendorff and colleagues in their publication.

Developing Cell-Type Resolution Aging Clocks Spearheads Aging Research Precision

Limitations to the study include that epigenetic clock analysis on specific cell types other than blood cells requires a biopsy. Even so, isolating brain cells from living humans with a brain biopsy can cost from $8,000 to $50,000. What’s more, for someone wanting to get a liver biopsy to find whether they have accelerated liver cell aging, such a procedure would cost from $1,500 to $300,000. Accordingly, such high costs make regular epigenetic clock analysis of cell types like brain and liver cells virtually impossible.

Along these lines, the cell type resolution of epigenetic clocks is likely inaccessible for most aging adults seeking to discover whether certain organs show accelerated aging. On the other hand, the new technique may be applied to projects that use cadavers or expensive biopsies, which seek to find whether aging intervention therapies are effective.

Altogether, research on this new cell-type resolution-based aging clock highlights the critical need for more precision in aging research. Since certain cell types fluctuate in abundance during aging, measuring aging in specific cell types can give a more accurate assessment of which cells contribute to aging. Moreover, since certain types of cells may age faster in age-related diseases, measuring aging with a cell-type resolution may help uncover how such diseases unfold. Future aging research using cell-type resolution may also help pinpoint what compounds target specific cells to delay, prevent, and/or alleviate certain age-related diseases.