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Remember the time you fell off your bike
or bumped your head on a sharp corner?
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Childhood injuries are things
we'd often like to forget,
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but our bodies often carry the memories
in the form of scars.
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So what are these unwanted souvenirs
and why do we keep them for so long
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after that unintended vacation
to the emergency room?
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The most common place we see scars
are on our skin,
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a patch that looks slightly different
from the normal skin around it.
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Often, this is considered
an unfortunate disfigurement,
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while other times, deliberate
scarification has been used
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in both traditional and modern cultures,
to mark a rite of passage
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or simply for aesthetic decoration.
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But the difference isn't only cosmetic.
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When we look at healthy skin tissue
under a microscope,
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we see the cells that perform
various functions
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connected by an extracellular
matrix, or ECM.
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This is composed of structural proteins,
like collagen,
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secreted by specialized fibroblast cells.
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Well-arranged ECM allows for
transportation of nutrients,
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cell-to-cell communication,
and cell adhesion.
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But when a deep wound occurs,
this arrangement is disrupted.
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During the process of wound healing,
collagen is redeposited at the wound site,
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but instead of the basket-weave formation
found in healthy tissue,
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the new ECM is aligned
in a single direction,
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impeding inter-cell processes,
and reducing durability and elasticity.
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To make matters worse,
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the healed tissue contains
a higher proportion of ECM than before,
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reducing its overall function.
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In the skin, the overabundance of collagen
interferes with its original functions,
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like producing sweat,
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controlling body temperature
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and even growing hair.
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The scar tissue is fragile, sensitive
to changes in temperature and sensation,
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and should be kept in moist environments
to maximize healing.
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This presence of excessive
fibrous connective tissue in an organ
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is known as fibrosis,
and if that term sounds familiar,
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it's because our skin is not the only
organ vulnerable to scarring.
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Cystic fibrosis is a genetic disorder
that causes scarring of the pancreas,
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while pulmonary fibrosis
is a scarring of the lungs,
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resulting in shortness of breath.
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Scarring of the heart and the buildup
of ECM following a heart attack
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can inhibit its beating,
leading to further heart problems.
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What's common to all these conditions
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is that although it retains some
of the original functions,
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the scar tissue formed after a wound
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is inferior to the native tissue
it replaces.
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However, there is hope.
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Medical researchers are now studying
what causes fibroblast cells
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to secrete excessive amounts of collagen
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and how we can recruit
the body's other cells
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in regenerating and repopulating
the damaged tissue.
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By learning how to better control wound
healing and the formation of scar tissue,
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we can utilize
the multi-billion-dollar budgets
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currently used to address
the aftermath of wounding
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in a much more efficient manner,
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and help millions of people live better
and healthier lives.
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But until then, at least some of our scars
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can help us remember to avoid
the sorts of things that cause them.