Do I Really Need to know about Stem Cells

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Nobel Prize for Physiology/Medicine:                 

• Given since 1901                                                                
•  2012 laureates include John B. Gurdon and Shina Yamanaka awarded for their discovery that differentiation of cells is a reversible process (explained below).

Figure 1.Cell types based on their potency-
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What exactly are they talking about?

• To understand we need some preliminary info regarding human reproduction and development process.
• Humans reproduce sexually i.e. require two parents (need a sperm and an egg)
• The sperm fuses with the egg to form a fused product called zygote. This cell divides itself to develop in to a baby.
• Now here it is seen that we have only one cell (we know cells similar to brick of a wall, are bricks of our body) zygote, which develops the entire human having eyes, heart, lungs etc. i.e. one cell capable of producing an organism= totipotency (potential to develop a total organism).

There are some other cells which have the capability to produce limited types of tissues, some which can produce only one specific tissue based on which we classify them.. Look into the figure for the classification.

Let’s apply these practically. Now pluripotency and totipotency are concepts, while stem cells are specific cells which exhibit these characteristics.

Stem cells?

Definition wise a stem cell should be:

• Able to divide and differentiate itself into specialized cells.

• Importantly should have the capability of self-renewal, i.e. reproduce itself.

Where are they found?

• Usually human embryo is a very good source, where all cells are totipotent.
• Stem cells are also present in adults called adult stem cells or somatic cells. These cells are found in bone marrow [a very popular source], blood etc.
• These cells do the important function of replenishing tissues, to be simple replacing dead cells.

What are its applications?

•  Stem cells can be potentially used to replace diseased cells, lost cells [malfunctioning heart, trachea etc.].

• A cure for Parkinson like diseases [A degenerative disorder caused by cell death in brain]

• Type I diabetes can also have a cure with stem cells.

• Cure for blood cancer- leukemia. 
• And another most important application in organ transplants.

 Controversy surrounding stem cells:

• Stem cells were essentially sourced from human embryos in the beginning, which required embryonic cells. But some people saw this as killing of a child and charged it as murder.

• Also religious institutions resented to the use of embryos for research.
• Use of adult stem cells faced the difficulty in extraction.
  
  

  

  
  

Arguments so far regarding stem cells

Thus there was a need for pluripotent and totipotent cells for various purposes. It is here the two laureates [Gurdon and Yamanaka] came in with their contributions. Now Let’s try to understand what they did in simpler terms.

Birth to Death- Not only you, your cell also grows:

1. In Life the cells of an organism proceed from initial undifferentiated stage to mature specialized stage through the process of differentiation, like a student in schools, ‘studies science, history, geography, English’ while during graduation narrows his focus only to his ‘subject of specialization’, during doctorate further narrowed thought to ‘one area in a subject’!!!
2. Similar to this our cells at birth manage all functions, with maturity they specialize: eye cells for vision, heart cells for purification, pumping etc. And this natural process is irreversible, that is once they mature, cells never exhibit their magical ability to be the jack of all trades. This was the plight in 1950s.
3. Now in 1960s this person called Gurdon said “These cells have exhibited pluripotency once, so definitely they should have this capability inherent in them, we just need to kindle it back” and he proved this with his experiment with tadpoles= A revolution when you consider its applications today(as listed above).
4. Gurdon in his experiment simply took the nuclei (grain of brick, i.e. part of our cells, of course the master of a cell is its nuclei) of a mature cell from a frog replaced it for nuclei in a newly fertilized egg (already told you egg cells=totipotent) and developed it in to a new tadpole i.e. instead of kindling back an ordinary cell, just proved that the cell has the capability to go back.

   
   

   
   

   5.  But the second person Yamanaka went further, “no need the help of an egg cell, ordinary cell itself can be rekindled” -was his theory and he proved it by identifying the ways to kindle back.i.e. He identified some genes which codify some factors[tech: transcription factors 4 in number- Myc, oct ¾, Sox2 and Klf4, which keep the cells immature] that when introduced in to an ordinary cell can turn them back to pluripotent cells. He called them iPS [induced pluripotent cells].

   
   

   

   
   

Significance:

• Their discoveries were answers to problems surrounding use of stem cells.

• Was an easy way to convert ordinary cells to stem cells. A reliable source for pluripotent cells

• No destruction of embryos involved.

• Basis for cloning, the discovery of Gurdon was the basis for cloning.

Yet some problems still remain in this technology:

• Reliability, efficiency of conversion is still low.
• If put to improper use without sufficient research can lead to uncontrolled, cancerous growth of cells.

Conclusion:

Thus we see that these scientists have furthered a revolution and in here lays the answer to many incurable diseases of today.

Though clinical trials, human experimentation are not into practice yet, some preliminary treatments like bone marrow transplant, cardiovascular treatments with stem cells have been demonstrated elsewhere is a sample for the success of the technology.