Multi cellular organisms have got cells that are referred to as stem cells. The major characteristic for the stem cells is there ability to differentiate and undergo cell division hence renewing them selves. In many tissues that continuously grow; they play the function of repairing the interior body tissues such as the skin whilst dividing continuously to sustain the live of an animal until the animal dies. Upon cell division, a stem cell can continue to remain a stem cell or differentiate into a specialized cell such as a brain cells. The major different between the stem cells and other cells is that, though initially unspecialized cells, they can differentiate to form specialized cells that play a defined role. Secondly, though cell division, they can renew themselves. It is notable that, stem cells can remain inactive and only divide when the need arises. For example, the stem cells in the heart remain inactive and only divide in special occasions.The major kinds of stem cells that the scientists have worked on are the adult stem cells and the embryonic stem cells. It is the embryonic cells that are used in cloning. Cloning involves a reproductive process, a procedure entailing in vitro fertilization. Though it has some great advantages, it also comes along with challenges too. The stem cells are crucial in the live of a living organism; it is responsible for the growth of the blastocyst and plays all its functions essential for the growth of this embryo. In adult tissues, through normal wear and tear, many cells in body tissues such as the bone marrow, skin and brain need to be continually replaced and it is the stem cells that are responsible for this regeneration of the worn out cells. Among the challenges brought about by the stem cells while regenerating is bringing about some diseases such as the diabetes among others. Much research needs to be carried out on these diseases in order to develop cell based therapies commonly called regenerative medicine. In the laboratories, scientists are employing the stem cells in order to develop other drugs and critically understand the growth from embryo and identify the cells responsible for birth defects. This research paper focuses on the stem cells, a very interesting biological field faced with many challenges and bringing about new great discoveries.DIFFERENT TYPE OF STEM CELLSThe embryonic stem cells
The embryonic stem cells are derived from embryo as a result eggs fertilized in vitro. Embryo stem cells are used for research purposes with the knowledge of the donors. It is imperative to note that the eggs are not fertilized in the body of a woman. The embryonic stem cells are grown in the laboratory in a culture medium dish containing necessary nutrients vital for growth. This is referred to as preimplantation. The cells divide on the surface of the dish while the inner surface of the culture is treated to prevent any division. The treated surface is called mouse cells where the cells attach themselves and derive nutrients form the feeder layer. Through technological advance, the feeder mouse cells are rarely used to decrease the chances of transmission of the molecules or viruses in the feeder mouse cell into the embryonic stem cell. In the culture dish, in case the embryonic stem cells divide and overcrowd, they are replanted in other cultures, a process called passage. The embryonic stem cells that remain proliferated in an original culture without dividing for a long period of time are pluriponent and are called embryonic stem cell line if they have not build up any genetic abnormality. The embryonic stem cell line is used for experiments in researches (Wobus, 2008).
Characterization is a process that evaluates the embryonic stem cell line in order confirms that they are exhibiting their desired properties. Though there is no generally accepted criterion of testing these characteristics, scientists employ a number of tests to confirm that they are in deed embryonic stem cells. Through subculturing and microscopic view, scientists evaluate whether they are healthy, remain undifferentiated and can stay for a long period and can divide. Presence of transcription factors, Oct4 and Nanog is carried out. The transcription factors are crucial during cell differentiation and switch the genes off and on at the right time during growth. The transcription factors maintain the embryonic stem cell during the undifferentiated state. By use of a microscope, one can evaluate whether the embryonic stem cells are altered or damaged. Embryonic stem cells are tested whether they remain pluriponent by permitting them to differentiate in a culture, suppressing their immune system so that they form a teratoma and controlling them while in the culture so that they can form three layers (The National Institutes of Health resource for stem cell research).ADULT STEM CELLS
According to The National Institutes of Health resource for stem cell research, adult stem cell "are an undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ" (online). Their major role involves repairing and maintaining tissues where they are located. They are commonly referred to as somatic stem cells by scientists. The adult stem cells can be used for transplant for a period of more that 40 years. By controlling differentiation of the stem cells, they can thus be used for transplant. Research has proven that stem cells can be found in the heart and in the brain. Further research has proven that, in the bone marrow, there exist two kinds of the adult stem cells, the hematopoietic stem cells and bone marrow stromal stem cells. The brain cells in a human being is said to constitute of three kinds of adult cells these are astrocytes, neurons and oligodendrocytes.Adult stem cells are found in a number of body tissues and organs that include the blood vessels, brain, teeth, heart, and liver among others. They are located in a designated area referred to as a stem cell niche. Some stem cells have been proven to be pericytes. Some stem cells cease to divide unless when stimulated to divide to repair the tissues. In every tissue or organ, there are limited numbers of stem cells hence removal of some adult stem cells in some tissues can affect normal functioning of tissue or organ. Scientists are working hard to derive ways of stimulating regenerating of adult stem cells in bones through the use of stroma which can thus be used to control diseases such as the type 1 diabetes and fixing injured heart muscles in case of a heart attack (National Institutes of Health, 2004).
