Characterisation of proteoglycans and their catabolic products in tendon and explant cultures of tendon

Sakurai

et al. 2008

Arthritis & Rheumatism

Objective. To evaluate histologic, immunohistochemical, and molecular changes in tendon induced by altered strain in a large-animal model.Methods. A full-thickness partial-width laceration of the infraspinatus tendon was created in 5 sheep, while 5 sham-operated sheep were used as controls. Sheep were killed after 4 weeks, and 4 differentially stressed tendon regions (tensile or near bone attachment from overstressed or stress-deprived halves) were evaluated for histopathology, proteoglycan (PG) accumulation, and characterization of glycosaminoglycans and aggrecan catabolites. Gene expression of matrix components, enzymes, and inhibitors was analyzed by reverse transcriptase-polymerase chain reaction.Results. Histopathologic changes were detected in both overstressed and stress-deprived tensile tendon, but only in stress-deprived tendon near bone. In overstressed and stress-deprived tensile tendon, levels of keratan sulfate, chondroitin 4-sulfate, and chondroitin 6-sulfate were increased. In overstressed tensile tendon, levels of ADAMTS-generated aggrecan catabolites were increased. There was increased matrix metalloproteinase 13 (MMP-13) and decreased fibromodulin and decorin expression in all regions. Increased MMP-1, MMP-9, MMP-14, and ADAMTS-1 expression, and decreased type II collagen expression were restricted to stress-deprived tendon. In stress-deprived boneattachment regions, messenger RNA (mRNA) for aggrecan was decreased, and ADAMTS was increased. In overstressed tensile tendon, aggrecan mRNA was increased, and ADAMTS was decreased.Conclusion. The distinct molecular changes in adjacent tissue implicate altered strain rather than humoral factors in controlling abnormal tenocyte metabolism, and highlight the importance of regional sampling. Tendon abnormalities induced by increased strain are accompanied by increased aggrecan, decreased ADAMTS, and low PG expression, which may negatively impact the structural integrity of the tissue and predispose to rupture.Injuries of the shoulder due to overuse are increasingly prevalent in both the sporting arena and the workplace. Occupational injury of the shoulder is second only to neck and low back pain in the frequency of consultation by general practitioners, with the most common injury involving the rotator cuff. (1,2) The prevalence of rotator cuff conditions increases with age, from 30-50% in the seventh decade of life to a staggering 70-80% by the ninth (3,4). Although most cases are treated conservatively, many patients undergo surgical repair with a prolonged convalescence. There are no drugs to specifically treat disorders of the rotator cuff or other tendons, and many surgical repairs fail within 12 months (5). Lack of knowledge of the fundamental mechanisms that underlie tendon breakdown results in limited and inadequate management options for tendon disorders.

Section: Discussionmentioning

confidence: 99%

Modulation of aggrecan and ADAMTS expression in ovine tendinopathy induced by altered strain

Sakurai

et al. 2008

Arthritis & Rheumatism

“…Certainly, biglycan and fibromodulin are fragmented in models of IVD degeneration and osteoarthritis (OA) [19,35] and in articular cartilage from total knee and hip replacement patients and from menisci of OA joints [17]. SLRPs are also extensively fragmented in pathological tendon and ligament [10,24,25]. Fragmentation of SLRPs may alter their function significantly, possibly rendering them more potent at stimulating inflammation.…”

Section: Introductionmentioning

confidence: 99%

A comparative evaluation of the small leucine-rich proteoglycans of pathological human intervertebral discs

Brown¹,

Melrose²,

Caterson³

et al. 2012

Eur Spine J

Purpose Proteoglycans are important to the functioning of the intervertebral disc. In addition to aggrecan there are the small leucine-rich proteoglycans (SLRPs). These are less common but in other locations their functions include collagen organisation, sequestering growth factors and stimulating inflammation. We have performed a comparative analysis of the SLRP core protein species present in intervertebral discs with various pathologies. Methods Eighteen intervertebral discs from patients with scoliosis (n = 7, 19-53 years), degenerative disc disease (n = 6, 35-51 years) and herniations (n = 5, 33-58 years) were used in this study. Proteoglycans were dissociatively extracted from disc tissues and the SLRPs (biglycan, decorin, fibromodulin, keratocan and lumican) assessed by Western blotting following deglycosylation with chondroitinase ABC and keratanase.

Journal Orthopaedic Research

“…8 Although GAG analysis alone does not determine what proportion of the chains are attached to aggrecan (compared to other CS/DS PG core proteins), purification steps such as gradient centrifugation and gel permeation chromatography, together with gel electrophoresis and protein sequence analysis, have been used to provide definitive evidence for the presence of aggrecan core protein in extracts of tendon. 3,9 Further, Western analysis with antibodies specific to known aggrecan core epitopes and neoepitopes 10 has shown the presence of both intact aggrecan and ADAMTS-generated fragments in the same tendon and ligament samples. 9,10 Aggrecan is most abundant in regions of tendon that experience mechanical compression and at tendon-bone insertion sites, 11 and proteolytically degraded aggrecan has also been identified by peptide analysis in tensional regions of normal adult tendons.…”

mentioning

confidence: 99%

“…3,9 Further, Western analysis with antibodies specific to known aggrecan core epitopes and neoepitopes 10 has shown the presence of both intact aggrecan and ADAMTS-generated fragments in the same tendon and ligament samples. 9,10 Aggrecan is most abundant in regions of tendon that experience mechanical compression and at tendon-bone insertion sites, 11 and proteolytically degraded aggrecan has also been identified by peptide analysis in tensional regions of normal adult tendons. 3 We have recently reported that diseased ligaments from horses with degenerative suspensory ligament desmitis (DSLD) contain highly elevated levels of intact aggrecan and fragments generated by ADAMTSaggrecanase activity.…”

mentioning

confidence: 99%

Murine tendon function is adversely affected by aggrecan accumulation due to the knockout of ADAMTS5

Wang

Bell

Thakore

et al. 2011

The present study examined the effect of ADAMTS5 (TS5) knockout on the properties of murine flexor digitorum longus (FDL) and Achilles tendons. FDL and Achilles tendons were analyzed using biomechanical testing, histology, and immunohistochemistry; further characterization of FDL tendons was conducted using transmission electron microscopy (collagen fibril ultrastructure), SDS-PAGE (collagen content and type), fluorescence-assisted carbohydrate electrophoresis for chondroitin sulfate and hyaluronan, and Western blotting for aggrecan, versican, and decorin abundance and distribution. FDL tendons of TS5 À/À mice showed a 33% larger cross-sectional area, increased collagen fibril area fraction, and decreased material properties relative to those of wild type mice. In TS5 À/À mice, aggrecan accumulated in the pericellular matrix of tendon fibroblasts. In Achilles tendons, cross-sectional area, stress relaxation, and structural properties were similar in TS5 À/À and wild type mice; however, the TS5 À/À tendons exhibited a higher tensile modulus and a weakened enthesis. These results demonstrate that TS5 deficiency disturbs normal tendon collagen organization and alters biomechanical properties. Hence, the role of ADAMTS5 in tendon is to remove pericellular and interfibrillar aggrecan to maintain the molecular architecture responsible for normal tissue function. ß