What the heck are "human induced pluripotent stem cells?"

In 2012, the Nobel Prize in Physiology or Medicine was awarded to John B. Gurdon and Shinya Yamanaka for their discovery that essentially any mature specialized cell can be reprogrammed to become stem cells capable of developing into all tissues of the body.  These are called "human induced pluripotent stem cells" (iPSC).  So, in principle, you can grow new brain cells from mature skin cells.  This has application in Alzheimer's disease research, and my brother-in-law (Leonard) sent me this article about its promise from Nature Molecular Psychiatry.  

When I started reading the article, I thought it might point to reprogramming any cell to produce new neurons in the brain.  Unfortunately, it was only about reprogramming cells in vitro -- in a test tube -- so that they can be used to study the disease.  From the best of our understanding, most of the success I've had in battling Alzheimer's disease has related to the ability of the brain derived neurotrophic factor to prompt stem cells in the hippocampus to form new brain cells.  (We discuss this in Beating the Dementia Monster.)  Research I've read suggests that you can run out of stem cells, which may stop the recovery process.  So I'm nervous.

The article goes into a great deal of detail regarding what we know about Alzheimer's disease, and I was gratified to note that we cover pretty much everything they discussed in either this blog or in the new edition of Beating the Dementia Monster.  Our version of the facts is just easier to understand.  However, the article did present a broader picture of all of the different types of brain cells that should be studied due to their role in Alzheimer's disease.  Since development of the process for generating new cells, laboratories around the world have now developed lines of all kinds of brain cells with all kinds of varying genetic profiles.  The article does not go beyond discussing their potential in research, although it does go into detail on how they might be used.

In this blog and in Beating the Dementia Monster, we discuss three types of cells in the brain whose failures are part of Alzheimer's disease.  These are:

• Neurons that apparently die due to deposition of beta amyloid plaques on their outside surface as well as due to collapse of microtubules into "tangles" from failure of tau protein
• Microglia -- the brain's unique immune cells -- that may fall down on the job of removing the beta amyloid and errant tau protein
  
• Endothelial cells of the blood-brain barrier that become diseased and permit destructive bodies to enter the brain -- notably in the hippocampus

The article highlighted three additional types of brain cells that are being cultured to study Alzheimer's disease.  We have not discussed these previously.

• Astrocytes perform a variety of functions in the brain, including metabolic functions, but their failure during Alzheimer's disease is poorly understood.
• Oligodendrocytes are important to signal propagation between cells and fail as a result of brain injury and a variety of neurodegenerative diseases.
• Pericytes can differentiate into new neurons in the event of cell death, but also play a key roll in regulating the blood brain barrier.  When the blood brain barrier fails, destructive pathogens and other substances can enter the brain.  

Yes, this was a nerdy article, and I noticed some your eyes glazing over.  Others didn't even get this far.  On the other hand, I thought it was all pretty interesting, and maybe some of you did too.