A cryopreserved bank of cells is a kind of freezed culture. The cells can be characterised, qualified
and shared.

Otherwise , the cells stored are highly susceptible to the adverse effects of laboratory accidents and microbial
contamination. They are also prone to genetic change which may not be recognized on microscopic examination but can have critical effects on their properties and characteristics. Thus cell banks also provide vital safe depositories of
precious material that would otherwise be lost over time.

Using stem cells banks as distribution centers also promotes standardisation of experimental research. A stem cell bank subjects all the stem cells to the same system of quality control and safety testing. This would provide a central resource with expertise in appropriate quality standards.

This would also influence more efficient international transfer of cells, by providing a central point for information on regulation.

The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst.

The blastocyst is formed by

• Trophoblast, which is the layer of cells that surrounds the blastocyst

• Blastocoel, which is the hollow cavity inside the blastocyst

• Inner cell mass, which is a group of approximately 30 cells.
• 

Culture

Growing cells in the laboratory is known as cell culture.

• Embryonic stem cells are isolated by transferring the inner cell mass into a plastic laboratory culture dish that contains a nutrient broth known as culture medium.

• The cells divide and spread over the surface of the dish. The inner surface of the culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide. This coating layer of cells is called a feeder layer. The reason for having the mouse cells in the bottom of the culture dish is to give the inner cell mass cells a sticky surface to which they can attach. Also, the feeder cells release nutrients into the culture medium.

• Over the course of several days, the cells of the inner cell mass proliferate. When this occurs, they are removed gently and plated into several fresh culture dishes. The process of replating the cells is repeated many times and for many months, and is called subculturing.
• After six months or more, the original 30 cells of the inner cell mass yield millions of embryonic stem cells. Embryonic stem cells that have proliferated in cell culture for six or more months without differentiating, are pluripotent, and appear genetically normal are referred to as an embryonic stem cell line.

• Once cell lines are established, or even before that stage, batches of them can be frozen and shipped to other laboratories for further culture and experimentation.

The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found.

They are also termed as  somatic stem cell. The origin of adult stem cells in mature tissues is unknown.

Adult stem cells have been found in many more tissues than they once thought possible. In right environment, certain kinds of adult stem cells seem to have the ability to differentiate into a number of different cell types, given the right conditions. If this is possible under lab conditions, these cells may become the basis of therapies for many serious common diseases.

About 40 years ago, researchers discovered that the bone marrow contains at least two kinds of stem cells. One population, called hematopoietic stem cells, forms all the types of blood cells in the body. A second population, called bone marrow stromal cells, generate bone, cartilage, fat, and fibrous connective tissue.

There are a very small number of stem cells in each tissue.They may remain non-dividing for many years until they are activated by disease or tissue injury.

The adult tissues reported to contain stem cells include brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin and liver.

Struggle, however is to  grow adult stem cells in cell culture and manipulate them to generate specific cell types so they can be used to treat injury or disease.

How To Identify Adult Stem Cells?

One or more of the following three methods are used to identify adult stem cells

1. Labeling the cells in a living tissue with molecular markers and then determining the specialized cell types they generate
2. Removing the cells from a living animal, labeling them in cell culture, and transplanting them back into another animal to determine whether the cells repopulate their tissue of origin
3. Isolating the cells, growing them in cell culture, and manipulating them, often by adding growth factors or introducing new genes, to determine what differentiated cells types they can become.

Stem cells taken from human embryos have been used to form tissues of the cerebral cortex, according to experts at the government backed research institute Riken. The tissues self-organised into four distinct zones very similar to the structure seen in human fetuses, and conducted neuro-activity such as transmitting electrical signals.

“Transplanting tissues could raise hopes for greater functional recovery,” the institute said.

But study of invitro cultivation of more mature cortex tissue, such as those with six zones like in the adult human brain, will be stepped up. The tissues could also serve as “a mini organ” for studying the causes of Alzheimer’s disease.

Embryonic stem cells are harvested by destroying a viable embryo, a process that some find unacceptable. Riken said cortex tissues were also obtained from “induced pluripotent stem cells,” which are similar to embryonic stem cells but artificially induced.

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Stem cells are present in most multi-cellular organisms.

The two broad types of mammalian stem cells are

• Embryonic stem cells
  These cells are isolated from the inner cell mass of blastocysts in embryo.In a developing embryo, stem cells can differentiate into all of the specialized embryonic tissues.
• Adult stem cells
  These are found in adult tissues and participate in  repair system for the body, replenish specialized cells and maintain the normal turnover of regenerative organs, such as blood, skin or intestinal tissues.

Stem cells can now be grown and transformed into specialized cells with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture.

Highly plastic adult stem cells from a variety of sources, including umbilical cord blood and bone marrow, are routinely used in medical therapies. Embryonic cell lines and autologous embryonic stem cells generated through therapeutic cloning are promising candidates for future therapies.

I needed a separate place to write on this topic as this topic is itself quite vast with all kind of possible ramifications.

Research in stem cells is quite promising and still evolving.

Be with me as I search and write.

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