Modern medicine clutches at a number of dreams. Some, like developing an AIDS vaccine, can seem tantalizingly close.
Others, like curing cancer, have frustrated so many minds for so many years that we’ve learned to temper our expectations.
Then there’s regeneration.
A future in which humans regrow lost or diseased body parts feels like a mirage. But why? After all, many species can accomplish the task with ease.
A decapitated flatworm, for example, will grow a new head, replete with a new brain. For the first week of their lives, tadpoles can replace lost tails.
And the axolotl, or Mexican salamander, has the ability to regenerate everything from its limbs and tail to its spinal cord and skin, all without any evidence of scarring.
Even some mammals have limited regenerative abilities: every year, reindeer regrow their shredded antlers. And, in some circumstances, young rats that lose a leg can grow it back.
Humans have a sliver of regenerative capacity, too. If a child experiences a neat slice through the end of his fingertip, that tip will grow back — although the ability disappears sometime around the age of 12.
The Greek legend of Prometheus, the god who was cursed to have an eagle peck out his liver each day, only to grow it back overnight, actually contains a grain of physiological truth.
If you were to lose part of your liver, it would, in fact, repair itself. With the exception of our skin, it’s the only human organ that can do this.
Regenerating a small body part under special circumstances is one thing, but what if we could regrow entire lost limbs?
What if we could signal to our bodies to regrow damaged retinal tissue — or even to regrow an entire eye? Michael Levin doesn’t think this is an outlandish fantasy.
In fact, he thinks he may be on the path to figuring out how to do precisely that.
Levin is director of Tufts University’s Center for Regenerative and Developmental Biology in Medford, near Boston.
He’s a 43-year-old Russian émigré who looks like a geeked-out Gen Xer: His smooth hair is parted far to the side; a neat geometric beard frames his face; and he’s most comfortable in a college uniform of T-shirts over long sleeves.
Levin thinks that the key to regeneration — the key to pattern, to shape — may be found in the electrical signals that are transmitted among all our cells, much like the ones and zeros that zip around in a computer’s hard drive.
Manipulating these signals has already allowed Levin to produce results more suited to an X-Men comic than a scientific journal, including the creation of four-headed flatworms.
Over the course of the next year, he will begin experiments that could make human regeneration a reality.
Levin’s work is little known, perhaps because so many scientists believe that the key to human regeneration — if such a thing exists — lies in studies of genetics and stem cells.
Such studies have produced incredible results: a patient’s windpipe, repaired in a lab; a segment of functional bladder, fashioned on an artificial lattice.
These achievements offer the hope that a patient will one day be able to grow a new organ from her own cells, instead of waiting for someone else misfortune to be her good luck.
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