Expression des glycosyltrasférases et synthèse des protéoglycanes : importance dans l'ingénierie du cartilage articulaire – Glycocart

Degenerative joint diseases, such as osteoarthritis, are a leading cause of disability. These pathologies are a consequence of mechanical and biological processes that lead to disruption of cartilage homeostasis. Despite, their important socio-economical impact, there are until now no efficient therapies available. Indeed, repair of cartilage defects is difficult due to the weak potency of the tissue to regenerate. The pharmacological approaches available are limited to symptomatic treatments, using analgesics and anti-inflammatory substances that did not affect the progression of the disease. In articular diseases, the loss of proteoglycan (PG) anabolism and the quantitative and qualitative modifications of their glycosaminoglycan (GAG) chains are early crucial events of cartilage damage. Indeed, PGs play key-roles in both the structural organisation of the extracellular matrix, and in regulation mechanisms, due to their potency to interact with growth factors and cytokines. The global reaction sequence responsible for the construction of GAG chains of PGs has been established. However, the regulation mechanisms of the glycosyltransferases (GTs) that catalyse the different steps of the polysaccharide synthesis remain to be elucidated. Moreover, the identity of the GTs that are responsible for the decrease in GAG synthesis in pathological conditions have to be determined. Several tissue engineering approaches, including tissue or cell therapy have been developed in order to counteract cartilage destruction, especially by targeting proinflammatory cytokines. However, these strategies did not lead to effective stimulation of the synthesis of cartilage matrix components. Our project aims at better understanding the mechanisms that are responsible for GAG anabolism decrease in degenerative joint diseases, and at identifying the GTs involved. The project involves a partnership of 3 research groups and will develop a multidisciplinary approach for the functional analysis of GTs and PGs. The coordinator will be responsible for the genomic analysis of GTs in cartilage using SuperArray DNA chips, for the cloning, heterologous expression and characterisation of target GTs. He will evaluate the contribution of these GTs in GAG biosynthesis and their potency to promote cartilage repair by gene transfer techniques. Group 2 is composed of glycochemists who will be involved in the synthesis of original glycopeptidic analogs and oligosaccharides, which are necessary to investigate the functional analysis of target GTs. The third group will develop suitable approaches to evaluate the expression of the PGs at the cell surface by genomic analysis, and quantitative and qualitative determination of GAG chain composition using chromatography or FACE (fluorophore-assisted carbohydrate electrophoresis) technologies. He will determine the impact of the perturbation of PGs expression on the metabolism of chondrocytes and their response to soluble mediators. Thus this study will lead to a better understanding of the individual importance of GT in GAG synthesis and of their regulation and should provide the basis for the design of new and efficient therapies for the treatment of joint diseases. Other pathologies that are characterised by changes in PGs biosynthesis, such as cancer, atherosclerosis or Alzheimer's disease would greatly benefit from the conclusion of this study. The multidisciplinary of the approaches used (glycogenomics, genetic and protein engineering, glycochemistry, cell and tissue therapy), the complementarity of the three partners involved in the project, which also associates competent research units in glycobiology and chemistry, as well as hospital departments (Rheumatology, Ortopaedics) are a token of a continuum between basic research of cartilage matrix and development of new approaches of tissue engineering in Human.