Skip to content

Stem Cells Research

Research about aging and health related issues

Archive

Archive for April, 2009

The endothelium is the thin layer of the cells which lines the interior surface of the blood vessels. This forms the interface between the circulating blood in the lumen and the rest of the vessel wall. Endothelial cell line the entire circulatory system from the cell to the smallest capillary. These cells reduce the turbulence and hence lead to the pumping of the blood to much further distance.

The endothelial tissue is the specialized type of the epithelium tissue which is one of the four types of biological tissue in the animals. More specifically it is a simple squamous epithelium.

Terminology

The foundational model of the anatomy makes the distinction between the endothelial cells and the epithelial cells on the basis of which the tissues can develop from and states that the presence of the vimentin rather than the keratin filaments separate them from the epithelial cells.

Endotheliums of the interior surface of the heart chamber are called the Endocardium. Both blood and the lymphatic capillaries are composed of the single layer of the endothelial cells called the monolayer.

Functions

  1. Endothelial cells may be involved in many aspects of the vascular biology. Some of the functions are as follows:
  2. Vasoconstriction and vasodilation, and hence the control of blood pressure.
  3. Blood clotting (thrombosis and fibrinolysis).
  4. Atherosclerosis.
  5. Formation of new blood vessels (angiogenesis).
  6. Inflammation.
  7. Barrier function – the endothelium acts as a selective barrier between the vessel lumen and surrounding tissue, controlling the passage of materials and the transit of white blood cells into and out of the bloodstream. Excessive or prolonged increases in permeability of the endothelial monolayer, as in cases of chronic inflammation, may lead to tissue oedema/swelling.

In some organs, there are highly differentiated endothelial cells to perform specialized ‘filtering’ functions. Examples of such unique endothelial structures include the renal glomerulus and the blood-brain barrier.

The role of Endothelium

I do feel that you must have an idea about the cholesterol. The cholesterol really leads to the blood pressure. There is a certain increase in the blood pressure if the cholesterol is increased in the blood vessel. I really feel that the endothelium can do a lot in controlling the heart disease. It is really a very important part of the blood vessel.

Scientists have recently discovered that when people digest fat then cholesterol is carried in the blood. This sometimes increases the blood pressure because the cholesterol forms a layer above the interior wall of the blood vessels. As a result the blood does not move smoothly through the blood vessels which may lead to heart diseases.

Dendritic cells (DCs) are a kind of the immune cells and as such it forms the part of the mammalian immune system. As far as the main process is concerned I must say that its main job is to process the antigen material and current it on the surface to other cells of the immune system, thus functioning as antigen-presenting cells.

The dendretic cells are present in the small quantities in the tissues that are in contact with the external environment which is mainly the skin and the inner lining of the stomach, lungs, nose and the intestine. We can also find them in the immature state of the blood.

As soon as they are activated they move to the lymphoid tissues where they react with the T cell and the B cells to initiate and shape the adaptive immune response. At definite expansion stages they grow branched projections, the dendrites that give the cell its name. However, these do not have any particular relation with neurons, which also have similar appendages. Undeveloped dendritic cells are also called veiled cells, in which case they possess large cytoplasmic ‘veils’ rather than dendrites.

History
Dendritic cells were first described by Paul Langerhans (Langerhans cells) in the late nineteenth century. It wasn’t until 1973, on the other hand, that the term “dendritic cells” was given by Ralph M. Steinman and Zanvil A. Cohn. In 2007 Steinman has been awarded the Albert Lasker Award for Basic Medical Research for his discovery.

Types of Dendritic cells
There are generally two kinds of the dendritic cells. I must say that the two kind of the dendritic cells are myeloid and plasmacytoid which is also called the lymphoid.

I would at first like to discuss the myeloid dendritic cells.

1. Myeloid dendritic cells
These are most similar to the monocytes. The MDC are made up of two subsets:

  • The more common mDC-1, which is a major stimulator of T cells.
  • The extremely rare mDC-2, which may have a function in fighting wound infection.

2. Plasmacytoid dendritic cells
These look like the plasma cells but have the certain characteristic of the myeloid dendritic cells.

