[Title of presentation]

EB3222Cell and Tissue Culture

Faculty

1

7. Stem cellsLearning outcomes:Explain the basic concepts of stem cellsExplain the usage of stem cells in therapyEthical issues

FacultyBasic concepts of stem cellsStem cells are cells that do not have a specialized functionThey are an immature kind of cell that still has the potential to differentiate into many different kinds of cell. This capacity to both proliferate and form different types of cells makes them ideal for replacing tissue that is lost. Hence, they are good for the development of regenerative medicine.

FacultyStem cells differ from other cells in the body in three main ways:Stem cells are unspecialised. They have not developed into cells that perform a specific function.Stem cells can differentiate. That is, they can divide and produce cells that have the potential to become other more specialised cell types or tissues. These new cells and tissues are used to repair or replace damaged or diseased cells in the body.Unspecialised stem cells are capable of self-renewal. Stem cells are able to divide and produce copies of themselves which leads to self renewal. Once a cell has become specialised (has differentiated) it has a very limited capacity to produce new cells, and then only cells of the same type. Thus, if a muscle or blood cell is damaged it cannot replace itself.

FacultyBasic concepts of stem cells: Types of stem cellsThere are several types of stem cells including:Totipotent stem cellsPluripotent stem cells. Multipotent stem cells. Unipotent stem cells.

Faculty

FacultyA fertilized egg is considered totipotent, meaning that its potential is total; it gives rise to all the different types of cells in the body. Pluripotent stem cells have the potential to form any cell except extra-embryonic tissue such as placentaMulti-potent stem cells could only differentiate into limited types of cells. Multi-potent stem cells could be found in adults. Unipotent stem cells could only differentiate into a single type of cells.

Faculty

FacultyBasic concepts of stem cells: Types of stem cells used in researchThere are several types of stem cells commonly used in research, including:Embryonic stem cells. Embryonic germ cells. Adult stem cells

Embryonic stem cells and embryonic germ cells are pluripotent while adult stem cells are usually multipotent.

FacultyBasic concepts of stem cells: Embryonic stem cellsThe embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst. The blastocyst includes three structures: the trophoblast, which is the layer of cells that surrounds the blastocyst; the blastocoele, which is the hollow cavity inside the blastocyst; and the inner cell mass, which is a group of approximately 30 cells at one end of the blastocoel.

Faculty

Faculty

FacultyBasic concepts of stem cells: Embryonic germ cellsEmbryonic germ cells are derived from the part of a human embryo or fetus that will ultimately produce eggs or sperm (gametes). They are found at 6 to 9 weeks of gestation when the embryo is developing into a fetus.Little research is now performed using this type of cells because they do not appear to be as versatile as embryonic stem cells.

Faculty

FacultyBasic concepts of stem cells: Adult stem cellsAdult stem cells/somatic stem cells are more specialized than embryonic stem cells. They are found in the majority of tissues and organs in our body and generate the mature cell types within that tissue or organ. They have a restricted ability to produce different cell types and to self-renew

FacultyAdult stem cells have been identified in many organs and tissues. One important point to understand about adult stem cells is that there are a very small number of stem cells in each tissue. Stem cells are thought to reside in a specific area of each tissue where they may remain quiescent (non-dividing) for many years until they are activated by disease or tissue injury. The adult tissues reported to contain stem cells include brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin and liver.Adult stem cells are formerly regarded as unable to differentiate into other types of cells e.g. hematopoietic stem cells could not differentiate into muscle cells.

Faculty

FacultyHowever, a number of experiments over the last several years have raised the possibility that stem cells from one tissue may be able to give rise to cell types of a completely different tissue, a phenomenon known as plasticity. Examples of such plasticity include blood cells becoming neurons, liver cells that can be made to produce insulin, and hematopoietic stem cells that can develop into heart muscle. Therefore, exploring the possibility of using adult stem cells for cell-based therapies has become a very active area of investigation by researchers.

Faculty

FacultyUsage of stem cells in therapyBlood-forming stem cells in bone marrow called hematopoietic stem cells (HSCs) are currently the only type of stem cell commonly used for therapy. Doctors have been transferring HSCs in bone marrow transplants for over 40 years. More advanced techniques of collecting, or "harvesting", HSCs are now used in order to treat leukemia, lymphoma and several inherited blood disorders.

FacultyPotential disease that could be cured with stem cells therapy includes:Type 1 diabetesParkinsons diseaseCardiac repairAnd many more

FacultyUsage of stem cells in therapy: Type 1 diabetes and Parkinsons diseaseType 1 diabetes and Parkinson's disease occur due the loss of a relatively small amount of tissue. In juvenile diabetics, the insulin-producing cells of the pancreas are destroyed by the immune system. In Parkinson's disease the dopamine-producing cells of the brain are destroyed no-one really knows why. Researchers have already had some success treating patients by replacing the lost tissue with material from aborted fetuses (in the case of Parkinson's disease) or donated pancreases (in the case of type 1 diabetes).

FacultyUsage of stem cells in therapy: Cardiac tissue repair

FacultyProblems of stem cell therapyThere are several problems posed that needs to be solved before stem cell therapy could be well developed and used as regular therapeutic options:Immune rejectionCancer inductionEthical issues

FacultyProblems of stem cell therapy: Immune rejectionPatients receiving embryonic stem cells or adult stem cells sourced from another individual would probably be treated in much the same way that organ transplant recipients are treated. The stem cells would be matched to the individual patient and anti-rejection drugs would be used. However, patients receiving brain stem cells may not need these drugs as the brain seems to get away with less surveillance by the immune system than other parts of the body.

FacultyThere is a type of stem cell known as a mesenchymal stem cell that seems to evade detection by the immune system. Everyone carries mesenchymal stem cells in their bone marrow; they normally give rise to cartilage, bone or muscle cells. If these cells do not trigger immune rejection they could be used in future treatments of bone and joint diseases or repair heart muscle damaged during a heart attack

FacultyIf patients provide their own stem cells, then of course immune rejection is no problem. Leukaemia patients routinely rely on their own stem cells. A reserve of their blood-forming stem cells (found in bone marrow, but different from mesenchymal stem cells) is stored away. After cancer therapy, which destroys stem cells, patients rely on the stored stem cells to rapidly restore their red and white blood cell counts to normal. Burnt patients also rely on the stem cells present in a tiny square patch of skin to seed the growth of metres of new skin in the culture dish.

FacultyProblems of stem cell therapy: Cancer induction Any stem cell, adult or embryonic, has the tendency to give rise to cancer. As stem cells could grow indefinitely, if they are not induced to differentiate, they would keep on growing until they form a lumptumor. All stem cell therapies have to be properly tested to make sure that the stem cells injected into the patients would not cause cancer growth.

FacultyProblems of stem cell therapy: Ethical issuesSome people oppose embryonic stem cell research on religious grounds. Many take the view that from the moment of conception an embryo is a human being with a soul, and that using these embryos is like dismembering a person. But not all religious people take this view. Some believe that an individual human being does not truly arise until the embryo has implanted into the wall of the mother's womb at around 14 days. According to that view, these embryos are too primitive to be to considered human beings and so it is not unethical to use them for life-saving research, especially if they are to be thrown away in any case.

Faculty

Thank you

Faculty