Differentiation and Stem Cells

• That cellular differentiation is the process by which a cell develops more specialised functions by expressing the genes characteristic for that type of cell.

• What is a cell?
• What varieties of cell exist?
• What is a tissue? Give some examples.
• What is an organ? Give some examples.
• What is a system? Give some examples.

• The human body is made up of many specialised cells that perform specific functions .
• Specialised cells have specific structural, functional and biochemical properties
• Specialised cells arise from the differentiation of unspecialised cells during embryological development.

• Cellular differentiation is under genetic control and involves cell signalling processes
• During differentiation, genes that express proteins important for the function of that cell remain ‘switched on’.
• Once a cell becomes specialised it stops dividing and only expresses the genes are characteristic for that type of cell.
• Specialised cells with similar functions are grouped into tissues, similar tissues are grouped into organs and similar organs are grouped into systems.

•
(a) Stem cells
— embryonic and tissue (adult) stem cells.
•
Stem cells are relatively unspecialised cells that can continue to divide and can differentiate into specialised cells of one or more types. During embryological development the unspecialised cells of the early embryo differentiate into cells with specialised functions. Tissue (adult) stem cells replenish differentiated cells that need to be replaced and give rise to a more limited range of cell types.
•
(b) Somatic cells divide by mitosis to form more somatic cells. These differentiate to form different body tissue types: epithelial, connective, muscle and nerve.
•
(c) Germline cells by mitosis to produce more germline cells or by meiosis to produce haploid gametes. Mutations in germline cells are passed to offspring. Mutations in somatic cells are not passed to offspring.
• (d) Research and therapeutic uses of stem cells by reference to the repair of damaged or diseased organs or tissues. Stem cells can also be used as model cells to study how diseases develop or for drug testing. The ethical issues of stem cell use and the regulation of their use.
• (e) Cancer cells divide excessively to produce a mass of abnormal cells (a tumour) that do not respond to regulatory signals and may fail to attach to each other. If the cancer cells fail to attach to each other they can spread through the body to form secondary tumours

Some questions to think about…
•What is a stem cell?
•What are some different types of stem cells?
•What is the purpose of stem cell research?
•What are some ways that stem cells have been successfully used in medicine?
•What are some of the issues in stem cell research?
•What are some of the misconceptions that people have about stem cell research?

Stem cells are unspecialised cells that have the ability to reproduce and differentiate into a diverse range of specialised cells .

Embryonic Adult

• Embryonic stem cells are derived from an embryo about 4 –5 days old (bastocyst).
• These cells have the ability to differentiate into all of the cell types that make up an organism. (They are pluripotent)

• Adult or tissue stem cells are found in small numbers in the tissues and organs of adults and children, including the brain , bone marrow , skeletal muscle and skin .
• These cells give rise to a much more limited range of cell types and will tend to develop into cell types that are closely related to the tissue in which they are found.
(They are multipotent)
• These cells replenish differentiated cells that need replaced in the tissues in which they are found.

• Stem cells can also be taken from the umbilical cord of new babies.
• Like adult stem cells, these cells can differentiate into a limited range of specialised cells.

Induced pluripotent stem cells are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state.

• Induced pluripotent stem cells (iPSCs) are stem cells derived from non-pluripotent
(somatic) cells.
• This is done by genetically reprogramming the nucleus of somatic cell to an embryonic stem cell-like state.
• The reprogramming process ‘de-differentiates’ the cells by forcing them to express genes and factors important for defining properties of embryonic stem cells.

Somatic cells are the differentiated cells that form the different types of body tissue that exist.

Smooth muscle
B Lymphocyte
Hyaline cartilage

Ciliated epithelial cell
neutrophil
Red blood cell platelets

Cardiac muscle
Squamous epithelial cells
Nerve cells
T lymphocyte

Germline cells include the gametes and the cells that produce the gametes.

