What is cell?
Cell is a structural, functional and biological unit of all living organisms. Anton Von Leeuwenhoek was the first scientist to see and describe a living cell. Cells vary in their shapes, sizes and functions. Human body is made up of several different types of cell. Most of the cells are specialised to perform particular functions. For example red blood cells carry oxygen in the blood of human body, white blood cell protect the human body from infectious agents but both these cells are not able to divide.
What are stem cells?
Stem cells are special human cells that have the ability to develop into many different cell types e.g. nerve cells, heart cells, etc. during early life and growth. They can also act as an internal repair system in many tissues of the body. When a stem cell divides, each new cell which is formed has the potential to either remain a stem cell or become another type of cell (which can have more specialised function).
Properties of stem cells
- Stem cells are unspecialised: They are unspecialised cells which are capable of renewing themselves by cell division. One of the unique feature of stem cells is that they do not have any tissue specific structure, thus they are not allowed to perform specialised functions. For instance, a stem cell cannot carry oxygen in the blood as red blood cells nor they can pump blood through the body like heart cells. But unspecialised stem cells can give rise to specialised cells (like heart muscle cells, red blood cells, etc)
- Stem cells can give rise to specialised cells: Under certain normal or experimental conditions, stem cells can be induced to become tissue or organ specific cells which can perform special and specific functions. The process of unspecialised stem cells giving rise to specialised cells, is called differentiation. In the process of differentiation, the cell goes through several stages and becomes more specialised at each step. Stem cells divide differently in different organs. For instance in organ like bone marrow, the stem cells regularly divide and replace the damaged tissue where as in organs like heart, the stem cells divide under specific conditions.
Sources for Stem Cells
- Embryos formed during the blastocyst phase of embryological development lead to the formation of embryonic type of stem cell.
- Bone morrow and Peripheral blood tissue are the source of Adult type of stem cells.
- Umbilical cord, placenta, aborted foetal tissue are also sources of stem cells
Types of Stem cells
- Embryonic Stem cells
- Non-embryonic somatic or adult stem cells.
Embryonic stem cells
Adult stem cells
Similarities and differences between embryonic and adult stem cells
- Cell types: One major difference between these two types of stem cells lies in their ability to be differentiated in different types of cells. Embryonic stem cells can be differentiated into all cell types of the body because they are pluripotent. Whereas, adult stem cells have limited differentiating ability. They can differentiate into limited types of cells.
- Processing: In comparison to adult stem cells, the embryonic stem cells can be grown more easily in culture. Whereas, isolating adult stem cells is challenging as they are found rarely in mature tissues.
- Transplantation: The tissues which are developed from embryonic and adult stem cells may differ in the likelihood of being rejected after transplantation.
Induced pluripotent stem cells (iPSCs)
Classification of Stem Cells on the basis of potency
- Totipotent Stem Cells: These types of stem cells can differentiate into embryonic and extra embryonic tissues such as yolk sac, chorion, amnion etc. In humans, these tissues form the placenta.
- Pluripotent Stem Cells: These stem cells are equally potent when compared to totipotent stem cells except for one thing i.e. creating an entire organism. These cells can self renew and differentiate into any of the three germ layers (ectoderm, endoderm, and mesoderm). These three germ layers further differentiate to form all tissues and organs within a human being. There are several known examples of natural pluripotent stem cells. The best example is embryonic stem cells. The human-made pluripotent stem cell also exists and they are known as induced pluripotent stem cell.
- Multipotent Stem Cells: They can give rise to other cell types but their differentiating ability is limited e.g. mesenchymal stem cells.
- Oligopotent Stem cells: They are similar to multipotent stem cells but their differentiating ability is more limited. They can self-renew and differentiate only in closely related types of cell e.g. haematopoietic cells.
- Unipotent Stem Cells: They have the least differentiation potential of all the stem cell types. They have the ability to differentiate only into one type of cell e.g. muscle stem cells.
Applications of stem cells
Brain cell transplantation
Organ and tissue regeneration
Treatment for diabetes
Stem Cell Treatment in India
Guidelines related to Stem cells in India
- In 2002, Indian Council of Medical Research had released Draft Guidelines for Stem Cell Research/Regulation.
- In 2007, Department of Biotechnology had released Guidelines for Stem Cell Research and Therapy.
- In 2013, National Guidelines for Stem Cell Research were released. These guidelines help the clinicians and scientists working in the field to conduct research in scientific and ethical manner.
- In 2017, National Guidelines for Stem Cell Research were released. According to these guidelines, only bone marrow stem cell transplant for blood disorders is permitted.
Stem cell culture
|Biotechnology - Genetic Engineering, Cloning and Recombinant DNA|
|Bio fingerprinting and Bio Sensors|
|Bioinformatics, Biopiracy, Bio-grid|
|Biotechnology Institutional structure in India|
|Bt cotton, Bt Brijal and Issues|
|Human genome project