WEBVTT

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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.