Super Human Part 2 - Regeneration

November 28, 2011

Torah Kachur

Wolverine could do it.  Claire Bennet could sorta do it.  I want to do it.


'It' is superhealing or regeneration and it's not just for comic book characters.  I want to be able to repair lost or damaged tissues so I will never have to worry about heart failure, kidney disease or neural degeneration and it's almost possible.  Regeneration is the ability for our cells to replace cells that have run their course or those that have been used and abused and can't quite hack it.  We have a natural ability to regenerate some tissue - like bone marrow - where our body is constantly replenishing blood cells to fuel our body. 


The ability to regenerate is caused by stem cells, tiny populations of cells in certain organs that have the unique ability to differentiate, or change fate into a new cell type or, more importantly, divide into more stem cells.  These stem cells are considered the holy grail of modern medicine and has been the focus of intense research since their existence was proposed in the 1960's.  They have the theoretical capacity to regrow any limb, organ or tissue in the body and replace those that we are just kinda bored with, like my current neurons.


Growing a heart in culture has been done, albeit it was a rat heart, but it's a start.  And even bladders have been successfully cultured and transplanted back into recipient patients.  This is the new frontier of medicine.


How do cells do it?  Organs are complex assortments of different cell types - take your heart for instance, it is a complex of muscle cells, nerve cells and connective tissue that make our most powerful muscle.  When a heart grows in an embryo it has the inherent capacity to sense what types of cells should be developed (or differentiated) and it also has the capacity to 'sense' it's size and the position of certain cells in the organ.

To heal a full limb, for instance, like the gecko's tail takes a massively complex form of 'patterning' to determine where and when a certain cell should develop.  You don't grow unusually large upper arms with short dumpy forearms (T-rex notwithstanding) or you don't grow massively long fingers with tiny little wrists.... and all of this has to be programmed into the framework of genes that control development.



If we want to truly have regenerative capacity, we can grow organs in culture and transplant them like some researchers have been doing, but that is hardly Wolverine-esque.  What would be way cooler is to be able to turn on genes that originally controlled our limb development at a later time point in development, like after an ampuation.  I'm not saying this is really all that possible yet, just a plausible sci-fi version of what our bodies actually have done.  We have to somehow manipulate the cells into thinking they aren't in the adult but rather in the embryo - growing a limb for the very first time.


The major genes that control limb patterning are genes with awesome names like Sonic Hedgehog and Notch, signals that tell the cell where they are in the growing tissue. Sonic hedgehog is a) wicked and b) a gene that controls the identity of the bottom of a limb.  If you don't have functional SHH, then you can get mirror-image hands like the Simpsons characters as well as other defects.  They are active throughout the life of the adult organism as well, controlling things like stem cell division and maintaining our regenerative capacity.  So maybe we could just develop a drug to turn on SHH and these other signals to regenerate our own tissue?  Sounds simple...... let's do it. 


Not so simple, it turns out.  The genes often involved in proliferation and growth also, in later years, contribute to cancer.  So you can grow a new arm if you also want a tumor along with it.  Is in situ regeneration really possible?  Our livers do it, so does our skin, we have latent genetic capacity to build any organ or tissue we want, we just need to figure out the series of switches to do it.  It might not happen like Wolverine, but that's just a story, real-life is way cooler.



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