(selected excerpts below)To evaluate the impact of CQ on senescence, we treated human mesenchymal stem cells (hMSCs), multipotent stem cells present in most tissues, with the drug...We found that CQ promoted cell self-renewal at lower concentrations (0.2–5 μmol/L), but inhibited cell proliferation at higher concentrations (20 μmol/L or above) (Fig. 1B). Specifically, treatment with 1 μmol/L CQ decreased the percentage of SA-β-gal-positive cells and increased the number of Ki67-positive cells in WS hMSCs (Fig. 1C and 1D)...To further examine the systemic effects of CQ in vivo, we treated 24-month-old Sprague Dawley (SD) male rats with CQ twice a week for 5 months at a low dose of 0.1 mg/kg orally by water to avoid potential side effects (Fig. 1A). Low-dose CQ administration extended the lifespan of rats by approximately 6% in terms of median longevity and by about 13% in terms of maximum longevity (Fig. 1F). CQ-treated rats also tended to have decreased serum TNF-α levels and reduced the numbers of circulating white blood cells (WBC) and neutrophils (NEU) in old rats (Figs. 1G–J and S1B), suggestive of attenuated chronic inflammation.