BIOL4415 - Adult Stem Cell Niche

What things comprise a stem cell niche microenvironment?

1. Stem cells

2. Support cells

3. Soluble factors

4. ECM

5. Progenitor cells

Where do stem cells reside in hair follicles?

In the hair bulge

Where do stem cells reside in cornea?

Limbus, they are called Limbal stem cells?

Where do liver stem cells reside? What can they differentiate into?

1. Canal of Hering

2. They can differentiate into hepatocytes or cholangiocytes

How does population asymmetry work

1. Stem cell divides into multiple transient cells

2. Some revert back to stem cells, other differentiate

Factors responsible for maintain HSCs in their niche during asymmetric division

1. Wnt

2. FGF

3. BMP

4. SCG - c kit interactions

5. VCAM - Integrin

6. N-Cadherins

7. Jagged - Notch

What cells to stromal cells differentiate into?

Osteoblasts, which then become osteocytes

List 2/3 signaling molecules in HSC microenvironment

1. Erythropoietin (EPO)

2. G-CSF

3. M-CSF

3 Molecules involved in cell-cell contact in HSC microenvironment

1. Desmosome

2. Adherens Junctions

3. Gap junctions

3 Molecules involved found in ECM in HSC microenvironment

1. Fibronectin

2. Collagen

3. Laminin

3 forces involved HSC differentiation in HSC microenvironment

1. Compression

2. Stiffness

3. Elasticity

4 major factors determining HSC differentiation in their microenvironment

1. Cell-cell signaling

2. Soluble factors

3. ECM interactions

4. Forces

What cells are found in the HSC niche

1. Adipocytes

2. Stromal cells

3. Osteoblasts

4. Progenitors

What cytokines do perivascular stromal cells release

1. CXCL12

2. SCF

During what time of the day to HSCs differentiate and proliferate? What causes it?

1. At night they divide

2. During the day they migrate into the vascular niche

3. Caused by release of noradrenaline during the day, which decreases CXCL12 expression in CAR and stromal cells, freeing up cells to go into the blood

Where do long-term quiescent HSCs reside

Attached to osteoblasts

Where do short-term active HSCs reside

In the perivascular niche attached to endothelial, stromal cells or CAR cells

What cells are found in intestinal stem cell niche

1. Intestinal stem cells

2. Paneth cells

Where does cell removal take place in small intestines

Anoikis, via apoptosis

How long is turnover in stem small intestines

2-3 days

Role of Paneth cells

Secrete Wnt and Delta to activate Notch signaling, which stimulates proliferation of ISCs, and is antagonistic to BMP signaling from upper cells

What happens after CBCC divison?

One cell stays next to P-cell and remains stem cells, other goes on to differentiate

Wnt vs BMP signaling

Wnt promotes stemness, BMP promtoes differentiation

Transit Amplifying cell

Differentiated cell which migrates upwards

How to visualize ISCs from the crypt?

1. Use Cre-Lox system

2. Put Cre in front of stem-cell specific promoter

3. Put stop codon flanked by Lox sites in front of a ubiquitous promoter, followed by a color which can be detected

Where are epidermal stem cells found?

Attached to basal lamina?

How do epidermal stem cells mature?

Notch signaling from mature keratinocytes induces asymmetric division

Cell signaling involved in follicle stem cell differentiation (image)

What stops bulge cells from migrating to dermal papilla

BMP4, from dermal fibroblasts and FGF16 and BMP6 from the inner bulge

What induced telogen to anagen transition

Underlying dermis and adipocytes release FGF6, FGF10, BMP inhibitions, and TGF-beta2 and Wnts

What maintains stemness of HFSCs

Shh signaling

How does Anagen end

HFSCs closer to the dermal papilla divide faster, pushing it away, thus decreasing the strength of it’s signaling and ending the anagen phase

Cord Blood vs Bone marrow when it comes to bone marrow transplant

1. Cord Blood is less mature, so lymphocytes will not be able to cause GVHD as often as mature lymphocytes from bone marrow

2. Cord Blood does not need an invasive surgery

3. Bone marrow need’s willing participants and may be in limited supply

4. Cord blood is cheaper

Describe the stem cell niche

1. Osteoblasts on the sidelines with HSCs

   1. Osteoblasts ensure these HSCs remain quiescent

   2. Release thrombopoietin which prevents blood vessel formation, decreasing oxygen supply, ensuring HSCs quiescence

   3. HSCs divide slowly

2. Perivascular niche with HSCs associated with CAR and mesenchyme cells

   1. CAR and mesenchymal cells release CXCL12, keeping the HSCs in the niche

   2. Noradrenaline from neurons blocks CXCL12 transcription

   3. At night, with less noradrenaline, more CXCL12 is produced, keeping the cells in the niche

   4. During the day, with more noradrenaline, less CXCL12 is produced, allowing HSCs to escape into blood vessels

what is anoikis

Cell death due to loss of attachment or shedding

Name of the crypt base stem sells

Columnar cells

Describe intestinal stem cell niche

1. Wnt gradient from bottom up, BMP from top down

2. Crypt has

   1. Paneth and Paneth progenitor cells

   2. Crypt base columnar cells (Intestinal stem cells)

3. Signaling from Paneth cells causes asymmetric division

   1. CBCC next to Paneth cells stays in the niche, other one becomes part of transit amplifying cells (TAC) which migrate upwards along the BMP gradient

4. At the top, the cells die via anoikis

Intestinal crypt cell cell-marker

Lgr5

Describe the skin stem cell niche

1. Basal layer is formed by epidermal stem cells

   1. Attach to basal lamina via laminin-integrin interactions

2. Notch signaling causes differentiation into keratinocytes

3. Dead keratinocytes form stratum corneum

Primary regulator of hair follicle stem cell proliferation. Show the regulatory map

c-Myc and Shh

What stem cells does umbilical tissue have

Stem cells needed for 1. cartilage

1. Cartilage

2. Blood vessel tissue

3. Skin

4. Neurons

5. Sensory organs

Three important qualities of umbilical cord cells

1. Engraftment - they can unite with other tissues

2. Homing - they can travel to the site they are needed at

3. Plasticity

What diseases can be trated using umbilical cord stem cells

1. Fanconi’s anemia

2. Leukemia

3. Metabolic disorders

What can treat Huntington’s or Parkinson’s disease

Umbilical Cord matrix stem cells (UCMS cells), such as the neuronal progenitors

Limitations of cord blood stem cells

1. Limited amount can be extracted from umbilical cord, and the donor can only donate it once

2. Delayed platelet and neutrophil engraftments, due to low numbers of these cells in the cord

How to use umbilical cord stem cells for gene therapy

1. Transduce them with retroviruses

2. Transplant them