Stem cells are the cells other than sex cells. They are found in almost all the multicellular organisms. They have the ability to differentiate into different kinds of cells like skin cells, blood cells etc. they undergo the process of mitosis for their multiplication. There are two types of stem cells that are embryonic stem cells and adult stem cells isolated from inner cell mass and adult tissues respectively. Scientists are now able to grow stem cells in the laboratory. These cells have the ability to renew themselves after having some type of injury through cell division and maintain their undifferentiated state.

The world of molecular biology has progressed to this level that now scientists are able to reprogram the tissue or skin cells into embryonic stem cells having the same characteristics like the original stem cells. For this purpose, scientists do not need eggs or embryos. The experiments were performed in mice at the Institute for Stem Cell Biology and medicine at UCLA. The reprogrammed cells will be able to differentiate into every cell type which is present in the body.

Reprogramming of Tissue Cells into Embryonic Stem cells:-
In 2007, scientists performed experiments on the mouse models. Mouse fibroblasts have been used, the cells which develop into connective tissue. Four transcription factors have been added with the fibroblasts which bind to the special sites present on the DNA molecule. This process enabled the scientists to convert the fibroblasts cells into the pluripotent cells. Pluripotent cells are those which have the tendency to differentiate into three germ layers that is endoderm, mesoderm and ectoderm. By performing this experiment, scientists tested that pluripotent cells were just the same as the embryonic stem cells.

Scientists are hopeful that if the process is replicated in humans, it may lead to the production f limitless source of immune friendly cells and they may be helpful in tissue engineering and transplantation medicine. Many diseases can be cured if this technique is applied in humans. For example, if the human skin cells are reprogrammed into embryonic stem cells, these stem cells can be able to differentiate into various types of cell such as motor neuron cells to treat Parkinson's disease, beta islet cells for the treatment of diabetes and hemotopoetic cells to make blood cells to treat the patients suffering from leukemia.

A researcher at the UCLA described that the cells which were reprogrammed could not be differentiated from the original stem cells. There was not a slight difference in the characteristics of the reprogrammed cells from the original ones. These cells can be beneficent in the different therapeutic techniques and can be helpful in treating various diseases.

This method of reprogramming the cells can be replaced with the therapeutic cloning as it is a very controversial technique. If a single normal human cell can be reprogrammed with this method into the embryonic stem cells and has the same properties of stem cells then it will be better to develop human cell lines and the technique of stem cell nuclear transfer can be stopped.

Another important feature of the reprogrammed stem cells was that they were not only functioning similar to the original embryonic stem cells but they were also similar in their biological structure. Usually, a cell' nucleus contains the DNA which stores the complete genetic information of the organism and is wrapped around the histones. Histones are tagged with some chemicals which determine that which genes are expressed and which are shut off. When the reprogrammed cells were examined, they had the same location of the chemical tags and also the DNA chromosomes were identical to the original embryonic stem cells. Researchers are now working on the reprogramming of the human cells. It is uncertain to say anything positive about the research before the right time.

Reprogramming of Skin Cells into Embryonic Stem cells:-
In 2008, stem cell scientists at UCLA successfully managed to reprogram human skin cells into embryonic stem cells. These cells have the same characteristics as the embryonic stem cells. Kathrin Plath and other researchers at the UCLA research centre use the genetic alteration to convert human skin cells into human embryonic stem cells. These cells have the ability to differentiate into any cell type. In this method four regulator genes have been used to produce the cells which are called as Induced pluripotent Stem Cells. This method of producing stem cells can be helpful in treating the diseases whether genetic or acquired by creating cells which are immune compatible.

This research was conducted after getting the successful results, when experiments were performed on the mouse models using tissue cells to create embryonic stem cells. The cells derived from skin cells also have the same functions and biological structures as the original stem cells.

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