This is a guest post by Mr.Manikandan Soundararajan
- Nobel Prize for Physiology/Medicine (2012):
- What are Stem cells?
- Where are Stem cells found?
- What are the application of Stem cells?
- Organ transplant and stem cells
- Controversy surrounding stem cells:
- Stem Cell research in USA
- Stem Cell : Pro and Anti Arguments
- Birth to Death- Not only you, your cell also grows:
- Significance of Gurdon and Yamanaka’s Discovery
Nobel Prize for Physiology/Medicine (2012):
- Given to John B. Gurdon and Shina Yamanaka for their discovery that differentiation of cells is a reversible process (explained below).
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.
What are 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 Stem cells 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 the application of Stem cells?
- 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.
Organ transplant and stem cells
- We have heard something called antibodies, some antigens, some WBCs(Police force of the body, ring a bell?? 8th class science). In higher classes, we were told, X has a kidney failure, needs kidney transplant to survive, but the kidney has to be from a blood relative else organ rejection will occur!
- The actual story here: Our body has its own frontline defense white blood corpuscles, which do not allow any foreign national whatsoever in to its boundaries. So an outsider kidney=alien, rejected entry, so the only way is to get a replacement from relative. In this application stem cells are a sustainable replacement
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 face the difficulty in extraction.
Stem Cell research in USA
US is one country where issues surrounding stem cells and their therapeutic usage are complex:
- State funding in stem cell & embryonic research was common in US
- Problems started with legalizing abortions in 1973.
- Now fearing that further state funding would encourage abortions, women especially poor and vulnerable would be exploited ban was placed on state funding on researches involving human embryos.
- As usual private, scientist lobby and great range of possibilities like a cure for parkinson’s, blood cancer , cardio problems with the loophole of lack of regulation in private sector all forced the government to lift the ban in 2001.
- Bush administration was behind this policy framework, which got critics from churches, anti-abortion movements, general public.
- Even now US has only partially lifted the ban still a moratorium remains, whereby embryos created solely for research only can get state funding.
Stem Cell : Pro and Anti Arguments
- Thus there was a need for pluripotent and totipotent cells for various purposes and that too bypassing all the above ill effects.
- 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:
- 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’!!
- 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.
- Now in 1960s this person called Gurdon said “Ordinary cells have only temporarily lost their pluripotency and if necessary changes made can become stem cells”.
- Gurdon proved it in his experiment, he 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. here the nuclei of a mature cell developed the new tadpole.
- But the second person Yamanaka went further proving, “no need the help of an egg cell to develop a new offspring, just any mature cell, like that of a skin, can be simply made pluripotent”. His major contribution was he identified the required genes and codes for making a mature cell pluripotent. The result was increased accuracy, efficiency in converting a mature cell to immature cell.[Dedifferentiation]
Significance of Gurdon and Yamanaka’s Discovery
- 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.
- 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.
Thanks Mrunal :)