Catabolism of aggrecan, decorin and biglycan in tendon

Abstract

We have examined the catabolism of the proteoglycans aggrecan, decorin and biglycan in fresh tendon samples and in explant cultures of tissue from the tensional and compressed regions of young and mature bovine tendons. A panel of well-characterized antibodies that recognize glycosaminoglycan or protein (linear or neoepitope) sequences was used to detect proteoglycans and proteoglycan degradation products that were both retained within the tissue and released into the culture medium. In addition, a reverse-transcriptase-mediated PCR analysis was used to examine the mRNA expression patterns of tendon proteoglycans and aggrecanases. The results of this study indicate a major role for aggrecanase(s) in the catabolism of aggrecan in bovine tendon. The study also provides a characterization of glycosaminoglycan epitopes associated with the proteoglycans of tendon, illustrating age-related changes in the isomers of chondroitin sulphate disaccharides that remain attached to the core protein glycosaminoglycan linkage region after digestion with chondroitinase ABC. Evidence for a rapid turnover of the small proteoglycans decorin and biglycan was also observed, indicating additional molecular pathways that might compromise the integrity of the collagen matrix and potentially contribute to tendon dysfunction after injury and during disease.

Inhibition of aggrecan turnover in short-term explant cultures of bovine tendon

“…Several members of this family have been demonstrated to have aggrecanase activity, including ADAMTS-1, ADAMTS-4, ADAMTS-5, ADAMTS-8, ADAMTS-9 and ADAMTS-15 (Porter et al, 2005). Within tendon, mRNA expression for both ADAMTS-4 and ADAMTS-5 has been detected (Rees et al, 2000;Tsuzaki et al, 2003), however it remains to be established as to whether other aggrecanases are also present in the tissue. Significantly, within explant cultures of tendon, considerable degradation of aggrecan occurs, and aggrecanase activity is present in the absence of catabolic stimulation, suggesting that the aggrecanases have a prominent role in constitutive catabolism of tendon aggrecan (Rees et al, 2005(Rees et al, , 2000.…”

“…In this regard, it has been proposed that the increased aggrecan mRNA expression and glycosaminoglycan levels that occur in painful tendinopathy may reflect an altered mechanical environment at the site of the lesion, resulting in a fibrocartilaginous expression pattern (Corps et al, 2006). We and others have demonstrated that aggrecan degradation in tendon is mediated principally via proteolysis of specific Glu-Xaa bonds, by 'aggrecanases' which are members of the ADAMTS (A Disintegrin And Metalloproteinase with Thrombospondin motifs) family of proteinases (Rees et al, 2000;Samiric et al, 2004b). Several members of this family have been demonstrated to have aggrecanase activity, including ADAMTS-1, ADAMTS-4, ADAMTS-5, ADAMTS-8, ADAMTS-9 and ADAMTS-15 (Porter et al, 2005).…”

“…Although collagen is the major component of the tendon ECM, proteoglycans are also present and it is the small leucine-rich proteoglycan, decorin, that predominates within proximal/tensional regions (Vogel and Heinegard, 1985) and is involved in the regulation of collagen fibrillogenesis (Vogel et al, 1984). The large aggregating proteoglycan, aggrecan (better known for its physiological role in articular cartilage where it serves to facilitate resistance of compressive forces during joint articulation), is also present within tensional tendon (Rees et al, 2005(Rees et al, , 2000Vogel et al, 1994), however its function within this region is unclear. Aggrecan, at a significantly higher concentration (and other matrix molecules common to the articular cartilage phenotype) is also present within fibrocartilaginous regions of tendon (Benjamin and Ralphs, 1995;Waggett et al, 1998).…”

Cultivation of human tenocytes in high-density culture

“…Tenocytes are embedded in an extensive three-dimensional network of extracellular matrix components consisting predominantly of collagen type I fibrils (>95% of tendon collagen), other types of collagen (type III and type V), proteoglycans, elastin and fibronectin (Bernard-Beaubois et al 1997;Kannus 2000;Rees et al 2000). These tendon-specific matrix components give tendon its resilience and biomechanical stability.…”

Contrasting Effects of n‐3 and n‐6 Fatty Acids on Cyclooxygenase‐2 in Model Systems for Arthritis

“…Reverse transcription-polymerase chain reactions (RT-PCR) were performed using an RNA PCR kit (PerkinElmer) as described previously [37] using oligonucleotide primers specific to cyclooxygenase cDNA sequences (see Table 1). Following an initial denaturation step of 1 min at 95°C, amplification consisted of 30-45 cycles of 1 min at 95°C, 45 s at the individual annealing temperature of the primers (Table 1), 30 s at 72°C, followed by a final extension step of 5 min at 72°C.…”