Sure. With a lot of organs, the function is a relatively mundane process. The heart pumps. The liver filters. The skin grows and dies and grows some more. This simplifies things a bit.
The challenge is to get all the right cells in the right places. Heart cells need to be arranged specifically so that the heart can pump. Wikipedia has a good animated gif of how the conduction wave flows through the heart [1].
Fortunately, this is a surmountable challenge. You can throw progenitor cells into a pre-built scaffold and they tend to organize like they should. This is because most organs in your body are built of relatively interchangeable parts. E.g. Most of your heart is the same kind of muscle cell.
The brain is a bit different. First, the type of damage is very dependent on the disease state. Have we lost entire neurons? What regions are affected? Are our neurons de-mylenating?
Second, your brain is unique to you. Sure, we both share stereotyped architecture: we both have a hippocampus, a cerebral cortex, a cerebellum, etc etc. The structure inside each region is pretty stereotyped too - we both have cortical bundles in our neocortex.
But when you drill down to the cellular level, we are very, very different. Each neuron I possess in my brain has a unique (and dynamic) synaptic arbor that connects to thousands of other, unique neurons.
If I suffer a stroke and a portion of my brain dies, you can't simply throw more neurons in to compensate. Effectively, neurons are not interchangeable parts like heart muscle cells. You need to coax those neurons to:
Another way to look at it is the information theoretic perspective: when organ X is damaged? what information do you need to grow it back? If X is anything but the brain (and maybe part of the spine), the information you need can almost always be picked from somewhere else (Stem cells plus standard human anatomy). We can't do that now, but in principle it should work.
But if you lose part of your brain, then it's a tougher challenge, because your personal memories, skills and more are stored in it. The only way to recover that would be to use the redundancy your brain might feature. Otherwise, it's lost. Sometimes, you cannot recover a code from a burned piece of paper.
Now, if your brain just suffers a terminal illness, but the information is still there, then healing you may be as difficult as copying your whole soul into a computer, synapse per synapse. (Or it may not: we do have way to slow down —not heal— Parkinson, for instance.)
That's exactly the sort of thing I'm coping with right now. The best currently available treatments can only mask and slow the progression of symptoms; the only really effective therapy at the moment is to try to build redundancy into the system at a rate approaching the loss of "primary storage". That includes nutrition, aerobic exercise (which, admittedly, looks a little bit silly when performed by someone who has difficulty controlling his limbs and maintaining posture) and keeping the ol' mind as active as it can be. That's hard, too -- it is very easy to let frustration overcome you and decide to lie down and die. But as long as there's a life worth living after the grunt work, it's something I'll keep on doing.
That said, I'm not holding on to life for its own sake. At some point I will either become incapable of any real physical activity OR too stupid to live. I've gotten a little taste of both when I've needed to get a baseline reassessment of my condition (which is not a typical presentation of anything, but seems to be more like Parkinson's than anything else on the menu). It's a bit of a race, really. I'm hoping that stupid wins, and that when it happens I do something so spectacularly stupid on the way out that it will make the news the world over (and perhaps win me a Darwin award).
interesting, thank you. I dont want to go so much off topic but I am interested in challenges upon regrowing parts of brain -- can you point me to some good (pref online) read?
The challenge is to get all the right cells in the right places. Heart cells need to be arranged specifically so that the heart can pump. Wikipedia has a good animated gif of how the conduction wave flows through the heart [1].
Fortunately, this is a surmountable challenge. You can throw progenitor cells into a pre-built scaffold and they tend to organize like they should. This is because most organs in your body are built of relatively interchangeable parts. E.g. Most of your heart is the same kind of muscle cell.
The brain is a bit different. First, the type of damage is very dependent on the disease state. Have we lost entire neurons? What regions are affected? Are our neurons de-mylenating?
Second, your brain is unique to you. Sure, we both share stereotyped architecture: we both have a hippocampus, a cerebral cortex, a cerebellum, etc etc. The structure inside each region is pretty stereotyped too - we both have cortical bundles in our neocortex.
But when you drill down to the cellular level, we are very, very different. Each neuron I possess in my brain has a unique (and dynamic) synaptic arbor that connects to thousands of other, unique neurons.
If I suffer a stroke and a portion of my brain dies, you can't simply throw more neurons in to compensate. Effectively, neurons are not interchangeable parts like heart muscle cells. You need to coax those neurons to:
A) live in relatively hostile environment
B) synapse to appropriate neuronal populations
C) weight those synapses correctly.
[1]http://en.wikipedia.org/wiki/File:ECG_Principle_fast.gif
Side note: Thanks for the heads-up on the Cloudera post - I just migrated themes and servers last night :)