The study tested whether genetically engineered senescence-resistant mesenchymal progenitor cells (SRCs) could slow or reverse aging in primates. By enhancing the activity of the longevity-associated gene FOXO3, the researchers created stem cells more resilient to stress and senescence.
This reversed ageing across a broad series of markers, including the brain, skin, bones, internal organs, and reproductive system.
The study used cynomolgus macaques aged 19–23 years, which they said is equivalent to 57–69 years in humans. I don't know if you can directly scale up the improvements to "human years", but if you could, it seems this would be the same as reversing human aging by about a decade for people in their 50s and 60s.
Senescence-resistant human mesenchymal progenitor cells counter aging in primates