Chapter 4 Answers to Select Review Questions

1.  List and describe the two basic properties of adult stem cells.

Self-renewal - indefinite or near-indefinite replicative capacity
Multipotency - the ability to generate multiple progeny of unique identities

3.  What is a "stem cell niche" and why is it important for regulating stem cell behavior?

It is the microenvironment wherein a stem cell resides. This niche provides the necessary growth and differentiation signaling events which are conducive to both cellular division and differentiation.

8.  What seminal discovery was made in 1961 regarding muscle development and who made it?

Myosatellite cells were discovered by Andrew Mauro.  These are progenitor cells present in muscle capable of terminal differentiation and fusion to enhance or augment existing muscle fibers and to form new fibers

10.  What homeodomain-containing transcription factors are crucial for myosatellite cell differentiation?

Pax3 and Pax7

14.  What key transcription factor and signaling protein drives MSC osteogenic versus adipogenic differentiation?

The signaling molecule Wnt10b and the runt-related transcription factor Runx2 have been identified as key regulators of the decision of MSCs to commit to osteogenic lineages. 

18.  Where does neurogenesis occur in the developing mammalian embryo and in the adult?

Neurogenesis during embryonic development occurs, for the most part, in the germinal ventricular zone, with progenitor populations rapidly expanding in concert with neural tube thickening.  In the adult brain neurogenesis occurs primarily in the subventricular zone (SVZ) of the lateral ventricles.

21.  What is the primary function of endothelial stem cells?

Endothelial stem cells have the primary purpose of creating a thin endothelium lining the walls of the vasculature.

23.  What are three sources of endothelial stem cells?

Endothelial stem cells can be isolated from the bone marrow, peripheral blood (isolated from peripheral blood mononuclear cells) or umbilical cord blood.

25.  How do tumors affect endothelial progenitor cell behavior?

Tumors recruit EPC to enter the circulatory system through the secretion of various factors such as FGF, osteopontin, CCL2 and CCL5.  Circulating EPCs are known to play a role in the maintenance of vascular integrity at tumorigenic sites, thus ensuring a supply of nutrients to growing tumors.