Stem Cells

Question 1

Describe unique features of stem cells

Answer 1

1. Can remain undifferentiated and unspecialised for a long period of time
2. Capable of dividing indefinitely and self-renewal by mitosis
3. Ability to undergo differentiation, giving rise to specialised cell types upon appropriate receiving molecular signals

Question 2

Name different potencies and an example for each potency

Answer 2

1. Totipotent: Zygotic stem cells
2. Pluripotent: Embryonic stem cells
3. Multipotent: Blood stem cells

Question 3

Describe features of zygotic stem cells

Answer 3

1. Totipotent
2. They have the ability to differentiate into any cell type that makes up an organism, including the extra embryonic tissue like placenta

Question 4

Describe features of embryonic stem cells

Answer 4

1. Pluripotent
2. They have the ability to differentiate into any cell type that makes up an organism, except the extra embryonic tissue for the formation of a foetus

Question 5

Describe features of blood stem cells

Answer 5

1. Multipotent
2. They have the ability to differentiate into a limited and related range of cell types in an organism
3. Blood stem cells undergo differentiation to form different types of blood cells to maintain the specific tissues where they reside by replacing worn-out or damaged red blood cells and white blood cells
4. Blood stem cells differentiate to form multipotent lymphoid and myeloid stem cells that further differentiate to form specialised cell types
5. Myeloid stem cells undergo differentiation to form cells such as macrophages that are involved in the innate immunity to generate inflammatory responses
6. Lymphoid stem cells undergo differentiation to form cells such as T lymphocytes that are involved in the adaptive immunity for a cell-mediated response

Question 6

Why cells were removed from donar [organ]

Answer 6

1. Cells from donor [organ] are foreign to the recipient as composition of glycoproteins on donor cells are different. Recipient’s cytotoxic T cells may attack and destroy the donor cells
2. Hence, donor [organ] has to be removed to avoid stimulating the adaptive immune system that would lead to the rejection of the foreign transplant cells
3. This is so that the recipient does not have to rely on immunosuppressants for the rest of their life

Question 7

Ethical implications of using embryonic stem cells

Answer 7

1. Creation of embryos is too controversial as embryos are treated as a source of spare body part
2. Possible exploitation of female donors for their oocytes, especially in poorer countries or countries with fewer legal restrictions
3. Oocyte retrieval is an invasive procedure and has high risks of medical complications

Question 8

How does iPSCs overcome some of the ethical concerns

Answer 8

1. Bypasses the high risks of medical complications involved in oocyte retrieval
2. Avoids possible exploitation of female donors for their oocytes, especially in poorer countries or countries with fewer legal restrictions
3. Provides an alternative to the controversial creation of embryos for research and as a source of spare parts.