Spinal regenerate in animal models.

As a general rule, the more complex the animal, the fewer powers of regeneration they have compared to simpler ones. For example, cnidarians such as the freshwater hydra show spectacular power to regenerate all parts of the body; fish and amphibians can often regenerate fins or limbs; mammals can regenerate the liver and the blood cells (the latter normally being in a constant state of differentiation and destruction). While our bones are capable of healing, say after a crack or a fracture, the process is slow and is not guaranteed to return back to its initial form.

I know humans don't regenerate as other animals can, but I'm asking about other animals just to know that those abilities exist in nature. Zebrafish regenerate spine hard tissues? They want to use many fish models to see how it can be applied to humans with our exceptional ability to augment ourselves. I saw a video that suggested that if humans could regenerate a leg all together as some salamanders can it would take 20 years. Better than nothing. But in the mean time useful remodeling to a youthful state would help a lot.