Expert: Florence M Rollwagen - 8/11/2008

Question
hi, i have noticed from everything i read that scar tissue and old age tissue (cellular and extracelular matrix) seems to be very similar in the cellular make up; disorganized collagen. is it possible that as we age we become more and more a scar?

that is not to say that our body turns 100% scar but it seems like a certain percentage of our bodys original embryotic tissue gradually get replaced with scare like collagen by wear and tear.

ok, so scar is 100% scar, old aged mammals are say 20% scar like randomly distributed tissue throughout out the body.

if you imagine bodily tissue and in the young the cellular tissue are all organised and as one ages a distribution of faulty crosslinked and glysated extracelular matrix is added; a partial scar inbetween organised non scar type cells and E.C.matrix.

Answer
Hi Gene:  Thanks for your question.

What a complex question!  

Let's look at it in two ways:  First, when we are young and growing, collagen is used to give support to various cells and organs.  It is laid down like you would construct a brick wall:  very organized and neat.  I should add here that collagen is not the only ECM that the body uses.  There is also fibronectin, peptidoglycan, elastin, hyaluronic acid and others.

So in the young person, the structure of cells, ECM and tissues is very organized and neat.  

Then things begin to change.  The body's cells, molecules and tissues undergo constant regeneration.  Cells die and are replaced, ECM gets broken down and replaced and tissues are replaced by cells and ECM.  

As a person ages (and by this I mean teenagers and young adults, not necessarily elderly) the body gradually loses its ability to regenerate these tissues and molecules.  Cells die and are not replaced, tissues deteriorate and the ECM gets thinner.

Aging is the cumulative effect of all these processes.  So that when an elderly (80+) person gets injured, it takes a long time to regenerate all these tissues.  

OK, that's the aging part.

As for scar formation, an entirly different process is involved.  When tissue is injured, it releases a variety of inflammatory molecules (inflammation: pain, swelling redness).  These molecules activate the body's defenses and attract inflammatory cells to the area.  The molecules secreted by these cells (mostly white blood cells) activate nearby tissues to grow and replace the injured cells.  

So the cells that replace the injury are not set like bricks in the original wall, they are patches, and don't integrate well with the existing structures.  The ECM protiens are not neatly arranged, but are disorganized, and weaker than the surrounding tissues.  Over time, scars also change and become softer and less rigid, but they are still scars.

So "scar" isn't the word you're looking for, its "disorganized ECM", and yes, the aged person has a higher ratio of ECM to normal tissue than a young person.

I hope this answer has helped you.  Please write back if you have more questions.

FM Rollwagen, PhD