Tendinopathic Tissue Research Articles

Localization of advanced glycation end-products and their receptor in tendinopathic lesions.

This study was designed to investigate the accumulation of advanced glycation end-products (AGEs) and the expression of the receptor of AGEs (RAGE) in tendinopathic tissues. In this study, tendinopathic posterior tibial tendons (PTT) were collected from patients (n=6). Redundant autografts of flexor digitorum longus tendon (FDL; n=3) were used for controls. The control and tendinopathic tendon tissues were used for extraction of proteins for western blot and sectioned for histology and immunohistochemistry. Tendinopathy of the PTT was confirmed histologically by the presentation of disorderly organized collagen fibers, high cellularity and increased vascularity. By immunohistochemistry, heterogeneous accumulation of AGEs was detected on the PTT sections and concentrated in areas, where collagen fibers were disorderly and tangled. In the PTT, roundish tenocytes were also AGEs-positive. In contrast, AGEs were diffuse, lightly stained in the FDL. A greater number of tenocytes within the tendinopathic lesions in the PTT were RAGE positive, compared to the tenocytes in the FDL. Western blot confirmed the expression of AGEs and RAGE in both tendinopathic PTT and control FDL but their band densities were not significantly different. The spatial relation of the accumulated AGEs and RAGE- positive tenocytes within the tendinopathic lesions indicates their involvement in the molecular pathology of tendinopathy.

IDENTIFICATION OF HEALTHY AND TENDINOPATHIC CELL SUBTYPES IN FOOT AND ANKLE TENDONS USING SINGLE-CELL TRANSCRIPTOMICS

Tendinopathy can commonly occur around the foot and ankle resulting in isolated rupture, debilitating pain and degenerative foot deformity. The pathophysiology and key cells involved are not fully understood. This is partly because the dense collagen matrix that surrounds relatively few resident cells limits the ability of previous techniques to identify and target those cells of interest. In this study, we apply novel single cell RNA sequencing (CITE-Seq) techniques to healthy and tendinopathic foot/ankle tendons. For the first time we have identified multiple sub-populations of cells in human tendons. These findings challenge the view that there is a single principal tendon cell type and open new avenues for further study. Healthy tendon samples were obtained from patients undergoing tendon transfer procedures; including tibialis posterior and FHL. Diseased tendon samples were obtained during debridement of intractable Achilles and peroneal tendinopathy, and during fusion of degenerative joints. Single cell RNA sequencing with surface proteomic analysis identified 10 sub-populations of human tendon derived cells. These included groups expressing genes associated with fibro-adipogenic progenitors (FAPs) as well as ITGA7+VCAM1- recently described in mouse muscle but, as yet, not human tendon. In addition we have identified previously unrecognised sub-classes of collagen type 1 associated tendon cells. Each sub-class expresses a different set of extra-cellular matrix genes suggesting they each play a unique role in maintaining the structural integrity of normal tendon. Diseased tendon harboured a greater proportion of macrophages and cytotoxic lymphocytes than healthy tendon. This inflammatory response is potentially driven by resident tendon fibroblasts which show increased expression of pro-inflammatory cytokines. Finally, identification of a previously unknown sub-population of cells found predominantly in tendinopathic tissue offers new insight into the underlying pathophysiology. Further work aims to identify novel proteins targets for possible therapeutic pathways.

Use of Weight-Bearing Computed Tomography (WBCT) Imaging in the Assessment of the Achilles Tendinopathy: A Prospective Comparative and Controlled Study

