Stunning Science - Issue 1

First Embryo Grown Outside the Womb Without Egg or Sperm Cells

Written By Lauren Smith and Michelle Johnson 

At the beginning of March, the University of Cambridge released an article explaining how they had grown an artificial mouse embryo from stem cells in their laboratory.  The embryo was able to develop for seven days outside of the womb. A mouse’s pregnancy lasts around 20 days so this was around one third of the way through the mouse pregnancy. This is equivalent to around six months in a human pregnancy. This new process of creating artificial embryos without the use of sperm or egg cells is opening many new doors for scientific research into embryology. Until very recently, embryos (‘unborn babies’) have only been able to be ‘created’ with both a mother and a father’s gamete (sex cell - sperm and egg). Scientists from Cambridge University mixed two types of stem cells together to form an embryo. This was possible because embryonic stem cells can turn into any type of specialized cell: muscle cells, red and white blood cells, skin cells and more. 

So, what are stem cells? 

Every cell in the human body has become specialised in order to carry out a certain job. For example, muscle cells are specialised and adapted to the job they need to carry out.  Unlike other cells, they are able to contract to allow movement; they can also create much more energy than other cells as they contain many mitochondria (mitochondria are structures in the cell where energy is created). This allows us to move and exercise without running out of energy. Our red blood cells are also specialised. They have a thin cell membrane. A cell membrane is a thin sheet- like structure surrounding the cell. It holds the cell together and controls what is let in and out. This means that oxygen can be delivered quickly to other cells, as it only has to travel a short distance. Red blood cells also have no nucleus (the organelle that controls the cell’s activities and contains genetic information); this creates more room for haemoglobin, the substance that carries the oxygen in the cell. Red blood cells and muscle cells are just two examples of the hundreds of uniquely specialised cells in the body. 

Once specialised, all animal cells, including human body cells, are unable to re-specialise or to become unspecialised again. Embryonic stem cells are cells that have the potential to turn into any type of cell, as they are not yet specialised. Indeed, they are unspecialised, growing, actively dividing cells. Embryonic stem cells lose the ability to turn into any type of cell at an early stage of development. They are found in embryos, placentas and umbilical cord blood. It was recently discovered that there are adult stem cells in the human body. These stem cell’s abilities are limited and they can only produce certain types of specialised cells. For example, adult stem cells in bone marrow can produce different types of blood cells. Their specialisation abilities are limited, compared to embryonic stem cells. 

There has been lots of research using embryonic stem cells. Scientists want to learn how to force them to specialise in certain ways. For example, embryonic stem cells could be used to treat dementia by specialising to create the right cells to fix the brain. This is very controversial though as embryos have to be killed in order to obtain the embryonic stem cells for research and medical treatment. 

As well as stem cells, trophoblastic cells can be found in developing embryos. Trophoblastic cells form the placenta, a flat, circular organ that nourishes the embryo through the umbilical cord. These cells are another type of stem cell and are very important in the development of the foetus, in the womb and in the experiment. 

At Cambridge University, scientists were able to use embryonic stem cells to create an artificial mouse embryo. A foetus is normally formed when sperm cells and egg cells’ nuclei are joined. This then produces something called a zygote. A zygote is a cell that will go on to divide and develop into the embryo. However, in this experiment, there was no use of either specialised cells. Instead, the scientists mixed the trophoblastic cells with embryonic stem cells in a special gel matrix. They then left the artificial embryo to culture for seven days. Surprisingly, the cells had organised themselves into two anatomical (bodily) sections and amazingly, after four days, the embryo contained the different body tissues that a normal mouse would have. 

How to grow an embryo using stem cells:

  1. Firstly, allow the embryonic stem cells to reproduce and grow. In a separate petri dish also allow trophoblastic stem cells to reproduce and grow in the same way. 
  1. Once these cells have grown, combine them in a special gel that mimics the conditions in the womb. 
  1.  Eventually these cells will begin to communicate and develop together, forming the embryo. This is how they would behave together and interact in the womb. 
  1. As the cells continue to develop you will be able to study the perfectly replicated structures that are formed during normal embryonic development. The embryo begins as a ball, which then elongates. Then the cells form a central cavity and begin developing a cell layer called mesoderm. This layer goes on to form bone and muscle. 
  1. Research is currently underway to find the right stem cells to add that are required to develop ectoderm, the layer of cells that forms the skin and nervous system, and endoderm, the layer of cells that creates the internal organs.

 

 

 

Professor Zernicka-Goetz, who is working on the project at Cambridge, explained what the artificial embryo she created was like:“They are very similar to natural mouse embryos. We put two types of stem cells together - which has never been done before - to allow them to speak to each other. We saw that the cells could self organise themselves without our help”. 

