Here is what I understood from it:
1) The wording makes it really unclear...
2) Soul Fusing Ability with Living
3) Kaien's shinigami power
I really dont think we can know for sure until we understand what is that other ball-head in that jar next to Aaroniro. Also, what experiments does Aizen do? From what i understood all he does is use the hogyoku...a different espada does experiments but i doubt he has anything to do with Aaroniiro.