Category: Hindfoot; Sports Introduction/Purpose: Insertional and non-insertional Achilles tendinopathy (AT) are prevalent diseases in the active, working-age population. Ultrasound (US) and magnetic resonance imaging (MRI) are frequently utilized in the assessment and grading of AT. Use of these imaging modalities are limited by operator interpretation/variability and costs, respectively. Also, these assessments are performed in the non-weight bearing positioning of the lower extremity, thus poorly evaluating the functional position of the loaded tendon. Validation of weight-bearing computed tomography (WBCT) for Achilles tendon imaging could provide a novel and functional means of quantifying tendon pathology. The study’s purposes were to: 1) Correlate Achilles tendon tissue structural findings when assessed by WBCT and US imaging, and 2) Compare WBCT Achilles tendon tissue changes between AT patients and controls. Methods: This was a prospective-comparative IRB-approved cohort study including 10 adults with AT (Age = 54.7 ± 10.3 years, BMI = 40.65 ± 10.07 kg/m2, 8F/2M), 10 age-matched controls (Age = 54.6 ± 11.33 years, BMI = 37.9 ± 9.55 kg/m2, 8F/2M), and 4 younger controls (Age = 32.25 ± 8.3 years, BMI = 24.32 ± 5.14 kg/m2, 2F/2M). WBCT scans (Curvebeam HiRise/PedCAT) and US imaging (Butterfly iQ+) of the Achilles tendon were collected. Tendons were manually segmented in WBCT images (3D Slicer software) and tendon thickness was measured at the maximum anterior-posterior (AP) diameter of the tendon (insertion and midportion regions). Radiodensity was quantified by the average Hounsfield Units (HU) of each tendon region and normalized to the radiodensity of each participant’s talus (segmented using Disior Bonelogic). US measures of the tendon thickness were similarly completed by independent observers who were blinded to the WBCT measurement. Intraclass correlation coefficient (ICC) assessed correlation between WBCT and US findings. Paired T-tests compared WBCT HU between patients and controls. P-values < 0.05 were considered significant. Results: There was excellent correlation (ICC= 0.83-0.94, Table 1) between WBCT and US imaging regarding tendon thickness, with WBCT overestimating thickness by only 0.27-0.55mm (4-9% of total tendon thickness). These findings could be explained by decreased US tendon thickness measurements secondary to the tendon’s compression by the US probe. WBCT imaging demonstrated a higher radiodensity (HU) within the Achilles tendon (for both insertion and midportion regions) in AT patients when compared to controls (Table 2), with p-values of 0.009 and 0.001 for insertional and midportion regions, respectively. Findings are consistent with tendinopathic differentiation of the Achilles tendon substance in the AT patients. Color-coded maps demonstrating HU distributions across the Achilles tendon were created to facilitate interpretation of tissue characteristics (Fig. 1). Conclusion: In this prospective, comparative, and controlled study, we observed a high correlation between US and WBCT imaging in the assessment of Achilles tendon thickness in AT patients and controls. We also found that WBCT HU distribution in the Achilles tendon was significantly increased in the AT patients when compared to controls. Findings are likely explained by tendinopathic tissue changes in the diseased tendons, potentially related to the well-known chondroid metaplasia observed in Achilles tendinopathy pathological process. WBCT imaging and color-coded maps can represent a promising tool in the assessment of AT patients.

Disruption of day-to-night changes in circadian gene expression with chronic tendinopathy.

Overuse injury in tendon tissue (tendinopathy) is a frequent and costly musculoskeletal disorder and represents a major clinical problem with unsolved pathogenesis. Studies in mice have demonstrated that circadian clock-controlled genes are vital for protein homeostasis and important in the development of tendinopathy. We performed RNA sequencing, collagen content and ultrastructural analyses on human tendon biopsies obtained 12h apart in healthy individuals to establish whether human tendon is a peripheral clock tissue and we performed RNA sequencing on patients with chronic tendinopathy to examine the expression of circadian clock genes in tendinopathic tissues. We found time-dependent expression of 280 RNAs including 11 conserved circadian clock genes in healthy tendons and markedly fewer (23) differential RNAs with chronic tendinopathy. Further, the expression of COL1A1 and COL1A2 was reduced at night but was not circadian rhythmic in synchronised human tenocyte cultures. In conclusion, day-to-night changes in gene expression in healthy human patellar tendons indicate a conserved circadian clock as well as the existence of a night reduction in collagen I expression. KEY POINTS: Tendinopathy is a major clinical problem with unsolved pathogenesis. Previous work in mice has shown that a robust circadian rhythm is required for collagen homeostasis in tendons. The use of circadian medicine in the diagnosis and treatment of tendinopathy has been stifled by the lack of studies on human tissue. Here, we establish that the expression of circadian clock genes in human tendons is time dependent, and now we have data to corroborate that circadian output is reduced in diseased tendon tissues. We consider our findings to be of significance in advancing the use of the tendon circadian clock as a therapeutic target or preclinical biomarker for tendinopathy.

