Senescent cells are cells that have permanently stopped dividing but refuse to die. They secrete a toxic cocktail of inflammatory molecules known as the senescence-associated secretory phenotype, or SASP, and even small numbers of transplanted senescent cells can accelerate aging in mice. Conversely, drugs that clear these cells, called senolytics, have extended healthspan and improved age-related phenotypes in animal studies. The landmark dasatinib-plus-quercetin combination, along with fisetin and UBX0101, established proof of concept, but small-molecule senolytics lack precision and have produced disappointing clinical results accompanied by side effects such as diarrhea, anemia, and rash.

Immunotherapy offers a sharper alternative. uPAR, the receptor for urokinase-type plasminogen activator, is broadly expressed on senescent cells and tumor cells but largely absent from healthy young tissue. CAR T cells engineered against uPAR have already reversed senescence-driven pathologies in mice, including liver fibrosis and metabolic dysfunction. Yet the approach carries risks: high doses of uPAR CAR T cells caused hypothermia, weight loss, and elevated cytokines in mice, and CAR T cells, once infused, expand unpredictably from patient to patient, making their toxicity hard to titrate. The team therefore turned to a bispecific T-cell engager, or BiTE, a soluble antibody construct that recruits a patient’s own T cells to target cells and vanishes from the bloodstream within days, allowing dosing to be adjusted or halted at will.

The engineered molecule, named hGFD-CD3, links the GFD domain of human uPA, the natural ligand of uPAR, to an anti-CD3 antibody fragment derived from the clinically tested drug acapatamab, with a non-functional Fc region added to extend its half-life. In laboratory dishes, the engager bound uPAR-positive senescent human lung fibroblasts and CD3-positive T cells simultaneously, killing senescent cells with an IC50 of just 0.015 nanomolar, a potency the authors attribute to the moderate, natural affinity of the ligand-based recognition domain. Young cells and cells treated with a control construct lacking the GFD domain were spared. Treated T cells upregulated the activation markers CD25 and CD69 and released granzyme along with the inflammatory cytokines TNF-alpha and IFN-gamma.

The in vivo story was more complicated, and it is here that the study makes its most consequential discovery. When aged mice received a high dose of the mouse version of the engager, 1 milligram per kilogram, they died within 24 hours; 0.3 milligrams per kilogram caused ruffled fur, anorexia, and a 20- to 30-fold surge in the liver enzymes AST and ALT. Histopathology pointed squarely at the liver. The reason, the team found, is that liver sinusoidal endothelial cells are among the very few non-hematopoietic cells in the body that express uPAR. Unlike the continuous, basement-membrane-backed vessels of the lung and kidney, liver sinusoids are fenestrated and lack a basement membrane, so widespread destruction of their endothelial lining collapses the microcirculation and injures hepatocytes. In uPAR knockout mice, the engager caused no liver damage at all, proving the toxicity was uPAR-dependent. The same hepatotoxicity appeared with uPAR CAR T cells, even in macrophage-deficient NSG mice, overturning the earlier hypothesis that macrophage activation was to blame.

Crucially, that toxicity proved monitorable and avoidable. At 0.1 milligrams per kilogram, a dose that left liver enzymes and tissues unremarkable, weekly mGFD-CD3 treatment for three weeks significantly reduced uPAR, p16INK4a, and p21 expression across tissues of 22-month-old mice, decreased senescence-associated beta-galactosidase staining in fat, liver, and lung, and suppressed SASP gene expression in liver RNA-sequencing analysis. The engager physically bridged T cells to senescent cells in tissue sections, activated peripheral T cells, and reduced uPAR-positive macrophages. Cytokine rises were modest, roughly twofold, far below cytokine-storm thresholds, and returned to baseline after treatment stopped.

The long-term benefits in mice were striking. Three months after starting treatment, circulating SASP factors had fallen, liver and lung fibrosis had eased, glomerulosclerosis was attenuated, and bone remodeling shifted favorably, with fewer osteoclasts and more active osteoblasts. After six months, treated mice showed better grip strength, treadmill endurance, walking speed, and hanging endurance, along with denser skeletal muscle fibers, less trabecular bone loss, a higher lean-mass fraction, healthier subcutaneous fat distribution, lower fasting glucose, and improved glucose tolerance and insulin sensitivity. Serum transaminases remained within normal ranges throughout, and no tissue showed pathological abnormalities.

The team then crossed the species barrier. In 24-year-old rhesus macaques, roughly equivalent to a 70-year-old human, a dose-escalation trial showed no abnormalities at 10 or 20 micrograms per kilogram, while 40 micrograms per kilogram produced anorexia and a 50 to 100 percent rise in AST and ALT, though still within the normal reference range. At the selected 20-microgram-per-kilogram dose given every three days, two of three macaques tolerated treatment without clinical signs; one showed transient anorexia and transaminase elevations that peaked at 108 U/L for AST and 134 U/L for ALT and cleared within three days. Temporary drops in white blood cells, neutrophils, lymphocytes, and blood pressure all rebounded by day three, a pattern consistent with T-cell migration into tissues rather than destructive depletion, and these fluctuations diminished with repeated dosing.

