Research Paper Volume 8, Issue 7 pp 1294—1315

Aging of mice is associated with p16(Ink4a)- and β-galactosidase-positive macrophage accumulation that can be induced in young mice by senescent cells

Brandon M. Hall1, , Vitaly Balan1, , Anatoli S. Gleiberman1, , Evguenia Strom1, , Peter Krasnov1, , Lauren P. Virtuoso1, , Elena Rydkina1, , Slavoljub Vujcic1, , Karina Balan1, , Ilya Gitlin2, , Katerina Leonova2, , Alexander Polinsky1, , Olga B. Chernova1, , Andrei V. Gudkov1,2, ,

  • 1 Everon Biosciences, Inc., Buffalo, NY 14203, USA
  • 2 Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA

Received: May 23, 2016       Accepted: June 28, 2016       Published: July 6, 2016      

https://doi.org/10.18632/aging.100991
How to Cite

Copyright: © 2016 Hall et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Senescent cells (SCs) have been considered a source of age-related chronic sterile systemic inflammation and a target for anti-aging therapies. To understand mechanisms controlling the amount of SCs, we analyzed the phenomenon of rapid clearance of human senescent fibroblasts implanted into SCID mice, which can be overcome when SCs were embedded into alginate beads preventing them from immunocyte attack. To identify putative SC killers, we analyzed the content of cell populations in lavage and capsules formed around the SC-containing beads. One of the major cell types attracted by secretory factors of SCs was a subpopulation of macrophages characterized by p16(Ink4a) gene expression and β-galactosidase activity at pH6.0 (β-galpH6), thus resembling SCs. Consistently, mice with p16(Ink4a) promoter-driven luciferase, developed bright luminescence of their peritoneal cavity within two weeks following implantation of SCs embedded in alginate beads. p16(Ink4a)/β-galpH6-expressing cells had surface biomarkers of macrophages F4/80 and were sensitive to liposomal clodronate used for the selective killing of cells capable of phagocytosis. At the same time, clodronate failed to kill bona fide SCs generated in vitro by genotoxic stress. Old mice with elevated proportion of p16(Ink4a)/β-galpH6-positive cells in their tissues demonstrated reduction of both following systemic clodronate treatment, indicating that a significant proportion of cells previously considered to be SCs are actually a subclass of macrophages. These observations point at a significant role of p16(Ink4a)/β-galpH6-positive macrophages in aging, which previously was attributed solely to SCs. They require re-interpretation of the mechanisms underlying rejuvenating effects following eradication of p16(Ink4a)/β-galpH6-positive cells and reconsideration of potential cellular target for anti-aging treatment.

Abbreviations

SC: senescent cell; SASP: senescence-associated secretory phenotype; β-galpH6: β-galactosidase activity detectable at pH6.0, a marker of SCs; FACS: fluorescence-activated cell sorting; GLuc: Gaussia princeps luciferase; i.p.: intraperitoneal; mAdMSC: mouse adipose-derived mesenchymal stromal cells; NDF: neonatal dermal fibroblasts; NK: natural killer cells; PGK: phosphoglycerate kinase; SCID: severe combined immune deficiency.