CSB329H1 Lecture 6: Lecture 6 Part 2
9 May 2018
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Lecture 6(b): Stem Cells & ECM
Intestinal Epithelium:
ð Crypts:
o Multipotent intestinal stem cells (ISCs) [red]
o Paneth cells (support cells) [purple]
• Stem cells will undergo proliferation and give rise to transit
amplifying cells (TAPs) [blue]
o TAPs will then give rise to differentiated cells:
§ Goblet cells, Enteroendocrine cells, Enterocyte
ð Involutions of the intestine (crypts & villus) are surrounded by the basal lamina; epithelial cells
o Stroma layer will also be surrounding it allowing the contraction of the intestine
Anoikis & Apoptosis:
• Anoikis – Cells that usually are in contact with ECM; if contact is lost, they commit suicide
• Apoptosis – Cells undergo programmed cell death (Anoikis is a form of apoptosis)
ISCs and Wnt Signaling:
ð Wnt signaling is essential for ISC self-renewal and maintenance
• Mesenchymal cells surrounding the crypt will secrete Wnt molecules
that affects ISCs
o ISCs are LRF5/6 positive and respond to the paracrine Wnt
signaling
ð To follow ISCs before they become TAP we can mark them with:
o LRP5/6 – Wnt Signaling
o YAP – Hippo Pathway
Renewing Intestinal Lining:
• Paneth Cells (Support Cells):
o Secrete factors that sustain and modulate the epithelial stem cells
§ Essential for long term maintenance of the intestinal epithelium
Synthetic Matrix Analogs:
• ECM is composed of polymers and the use of detergents to isolate it leads to the loss of
several factors and will only be able to replenish polymerized collagen and fibronectin
o Not representative of native ECM; missing a lot of factors
Making our ‘Own’ ECM:
• Polyethylene glycol (PEG) is used as a scaffold and will generate a 3D PEG-matrix hydrogel
o Matrix stiffness and composition can be precisely controlled, and can also decorate
PEG with a variety of molecules = mimic different ECM (tensile strength & stiffness)
Document Summary
Crypts: multipotent intestinal stem cells (iscs) [red, paneth cells (support cells) [purple, stem cells will undergo proliferation and give rise to transit amplifying cells (taps) [blue, taps will then give rise to differentiated cells: Wnt signaling is essential for isc self-renewal and maintenance: mesenchymal cells surrounding the crypt will secrete wnt molecules, iscs are lrf5/6 positive and respond to the paracrine wnt that affects iscs signaling. To follow iscs before they become tap we can mark them with: lrp5/6 wnt signaling, yap hippo pathway. Renewing intestinal lining: paneth cells (support cells): Making our own" ecm: secrete factors that sustain and modulate the epithelial stem cells. Peg with a variety of molecules = mimic different ecm (tensile strength & stiffness) Mouse intestinal organoid formation: rgd covalently linked to hydrogel, single lgr5 was introduced into the hydrogel expressing isc (yap-dependent mechanism, capable of forming circular colonies of epithelial-like cells. Non-degradable stiff matrix => gave rise to a polarized matrix.