Over 90 days of follow-up, senescent cell burden in subcutaneous fat, measured by beta-galactosidase staining, fell by day 42, and uPAR, p16INK4a, and p21 expression dropped in fat, muscle, and skin before drifting back up by day 90 as senescent cells slowly re-accumulated. Serum SASP levels fell in parallel, and immune-cell gene signatures declined, indicating reduced tissue inflammation. The macaque with the heaviest senescent burden was the one with the strongest transient enzyme and cytokine responses, reinforcing the authors’ proposal that liver function tests can serve as a practical, biomarker-guided safety gauge for uPAR-targeted senolytics. Because senescent cells are rare, non-proliferative, and take months to return, the team argues that intermittent, low-dose regimens, potentially as infrequent as twice yearly, could impose minimal treatment burden. They caution that for preventive anti-aging use the risk-benefit balance demands careful evaluation, and suggest that diseases with clear unmet need, such as chronic kidney disease, Alzheimer’s disease, and liver fibrosis, may be the most sensible first indications for clinical translation.

Subject of Research: Senolytic immunotherapy targeting uPAR with a bispecific T-cell engager in aged mice and non-human primates

Article Title: uPAR‐Targeting T Cell Engager Exerts Senolytic Effects in Mice and Non‐Human Primates With Serum Aminotransferase Activity as a Safety Monitor

Article References: Deng, J., Zeng, X., Guo, J., Li, L., Zou, S., Liu, N., He, S., Yan, L., Wang, Q., Zhu, Y., Wang, B., Yang, D., Lv, L., & Zhao, X. (2026). uPAR ‐Targeting T Cell Engager Exerts Senolytic Effects in Mice and Non‐Human Primates With Serum Aminotransferase Activity as a Safety Monitor. Aging Cell, 25(10), Article e70742. https://doi.org/10.1111/acel.70742

Image Credits: AI Generated

DOI: 10.1111/acel.70742

Keywords: senolytics, cellular senescence, uPAR, T-cell engager, BiTE, aging, hepatotoxicity, aminotransferases, CAR T cells, rhesus macaques, SASP, liver sinusoidal endothelial cells

Liver fibrosis, characterized by excessive deposition of extracellular matrix components, leads to the disruption of normal hepatic architecture and function. Central to this process is the phenomenon of capillarisation, where specialized fenestrated LSECs lose their unique morphology and transform into a continuous, capillary-like endothelium. This transformation impairs the highly selective filtration function of LSECs, contributing to the progression of liver fibrosis and, ultimately, cirrhosis. Understanding and reversing this capillarisation have been long-standing objectives, as the restoration of LSEC function could halt or even reverse fibrotic progression.

The research team led by Liu, W., Liu, Y., and Zhang, L. engineered nucleic acid-based spherical nanoparticles designed to intervene in the cellular pathways that govern LSEC capillarisation. Unlike conventional small molecules or antibody therapies, these nucleic acid spheres offer a multifaceted mechanism of action: they can be programmed to deliver specific sequences capable of modulating gene expression, interfering with pathological signaling cascades, and promoting cellular reversion to a healthy phenotype. Their unique spherical configuration enhances stability and cellular uptake, bypassing many shortcomings encountered by traditional nucleic acid therapies.

At the molecular level, it is well understood that capillarisation is driven by aberrant activation of pro-fibrotic signaling pathways, including those mediated by transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), and Notch signaling. These pathways collectively promote endothelial dedifferentiation, loss of fenestrae, and basement membrane deposition. The nucleic acid spheres are designed to target key molecules within these signaling networks, thereby attenuating fibrotic signaling and restoring the fenestrated phenotype characteristic of healthy LSECs.

A particularly novel aspect of Liu et al.’s strategy is the ability of nucleic acid spheres to penetrate the liver sinusoidal environment efficiently. The unique size and surface chemistry of these spheres facilitate their selective uptake by LSECs, minimizing off-target effects and potential systemic toxicities. This selective targeting is crucial, considering the liver’s complex cellular heterogeneity and the unique fenestrated morphology that defines LSECs. Effective delivery to these cells has previously been a formidable barrier to therapeutic development.

Their in vitro experiments demonstrated remarkable efficacy in reversing capillarisation markers in cultured LSECs subjected to fibrotic stimuli. Upon treatment with nucleic acid spheres, LSECs exhibited restored fenestrae structures, reduction in basement membrane proteins, and downregulation of endothelial-to-mesenchymal transition markers. These morphological and molecular changes indicate a functional reversion towards a healthy endothelium, an encouraging endpoint rarely achieved by previous interventions.