• Germline cells can divide by mitosis to produce more germline cells.
• Gamete mother cells divide by meiosis to produce gametes.

Stem cell research provides us with a wealth of information and can be studied in a variety of ways, including:
•how cell processes such as growth, differentiation and gene regulation work
•the study of diseases and their development
•drug testing
•therapeutic uses in the treatment of diseases such as leukaemia (bone marrow transplant), Hunter’s disease and heart disease
•therapeutic uses in medicine, including skin grafts for burns and stem cell grafts for cornea repair.

For example, stem cells could be turned into new bone cells and then injected into weak or broken bones.
Or they could become nerve cells that could heal spinal cord injuries.
Skin cells could replace burnt skin, and brain cells could help people who have suffered brain damage.
Stem cells could be taken from someone with heart disease and be turned into heart cells, which can gather in a dish and throb! They could then be injected back into the patient to rebuild their heart tissue and combat heart disease.

Parkinson's disease
Parkinson's is a very common disease starting with mild symptoms, a mask-like face, stiffness and tremors until sufferers eventually become immobile. It is caused by a slow deterioration of certain brain cells (neurons) and there's no cure.
Replacing the affected brain cells seems more hopeful than finding better drugs. Many people think that stem cells could be grown into new brain cells that could help to treat or even cure Parkinson's.

Using what you have learned already and adding further research, create a presentation that covers the following aspects of stem cells:
•the biology of stem cells – what is a stem cell, types of stem cells
•the potential of stem cells – details of one or two research projects involving stem cells that you have found particularly interesting, details of potential therapies
•stem cell dilemmas – explore the moral and ethical issues surrounding stem cell research (personal points of view can be expressed if desired).
You will be assessed using all three of the above criteria as well as on the overall quality of your presentation.

Criteria
The biology of stem cells
The potential of stem cells
Stem cell dilemmas
Quality of presentation
4
Covers the topic in depth with details and examples. All key terms and words have been defined.
Subject knowledge is excellent.
More than one example of stem cell research has been covered in depth. More than one example of potential stem cell therapies has been explored.
The moral and ethical issues surrounding stem cell research have been explored in detail. More than one perspective has been given for many issues.
Interesting, well rehearsed, all members of group involved, word content of slide minimal, good eye contact with audience, smooth delivery.
3
Includes essential knowledge about the topic. Subject knowledge is good.
At least one example of stem cell research has been covered in depth. Potential stem cell therapies have been covered.
The moral and ethical issues surrounding stem cell research have been covered well. More than one perspective has been given for some issues.
Relatively interesting, fairly smooth delivery. Eye contact mainly good and most members of group involved at some stage.
2
Includes most information about the topic but there are some factual errors/omissions.
An example(s) has been covered but is lacking in depth and detail of information.
Some moral and ethical issues have been mentioned but lack detail. Arguments detailed not balanced/only one perspective given.
Able to maintain interest of audience but delivery not smooth. Failed to make eye contact on some occasions.
Some group members not involved.
1
Content is minimal and there are several factual errors/omissions.
Examples are minimal.
Very few details given.
Very little detail given in this area.
Poor eye contact, not able to maintain interest of audience.
Reading from slides, delivery not smooth.

http://www.playbackschools.org.uk/program me/3144/stem-cell-research-the-issue
(15min)

Watch the clip on stem cell research and answer the following questions http://www.pbslearningmedia.org/resource/tdc02.sci.life.cell
.stemcellvid/stem-cells-seeds-of-hope/ (7min)
1. What does Dr Snyder mean when he says stem cells are "flexible and plastic?"
2. In this video what evidence convinces you that stem cells can be used to cure spinal cord injury?
3. Dr Snyder points out that there are ethical concerns, and that there is no single answer that will please everyone. Who do you think should be the ones to decide where to obtain stem cells for medical research?

