LongeCityNews Last Updated: 20 March 2026 - 04:04 AM

Senescent cells accumulate with age in tissues throughout the body, the result of a growing imbalance between the pace at which somatic cells enter the senescent state in response to damage, stress, and the Hayflick limit on the one hand and the pace of clearance of senescent cells by the immune system on the other. The growing burden of senescent cells disrupts tissue structure and function via inflammatory signaling. This is thought to produce a significant, important contribution to degenerative aging, and over the past fifteen years cellular senescence has become major focus of life science research and development.

Today the field of senotherapeutics, meaning anti-aging therapies that in some way target senescent cells, is in the strange superimposed state of both existing and yet to emerge. Senostatics slow the rate at which cells become senescent, and the low cost, generic mTOR inhibitor rapamycin appears to be a legitimate senostatic. Senolytics selectively destroy senescent cells, and the senolytic combination of dasatinib and quercetin, the subject of several early stage clinical trials, also costs little. Senomorphics impede the bad behavior of senescent cells, and many existing drugs might qualify as senomorphic to some degree.

The two named options above are readily available via off-label prescription to any older individual willing to try. Yet use is not widespread. The large clinical trials that would provide concrete demonstrations of efficacy (or lack of same) have not been conducted, and do not seem likely to be conducted. Generic drugs cannot command enough revenue to support the regulatory cost of large clinical trials. The research community and longevity industry is instead focused on the development of a wide range of novel senotherapeutics, and progress largely remains at a preclinical stage. Today's open access paper is an opinionated tour, but gives a sense of where things stand, the variety of approaches under consideration.

Emerging strategies in senotherapeutics: from broad-spectrum senolysis to precision reprogramming

Cellular senescence, originally described as a finite proliferative arrest in cultured somatic cells, has since been recognized as a central mechanism underlying aging and the development of age-associated disorders. The progressive accumulation of senescent cells (SnCs) promotes chronic inflammation through the senescence-associated secretory phenotype (SASP) and circumvents immune-mediated clearance by upregulating pro-survival and immune checkpoint pathways. Early "first-generation" senolytics, including navitoclax (ABT-263) and the dasatinib-quercetin (D + Q) combination, provided proof-of-concept that selective removal of SnCs can alleviate certain fibrotic, metabolic, and cardiovascular pathologies in preclinical studies. However, these agents exhibited notable drawbacks, such as dose-dependent thrombocytopenia, variable therapeutic efficacy, and the emergence of resistance mechanisms. Consequently, current research has shifted toward precision senotherapy, though significant translational challenges remain.

This review synthesizes three next-generation strategies developed to address limitations of early senolytic agents. (1) Immune-based senolysis: This approach applies immuno-oncology principles to counter immune evasion of SnCs. Strategies include blocking immunosuppressive ligands such as GD3 ganglioside, engineering chimeric antigen receptor (CAR) T cells to target senescence-specific surface markers like urokinase-type plasminogen activator receptor (uPAR), and exploiting metabolic vulnerabilities (e.g., glutaminolysis and ferroptosis) to sensitize SnCs to immune-mediated clearance. (2) Tissue-precision proteolysis-targeting chimeras (PROTACs): These agents recruit organ- or tissue-specific E3 ligases (e.g., von Hippel-Lindau (VHL)) to selectively degrade anti-apoptotic proteins such as BCL-xL. Localized activity may reduce systemic toxicity and mitigate dose-limiting effects observed with traditional inhibitors. (3) Microbiome-epigenetic interplay: This strategy modulates the gut-liver axis to enhance senolytic efficacy. Short-chain fatty acids (SCFAs), such as butyrate, epigenetically regulate drug transporter expression and suppress the SASP, while dietary interventions may create a microenvironment favorable to senolysis.

These approaches offer potentially more targeted and personalized therapeutic options but face significant challenges, including immunopathology, manufacturing complexity, off-target effects, and long-term safety concerns. The ongoing shift from broad inhibition to precision reprogramming represents a promising but preliminary step in the treatment of age-related diseases.

Researchers publishing in Cell Reports Medicine have described the development of a lipid nanoparticle (LNP) that delivers mRNA to neurons in order to stop the formation of tau aggregates and fight Alzheimer’s disease.

Tau and amyloids

Amyloid beta deposition between neurons and tau aggregation within neurons are both hallmarks of Alzheimer’s disease, and evidence suggests that the latter is potentially more significant than the former [1]. While some potential therapies have been discovered that may disaggregate these tau tangles after they have formed [2], no therapy has yet been approved by the FDA to do this.

