title: Chondroadherin fragmentation mediated by the protease HTRA1 distinguishes human intervertebral disc degeneration from normal aging.
abstract: Chondroadherin, a member of the leucine-rich repeat family, has previously been demonstrated to be fragmented in some juveniles with idiopathic scoliosis. This observation led us to investigate adults with disc degeneration. Immunoblotting analysis demonstrated that non-degenerate discs from three different age groups show no chondroadherin fragmentation. Furthermore, the chondroadherin fragments in adult degenerate disc and the juvenile scoliotic disc were compared via immunoblot analysis and appeared to have a similar size. We then investigated whether or not chondroadherin fragmentation increases with the severity of disc degeneration. Three different samples with different severities were chosen from the same disc, and chondroadherin fragmentation was found to be more abundant with increasing severity of degeneration. This observation led us to the creation of a neoepitope antibody to the cleavage site observed. We then observed that the cleavage site in adult degenerate discs and juvenile scoliotic discs was identical as confirmed by the neoepitope antibody. Consequently, investigation of the protease capable of cleaving chondroadherin at this site was necessary. In vitro digests of disc tissue demonstrated that ADAMTS-4 and -5; cathepsins K, B, and L; and MMP-3, -7, -12, and -13 were incapable of cleavage of chondroadherin at this site and that HTRA1 was indeed the only protease capable. Furthermore, increased protein levels of the processed form of HTRA1 were demonstrated in degenerate disc tissues via immunoblotting. The results suggest that chondroadherin fragmentation can be used as a biomarker to distinguish the processes of disc degeneration from normal aging.
authors.affiliation: Orthopaedic Research Laboratory, McGill University, Montreal, Quebec H3G 1A4, Canada.
authors.forename: Bashar
authors.initials: B
authors.lastname: Akhatib
authors.forename: Patrik
authors.initials: P
authors.lastname: Onnerfjord
authors.forename: Rahul
authors.initials: R
authors.lastname: Gawri
authors.forename: Jean
authors.initials: J
authors.lastname: Ouellet
authors.forename: Peter
authors.initials: P
authors.lastname: Jarzem
authors.forename: Dick
authors.initials: D
authors.lastname: Heinegård
authors.forename: John
authors.initials: J
authors.lastname: Mort
authors.forename: Peter
authors.initials: P
authors.lastname: Roughley
authors.forename: Lisbet
authors.initials: L
authors.lastname: Haglund
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000375:Aging; D001665:Binding Sites; D003937:Diagnosis, Differential; D005109:Extracellular Matrix / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D000074289:High-Temperature Requirement A Serine Peptidase 1; D006801:Humans; D007249:Inflammation; D007403:Intervertebral Disc / Q000378:metabolism / Q000473:pathology; D055959:Intervertebral Disc Degeneration / Q000201:enzymology*; D008875:Middle Aged; D010447:Peptide Hydrolases / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*
chemical_list: D016326:Extracellular Matrix Proteins; C088980:chondroadherin; D010447:Peptide Hydrolases; D000074289:High-Temperature Requirement A Serine Peptidase 1; C474012:HTRA1 protein, human; D012697:Serine Endopeptidases
keywords: Chondroadherin; Extracellular Matrix; HTRA1; IVD; Intervertebral Disc Degeneration; Protease; Protein Degradation; Protein Turnover; Proteolytic Enzymes