• Practices using adult stem cells remain fairly uncontroversial.
• It is the use of embryonic stem cells, because of their pluripotent nature, that really excites scientists today.
• The research surrounding these types of stem cells raises many moral and ethical issues, such as the rights of the embryo.
• Many pro-life and religious groups argue that embryos have human rights and that it is wrong to create a human life simply for the purpose of scientific research.
• Opposing arguments include the fact that embryonic stem cells have the potential to discover cures for diseases for which there are currently none.

• In the UK, the laws controlling the use of embryonic stem cells remain very tight.
• Some of the conditions put on stem cell research using embryonic cells include the following:
– The research must be licensed by the Human
Fertilisation and Embryology Authority.
– Researchers must justify that the creation of an embryo is necessary and that the work could not be carried out in another way.
– Embryos over the development stage of 14 days cannot be used as this is the stage at which there is some primitive development of the nervous system.

• The use of stem cells in therapeutic treatments in the UK is currently restricted to adult stem cells.
• Whether or not embryonic stem cells can be used in the future remains to be seen.

• The laws surrounding embryonic stem cells and adult stem cells differ because while both have similar capacities in differentiation, their modes of derivation are not.
• While embryonic stem cells are taken from embryo blasts, induced pluripotent stem cells are undifferentiated from somatic adult cells

• Human reproductive cloning is illegal in the UK. As a result of the Human
Reproductive Cloning Act (2001) nobody in the UK is allowed to use cell nuclear transfer, or any other technique, to create a child.

Cancer cells do not respond normally to regulatory signals and divide excessively to produce a mass of abnormal cells.
Cancer cells have many characteristics that make them different from normal cells:
•Cancer cells continue to reproduce to produce a mass of abnormal cells (a benign tumour).
•They do not respond to normal regulatory signals that would instruct them to stop dividing when necessary.
•They lose the molecules on their surface that would normally hold them in place and can therefore be detached from their neighbours, causing the cells to spread
(malignant tumour).
Skin cancer cells (melanoma)

• It is thought that 90–95% of cancers are caused by environmental and lifestyle factors such as obesity and tobacco.
• It is estimated that 5–10% are due to genetics

• Certain strains of the human papilloma virus
(HPV) have been shown to cause cervical cancer.
• The routine immunisation programme in Scotland is for girls aged 12 and 13
(S2). There is also a oneoff, three-year catch-up programme for older girls.

Produce an information leaflet designed to answer the questions of a patient recently diagnosed with cancer. Points to consider:
• How are cancer cells different from other cells?
• What is a tumour?
• How will I know if my cancer has spread?
• What is the difference between a malignant tumour and a benign tumour?
• How will my cancer be treated?

• That cellular differentiation is the process by which a cell develops more specialised functions by expressing the genes characteristic for that type of cell.

•
(a) Stem cells
— embryonic and tissue (adult) stem cells.
•
Stem cells are relatively unspecialised cells that can continue to divide and can differentiate into specialised cells of one or more types. During embryological development the unspecialised cells of the early embryo differentiate into cells with specialised functions. Tissue (adult) stem cells replenish differentiated cells that need to be replaced and give rise to a more limited range of cell types.
•
(b) Somatic cells divide by mitosis to form more somatic cells. These differentiate to form different body tissue types: epithelial, connective, muscle and nerve.
•
(c) Germline cells by mitosis to produce more germline cells or by meiosis to produce haploid gametes. Mutations in germline cells are passed to offspring. Mutations in somatic cells are not passed to offspring.
• (d) Research and therapeutic uses of stem cells by reference to the repair of damaged or diseased organs or tissues. Stem cells can also be used as model cells to study how diseases develop or for drug testing. The ethical issues of stem cell use and the regulation of their use.
• (e) Cancer cells divide excessively to produce a mass of abnormal cells (a tumour) that do not respond to regulatory signals and may fail to attach to each other. If the cancer cells fail to attach to each other they can spread through the body to form secondary tumours