Small extracellular vesicles found to spread cellular senescence in models of aging

“Collectively, these findings identify sEVs released by senescent and aged cells as an important mechanism of intercellular communication and a key mediator of paracrine senescence.”

BUFFALO, NY — October 29, 2026 — A new research paper was published in Volume 18 of Aging on October 8, 2026, titled “Small extracellular vesicles as mediators of paracrine senescence in cellular models of aging.”

The study found that small extracellular vesicles (sEVs) released by senescent cells can transmit signals that promote senescence in neighboring cells. Using human cellular models of aging, the researchers demonstrated that these membrane-enclosed particles could trigger cell-cycle arrest and DNA damage responses without activating the classical inflammatory pathways associated with senescence. The findings reveal another mechanism through which aging cells may influence their surroundings.

The research was led by equal-contributing first authors Aina M. Llabrés-Mas, Antonio Merino-Navarro and Marta Menéndez-García, all affiliated with the Spanish National Research Council (CSIC), Madrid, Spain. Corresponding author Ana O’Loghlen is affiliated with the same institution.

Cellular senescence is a process in which cells enter a stable state of growth arrest in response to stress, damage or other signals. Although senescence can help prevent uncontrolled cell proliferation and support tissue repair, the accumulation of senescent cells is associated with aging, chronic inflammation and age-related diseases.

Senescent cells can influence surrounding tissues through the senescence-associated secretory phenotype (SASP), which includes inflammatory molecules, growth factors and other signaling substances. These signals can sometimes induce paracrine senescence, a process in which senescent cells promote senescence in nearby, previously proliferating cells.

However, not all senescent cells produce the same inflammatory signals. Cells expressing high levels of p16^INK4A, a protein involved in regulating cell-cycle progression, can enter a stable growth-arrested state without developing the classical inflammatory SASP. This raises questions about how these cells communicate with their surroundings and potentially influence tissue aging.

To investigate this, the researchers examined small extracellular vesicles, membrane-bound particles that transport proteins, nucleic acids and lipids between cells. These vesicles act as biological messengers, transferring molecular information that can influence the behavior of recipient cells.

The team used human primary fibroblasts genetically modified to express p16^INK4A. They compared these cells with normally proliferating fibroblasts and cells expressing an oncogenic form of RAS, which served as a model of senescence associated with a classical inflammatory SASP.

Initial experiments showed that p16^INK4A-expressing fibroblasts produced little or no classical inflammatory SASP, while RAS-induced senescent cells released higher levels of inflammatory factors, including interleukin-6 (IL-6) and interleukin-1β (IL-1β).

Despite lacking a prominent inflammatory response, p16^INK4A-expressing fibroblasts released significantly more small extracellular vesicles than proliferating control cells. The researchers isolated these particles using ultracentrifugation and characterized them through nanoparticle tracking analysis, flow cytometry and established extracellular vesicle markers, including ALIX, TSG101, CD9, CD63 and CD81. The analyses confirmed increased vesicle release without significant differences in average particle size.

The researchers next investigated whether these vesicles could influence healthy recipient cells. Small extracellular vesicles isolated from p16^INK4A-expressing fibroblasts were applied to proliferating human fibroblasts for 72 hours.

The treatment significantly reduced the proportion of cells expressing Ki-67, a marker of proliferation, while increasing p16^INK4A expression. Further analysis revealed increased γH2AX, a marker of DNA damage responses. Together, these findings demonstrated that vesicles released by p16^INK4A-expressing cells could induce several characteristics of cellular senescence in previously proliferating fibroblasts.

Importantly, these changes occurred without substantial activation of classical inflammatory signaling. Unlike vesicles released by RAS-induced senescent cells, those from p16^INK4A-expressing fibroblasts did not significantly increase IL-6 or IL-8 expression in recipient cells. IL-6 secretion also remained unchanged after the vesicles were removed and the cells were maintained for another five days.

These findings suggest that extracellular vesicles can promote senescence-associated changes without inducing a conventional inflammatory SASP response, indicating that different forms of senescence may involve distinct communication mechanisms.

To determine whether this phenomenon extended beyond p16^INK4A-induced senescence, the researchers examined two additional cellular models of aging. One involved progerin, an abnormal protein associated with premature aging, while the other used a dominant-negative form of telomeric repeat-binding factor 2 (TRF2), which disrupts telomere protection and mimics aspects of replicative senescence.

Small extracellular vesicles collected from both models reduced proliferation in healthy recipient fibroblasts, providing further evidence that vesicle-mediated communication can occur across different forms of cellular senescence.

The researchers also investigated fibroblast cultures derived from human donors of different ages. Vesicles isolated from cells obtained from a 67-year-old donor reduced DNA synthesis in fibroblasts derived from a one-year-old donor, indicating impaired proliferative activity.

In another experiment, the researchers pooled vesicles collected from four older donors, aged 67 to 81 years, and applied them to fibroblast cultures from four young donors, aged one to three years. These particles increased senescence-associated β-galactosidase activity, a commonly used marker of cellular senescence, in the young recipient cells.

These results suggest that extracellular vesicles released by aged cells can transmit senescence-associated signals to younger cells under laboratory conditions. However, whether the same process contributes to aging in living tissues remains to be established.

“Overall, our findings establish that the p16-associated evSASP is sufficient to mediate paracrine senescence without the induction of a classical SASP, highlighting EV as an important mechanism by which p16-expressing cells influence the tissue microenvironment.”

The findings support a broader understanding of the senescence-associated secretory phenotype. Rather than consisting exclusively of soluble inflammatory molecules, the SASP may include two complementary components: a soluble fraction, known as sSASP, and an extracellular vesicle-associated fraction, known as evSASP.

Unlike freely released proteins, extracellular vesicles are protected by a lipid membrane that can shield their contents from degradation. This allows them to transport molecular signals between cells and potentially influence cellular behavior beyond their immediate surroundings.

The researchers propose several possible mechanisms. Vesicles may carry DNA fragments capable of activating DNA damage responses or transfer proteins and microRNAs that influence cell-cycle regulation. Previous research has implicated molecules such as IFITM3 and the receptor EphA2 in vesicle-mediated signaling. However, the specific molecular cargo responsible for the effects observed in this study remains unidentified.

The study has important limitations. All experiments were performed in cultured human cells, including genetically modified fibroblasts and donor-derived cell lines. The findings have not been validated in animal models or living human tissues, and the researchers did not identify which vesicle-associated molecules were directly responsible for inducing senescence.

Future studies will need to characterize these molecular signals and determine whether blocking vesicle release or uptake can reduce paracrine senescence. Research in more complex biological systems will also be necessary before considering potential therapeutic applications.

Overall, the study identifies small extracellular vesicles as an important means of communication between senescent and proliferating cells in laboratory models of aging. By demonstrating that these particles can promote growth arrest and DNA damage responses without activating classical inflammatory pathways, the findings broaden our understanding of how senescence-associated signals may spread and provide a foundation for investigating their contribution to cellular aging and age-related tissue dysfunction.

Paper DOI: https://doi.org/10.18632/aging.206425   

Corresponding author: Ana O’Loghlen - ana.ologhlen@cib.csic.es   

Keywords: p16^INK4A, extracellular vesicles, senescence, aging, SASP

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