W/S 5 - Liver toxicology models Flashcards
elements of organ-on chip
Microfluidic channels - nutrient, oxygen and waste exchange (made with PDMS = flexible)
Cells of target organ
Extracellular matrix - scaffold for cell attachment
Stimulate physical forces experienced by tissue
[Ewart et al, 2022] experiment
tested 27 drugs on 780 liver chips
80% sensitivity
100% specificity
[Ewart et al, 2022] how they measured liver toxicology
reduced albumin and ALT production via qRT-PCR
increase in cytokine and immune cell activation
+ immunofluorescence images of cell imaging
[Ewart et al, 2022] what cells did they use?
liver sinusoidal endothelial cells
kupffer cells
stellate cells
immune cells and liver function
kupffer cells (= macrophages in liver), natural killer cells, dendritic cells, T cells
become activated when liver encounters toxic substance
release pro-inflammatory cytokines (e.g. TNF, IL-6)
advantages of organ-on chips
Save money as better at predicting if drug will fail
- Divert more resources into drugs which are more likely to be successful
Use of human tissue - more translatable
High throughput capability
Ethical - no animals used
Accounts for donor variability (multiple donors used) - e.g. people’s diets, race/ethnicity
Customizable in what cell types you see in models
disadvantages of organ-on chips
If donor has polymorphism that drug will respond to in different way
- Donor genetics may not be relevant to wider population and polymorphisms could contribute to different drug responses
Only been shown for small molecules
Not 100% accurate
Doesn’t fully represent organ complexity - example - Pemoline couldn’t be tested because toxicity is due to immune cells, which were not included
Requires high level of expertise, not yet taken up by big drug companies as it takes lots of time to optimize
selectivity
ability to distinguish between hepatoxic and non-toxic drugs
specificity
ability to avoid false-positive predictions
[Yang et al, 2023] - why they decided to develop organ-on chips
1/3 of drugs removed from market due to liver damage
1/2 drug candidates induce hepatotoxicity in humans but not animals
[Yang et al, 2023] - fialuridine
potential hepatitis B therapy
induced severe toxic reaction and hepatic failure in humans (animal model data didn’t indicate this)
advantages of monolayer culture
low cost
easy to obtain
simple to culture
fast prep
disadvantages of monolayer culture
single cell type
no cell-cell or cell-ECM interaction
limited culture time
incomplete metabolic function
what are spheroids?
collection of cells that form spheroid shape
can be made from multiple cell types
[Yang et al, 2023] - flucloxacillin
converted to 5-hydroxymethyl metabolites by CYP3A4
= toxic to biliary epithelial cells but not hepatocytes