Cells for New life
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Types of Stem Cells

Adult Stem Cells

For many years, researchers have been seeking to understand the body’s ability to repair and replace the cells and tissues of some organs, but not others. After years of work pursuing “how and why” of seemingly indiscriminant cell repair mechanisms, scientists have now focused their attention on adult stem cells. It has long been known that stem cells are capable of renewing themselves and that they can generate multiple cell types. Today, there is new evidence that stem cells are present in far more tissues and organs than once thought and that these cells are capable of developing into more kinds of cells than previously imagined. Efforts are now underway to harness stem cells and to take advantage of this new found capability, with the goal of devising new and more effective treatments for a host of diseases and disabilities.

Adult Human Stem Cells and Their Primary Direction of Differentiation

Cell Type Tissue-Specific Location Cells or Tissues Produced
Hematopoietic Bone marrow, peripheral blood Bone marrow and blood lympho-hematopoetic cells
Mesenchymal stem cell Bone marrow, peripheral blood Bone, cartilage, tendon, adipose tissue, muscle, marrow stroma, neural cells
Neural stem cells Ependymal cells, astrocytes (subventricular zone) of the CNS Neurons, astrocytes, oligodendrocytes
Hepatic stem cells In or near the terminal bile ductules (canals of Hering) Oval cells that subsequently generate hepatocytes and ductular cells
Pancreatic Stem cells Intra-islet Nestin positive cells, oval cells, duct cells Beta cells
Skeletal muscle Stem cells Muscle fibers Skeletal muscle fibers
Stem cells of the skin Basal layer of the epidermis, bulge zone of the hair follicles Epidermis, hair follicles
Epithelial stem cells of the lung Tracheal basal and mucus-secreting cells, bronciolar Clara cells, alveolar Type II pneumocyte Mucous and ciliated cells, type I and II pneumocytes
Stem cells of the intestinal epithelium Epithelial cells located around the base of each crypt Paneth’s cells, brush-border enterocytes, mucus secreting goblet cells, enteroendocrine cells

 

Indeed, if the adult stem cells exist in all types of human tissues this means that each tissue and each body has its own regenerative potential. Under normal conditions this potential is realized in the physiological regeneration i.e. renewal of the cells that have completed their life cycle and died. We know that the intestinal epithelial cells live for only 6 days and the erythrocytes live for 120 days. Cells that have exhausted their time and died should be replaced with the new ones; this exact function of continuous update of cellular composition of the body is performed by adult stem cells.

In regenerative medicine adult stem cells can be used in three ways. First: these cells can be identified, multiplied and differentiated into the desired cell type and administered to the patient without fear of immune rejection reactions in autologous transplantation when adult stem cells are taken from the patient and administered to the same patient. The second way: in allogeneic transplantation (cells are taken from one patient and administered to another) the need to use immunosuppressive agents appears again (as in the case of the derivatives of embryonic stem cells). Finally, the third area is the use of biologically active substances that can stimulate adult stem cells of the patient which will increase the intensity of the restoration of the damaged organ (tissue), i.e. it will accelerate the process of reparative regeneration.