Researchers are spending a fair amount of time on understanding why regeneration in mammals differs from - and is much worse than - regeneration in lower animals like salamanders. A salamander can grow back a limb any time it needs to, a mouse or a human not so much. But we can do the full regeneration trick to a far lesser degree, as humans and mice can both regrow the tip of a finger or toe when very young or very lucky, for example. You might also recall the MRL mice, an engineered species that can regenerate much more effectively than is normal for most mice.
One of the questions that researchers aim to answer is whether the mechanisms for salamander-like regeneration lie buried in mammalian biology, perhaps turned off for reasons involving cancer suppression. If they are there, perhaps they can be restored via drugs or genetic engineering for long enough to regrow major damage to limbs and organs. That's all speculative at this point, and looking more so after this latest research publication:
Tissue-specific adult stem cells are responsible for the ability of mammals to re-grow the tips of fingers or toes lost to trauma or surgery, say researchers at the Stanford University School of Medicine. The finding discredits a popular theory that holds that previously specialized cells regress, or dedifferentiate, in response to injury to form a pluripotent repair structure called a blastema.
"We've shown conclusively that what was thought to be a blastema is instead simply resident stem cells that are already committed to become specific tissue types," said Irving Weissman, MD, director of Stanford's Institute for Stem Cell Biology and Regenerative Medicine. "The controversy about limb regeneration in mammals should be over."
If you want to take the glass half full view, this might mean that it will be a shorter path to pushing these stem cells into doing more with less - rather than the alternative and longer path of trying to recreate salamander-like blastema behavior in mammals. But it's anyone's guess as to how much regeneration these cells are capable of if manipulated; no doubt less than we'd all like.