Embryonic Stem Cells

An embryonic stem cell is a cell derived from the earliest stages of a embryo which is capable of differentiating into any cell type in the organism. Embryonic stem cells are able to differentiate into any cell type because that is what they are used for in the embryo.

Overview of embryonic stem cells

As the embryo grows and divides, the generalising cells must become increasingly specific as they divide. This eventually creates the different organs, tissues and systems of an organism. Embryonic stem cells are totipotentwhich means that they can divide into any other cell type within an animal. This is a process known as cell differentiation.

Once sperm cells reach an egg cell (oocyte), the fertilisation and the DNA of the two cells is merged into a single nucleusin a single cell. This is the zygote and technically it is an embryonic stem cell because as it divides it will differentiate into all the cells of the body.

This cell and the first divisions of this cell have the ability to become any type of tissue. This means that they have the capacity to become a complete organism. Identical twins, for example, develop from the same zygote that accidentally separates when it begins to divide.

What are embryonic stem cells used for?

In medicine and research, scientists use cells embryonic stem cells pluripotent. These cells do not have the capacity to develop into a full organism. Rather, they are directed by signals from the early embryo that tell them which cell type to differentiate into. Scientists prefer these cells for many reasons.

First, they can be stored and maintained more easily. Totipotent cells tend to differentiate quickly and immediately try to develop into an organism. Pluripotent cells are waiting for a signal to divide and can be maintained for longer periods. In addition, because pluripotent cells are simply waiting for the right signals to tell them what type of cell to become, they can be easily integrated into medical applications where new tissue must be grown.

Embryonic stem cells in medicine

The use of embryonic stem cells is a very new form of medicine. The cause of many degenerative diseases and physical injuries has been understood for decades. Tissue damage is the root cause of many of these ailments, and scientists have long been searching for a method to develop tissues that do not easily repair themselves. Because an embryonic stem cell is pluripotent and can become almost any cell in the body, these cells have long been studied for their possible use in medicine.

Since the late 1950s, scientists have been trying various methods of growing tissue with an embryonic stem cell. The first clinical trials were conducted in the late 1960s, but not much progress has been made. President Bush imposed a moratorium on the use of federal funds for stem cell research, which was finally lifted by the Obama administration in 2009. European countries have also faced an uphill battle to fund stem cell research. However, with advances in science came new discoveries that allowed for a more ethical harvesting of an embryonic stem cell. The first medicinal stem cell treatments were in 2010.

Nerve cell regeneration

From a medical point of view, the embryonic stem cell is limited in its current uses, although many new applications are in the pipeline. Current treatments focus on the replacement of tissue damaged by injury or disease. Of these, the first treatment approved by the FDA for testing was to replace damaged tissue in spinal injuries.

Since nerve cells rarely regenerate, an embryonic stem cell can be used to replace the damaged nerve and restore function. For someone with a spinal injury, this means being able to walk again. For a blind person, it could mean being able to see again. While the treatment is still new and success is limited, it has shown some positive results.

As a research tool

Still, other medical breakthroughs are achieved with embryonic stem cells, although these do not come as direct medical treatments, but rather as the knowledge that stem cells provide us with. As an embryonic stem cell differentiates into its target tissue, scientists can study the chemicals and methods it uses to do so. Scientists can also alter the genome of these cells and study the effects that different mutations have on a cell’s function.

Between these two paths of discovery, scientists have gathered a lot of information about how and why cells differentiate and divide. With these tools, scientists are getting closer to methods that would allow them to turn a normal cell into a pluripotent stem cell. These are known as induced pluripotent stem cells. They are not embryonic stem cells, because they are not derived from an embryo. This process could not only repair injuries and ailments, but could reverse ageing and prevent death.

On a less dramatic and grander scale, these methods are also being used to cure common diseases, such as diabetes. By learning how embryonic stem cells become pancreatic cells and secrete insulin, scientists are learning methods to turn other tissues into insulin-secreting tissues. This could help cure diabetes, often caused by the destruction of insulin-producing cells. If they were replaced with stem cells or other cells were induced to become pancreatic cells, the disease could be cured.

Other diseases, such as cystic fibrosis, fragile x syndrome and other genetic disorders are being studied in embryonic stem cells. Not only can many cells be created, but they can also differentiate into different cell types. In this way, a scientist can create a picture of the disease from snapshots of each cell type and understand exactly how the disease is affecting a person.

How are embryonic stem cells collected?

While there was once concern that embryonic stem cells would be harvested without the consent of unknown women, the vast majority are now ethically harvested. at fertilisation clinics in vitro. In these clinics, in order to achieve a successful pregnancy, many eggs must be fertilised. Only one is implanted and, with the woman’s consent, the rest can be used to collect embryonic stem cells. To do this, scientists extract some embryonic stem cells from an embryo when it is just a small ball of cells. This can be seen in the picture below.

A harvested embryonic stem cell is placed in a Petri dish with nutrients and allowed to divide. Without any sign of the embryo, the cells remain pluripotent. They continue to divide, fill a dish, move to many more dishes and continue to grow. After 6 months of this, they are considered a successful pluripotent embryonic stem cell line. They can then be used to study diseases, used in treatments or genetically manipulated to provide models of how cells function.

To prove that these cells are indeed pluripotent stem cells, they are injected into mice with depressed immune systems. The mice must have depressed immune systems, or their bodies would naturally reject human tissue. Once implanted into the mice, the successful pluripotent cells will form a small tumour called a teratoma. This small tumour has different tissue types and demonstrates that the cell line remains pluripotent and can differentiate into different cell types.

The difference between adult and embryonic stem cells

There are also other types of stem cells, which should not be confused with an embryonic stem cell. Embryonic stem cells are derived from embryos. There are also adult stem cells, umbilical cord stem cells and foetal stem cells. These stem cells are not only sometimes more ethically challenging, but they are only multipotentwhich means that they can only develop into a small range of cell types.

Examples are the stem cells of the blood umbilical cord bloodwhich have been used in medical treatments to treat various blood diseases and weakened immune systems. Stem cells in umbilical cord blood can differentiate into almost any blood or immune cell type, making them multipotent. However, this limits their use in other areas of medicine.

There are also adult stem cellswhich survive in various organs of the body. These cells are also multipotent and can only differentiate into the tissue types in which they are found. A common use of adult stem cells is the bone marrow transplantation. In this procedure, a healthy donor must have bone marrow removed from his or her bones. Bone marrow is a blood-like substance inside large bones that creates blood cells and immune cells.

Cancer patients, who have undergone radiation and chemotherapy, lose most of their immune cells and become immunosuppressed. Often, a bone marrow transplant is needed to replace these tissues. The new stem cells begin to produce new immune cells, which help the patient recover and fight infection and disease.

Discover our blog post where we talk about stem cell types.