Shear wave elastography imaging in a porcine tendinopathy model.

To quantify the effect of structural damage in an ex vivo animal tendinopathy model using shear wave elastography (SWE). Sixteen porcine flexor tendons were injected with a 0.05mL bolus of 1.5% collagenase solution to induce focal structural damage without surfacing tears. Control tendons were injected with saline (n = 16). Eight tendons from each group were incubated at 37°C for 3.5h while the remaining 8 from each group were incubated for 7h. Tendons were mechanically stretched to 0% and 1% strain. Simultaneously, SWE was acquired proximal to, at, and distal to the injection site using a clinical ultrasound scanner. There were significant differences in SWS (saline > collagenase) at 1% strain and 7-h incubation for all three locations (PROX p = 0.0031, ROI p = 0.001, DIST p = 0.0043). There were also significant differences at 0% strain and 7h, but only at (p = 0.0005), and distal to (p = 0.0035), the injection site. No statistically significant differences were observed for 3.5-h incubation, at 0% or 1% strain. Collagenase-mediated structural damage does appear to convey decreased tissue elasticity on SWE when ex vivo tendons are incubated for 7h. These findings suggest that SWE may be a useful tool for predicting ultimate tissue strength in tendinopathic tissues. Pull-to-failure testing should be performed in the future and are expected to show that tendons with decreased SWS, and, therefore, decreased elasticity, rupture at lower pulls forces.

Scleraxis and collagen I expression increase following pilot isometric loading experiments in a rodent model of patellar tendinopathy

The effect of mechanical load on tendinopathic tissue is usually studied in the context of identifying mechanisms responsible for tendon degradation. However, loading is also one of the most common treatments for tendinopathy. It is therefore possible that different loads result in different cellular responses within a tendon. To test this hypothesis, we first established a rodent model of tendinopathy that has a transcriptional signature similar to human tendinopathy. Tendinopathy was modeled in the rat by producing a lesion in the central core of the patellar tendon using a biopsy punch, followed by two weeks to allow scar formation. We performed 3’ Tag RNA-Seq to identify genes that were differentially expressed between the native and scarred rat patellar tendon. Genes involved in extracellular matrix (ECM) structure and turnover were increased, mitochondrial genes were decreased, and there was no inflammatory signature in the tendinopathic tissue. These transcriptional changes phenocopy previously published whole transcriptome analysis in human tendinopathy. After validating the model, the initial response to injury and loading was determined. Two weeks after creation of the patellar tendon lesion, the tendon was loaded using either 4 × 30s isometric or a time-under-tension matched (360 × 0.33s) dynamic protocol. Injured +/- loading and contralateral control tendons were collected eighteen hours after loading, RNA was extracted, and gene expression was quantified using qRT-PCR of the scar with or without loading. The expression of scleraxis and type I collagen increased following isometric loading relative to those loaded dynamically. By contrast, the expression of type II collagen increased in the dynamic samples relative to those loaded isometrically. These data suggest that dynamic loading of a central core tendon injury increases fibrocartilage markers, whereas long isometric loads stimulate markers of tendon regeneration.

Interleukin-17 Cytokines and Receptors: Potential Amplifiers of Tendon Inflammation.

