Cytokines and apoptosis in supraspinatus tendinopathy

Biologic Adjuvants to Rotator Cuff Repairs Induce Anti-inflammatory Macrophage 2 Polarization and Reduce Inflammatory Macrophage 1 Polarization In Vitro

PURPOSE

To examine the effect of various biologic adjuvants on the polarization of macrophages in an in vitro model for rotator cuff tears.

METHODS

Tissue was harvested from 6 patients undergoing arthroscopic rotator cuff repair. An in vitro model of the supraspinatus and subacromial bursa was created and treated with control, platelet-rich plasma (PRP), autologous activated serum (AAS), or a combination of PRP+AAS. The effect of treatment on macrophage polarization between M1 proinflammatory macrophages or M2 anti-inflammatory macrophages was measured using gene expression, protein expression, flow cytometry, and nitric oxide production.

RESULTS

Tendon and bursa treated with PRP, AAS, and PRP+AAS significantly decreased the gene expression of M1 markers interleukin (IL)-12 and tumor necrosis factor-alpha while significantly increasing the expression of M2 markers arginase, IL-10, and transforming growth factor-β (P < .05) compared with treatment with control. Enzyme-linked immunosorbent assay analysis of protein production demonstrated that, compared with control, coculture treated with PRP, AAS, and PRP+AAS significantly decreased markers of M1-macrophages (IL-6, IL-12, and tumor necrosis factor-alpha) while significantly increasing the expression of markers of M2-macrophages (arginase, IL-10, and transforming growth factor-beta) (P < .05). Flow cytometry analysis of surface markers demonstrated that compared with control, tendon and bursa treated with PRP, AAS, and PRP+AAS significantly decreased markers of M1-macrophages (CD80, CD86, CD64, CD16) while significantly increasing the expression of markers of M2-macrophages (CD163 and CD206) (P < .05). Treatment of the coculture with PRP, AAS, and PRP+AAS consistently demonstrated a decrease in nitric oxide production (P < .05) compared with control. AAS and PRP+AAS demonstrated an increased macrophage shift to M2 compared with PRP alone, whereas there was not as uniform of a shift when comparing PRP+AAS with AAS alone.

CONCLUSIONS

In an in vitro model of rotator cuff tears, the treatment of supraspinatus tendon and subacromial bursa with PRP, AAS, and PRP+AAS demonstrated an increase in markers of anti-inflammatory M2-macrophages and a concomitant decrease in markers of proinflammatory M1-macrophages. AAS and PRP+AAS contributed to a large shift to macrophage polarization to the anti-inflammatory M2 compared with PRP.

CLINICAL RELEVANCE

The mechanism of biologic adjuvant effects on the rotator cuff remains poorly understood. This study suggests that they may contribute to polarization of macrophages for their proinflammatory (M1) state to the anti-inflammatory (M2) state.

Successive tendon injury in an in vivo rat overload model induces early damage and acute healing responses

Introduction: Tendinopathy is a degenerative condition resulting from tendons experiencing abnormal levels of multi-scale damage over time, impairing their ability to repair. However, the damage markers associated with the initiation of tendinopathy are poorly understood, as the disease is largely characterized by end-stage clinical phenotypes. Thus, this study aimed to evaluate the acute tendon responses to successive fatigue bouts of tendon overload using an in vivo passive ankle dorsiflexion system. Methods: Sprague Dawley female rats underwent fatigue overloading to their Achilles tendons for 1, 2, or 3 loading bouts, with two days of rest in between each bout. Mechanical, structural, and biological assays were performed on tendon samples to evaluate the innate acute healing response to overload injuries. Results: Here, we show that fatigue overloading significantly reduces in vivo functional and mechanical properties, with reductions in hysteresis, peak stress, and loading and unloading moduli. Multi-scale structural damage on cellular, fibril, and fiber levels demonstrated accumulated micro-damage that may have induced a reparative response to successive loading bouts. The acute healing response resulted in alterations in matrix turnover and early inflammatory upregulations associated with matrix remodeling and acute responses to injuries. Discussion: This work demonstrates accumulated damage and acute changes to the tendon healing response caused by successive bouts of in vivo fatigue overloads. These results provide the avenue for future investigations of long-term evaluations of tendon overload in the context of tendinopathy.

Rotator Cuff Tendinopathy: Pathways of Apoptosis

Rotator cuff repair is usually successful, but retear is not uncommon. It has been previously identified that there is a higher incidence of apoptosis in the edges of the torn supraspinatus tendon. A prospective cohort study was conducted with 28 patients-14 rotator cuff tear patients, 5 instability patients, and 9 Anterior cruciate ligament reconstruction patients to determine whether there was any increase in several genes implicated in apoptosis, including Fas receptor (FasR), Fas ligand, Aifm-1, Bcl-2, Fadd, Bax, and caspase-3. There was a significant expression of Bax (P=0.2) and FasR (P=0.005) in the edges of torn supraspinatus tendons, and in intact subscapularis tendons, there was a significant expression of caspase-3 (P=0.02) compared with samples from the torn supraspinatus tendon (P=0.04). The cytochrome c pathway, with its subsequent activation of caspase-3, as well as the TRAIL-receptor signaling pathway involving FasR have both been implicated. The elevated expression of Bax supported the model that the Bax to Bcl-2 expression ratio represents a cell death switch. The elevated expression of Bax in the intact subscapularis tissue from rotator cuff tear patients also may confirm that tendinopathy is an ongoing molecular process.

