Use this URL to cite or link to this record in EThOS:
Title: Investigation of the effects of injury upon intracellular signalling pathways and expression of inflammatory response genes in articular cartilage
Author: Watt, Fiona Elizabeth
ISNI:       0000 0004 2679 9025
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
Availability of Full Text:
Access from EThOS:
Access from Institution:
Damage to joints predisposes to osteoarthritis. The mechanism by which injury to cartilage might lead to net matrix loss and cartilage degeneration remains unknown. Following experimental sharp injury to porcine articular cartilage (dissection from, or scoring of the articular surface), our group has previously shown rapid activation of the 3 mitogen activated protein kinase (MAPK) pathways in cartilage. Activation of ERK, and probably also p38 MAPK, is due to release of fibroblast growth factor (FGF) from the matrix after injury. However, despite a long search, the cause of JNK activation following sharp injury remains unknown. I investigated the extent and regulation of inflammatory signalling after cartilage injury and whether it was sufficient to cause expression of inflammatory response genes. In this work, I show that a number of intracellular signalling pathways including PI3 kinase and IκB kinase (IKK) (which leads to activation of NFκB) are activated by sharp injury to cartilage. The signalling following injury was sufficient to induce a wide range of inflammatory response mRNAs, including pro-inflammatory cytokines such as IL-6, COX-2 and proteinases such as MMP-1 and ADAMTS-4 in a pattern which was not entirely IL-1-like. Pharmacological inhibition experiments suggested that the production by injured cartilage of an inflammatory response gene which could be assayed at the protein level, activin A, was regulated by FGF-mediated pathways (ERK) as well as by NFκB and tyrosine kinases (src family kinases). Given these findings, the role of tyrosine kinases in the early response of cartilage to injury was explored. By phosphotyrosine immunoprecipitation and purification from injured cartilage lysates, FAK and its substrate paxillin were identified from silverstained gels by mass spectrometry. The phosphorylation of these src substrates accounted for rapidly inducible bands seen on phosphotyrosine western blotting of injured cartilage lysates. However, no evidence of a role for src kinases in the regulation of MAPK/IKK signalling upon injury was found. In contrast, blockade of another tyrosine kinase, the FGF receptor, led to partial inhibition not only of the ERK pathway following sharp injury, but also the other MAPKs and IKK. Whilst activation of the same pathways was also seen following injury to synovium, FGF receptor inhibition had no effect on this signalling. This suggested that FGF may have a pro-inflammatory action following injury in vivo which is a particular feature of cartilage.
Supervisor: Saklatvala, Jeremy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral