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The research on stem cells started 30 years ago. This is where scientists derive embryonic stem cells from early mouse embryos. And until few years back, scientists manage to find a way to derive human embryonic stem cells and breed it in the laboratory. This discovery is led by the first breakthrough of finding the mouse embryonic cells. The newly found human stem cells are used for reproductive purposes. In additional, the unused stem cells of human are being sent for further research. In 2006, scientists had another important discovery. Scientists are now able to make specialized adult cells back to its stem cells functions. These kind of cells are called induced pluripotent stem cells.(IPSCs) We will talk about this later on.
Stem Cells are popular topic recently where scientists all around the world are discussing. Stem Cells are known to people around the world as new cure or treatment for incurable diseases or complicated diseases. These new discovery and ongoing research are said to be very useful to medical sectors in the future. However, not many people really know what stem cells are all about. Basically, there are two types of stem cells. They are embryonic stem cells and non-embryonic stem cells.
Embryonic stem cells
So what are embryonic stem cells? From the word 'embryonic', we can derive they are unspecialized cells that are present in a 3 to 5 day old embryo. This embryo is also known as blastocyst. The blastocyst includes three structures. The blastocoel, a hollow cavity inside the blastocyst;The trophoblast, a layer of cells that surrounds the blastocyst; and the inner cell mass which is a group of cells at one end of the blastocoel that develop into the embryo proper. This means that these cells are only present on humans when a particular human baby is born. After a period of time, these cells will become specialized into other important functions to become cells such as brain cells, heart cells, lungs cells and so on. This process is called differentiation. This is where cells become specialized for a specific function. These different specialized cells then come together with other same specialized cells to form tissues. Different groups of same types of tissues then come together to form an organ. The different organs then form different systems of the body which then form the body. Here, we see that from some small and simple stem cells can eventually form a huge and complex organism. These impressive and potential cells are therefore worth researching and find out their other uses which may come out with new therapies and cures.
Embryonic stem cells in laboratory
Scientists now are able to grow stem cells in laboratory. This is known is cell culture. Scientists isolate the stem cells by taking the inner cell mass of the stem cells and plant them into a plastic laboratory culture dish which contains a nutrient broth that allows the stem cells to grow. The nutrient broth is also known as the culture medium. With all the requirements for the cells to grow present, the cells will divide and spread all over the surface of the dish. There is an inner surface of the cultural dish is coated with mouse embryonic skin cells. These mouse embryonic skin cells act as a sticky surface for the inner cell mass cells to attached itself to it. In additional, this mouse cells also provides nutrients into the cultural medium. Therefore, scientists also call it the feeder layer. What makes it a better support for the inner cell mass cells to divide is the mouse cells will not divide or reproduce after being treated by scientists. This treated mouse cells will then not disrupt the inner cell mass cells to grow but fully boost and support it to grow. However, scientists hope they can grow inner cells mass cells without this feeder layer. This is because there is a risk that viruses or other macromolecules in the mouse cells may be transmitted to the human cells. This will then affect the growth of the cells and the whole experiment will fail.
The process of producing embryonic cell line is somewhat inefficient. Lines are not produced each time inner cell mass cells are placed into the cultural dish. However, if the inner cells mass cells are able to survive and grow as planned, divide normally and multiply enough to crowd the whole cultural dish, they will be extracted gently and replant into many fresh cultural dishes. This process is called replating or subculturing. This process continues repeatedly for several months until a cell line is formed. This is where the original few cells developed and yields into millions of identical cells. Embryonic cells that are proliferated for this long period of time without developing themselves into specialized function (differentiation) are said to be pluripotent. Moreover, if they are also genetically stable, they are also known as embryonic stem cell line.
Ways to stimulate embryonic stem cells to differentiate
For many years, scientists having trying to find ways to manually stimulate embryonic stem cells to different specialized cells they want. Their years of hard work have paid off a little. They now found ways to stimulate stem cells to specialized cells such as cells that produce insulin. With this discovery, patients with diabetes condition can be under control with the injection of insulin. Insulin will reduce the glucose level in the blood. Another discovery is scientist is now able to specialise stem cells into neurons that produces dopamine and serotonin. With this ongoing research and countless experiments going on to find other 'recipes' of specialising stem cells, many new cures and treatments will be created. Before I elaborate further, let's look at the diagram below that illustrate the process of specialising the two cells mentioned above.
Directed differentiation of mouse embryonic stem cells. This figure is a flow chart showing the steps scientists take to isolate and differentiate mouse embryonic stem cells. A mouse blastocyst is shown in the upper left, with its inner cell mass (ICM) labeled. Arrows indicate removal of the ICM and plating in a tissue culture dish, labeled as "undifferentiated embryonic stem cells." The next arrow indicates the passage of time and shows that the cells in the plate have now become embryoid bodies. From this culture dish, an arrow indicates that the next step is "induce initial differentiation and select precursors." Next, two arrows show two possible fates, and the label underneath indicates that the scientists "expand precursors." The two possible precursor types are "neuronal precursors" or "pancreatic precursors." The final step indicates "complete differentiation to generate functional cells." The bottom left shows a fluorescently labeled microscope image of "dopamine- and serotonin-secreting neurons" and the bottom right shows a fluorescently labeled microscope image of "insulin-secreting pancreatic islet-like clusters." (© 2001 Terese Winslow)
With suitable and under controlled conditions of culture dish, embryonic stem cells are allowed to remain undifferentiated. However, if they are allowed to grow and clump together, they will differentiate unexpectedly. They will differentiate themselves into other different cells researchers did not plan. Examples are muscles cells, brain cells etc. Although these prove that these cells are in good conditions, healthy, this is not the most efficient way to produce specific types of cells. Therefore, researchers wish to produce and generate specific types of cells such as heart muscle cells, brain cells, nerve cells for example but not differentiate these cells randomly and result in mass varieties of cells. In order to achieve this, researchers does various experiments. Each of these experiments changes one different variable that is different from other experiments. The rest of the variables are remained unchanged. Researchers change variables such as the chemical composition of the culture medium, alter the surface of the culture dish, or modify the cells by inserting specific genes.
If researchers are able to find out ways to obtain different specialized cells, these ability will help to treat certain diseases in the future. With this breakthrough of this sector of medical science, terminal or untreatable diseases such as Parkinson's disease, diabetes, traumatic spinal cord injury, Duchenne's muscular dystrophy, heart disease, and vision and hearing loss no longer incurable.