When an octopus is injured and loses one of its limbs, it will grow back after several months. When a starfish loses an appendage, not only will the starfish grow a new arm, but the severed arm will grow a new starfish! Even among vertebrates, regeneration is not unknown – salamanders can regrow lost body parts. Yet when a human loses an appendage, it is forever lost. What do these animals do that we don’t? Many scientists believe that the capacity for regeneration is lying dormant within our biology, and we may soon be able to activate it. Most complex organisms including humans contain a huge number of different types of cells that each perform a specific function within the body. For the most part, these cells cannot do anything else; a brain cell can never become a white blood cell, or vice versa. But in addition to these specialized types of cells, we have stem cells – “wild card” cells that have no specific function of their own, but are able to become whatever type of cell the body needs. Stem cells show great promise in treating a wide range of diseases, rejuvenating our organs and tissues, and replacing entire body parts.
For several decades, the organ transplant process has been horrendously inefficient. The standard procedure has been for patients to beg their friends and family to donate an organ…if they can even find a compatible donor. If not, they enter their name onto a hopelessly long organ wait list, where they may die before finding a suitable replacement. If they are lucky enough to receive a transplant, patients will spend the rest of their lives taking a strict regimen of drugs to prevent their body from “rejecting” the organ (i.e. viewing it as a hostile invader to be eliminated).
Regenerative medicine will soon transform this process. People will be able to grow their own replacement organs in a lab, and since the new organ is their own, there will be no worries about their body rejecting it. Substantial progress has already been made in many areas. In 2006, doctors first created a human bladder from scratch. They extracted a few bladder cells from patients, and pasted them onto a three-dimensional mold shaped like a bladder. To their delight, the cells quickly grew into a new, fully-functional bladder, which they then transplanted into the patient. In 2010, doctors first performed a similar procedure using stem cells instead of bladder cells. Regenerative medicine is quickly becoming the standard for treating serious bladder diseases. Clinical trials are underway for similar procedures for other organs including the heart, although these procedures are at least a decade from being used in hospitals. In June 2010, scientists successfully grew a liver in the laboratory for the first time.
But replacing entire organs is not the only promising use for regenerative medicine. There is no fundamental reason why tissues and organs that have been badly damaged – by disease, injury, or natural wear and tear – cannot gradually be rejuvenated by replacing the damaged cells with healthy stem cells, allowing our body parts to remain in excellent condition throughout our lives. This has ramifications for slowing the human aging process, and possibly even reversing it. When people are able to replace their organs with newer versions of themselves, “old age” will need not be regarded as a time of enfeeblement and illness.
Our stem cells are essentially a blank slate, which can become whatever type of cell we want them to become. Their potential applications to regenerative medicine are practically limitless, as practically every major non-infectious, non-genetic disease results in some form of cellular damage. Regenerative medicine treatment will be a relatively slow and non-disruptive transformation – we will gradually see more and more of these therapies over the next few decades – and is not a cure-all by any means. However, it is one of the most promising new treatments (along with genomics) which will eventually radically extend the human lifespan.
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