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Advanced Molecular > Mehcanobiology > Flashcards

Mehcanobiology Flashcards

1
Q

What is mechanobiology?

A

Study of how physical forces changes in cell or tissue mechanics contribute to development, physiology and disease

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2
Q

What is mechanotransuction?

A

Conversion of a physical force to a biochemical response

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3
Q

What is mechanosensing?

A

When a protein or cellular structure responds to a physical cue to initiate mechanotransduction

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4
Q

What is are the steps building up to cellular response and their components?

A
  1. Mechanosensing: Adhesion receptors, membrane proteins/signalling
  2. Signal transduction: often along cytoskeleton
  3. Signal integration at nucleus: Chromatin rearrangement, nuclear pore opening
  4. Cellular response: Cell shape, fate, motility, growth
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5
Q

What is an example of mechanotransduction?

A
  • Arteries increase with blood flow but capillaries cant cope so muscles contract to constrict the diameter again
  • Cytoskeleton cell shape changes with fluid flow because cells counteract force that fluid flow is exerting
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6
Q

Describe the components of lung on a chip

A
  • Mimic lungs on mechanical and cellular level
  • Has fluid and air flow
  • It has epithelial cells and flexible membranes with many channels
  • Artificial membrane which contains small pores and the endothelium which mimics the blood vessels
  • Vacuum on left and right side of the air/blood chamber, vacuum can be applied, stretched and released to reinact breathing
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7
Q

How is lung on a chip used to study lung inflammation?

A
  • TNF is a cytokine involved in lung inflammation
  • Once added, it can be seen that neutrophils get stuck to the endothelial layer due to the upregulation of adhesion receptors
  • They migrate towards the epithelial layer over time through pores
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8
Q

How is lung on a chip used to study lung infection?

A
  • Adding E.coli on the epithelial layer
  • Bacteria secretes factors inducing TNF
  • Leads to neutrophils being accumulated
  • Neutrophil migration through endothelial and epithelial layer and engulfs the bacteria
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9
Q

What is a neutrophil?

A

A type of white blood cell involved in the immune systems response to inflammation and infection

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10
Q

How is lung on a chip used to study mechanical stretching as a result of nanoparticles?

A
  • Gas particles applied within air channel of lungs
  • These particles initiate inflammatory response: adhesion of neutrophils, immobilisation etc.
  • Mechanical stretching mimics the breathing
  • See an increase in iCAM1 expression which is involved in facilitating the adhesion of immune cells in the inflammatory response
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11
Q

Why are organ on chip experiments good?

A
  • Can be used to reduce animal experiments as human cells can be used on the chip
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12
Q

What is the equation for stress?

A

Force/Area
(Pa)

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13
Q

What is the equation for strain?

A

Change in length/ Original length
No units

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14
Q

What is the equation for stiffness?

A

Stress/Strain
(kPa)
- Plotting stress against strain can give u info about the defined properties of a material

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15
Q

Give some examples of soft, intermediate and stiff tissues in the body

A

Soft: Brain, breast
Intermediate: Liver, Kidney, Lung
Stiff: Cartilage, bone

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16
Q

How can stiffness be measured?

A

By indentation, looking at the force applied and the depth of indentation into plastic

17
Q

How is stiffness relevant in differentiation?

A
  • Human stem cells can develop into bone, muscle and brain cells
    -Stiffness can steer differentiate
  • When generating stem cells, provides information that neurons for example need a softer surface than plastic for in vitro experiments
18
Q

How can ultrasounds be used to measure the stiffness of organs?

A
  • Looks at speed of sound and how fast its being transmitted which is proportional to stiffness
  • Non invasive
19
Q

Give examples of two diseases where there is increased stiffness in the organs

A
  • Fibrotic diseased liver
  • Chronic liver disease
20
Q

How is cancer associated with tissue stiffening ?

A
  • Lump like structures often detected by the patients
  • Tumour tissue is stiffer than surrounding healthy tissue
  • Stiffness can go up to 8kPa
  • Tumour is exerting force on to adjacent healthy tissue, modifying the healthy tissue
21
Q

Why is a tumour stiffer than a normal cell? LEARN

A
  • Cells more tightly packed
  • Tumour cells and fibroblasts (tumour-activating) are excreting much more extracellular matrix than normal *
    Cross-linking of ECM*
    Desnity of tumour cell *
22
Q

What mechanosensors detect pressure in the cell?

A
  1. Piezo channels
  2. Integrins
  3. Caveolae
23
Q

How do piezo channels work?

A
  • Ion channels which respond to stretch (mechosensitive)
  • When lateral tension to the membrane is applied (pulled on either side) pore opens leading to the influx of extracellular Ca2+ and transducing mechanical signals into electrical and chemical signals in the cell.
  • actin filaments is what pulls the membrane
  • F-actin facilitates opening of the pore
24
Q

How do integrins work?

A
  • Mechanoreceptor, transmembrane, links cells with the ECM
  • Activated through ‘inside out’ signalling, phosphorylation on the inside signals for integrins to engage with the ECM
  • F-actin connects to integrins through Talin and Vinculin
  • Vinculin binds when the actin-myosin (connected to integrins through talin) applies a force and pulls, unfolding a binding site for vinculin enhacing the F-actin connection
  • So integrins connect with intracellular matrix (F-actin) on one side and ECM on the other
25
Q

How do caveolae work?

A
  • Small invagination on the plasma membrane
  • Lateral tension applied so the caveolae flattens out
  • Caveolae links to stress fibres and actin cytoskeleton
  • This causes Cavin molecules attached on the intracellular side to detach and go on for further downstream signalling processes
26
Q

How is actin and myosin contraction regulated and why is it important?

A
  • Activation of Rho (GTPase)
  • Interacts with Rho dependent kinase
  • This phosphorylates the myosin light chain
  • Contraction occurs
  • Regulation is essential for changing cell shape, cell migration etc.
27
Q

What transcription factor is involved in epithelial to mesenchymal transition?

A
  • SNAIL
  • e.g. in the process of epithelial to mesenchymal in cancer cells, SNAIL appears
28
Q

What two enzymes when dysregulated play a role in cancer, particularly in cancer invasion?

A

LOXL2 and MMPs
- Contribute to the remodelling of the ECM, facilitating tissue remodelling which cancer cells need to invade

29
Q

What is the role of the hippo pathway?

A

Regulating:
- Cell proliferation
- Apoptosis
- Organ size

Dysregulation can be implicated in cancer

30
Q

How is the size of an organ regulated?

A
  • LATS1 (kinase) is activated by Mst1/2 (kinase)
  • YAP/TAZ is phosphorylated by LATS1/2 at ps127 (a serine amino acid)
  • 14-3-3 protein binds to YAP/TAZ meaning it cannot enter the nucleus, stays in cytosol
  • When 14-3-3 is removed, cytoplasmic retention stops and YAP/TAZ can enter the nucleus and bind to DNA as a transcriptional regulator
31
Q

What factors cause YAP to be localised in the nucleus?

A
  • Large cell area, Stiff ECM, Higher contractile forces

This leads to process such as cell proliferation, cell growth and the formation of osteoblasts

32
Q

What factors cause YAP to be localised in the cytosol?

A

Smaller cell adhesion area, soft ECM and lower contractile forces

Leads to processes such as growth arrest

Advanced Molecular (13 decks)

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