  • Characteristic of the immature dendritic cells
  • High intracellular MHC II in the form of MIICs.
  • Expression of CD1a.
  • Active endocytosis for certain particulates and proteins; presence of FcgR and active phagocytosis.
  • Deficient T cell sensitization in vitro.
  • Low/absent adhesive and costimulatory molecules (CD40/54/58/80/86).
  • Low/absent CD25, CD83, p55, DEC-205, 2A1antigen.
  • Responsive to GM-CSF, but not M-CSF and G-CSF.
  • Maturation inhibited by IL-10.

Similarly there are some characteristic of the mature dendritic cells and I must tell you that these cells are really of great importance.

Beta cells are a type of the cell which is present in the pancreas in the areas called the islets of the langerhans. They make 65 to 80 % of the cells in the islets. The beta cells make and release insulin which is a hormone which regulates the level of the glucose in the blood. There is a baseline level of the glucose in the blood which is maintained by the liver. It can really respond quickly to spikes in the blood glucose. The response time is purely quick taking only 10 minutes.

If we leave the insulin apart, beta cells also release C-peptide, a byproduct of insulin production, into the bloodstream in equimolar quantities. You must know that the C-peptide helps to prevent neuropathy, and also other symptoms of diabetes related to vascular deterioration. Measuring the levels of C-peptide can give a practitioner an idea of the viable beta cell mass. Hence the C-Peptide is really very important.

The beta cells also produce the amyline which is also known as the IAPP islet amyloid polypeptide. Amyline acts as the part of the endocrine pancreas and contributes to the glycemic controls. Amyline metabolic function is really now some what characterize as the inhibiter of the appearance of the nutrients in the plasma. You can also say that it functions as the syenergic partner of the insulin. The insulin regulates the food intake for the long time and the amyline decrease the food intake for the short time.

Research
Much research has been done in the field of the beta cell physiology and the pathology. One of the major topics of concern is the effect of the beta cell on the diabetes. Many research scholars are really trying to find the way to cure or even control the diabetes with the help of the beta cells.
One of the other major topics is the replication of the adult beta cell and also its application in diabetes. The Larry L. Hillblom Islet Research Center at UCLA is one of the leading research centers in the field, within the Diabetes and Endocrinology Research Center, directed by Dr. Peter Butler.

Pathology
The diabetes mellitus type I is really caused by the destruction of the insulin producing beta cell by the cells of the immune systems.

In the diabetes mellitus type II is caused by decline of the beta cells over the time and the insulin resistance really plays a large role in the disease.

I would really say one thing and that is the research are really on and it could be very soon that we will find the permanent cure of the diabetes. This will really be a major break through in the field of medical science.

Somatic cells are the body forming cells of any organism and as the meaning suggest it really forms the body of any cell. The somatic word has been taken from the Greek word soma which really means the body.  It is quiet different from the germline cells. Germline cells are found in the mammals and the example of the germline cells those which participate in reproduction. However here you will not have to worry about it. I really feel that we are here to talk about the somatic cells and hence we should talk about the somatic cells which are also called body cells.

A simple use of the somatic cells can be determined as the cells which forms the body. The somatic cell contains the 46 chromosomes as 23 pairs of chromosomes. Each cell of the chromosome contains one chromosome from the father and the mother. This is really very interesting to note that the somatic cells contain twice the times the somatic cells contain the chromosomes. You should know that the somatic cells contain 46 chromosomes in 23 pairs whereas the germilne cells contain only 23 chromosomes which is really half the number as contained by the somatic cells.

As far as the gender of the born child is concerned you should know that it depends upon the fusion of the gernline cells. It’s really also known that the zygote contains46 chromosomes.

As far as the other species are concerned I must tell you that they contain a much more complex structure. As far as the different species are concerned I must tell you that those species which contains chromosomes arranged in pairs are called the diploid organisms. Those species which contain single unpaired chromosomes are called the haploids. However as far as the somatic cells are concerned the chromosomes arrange themselves in four or the tetraploids or even the six or the haploids. This means that they can have the diploid or the triploid germline cells. As an example you can take the modern cultivated species of the wheat which is called the triticum aestivum L, a hexaploid species whose somatic cells contain six copy of every chromatid.

