Stem Cells- Squier

Question 1

Definition of stem cell?

Answer 1

oCells that Persist for the Lifetime of the Organism
oContinues to Reproduce Itself
oGenerates Differentiated Progeny (Involves Transit Amplifying Cells).
oInner cell mass in blastocyst gives rise to ES cells.

Question 2

Totipotency?

Answer 2

the potential of a single cell to develop into a total organism (e.g., a fertilized egg and the four cell stage).

Question 3

Pluripotency?

Answer 3

is a cell’s capacity to give rise to all cell types in the body but not to the supporting structures, such as the placenta, amnion, and chorion, all of which are needed for the development of an organism.
AKA: embryonic stem cells.

Question 4

Unipotency?

Answer 4

is a cell’s capacity to give rise to only one cell type.

Question 5

Multipotency?

Answer 5

is a cell’s capacity to give rise to a small number of different cell types.
AKA: tissue specific stem cells.

Question 6

List the research and therapeutic applications of different types of stem cells.

Answer 6

Advantages of iPS cell lines:
•Differentiated cells will be a perfect immunological match to the donor, permitting grafting back without the use of immunosuppressive drugs.
•Permits treatment of genetic diseases or cancers (e.g., repopulation of bone marrow).
•Tumor formation represents major concern due to mechanisms of viral gene insertion (introduction of pluripotency genes). Host genes may be interrupted. In addition, silenced genes (which occur during passage) may be reactivated.

Potential therapies using pluripotent stem cells (ES or iPS)

1. Diabetes
2. Parkinson’s
3. Spinal repair

Question 7

Describe how embryonic stem (ES) cells are isolated & cultured from in vitro fertilization (IVF) blastocysts and by somatic cell nuclear transfer (SCNT).

Answer 7

IVF:
•In vitro fertilization for reproductive purposes→ eggs from donor fertilized & allowed to develop in vitro (in culture)
•Fertilized eggs implanted into mother in fertility clinics
•Extra embryos frozen →excess embryos that can be used to harvest ES cells
•Inner cell mass harvested from blastocyst (30 cells) → cultured with feeder cells
•Feeder cells provide matrix for attachment & nutrients
•Feeder cells can contaminate ES cells with viruses or other molecules (safety issues in patient transplantation)
SCNT:
•Nucleus from Somatic Cell Transferred into Enucleated Eggs.
•Early Embryo Can Be Used to Create Embryonic Stem Cells (Genetic Match to Donor).
•Offers Pathway to Therapeutic Cloning or Propagation of Livestock

Question 8

Describe how induced pluripotent stem cells (iPS) cells are generated.

Answer 8

oiPS are engineered cells derived from somatic cells that resemble embryonic stem (ES) cells.
oIntroducing foreign genes (at least 4) (transcription factors and oncogenes) into cells using vectors.

Question 9

Describe how tissue specific stem cells can be used therapeutically (especially hematopoietic stem cells for grafting into bone marrow).

Answer 9

Tissue Subtypes:

1. Post-mitotic (muscle and neuronal) are non-dividing cells (formed during embryogenesis or soon after birth) and contain few or NO stem cells. Skeletal muscle contains satellite cells critical for regeneration (not true stem cells).
2. Expanding (liver, kidney, and thyroid) undergo an expansion only during juvenile growth and possess some stem cells that can generate new cells to repopulate tissues (stem cells typically are not clearly identified).
3. Renewal (epithelial lining of intestine, stomach, epidermis of skin, testes, and hematopoietic system) undergo continual replacement (involving transit amplifying cells that cease dividing in basal layers and then progressively differentiate).

Question 10

Hematopoietic stem cell transplantation?

Answer 10

• 50,000 HSCTs carried out yearly with 10% mortality rate (includes bone marrow and stem cells from non-marrow sources (e.g., peripheral blood or umbilical cord blood).
• Radiation preferentially kills dividing cells, where hematopoietic tissue of bone is most sensitive.
• Following repopulation from donor there is immune cell reprograming and a transfer of tolerance.
• Matching of host and donor lymphocytes [requires a good human leukocyte antigen (HLA) match].
• Current practice involves incomplete destruction of host cells, and uses graft-versus-leukemia effect to destroy tumor cells.

Question 11

Understand differences between existing (proven) stem cell treatments and aspirational stem cell therapies.

Answer 11

1. Resident (Multipotent) Stem Cells Are Therapeutically Robust, and Represent Major Forms of Treatment.
2. Use of ES and iPS (Pluripotent) Stems Cells Represent Important Research Tools (Cell Culture and Genetically Modified Organisms).
3. Major Value of Human Pluripotent Stem Cells (iPS) May Be to Study Human Embryonic Development and Assess Drug Screening without Needing Embryos.