I don't want to get all high school biology on this subject, but I would imagine a mage well versed in the machinations of Restoration could restore and regenerate all the cells in his body. It would take a ridiculous amount of magicka I'm sure.
But take this with a grain of salt because I have no idea how the elements of how the magick in the Elder Scrolls work. But that is my take on it, at least.