Interleukin (IL)-17A, a pro-inflammatory cytokine that is linked to the pathology of several inflammatory diseases, has been shown to be upregulated in early human tendinopathy and to mediate inflammatory and tissue remodelling events. However, it remains unclear which cells in tendons can respond to IL-17A, and how IL-17A, and its family members IL-17F and IL-17AF, can affect intracellular signalling activation and mRNA expression in healthy and diseased tendon-derived fibroblasts. Using well-phenotyped human tendon samples, we show that IL-17A and its receptors IL-17RA and IL-17RC are present in healthy hamstring, and tendinopathic and torn supraspinatus tendon tissue. Next, we investigated the effects of IL-17A, IL-17F, or IL-17AF on cultured patient-derived healthy and diseased tendon-derived fibroblasts. In these experiments, IL-17A treatment significantly upregulated IL6, MMP3, and PDPN mRNA expression in diseased tendon-derived fibroblasts. IL-17AF treatment induced moderate increases in these target genes, while little change was observed with IL-17F. These trends were reflected in the activation of intracellular signalling proteins p38 and NF-B p65, which were significantly increased by IL-17A, modestly increased by IL-17AF, and not increased by IL-17F. In combination with TNF-α, all three IL-17 cytokines induced IL6 and MMP3 mRNA expression to similar levels. Therefore, this study confirms that healthy and diseased tendon-derived fibroblasts are responsive to IL-17 cytokines and that IL-17A induces the most profound intracellular signalling activation and mRNA expression of inflammatory genes, followed by IL-17AF, and finally IL-17F. The ability of IL-17 cytokines to induce a direct response and activate diverse pro-inflammatory signalling pathways through synergy with other inflammatory mediators suggests a role for IL-17 family members as amplifiers of tendon inflammation and as potential therapeutic targets in tendinopathy.

Can Achilles tendon xanthoma be distinguished from Achilles tendinopathy using Dixon method MRI? A cross-sectional exploratory study

BackgroundFamilial hypercholesterolemia is a genetic condition characterized by life-long elevations of plasma low-density lipoprotein cholesterol. In addition to life-threatening cardiovascular complications, intratendinous cholesterol deposits (xanthomas) can lead to pain and tendon thickening, particularly in the Achilles. Clinical detection of xanthomas currently relies upon visual assessment and palpation, or ultrasound-based measures of tendon thickening or echotexture. Misdiagnosis of xanthoma can delay the commencement of potentially life-saving lipid-lowering therapy. Our primary purpose was to determine whether analysis of separated fat and water magnetic resonance images may be able to differentiate between xanthomatic and nonxanthomatic Achilles tendons through quantification of intratendinous fat content. The main hypothesis was that Achilles tendon xanthomas will demonstrate greater lipid content than Achilles tendinopathy or healthy control tendons.MethodsBilateral MRI scans of Achilles tendons from 30 participants (n = 10 Achilles tendon xanthoma, n = 10 Achilles overuse tendinopathy, n = 10 healthy controls) were analyzed for total lipid content using the Dixon method of fat and water signal separation. Secondary outcome measures included tendon water content, as well as ultrasound characterization of tendon tissue organization and thickness.ResultsFat content was greater in Achilles tendon xanthomas compared to the tendinopathy (p < 0.0001) and control groups (p < 0.0001). Water content was also greater in Achilles tendon xanthomas compared to the tendinopathy (p < 0.0001) and control groups (p = 0.0002). Ultrasound tissue characterization revealed worse tissue organization in Achilles tendon xanthoma tendons compared to Achilles tendinopathy (p < 0.05) but demonstrated largely overlapping distributions. Achilles tendon xanthoma tendons were, on average, significantly thicker than the tendons of the other two groups (p < 0.01 and p < 0.001, respectively).ConclusionMRI-derived measures of Achilles tendon fat content may be able to distinguish xanthomas from control and tendinopathic tissue. Dixon method MRI warrants further evaluation in an adequately powered study to develop and test clinically relevant diagnostic thresholds.

Novel self-amplificatory loop between T cells and tenocytes as a driver of chronicity in tendon disease

ObjectivesIncreasing evidence suggests that inflammatory mechanisms play a key role in chronic tendon disease. After observing T cell signatures in human tendinopathy, we explored the interaction between T cells and...

