Stem cell

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Cell is a basic unit of life. Many cells combine to form tissues, many tissues combine to make an organ and all organs join together to form a body. Every organ is madeup of special type of cells due to which every organ differs from their appearance, working and composition. Therefore, every cell in the body has specific purpose but there are some cells which do not have yet any special role but can become any required type of cells. Cells which have specific purpose in the body are called as differentiated cells. Stem cells are undifferentiated cells which can become any kind of specific cells when needed. Scientists and doctor are more interested in stem cells as they are very helpful in explaining how some complex functions of bodyworks and how they sometimes go wrong.  Stem cells are providing a path for the cure of disease which are not considered as curable disease currently.

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Types of stem cells

Stem cells are been classified into categories on the basic of their potential to differentiate into other types of cells.

Totipotent : These types of stem cells can differentiate  into all possible cell types. After the formation of zygote, immediately formed few cells are called totipotent cells.

Pluripotent:These cells can differentiate into almost all cell types. Cells in the embryo are pluripotent.

Multipotent : These stem cells can differentiate into closely related family of cells. Adult blood stem cells can turn into red blood cells, white blood cells or platelets.

Oligopotent: These cells  differentiate  into few different types of cells. Adult lymphoid stem cells can differentiate into few other type of cells.

Unipotent:  these cells can turn into one kind of cells only which is their own kind. They are still stem cells because they can renew themselves e.g. adult muscle cells

*Embryomic cells are most potent cells but are considered as pluripotent  instead of totipotent because they cannot become the cannot  become the part of extra-embryonic membrane or placenta.

Sources of stem cells

Stem cells are present in whole body but are originated from two sources only; adult body tissues and embryonic cells. However, research is ongoing where scientists are working on the formation of stem cells from other body tissues under the technique called genetic reprogramming technique.

Adult stem cell (ASCs)

A human body contains stem cells throughout their life. The body uses these stem cells whenever they are needed. These stem cells are also called somatic stem cells or tissue specific cells because they are present in body of human from the time of embryo. The cells are in non specific state but are more specialized than embryonic stem cell. These cells remain in this state  until they are body needs them for specific purpose e.g. skin cells, muscle cells, etc. cells inside the body remain in process of repair and renewing by dividing to produce new body tissues. Stem cells are present inside different kinds of tissues. Scientists have successfully found the stem cells in tissues including brain, bone marrow, skeletal muscles, blood and blood cells, skin, and liver. Stem cells are difficult to find although they can remain in non-dividing and non-specific state for years until they are stimulated to generate into new and specific ones. Adult stem cells can divide indefinitely which means they can generate various cell types from the originating organ or can generate a new organ itself. Division and regeneration can be explained on the basic of healing of wounds by skin or repair of liver by itself.

Embryonic stem cells (ESCs)

When sperm fertilizes egg, first cell formed after fertilization is called zygote. After division of zygote in some no. of cells then it is called as embryo..after 2-5 days of fertilization embryo take form of a ball of cells called blastocysts. Embryonic stem cells come from blastocystes. They  are pluripotent stem cells i.e. they are stem cells which able to differentiate themselves in almost every cell type.

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Mesenchymal stem cells (MSCs)

MSCs come from the connective tissue or stroma that surrounds the organs and tissues of body. These stem cells have been used to create new body tissues, such as bone, cartilage, and fat cells. It is said that these cells will  become solution for wide range of health problems in future.

Induced pluripotent stem cells (iPSCs)

These cells are created by scientists in lab, using skin cells and other tissue-specific cells. These type of stem cells behave like embryonic stem cells, so are considered to be useful for development of different therapies. However, more research and development is necessary.

For production f stem cells, a sample is firstly extracted from adult cell or embryo. Then these samples are paced in a controlled culture where they will divide and reproduce but not specialize further. Stem cells that are dividing and reproducing in a controlled culture are called a stem-cell line. Researchers manage and share stem-cell lines for different purposes. These stems cells can be stimulated to specialize in a particular way. Until now, it has been easier to grow large numbers of embryonic stem cells than adult stem cells. However, scientists are making progress with both cell types.

Uses

Transplants : stem cells with right can take on any role of any type  and can repair damaged tissues after  illness or injury. Transplant of stem cells are already helping people with disease lymphoma

Tissue regeneration: Tissue regeneration is probably the most important use of stem cells.new tissue types or organs can be formed from stem cells under specific conditions which will be very useful in organ failure like liver, skin, kidney etc.

Cardiovascular disease treatment: In 2013, a team of researchers from Massachusetts General Hospital reported in PNAS Early Edition that they had created blood vessels in laboratory mice, using human stem cells.Within 2 weeks of implanting the stem cells, networks of blood-perfused vessels had formed. These new blood cells were as healthy and good a natural cells. It is expected that this type of technique could eventually help to treat people with cardiovascular and vascular diseases.

Brain disease treatment: Doctors may one day be able to use replacement cells and tissues to treat brain diseases, such as Parkinson's and Alzheimer's disease.

Cell deficiency therapy: As research in stem cell is developing ways to diagnostic world, it is hoping that in future scientists will be able to develop heart cells in laboratory conditions that can replace and repair damaged heart by repopulating hearth with healthy tissues. This technique will be useful for peple with type I diabetes who can receive pancreatic cells which can replace insulin producing cells (β- cells)

Blood disease treatments: hematopoietic stem cells are multipotent stem cells which are been used currently for treatment of diseases such as, sickle cell anemia, leukemia and other immunodeficiency problems.  Hematopoietic stem cells e present and found in blood and bone marrow.

Questions related stem cells are frequently asked in competitive exams like UPSC, UPPSC, HAS, HPAS, KAS, RAS, PCS, CDS, SSC CGL  and other exams.