The four "Yamanaka factors" have been known to induce pluripotency for some time. Forced expression of these four genes has been reported to turn an adult cell into what appears to be a pluripotent stem cell, with all that entails.
However, the report titled: “In Vivo Amelioration of Age-Associated Hallmarks by Partial Reprogramming” illustrates that stem cell differentiation is a continuum. These researchers report that a relatively small dose of these four factors -not enough to induce pluripotency- can prolong lifespan in a mouse model of premature aging, as well as ameliorate age-related impairments in muscle repair in aged mice.
The epigenetic remodeling accomplished by this protocol appears promising, and may help us to rejuvenate older humans. However, we should proceed with caution; these researchers reported that too long of expression of the Yamanaka factors (only 8 days) caused nearly two-thirds of the animals to die, presumably by causing organ failure resulting from too much de-differentiation. While promising, safely striking a balance between rejuvenation and de-differentiation with a similar protocol in humans might be difficult to accomplish.