Cell Bio - Stem Cells and Tissue Regeneration

Totipotent Cell

A cell that can become any cell in an organism

Do we know that totipotent cells exist?

No

Pluripotent Cell

A cell that can become nearly any cell in an organism

Multipotent Cell

A cell that can become any cell within a particular tissue or organ

Self-Renewal

When stem cells divide, they produce one progenitor daughter and one stem cell daughter (usually)

Two methods of self-renewal in stem cells

• Asymmetric Divisions

• Getting kicked out of the stem cell niche

Stem Cell Niche

A location that provides cues to keep stem cells from differentiating, such as secreted signal molecules

Progenitor Cells

A cell that will go on to differentiate

Potential outcomes of stem cell division

1. Two stem daughter cells

2. Two progenitor daughter cels

3. One of each

Where can stem cells be found in the intestinal epithelium?

At the base of Crypts, between the villi

Lineage Tracing

Genetically label a stem cell, then you can watch which cells are derived from it because they will also be labelled

Hematopoietic Stem Cells

Multipotent stem cells that can generate all types of blood cells

Committed Progenitors

Cells that are no longer stem cells because they cannot self-renew, and can only produce cells in their lineage

Cancer stem cells

Tumors contain their own cancer stem cells, and a single one can recreate a tumor

Why is liver tissue unique?

It can regrow without stem cells

De-differentiating

When a cell loses specialized characteristics to replace lost tissue

What species can regenerate their whole body?

Planaria

Blastema

In fish/amphibians, a clump of activated stem cells and progenitor cells that allows for limb regeneration

Quiescent Cells

Cells that have temporarily exited the cell cycle

Satellite Cells

Quiescent cells that can become activated and proliferate in response to muscle damage

What is the primary example of a pluripotent cell?

Early embryonic stem cells

Embryonic Stem Cell Properties (there are 3)

• Upregulate telomerase to maintain telomere length

• Much more euchromatin, for flexibility in gene expression

• Express ES-critical genes

ES-Critical Genes

Certain genes in Embryonic Stem Cells that are essential to maintaining pluripotency

Induced Pluripotent Stem Cells (iPS)

Non-stem cells modified to behave like pluripotent stem cells

How do we make iPS?

Certain transcription factors express genes that cause reprogramming in a small percentage of cells (we are working on yield still)

What are iPS cells most commonly produced from?

Fibroblasts

Transdifferentiation

Fibroblasts that skip the iPS cell stage and go straight to expressing genes of a certain target tissue

Where are transdifferentiated cells used?

In research, because they can retain some characteristics of fibroblasts so they aren’t yet suited for clinical medicine.

Uses of iPS or transdifferentiated cells

• Studying disease mechanisms

• Screening drugs

• (Someday) giving patients healthy cells that are genetically matched

Organoids

Pluripotent stem cells that can be induced into created 3D tissue structures resembling human tissues (like a retina)