It was mentioned some sort of experiment or samples led to Kakashi and Rin being cornered. Now the Mist nin wants Rin's body. When I hear experiment the first name comes to mind is Orochimaru. We know Yamato was one of the test subjects Oro had injecting Harashima's DNA. Also Tobi tends to curse Oro's name. Could Rin be one of Oro's test subjects of his various projects?