recent Nature is aging The study evaluated the efficacy of a senolytic therapy based on chimeric antigen receptor (CAR) T-cells. In this therapy, senolytic CAR T-cells target urokinase plasminogen activator receptor (uPAR)-positive cells, which accumulate during aging.
Study: Prophylactic and chronic efficacy of senolytic cART cells against age-related metabolic dysfunction. Image credit: Juan Gaertner / Shutterstock.com
Cellular senescence is an irreversible cell cycle arrest induced in response to stress. Under stressful conditions, matrix remodeling enzymes and pro-inflammatory cytokines are produced, referred to as the senescence-associated secretory phenotype (SASP).
In young individuals with physiologic conditions such as tumor suppression and wound healing, SASP promotes the recruitment of immune cells, which facilitates tissue repair and clearance of senescent cells. In elderly people, senescent cells accumulate due to reduced immune system function and high tissue damage.
To date, most senolytic therapies have included small-molecule drugs that require repeated administration and poorly target the affected area. In comparison, CAR T-cells require a single target antigen that is differentially expressed compared to normal tissue. Furthermore, CAR T-cells are single-administered ‘living drugs’, which persist for many years and mediate their effects.
About the study
Previously, CAR T-cells have been shown to target the cell-surface protein uPAR and effectively deplete senescent cells. The current study examines whether CAR T-cells effectively and safely remove senescent cells in aged mice, thereby regulating health span.
Mice of both sexes, aged 8–12 weeks and 18–20 months, were included in the study. They were kept in group housing and pathogen free conditions.
A 12-h light/dark cycle was used and temperature and humidity conditions were standard. Aging mice consumed a normal diet, whereas a subset of mice consumed a high-fat diet (HFD).
For flow cytometry analysis, livers were isolated and filtered, followed by exclusion of red blood cells. Single-cell ribonucleic acid (RNA) sequencing was performed, followed by expansion, isolation, and transfer of mouse T-cells. Complete blood counts were noted and postmortem analysis of multiple organs was performed.
Senolytic cell therapies have been shown to reduce signs of physiological aging, including metabolic dysfunction. To this end, the proportion of uPAR-positive cells often increases with age; Therefore, both immune and non-immune uPAR-positive cells likely facilitate the burden of senescence in aged tissues.
AImmunohistochemical staining of liver, adipose tissue, muscle, and pancreas of young (3 months of age) or old (20 months of age) mice (n = 3 per age). b–Mr, Single-cell analysis of uPAR expression and senescence. uPAR-positive and uPAR-negative cells were sorted from the liver, adipose tissue, and pancreas of 20-month-old mice and subjected to single-cell RNA-seq by the 10x Chromium protocol (n = sequences from four mice with two females combined in one replicate and two males were combined in another replicate). bUniform manifold approximation and projection (UMAP) visualization of liver cell types. cUMAP visualization of adipose tissue cell types. dUMAP visualization of pancreatic cell types. eUMAP visualization of hepatic uPAR-negative and uPAR-positive cell types. fUMAP visualization of adipose uPAR-negative and uPAR-positive cell types. gUMAP visualization of pancreatic uPAR-negative and uPAR-positive cell types. h,j,lUMAP visualization with senescence signature scores24 In each cell indicated by the color scale. i,k,MrQuantification of the proportion of uPAR-positive and uPAR-negative cells contributes to their respective senescence signatures. h,ishow live; j,kfat banana; l,Mr, pancreas. Results are from an independent experiment (A–Mr) DC, dendritic cell; NK, natural killer; pDC, plasmacytoid dendritic cells; ASPC, Adipose Progenitor and Stem Cell.
The efficacy of uPAR CAR T-cells in removing uPAR-positive senescent cells was also highlighted. To this end, uPAR CAR T-cell efficacy was not associated with changes in tissue pathology or renal and hepatic parameters in aged mice.
uPAR CAR T-cell activity was found to be associated with metabolic fitness and enhanced glucose homeostasis in normal aging and HFD-fed mice. Importantly, no toxicity was observed after administration of uPAR CAR T-cells at the recommended doses.
Another interesting observation was the potential for uPAR CAR T-cells to act prophylactically to mitigate diet-related and age-related metabolic decline. Moreover, uPAR CAR T-cells have long-lasting effects in senolytic systems based on small molecules. After a single administration, these cells impaired HFD-associated or age-induced metabolic syndrome in rats administered HFD or treated during puberty.
In terms of glucose tolerance, senolytic studies have identified the removal of senescent pancreatic beta cells. However, immune cell senescence may also play a role.
Elimination of macrophages with senescent properties has been suggested to reduce tissue loss in mice. This is consistent with study observations, in which uPAR-expressing macrophages co-express transcriptional signatures associated with senescence and senescence-associated β-galactosidase (SA-β-gal).
The mechanism of action of small molecules is often poorly understood; However, senolytic CAR T-cells have a clear underlying mechanism due to the expression of specific surface antigens. This approach is associated with many advantages over vaccines or small-molecule approaches, as cellular therapies control persistence through different CAR designs and are equipped with specific safety switches.
In the future, cellular therapies may target these antigens to treat different phenotypes. The effect and durability of uPAR-targeted CAR T-cells after a single administration are good for senolytic CAR T-cell approaches to treat chronic pathologies.
- Amor, C., Fernandez-Maestre, I., Chowdhury, S., etc (2024) Prophylactic and chronic efficacy of senolytic CAR T cells against age-related metabolic dysfunction. Nature is aging; 1-14. doi:10.1038/s43587-023-00560-5