lecture 16: stem cell therapies for respiratory diseases Flashcards
1
Q
How does the lung develop in the embryo?
A
- formation of blastocyst → gastrulation → ectoderm, endoderm, mesoderm
- most textbooks will say that the lung is of endoderm
- true of the lung epithelium
- but lung is a very complex structure with contributions from other germ layers
- lung innervation → ectoderm
- mesoderm → lung endothelium, haematopoietic cells, lung mesenchyme
2
Q
Of how many cell types is the lung comprised?
A
- over 50 different cell types in the adult lung
- cartilage in the upper airways
- neural tissue
- epithelium itself made up of many different specialised epithelial cell types
- ciliated cells
- basal cells
- club cells
- dedicated type I and II pneumocytes in alveoli
- mesenchymal cells that are largely structural
- vascular
- endothelial
- resident haematopoietic regeneratation
- so when we talk about regeneration in the lung have to think of the stem cells that contribute to all of these different lineages
3
Q
What is patterning of the foregut endoderm?
A
- the lung epithelium is formed by proliferation of an endodermal progenitor cell in the foregut endoderm
- foregut endoderm gives rise to thyroid, liver, pancreas, intestine and lung bud
- lung bud branches out from this structure towards mesenchymal cells → interaction between the two kinds of cells
- the structure of the lung is then formed by formation of an epithelial lung bud surrounded by loosely packed mesenchymal cells
- branching morphogenesis results in the generation of the conducting and respiratory airways
- aveologenesis results in the formation of mature pulmonary gas-exchange units (alveoli)
4
Q
What are the stages of lung development?
A
- occurs over 38 weeks
- embryonic
- bronchi
- pseudoglandular
- bronchioles
- terminal bronchioles
- canallicular
- respiratory bronchioles
- saccular
- alveolar ducts
- alveolar
- alveolar sac
- continues on post birth
5
Q
What is epithelial branching morphogenesis?
A
- lung epithelial stem cells in the embryonic lung are located at the distal tip of the growing lung bud
- E11: just small bification where you just have developing out from the foregut endoderm
- very quickly go through a pattern of branching morphogenesis right to where have almost a fully developed embryonic lung at E16
6
Q
What is lineage tracing of lung embryonic stem cells?
A
- by genetically tagging lung embryonic stem cells by their expression of Id2 you can show that all lung epithelial cells are the progeny of Id2pos stem cells because the genetic marker (blue) is passed on during cell division during development
- Id2 marks lung epithelial stem cells at the tip od the budding epithelium
7
Q
What is the epithelial hierarchy in the embryonic lung?
A
- lung embryonic stem cells, derived from the foregut endoderm, are multipotent epithelial stem cells capable of giving rise to all epithelial cell types in the lung
- endoderm
- embryonic lung bud
- lung embryonic stem cell (Id2+)
- alveolar progenitor
- alveolar type 2 cell
- alveolar type 1 cell
- alveolar type 2 cell
- bronchiolar progenitor
- neuroendocrine cell
- basal cell
- club cell
- ciliated cell
- goblet cell
- club cell
- alveolar progenitor
- lung embryonic stem cell (Id2+)
- embryonic lung bud
8
Q
What is the lung mesenchyme?
A
- mesenchymal cells derived from the splanchnic mesoderm give rise to fibroblasts and smooth muscle in the developing lung
- the developing lung epithelium is surrounded by mesenchymal cells
- differentiated smooth muscle cells surround the airways in the developing lung
- mesenchymal progenitor cells at the distal tip
- FGF-10 (blue) marks mesenchymal progenitor cells
- very close relationship between the epithelial and mesenchymal progenitors during development where the mesenchymal progenitors actually instruct the epithelial pgs what to do → reciprocal feedback → mesenchymal cells move up the side and develop into smooth muscle
9
Q
What is the crosstalk with the mesenchyme?
A
- the proliferation and differentiation of lung embryonic stem cells is regulated by signals emanating from the surrounding mesenchyme
- FGF-10 produced by mesenchymal cells promote epithelial growth
- epithelial progenitors grow towards the FGF-10 → proliferate → undergo branching morphogenesis → all of the epithelial cells of the lung
- mesenchymal cells begin to differentiate and wrap around → smooth muscles → lines the airways
10
Q
What is innervation of the lungs?
A
- innervation of the developing lung is derived from neural crest progenitor cells of the ectoderm
11
Q
What is vascularisation of the lung?
A
- vascularisation of the developing lung is derived from endothelial progenitor cells of the mesoderm
- flk-1 labels endothelial cells
- very complex
- you have a lot of endothelial cells wrapped around the alveoli and stretching up the airways
- very important for gas exchange
- in terms of understanding regenerative potential of the lung we need to know a lot more about how the endothelial progenitors contribute to vascularisation
- if the process goes wrong you have
12
Q
What is co-development of the heart and lung?
A
- new evidence that lung mesenchyme and endothelium shares a common ancestor with the cardiovascular system
- multipotent cardiopulmonary progenitor
- cardiac inflow tract cardiomyocyte progenitor
- atrial/sinus venosus myocardium
- pulmonary vein myocardium
- cardiopulmonary mesenchymal progenitor
- pulmonary artery SMC
- pulmonary vein SMC
- airway SMC
- pericyte
- proximal vessel endothelium
- cardiac inflow tract cardiomyocyte progenitor
13
Q
What is the most extensively researched stem cell hierarchy?
A
- hematopoeisis: a model stem cell hierarchy
- stem cells → progenitor cells → differentiated cells
- defining feature of stem cells is the capacy to self-renew and give rise to differentiated cells
- progressively become more restricted further and further down the heirarchy
- very well mapped out
14
Q
What is the cellular architecture of the adult lung?
A
- epithelium: lines upper airways, bronchioles, alveoli
- underneath a lot of different stromal cells
- cartilage in upper airways
- haematopoietic cells → interact bahlbehoigf
15
Q
What is flow cytometry for single cell analysis?
A
- adult stem cells are characterised by the expression of multiple markers which collectively specify the stem cell state and the lack of markers that are associated with differentiated cell lineages
- i.e. stem cells are often defined as Marker-Apos Marker-Bpos Marker-Cpos
- the crucial advantage of using flow cytometry for stem cell research is the ‘single cell’ measuring principle: each and every cell is analysed as a single event → rare populations can be detected