|cell deformation, fluid flow, electrical streaming potentials (ions)
Intracellular events: nucleus distortion, mechano ion channels, integrins, mitochondria distortion, cytoskeletal reorganisation, nitric oxide, Ca2+ signalling (downstream mechanical responses), nucleotide release.
Isolated chondrocytes are put in the agarose
similar sugar composition as proteoglycans
More simple transfer function than normal cartilage simplification model system easier to see what is happening.
(too much squeezing cell ruptures)
Phenotype is retained (when the ECM is digested the cell becomes round again.
Reproducible and well established system and enable examination of the effects of the cell deformation on signalling pathways.
Max. strain of 15% (representable level)
Cell proliferation of dynamic tests do up regulate (static down), is dominated by superficial cells (higher density of cells on top).
GAG production only regulates up at 1 Hz (static down), is dominated by deep cells (higher density of GAGs). Optimisation of 15% strain always on 1 Hz (humans, horses).
So we need both the layers!
Dynamic compression inhibits the synthesis of NO (NO= bad reduction of cell proliferation and production of GAGs). Cells that produce interleukin-1β (stimulates inflammation), an inhibitor of NO reverses this effect.
Everyone should load mechanically (also old people!).
Human chondrocytes need a growth factor (TGFβ) before they will be active and so no effect in the culture media.
Lots of interplay between mechanical loading and biochemical responses, integrin blocking will result in no responses to mechanical loading.
Explants, agarose, fibrin, PEGDM, PLA/PCL
Most of the scaffold look okay, but the mechanical properties are not good (compressive stiffness modulus of cartilage 1-10MPa, agarose 100kPa).
In Vitro (in a bioreactor a controlled environment)