New research reveals senescence is not a single process but a spectrum of cellular states with implications for precision longevity therapies.
The accumulation of senescent cells is increasingly seen as a major contributor to aging and age-related diseases. These senescent cells – often referred to as “zombie cells” because they cease dividing but refuse to die – build up in tissues over time, secreting inflammatory and tissue-damaging factors. Their presence has been linked to chronic diseases such as osteoarthritis, cardiovascular disease and neurodegeneration. A growing field of research has sought ways to eliminate these cells, and while functional differences have been observed across tissues, senescence within a given cell type has often been treated as uniform.
Three paths through cellular purgatory
A new study led by researchers at Johns Hopkins University, published in Science Advances, challenges this assumption, revealing that even within a single cell type – human dermal fibroblasts – senescence is not a single outcome but a spectrum of distinct subtypes [1]. By identifying three different ‘paths’ that skin cells may take as they enter senescence, the findings open the door to more precise interventions against the harmful consequences of cellular aging.
Longevity.Technology: The identification of distinct senescence subtypes within human dermal fibroblasts marks important progress in our understanding of cellular aging. This research underlines that senescence is not a monolithic state, but a spectrum of functionally distinct subtypes with both reparative and pathological roles. The prospect of targeting harmful subtypes while preserving beneficial ones is an important refinement to senotherapeutic strategies – however, senescence remains a complex and context-dependent process, and caution is needed. Subtype identification currently relies on sophisticated imaging and machine learning methods that are not yet directly applicable in vivo, and the molecular mechanisms underpinning each subtype are not fully resolved. There is also a risk that interventions may have unintended effects if the functional roles of subtypes are not fully understood. Senescence is no longer a binary problem but a nuanced, targetable landscape, and future therapies will need to match that complexity if they are to safely and effectively extend healthspan.
Classifying the zombie subtypes
The team at Johns Hopkins developed a framework called SenSCOUT, which uses high-content imaging and machine learning to analyze single-cell morphology. By examining more than 50,000 skin cells from donors aged between 20 and 89 years, both before and after exposure to senescence-inducing agents, the researchers identified eleven morphological clusters, of which three (named C7, C10 and C11) were confirmed as bona fide senescence subtypes; these subtypes were characterised by differences in size, nuclear structure, biomarker expression and secretory profiles [1].
“We’ve known that senescent skin cells are different from senescent immune cells or senescent muscle cells. But within a cell type, senescent cells are often considered the same – in essence, skin cells are either senescent or not, for example,” said Jude Phillip, an assistant professor of biomedical engineering at Johns Hopkins University. “But we’re finding that when a skin cell goes into senescence, or a zombie-like state, the cell could go down one of three different paths, each leading to a slightly different subtype [2].”
Not all senescence is created equal
One key finding was that the C10 subtype showed a strong correlation with chronological aging, making it a potential biomarker for biological age; by contrast, C7 and C11 appeared more associated with stress-induced senescence, such as that triggered by DNA damage or oxidative stress. In functional assays, the subtypes also exhibited different responses to senolytic treatments – drugs designed to selectively eliminate senescent cells. Notably, C7 cells were more sensitive to the combination of dasatinib and quercetin, while C10 cells were more resistant, suggesting that a one-size-fits-all approach to senolysis may miss important nuances [1].
A subtler view of cellular ageing
Senescence, long understood as a double-edged sword in biology, provides a natural brake against cancer by halting the proliferation of damaged cells; however, when senescent cells accumulate and linger, they drive chronic inflammation – a process sometimes referred to as ‘inflammaging’. The new findings help explain how these seemingly contradictory effects can coexist within a single tissue.
The SenSCOUT platform not only identified the subtypes but also demonstrated that the burden and composition of senescent cells in an individual’s skin could predict their susceptibility to further senescence following stress, such as chemotherapy. Cells with a higher baseline senescence score were more likely to accumulate damage-induced senescent cells, providing a potential link between baseline cellular health and resilience to therapies [1].
“With our new findings, we have the tools ready to develop new drugs or therapies that preferentially target the senescence subtype that drives inflammation and disease as soon as it is identified,” Phillip said [2].
Mapping the future of precision senotherapy
The implications extend beyond dermatology; understanding and targeting specific senescence subtypes could have relevance across a range of tissues and conditions, from lung fibrosis to cardiovascular disease. Nonetheless, as the researchers themselves acknowledge, translating these findings into clinical practice will not be immediate; the current classification depends on sophisticated ex vivo imaging and machine learning; further work will be needed to define molecular signatures that are accessible in vivo.
Moreover, there is a risk that selectively clearing one subtype could disrupt beneficial processes such as wound healing or tumour suppression; a deeper understanding of the dynamic roles of each senescence subtype will be essential to avoid unintended consequences.
This research moves the field closer to a more precise, personalised approach to senotherapy – one that recognises the complexity of senescence rather than treating it as a binary state to be eradicated wholesale. As the tools for identifying and manipulating senescent cells become more refined, the prospect of safely extending healthspan by tackling the cellular roots of aging comes ever more sharply into focus.
Main image shows skin-related fibroblasts with nuclei stained green and f-actin stained red.
Credit: Jude Phillip, Johns Hopkins University
[1] https://www.science.org/doi/epdf/10.1126/sciadv.ads1875
[2] https://hub.jhu.edu/2025/04/25/zombie-cell-shape-related-to-subtype/
