So how stem cells can give rise to specialized cells? Today we know that when unspecialized stem cells lead to specialized cells, this process is called differentiation. Although the differentiation of cells normally takes place in several stages, they are becoming more specialized at each stage. Scientists are just beginning to understand the signals inside and outside cells that trigger each step in the process of differentiation. The internal signals are controlled by cells of genes that are alternated by long strands of DNA and carry coded instructions for all cellular structures and functions. The external signals for cell differentiation include chemicals, allocated to other cells, physical contact with neighboring cells and certain molecules in the microenvironment of the organism. It is this interaction of signals in the differentiation of stem cells into specialized not only allows them to differentiate, and to find out which cells need help. (Park 2001)

Stem cells in human organism typically generate the types of cells in tissues where they live. For example, hematopoietic stem cells in the bone marrow normally gives rise to many types of blood cells. The process of stem cell therapy occurs during their differentiation into healthy specialized cells. This means that the human body itself knows what organs or tissues should be treated. Stem cells themselves are, of course, circulate through the blood vessels, and the process of differentiation begins in the affected part of the body. Today, however, it is not clear whether the new cells replace old ones or make them “recover”. The only thing that scientists were able to prove experimentally was that replacing the old cells with new ones, but only if the disease is not hard. Otherwise, scientists believe stem cells secrete a special substance that causes the diseased cells regenerate. (Park 2001)

As for the obstacles to treatment with stem cells, the main one is blocked blood vessels (blood clots, etc.), which do not allow stem cells to reach the affected areas. This becomes a crucial factor in the event that the causative agent of the disease still continues to actively suppress the body – in this case it becomes impossible to cure the disease. In addition, it often happens that the disease in human body is hidden or is in its initial stage of development, and the body simply does not perceive it, and stem cells “pass” the painful organ or tissue. A next possible obstacle is aging of stem cells they grow old, and this feature of any living organism, alas, can not be stopped.

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