DO YOY KNOW WHAT ARE STEM CELLS?

Stem cells are the primal cells of the body. The different cell types within the body are all derived from such cells- and hence the name. Stem cells are undifferentiated, "blank" cells that do not yet have a specific function. Characteristically, stem cells have a high capacity for self-renewal. This feature permits their continuous culture under laboratory conditions.

Stem cells have the unique ability to differentiate into a variety of cells. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function - such as a muscle cell, a red blood cell or a nerve cell.

Self-Renewing

Given the right environment, stem cells can give rise to a number of tissues that constitute the different organs. Also serving as a kind of repair system for the body, stem cells can divide repeatedly and then differentiate and replenish cells within the body. These unique characteristics are the reason why stem cells are considered a breakthrough in regenerative medicine. They have the potential for providing cells and tissues to treat various debilitating, life-threatening diseases.

Stem cells can be derived from various sources such as the bone marrow, embryos obtained by in vitro fertilization, amniotic fluid and umbilical cord blood.
There are three broad categories of stem cells, which can be derived from various sources such as the bone marrow, embryonic tissue, amniotic fluid and umbilical cord blood.

Types of Stem Cells
There are three main types of stem cells, which are usually considered for their potential use in research and medicine. They differ in their ability to self-renew:

Totipotent
These stem cells have the potential to become any kind of cell in the body. After an egg is fertilized, it undergoes a series of divisions to become an embryo and later a fetus. The cells that are formed during these first few divisions are totipotent i.e. they can become any cell in the body. Human cells have this capacity only during the first few divisions of a fertilized egg. After 3 - 4 divisions of totipotent cells, these cells will not be able to differentiate into any cell type.

Pluripotent
This type of stem cell has the ability to become almost any kind of cell in the body-except the cells of the placenta or other supporting tissues of the uterus. Pluripotent stem cells result after totipotent stem cells undergo the first few divisions. Embryonic stem cells at the blastocyst stage and fetal stem cells are pluripotent.

Totipotent and Pluripotent cells are essential for the development of an entirely new organism, which is why they are found in the early stages of development.

Multipotent
These cells can give rise to several other cell types, but those types are limited to mostly cells of the blood, heart, muscle and nerves. These cells function as a repair system for damaged tissue. Adult stem cells are a good example of multipotent stem cells.

Sources of Stem Cells
Stem cells can be harvested from various sources like the bone marrow, embryonic tissue, amniotic fluid or umbilical cord blood. Stem cells are classified according to the source from which they are obtained.

Somatic Stem Cells
Stem cells are found in small numbers in adult tissue such as brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, liver and umbilical cord blood. These cells are also called 'adult stem cells', even though the term 'adult' is incorrect as stem cells also occur in babies and children.

The primary role of stem cells in the body is to maintain and repair the tissues in which they are found, as they are multipotent in nature.

Somatic Stem CellsOf all adult tissue, the bone marrow is an extremely rich source of somatic stem cells. Drawn from the spongy tissue found in the center of bones, the main function of these stem cells is to make blood cells that circulate in our bodies and fight infection. In stem cell therapy, bone marrow was the earliest source of stem cells due to its rich supply.

The other rich source of stem cells is the blood left over in the umbilical cord and placenta of a newborn child. Till recently, this blood was (and continues to be) often discarded as medical waste. However, now that umbilical cord blood is known to be a rich source of stem cells, more people are choosing to bank these cells for its potential future use.

Embryonic Stem Cells (ESCs)
Embryonic Stem Cells (ESCs)These cells are derived from embryos that develop from eggs that have been fertilized in vitro and are donated for research. The embryos from which these cells are derived are four or five days old and are a hollow microscopic ball of cells called the blastocyst. The cells are removed from the blastocyst and treated in a culture dish where they divide into more embryonic stem cells. Because these cells are pluripotent, they are attractive candidates for use in stem cell research and therapy.

Embryonic (or fetal) Germ Cells (EGCs)
Embryonic (or fetal) Germ Cells (EGCs)These pluripotent stem cells are derived from primordial germ cells, which give rise to the gametes (sperm & eggs) in adults. They are found in a 5 to 9 week old embryo/fetus in the area that is destined to become either the testicles or the ovaries. Like the embryonic stem cells, primordial germ cells too are transferred into a specially treated culture dish to form germ cell colonies. Deriving stem cells through this process is controversial since the embryo or the fetuses from which the germ cells are obtained are destroyed. The embryo or the fetuses, even though not fully formed, are considered 'human' in many cultures and hence their destruction leads to ethical dilemmas. Such a dilemma exists even if the embryonic germ cells are derived from a fetus that is obtained as a result of a miscarriage or abortion.

Peripheral Blood Stem Cells
Peripheral Blood Stem CellsStem cells, in limited quantities, can also be found in the peripheral blood circulation. Peripheral blood stem cells are easier to obtain than bone marrow as they can be drawn from blood. Some studies have shown that these stem cells engraft faster than bone marrow stem cells.