Stem cells and their recognization in the treatment of various ailments begun with the unearthing of the concept by Ernest A. McCulloch and James E.Till in the 1960s. Stem cells are basic cells and are still in their undifferentiated state. They are the potential candidates which upon rapid mitotic divisions will give rise to specialized cells after undergoing a process called cell differentiation. A differentiated cell is a specialized cell and constitutes the structural and functional basis of a tissue-system in a multicellular organism. Stem cells are distinctive from any other adult cell of the body in that

They are capable of continuous mitotic divisions and self-renewal over long periods without undergoing the process of differentiation. This property is called cell proliferation.

Stem cells are unspecialized and undifferentiated. They are therefore capable of specialization along a specific cell line upon receiving certain signals. The signals are by way of internal gene commands. The microenvironment of the cell generated by specific chemicals secreted by adjoining cells upon physical contact and otherwise triggers the process of specialization referred to as differentiation. Presence of protein Oct-4 is a factor that assists in turning on or off the genes responsible for differentiation. It does so by controlling transcription in undifferentiated cells.Stem cells also referred to as progenitor cells or mother cells and are broadly sorted out as

Embryonic stem cells which are derived from the 32-64 cell stage of the blastocyst or early morula stage during development of the fertilized egg. During this time the fertilized egg now referred to as blastula is 5-6 day old. Its appearance is similar to the mulberry fruit. In normal course of development the outer most cells referred to as epiblast are capable of giving rise to all the derivatives of three primary germ layers namely ectoderm, mesoderm and endoderm. Each of these layers has its unique role in development of specific cell type contributing to the formation of a specific organ and organ system. Presence of cell surface proteins such as glycolipid SSEA3, SSEA4 and keratin sulfate antigens besides Fibroblast Growth Factor FGF-2 and genetic manipulation is instrumental in infusing differentiation.

Adult stem cells are found primarily in the bone marrow and in a few other adult tissues. Their multiplication helps to replenish the depleting specialized cells to a constant number.

Cord blood stem cells lie in the in the umbilical cord of the foetus.

Stem cells are totipotent. This means that they are capable of being transformed into any specialized cell. Stem cells that keep dividing without undergoing the process of differentiation are called pluripotent cells. Unipotent stem cells are capable of generating only one line of specialized cells.

Multipotent stem cells of the type found in bone marrow contain hematopoietic cells. These cells are capable of differentiating into multiple varieties as red blood cells, white blood cells and platelets. Stem cells offer permanent solution to treat deadly diseases and eliminates the role of modern medicine. It does so by way of utilizing reparative or regenerative cell based therapy. Diseases as cancer, heart ailments, osteoarthritis, spinal cord injury, Alzheimer and Parkinson's disease will no longer be dreaded once this therapy is authenticated. They offer the possibility of renewable flow of fresh cells that replace defective cells. This is a life giving chance of rejuvination to the otherwise worn out and defective cells which were the underlying reasons for the manifestation of disease.

Cell based reparative therapy is successfully undertaken owing to the property called plasticity, inherent in stem cells. This means that undifferentiated cell from one tissue can be transformed into the specialized and differentiated cell capable of performing the function of yet another cell. Undifferentiated cells from neuron converted into blood cells or a heart muscle cell is an example of plasticity. Application of clonogenic assays of these undifferentiated stem cells in vitro culture can be used to beget specialized cell line.

Take the instance of a person suffering from osteoarthritis. Upon injection of proliferated differentiated stem cells into problem area, the existing diseased cells are soon replaced by fresh cells and are gradually incorporated into the existing tissue system. Once the integration is complete the functions of the recipient tissue carry on as on normal course. In this manner diseased cells are removed from the preview of the tissue system. However it needs to be ensured that newly differentiated cells included in the existing set up is not rejected by the recipient's immune system.