Stem cells are the body’s raw materials. They are the cells from which all other cells that perform specialized functions are generated. Under appropriate conditions in the body or laboratory, stem cells divide to form more cells called daughter cells.

These daughter cells either become new stem cells or specialized (differentiated) cells with another, more specialized function, such as blood cells, brain cells, heart muscle cells, or bone cells. No other cells in the body have this natural ability

Researchers hope that stem cell studies will help:
• Increased understanding of how disease occurs: By watching stem cells grow until they become cells in bones, heart muscle, nerves, and other organs and tissues, researchers can better understand how diseases and conditions develop.

• Generating healthy cells to replace cells affected by disease (regenerative medicine): Stem cells can be directed to become cells of a specific type that can be used in patients to regenerate and repair tissues damaged or affected by disease.

Patient groups who can benefit from stem cell treatments include people with spinal cord injuries, type 1 diabetes, Parkinson’s disease, amyotrophic lateral sclerosis, Alzheimer’s disease, heart disease, stroke, burns, cancer, and osteoarthritis.

Stem cells may have the ability to grow into new tissue that can be used in organ transplants and regenerative medicine. Researchers continue to develop information about stem cells and their uses in organ transplantation and regenerative medicine.
• Testing new drugs to determine their safety and effectiveness: Before using research drugs on people, researchers can use some types of stem cells to test the safety and quality of the drugs. This type of testing is likely to have a direct impact first on the development of drugs for cardiotoxicity testing.

New areas of study include the effectiveness of using human stem cells that have been programmed to become specific tissue cells to test new drugs. For testing of new drugs to be accurate, the cells must be programmed to have the same specific characteristics as the cells the drug targets. Researchers are still studying methods of programming cells so that they become cells of a specific type.

For example, neurons could be generated to test a new drug to treat a neurological disease. Tests may show whether the new drug has an effect in cells and whether the cells have been damaged.
Where do stem cells come from?

Stem cells have multiple sources:
• Embryonic stem cells: These stem cells come from embryos that are between 3 and 5 days old. The embryo at this stage is called a blastocyst and its body contains approximately 150 cells.
These stem cells are multipotent; That is, they can branch out to produce more stem cells or they can become any type of cell in the body. This versatility allows embryonic stem cells to be used to regenerate or repair diseased tissues and organs.

• Adult stem cells: These stem cells are found in small numbers in most adult tissues, such as bone marrow or fat. Adult stem cells have a limited ability to form different body cells compared to embryonic stem cells.Until recently, researchers believed that adult stem cells could only create similar types of cells. For example, researchers believed that stem cells in bone marrow only made blood cells.
However, recent evidence suggests that adult stem cells may be able to form many cell types. For example, stem cells in bone marrow are capable of forming bone or heart muscle cells.

• Adult cells transformed to acquire the properties of embryonic stem cells: Scientists have succeeded in converting normal adult cells into stem cells using genetic reprogramming. By transforming adult cells, researchers can reprogram the cells to perform the same functions as embryonic stem cells.
This new approach may allow the use of reprogrammed cells instead of embryonic stem cells, avoiding the immune system’s rejection of the new stem cells. However, scientists have not yet known whether or not using transformed cells will cause harmful effects in humans.

Researchers are now able to take normal connective tissue cells and reprogram them into functional heart cells. Some studies have found that animals with heart failure who were injected with new heart cells showed improved heart function and survived longer.

• Stem cells before birth: Researchers discovered the presence of stem cells in amniotic fluid in addition to umbilical cord blood. These stem cells have the ability to transform into specialized cells.
Amniotic fluid fills and protects the sac surrounding the fetus that forms in the uterus. Researchers were able to determine the presence of stem cells in amniotic fluid samples drawn from pregnant women for testing or treatment purposes, a procedure called amniocentesis.