POS0020 EFFICACY AND SAFETY OF SECUKINUMAB IN PATIENTS WITH ROTATOR CUFF TENDINOPATHY: A 24-WEEK, RANDOMISED, DOUBLE-BLIND, PLACEBO-CONTROLLED, PHASE II PROOF-OF-CONCEPT TRIAL

Background:Rotator cuff tendinopathy (RC TP) is a multifactorial condition and one of the most common causes of musculoskeletal burden. Current standard of care (SoC) is limited to pain relief with NSAIDs and physiotherapy. Recent evidence indicates that IL-17A-expressing tendon-resident immune cells are present in human overuse tendinopathy, and IL-17A levels are increased in early human tendinopathic tissue samples [1, 2]. Secukinumab (SEC) is a fully human, monoclonal antibody that binds to and neutralises IL-17A.Objectives:To evaluate the efficacy and safety of SEC in patients with active overuse RC TP refractory to oral NSAIDs/acetaminophen, physiotherapy or corticosteroid injections.Methods:96 patients with symptomatic RC TP with no or &lt;50% rupture were randomly assigned to receive seven subcutaneous injections of SEC 300 mg or placebo (PBO) at baseline and Weeks 1, 2 and 3, followed by every 4 weeks starting at Week 4. The primary endpoint was change from baseline in the Western Ontario Rotator Cuff (WORC) index score at Week 14 for SEC vs PBO (two-sided p&lt;0.1). Secondary endpoints included, visual analogue scale (VAS) pain score, Disability of Arm, Shoulder and Hand Questionnaire (QuickDASH) score, American Shoulder and Elbow Surgeons Shoulder Evaluation Form (ASES), EQ-5D-5L score and patient global assessment (PGA) score. All endpoints were assessed through 24 weeks.Results:Clinically relevant improvement in both SEC and PBO groups on top of SoC treatment was observed, with no statistically significant difference demonstrated in the full study population on physical symptoms and function (Table 1). Similar results were observed in the secondary endpoints with marked improvement in both groups over time. Exploratory post-hoc analyses in a subpopulation of 39% of the study subjects with non-acute, moderate to severe disease, SEC provided significant and clinically relevant improvements vs PBO through Week 24 in total WORC score (overall treatment difference: 19.2, p &lt;0.01) and pain (VAS, overall treatment difference: 15, p = 0.02) with early effect observed after two weeks (Figure 1). A favourable treatment effect in the more severe subgroup was demonstrated in other patient-reported outcomes. No serious adverse events were reported.Conclusion:Although SEC did not demonstrate a significant benefit vs PBO in the overall patient population with active overuse RC TP, SEC did provide benefit in the subpopulation with non-acute, moderate to severe disease. Larger clinical trials of SEC in this area are warranted.

Stromal “activation” markers do not confer pathogenic activity in tendinopathy

Tendinopathy is a highly prevalent musculoskeletal pathology associated with incremental injury as result of repetitive microtrauma. We sought to explore the physiological significance of stromal “activation” signatures in a human model of tendinopathy. Torn supraspinatus tendon and matched intact subscapularis tendon biopsies were collected from patients undergoing shoulder surgery while healthy tendon was collected from patients undergoing anterior cruciate ligament (ACL) reconstruction. Expression of stromal activation markers was analyzed at transcript/protein level using qRT-PCR and immunohistochemistry. Gene expression of stromal activation markers was silenced by siRNA-mediated knockdown or induced by IL-1β stimulation. Expression of “activation” markers podoplanin, VCAM-1 and CD248 was identified in human tendon tissue. Podoplanin and VCAM-1 expression were significantly increased in tendinopathic tissue. Knockdown of podoplanin and VCAM-1 in normal and tendinopathic tenocytes did not have any significant effect on expression of matrix genes COL1A1, COL3A1, TNC, or DCN. Similarly, no changes in release of inflammatory mediators IL-6, IL-8, and CCL2 were observed in podoplanin/VCAM-1 knockdown cultures. Our data suggest that silencing expression of stromal “activation” markers does not affect the intrinsic inflammatory profile or matrix regulatory behavior of tenocytes. We propose that the term “activation” is more appropriately reflected by alterations in tenocyte behavior that induce changes in the stromal microenvironment and overall tissue architecture rather than identification through potentially arbitrary phenotypic traits.

