Adult stem cells

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Overview

Adult stem cells are undifferentiated cells, located throughout the body that divide to replace the dead cells and helps to regenerate damaged tissues. Also known as somatic stem cells, these are present both in children and adults.

Adult stem cells are important, thanks to their quality to auto-renewing or divide, on an indefinite time and give rise to all cell types, regardless of body type from which they come.


Contents

1. Overview
2. History of adult stem cells
3. The role of adult stem cells
4. What tests are used to identify adult stem cells?
5. Adult stem cell differentiation


History of adult stem cells

Research on the history of stem cells began about 50 years ago. In 1950, researchers found that bone marrow contains at least two types of stem cells. Some of these are called hematopoietic stem cells that can divide in all types of blood cells in the body.

The second type is called bone marrow stromal cells (mesenchymal stem cells or skeleton stem cell). They were discovered a few years later. Hematopoietic non-stem cells make up (in small fraction) bone marrow stromal cells and can generate bone, cartilage, fat, supporting the formation of blood cells and fibrous connective tissue.


The role of adult stem cells

Adult stem cells have been identified in several organs and tissues, including brain, bone marrow, peripheral blood circulation, blood vessels, skeletal muscle, skin, teeth, heart, intestines, liver, ovary epithelium and testis. It is considered that they are positioned in a certain area of each tissue.

In many tissues, current evidence suggests the presence of certain types of stem cells, which compose the outer layer of small blood vessels. Stem cells can remain passive (without dividing) a long time until they are activated by the many of the cells normal requirements, to protect tissues from disease or injury.

Usually, there is a very small number of stem cells in every tissue and once it is removed from the body, their ability to divide is limited, which hampers the generation of large quantities of stem cells.

Scientists are trying to find the best ways to increase the amount of adult stem cells in cell culture and by trying to control them in order to produce certain types of cells so that they can be used to treat a disease or injury .

Some examples of possible treatments include bone regeneration, using cells derived from bone marrow stroma, development of insulin-producing cells for patients with type 1 diabetes and repairing damaged heart muscle from a heart attack with cardiac muscle cells.


What tests are used to identify adult stem cells?

Scientists use one or more of these methods for adult stem cells identifying:

- marking cells in living tissue, determining types of specialized cells that were generated
- elimination of cells from live animals, labeling in cell culture and transplanting them into another animal, in order to determine whether these cells can replace or repopulate their tissue of origin.

Important is the demonstration that a single adult stem cell can generate a line of genetically identical cells that give rise to all appropriate types of differentiated tissue cells. To experimentally confirm that a supposed adult stem cell is really a stem cell, scientists trying to confirm that the cell can give rise to genetically identical cells in a culture medium and also as a purified population of these stem cells can repopulate and re-form tissue after transplantation to an animal.


Adult stem cell differentiation

1. Normal ways for stem cell differentiation. In a living animal, adult stem cells have the ability to divide when needed and give rise to various types of mature cells that have characteristic shapes, specialized structures and contribute to a specific tissue function. The following are some examples of ways that can differentiate adult stem cells (which have been demonstrated both in vitro and in vivo).

- Hematopoietic cells give rise to all types of blood cells: red blood cells, type B lymphocytes, type T lymphocytes, natural killer cells, neturophile, basophils, eosinophils, monocytes and macrophages.
- Mesenchymal stem cells can form a variety of cell types: bone cells, cartilage cells (chondrocytes), fat cells (adipocytes) and other connective tissue cells such as those in tendons composition.
- Neural stem cells in the brain give rise to three types of existing cells in the brain: nerve cells (neurons) and two non-neuronal cell types.
- Skin stem cells are located in the basal layer of the epidermis and hair follicles. Epidermal stem cells give rise to keratinocytes, which migrate from the skin and forms a protective layer. – Follicular stem cells can contribute to hair follicle formation, but also the epidermis.

2. Trans-differentiation – A series of experiments have reported that certain types of stem cells can differentiate into cell types observed in the organ or tissue other than initially expected (eg, brain stem cells differentiate into blood cells that can differentiate into cardiac muscle cells, etc.). This phenomenon is called trans-differentiation.

Although isolated cases of trans-differentiation were observed in some species of vertebrates, this phenomenon in humans is still debated by researchers. Scientists have recently shown that certain types of adult cells can be reprogrammed into other cell types, following a process of genetic modification in vivo. Strategy can be a way of reprogramming the cells available in other types of cells that were lost or damaged due to disease.

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