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Medical Author:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• What are stem cells?
• Why are stem cells important?
• What are some different types of stem cells?
• Embryonic stem cells
• Fetal stem cells
• Adult stem cells
• Peripheral blood stem cells
• Umbilical cord stem cells
• Induced pluripotent stem cells
• Why is there controversy surrounding the use of stem cells?
• What are some stem cell therapies that are currently available?
• What are experimental treatments using stem cells and possible future directions for stem cell therapy?
• Stem Cells At A Glance
• Stem Cells Index

Most blood stem cells are present in the bone marrow, but a few are present in the bloodstream. This means that these so-called peripheral blood stem cells (PBSCs) can be isolated from a drawn blood sample. The blood stem cell is capable of giving rise to a very large number of very different cells that make up the blood and immune system, including red blood cells, platelets, granulocytes, and lymphocytes.

• Red blood cells carry oxygen around the body and give the blood its color.
  
  
• Platelets are cell fragments that stop a person from bleeding and help the body to clot and heal when it is cut.
  
  
• Granulocytes are a type of white blood cell that helps fight bacterial infection.
  
  
• Lymphocytes are a type of white blood cell that is part of the immune system, help fight other infections, and also may be involved in protection against cancer.

All of these very different cells with very different functions are derived from a common, ancestral, committed blood-forming (hematopoietic), stem cell.

Blood from the umbilical cord contains some stem cells that are genetically identical to the newborn. Like adult stem cells, these are multipotent stem cells that are able to differentiate into certain, but not all, cell types. For this reason, umbilical cord blood is often banked, or stored, for possible future use should the individual require stem cell therapy.

Induced pluripotent stem cells (iPSCs) were first created for human cells in 2007. These are adult cells that have been genetically converted to an embryonic stem cell–like state. In animal studies, iPSCs have been shown to possess characteristics of pluripotent stem cells. Human iPSCs can differentiate and become multiple different fetal cell types. iPSCs are valuable aids in the study of disease development and drug treatment, and they may have future uses in transplantation medicine. Further research is needed regarding the development and use of these cells.