M5L9: Stem cell technology

Stem cell technology

Stem cells are all-rounders. They have the capacity to convert to cells of other tissues. This ability is referred to as stem cell plasticity

When a human is formed in the womb of the mother, it passes through various stages. 

In this case, we find that it was once an embryo that could perform all the functions. However, as the embryo grows up into an adult, the organs start performing selective functions. For e.g. the hair performs the role of the hair and not the skin. The skin performs the role of the skin and not the blood. The blood performs the role of the blood and not the muscle. Why?

The answer to it lies in the stem cells. When the zygote is formed, it is an allrounder. Slowly and gradually, the cell starts turning off the chromosomes that are not required and keeps only those in ON condition, that are required. This does not mean that the chromosomes are lost. What we mean here is that the cell starts becoming selective in what role or function it is supposed to perform. This is known as cell plasticity.

Omnipotent/totipotent stem cells

Omnipotent or totipotent stem cells can originate a complete organism. The fertilized egg cell, the so-called zygote, develops to become an embryo by cells dividing. The cells arrange themselves in the blastocyst. The outer layers form the so-called trophoblast, which develops into the amniotic sac, the umbilical cord, and the placenta. The inner cell layers form the embryoblast, which becomes the complete human being. During this time, the stem cells are totipotent, i.e. they can originate a completely new organism including placenta, amniotic sac, and umbilical cord.

Pluripotent stem cells

Pluripotent stem cells also have the property to differentiate into all types of cells, but they cannot become an entirely new organism anymore. Pluripotent stem cells are particularly interesting to stem cell research and tissue engineering. The goal of the latter is to grow tissue in a three-dimensional structure and with complex tasks. One day, whole organs could be replaced by means of this method.

Multipotent stem cells

Multipotent stem cells can differentiate into various cell types of their tissue. For e.g. neuronal stem cells may become different types of brain cells, but no more muscle cells or heart cells.

Oligopotent stem cells

Oligopotent stem cells are still able to differentiate into a few cell types of their tissue. Blood-forming stem cells are multipotent. They can become erythrocytes, granulocytes, thrombocytes, and monocytes. The lymphoid stem cells become part of the immune system – namely T cells, B cells, and killer cells.

Unipotent stem cells

They can only become their own type of cell.

So, what if you can get hold of these pluripotent stem cells? You can make a completely new organ out of it.

For e.g., let’s say, a person lost his eyesight because of some mishap or accident. If his stem cells are available, we can completely create a new organ out of it. Or let’s say, a UPSC aspirant after clearing prelims drank too much alcohol in old Rajinder Nagar. Eventually, he lost his liver due to it. Can he make a new set of liver if his stem cells are available?

The answer is obviously yes. But we need to engineer and design them in a way that they resemble the original organ in shape size, weight ratio etc.

Recently the scientists have come out with a novel option. 3D printing

3D printing uses additive manufacturing technique. It deposits the ink layer by layer to form the shape that is required by the user.  This technique of combining medical science with engineering is called as Synthetic Biology. The medical scientists are trying to create an atlas/directory of each cell and its role. It is known as BioGrid. In 2018, the medical scientists successfully transplanted the first oesophagus, created using stem cells.

The Biological General Repository for Interaction Datasets (BioGRID) is a curated biological database of protein-protein interactions, genetic interactions, chemical interactions, and post-translational modifications created in 2003 (originally referred to as simply the General Repository for Interaction Datasets (GRID)

Induced Pluripotent Stem Cells (iPS)

iPSC are derived from skin or blood cells that have been reprogrammed back into pluripotent stem cells. For example, iPSC can be used to convert blood cells into other new cancer free cells for a leukemia patient, or neurons to treat neurological disorders. However, one important challenge is that the rate of success is less than1%.

The 2012 nobel prize in medicine to Shinya Yamanaka and John Gurdon was awarded for research on iPSC technology. Mr. Yamanaka has discovered that there are the four essential genes that can reprogramme the cells in our body and, in principle, be used to regenerate old cells or grow new organs. Collectively known as OSKM (for the initials of the genes, Oct4, Sox2, Klf4 and Myc), these Yamanaka genes are named after him. This has opened a new gateway for regenerative medicine. It deals with the process of replacing, engineering or regenerating human cells, tissues or organs to restore or establish normal function.