The discussion centers on the feasibility of injecting mouse cells, such as liver or heart cells, into humans without causing harm. Xenotransplantation is highlighted, noting that while some animal organs, like pig heart valves, can be used after chemical treatment, there are significant challenges with infection rates and immune rejection. The FDA has banned non-human primate transplants due to cross-species infection risks. The immune system typically rejects foreign cells within 72 hours, and using immunosuppressants may not be viable due to the high risk of secondary infections. The conversation also touches on the potential for regenerative medicine, referencing research on "miracle mice" that can regenerate limbs and organs. These findings suggest that certain genes may enable regeneration, but the applicability to human medicine remains uncertain, especially concerning brain regeneration. Overall, while there is scientific interest in the potential of animal cells for human treatment, significant barriers related to immune response and safety persist.