It seems that when you roll cells back to stem cells, they first roll back to an earlier age, and then to stem cells. So if we can control the process, we can roll the body back to a younger age without converting the cells to stem cells which can then create cancers.
This could be one of the biggest technologies in reversing ageing.
It seems that an excess of PUM2 protein in cells causes a reduction of mitophagy, which eliminates defective mitochondria from cells. This then causes a lack of energy in old age which contributes to many of the problems of ageing. Removing that protein in old animals helps rejuvenate and extend lifespan.