“Old age is dreadful, for it does not come alone…” True, very true. For indeed, old age brings with it many other “dreadful” consequences—physical and mental decline, as well as an increased risk of serious diseases such as cancer, heart disease, and dementia. Anyone who has reached their first “-ties” already gradually feels the impact of aging on their own body. But who would have imagined that the aging process does not wait until the “-ties” to begin, but starts in the early “-ties,” and that its patterns show many differences between the sexes? Who would also have imagined that aging is a synchronized process, as if the organs “communicate” about when they will start their downward trajectory?
Yet, all these astonishing findings and more are revealed for the first time by a study from researchers at Rockefeller University in New York, recently published in the prestigious scientific journal Science. The study analyzed seven million cells from 21 organs and produced the most detailed atlas to date of the aging process across numerous different cell types.
A Researcher’s Titan Project
Although this atlas (publicly available at epiage.net) was initially “mouse-sized,” using the aging process of mouse cells as its guide, as the study’s lead author, Dr. Junyue Cao, head of the Laboratory of Single-Cell Genomics and Population Dynamics at Rockefeller University, told Vima-Science, the mechanisms revealed are shared in humans. This new “giant” research effort provides a comprehensive view of aging—offering a roadmap for preventing and treating multiple age-related diseases simultaneously, rather than addressing them individually, as is currently the case. The detailed scrutiny of biological changes caused by aging is key to this upcoming “universal battle” against age and its consequences.
“Our goal was not only to understand what changes in the body with aging but also why and how these changes occur. By mapping both cellular and molecular changes, we can identify what drives aging. And this opens a major window for interventions targeting the aging process itself rather than its individual outcomes,” noted Dr. Cao.
How This Detailed Mapping Was Possible
The researcher explained that his graduate student, Ziyu Lu, perfected a method called single-cell ATAC-seq. This method shows how DNA is “packaged” inside each cell, revealing which regions of the genome are active—a marker for the state and function of each cell. “Remarkably, the entire resulting atlas was essentially created by a single graduate student. Most large atlases require massive collaborations involving dozens of labs, yet our method is much more efficient than other comparable approaches.”
The Downward Trajectory Starts Early
This technique was applied to millions of individual cells obtained from 21 organs of 32 mice in three age groups: one month (young), five months (middle-aged), and 21 months (old). In total, more than 1,800 distinct cell subtypes were identified, including many rare cell populations never fully described before. Researchers then tracked how the number of these cells changed as the mice aged. This tracking produced a major surprise compared to previous scientific assumptions. For decades, researchers believed that during aging, cell function changes rather than the number of cells of different types.
The new study showed, however, that about 25% of the cell types examined displayed significant changes in their numbers over time. “We found that roughly ¼ of 536 cell types across the different organs, and 1,828 cell subtypes, exhibited significant population changes associated with aging,” said Dr. Cao, adding that “although all organs showed changes in their cell populations, reproductive organs—particularly the ovaries and uterus—as well as the liver and thymus, exhibited the largest changes.”
It was also notable, according to the researcher, that “some cell types declined by more than 50% as early as five months of the mice’s lives, corresponding to the late 20s to early 30s in humans. These included satellite cells and tenocytes (tendon cells) in muscles, as well as precursor B cells in bone marrow. Aging appears to start early in these cell populations. At the same time, however, immune cells increased substantially in number over time.”
Unexpected Findings
These results demonstrate, as Dr. Cao emphasized, that “the system driving aging is far more dynamic than we thought. Remarkably, some of the cell number changes occur surprisingly early. Aging is therefore not something that comes relatively late in life but starts early, involving ongoing developmental processes.”
Further unexpected findings left researchers astonished when they observed how synchronized changes were across different organs—the activity of cells increased or decreased simultaneously, like a coordinated orchestra. Dr. Cao noted that “this pattern suggests that common signals, possibly factors circulating in the blood, contribute to coordinating the aging process throughout the body.”
The study also revealed significant differences in aging between sexes. Almost 40% of the cellular and molecular changes associated with aging differed depending on sex. For example, female mice exhibited much greater activation of the immune system as they aged. “We observed, among other things, a significant increase in B cell subtypes of the immune system only in female mice as they aged. This finding may explain why women more often develop autoimmune diseases. At the molecular level, we also identified tens of thousands of changes that affected only male or only female mice, indicating that sex is a key axis of heterogeneity in aging,” commented the study’s lead author.
Identifying the Culprit
So who was responsible for all these cellular changes triggered by aging? Researchers found that immune signaling molecules called cytokines appear to be responsible for many of the changes. This discovery opens the door to therapies targeting cytokines, offering the “holy anti-aging Grail”: slowing the aging process across multiple organs simultaneously!
Dr. Cao acknowledged that the study just published with his team is only the beginning of addressing aging from a new “holistic” perspective. “So far, we have identified the cell types most vulnerable to aging. The next major question is whether we can develop interventions targeting the specific mechanisms that drive aging, and our laboratory has already begun research in this direction.”
Research promises that in the future, the aging process may slow overall, allowing our organs to remain healthy like that “well-tuned” orchestra we mentioned—through our twenties, thirties, forties, and possibly beyond.
