Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: thedoc on 16/09/2015 23:50:02
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C Bruce Rodgers asked the Naked Scientists:
If a human liver can rebuild itself, and some lower life forms can regrow entire limbs, is there any research being done to help human amputees?
What do you think?
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Human livers do not "rebuild" themselves. I am attaching a picture of a cirrhotic liver. Does it look rebuilt to you?
Furthermore would you really have newt genes inserted into your DNA? Would you not then have strange compulsions about flies?
If we had some eggs we could have ham and eggs....if we had some ham.
Put yer money on prosthetic research, kiddo.
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The original poster is referring to the impressive regenerative capacity of the liver in response to injury. Whilst cirrhosis might eventually occur, this is the result of sustained damage to the liver, either by alcohol or other drugs, metabolic injury, or infections like hepatitis C. Were the liver not able to repair and regenerate itself to the extent that it can, then it would have failed much sooner.
This remarkable restoratative potential is exploited in transplantation. A tissue-matched individual can elect to donate 80% of their own liver to a recipient. The remaining 20% can regenerate a new liver in the donor, while the 80% given to the recipient endows them with a healthy safety factor to compensate for the demands of transplantation and - hopefully - sufficient viable tissue from which to regenerate a healthy organ.
The liver has evolved to possess this capability owing to the metabolic demands it faces during life. Other organs and body parts, however, do not have the same regenerative ability for a range of reasons. Cardiac and skeletal muscle tends to regenerate poorly and has a predisposition towards scar formation, limiting further recovery. Neurones are post-mitotic, meaning that they are non-dividing and once lost are gone for good (with a few exceptions). Skin is full of stem cells and can regenerate rapidly to close a wound, but more significant structural changes - where the scaffold of mature skin that guides and supports the stem cells is lost - cannot be compensated: a full-thickness burn, for example, often requires a skin graft. When we circumcise a baby, the penis does not grow a new foreskin.
Clearly, however, organs and tissues had the capacity to develop in the first place, so something must be preventing or blocking this process during healing in some situations, although we do not yet know what, or why. One reason may be to prevent cancer.
What researchers are now doing is to explore how organs and tissues develop to begin with, and what genetic pathways control this process. The next step will be to attempt to reactivate these genetic programmes in a time and spatially-limited way to achieve repair and replacement of missing body parts.
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The question on the table (As stated by "The Doc" his own self) is can research help amputees. Not may research help amputees someday.
What sets a fine medical practitioner (or medical researcher) from a pedestrian one is the ability to define the question with accuracy and precision.
While it is true that future clinicians may perhaps someday be able to regrow a foot in a traumatic amputation ..... someday -- that is still on the come. Neither does it begin to address amputation with co-morbidities such as peripheral vascular disease or diabetes.
I read the gentleman's question as a request for help today. Which is why I told him to put his money on prosthetic research today. Long John Silver has to cope as best he can with a peg leg. Modern AK amputees -- if they have enough moola -- can get a C-leg.[1.] Ain't that right, matey? Arrrr.
When a clinician blithely seems to throw off liver regeneration among those not in the know of seeing people suffer slow, painful deaths from chronic liver failure, it makes my teeth hurt.
This is a teaching moment to discuss the wisdom of getting tested for Hepatitis C - a cause of chronic failure. Current estimates are that ~ 214,000 people are infected with Hep C in England as of 2014 [3.] They have treatments for that now which work pretty well. Take a look at that liver picture I showed above and see if you want to be tested or go have a drinkee-poo.
Went to my doctor yesterday
She said I seem to be okay
She said, “Paul, you better look around
How long you think that you can
Run that body down?
How many nights you think you can
Do what you been doin’?
Who, now who you foolin?”
-Paul Simon, Run that body down [2.]
[1.] [2.] [3.] https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/337115/HCV_in_the_UK_2014_24_July.pdf
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I think you'll find that I have answered the question ("is there any research being done to help human amputees?") clearly, and provided additional background information to help to explain the current state of knowledge relevant to the subject area. I have also clarified the misconception surrounding liver cirrhosis.
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Hmmm, you sound miffed. Sorry about that.
Perhaps I can tell you my hepatitis story to improve the evening hour.
I believe I was infected with Hep B by one of the last surviving vets to have died of his wounds.
This Japanese-American vet had volunteered out of the concentration camp at Manzanar to fight Hitler in Italy [1.] When he was wounded he was given blood, but nobody knew from Hepatitis B in 1944.... but Hepatitis B knew about him.
So when I admitted him to his bed in 1983 at the Sepulveda VA Medical ICU, he barfed blood all over me. He did that because the wound caused the transfusion which caused the Hep B which trashed his liver -which caused the esophageal varices which ruptured and killed him the next day.
And infected me with Hepatitis B from being "washed in the blood" as I learned the next month.
So if I seem to react strongly to your rather blithe description of a miraculous liver repairing itself, it touches a nerve.
As to my response to this question about amputation, the readers can take it and use it today --- not some great come and get it day in the future. That is why I am here.
And maybe I have saved some reader's life by talking about Hep C testing which is also why I am here.
So,again. sorry about that.
[1.]
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There's a difference between repair or regenerate (from mechanical trauma) and disinfect. Back to the lizard: an infected stump won't regrow.
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There have been some amazing recoveries reported following accidental amputation of fingertips (https://en.wikipedia.org/wiki/Regeneration_in_humans#Fingers) in children.
Unfortunately, this recovery is inhibited by the traditional treatment - covering the wound with a flap of skin.
Also unfortunately, it seems to be more random in adults.
Now a fingertip has a similar structure to the remaining segment of the finger, so replication of already-differentiated cells could restore it. However, a finger joint has many different types of cells, different from the adjacent section of finger, so a more sophisticated set of instructions would be required to regenerate a whole finger.
As the OP commented, the axolotl (https://en.wikipedia.org/wiki/Regeneration_(biology)#Amphibians) is able to regenerate a whole limb, including joints, and many lizards can regenerate a lost tail. It would be great to be able to "replay" the instructions which originally built the limb - but we can't do that today.
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Perhaps Mr. Rodgers may find this video of the first Briton to receive an "i limb" prosthetic hand demonstrate its utility to be germane.
Or perhaps this video showing DARPA's progress in developing "mind-controlled" prosthetic hands might be of interest. He may find the sight of a quadriplegic now able to take her first drink of water by herself in 15 years a cause for optimism.