It has been previously shown in several studies that OSKM induction (where O stands for Oct4) lowers epigenetic age gradually
For example, this fact has been demonstrated in human fibroblasts in the following preprint:https://www.biorxiv.org/content/early/2018/03/31/292680
Having discovered this gradual property of epigenetic reprogramming, we can now be cautiously optimistic that we will manage to find a safe therapeutic window (such as marked by a yellow box in the graph on the right) - i.e. a period of safe epigenetic rollback when the methylation profile of a cell has been returned to a younger state but the cell has not lost its functional characteristics (i.e. a skin cell remains a skin cell rather than gets dedifferentiated into a pluripotent cell).