Characterization of DNA methylation clock algorithms applied to diverse tissue types

Area of Science:

• Epigenetics
• Aging Research
• Genomics

Background:

• DNA methylation (DNAm) is used in epigenetic clocks to predict age.
• Existing clocks often use blood DNAm, limiting their use in other tissues.

Purpose of the Study:

• To assess epigenetic clock performance across diverse human tissue types.
• To determine if tissue-specific epigenetic clocks are necessary.

Main Methods:

• DNAm data from 973 deceased donors across 9 tissue types (lung, colon, prostate, ovary, breast, kidney, testis, skeletal muscle, blood) were analyzed.
• Eight epigenetic clocks were applied to estimate DNAm age.
• Clock estimates were analyzed for distributions, correlation with chronological age, and inter-tissue correlations.

Main Results:

• DNAm age estimates varied significantly across tissue types and between clocks within tissues.
• Correlation with chronological age differed by tissue, with blood often showing the strongest association.
• Smoking showed a positive association with epigenetic age in lung tissue.

Conclusions:

• Epigenetic aging differs across tissue types, impacting DNAm clock accuracy.
• Tissue-specific epigenetic clocks are required to improve predictive performance in non-blood tissues.