This paper zeroes in on a specific ligase that can naturally do this: TRIM11, which does not depend on ATP to do its work. While this ligase is overexpressed in brain cancers [3], neurons that overexpress TRIM11 have been found to fight back against tau aggregates and this protein is downregulated in Alzheimer’s disease [4]. While developing therapeutics that cross the blood-brain barrier (BBB) is difficult, certain LNPs that contain mRNA-based treatments have been found to do exactly this [5].

Sneaking the mRNA in

These researchers developed an LNP, PLNP, that mimicks acetylcholine, a neurotransmitter, in order to gain access to target cells past the BBB. When the researchers exposed neuron and microglial cell lines to PLNP, this approach yielded significant results compared to naked mRNA, which was hardly uptaken at all. The PLNP-delivered mRNA was found in the cells’ cytosol, evading degradation by lysosomes. Exposing these cells to a choline inhibitor significantly limited mRNA uptake, demonstrating that the PLNP particles were going through the expected pathway.

The researchers then tested their PLNP on wild-type Black 6 mice. Compared to other, less targeted, LNPs, their approach yielded nearly 17 times as much delivered mRNA, as measured by the fluorescent reporters they used to test it. This mRNA was found throughout all regions of the rodents’ brains.

The next experiment was done with actual TRIM11 attached to a fluorescent reporter. Just like with the previous experiments, regular LNPs were found to be much less effective than PLNP when tested in vitro.

Most importantly, the TRIM11 mRNA appeared to be doing its work; when it was administered alongside okadaic acid, which causes tau pathology, there were substantially fewer tau tangles. The TRIM11 generated by the cells was co-localized with the tau tangles that did exist, demonstrating its direct effect. “These results confirm that PLNP-delivered TRIM11 localizes to and interacts with intracellular Tau aggregates in SH-SY5Y and Neuro2A cells.”

Effective against Alzheimer’s in a mouse model

The researchers then administered their PLNP to male mice that have three key mutations that make them susceptible to Alzheimer’s disease. At around 7 and a half months of age, these mice develop significant tau tangles in their brains. Three times over two weeks, these mice were given PLNP injections and then examined for behavior and brain changes.

The results were substantial; there was no statistically significant difference between the PLNP-treated tau-prone mice and wild-type mice. The treated mice showed a strong preference for novel objects, better performance on the Morris water maze test, behavior nearly identical to wild-type mice when placed in an open field, and nesting behavior that was also nearly identical. These results persisted even three months after treatment. Similar results were also found when this treatment was given to 5.5-month-old mice, which had not yet developed signs of tau pathology.

Markers of tau pathology, which are normally widely abundant in this mouse strain, were practically absent in the treated mice. These also included inflammatory biomarkers such as IL-6 and TNF-α; microglial overactivation, which is usually prevalent in this mouse strain, was suppressed by the treatment. These effects were found across the brain, including both the hippocampus and the cerebral cortex. “Together, these results demonstrate that systemically administered PLNP-mTRIM11 effectively reduces insoluble Tau aggregates and suppresses neuroinflammatory responses in the AD brain.”

Overall, this appears to be a highly promising treatment that “offers a disease-modifying strategy for preclinical intervention in AD.” However, the researchers note key limitations. The main experiments were exclusively done on male mice that were genetically engineered to be prone to Alzheimer’s. There may also be potential off-target effects; tau protein has a nautral function, and the researchers are concerned that untargeted TRIM11 may affect more than just harmful aggregates. They intend to use older animals, other models, and more biomarkers in order to validate their findings.

Literature

[1] Brier, M. R., Gordon, B., Friedrichsen, K., McCarthy, J., Stern, A., Christensen, J., … & Ances, B. M. (2016). Tau and Aβ imaging, CSF measures, and cognition in Alzheimer’s disease. Science translational medicine, 8(338), 338ra66-338ra66.

[2] Seidler, P. M., Murray, K. A., Boyer, D. R., Ge, P., Sawaya, M. R., Hu, C. J., … & Eisenberg, D. S. (2022). Structure-based discovery of small molecules that disaggregate Alzheimer’s disease tissue derived tau fibrils in vitro. Nature communications, 13(1), 5451.

[3] Di, K., Linskey, M. E., & Bota, D. A. (2013). TRIM11 is overexpressed in high-grade gliomas and promotes proliferation, invasion, migration and glial tumor growth. Oncogene, 32(42), 5038-5047.