This process is allowing scientists to research the development of embryos in great detail. It also solves the ethical problem of using real human embryos and ending lives for science. Artificial embryos can be mass-produced for scientists to use. However, the ethical issue of killing embryos for the embryonic stem cells remains. This has created many controversial pros and cons. Although lives are being taken, future lives may be saved because of this research, so it seems acceptable. This research will go on to help scientists understand why people have miscarriages at this stage in embryogenesis (the embryo’s development), which will then go onto reduce the rate of miscarriages and improve in-vitro fertilisation (IVF) rates too. 

 

 

 

As well as reducing the rate of miscarriages, this new opportunity is opening new windows for research into embryo development just before implantation in the womb. This is because scientists now have the ability to see a 3D image of the structure of a foetus. It has never been possible to carry out this in-depth research before as the embryo is too tiny to observe with ultrasound during the early stages of development. Professor Zernicka-Goetz, has explained how it is unlikely the embryo will be able to develop much further outside of the womb, as it will soon need the supply of nutrients and oxygen from the mother. She also went on to say how scientists are not planning on growing whole animals and humans in the laboratory. They just want to be able to study the embryo. The university want to try carrying out this experiment again but with human stem cells, rather than mouse cells. This could open up even more doors for research and further developments of embryology knowledge. 

This is an amazing new experiment that is enabling scientists to complete in depth research they never before thought was possible. Hopefully, in the future, IVF rates will be higher and miscarriages may be preventable. Also maybe one day scientists will find a way to develop embryos further in the laboratory and to create whole human babies outside of the womb. There are lots of new possibilities that have been created after this successful experiment was carried out and the future of embryology research looks very positive! 

 

 

Glossary

Embryos-

An embryo is an unborn or unhatched offspring in the womb, developing. It is not the same as a foetus. A baby is called an embryo during the period from approximately the second to the eight week after fertilization.

Stem cells-

            Stem cells are cells that are unspecialized. They are generally found in an embryo but can be also found in adult tissue.

Gestation period –

            The gestation period is a period of time that a foetus is developing in the womb. The gestation period for each animal is different.

Womb-

            The womb is an organ in the lower body of a woman or female mammal. It is where offspring are conceived. It is also called the uterus. 

Sperm cell-

            Sperm is the male reproductive cell. It is essential for fertilization. It has a tail and an oval shaped head.

Egg cell-  

            The egg cell, or ovum, is the female reproductive cell. It is a circle shape and only found in woman.

Embryology-            

Embryology is the study of embryos and their development in biology and medicine. However, embryologists only study the embryo during the first eight weeks of development.

Gamete-

            A gamete is another name for sex cell

Specialized cells-   

            A specialized cell is a cell that has a special function/job. They are crucial to human survival. Specialized cells have special adaptations in order to do its job.

Mitochondria-

            An organelle found in many cells. It is where aerobic respiration takes place. They release energy in a biochemical process.

Cell membrane-

            A semipermeable ‘coating’ surrounding the cytoplasm of a cell. It allows gases and other things into and other of the cell.

Nucleus-

            The nucleus contains DNA and controls all the activity that takes place in the cell. It is the brain of the cell.

Haemoglobin-

            Haemoglobin is a protein in red blood cells. This protein helps red blood cells carry oxygen around the body. 

Unspecialised-

            A cell is unspecialised when it does not have a function or task. Usually, unspecialised cells are stem cells.

Placentas-

            The placenta is an organ that develops in a women’s uterus during pregnancy. The placenta provides oxygen and nutrients to the growing baby and removes waste products from the baby’s blood.

Umbilical cord-

            The umbilical cord contains one vein. It carries nutrient-rich blood, carrying oxygen, to the baby. The umbilical cord also has two arteries that carry deoxygenated blood away.

Trophoblastic cells-

            Trophoblastic cells are cells that form the outer layer of a very young embryo. They provide nutrients to the embryo and develop into a large part of the placenta.

Mesoderm cells-

            The mesoderm cells are the cells that develop into the heart tissue, bones and lungs. It is one of the three primary layers in the vey early embryo. The other two layers are the ectoderm and endoderm.

Foetus-

            A foetus is an unborn or unhatched vertebrate in the later stages of development, when the main features of the embryo become visible.

Zygote-

            A diploid cell (a cell with 46 chromosomes) that is created by the fusion of two gametes. Also known as a fertilized ovum.

Anatomical-

            Anything anatomical is relating to bodily structure or anatomy.

Petri dish-

            A petri dish is a shallow, circular, transparent dish with a flat lid. Petri dishes are used to culture microorganisms. 

Ectoderm-

            Ectoderm is the outer most layers of cells or tissue of an embryo in very early development. They form the skin and nervous system.

Endoderm-

            Endoderm is the innermost layer of cells or tissues of an embryo in very early development. They create the lining of the gut and other similar structures.

Miscarriages-

            A miscarriage is the surprising loss of a foetus before it is born.

Ultra sound-

            An ultra sound is a scan, especially of one of a pregnant woman to examine the foetus.
IVF-

            IVF means In Vitro Fertilization. It is commonly used assisted reproductive technology.  

Information Sources

 

 

  • Year 9 lessons, Ribston Hall High School.