Wade Wilson just might be the human embodiment of the old adage that sometimes you just have to laugh to keep yourself from crying. The Merc with a Mouth has an intimate relationship with comedy but his story is wholly tragic.
An abusive father and a hard-working mom taken too soon by cancer left Wilson on his own before he was old enough to buy a drink. As a hired gun, Wilson traveled the world answering only to his own personal code, killing people he deemed worthy of death. When cancer came knocking at his own doorstep, he entered the Weapon X program, where he acquired a healing factor from none other than Wolverine. His new-found superpower held his cancer at bay but did nothing to heal his horrifyingly scarred body.
After a string of failed relationships: personal, terrestrial, and ethereal (Wilson has at times had a tenuous romantic affiliation with Death herself) he donned the costume and became the mercenary we all know and love, he became Deadpool.
Deadpool's life is one of almost constant suffering, made more bizarre by the fact that he seems to be aware of his station in life as a fictional character on page and screen. Despite what appears to be his best efforts, he cannot die. His healing factor, becoming more or less effective depending on the arc in question, keeps him inches from death, despite trauma so severe most ordinary folks would be begging for sweet release.
While Deadpool's abilities are the result of creative fiction, regeneration of damaged tissues has been the pursuit of the medical establishment for decades. The ability to reattach a severed head or grow a new heart after yours has been torn from your chest by Ajax is likely something we'll never achieve, but maybe we can meet somewhere in the middle.
The story so far
You might be surprised to learn that the regeneration of tissues isn't entirely outside of your ability. Your own healing factor is, admittedly, less awesome than Deadpool's or Wolverine's but it's there. It's just that you have less opportunity to use it.
Obviously, everyone has some ability to heal, otherwise we'd all meet our end the first time we got a nosebleed or sliced our fingers on a sheet of particularly aggressive paper. Assuming wounds aren't too deep, your body is actually quite good at stitching your casing back together. A cursory inventory of your meat sack will probably reveal more than few scars, all evidence of a time your body sighed, wiped its brow, and cleaned up the messes of your clumsiness or misfortune.
Your immune system is also pretty good at protecting you from microscopic foreign invaders. The amount of bacteria present on the phone or computer your reading this on is so staggering it's shocking you don't bathe in bleach.
But none of that is as impressive as regrowing appendages. It turns out, however, you can do that too. A little. It's been pretty well documented, though poorly advertised, that human beings are capable of regrowing fingers and toes, to a degree. A finger amputated at the distal phalanx (the outermost knuckle) is capable of regenerating from almost nothing.
The earliest documented case of this (though surely it happened countless times before) was in 1932 when Dr. G.S., a house surgeon at the Montreal General Hospital pricked his fingertip with a safety pin and it became infected (because ordinary people are super lame). The infection eroded the bone and necessitated removal. The cavity was cleaned and packed and the infection cleared. Over the next several weeks, the bone regenerated, and within six weeks the finger was fully healed, including fingernail.
The same can be said of toes, though mileage varies. It appears to require the root of the nail to be present. Stem cells present in the epithelium under the nail assist in regeneration. And in some cases, fingerprints do not return, perfect for a life of mercenary crime behind a mask (it should be noted that SYFY does not recommend the amputation of fingertips in pursuit of nefarious deeds, getting a normal job seems way easier).
Bring on the science
If there's one thing human beings are good at, it's being dissatisfied with the status quo. Enough is never enough. We weren't happy living in trees or being hunted by tigers with dental problems, and we aren't happy just regrowing toes.
We've known for some time that regeneration is possible within the animal kingdom. Many animals are capable of losing and re-growing complex structures, but human beings aren't one of them. New research, however, may have unlocked the secret to that ability, locked within our own dormant DNA.
New research has identified a gene, p21, that is seemingly responsible for shutting off our healing factor. When the gene is turned off in lab mice, they're able to regrow large puncture wounds and severed appendages quickly. Though it comes with a downside. P21 is apparently a safety measure against another gene, p53, which codes for ongoing cellular division. Research suggests that, unchecked, p53 might affect runaway cell growth, resulting in cancers.
In a twist of fate, the likes of which would make Deadpool laugh fit to cry, releasing our dormant regeneration abilities might spike instances of cancer, a complete opposite of his experiences in the Weapon X program. Though, in the lab mice that were tested, there was no surge in cancerous tissues once p21 was set free. More research is needed to determine the long-term effects.
While lab mice are almost always our animal of choice, when it comes to unlocking the key to regeneration, there's no better subject for study than the axolotl. You may recognize it as the inspiration for Mudkip, the adorable pokemon, but in real life, it's the only vertebrate that retains its regeneration abilities to adulthood.
Many invertebrates have the ability to regenerate. Every kid knows that if you cut an earthworm in two, you end up with two worms. And frogs can regrow limbs while in their tadpole stage. But Axolotl's stand alone in the vertebrate world when it comes to regrowing lost tissues throughout their lives.
When an axolotl loses an arm, rather than developing scar tissue, it rapidly cuts off blood flow, then develops a wound epidermis, which gives way to a blastema containing all of the requisite tissues needed for a new limb. These tissues continue to develop until a new limb is formed. Though there are limits. In some studies, after an axolotl's limb was severed a number of times, it lost the ability to reform.
When comparing the axolotl to human tissues, it becomes clear that it retains a primitive ability to grow new tissues as if it were in the womb, while humans develop scar tissues. Initiating scar tissue in the axolotl prevents its ability to regrow limbs, likewise, reversing the process may allow human beings to regrow lost limbs, but the research is still ongoing.
It seems, somewhere in our DNA, lies the ability to grow and regrow complex tissues and, while we may not have the benefit of horrible tragedies and government experiments to unlock our healing factors, science and humble salamanders may light the way to our comic book future.