In recent times the technique of cloning has really become very important. I do feel that you must have the idea about the cloning but the question really arises that what is really the importance of the somatic cells in the cloning process. Any retention of existing mitochondrial DNA prevents the new cell being identical. One method of doing this is called “somatic cell nuclear transfer” and involves removing the nucleus from a somatic cell, usually a skin cell.

I really feel that now you must have got an idea that how important the somatic cells are for the human body and its comparison with the germline cells.

Stem cells differ from the other kinds of cells in the body. There are basically three unique properties of the stem cells which are really very important. They have the capability of dividing and renewing for a long period of times. They are unspecialized and the third one is that they can give rise to the formation of the specialized cells.

Scientists are really trying very hard to understand the two fundamental properties of the stem cells which are really related to the self renewal properties of the stem cells.  The two fundamental properties are as follows:

  1. The first point is that how can the embryonic cells proliferate for so long and this also without differentiating where as the adult stem cells cannot.
  2. The second point is of the fact that how the stem cells can proliferate for so long and renews itself without differentiating.

While trying to answer these questions the scientists may find the way to understand how the cell proliferation takes place during the embryonic development abnormal cell division that leads to the cancer. In fact all these studies will help the scientists grow the embryonic cells and the adult cell better in the laboratory.

I would like to explain the two plus points of the stem cells in detail. The details with the description are as below:

1. Stem cells are unspecialized and can develop specialized cells
One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. A stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell); it cannot carry molecules of oxygen through the bloodstream (like a red blood cell); and it cannot fire electrochemical signals to other cells that allow the body to move or speak (like a nerve cell). However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.

2. Stem cells can divide and renew itself on it own
Unlike muscle cells, blood cells, or nerve cells-which do not normally replicate themselves-stem cells may replicate many times. When cells replicate themselves many times over it is called proliferation. A starting population of stem cells that proliferates for many months in the laboratory can yield millions of cells. If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal.

I really feel that these are some points which just reveal one point and that is the research on the stem cells can come out to be a major milestone in the field of medicine. We all know that the bio technology has really been a milestone in the field of medicinal world. And the research topics can really be more than a milestone.

An adult stem cell is an undifferentiated cell found among the differentiated cells in a tissue or organ can renew itself and can differentiate to yield the major specialized cell types of the tissue or organ. The primary roles of the adult stem cell in a living cell are to maintain and repair the tissues and organs in which they are found. There are now some scientists who spell the adult stem cells as the somatic stem cells. Unlike the embryonic stem cells the adult stem cells are a bit different. The embryonic stem cells are known by the organs in which it is found such as the inner cell mass and the blastocysts. The origin of the adult stem cell in the tissue is still unknown.

Research on the stem cell has really led to some of the very exciting results. The scientists have found many adult stem cells in many different tissues in which they have never thought of that it would be present. All this findings related to the adult stem cells have really prompted the scientists to think that they can be used for the transplant or not. In fact the adult blood forming stem cells from bone marrow have been used in transplant for more than 30 years.

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 differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of therapies for many serious common diseases.

The history of the research on the adult stem cell began about 40 years ago. In 1960, the scientists discovered that the bone marrow contain about two types of stem cells. One population which was called the hematopoietic stem cells and this formed the all types of the blood cells found in the body.

The second one which was called the bone marrow stromal cells was also discovered few years after. The stromal cells are the fixed cell populations that generate bones, cartilage, fats and fibrous connective tissues.

Where are they found?
The adult stem cells are found in almost all the tissues and organs. You must know one point and that is the stem cells are found in almost all the tissues and organs. Yes, you can say that they might be one or two but they are present in almost all the tissue and organs.

Scientists in many laboratories are trying to find the way to grow the adult stem cells in cell culture and manipulate them to generate specific cell type in order to cure various injuries and the diseases. We can thus hope only for the best.

