Here are some Frequently Asked Questions and a Glossary about stem cells and regenerative medicine.
Q: What are stem cells?
A: Stem Cells are the master cells of your body. They are a cell that possesses two properties: self-renewal and differentiation.
Q: What is regenerative medicine?
A: Is a newly emerging science and the clinical use of stem cells to repair tissues lost due to damage or decay.
Q: Are stem cells currently used in therapies today?
A: Blood stem cells are currently the stem cells most commonly used for therapy: doctors have been transferring blood stem cells by bone marrow transplant for more than 40 years. Advanced techniques for collecting or “harvesting” blood stem cells are now used to treat leukemia, lymphoma and several inherited blood disorders, among others. Cord blood, like bone marrow, is stored as a source of blood stem cells and is being used experimentally as an alternative to bone marrow and transplantation.
Q: What are the different kinds of stem cells found in the human body?
Adult stem cell: Tissue-specific stem cells. A stem cell found in fetal and/or adult tissues that typically generates the type of tissue in which it is found (blood stem cells make blood, neural stem cells make neurons, and so forth).Although commonly used and accepted, the term “adult stem cells” is a little misleading, since these cells are actually found in infants and children as well as in adults. Adult stem cells produce the different kinds of cells that maintain the body’s tissues and organs, and, importantly, they have the ability to divide and reproduce indefinitely. These cells typically produce the type of tissue in which they are found. Adult stem cells are sometimes also called somatic stem cells.
Bone marrow: The spongy tissue that fills most long bone cavities and contains hematopoietic stem cells. The bone marrow also contains other cell types such as mesenchymal stem cells, endothelial (vascular) cells, macrophages (debris clearing cells), and more.
Cord blood stem cells: Blood stem cells obtained from the umbilical cord and placenta following the birth of a child. While at this point in time cord blood is only a source of cells for use in hematopoietic transplantation, research is underway to identify and use other cell types present in this tissue such as mesenchymal or endothelial (blood vessel) stem cells.
Embryonic stem cell: ES cell. A cell derived from the inner cell mass of the pre-implantation blastocyst (around five to seven days post-fertilization in humans) that is pluripotent and capable of self-renewal in cell culture.
Mesenchymal Stem Cells: A specific class of adult or tissue-specific stem cells that generates connective tissues (including cartilage, tendons, and bone).
Q: What’s the difference between allogeneic and autologous stem cell transplant?
Allogeneic: Cells or tissue obtained from donors for use in transplantation. The term applies if the donor is related or unrelated to the transplant recipient.
Autologous: Cells or tissue obtained from the patient. Sometimes a patient will have a portion of her own tissues stored for therapeutic use later. Examples include privately banked umbilical cord blood or a patient’s own bone marrow that is stored prior to receiving chemotherapy for solid tumors. The patient’s own marrow may then be transplanted at a later date to “rescue” the person from the side effects of chemotherapy on her blood system.
Hematopoietic: Relating to the blood system whether blood-producing (such as bone marrow) or the cells themselves (including red blood cells and hematopoietic stem cells).
Histocompatibility: The degree of genetic matching between tissues or cells from a donor and a transplant recipient. The most important genes for tissue matching are HLA-A, HLA-B, and HLA-DR. People get one copy of each of these genes from each parent (three from mom and three from dad), so a person has six places to match for histocompatibility. Thus, a “full match” in transplantation is called a 6 on 6 or 6/6 due to correct matching at both the maternal and paternal copies of HLA-A, HLA-B, and HLA-DR. The lower the degree of matching at these genes, the more likely it is that a transplant will fail. For the most part, a child will only match half of their HLA genes to one or the other parent (3/6). Thus, parents are most often not nearly as compatible to be transplant donors to their children as are the child’s siblings, who in rare cases, can match perfectly to one another (6/6).
Immunosuppression: The use of powerful drugs to impair a patient’s immune system in order to prevent the rejection of transplanted tissues or GvHD. Long-term immunosuppression may lead to liver damage, cataracts, and/or infections, among other problems
In vitro: Literally, “in glass.” This refers to work completed in the laboratory. Thus, “in vitro fertilization” takes place in the laboratory.
In vivo: Literally, “in life.” This refers to biological processes that take place within the body.
Induced pluripotent cell (iPS): a type of pluripotent cell made directly from a somatic (from the body) cell. First achieved using mouse cells by Shinya Yamanaka of Japan in 2006, the technique has successfully been used to “reprogram” human somatic cells to a state very similar to ES cells. The iPS process uses three genes (Oct4, Nanog, and Sox2) with an occasional fourth (c-Myc) that are introduced to cells using viruses. Non-viral methods are under development.
Multipotent: A degree of developmental versatility that is less than totipotent and pluripotent. Multipotent means a stem cell may form many types of cells in a given lineage, but not cells of other lineages. For example, a multipotent blood stem cell can form the many different types of blood cells (red, white, platelets, etc.), but it cannot form neurons. Most adult or tissue-specific stem cells are multipotent.
Pluripotent: The potential of a stem cell that describes an ability to differentiate into all types of specialized cell in the body. Scientifically, a cell is termed pluripotent if it is capable of making derivatives of all three embryonic (basic) germ layers: endoderm (gut tissue), mesoderm (including blood, muscle, and vessels), and ectoderm (such as skin and nerve).