Stem Cells

Embryonic Stem Cells:

These cells are supposedly the most primitive and potentially the best source of stem cells for treatment of various disorders. They are derived from blastocysts as their inner cell mass. However there are numerous ethical and legal issues regarding the use of these cells.

Undoubtedly, embryonic stem cells offers the most exciting form of clinical research since maximum cell lines i.e. yardsticks for maximum deranged tissues and organs can be formulated. However, one can also not ignore the fact that due to its ultra primitive nature there is a possibility of some unwanted side effects and malignancies (cancers) during therapies using this.

Umbilical Stem Cells from umbilical cord blood at birth:

Umbilical cord blood is a readily available source of stem cells used with increasing frequency as an alternative to bone marrow or peripheral stem cells for transplantation in the treatment of malignant and non-malignant conditions in children and adults. Umbilical cord blood transplantation provides a rich source of stem cells with several advantages, including:

• Prompt availability
• Decreased risk of transmissible viral infections
• Graft-versus-host disease (GVHD) in both human leukocyte antigen HLA-matched and HLA-mismatched stem cell transplants
• Ease of collection with little risk to mother or newborn.

Only recently has the importance of cord blood derived stem cells been established. Umbilical cord blood is an excellent source of highly proliferative stem cells capable of completely reconstituting the hematopoietic system. Practical advantages of cord blood include a lower risk and severity of graft-versus-host disease (GvHD) in HLA-matched and -unmatched recipients, ease of collection without discomfort or risk to the donor and prompt availability as a frozen graft.

Umbilical cord blood has been approved for use by the FDA's and other authorities since the late 1980s. The first umbilicial cord blood transfusion cured a blood cancer in 1988. Over 1,000 cord blood transfusions, frequently in children with leukemia, have been successfully performed in the United States with little or no side effects. Recent research has shown that umbilical cord blood stem cells have similar powers and health promoting benefits as do embryonic stem cells. Advances are being made each day in providing greater safety to the patient. New methods of separating the stem cells from all other blood components have resulted in a product that consists of only stem cells. Since these umbilical cord stem cells have not developed ABO and HLA antigens on their surface they do not induce graft-versus-host reactions nor other problems that may occur with embryonic and adult bone marrow stem cells.

Adult Stem Cells:

Bone Marrow:

Stem cells derived from bone marrow have been the most widely practiced form of transplants till the advent of the cord blood derived stem cells. Purists still prefer this form of therapy. A cell-based therapy that has direct stem cell relevance is the Bone Marrow Transplantation (BMT). The stem cells found in bone marrow are transplanted into cancer patients whose hematopoietic system has been destroyed by radiation or chemotherapy used to fight cancer. BMT has been used to benefit hundreds of thousands of patients for nearly three decades.

Recently, bone marrow has been discovered as a meaningful source for stem cells in regenerative medicine. However, for the moment, they are less preferred to umbilical cord cells for the following reasons:

• Bone marrow stem cells can carry dormant viruses that can be transmitted to the recipient from the donor. This presents an unacceptable risk
• The MSC population in bone marrow is scarce compared to umbilical cords
• Significant drop in MSC and their proliferative capacity with age.

Bloodstream:

Stem cells are collected by a procedure called “apheresis”. It requires the aid of a well-programmed cell separator that would provide the desired stem cells from the blood stream. This procedure is generally utilized for autologous (for self) use only. The limitation of this procedure is that it is lengthy, the total cell yield is suspect and the procured stem cells are obviously less plastic, thus making the homing and engraftment a big problem in most cases.

Adult Tissues:

Stem cells can be collected from adult tissue like skin, cornea, fat, teeth, organs like the small intestine and liver and other tissue. Research in this field is gaining in importance primarily because it presents us with an opportunity to use stem cells that are easy to procure, can be genetically modified, programmed to behave like embryonic stem cells and wholesomely available. It certainly offers us exciting prospects. These stem cells would also be generally utilized for autologous (for self) use.