Undifferentiated cells that can give rise to specialized tissues and organs are Stem Cells. Medical and Scientific interest in Stem Cells is based on a desire to find a source of new, healthy tissues to treat diseased or injured human organs. It is known that some organs, Such as the skin and the liver, are adept at regenerating themselves when damaged, but it is not understood why and how some tissues are capability and other do not. Recent research has indicated that stem cells are a key to these regenerating properties.

 Stem cells are the future plan of constructing the human organs. Stem cells differ from other kinds of cells in the body. All stem cells- regardless of their source- have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types

Stem cell are classified into these type of cells and they are mentioned below

          Embryonic stem cells are 'harvested' or collected from the very early stages of a fertilized egg called a                   blastocyst 

          Adult stem cells are collected from a limited number of cell types in the body. Typically these are bone           marrow cells or from very early stages of tissue development.

         Umbilical cord stem cells are collected from the cells of the umbical cord of a recently born baby. Some        of these cells are slightly undeveloped and so can turn into other types of cells  (multipotent)                  

  Stem cell biology has gained tremendous interest in the recent years, driven by the hope of finding cures for several diseases through transplantation medicine. Various types of stem cells have been identified from preimplantation embryos, the fetus, placenta and adult. The isolation of human embryonic stem cells has been considered the biggest breakthrough of the 21st century. Some of these stem cell types are charged with ethical controversies although they are versatile and offer tremendous potential for finding cures for incurable diseases. In fact, cures for diabetes, heart diseases and many other diseases via stem cell research is expected within the next 10 years

  The goal of any stem cell therapy is to repair a damaged tissue that can't heal itself. This might be accomplished by transplanting stem cells into the damaged area and directing them to grow new, healthy tissue. It may also be possible to coax stem cells already in the body to work overtime and produce new tissue. To date, researchers have found more success with the first method, stem cell transplants.

  Stem cells have the remarkable potential to develop into many different cell types in the body. Serving as a sort of repair system for the body, they can theoretically divide without limit to replenish other cells as long as the person or animal is still alive. 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 brain cell.

This document covers basic information about stem cells. For a more detailed discussion, see Stem Cells: Scientific Progress and Future Research Directions. Or you can check our Frequently Asked Questions page for quick answers to specific queries. 

Throughout Stem Cell Basics, the first reference to a Glossary term on a page appears in bold, underlined maroon type. Clicking on the term will open its definition from the Glossary page in a new window.


Stem Cells and Diseases

The Promise of Stem Cells
        Studying stem cells will help us understand how they transform into the dazzling array of specialized cells that make us what we are. Some of the most serious medical conditions, such as cancer and birth defects, are due to problems that occur somewhere in this process. A better understanding of normal cell development will allow us to understand and perhaps correct the errors that cause these medical conditions.

Another potential application of stem cells is making cells and tissues for medical therapies. Today, donated organs and tissues are often used to replace those that are diseased or destroyed. Unfortunately, the number of people needing a transplant far exceeds the number of organs available for transplantation. Pluripotent stem cells offer the possibility of a renewable source of replacement cells and tissues to treat a myriad of diseases, conditions, and disabilities including Parkinson's and Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis.

Have human embryonic stem cells successfully treated any human diseases ?

Scientists have been able to do experiments with human embryonic stem cells (hESC) only since 1998, when a group led by Dr. James Thompson at the University of Wisconsin developed a technique to isolate and grow the cells. Moreover, Federal funds to support hESC research have been available since only August 9, 2001, when President Bush announced his decision on Federal funding for hESC research. Because many academic researchers rely on Federal funds to support their laboratories, they are just beginning to learn how to grow and use the cells. Thus, although hESC are thought to offer potential cures and therapies for many devastating diseases, research using them is still in its early stages.

Adult stem cells, such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs), are currently the only type of stem cell commonly used to treat human diseases. Doctors have been transferring HSCs in bone marrow transplants for over 40 years. More advanced techniques of collecting, or "harvesting," HSCs are now used in order to treat leukemia, lymphoma and several inherited blood disorders.

The clinical potential of adult stem cells has also been demonstrated in the treatment of other human diseases that include diabetes and advanced kidney cancer. However, these newer uses have involved studies with a very limited number of patients.


What are stem cells ?

Stem cells are cells that are capable of growing into any of the 300 different kinds of cell in the human body. 

Where do they come from ?

They can be taken from embryos a few days old, and researchers extract them from human embryos that have been discarded during fertility treatments. 

Stem cells can also be found in adults and children. For example, we all have blood stem cells, which are found in the bone marrow and continuously replenish the body's red blood cells, white blood cells, and platelets. 

But embryonic stem cells are more flexible to work with. Scientists believe they are essential to research into how to coax stem cells to grow in certain types of cells needed. 

What are stem cells used for ?

Scientists want to make use of stem cells' ability to grow into any kind of cell by growing them in the laboratory and using them in tissue transplants and to help to treat disease such as Alzheimer's, Parkinson's and diabetes. 

Where does cloning come into all this ?

Therapeutic cloning - the creation of human embryos solely for the production of stem cells, rather than with the intention of creating a new human being, could be used to clone a patient's DNA, harvest stem cells, and grow them into the type of tissue needed. 

Scientists hope that this would eliminate the problems of tissue rejection caused when someone else's tissue is used in a transplant. Cloning embryos for their stem cells would also provide a steady supply of cells for research. 

What has George Bush decided ?

He has decided to allow federal funding for embryonic stem cell research, permitting American scientists to carry out experiments on about 60 stem cell cultures already in research facilities using government money. 

However they cannot use government money to extract stem cells from new embryos, an operation which would kill the embryo. But private money can still be used for this kind of research. 

What about other countries ?

Several countries are considering legislation on stem cell research. For example, the Japanese government has said it is likely to approve research on clone embryos and embryonic stem cells within a year, while The British parliament has voted in favour of allowing stem cell research using early human embryos in December last year. 

Who objects to stem cell research, and why ?

Anti-abortion and ethics groups oppose such research because it results in human embryos being destroyed. The Coalition of Americans for Research Ethics argues the case like this: "The destruction of human embryonic life is unnecessary for medical progress, as alternative methods of obtaining human stem cells and of repairing and regenerating human tissue exist and continue to be developed." 

There is also a strong religious lobby opposing embryonic stem cell research. When the Pope visited George Bush recently, he told the US president that the work was as evil as infanticide, because obtaining the cells involves destroying early stage human embryos, and US Catholic bishops told him that the work is "illegal, immoral and unnecessary".