Stage 1 Biology Semester 2 2015 Biotechnology Stem Cells and Cloning

Key Ideas   Explain the origin of stem cells and how they can differentiate into all the different types of cells in the body. Understand the meaning of differentiation. State the origins of stem cells. Understand the basis for the controversy around using some types of stem cells. Explain the potential applications of stem cell therapy.

What are Stem Cells?

What is Differentiation? Differentiation is the process by which stem cells change from undifferentiated (unspecialised) cells, into a specific cell type such as like neural cells, muscle cells, brain cells, and skin cells.

Properties of Stem Cells There are two properties which define a stem cell: Self-renewal – the ability to replicate itself while maintaining the undifferentiated state. Potency: the capacity to differentiation into specialised cells.

Properites of Stem Cells 1. Self renewal Stem cell division and differentiation. A: stem cell B: progenitor cell (can only differentiate into closely related or the same cell type) C: differentiated cell

Properties of Stem Cells 2. Potency Totipotent – first few divisions of a fertilised egg and can become embryonic cell types. Pluripotent – can become almost any of the more than 200 cell types in the body Multipotent - can only differentiate into closely related cell type Unipotent - can only differentiate into the same cell type

Why do we need stem cells? One of the human body's “master cells” Replace old, dead or damaged cells Able to divide repeatedly throughout their life Can differentiate into any one of more than 200 cell types in the body

https://www.youtube.com/watch?v=_LpHo6OSmpk

3 main types of stem cells Embryonic Stem Cells (ES) Adult (Somatic) Stem Cells Induced Pluripotent Stem Cells (iPS)

What are Embryonic Stem Cells? Embryonic stem cells are cells derived from the inner cell mass of a developing blastocysts. Embryonic stem cells are undifferentiated cells from the embryo that have the potential to become a variety of specialised cell types.

Embryonic Stem Cells Embryonic stem cells are created by means of in vitro fertilization and donated for research purposes. They are harvested after 5-6 days from a cells within a blastocyst. They have the potential to change into any type of cell found in the body.

https://www.youtube.com/watch?v=-FfO_3xyrmU

Totipotent Pluripotent

Sources of Stem Cells 1. Excess IVF Eggs Excess fertilized eggs from IVF (in-vitro fertilization) clinics Tens of thousands of frozen embryos are routinely destroyed when couples finish their IVF treatment. These surplus embryos can be used to produce stem cells.

Sources of Stem Cells - 1. Excess IVF Eggs

Sources of Stem Cells 2. Somatic Cell Nuclear Transfer The nucleus of a donated egg is removed and replaced with the nucleus of a mature, "somatic cell" (a skin cell, for example). No sperm is involved in this process, and no embryo is created to be implanted in a woman’s womb.

Why use embryonic stem cells? Pluripotent – can become almost any cell type Could be used to repair just about any organ or tissue type Great potential to treat disease and save lives

Why DON’T we use embryonic stem cells? Critics say its unethical Claim that blastocysts have ‘right to life’

Adult Stem Cells Adult stem cells are found in bone marrow and can be harvested at any time in a adult person’s life. Adult stem cells have the potential to only become a limited number of specialized cells.

Adult Stem Cells The primary roles of adult stem cells in a living organism are to maintain and repair the tissues in which they are found. Some scientists now use the term somatic stem cell instead of adult stem cell.

Umbilical Cord Blood Stem Cells Pluripotent adult stem cells are rare and generally small in number. They can be found in a number of tissues including in the blood of the umbilical cord during and shortly after delivery.

Why use adult stem cells? Multipotent – can become a limited range of cell types Can potentially be used to treat a range of disease and injury Harvested and grown with donor consent No blastocysts (early stage embryos) are destroyed

Induced Pluripotent Stem Cells (iPSC) In the last couple of years a potential alternative to either embryonic stem cells or adult stem cells has been developed. These cells are called iPSC. They are generated from differentiated cells (commonly fibroblasts). These cells are de-differentiated or reprogrammed by modifying 4 genes using viral vectors. The resultant cells seem to have most of the characteristics of SC.

Potential applications of stem cells

Stem Cell Therapies Stem cell treatments or therapies are a type of intervention strategy that introduces new adult stem cells into damaged tissue in order to treat disease or injury.

Stem Cells to Treat Leukemia Leukemia is a cancer of white blood cells, or leukocytes. Like other blood cells, leukocytes develop from somatic stem cells. Mature leukocytes are released into the bloodstream, where they work to fight off infections in our bodies.

Stem Cells to Treat Leukemia In a bone marrow transplant, the patient's bone marrow stem cells are replaced with those from a healthy, matching donor. To do this, all of the patient's existing bone marrow and abnormal leukocytes are first killed using a combination of chemotherapy and radiation. Next, a sample of donor bone marrow containing healthy stem cells is introduced into the patient's bloodstream. If the transplant is successful, the stem cells will migrate into the patient's bone marrow and begin producing new, healthy leukocytes to replace the abnormal cells.

Stem Cell Therapies Medical researchers anticipate that adult and embryonic stem cells will soon be able to treat : cancer,  Type 1 diabetes mellitus, Parkinson's disease,  Huntington's disease, Celiac Disease,  cardiac failure,  muscle damage and neurological disorders, and many others.

Key Ideas   Explain the origin of stem cells and how they can differentiate into all the different types of cells in the body. Understand the meaning of differentiation. State the origins of stem cells. Understand the basis for the controversy around using some types of stem cells. Explain the potential applications of stem cell therapy.

Task: Create a table with the following information Type of Stem Cell Summary of stem cell - location Application example Pros Cons

Infusing stem cells into the brain may help boost recovery after a stroke, according to a pilot study by Imperial College London. Scientists believe the cells encourage new blood vessels to grow in damaged areas of the brain. They found most patients were able to walk and look after themselves independently by the end of the trial, despite having suffered severe strokes.

Ethical Issues – controversy around stem cells Harvesting human Embryonic Stem Cells destroys a 4-7 day old embryo (blastocyst) that has the potential to become a human baby if implanted into a uterus. Some people say that it trivializes life and the cost is too great. Some people say that the benefits of curing diseases far outweighs the ethical considerations. In some types of research eggs from women are needed. Should women be able to volunteer or sell their eggs?