S100A8 & S100A9: Alarmin mediated inflammation in tendinopathy

Alarmins S100A8 and S100A9 are endogenous molecules released in response to environmental triggers and cellular damage. They are constitutively expressed in immune cells such as monocytes and neutrophils and their expression is upregulated under inflammatory conditions. The molecular mechanisms that regulate inflammatory pathways in tendinopathy are largely unknown therefore identifying early immune effectors is essential to understanding the pathology. Based on our previous investigations highlighting tendinopathy as an alarmin mediated pathology we sought evidence of S100A8 & A9 expression in a human model of tendinopathy and thereafter, to explore mechanisms whereby S100 proteins may regulate release of inflammatory mediators and matrix synthesis in human tenocytes. Immunohistochemistry and quantitative RT-PCR showed S100A8 & A9 expression was significantly upregulated in tendinopathic tissue compared with control. Furthermore, treating primary human tenocytes with exogenous S100A8 & A9 significantly increased protein release of IL-6, IL-8, CCL2, CCL20 and CXCL10; however, no alterations in genes associated with matrix remodelling were observed at a transcript level. We propose S100A8 & A9 participate in early pathology by modulating the stromal microenvironment and influencing the inflammatory profile observed in tendinopathy. S100A8 and S100A9 may participate in a positive feedback mechanism involving enhanced leukocyte recruitment and release of pro-inflammatory cytokines from tenocytes that perpetuates the inflammatory response within the tendon in the early stages of disease.

Matrix stiffness regulates the differentiation of tendon-derived stem cells through FAK-ERK1/2 activation

Tendon derived stem cells (TDSCs) were vital in tendon homeostasis. Nevertheless, the regulation of TDSCs differentiation in tendinopathy is unclear. Matrix stiffness modulated stem cells differentiation, and matrix stiffness of tendinopathic tissues decreased significantly. In order to clarify the role of matrix stiffness in TDSCs differentiation, they were cultured on the gelatin hydrogels with the stiffness from 2.34 ± 1.48 kPa to 24.09 ± 14.03 kPa. The effect of matrix stiffness on TDSCs proliferation and differentiation were investigated with CCK8 assay, immunofluorescences, real time PCR and western blot. It was found the proliferation of TDSCs increased and more stress fibers formed with increasing matrix stiffness. The differentiation of TDSCs into tenogenic, chondrogenic, and osteogenic lineages were inhibited on stiff hydrogel evidenced by reduced expression of tenocyte markers THBS4, TNMD, SCX, chondrocyte marker COL2, and osteocyte markers Runx2, Osterix, and ALP. Furthermore, the phosphorylation of FAK and ERK1/2 were enhanced when TDSCs grew on stiff hydrogel. After FAK or ERK1/2 was inhibited, the effect of matrix stiffness on differentiation of TDSCs was inhibited as well. The above results indicated matrix stiffness modulated the proliferation and differentiation of TDSCs, and the regulation effect could correlate to the activation of FAK or ERK1/2.

Characteristics of tendon derived stem cells according to different factors to induce the tendinopathy.

Tendon derived stem cells (TDSCs) have been used as a therapeutic agent and as a healing marker. However, there has been no study about the characteristics of TDSCs extracted from tendinopathic tendon tissues. The aim of this study was to find the different characteristics of TDSCs according to the factors to induce the tendinopathy. Five- and fifteen-week old Sprague Dawley rats were used for this study and chemically-induced and injury-induced tendinopathy models were made depending on the age of the animal for different types of tendinopathy. TDSCs from chemically-induced tendinopathy showed markedly low proliferation compared to those from age-matched normal control and injury-induced tendinopathy. In addition, TDSCs from chemically-induced tendinopathy progressed to osteogenesis under an osteogenic differentiation environment more than those from other groups. In contrast, TDSCs from injury-induced tendinopathy showed markedly high proliferation and high expression of type III collagen and α-SMA compared to other groups. Adipogenic potentials in TDSCs from injury-induced tendinopathy were also higher. These different characteristics might be helpful in the development new therapeutic agents for tendon regeneration according to different factors to induce the tendinopathy.

Ultrasonic Percutaneous Tenotomy of Common Extensor Tendons for Recalcitrant Lateral Epicondylitis.

