Massive Mouse Cell Atlas Finds Aging Follows Coordinated Patterns Across Organs

In a Rockefeller University lab overlooking New York’s East River, aging no longer looks like slow, random decay. On a computer screen, scientists can scroll from a one-month-old mouse to a 21-month-old and watch entire organs change in lockstep: immune cells surge across tissues, specialized cells quietly vanish, and the genetic switches that govern their behavior flip in coordinated patterns.

Those images come from a new study that mapped how nearly every major organ in the mouse body ages, one cell at a time. The work, published Feb. 26 in Science, suggests that growing old is a synchronized, body-wide process written into the regulatory machinery of cells — and not just a matter of wear and tear.

“Our goal was to understand not just what changes with aging, but why,” said Junyue Cao, who led the study and heads the Laboratory of Single Cell Genomics and Population Dynamics at Rockefeller. “By mapping both cellular and molecular changes, we can identify what drives aging.”

A body-wide epigenomic map of aging

The research team built what amounts to an epigenomic atlas of mouse aging: a reference map showing how different cell types, and the DNA control regions that regulate them, shift across the lifespan. The scale is unusual. The group profiled about 7 million individual cells and nuclei from 21 organs in 32 mice — 16 males and 16 females — at three ages: 1 month (young adults), 5 months (middle age) and 21 months (old age for mice).

By examining chromatin accessibility — which stretches of DNA are open and available to be read — the scientists cataloged 536 main cell types and 1,828 finer subtypes across the body, along with roughly 1.3 million regulatory regions. The data are publicly available through an interactive portal (mouseagingatacatlas.org) and in raw form through the National Center for Biotechnology Information.

“This entire atlas was generated by a single graduate student,” Cao said in a statement released by Rockefeller, underscoring how an optimized technique called EasySci-ATAC let first author Ziyu Lu process hundreds of samples at scale.

Immune expansion, specialized-cell decline

The atlas shows that roughly a quarter of organ-specific cell types change in abundance with age. In broad terms, immune cells tend to expand across many tissues, while highly specialized cells that perform key functions often decline.

In old mice, plasma cells, macrophages and several subtypes of T and B cells were found in greater numbers in multiple organs at once. At the same time, the researchers saw fewer kidney podocytes, which help filter blood; fewer muscle satellite cells and tenocytes, which support muscle repair and tendon function; fewer lung aerocytes involved in gas exchange; and fewer granulosa cells in the ovary, which are vital for hormone production and fertility.

The pattern lines up with two well-known features of aging in humans: chronic, low-grade inflammation and a gradual loss of regenerative capacity.

“You see the immune system ramping up across the body, and the very specialized cells that keep organs working at their best are the ones that quietly disappear,” Cao said.

Aging appears coordinated—and starts earlier than expected

What surprised the team most, he said, was how coordinated those changes were across organs. When they tracked specific cellular subtypes — including distinct T cell, B cell, endothelial and fibroblast populations — they found that many rose or fell together in distant tissues as mice grew older.

Cao said the data suggest aging “starts earlier than we expected and unfolds in a coordinated way throughout the body,” with “similar cellular states [that] rose and fell together across different organs.”

Many of those shifts were already visible at five months, the study’s middle-age time point, not just in 21-month-old animals. “By five months of age, some cell populations had already begun to decline,” Cao said. “This tells us that aging isn’t just something that happens late in life; it’s a continuation of ongoing developmental processes.”

Regulatory “hotspots” hint at leverage points

The team also examined the molecular switches underlying those cellular shifts. Out of about 1.3 million DNA regulatory regions, they identified roughly 279,000 that changed accessibility with age. Most of these changes were specific to one or a few cell types. But a smaller group — around 1,000 regions — appeared to be “hotspots”: repeatedly altered across many different cell types.

Those hotspots clustered near genes involved in immune and inflammatory pathways, cytokine signaling and developmental programs, the study found. Promoter regions for genes such as Il7, which influences immune cell survival, often became more accessible in older mice, while enhancers associated with developmental transcription factors like Sox4 and Sox11 tended to become less accessible.

“These findings challenge the idea that aging is just random genomic decay,” Cao said. “We see specific regulatory hotspots that are particularly vulnerable.”

Because those hotspots appear across many tissues, they may represent leverage points where a single intervention could influence aging in several organs at once. Researchers caution, however, that changes in chromatin accessibility do not automatically prove a functional role in disease or decline. Follow-up work will need to test whether nudging these regulatory regions back toward a youthful state is either effective or safe.

Male and female aging diverge

The atlas also underscores how differently males and females age at the cellular and molecular levels.

The study found that about 40 percent of the age-related changes in cell population sizes showed sex-dependent patterns, meaning a cell type might expand with age in males but remain stable or shrink in females, or vice versa. At the chromatin level, tens of thousands of regulatory regions showed age-related changes only in one sex.

In many cases, regulatory regions that opened up specifically in aging females were near genes associated with antiviral responses and cell-cycle regulators such as Cdkn2b, a gene linked to cellular senescence. Press materials from Rockefeller noted that females showed “much broader immune activation” with age, which Cao said could help explain why autoimmune diseases are more common in women.

“These data reinforce that sex is a major biological variable in aging,” he said. “If we want to design therapies that work for everyone, we need to understand that male and female bodies don’t age in exactly the same way.”

Why the atlas matters—and what it can’t yet prove

The work arrives as health systems worldwide confront the consequences of aging populations. The United Nations estimates that there were about 703 million people age 65 or older in 2019 and projects that number will rise to 1.5 billion by 2050. In many wealthy countries, older adults already account for nearly one in five residents, straining pension systems, long-term care and budgets for chronic disease.

Against that backdrop, researchers and companies are increasingly focused on extending healthspan — the number of years people remain healthy and independent — rather than simply adding years of life. The new atlas gives scientists a detailed look at where and how aging-related changes accumulate, potentially helping identify targets to slow or prevent multiple diseases at once.

In the near term, the resource is likely to guide basic research and drug discovery. Scientists can use it to pinpoint vulnerable cell types to protect, such as podocytes or muscle stem cells, and inflammatory cell states to dampen. The catalog of regulatory hotspots and transcription factor motifs may help in designing more precise immune-modulating or epigenetic drugs.

The data could also inform how researchers design animal experiments and, eventually, human trials, including decisions about which tissues to monitor and how to account for sex-based differences.

There are significant caveats. Mice age faster than humans, and not all mouse cell types or regulatory programs have direct human counterparts. The study captured only three time points, offering snapshots rather than continuous trajectories. And the atlas is observational: it shows what correlates with age but cannot prove which changes cause disease or frailty.

Cao said he sees the work as infrastructure for the field rather than an endpoint.

“The system is far more dynamic than we realized,” he said. “This atlas is really a starting point. It tells us where to look and what to test, but actually changing aging will require many more experiments.”

For now, the map offers an unusually detailed view of what it means, at the level of individual cells and their DNA control panels, to grow old. In place of a vague idea of bodies “wearing out,” it reveals a pattern of synchronized shifts rippling through organs over time — a kind of hidden timetable of aging that researchers are only beginning to read.