Lecture 16 - Stem Cells in the Lung Flashcards
From which germ layer does the lung epithelium arise?
Endoderm
From which germ layer does the innervation of the lung arise from?
Ectoderm (neural crest cells)
From which germ layer does the endothelium, haematopoietic cells and lung mesenchyme arise from?
Mesoderm
Which part of the lung arises from the endoderm?
Lung epithelium
Which part of the lung arises from the ectoderm?
Innervation
Which part of the lung arises from the mesoderm
Lung endothelium, mesenchyme and haematopoietic cells
Number of different cell types in the lung
Over 50
How is the lung epithelium formed?
A proliferation of an endodermal progenitor in the foregut endoderm.
How are the conducting and respiratory airways formed?
Branching morphogenesis
How are the lungs developed? 1) 2) 3) 4)
1) Endodermal progenitor proliferates in the foregut endoderm, forming the lung epithelium.
2) Epithelial lung bud forms surrounded by loosely-packed mesenchymal cells.
3) Branching morphogenesis forms conducting and respiratory airways
4) Alveologenesis forms alveoli
Stages of lung development 1) 2) 3) 4) 5)
1) Embryonic
2) Pseudoglandular
3) Canalicular
4) Sacular
5) Alveolar
When does surfactant start to be produced?
Sacular period (around week 25)
Where are lung epithelial stem cells located during embryonic development?
At the distal tip of the growing lung bud
How can you stain for embryonic epithelial lung stem cells?
LD2 expression.
Which type of stem cell are lung epithelial stem cells?
Multipotent
Which cell type can give rise to goblet cells and ciliated cells?
Club cells
Cell types that club cells give rise to
Goblet cells and ciliated cells
Which part of the mesoderm do mesenchymal cells arise from?
Splanchnic mesoderm
What do mesenchymal cells give rise to in the lung?
Fibroblasts and smooth muscle cells
Expression of what marks mesenchymal progenitor cells in the lung?
FGF-10 expression
What does LD2 expression mark?
Lung epithelial stem cells
What does FGF-10 expression mark?
Mesenchymal stem cells
Role of FGF-10
Epithelial progenitors grow towards FGF-10 (FGF-10 secreted by mesenchymal progenitors at the tip of the lung bud, driving formation of bud).
What does the lung vasculature develop from?
Endothelial progenitor cells of the mesoderm
Why do the heart and lungs often have comorbidities?
Because they share a stem cell line (multipotent cardiopulmonary progenitor)
How to use flow cytometry to analyse lung stem cells
1)
2)
1) Digest lungs with collagenase
2) Colony-forming assay
Rationale behind a colony-forming assay
Stem cells will be able to regenerate. More-differentiated cells won’t be able to do so.
Phenotype of lung epithelial progenitor cell
CD45 negative
CD31 negative
EpCAM positive
CD24 low
How are lung epithelial progenitor cells grown in culture?
As a co-culture with lung stromal cells
Three colony types of colony-forming assay of lung cells
1) Airway
2) Alveolar
3) Mixed
How are alveolar cells identified in a colony-forming assay?
Expression of Pro-spc (surfactant)
How are airway cells identified in a colony-forming assay?
Muc-ac expression (mucin)
What is the significance of finding alveolar, airway and mixed colonies in a colony-forming assay?
There are cells in the lungs that are committed to one lineage (alveolar or airway) and cells that are multipotent.
Airway colonies can only give rise to airway colonies.
Alveolar colonies can only give rise to alveolar colonies.
How was the lung epithelial stem cell nice found?
1)
2)
3)
1) Club cells are depleted by naphthaline.
2) Naphthaline used to deplete club cells of airways. After ~3 days club cells were regenerated.
3) Location of regeneration found using histology
What determines epithelial stem cell fate?
Microenvironment (supported by stromal cells)
Lineage specifications of mesenchymal cells
1)
2)
Three distinct types found using flow cytometry:
1) CD166+ has low proliferative capacity, becomes myofibroblasts.
2) Two CD166- types are multipotent, can become either myofibroblasts or lipofibroblasts
Factor released by mesenchymal stromal cells in the lung that allow epithelial stem cells to regenerate
FGF-10
Most important expressed molecules that allow identification of adult lung epithelial stem cells
Differential expression of EpCAM and CD24
Another name for culture-forming assay
In vitro clonogenic assay
Which rank do lung diseases have worldwide for disease prevalence and cost?
2nd
When might a stem-cell therapy for lung disease a good idea?
When the disease is chronic. If it is acute, stem-cell therapy might be too slow
Two main approaches for stem cell therapy
1) Deliver functioning stem cells to needed area
2) Deliver factors that will result in genesis of stem cells in needed area
Why aren’t embryonic stem cells appropriate for transplant?
Form teratomas
For what could stem cells be used as a gene therapy?
Cystic fibrosis
Successful tissue decellularisation transplant
Trachaea
Problem with tissue decellularisation
Organ being made must be self-renewing. Need to understand how cells communicate in tissue
Another role of mesenchymal stem cells
Intrinsically anti-inflammatory
