New Gene Expression Clocks Reveal Biological Aging Can Be Measured and Reversed
Researchers from Harvard and Mass General Brigham have developed a new biological clock based on gene expression, revealing that aging is not a uniform or irreversible process.
We are accustomed to measuring our age by the time that has elapsed since our birth, but could our body possess an internal clock that ticks at a completely different rate? A new study published in the journal Nature suggests just that. Researchers from Mass General Brigham and Harvard University in the USA have developed a novel way to peer into the body's biological clock and potentially forecast our future health.
To understand the innovation of the research, one must distinguish between two types of age. Chronological age is defined as the number of years that have passed since birth, whereas biological age reflects the condition of cells, tissues, and body systems. Two people born on the same day can be vastly different: one may function like a person a decade or two younger, while another already exhibits numerous cellular and molecular changes associated with aging.
The way the researchers measured biological age relies on transcriptomics—the study of gene expression. DNA can be likened to a vast instruction manual. All cells operate according to the same manual, but different cells use different parts of it. By examining active genes at any given moment, researchers can obtain a snapshot of the cell and hint at its biological age.
The study analyzed more than 11,000 gene expression samples from over 25 types of tissues, as well as data from mice, rats, and rhesus macaques. The results were unexpected: despite their different functions, liver, muscle, immune, and stem cells share similar aging patterns. Based on these data, the researchers developed gene expression clocks capable of calculating an estimated molecular age.
Unlike previous biological clocks that provided a single age, the new clocks break down aging into its components. This makes it possible to separately measure various processes occurring in the body, such as inflammation, energy production, or the state of the supportive environment for cells and tissues. When applied to people with chronic diseases such as Crohn's disease, ulcerative colitis, chronic kidney disease, heart failure, and Alzheimer's, the clocks indicated accelerated molecular aging compared to healthy individuals of the same age.
To test whether aging acceleration or deceleration could be detected, the researchers examined data from mice and rats that underwent changes known to affect lifespan, such as genetic alterations, dietary modifications, and drug treatments. Interventions known to extend life, like calorie restriction and certain medications, slowed the clocks and reduced the measured biological age. Fascinently, in some cases, biological rejuvenation was observed, with molecular signatures of aging weakening and even reversing.
If research in this field continues to develop, it could transform modern medicine. Doctors could monitor the body's aging rate in real-time and evaluate how treatments, nutrition, or physical activity affect long-term health. However, along with the great promise arise ethical concerns, such as the potential for biological discrimination where insurance companies or transplant committees might use biological age metrics.