Tennis elbow is a common musculoskeletal condition affecting middle-aged patients with symptoms usually lasting from 6 months to 2 years. The vast majority of individuals will respond to conservative therapy; however, some will require surgical intervention. A new treatment system has been developed for use with ultrasound guidance in the ultrasonic microresection of tendinopathic tissue. This technology has been implemented in the TX1 Tissue Removal System and is used to treat various tendinopathies by debridement using targeted ultrasonic energy. We describe the surgical technique for the TX1 system as well as provide pain and functional outcome scores for a series of patients with recalcitrant lateral epicondylitis treated with percutaneous tenotomy with ultrasonic energy utilizing ultrasound guidance.

Efficacy and Safety of a Percutaneous Tenotomy System for Debridement of Tendinopathic Tissues.

During acute inflammatory phases of tendinopathy, a combination of physical therapy and corticosteroid injections is considered to be moderately effective for acute inflammation. However, surgical debridement of tendinopathic tissues is often required for chronic cases. The TenJet system created by HydroCision, Inc. is a percutaneous device that uses high-pressure saline to debride pathologic tissues during tenotomy. Here, we use a collagenase-induced tendinopathy model on explants from bovine ankle extensor tendons. We use the volume of defect debrided as a metric to determine the efficacy of using high-velocity fluid flow as a debridement tool as well as the effect of velocity magnitude on efficacy. Furthermore, we highlight the negligible disruption of healthy tissue surrounding pathologic tissue.

Effects of anti-inflammatory (NSAID) treatment on human tendinopathic tissue.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat tendinopathy, but evidence for this treatment is lacking, and little is known regarding effects of NSAIDs on human tendinopathic tendon. This study investigated the effects of NSAID treatment (ibuprofen) on human tendinopathic tendon, with changes in gene expression as the primary outcome, and tendon pain, function, and blood flow as secondary outcomes. Twenty-six adults (16 men, 10 women), diagnosed with chronic Achilles tendinopathy, were randomized to 1-wk treatment with ibuprofen (600 mg ×3/day) (n = 13) or placebo (n = 13) (double-blinded). Ibuprofen content in blood, visual analog scale score for tendon pain at rest and activity, Victorian Institute of Sports Assessment-Achilles (VISA-A) scores for tendon function, tendon thickness (with ultrasonography), and color Doppler were measured before and 1 h after treatment. After the last posttreatment test, a full-width tendon biopsy was taken from the affected area. Real-time-RT-PCR was used to assess expression of collagen I, collagen III, transforming growth factor (TGF-β) isoforms, cyclooxygenase-2 (COX-2), angiopoietin-like 4 (ANGPTL4), and cyclic AMP-dependent transcription factor (ATF3) in tendon tissue. Expression of collagens and TGF-β isoforms showed relatively low variation and was unaffected by ibuprofen treatment. Further, no changes were seen in tendon thickness or VISA-A score. The placebo treatment reduced the color Doppler (in tendon plus surrounding tissue) compared with the ibuprofen group and also increased the perception of pain at rest. In conclusion, there was no indication that short-term ibuprofen treatment affects gene expression in human chronic tendinopathic tendon or leads to any clear changes in tendon pain or function.NEW & NOTEWORTHY Nonsteroidal anti-inflammatory drugs are widely used in the treatment of tendinopathy, but little is known of the effects of these drugs on tendon tissue. We find that 1 wk of ibuprofen treatment has no effect on gene expression of collagen and related growth factors in adult human tendinopathic tendon in vivo (in spite of relatively low levels of variation in gene expression), suggesting that tendinopathic cells are not responsive to ibuprofen.

Development of overuse tendinopathy: A new descriptive model for the initiation of tendon damage during cyclic loading.

