2 replies to this topic

[Tetracyclone]

I think many of us will be interested in Dr. Young's explanation of scar tissue and the cord.


I realize that I may be a loner amongst scientists when it comes to the use of the word "scar" referring to the aftermath of spinal cord injury. Over the years, I have spoken up at multiple meetings, questioning speakers who use the word "scar" or "glial scar" with respect to spinal cord injury. I didn't use to be militant on this subject until I saw a talk given by Carlos Lima in 2003. He was presenting his work that transplanted olfactory mucosal into the spinal cord of patients and he said that the surgical team removed a "block" of scar tissue from the spinal cord so that they could stuff nasal mucosa into the hole. He showed pictures of the removed tissues and there were axons in the tissue.

There is no rational or evidential basis for removing scar tissue from the spinal cord. It is not rational to remove "scar" because the act of removing scar will simply create more scar. There is no evidence that a majority of people with spinal cord injury have a "scar". This is where the discussion usually breaks down. What people are calling "scar" is simply accumulation of glial cells, i.e. astrocytes that grow at injury sites. This is properly called gliosis. To me, the word scar refers to a collagenous tissue formed by fibroblasts, skin cells, that knit damaged tissues together. Fibroblasts are present in most parts of the body. Fibrous and collagenous scars form when we cut skin, liver, heart, lung, and many other organs because these organs have fibroblasts that invade into the injury scar and form scars.

It is true that if you cut the spinal cord and do not close the dura, fibroblasts do invade into the spinal cord and a fibrous scar may form, lined on the CNS side by astrocytes. However, the vast majority of spinal cord injuries do not involve any penetration of the spinal cord. Displaced bone or disc compresses or contuses the spinal cord, usually without penetrating the dura, a very tough membrane that surrounds and protects the spinal cord. While some fibroblasts are present in the arachnoid membranes outside the spinal cord, fibroblasts are usually excluded from the spinal cord. A contused spinal cord seldom has any collagen within the injury site.

The vast majority of spinal cord injuries do not involve a penetrating wound of the spinal cord. Normally, no fibroblast resides in the spinal cord and they are carefully excluded by astrocytes, whose job it is to wall off the central nervous system including the spinal cord from peripheral tissues. Astrocytes are responsible for creating the blood brain barrier and line all boundaries between the central nervous system and peripheral tissues. Gliosis is part of the natural repair of the injured spinal cord. In fact, many studies have shown that if you stop gliosis, it is damaging to the spinal cord and the blood brain barrier does not reform.

Investigators who injure the spinal cord by using a knife, scissors, vibrating probes, or laser beams to cut the spinal cord may of course see a scar at the injury site. At least one study [1] has shown that if the investigator carefully sewed the dura close and prevented invasion of fibroblasts into the injury site, there is no scar formation. I don't question the presence of scar tissues in such injury models. However, if the spinal cord is injured by compression, contusion, or ischemia, there is seldom any collagenous scar tissue in the spinal cord. Stephen Davies uses hemisection or transection model of spinal cord ijnjury, where he cuts the spinal cord. Of course he thinks that scar is important because his model has scar.

There is also an open question whether "scar" tissues prevent axonal regeneration. For example, in recent studies by Kai Liu, et al. [2] showing rivers of corticospinal tract axons growing across a cut injury site after reducing PTEN expression, he made no attempt to remove the scar tissues and yet many axons regenerated across the injury site. Scientists such as Martin Schwab did not remove scar when he used Nogo blockers to stimulate regeneration [3]. Likewise, scientists who used chondroitinase to enhance regeneration the spinal cord did not remove "scar". For example, Yick, et al. [4] was able to regenerate 40% of the rubrospinal tract in rat spinal cord with chondroitinase and lithium.

Some scientist say that astrocytes secrete chondroitin-6-sulfate proteoglycan (CSPG) which stops axonal growth. While it is true that CSPG does stop axonal growth, CSPG is not "scar". It is a glycoprotein that is present in the extracellular space. While CSPG does stop axonal growth, this is its purpose, i.e. it is present at the edges of the nervous system and its "job" is to channel axons so that they grow within the central nervous system and do not sprout like hair from the surface of the brain and spinal cord. One can have astrocytes without CSPG. In fact, Stephen Davies himself showed that certain types of astrocytes are beneficial for axonal regeneration in spinal cord injury.

Some people may dismiss my argument as just semantics. I would agree with them if I have not seen so many patients with spinal cord injury coming to me and to this web site saying that "scar" has to be removed from the spinal cord before regeneration can occur. I would agree if there were not people like Carlos Lima whose surgical team actually cut out "scar" from the spinal cord. I would agree if the word "scar" were not used so indiscriminately as to refer to any kind of gliosis, including a company that actually set as its therapeutic goal the elimination of gliosis from spinal cord injury. So, it is not just semantics. Based on the false premise that glia cells block regeneration, surgeons are removing "scar" from human spinal cords. Patients are demanding it. Companies are trying to find ways of removing "scar". So, it is wrong and bad for patients for this term to be floating around. It gives the wrong impression.

There is one other reason why the use of the word "scar" is inappropriate when applied to gliosis in the spinal cord. There are true fibrous scars that develop in spinal cord injury. For example, as pointed out, when the spinal cord is cut and the dura is not repaired, fibroblasts do move into the spinal cord and form collagenous scars that are walled off by glial cells. Likewise, fibrous adhesions do develop between the spinal cord/roots with surrounding tissues. Removal of these adhesions or untethering the spinal cord is an important surgical procedure that can help restore function. The word scar should be reserved for such fibrous attachments and true scars instead of being meaninglessly applied to gliosis in the spinal cord.

Scientists should not be using the term "scar" so cavalierly. Words have power to mislead and this is one of those words that have actually led to harmful clinical practices and misleading concepts of spinal cord injury. It scares me every time I see somebody ask a question in the Cure forum about having their "scar" cut out from their spinal cord. Until somebody has better evidence that "scar" is preventing regeneration and that cutting scar out from the spinal cord is doing anything to improve function, I feel the necessity to speak out strongly against the use of the word scar to refer to gliosis in the spinal cord.

Wise.

from http://sci.rutgers.e...072#post1369072

[skeetie]

hi i had surgery on c3-c7 with titanium instrumentation. during surgery the instrument slipped and they said i had contussion and dural tear wich was sutured.
sry im not a typer lol hunt n peck. your post was of interest to me. i still dont understand all the changes of my body. it seams like every day is different.i have been a nurse for over 40 yrs but dont understand. all i know is pain 24//7 and still struggling with my rt side which is wose than left.i just wish i had someone who could explain all that i experiance. my name is skeetie and im new here

[Tetracyclone]

Skeetie,

Welcome three times, and I'm glad to see you finally post. When you have energy for it please type up something for your "about me" section of your profile.

Being in medicine does not prepare us for SCI unless were in rehab. Here in Taiwan the rehab nurses get a lot of special training and are sooo thoughtful, but this site is still the best place I know to learn about symptoms. Reading old threads is helpful, but where is there time between our bladder and bowel duties!