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Remember the time you fell off your bike[br]or bumped your head on a sharp corner?

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Childhood injuries are things[br]we'd often like to forget,

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but our bodies often carry the memories[br]in the form of scars.

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So what are these unwanted souvenirs[br]and why do we keep them for so long

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after that unintended vacation[br]to the emergency room?

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The most common place we see scars[br]are on our skin,

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a patch that looks slightly different[br]from the normal skin around it.

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Often, this is considered[br]an unfortunate disfigurement,

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while other times, deliberate[br]scarification has been used

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in both traditional and modern cultures,[br]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[br]under a microscope,

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we see the cells that perform[br]various functions

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connected by an extracellular[br]matrix, or ECM.

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This is composed of structural proteins,[br]like collagen,

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secreted by specialized fibroblast cells.

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Well-arranged ECM allows for[br]transportation of nutrients,

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cell-to-cell communication,[br]and cell adhesion.

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But when a deep wound occurs,[br]this arrangement is disrupted.

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During the process of wound healing,[br]collagen is redeposited at the wound site,

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but instead of the basket-weave formation[br]found in healthy tissue,

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the new ECM is aligned[br]in a single direction,

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impeding inter-cell processes,[br]and reducing durability and elasticity.

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To make matters worse,

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the healed tissue contains[br]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[br]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[br]to changes in temperature and sensation,

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and should be kept in moist environments[br]to maximize healing.

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This presence of excessive[br]fibrous connective tissue in an organ

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is known as fibrosis,[br]and if that term sounds familiar,

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it's because our skin is not the only[br]organ vulnerable to scarring.

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Cystic fibrosis is a genetic disorder[br]that causes scarring of the pancreas,

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while pulmonary fibrosis[br]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[br]of ECM following a heart attack

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can inhibit its beating,[br]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[br]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[br]it replaces.

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However, there is hope.

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Medical researchers are now studying[br]what causes fibroblast cells

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to secrete excessive amounts of collagen

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and how we can recruit[br]the body's other cells

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in regenerating and repopulating[br]the damaged tissue.

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By learning how to better control wound[br]healing and the formation of scar tissue,

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we can utilize[br]the multi-billion-dollar budgets

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currently used to address[br]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[br]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[br]the sorts of things that cause them.