Yet in DMC2 it is supposed to be years from DMC1 but dante is only a little older and if he goes demon form which he does he is practically unaging.So surely every time he dt's he revitalises his cells.
DMC2 was originally supposed to be set closer to DMC1, but then it became embarrassing enough that they pushed its story in far future so they don't have to deal with it so soon... or ever, hence why Dante doesn't look so old.
Gameplay-wise, dt indeed makes Dante heal, so one can take it as really revitalizing his cells story-wise as well. However, Dante spends more time in human form, which I guess does a lousier job or something.