Board Thread:Naruto Discussions/@comment-25369463-20140916215554/@comment-26302001-20140916230745

Kabuto did say he was the closest to the Sage when fighting Itachi so he may have already integrated Hashi's cells, but maybe like Danzo he can't control it so he doesn't use it. He also only used Hashi cells to repair Sasuke's heart since it was fatally damaged.. Sasuke definitely has Hashi's DNA in him, not to mention Hashirama gave him his Chakra too.