Moving beyond cell culture, the team validated their approach in murine models of liver fibrosis induced by carbon tetrachloride and bile duct ligation. Systemic administration of nucleic acid spheres resulted in significant improvements in liver histology, marked decreases in collagen deposition, and restored endothelial fenestration as assessed by electron microscopy. Functional assays revealed improved hepatic perfusion and metabolic function, linking the morphological restoration directly to improved liver physiology.

The implications of this study extend well beyond the realm of experimental therapeutics. By showcasing the potential of nucleic acid nano-constructs as precise modulators of endothelial function, Liu et al. open avenues for addressing a wide range of vascular pathologies characterized by endothelial dysfunction. Importantly, these spheres are customizable, suggesting a versatile platform that can be adapted for various disease contexts, including other fibrotic diseases, vascular malformations, and perhaps even tumor vasculature normalization.

Central to the success of this approach is the careful design of the nucleic acid spheres to resist nuclease degradation, a major limitation in nucleic acid therapeutics. The authors employed chemical modifications of nucleotides and a controlled self-assembly process to generate spheres stable under physiological conditions. This stability ensures sustained bioavailability and effective biological activity, overcoming a significant hurdle in the translation of nucleic acid therapies.

Another innovation lies in the interactivity of the nucleic acid spheres with the intracellular machinery of LSECs. Beyond delivering inhibitory RNA sequences, these spheres act as scaffolds, recruiting endogenous regulatory proteins that amplify anti-fibrotic signaling. This multi-layered mode of action potentiates therapeutic outcomes, rendering the approach both robust and adaptable.

The safety profile reported by Liu et al. is equally encouraging. Comprehensive toxicology studies showed no significant off-target immune activation, hepatotoxicity, or systemic adverse effects at therapeutically effective doses. Given the immunogenic risk often associated with nanoparticle-based therapies, this finding paves the way for clinical translation, underscoring the biocompatibility of the nucleic acid sphere platform.

Clinical translation remains a critical future step. The team outlines strategies to scale up nucleic acid sphere production under Good Manufacturing Practice (GMP) conditions and plans to initiate early-phase clinical trials targeting patients with early-stage liver fibrosis. If successful, this therapy could shift the treatment paradigm from symptom management to direct disease modification, a transformative advancement in hepatology.

The impact of Liu et al.’s research resonates within the scientific community and beyond. The use of nucleic acid nanotechnology to orchestrate endothelial cell phenotypes represents an elegant convergence of molecular biology, nanomedicine, and vascular biology. It challenges the traditional confines of drug design and opens the playing field for sophisticated biological interventions tuned at the genomic and proteomic levels.

Moreover, the study highlights the importance of targeted delivery in overcoming biological barriers intrinsic to complex organs such as the liver. By refining cellular specificity and enhancing intracellular trafficking, therapeutic nucleic acid spheres embody the next generation of precision medicine aimed at tackling chronic, otherwise intractable diseases.

As liver fibrosis affects millions worldwide, contributing significantly to morbidity and mortality, the potential societal impact of such a therapy is profound. The promise of restoring healthy liver vasculature and halting fibrotic progression could alleviate burdens on healthcare systems and improve patient quality of life on a global scale.

The methodology and findings of Liu and colleagues also inspire future research directions. The utility of nucleic acid spheres could extend to other endothelial subtypes and fibrotic models, and their modular nature suggests integration with emerging gene editing tools, such as CRISPR-Cas systems, to further refine therapeutic precision.

Finally, these findings underscore the essential role of interdisciplinary collaboration in advancing biomedical innovation. The marriage of nucleic acid chemistry, vascular biology, and nanotechnology exemplified in this study demonstrates how convergent science can unlock new therapeutic frontiers.

In conclusion, the therapeutic deployment of nucleic acid spheres to reverse LSEC capillarisation represents a landmark achievement in liver fibrosis research. Liu et al. have charted a course toward restoring endothelial health and tackling fibrosis at its vascular roots. Their work lays a formidable foundation for translating nanomedicine into clinically viable solutions, poised to transform the future landscape of liver disease treatment.

Subject of Research: Treatment of capillarisation of liver sinusoidal endothelial cells in liver fibrosis using nucleic acid spheres

Article Title: Nucleic acid spheres for treating capillarisation of liver sinusoidal endothelial cells in liver fibrosis

Article References:

Liu, W., Liu, Y., Zhang, L. et al. Nucleic acid spheres for treating capillarisation of liver sinusoidal endothelial cells in liver fibrosis.
Nat Commun 16, 4517 (2025). https://doi.org/10.1038/s41467-025-59885-x

Image Credits: AI Generated