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Adult stem cells are identified by identifying the kind of cells they develop once they labeled in a living animal or person. They can also be identified by putting them in a culture and transplanting them in to another animal and evaluating whether they repopulate the cells that were originally there. A single adult stem cell produces genetically identical stem cells.THE POTENTIAL SUCCESSES OF THE STEM CELL RESEARCH AND ITS CHALLENGES
The human stem cells have been used in a variety of ways in clinics and the scientific research. The compound events occurring as one grows have been better understood through the study of the human being embryonic stem cells. Deeper research has been carried out to evaluate the process the stem cell undergoes from being undifferentiated to being differentiated tissues or organs which is achieved through switching genes off and on. Through the study of the stem cells, it has been understood that some diseases such as cancer arise due to unusual differentiation and division of the stem cells. By understanding this phenomenon, new strategies have been developed to control the abnormal differentiation or cell division. These strategies involve control of cell differentiation and keen study of the genetic signals.The human stem cell is used as a control experiment for new drugs being invented. This is carried out using the pluriponent stem cells lines. However, for best results to be achieved, the pluriponent cell lines must be identical to understand the cells reaction to different medical tests and drugs. This is used in developing in the anti-tumor cancer drugs. The stem cells are also used for medical purposes in the cell based therapy. One can donate an ailing organ to another person as long as medical tests have proven parties are compatible. Since there is a higher demand for organs that the supply, the stem cells are used to develop tissues and organs into precise cell types. This has assisted in controlling of diseases such as the heart disease, spinal cord injuries, diabetes, burns, just but to mention a few.The cardiovascular diseases are a major cause of death. This includes a number of diseases such as coronary heat disease and stroke, these kill a person by killing the cardiac muscle when deprived oxygen. When deprived oxygen, the cardiac muscles overwork in efforts to maintain the cardiac output resulting to heart failure. The damaged cardiac muscle can be repaired through regeneration of the damaged cells hence new medication for the heart failure. A further and extensive research is being carried out on the use of the stem cells in heart failure treatment. Though tests have been done on smaller mammals such as the rats, the use of the stem cells in treatment of cardiovascular diseases has remained controversial and has not been fully accepted. However, pilot clinical tests are continuing to be carried out. The stem cells are also used in treatment of the type 1 diabetes. The National Institutes of Health resource for stem cell research notes that,In people who suffer from type 1 diabetes, the cells of the pancreas that normally produce insulin are destroyed by the patient's own immune system. New studies indicate that it may be possible to direct the differentiation of human embryonic stem cells in cell culture to form insulin-producing cells that eventually could be used in transplantation therapy for persons with diabetes (online).The scientists who employ the stem cells to achieve a certain preset goal are faced by a number of challenges. Among the greatest challenge is controlling differentiation of the stem cell to ensure that the cell possesses the desired characteristics. In efforts to reduce the chances of immune rejection, research is being carried out in generating "tissues that cannot be rejected" (The National Institutes of Health resource for stem cell research)CLONING USING STEM CELLS
Cloning produces an animal with the similar genetic material as the parent using a technique referred to as somatic cell nuclear transfer. It can also be used to produce embryonic stem cells. It is through cloning the Dolly the sheep was produced. In this process, the diploid nucleus of a somatic cell replaces the nucleus of an egg and a single genetic parent is used. This process has been faced with a lot of controversies due to the ethical and legal issues involved (Hanna, 2006).The stem cells are integral part of human body. Through continued scientific research, the understanding of these cells has yielded great results that have been employed by medical practitioners and researchers. The use of stem cells in treatment of the some diseases and cloning that produces a person with similar genetic make up is among the greatest achievement of research on the stem cells. Though some researches have not been fully exclusive continuous research will offer more insight on understanding of the stem cells that will further be translated productive use. Though the scientists are faced with numerous challenges with time, the challenges will be history.