Board Thread:Theories and Speculation/@comment-1512913-20150221101637/@comment-25549954-20150307105312

Kabuto experimented on Hashirama cell and he injected those cells to heal Sasuke, Hashirama also gave him chakra and a jutsu to counter Madara's Senjutsu but it rebounded on himself probably. I don't think Sasuke's Rinnegan always remain activated he could probably switch it with normal Uchiha black just like his Sharingan, Nagato couldn't deactivate it because it wasn't his eyes and Madara could switch it with his Mangekyou. I think he got his Rinnegan because of Hashirama's chakra and his Indra chakra got mixed. And that is why he was probably able to meet the Sage to receive tattoo gifts. So I think his Rinnegan is permanent only the tattoo disappeared, but in The Last and Epilogue his Rinnegan was not shown for whatever reason.