When we interviewed Dr. Mark Carlson about the research he's conducting to develop a liquid bandage, he had some interesting things to say about tissue regeneration. As we all know, humans and other mammals don't 're-grow' skin or other parts of the body, but other creatures can.

"If you get a burn and the skin is burned away, your body cannot regenerate that lost skin. You get a scar instead,” said Carlson. “There are a lot of lower animals, salamanders, for instance, that can regenerate lost body parts. So elsewhere in the animal kingdom, the ability to regenerate does exist. But in the mammals and in humans, the ability to regenerate lost tissue, whether from an injury trauma or a cancer or loss of blood supply, whatever the mechanism of tissue injury is, a human cannot replace, except in a very small number of cases, lost tissue."

So why is that? I'd think we 'advanced' creatures would be the ones that would regenerate tissue, while the 'lower' ones like a salamander would be the ones running around without a leg or tail after losing it. Carlson explains that it might be an evolutionary sort of thing.

"When you get an injury, typically the quickest way to cover that injury up to get it to seal from the environment is by healing with a scar. And this is very important in the wild because you have to have that wound covered quickly or else it’ll get infected. So in nature, a large animal like a wolf or something gets an injury, they heal quickly with scar and that protects them in the short run. Smaller animals like salamanders etc., they’ve maintained this ability to regenerate possibly because the need to get the wound covered right away isn’t as great. This is a theory. This is not fact. But, when people try to piece together why large mammals like us don’t regenerate and small animals can, this is one of the things that commonly comes up is that there were evolutionary pressures on the large animals to recover from a wound as fast as possible, so that they would survive. So somewhere, we’ve lost the ability to regenerate."

The liquid bandage Carlson is hoping to develop is designed to stop bleeding quickly. That could be a life-saver in battlefield situations or other incidents of trauma. But he's thinking about a bigger picture too. He says one of the other research goals of regenerative medicine is to try to figure out the reasons why some creatures (mammals) react to injury with an inflammatory response and others (salamanders) take the path of regeneration. Then maybe someday, humans will 're-grow' tissue and recovery from injury could be more complete.

Additional Links:

St. Elizabeth Regional Medical Center Burn Center

Nature Technology Corporation

A look into the science of skin.

In an article this week in the New York Times, brainpower was correlated with the complexity of nerve synapses. Leading researcher Dr. Grant, who has studied the interconnectedness of neurons, likened this connection to technology; "From the evolutionary perspective, the big brains of vertebrates not only have more synapses and neurons, but each of these synapses is more powerful – vertebrates have big Internets with big computers and invertebrates have small Internets with small computers." The brain has been made analogous to a computer before in order to study evolutionary adaptation. However, the brain was not the organ being studied, rather it was human skin.

Have you ever wondered why we have hair only on the tops of our heads and the rest of our skin is relatively bare? Why does our skin come in so many pigmentations? And why does our skin sweat? Dr. Nina Jablonski kept asking why and attributes these adaptations to the need to keep our brain cool. I first heard Dr. Nina Jablonski speak about her most recent book, Skin: A Natural History, in early 2007. I was absolutely enthralled and two hours raced by as she articulated her fascination with skin. Dr. Jablonski divulged into why our skin appears and acts the way it does from an evolutionary standpoint. Her findings showed that about two million years ago our ancestors were running long distances in Africa under the heat of the equatorial sun. To keep their brains cool, sweat glands became more prominent. This in turn let brain size expand and evolve. In the fossil record, it shows after this increase in brain size, Homo sapiens left Africa to migrate into Mainland China.

Skin:A Natural History

So skin was an evolutionary adaptation to keep our large brains cool and working effectively. Skin color, Dr. Jablonski surmised, was what regulated our body's reaction to the sun and its rays. Dark skin evolved to protect the body of those of our ancestors close to the equator. Those ancestors further away evolved light skin in order to take in Vitamin D in less sunny climates. After her talk about Rosacea, which is a condition of constant blushing found in Eastern European nationalities, I asked Dr. Jablonski why. She told me this might have been attributed to ancestors of light skin being overly bundled and getting over-heated. It might have been an adaptation to release heat and cool the brain from the only exposed skin.

In her lecture, Dr. Jablonski did not stop with touching upon evolutionary adaptations, she also delved into how we associate and identify through our skin. We decorate our skin, clothe it, paint it, tattoo it, scar and pierce it. She elucidated skin as an intimate connection with the world as well as our presentation of individuality. Skin: A Natural History and Dr. Nina Jablonski have gained national recognition. She was even invited as a guest on the Colbert Report to talk about her findings. It is rumored that she is following up Skin with more in-depth research. Until then, this is an outstanding look at a very under-appreciated organ, one that might have made the complex nuances of our brain and its synapses possible.

Watch Dr. Nina Jablonski on The Colbert Report:

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