Tendinopathic tissue has long been characterized by changes to collagen microstructure. However, initial tendon damage from excessive mechanical loading-a hallmark of tendinopathy development-could occur at the nanoscale level of collagen fibrils. Indeed, it is on this scale that tenocytes interact directly with tendon matrix, and excessive collagen fibril damage not visible at the microscale could trigger a degenerative cascade. In this study, we explored whether initiation of tendon damage during cyclic loading occurs via a longitudinal compression-induced buckling mechanism of collagen fibrils leading to nanoscale kinkband development. Two groups of tendons were cyclically loaded to equivalent peak stresses. In each loading cycle, tendons in one group were unloaded to the zero displacement mark, while those in the other group were unloaded to a nominal level of tension, minimizing the potential for fibril buckling. Tendons that were unloaded to the zero displacement mark ruptured significantly sooner during cyclic loading (1,446 ± 737 vs. 4,069 ± 1,129 cycles), indicating that significant fatigue damage is accrued in the low stress, toe region of the load-deformation response. Ultrastructural analysis using scanning electron microscopy of tendons stopped after 1,000 cycles showed that maintaining a nominal tension slowed the accumulation of kinkbands, supporting a longitudinal compression-induced buckling mechanism as the basis for kinkband development. Based on our results, we present a new descriptive model for the initiation of tendon damage during cyclic loading. The so-called Compression of Unrecovered Elongation or CUE Model may provide useful insight into the development of tendinopathy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:467-476, 2018.

Presence of Bacteria in Spontaneous Achilles Tendon Ruptures

Background: The structural pathology of Achilles tendon (AT) ruptures resembles tendinopathy, but the causes remain unknown. Recently, a number of diseases were found to be attributed to bacterial infections, resulting in low-grade inflammation and progressive matrix disturbance. The authors speculate that spontaneous AT ruptures may also be influenced by the presence of bacteria. Hypothesis: Bacteria are present in ruptured ATs but not in healthy tendons. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Patients with spontaneous AT ruptures and patients undergoing anterior cruciate ligament (ACL) reconstruction were recruited for this study. During AT surgical repair, excised tendinopathic tissue was collected, and healthy tendon samples were obtained as controls from hamstring tendon grafts used in ACL reconstruction. Half of every sample was reserved for DNA extraction and the other half for histology. Polymerase chain reaction (PCR) was conducted using 16S rRNA gene universal primers, and the PCR products were sequenced for the identification of bacterial species. A histological examination was performed to compare tendinopathic changes in the case and control samples. Results: Five of 20 AT rupture samples were positive for the presence of bacterial DNA, while none of the 23 hamstring tendon samples were positive. Sterile operating and experimental conditions and tests on samples, controlling for harvesting and processing procedures, ruled out the chance of postoperative bacterial contamination. The species identified predominantly belonged to the Staphylococcus genus. AT rupture samples exhibited histopathological features characteristic of tendinopathy, and most healthy hamstring tendon samples displayed normal tendon features. There were no apparent differences in histopathology between the bacterial DNA–positive and bacterial DNA–negative AT rupture samples. Conclusion: The authors have demonstrated the presence of bacterial DNA in ruptured AT samples. It may suggest the potential involvement of bacteria in spontaneous AT ruptures.

Resorbable electrospun polydioxanone fibres modify the behaviour of cells from both healthy and diseased human tendons.

Chronic tendinopathy in an active and ageing population represents an increasing burden to healthcare systems. Rotator cuff tendinopathy alone accounts for approximately 70 % of all shoulder pain. Tendinopathic tissue has a disorganised extracellular matrix, altered vasculature, and infiltration of fibroblasts and inflammatory cells. This altered biology may contribute to the limited success of surgical repair strategies. Electrospun resorbable scaffolds can potentially enhance endogenous repair mechanisms by influencing the tissue microenvironment. Polydioxanone (PDO) has an established safety profile in patients. We compared the response of healthy and diseased human tendon cells to electrospun PDO fibres using live cell imaging, proliferation, flow cytometry, and gene expression studies. Within 4 h of initial contact with electrospun PDO, healthy tendon cells underwent a marked transformation; elongating along the fibres in a fibre density dependent manner. Diseased tendon cells initially responded at a slower rate, but ultimately underwent a similar morphological change. Electrospun fibres increased the proliferation rate of diseased tendon cells and increased the ratio of type I:IIIcollagenmRNA expression. Flow cytometry revealed decreased expression of CD106, a marker of mesenchymal stem cells, and increased expression of CD10 on healthy versus diseased tendon cells. PDO electrospun scaffolds further promoted CD106negCD10pos expression of healthy tendon cells. Despite their behavioural differences, both healthy and diseased human tendon cells responded to electrospun PDO fibres. This encourages further work establishing their efficacy in augmenting surgical repair of diseased tendons.