Introduction to stem cells and tissue regeneration

Question 1

What defines a stem cell?

Answer 1

Self-renewal – Can divide and generate identical copies over long periods.
Unspecialized – Not committed to a specific function.
Differentiation – Can give rise to specialized cells.

Question 2

What are the four main stem cell potency types?

Answer 2

Totipotent – Can form all embryonic and extraembryonic tissues (zygote cells).
Pluripotent – Can form all cell types in the embryo (e.g., ESCs, iPSCs).
Multipotent – Can form more than one cell type, but not all (e.g., HSCs).
Unipotent – Can form only one type of specialized cell (e.g., muscle stem cells).

Question 3

What is a progenitor cell?

Answer 3

A transitional cell between stem cells and fully differentiated cells, with limited self-renewal capacity

Question 4

How do stem cells divide?

Answer 4

Symmetric division → Produces two identical stem cells OR two differentiated cells.
Asymmetric division → Produces one stem cell + one differentiated cell.

Question 5

What influences stem cell fate?

Answer 5

The stem cell niche (local environment), which provides external signals

Question 6

Where are adult stem cells found in the human body?

Answer 6

Intestinal crypts → Maintain gut lining.
Muscle tissue → Repair damaged muscle fibres.
Bone marrow → Generate blood cells via haematopoiesis.

Question 7

What cell types arise from hematopoietic stem cells (HSCs)?

Answer 7

Red blood cells – Oxygen transport.
White blood cells – Immune defence.
Platelets – Blood clotting.

Question 8

What regulates blood cell formation?

Answer 8

Stromal cells (niche interactions).
Signalling molecules (e.g., erythropoietin for red blood cells, CSFs for immune cells).
Random chance – Some fate decisions occur unpredictably.

Question 9

How are embryonic stem cells (ESCs) derived experimentally?

Answer 9

Mouse ESCs (Martin, 1981; Evans & Kaufman, 1981).
Human ESCs (Thomson et al., 1998).

Question 10

What experimental assays confirm pluripotency?

Answer 10

Embryoid body formation – Assesses spontaneous differentiation potential.
Teratoma formation – Tumour assay testing differentiation in vivo.
Marker analysis – Detection of pluripotency genes & proteins (e.g., Oct4, Sox2).
Chimeric animal generation – Incorporation into developing embryos.

Question 11

How can fibroblasts be reprogrammed into iPSCs?

Answer 11

Takahashi & Yamanaka (2006) discovered four key transcription factors:
Oct4
Sox2
Klf4
c-Myc
Reprogramming induces massive gene expression changes, but only some cells successfully convert to iPSCs.

Question 12

How are ESCs/iPSCs useful?

Answer 12

Drug discovery – Testing new therapeutics.
Disease modelilng – Studying genetic disorders.
Cell therapy development – Generating replacement cells for regenerative medicine.