[4] Perez-Nievas, B. G. (2023). TRIMming Tau away. Nature Neuroscience, 26(9), 1481-1481.

[5] Wang, C., Xue, Y., Markovic, T., Li, H., Wang, S., Zhong, Y., … & Dong, Y. (2025). Blood–brain-barrier-crossing lipid nanoparticles for mRNA delivery to the central nervous system. Nature materials, 24(10), 1653-1663.

An increasing number of cells in aged tissues enter a senescent state, ceasing replication and generating pro-inflammatory signals that are disruptive to tissue structure and function. In the case of innate immune cells, however, there is some question as to whether they are in fact senescent or just adopting features of senescence, and that leads to debate over whether these cells are in fact harmful. Neutrophils, also known as polymorphonuclear leukocytes, are an important cell type in the innate immune system. Here, researchers show that neutrophils in aged individuals exhibit features of cellular senescence, but stop short of calling them senescent cells. They also show that this behavior is harmful, as it impedes the immune response to infection.

Aging drives increased susceptibility to respiratory infections by Streptococcus pneumoniae (pneumococci). Polymorphonuclear leukocytes (PMNs) are among the first responders in the lung following pneumococcal infection and are required for bacterial clearance. However, PMN antimicrobial function declines with age. To identify mechanisms underlying this decline, we performed RNA sequencing on PMNs in the lungs of young and old mice following pulmonary infection with S. pneumoniae. We observed significant transcriptomic differences across host age.

Transcriptional analysis followed by functional validation revealed that in infected mice, PMNs from aged hosts failed to upregulate several effector activities including glycolysis and subsequent mitochondrial reactive oxygen species (ROS) production, which are necessary for bacterial killing by PMNs. Conversely, PMNs in aged mice displayed a higher senescence-associated secretory phenotype (SASP) score and upregulated pathways involved in cellular senescence. Follow-up functional characterization found that in uninfected hosts, PMNs in aged mice expressed higher levels of SASP factors IL-10, TNFα, and ROS, had a lower incidence of apoptosis, and had a higher proportion of cells positive for senescence-associated β-galactosidase, features of a senescent-like phenotype.

Importantly, blocking TNFα, one of the SASP factors, altered the senescent-like phenotype and boosted the antibacterial activity of PMNs from aged hosts and increased host resistance to S. pneumoniae pulmonary infection. In conclusion, host aging is associated with altered PMN phenotype, including a shift toward senescent-like energy-deficient cells, which contribute to impaired host defense and represent potential targets for improved interventions against infection in older adults.

Link: https://doi.org/10.1111/acel.70435

The standard view of the evolution of aging is that aging exists because natural selection operates more strongly on features of young animals than on features of old animals. A faster time to reproductive success will be selected over a slower time to reproductive success. This leads to the evolution of biological systems that are front-loaded for early efficiency, but that decay to become dysfunctional over time. Aging is near universal but not actually universal, however. For example, varieties of hydra are in fact immortal, exhibiting no loss of function over time. How to explain the existence of the few immortal species in the presently dominant view of the evolution of aging? Here, researchers build a model of the evolution of aging in which a runaway feedback loop leading to immortality is a possible outcome.

In recent years, senescence is increasingly understood as a process of damage accumulation that accelerates with age throughout an organism's lifespan. That understanding has rarely been introduced to senescence evolution theory. In classic models, including Mutation accumulation and Antagonistic pleiotropy, the intensity of selection over genes is determined by the timing of their effect on mortality. They conclude senescence evolution occurs because of weak selection on late-acting genes. Despite the success of these classic explanations, several phenomena have not been fully addressed. One is the existence of species exhibiting negligible senescence - mortality rate that remains constant with age.

Here we explore, consistent with recent evidence, an alternative model: where genes affect mortality throughout an organism's lifespan, and the shape of this effect determines selection. We expanded Hamilton's classic model of senescence evolution using these notions. Our model takes into account evolutionary dynamics between external mortality risk, potential mortality risk from internal damage, reproduction start age, and reproduction rate. The analysis of the model suggests biological limitations on reducing the potential mortality risk from internal damage can lead to a positive feedback loop in senescence evolution where genes that slow senescence can increase selection for further senescence retardation. Our model sheds light on several phenomena, not fully explained by classic theory, including Peto's paradox, Strehler-Mildvan correlation, and negligible senescence.

Link: https://doi.org/10.1002/ece3.72988