¶ … Embryonic Stem Cells to Cure Disease
Embryonic Stem Cell
Derivation of Human Embryonic Stem Cells
Generation of Cardiomyocytes from Human Embryonic Stem Cells
Purified Population of Cardiomyocytes
Use of Transgenes in Differentiated Cardiomyocytes
Use of Human Embryonic Stem Cells for Heart Conditions
Neurological Disorders and Use of Human Embryonic Stem Cells
Parkinson's Disease
Stroke
Huntington's disease
Amyotrophic Lateral Sclerosis
Human Embryonic Stem Cells for the Generation of Functional Hepatic Cells
Ethical Considerations of Using Human Embryonic Stem Cells
Social Oppression
Value of the Embryo
Pluripotent stem cell cultures were isolated in 1981 by Evans and Kaufman from mouse blastocysts. It was found that these cells were capable of self-renewal having a long-term capacity to remain undifferentiated in certain provided culture conditions. Studies have highlighted the basic difference between stem cells and embryonic stem cells. Embryonic stem cells have the potential to differentiate into three germ layers. These cells have an additional capacity to proliferate in culture conditions in an undifferentiated state plus these cells usually disappear after differentiating into germ layers. For clinical purposes, origin of human embryonic stem cell is pre-implantation embryo. The stem cell lines have been derived from inner cell mass of human blastocysts that are produced by in-vitro fertilization. The studies have shown that human embryonic stem cells have the properties of embryonic stem cells (Cai et al. 2007, p. 1229). The properties include derivation from pre-implantation embryo, prolonged proliferation in the culture in an undifferentiated state and a capacity to form three germ layers. In addition to this, it has been seen that human embryonic stem cells can maintain diploid karyotype and an expression of higher telomerase activity when cells are kept in cultures for longer periods.
There are two main properties of embryonic stem cells, indefinite cell renewal and an ability to differentiate into one or more cell types. Successful studies and applications of murine embryonic stem cell research have paved the way to study more about important applications of human embryonic stem cells. Several tissues in the human body depend on a pool of adult or somatic stem cells for maintenance. The tissues include hematopoietic system, skin, gut and some parts of the central nervous system. Studies have shown that the depletion of stem cell pools can lead to many diseases that include leukemia, lymphoma, and certain genetic defects. Other kinds of diseases involve tissue destruction where these tissues are unable to be revived by the stem cell pools. These diseases and conditions include Type 1 diabetes that occurs because of auto-immune destruction of pancreatic beta cells and liver failure occurring because of liver cirrhosis either because of toxins or certain infectious agents (Zou et al. 2009, p. 98). Main way to treat these diseases is replacement of stem cell pools in the body. Reports and studies have highlighted success of bone marrow transplants and direct organ transplants. Human embryonic stem cells can be triggered to differentiate into adult stem cells in order to replace the damaged stem cell pool in the body clinically in order to regenerate damaged or diseased tissues and organs (Lerou, and Daley, 2005, p. 321). Organ transplantation has been lesser appreciated as compared to replenishment of stem cells based on an immune barrier, where immune-suppression becomes necessary to prevent graft rejection (Gepstein, 2002, p. 869).
For proper clinical and medical usage of embryonic stem cells, it is important that developmental pathways of tissues within an embryo are studied and understood. Many kinds of embryonic stem cells have been characterized including insulin secreting cells, neural tissue, cardiomyocytes, endothelial cells, hematopoietic cells, hepatocytes and osteoblasts. Thereby stem cells can be used clinically in order to treat medical conditions in these tissues and cells (Lindvall, & Kokaia, 2006, p. 1095).
Derivation of Human Embryonic Stem Cells
It has been reported that cells in mammalian embryo have the capacity to regenerate into any tissue type in the body. This property is termed as pluripotency. After the occurrence of fertilization, at the stage of blastocyst, formation of hollow sphere of cells takes place that has an outer cell layer and an inner cell mass. The outer cellular layer develops into trophectoderm giving rise to placenta and other tissues. All the other tissues in the body are developed by the inner cell mass (Cai et al. 2007, p. 1231).
