Sometimes. "Aging" is a remarkably complex set of processes and still in its very early stages of being properly understood. Some causes of aging, when treated and addressed, really do "reverse" apparent age — in reality, this is addressing flaws in replication process and moving that function back towards normal, but from the outside it does appear that the new tissue is functionally "younger" than the old.

One special case (telomerase deficiency) induced and exercised in mice: https://www.nih.gov/news-events/nih-research-matters/aspects-aging-might-be-reversed

Everything in your body (almost) is continuously replacing itself at various speeds. If there's a problem that's causing replicated cells to behave as if they're more degraded ("older") than they otherwise would be, then treating that and having the next replacement round be more functional than its precessor is effectively "reducing age" as an apparent and functional measure.

If the source cells have accumulated replication errors or otherwise been intrinsically "damaged," however, you need much more intensive and hitherto "exotic" treatments to make all the trillions of pieces of "future human" to look and act younger than "current human," and "slowing aging" is a lot more readily attainable in those circumstances.