Board Thread:Naruto Discussions/@comment-25369463-20140916215554/@comment-4912646-20140916225605

He said he used his studies of Hashirama's DNA to heal Sasuke, but didn't say whether he (and now Sasuke) actually has Hashirama's DNA in his body. Just like how he said his own enhanced regeneration is based on studying Karin, but didn't say whether it's a result of integrating her DNA.

Thinking about it, if Kabuto actually does have Hashirama cells, he essentially has four times the regeneration power (his own medical ninjutsu, Orochimaru's white snake power, Karin's regeneration, and now Hashirama's).