Stem Cells

Question 1

Define stem cell and its characteristics:

Answer 1

A cell capable of self renewal and differentiation into different specialised cell types

Core Characteristics:
Self-Renewal - ability to divide and produce identical stem cells over long periods.
Potency - ability to differentiate into various cell types.

Question 2

What are the different types of stem cells ?

Answer 2

Embryonic Stem Cells (ESCs): Derived from the inner cell mass of the blastocyst; pluripotent.

Adult Stem Cells (ASCs): Found in specific tissues (e.g., bone marrow, skin); multipotent or unipotent.

Induced Pluripotent Stem Cells (iPSCs): Somatic cells reprogrammed to pluripotency through genetic manipulation.

Question 3

Describe the different potencies of stem cells:

Answer 3

Totipotent: Can form all embryonic and extra-embryonic cell types (e.g., zygote, first few cell divisions).

Pluripotent: Can differentiate into all embryonic germ layers (ectoderm, mesoderm, endoderm) but not extra-embryonic tissues (e.g., ESCs, iPSCs).

Multipotent: Can differentiate into multiple, but limited, cell types within a specific lineage (e.g., hematopoietic stem cells).

Unipotent: Can produce only one cell type but retains self-renewal capacity (e.g., muscle stem cells).

Question 4

Describe feeder layer culture for pluripotent stem cells

Answer 4

Uses fibroblast feeder cells to provide nutrients and signals (e.g., LIF for mouse ESCs).
Advantages: Robust and supports long-term maintenance.
Challenges: Risk of contamination and variability.

Question 5

Describe feeder free systems to culture pluripotent stem cells

Answer 5

Cultures stem cells on defined substrates (e.g., Matrigel, laminin) with chemically defined media.
Advantages: Reduces variability; suitable for clinical applications.
Challenges: More expensive and technically demanding.

Question 6

Describe suspension culture for pluripotent stem cells

Answer 6

Cells grow as aggregates (e.g., embryoid bodies) or in bioreactors.
Advantages: Scalable for large-scale production.
Challenges: Difficult to control differentiation.

Question 7

Describe synthetic Substrates and Microfluidics for culture of pluripotent stem cells:

Answer 7

Use of engineered materials and devices to mimic the natural stem cell niche.
Advantages: Highly controlled environment; promotes reproducibility.
Challenges: Experimental and costly.

Question 8

What are the key features of pluripotent stem cells ?

Answer 8

Morphology: Compact colonies with high nuclear-to-cytoplasmic ratio.
Markers:
Transcription Factors: Oct4, Sox2, Nanog.
Surface Markers: SSEA-3/4, TRA-1-60/81.
Behavior: Ability to differentiate into derivatives of all three germ layers in vitro (e.g., embryoid body formation) and in vivo (e.g., teratoma formation).