Generation of Cardiomyocytes from Human Embryonic Stem Cells
For clinical usage, many protocols have been used in order to trigger differentiation of human embryonic stem cells to specialized cardiomyocytes. Studies have shown that 5-aza-20-deoxycytodine has...
2002, p. 2734). However in these cases, the obtained cardiomyocytes are immature and have properties and functions related to fetal cardiomyocytes. Thereby there is a need that better protocols are developed that can help in the development and differentiation of human embryonic stem cells towards specialized cardiomyocytes rather than fetal or immature cardiomyocytes (Stojkovic et al. 2004, p. 260).
Purified Population of Cardiomyocytes
Second main fact highlighted in the studies is that in order to attain purified population of engrafted heart cells, it is important that protocols are followed that can generate purified population of heart cells. For clinical usage, purified cell population is used rather than mixed population for best results. For example, in certain clinical and medical conditions, it is important that only specific kinds of cardiomyocytes are used rather than the mixed populations. In the case of myocardial infarction and chronic heart failure, ventricular cardiomyocytes are needed, not sinus-nodal type because sinus-nodal type are more arrythmogenic and are reported to have caused morbidity in patients (Bhattacharya et al. 2004, p. 2959).
Use of Transgenes in Differentiated Cardiomyocytes
Human embryonic stem cells can generate differentiated heart cells when specific culture conditions are provided that can be used for clinical purposes that include heart failure and myocardial infarctions. In some cases, the previous studies have reported the usage of transgenes. Reports and studies have highlighted that transgenes can be a source of mutagenesis in the cells affecting the functions of cells in a negative way. The only advantage highlighted in the case of transgenic approach is that it can help in highlighting developmental pathways helping the scientists in learning about the lab culture conditions appropriate for the development of cardiomyocytes without any reliance on transgenes (Stojkovic et al. 2004, p. 263).
Use of Human Embryonic Stem Cells for Heart Conditions
In the western world, one of the main heart diseases being the main reason of mortality includes ischemic heart disease. Within the heart, irreversible cell damage is triggered based on oxygen deprivation and irreversible cell damage can cause heart cell death. The damaged cells are thereby in a need to be replaced by newer cells provided by cardiomyocytes transplantation. One of the main advantages in these cases is that permanent damage can be slowed down as newer cells can replace newer ones (Cai et al. 2007, p. 1232).
Neurological Disorders and Use of Human Embryonic Stem Cells
Some of the most common neurological disorders include multiple sclerosis, Parkinson's disease, and stroke. These diseases and conditions are caused by the loss of neurons and glial cells. In recent era, it is being hoped that a large and an inexhaustible source of neurons and glia will be provided by the stem cells in order to ensure success of therapies of the highlighted medical conditions to trigger cell replacement and neuroprotection. For this purpose, embryonic stem cells or fetal or adult stem cells from adult or fetal central nervous system are considered as best suitable. For clinical applications of these cells, it is important that specific kinds of cells and neuroprotective molecules are used (Gepstein, 2002, p. 866).
Parkinson's disease
Parkinson's disease is characterized by the gradual loss of nigrostriatal dopamine-containing neurons but in some cases it has been reported that there is a loss in non-dopaminergic neurons as well. Main symptoms of Parkinson's disease include lesser movement, rigidity, tremors, and an increased instability in postural movements. Some of the main therapies that are being used in the modern days include oral administration of L-Dopa along with dopamine receptor agonists (Lindvall and Kokaia, 2006, p. 1095). Another therapy includes the deep brain stimulation of the subthalamic nucleus. These treatments have been seen to be effective for some symptoms. There are some associated disadvantages in the case of these treatments and these include an inability to control the progression of the disease. Thereby there is a need to find an alternative that can help stop the progression of the disease and can cure the disease rather than treating some symptoms. Significant improvements in mobility and long lasting disease cure are what needs to be targeted by the help of stem cells (Bhattacharya et al. 2004, p. 2957).
Many clinical trials have been conducted where fetal dopaminergic neurons have been transplanted replacing the damaged dopaminergic neurons showing major and long lasting improvements in the patients. Thereby most promising results have been shown by embryonic stem cells having the capacity to regenerate into dopaminergic neurons. However. still a great deal of research and studies are needed in the order to study the efficiency of stem cells in innervation of the…
