lec 16 Flashcards
What is Barth Syndrome and how does it come about?
A rare x-linked genetic disorder.
Results in aberrant lipid metabolism in mitochondria. Therefore patients develop cardiomyopathies as they get older.
It is characterised by a lack of mature cardiolipin in the membrane of mitochondria.
Mutation in TAFAZZIN gene - c517delG
Barth syndrome is seen in all muscles. Muscle weakness and exertional fatigue is characteristic of BTH.
How do we diagnose Barth Syndrome?
When diagnosing BTH we look at the ratio between cardiolipin and monolysocaridiolipin. If the MLCL:CL ratio is large it is defined as BTH. This can be measured via mass spec.
BTH - CM and WT-CM were cultured in galactose before measurement of ATP content. BTH -CMs saw a much lower ATP content indicating mitochondria are not as efficient at producing energy.
What are the 3 substances that we test for BTH treatment?
LA (Linoleic acid( - decreases MLCL:CL ratio and increases ATP
LA was also shown to reduce O2 consumption in BTH and increase resp reserve in BTH.
BEL (Bromoenol lactone) - decreases ratio, no effect on ATP
A/C (arginine and cysteine) - no effect on ratio but increases ATP
What is the significance of chips for BTH testing?
So when we model BTH-CM on a muscular thin film, we can see the contractility is poor but with the addition of LA the function of the BTH-CM is restored to the level of WT CMs.
What is Asthma?
Asthma arises from an inflamed airway that narrows the airways. There is no one cause of asthma like in congenital diseases.
How does Asthma give rise to symptoms and what are the current tx?
In allergic asthma the clinical symptoms of coughing wheezing and breathlessness result from an exaggerated increase in smooth muscle tone in response to allergen provocation.
Current therapies include:
Glucocorticoids
Beta agonists
What is important when modelling asthma on a chip?
In order to model Asthma on a chip we must model bronchi narrowing on a chip.
So how do we model asthma on a chip?
The process of seeding lung smooth muscle cells on a chip is the same as the cardiac chip
We can stimulate the contraction via bronchoconstrictors such as Ach. It is a native molecule in the bronchi, via autonomic innervation. So the films on the chip will curl up.
What is the role of IL-13 in asthma and the chip?
Asthma is characterised by IL-13, as IL-13 causes inflammation and increases the thickness of the airways by hypertrophying the cells.
We can recreate the asthmatic phenotype by adding IL-13 to the film for 10-14 hours.
If IL-13 and Ach are added the contraction is over exaggerated similarly to asthma.
How are atropine and Ach used in the asthmatic chip?
Atropine and Ach can be used to contract and then release the smooth muscle from its contractile state. In asthmatic chip the baseline contraction is seen to be significantly more than a normal chip.
Addition of B-agonist isoproterenol further relaxes the SM.
beta-agonists in asthma?
Beta agonists:
Isoproterenol - activates cAMP which activates Calcium channels to reduce intracellular Ca.
This reduces contractility.
Rho-A inhibitors in asthma?
Rho-A inhibitors:
Expression of Rho-A sensitizes the cells to calcium by inhibiting dephosphorylation of myosin. Rho-A inhibitors reduce sensitivity.
What are the current problems we face with chips?
- Not plug and play, not collaborative
- Really small (10p size) what doses do we give? Scaling issues.
- Analysis and result output is hard as it is tiny
- Disease models that are accurate and cell sources
- The cell culture medium that represents blood is not standardised.
