Stem Cells

What are the 3 unique features of stem cells?

1. They are undifferentiated and unspecialised

2. They can undergo extensive proliferation and are capable of self-renewal through mitosis

3. They can differentiate into various specialised cell types upon stimulation by appropirate molecular signals

Totipotent cells characteristics and examples

They can differentiate into all of the cell types that make up an organism including extra-embryonic tissue such as placenta

They can be pluripotent and multipotent

Eg. Zygotic stem cells, Cells that are produced within the first 3 mitotic divisions (8 cell stage)

Pluripotent stem cells characteristics and examples

They can differentiate into all of the cell types except extra-embryonic tissue like placenta

They can be multipotent

Eg. Embryonic stem cells derived from cells of inner cell mass of blastocyst (forms 4-5 days post fertilisation)

Multipotent stem cells characteristics and examples

Able to differentiate into several related specialised cell types but far fewer types than pluripotent

Eg. Adult stem cells like blood stem cells (RBC to transport O2, WBC to fight infections, platelets for blood clotting)

How can stem cells differentiate into specialised cells upon receiving molecular signals

Molecular signals may activate or shut down expression of specific genes that result in synthesis of tissue specific structures that enable these specialised cells to perform certain functions

What are advantages of induced pluripotent stem cells (iPSCs) ?

1. they are derived directly from adult tissues so they do not generate or destroy any human embryos

2. they can be easily obtained from any type of adult cell without risk to donor

3. they can be used to generate patient-specific cells to prevent rejection by immune system

What are functions of blood stem cells? (think to overall function of stem cells and what blood stem cells are)

Blood stem cells are multipotent stem cells so they differentiate into several related cell types, but are restricted to blood cells only.

They undergo extensive proliferation and self-renewal to ensure a constant pool of blood stem cells.

They replace blood cells lost through normal cell death.

They give rise to RBC, WBC

What are the functions of stem cells?

• Extensive proliferation and self-renewal to ensure a constant pool of blood stem cells

• Growth and development

• Differentitate into specialised cells to regenerate or replace cells that are lost to cell death or injury

What principals to consider of bioethics?

1. Respect for persons

   • able to make their own choices w informed consent

2. Maximise benefits

   • always act for benefit of others

3. Minimise harms

   • do not harm

4. Justice

   • providing equally to all (sharing of risks, costs, benefits)

Name a genetic disease which has been treated with stem cell transplantation

Leukaemia or Parkinson’s disease