Hughes, Clare, Dr

Dr Clare Hughes - PhD

Overview
Publications
Research

Cartilage Proteoglycan Metabolism in Osteoarthritis

Articular cartilage chondrocytes are responsible for the synthesis, organization and maintenance of a specialized extracellular matrix composed predominantly of type II collagen fibrils enmeshing large, multimolecular aggregates of cartilage proteoglycan (aggrecan) bound to hyaluronan (HA) and stabilized by cartilage link protein. The entrapment of the large, highly hydrated proteoglycan aggregates within the collagen fibril meshwork provides articular cartilage with its ability to resist compressive loads applied to the joint during articulation. Maintenance of the components of cartilage extracellular matrix is controlled by the resident chondrocytes that must balance synthetic and degradative processes in order to maintain the integrity of this specialized tissue.

Organisation of Human Aggrecan.

During degenerative joint disease (arthritis), chondrocytes elicit a catabolic response, which exceeds anabolism of new matrix molecules. Thus, there is an increase in the expression and activity of proteolytic enzymes. A major role is indicated for metalloproteinases, which are able to degrade collagen and proteoglycan (aggrecan). Historically, several of the matrix metalloproteinases were thought to be the key players in the catabolism of aggrecan. However, recently metalloproteinases belonging to the newly discovered ADAMTS (a disintegrin and metallo with thrombospondin) family (namely ADAMTS4 and ADAMTS5) have been found to be responsible for the cleavage of aggrecan at specific peptide bonds distinct from matrix metalloproteinases. It is cleavage at these latter peptide bonds by ADAMTS proteinases that now appear to be responsible for the loss of aggrecan from within the cartilage extracellular matrix during disease.

The research approaches in our laboratories have:

Focused towards bettering our understanding of the role and mechanisms by which the ADAMTS proteinases play in the destruction of aggrecan in cartilage.
Investigating the potential of biomarkers that can be used for diagnosis, distinguishing disease progression and monitoring the efficacy of surgical and therapeutic interventions.
Investigated the use of Nanotechnology for drug delivery in arthritis.

We use a multi disciplinary approach in our work that encompasses the use of monoclonal antibody technologies, protein isolation, purification and characterisation and molecular biology techniques. We are using an established panel of neoepitope antibodies to study the catabolic products generated by ADAMTS proteinases in articular cartilage in both in vitro culture systems (which mimic degradative processess during disease) as well as synovial fluids from patients diagnosed with different joint pathologies. This work will ultimately lead to the discovery of specific markers for joint diseases and therefore aid in the development of pharmaceutical inhibitors of key enzymes such as aggrecanase(s) which will then be developed for use in humans, thereby preventing or limiting the progression of cartilage erosion in osteoarthritis.

In addition, we are using monoclonal antibodies recognising the aggrecanases to elucidate the mechanism by which these enzymes are produced and processed during normal tissue homeostasis and in disease. Molecular Biology approaches have led to the discovery of an alternative-splice variant of ADAMTS-4. Furthermore, the large panel of monoclonal antibodies we have produced are now being used to develop ELISA-based assay kits for identification of biomarkers expressed in the pathogenesis of musculoskeletal diseases.