Stem Cells Flashcards
Define stem cell, self renewal, potency, embryonic stem cell
Define “potency” in regard to stem cells
Potency is the range of commitment options available to the cell.
Name and explain the different classes of potency
Totipotent - Produces a fully functioning organism. Only displayed in zygotes and early blastocysts and doesn’t occur in vertebrates.
Pluripotent - Produces cells which belong to any 3 of the germ layers (ectoderm, mesoderm, endoderm), including germ cells and may produce some/all extraembryonic cell types (placenta, yolk sac)
Multipotent - Progenitor cells are multipotent, they differentiate into discrete cell types. They form multiple lineages that constitute an entire tissue/tissues. eg. HSC
Unipotent - Produces cells of only one cell type.
Define and explain the term “self-renewal” in regards to stem cells
Self-renewal is the ability of the stem cell to create a perfect copy of itself that retains the ability to differentiate - the defining factor of stem cells.
Are all cells that can differentiate stem cells? ie. Transit Amplifying cells
No, cells can be pluripotent but not be stem cells. They NEED to be able to self renew. Transit amplifying cells are highly proliferative and differentiate into cell types but they cannot self renew.
Describe an Embryonic Stem Cells (ES Cells)
They are derived from the EPI cells of the pre-implantation embryo. When EPI cells are cultured they self-renew and form embryonic stem cells. In vivo, ES cells are transient. EPI and ES cells are both pluripotent, but unlike EPI, ES cells self-renew, making them stem cells. Pluripotent stem cells are not found at any developmental stage.
Describe a progenitor cell
They can differentiate to form different cell types but lack the self-renewal properties of stem cells. This is because when they divide, they change, letting them become terminally differentiated cells.
How would you determine if an embryonic stem cell was pluripotent?
Inject it into a mouse blastocyst, wait until the mouse is born. The chimera should have contribution (GFP detected) in tissues from each of the germ layers (gut, brain, muscle etc.). Then, cross this mouse with a non labelled mouse and see if the offspring are chimeras. This tests if a germline contribution is made and if the cells are functional.
How would you prove that a HSC is a multipotent stem cell?
Lethally irradiate a mouse (to wipe out bone marrow cells) and inject with a labelled HSC. Mouse will survive, showing that the cell has repopulated the whole blood system. However, to prove that it is a stem cell, it must undergo consecutive transplantations to prove self-renewal (Strongly suggest - cant do forever).
Describe a tissue/adult stem cell
They’re found in the organism, coming from fetal or adult tissue. They are multipotent. Some can be cultured and others can’t. Properties can change in vitro. HSCs, spermatogonial, epidermal. Cells isolated from different stages may have different roles.
