What Are Stem Cell?

Stem cells are undifferentiated cells that can turn into cells with specific functions.

Research has been tapping into the potential of stem cells to treat some diseases that currently have no cure.

Sources of stem cell

There are two main sources of stem cells: adult body tissues and embryos. Scientists have been working on ways to produce stem cells from other cells by genetic “reprogramming”.

Adult stem cell

The human body contains a reservoir of stem cells throughout their life. This reservoir can be used as and when the need arises.  Also called tissue-specific or somatic stem cells, these cells exist from the time an embryo develops. The cells are in a non-specific state, but they are more specialized than embryonic stem cells.

For daily living, the body is constantly renewing its tissues. Scientists have found stem cells in tissues, including:

However, stem cells can be difficult to find. They can stay non-dividing and non-specific for years until the body requires to repair or grow new tissue.

Adult stem cell can divide or self-renew indefinitely. This means they can generate various cell types from the originating organ or even regenerate the original organ, entirely.   Healing of a skin wound or liver repairing itself after damage explains this division and regeneration.

In the past, scientists believed adult stem cells could only differentiate based on their tissue of origin. However, some evidence now suggests that they can differentiate to become other cell types, as well.

Embryonic stem cell

Embryo is formed once the sperm fertilizes the egg.  After 3–5 days the embryo forms a blastocyst or ball of cells.  The blastocyst contains stem cells and will later implant in the womb. Embryonic stem cells come from a blastocyst that is 4–5 days old.

When scientists take stem cells from embryos, these are usually extra embryos that result from in vitro fertilization (IVF).  In IVF clinics, the doctors fertilize several eggs in a test tube, to ensure that at least one survives. They will then implant a limited number of eggs to start a pregnancy.  When a sperm fertilizes an egg, these cells combine to form a single cell called a zygote. This single-celled zygote then starts to divide, forming 2, 4, 8, 16 cells, and so on forming an embryo.  Soon, and before the embryo implants in the uterus, this mass of around 150–200 cells is the blastocyst. The blastocyst consists of two parts:

an outer cell mass that becomes part of the placenta

an inner cell mass that will develop into the human body

The inner cell mass is where embryonic stem cells are found. Scientists call these totipotent cells. The term totipotent refer to the fact that they have total potential to develop into any cell in the body.

With the right stimulation, the cells can become blood cells, skin cells, and all the other cell types that a body needs.

In early pregnancy, the blastocyst stage continues for about 5 days before the embryo implants in the uterus, or womb. At this stage, stem cells begin to differentiate.

Embryonic stem cells can differentiate into more cell types than adult stem cells.

Mesenchymal stem cells (MSCs)

MSCs come from the connective tissue or stroma that surrounds the body’s organs and other tissues.

Scientists have used MSCs to create new body tissues, such as bone, cartilage, and fat cells. They may one day play a role in solving a wide range of health problems.

Induced pluripotent stem cells (iPS)

Scientists create these in a lab, using skin cells and other tissue-specific cells. These cells behave in a similar way to embryonic stem cells, so they could be useful for developing a range of therapies.

However, more research and development is necessary.

To grow stem cells, scientists first extract samples from adult tissue or an embryo. They then place these cells 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. They can stimulate the stem cells to specialize in a particular way. This process is known as directed differentiation.

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.

There are multiple types of stem cell treatment are available in these day.

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