In the Field of genetics and the developmental biology, the somatic cell nuclear transfer (SCNT) is a laboratory technique for creating the Clonal embryo, using an ovum with the donor nucleus. It can be used in the embryonic cell research or in regenerative medicine where it is sometimes referred to as “therapeutic cloning”. It can also be used as the first step for the reproductive cloning.

In SCNT the nucleus, which contain the organism’s DNA, of a somatic cell is removed and the rest of the cell discarded. At the same time, the nucleus of an egg cell is detached. The nucleus of the somatic cell is then inserted into the enucleated egg cell. After being inserted into the egg, the somatic cell nucleus is reprogrammed by the host cell. The egg, now containing the nucleus of a somatic cell, is stimulated with a shock and will begin to divide. After many mitotic divisions in culture, this single cell forms a blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to the original organism.

I would like to present some of the fields where the concept of SCNT can be used. I am listing two of them. They are as follows:

  1. SCNT in stem cell research
  2. SCNT in reproductive cloning

I would like to discuss the first one in detail. The detail is as follows:

SCNT in stem cell research
Only a handful of the labs in the world are currently using SCNT techniques in human stem cell research. In the United States, scientists at the Harvard University Stem Cell Institute, the University of California San Francisco, Stemagen (La Jolla, CA) and possibly Advanced Cell Technology are currently researching a technique to use somatic cell nuclear transfer to produce embryonic stem cells. In the United Kingdom, the Human Fertilization and Embryology Authority has granted permission to
research groups at the Roslin Institute and the Newcastle Centre for Life. SCNT may also be occurring in China.

In 2005, a South Korean research team led by Professor Hwang Woo-suk, published claims to have derived stem cell lines via SCNT, but supported those claims with fabricated data. Recent evidence has proved that he in fact created a stem cell line from a parthenote.

I must say that this is really a great step which is definitely going to take us to the new era where the medicines will have completely new meaning. Who had
though 20 years before that we will be able to grow the cells on our own? However this is a truth now. We can really do it.

I would also like to say that the SCNT has really been a find and it has really created a mile stone in the field of stem cell research.

A Genetic screen is the procedure or step to identify and select the individuals who possess the phenotype of interest. A genetic screen for new genes is often referred as the forward genetics and not the reverse genetics which the term to identify the mutant alleles that are already known. The mutant alleles that are not tagged for the rapid cloning are mapped and cloned by the positional cloning.

How to create a mutant population?

Since unusual alleles and phenotypes are rare, geneticists expose the individuals that are to be screened to a mutagen, such as a chemical or radiation, which generates mutations in their chromosomes. The use of mutagens enables “saturation screens” one of the first of which was performed by Nobel laureates Christiane Nüsslein-Volhard and Eric Wieschaus. A saturation screen is performed to uncover every gene that is involved in a particular phenotype in a given species. This is done by screening and mapping genes until no new genes are found.

Type of screening
I would like to describe the three types of screens for you. They are as follows:

1. Basic screen
A basic screen involves the looking for a phenotype of interest in the mutated population. One can really screen for the obvious phenotypes such as the fruit flies with no wing or a flower with no petal.

2. Temperature sensitive screen
More subtle is the temperature sensitive screen that involves the temperature shift to enhance the mutant phenotype. A population growth at low temperature would have a normal phenotype. However the mutation in the particular gene at the higher temperature will definitely make it unstable. You must know that the mutant phenotype is conditional and can be activated by just raising the temperature. A null mutation in such a gene may be lethal for the embryo and such mutation will be missed in the basic screen.

3. An enhancer or the suppressor screens
This is the most sophisticated type of the genetic screen. This type of the screen has the two advantages. First, new genes identified in the screen are often involved in the same biological process as the weak allele in the genetic background, in this case wing formation. Second, due to genetic redundancy, the mutant genes discovered may not have a visible phenotype of their own. In a more basic screen these would not be discovered, however, in the sensitized genetic background a visible phenotype is clear.

I really feel that the biotechnology has given a lot to the field of medicine. We are now on the verge to discover and cure many diseases which were not been able to be cured until now. Genetic screening is really a one small part of this vast field of biotechnology.