CULTURED STEM CELLS AND BONE MARROW TRANSPLANTATION

Stem cells are undifferentiated cells which have the potential of differentiating into several kinds of cells. These cells are used for transplantation in patients, whose immune and blood forming systems have been devastated by leukemia, cancer, chemotherapy or other unknown causes. In the foetus, the blood cells are created in the liver, but just after birth they are produced exclusively in bone marrow. If marrow is transplanted to the same individual from where it was taken for culture, it is described as autotransplantation and if donated to someone else, it is called allogenic transplantation.

Monoclonal antibodies have been used to stem cells from the mass of cells in the bone marrow. These monoclonal antibodies react to a cell marker or antigen called CD34, which is specific for primitive bone marrow stem cells.

Several hormones are also available which stimulate replication of precursor blood cells e.g. granulocyte colony stimulating factor (G-CSF), Interleukin-6, Interleukin-11 and stem cell factor.

Monoclonal antibodies linked with toxins can be used for killing the malignant cells. Chemotherapy with extracted bone marrow can also be used for destroying malignant stem cells.

In future, efforts are being made to store the stem cells of a healthy person permanently and use them whenever required. This will be possible when the techniques to culture stem cells would be standardized specially using umbilical cord blood which may become an important source of stem cells.