(Almost) Everything About Stem Cells
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For many years, stem cells have been the main talking point in discussions about the future of medicine. But what exactly are stem cells, how are they obtained and how do we hope to benefit from them?
Our body is, indisputably, a miracle of nature. It consists of many small cells: blood cells, skin cells, fat cells, and approximately 200 other cell types. Researchers estimate that a mature human body consists of 30 trillion cells – to illustrate, that’s a number with 13 zeros. All these cells originate from a single cell: the fertilised egg. The egg is a stem cell, or rather, the mother of all stem cells: after all, it forms our entire organism.
Stem cells are cells that haven’t differentiated yet. This means they have not yet been assigned a certain function within the body. On first glance, stem cells differ very little from normal body cells. However, they have two very special talents: they can divide and differentiate. They can therefore create exact copies of themselves.Furthermore, they can specialise into a defined cell type, thus forming or repairing tissue.
There are different types of stem cells: totipotent, pluripotent, embryonic… This diversity – and all the various names – may seem confusing at first, but the differences can basically be determined by two characteristics of stem cells: their respective development potentials and their origin. There is a close relationship between the two.
The cell with the greatest development potential is the fertilised egg. It can develop a human being, which is why it is described as totipotent. This cell is a real all-rounder. The next in line are pluripotent stem cells. They can develop every kind of human tissue, but not an entire organism. In turn, multipotent stem cells can create different cell types, but they are limited to a specific type of tissue. They are therefore still capable of a lot, but have limitations. Last but not least, there are oligopotent and unipotent stem cells. These can merely differentiate into a few or even a single type of cell. In addition to this, stem cells are classified according to their origin. All human beings carry adult stem cells in their body into old age. They are either multipotent or oligopotent and can be found in many organs of our bodies. Their main task is to maintain or repair tissue that is under sustained stress. For example, adult stem cells replace our skin, form new blood cells, and structure our bones. They are truly tireless workers, replacing the millions of cells that die in our bodies every second. Using adult stem cells for therapy hardly ever leads to complications. Sadly, they also have some decisive disadvantages. They are often difficult to extract, multiply inefficiently, and aren’t suitable for every task.
Embryonic stem cells are a different matter altogether: they are pluripotent, which means they can produce all kinds of tissue and develop every organ. In addition, they grow very rapidly into large amounts of cells. From this point of view, they are fairly well suited for research and medicine. However, their use on humans is restricted by law and ethically controversial.
After all, one requires embryos to obtain such cells. This tissue could – in theory – develop into a human being. But where does human life begin? And should it be allowed to use excess embryos, which are generally destroyed after successful artificial inseminations, to develop cures for serious diseases?
These controversial questions could be avoided with so-called induced pluripotent stem cells (iPS). iPS are produced artificially in a laboratory. The source materials for this process are the matured body cells of an adult – skin cells, for example. These are then reprogrammed into a very early, quasiembryonic state by utilising various techniques.
Et voilà: this ‘reset’ creates iPS that can, just like embryonic stem cells, transform into almost every cell type. Is this the perfect solution? Unfortunately no, as we still don’t know all the risks that this reprogramming can cause.
Speaking of risks, the greatest strength of embryonic, as well as induced pluripotent stem cells is their ability to divide, multiply, and transform into various cell types. This strength is also their greatest weakness. Once injected into a human body, the cells could start proliferating uncontrollably, thus potentially causing tumours to grow.
Magic weapon against diseases
Scientists around the world are working very hard to minimise these risks. Stem cells have the promise to work wonders in curing many diseases: Parkinson’s, cancer, heart attacks, agerelated blindness, etc. The list is almost endless. The hope is that the diseased cells can be replaced with healthy ones. A similar process has been successfully used in the clinics for many years in the battle against leukaemia.
Spinal cord researchers also harbour great hopes for stem cells. Spinal cord injuries are extremely complex: inflammations occur, nerve tissue is lost, and scars that prevent the growth of nerve cells form. Stem cells could help solve all these problems. They could replace dead tissue, produce new nerve cells, and create a regenerative environment.
NOTE FOR PATIENTS!
In the field of fundamental research, scientists have already achieved some promising results involving stem cells. Whether the use on patients is safe enough is currently being tested in various clinical trials. However, clinically approved stem-cell therapy for patients suffering from spinal cord injuries is not yet available, even if it is promised on occasion. For helpful information on the topic, download the ‘Guide for Experimental Therapies’ HERE.