Risk of rotator cuff tear and rotator cuff repair surgery comparison between sodium-glucose cotransporter 2 inhibitors and glucagon like peptide-1 receptor agonists: A real-world study

AIM

Theoretically, sodium-glucose cotransporter 2 inhibitors (SGLT2is) reduce the risk of rotator cuff tear through an anti-inflammatory mechanism. To clarify this association, in this study, we compared SGLT2is users and glucagon-like peptide-1 receptor agonists (GLP-1RAs) users in terms of the risk of rotator cuff tear and the risk of receiving rotator cuff repair surgery.

METHODS

A retrospective cohort analysis was conducted using data from the TriNetX platform. A target trial design was adopted to identify patients with type 2 diabetes mellitus who started receiving SGLT2is or GLP-1RAs. Propensity score matching was used to form two homogeneous groups. The study outcomes were the risk of rotator cuff tear and the risk of receiving rotator cuff repair surgery. Hazard ratios (HRs) with 95 % confidence intervals (CIs) were calculated within the TriNetX platform.

RESULTS

Initially, 351,800 SGLT2is users and 387,616 GLP-1RAs users were identified. After propensity score matching, each group comprised 274,026 patients. The mean age was 59.5 years in both groups; the proportions of women in the SGLT2is and GLP-1RAs groups were 46.9 % and 46.7 %, respectively. Compared with the GLP-1RAs group, the SGLT2is group had significantly reduced risks of rotator cuff tear (HR 0.812 [0.761;0.867]) and rotator cuff repair surgery (HR 0.900 [0.815;0.994]).

CONCLUSION

SGLT2is appear to reduce the risk of rotator cuff tear and the risk of receiving rotator cuff repair surgery in patients with type 2 diabetes mellitus. Further prospective studies are needed to validate our findings.

Biology and physiology of tendon healing

Tendon disorders affect people of all ages, from elite and recreational athletes and workers to elderly patients. After an acute injury, 3 successive phases are described to achieve healing: an inflammatory phase followed by a proliferative phase, and finally by a remodeling phase. Despite this process, healed tendon fails to recover its original mechanical properties. In this review, we proposed to describe the key factors involved in the process such as cells, transcription factors, extracellular matrix components, cytokines and growth factors and vascularization among others. A better understanding of this healing process could help provide new therapeutic approaches to improve patients' recovery while tendon disorders management remains a medical challenge.

Pro-Resolving Mediators in Rotator Cuff Disease: How Is the Bursa Involved?

So far, tendon regeneration has mainly been analyzed independent from its adjacent tissues. However, the subacromial bursa in particular appears to influence the local inflammatory milieu in the shoulder. The resolution of local inflammation in the shoulder tissues is essential for tendon regeneration, and specialized pro-resolving mediators (SPMs) play a key role in regulating the resolution of inflammation. Here, we aimed to understand the influence of the bursa on disease-associated processes in neighboring tendon healing. Bursa tissue and bursa-derived cells from patients with intact, moderate and severe rotator cuff disease were investigated for the presence of pro-resolving and inflammatory mediators, as well as their effect on tenocytes and sensitivity to mechanical loading by altering SPM signaling mediators in bursa cells. SPM signal mediators were present in the bursae and altered depending on the severity of rotator cuff disease. SPMs were particularly released from the bursal tissue of patients with rotator cuff disease, and the addition of bursa-released factors to IL-1β-challenged tenocytes improved tenocyte characteristics. In addition, mechanical loading modulated pro-resolving processes in bursa cells. In particular, pathological high loading (8% strain) increased the expression and secretion of SPM signaling mediators. Overall, this study confirms the importance of bursae in regulating inflammatory processes in adjacent rotator cuff tendons.

The Genetic Association with Athlete Status, Physical Performance, and Injury Risk in Soccer

The aim of this review was to critically appraise the literature concerning the genetic association with athlete status, physical performance, and injury risk in soccer. The objectives were to provide guidance on which genetic markers could potentially be used as part of future practice in soccer and to provide direction for future research in this area. The most compelling evidence identified six genetic polymorphisms to be associated with soccer athlete status (ACE I/D; ACTN3 rs1815739; AGT rs699; MCT1 rs1049434; NOS3 rs2070744; PPARA rs4253778), six with physical performance (ACTN3 rs1815739; AMPD1 rs17602729; BDNF rs6265; COL2A1 rs2070739; COL5A1 rs12722; NOS3 rs2070744), and seven with injury risk (ACTN3 rs1815739; CCL2 rs2857656; COL1A1 rs1800012; COL5A1 rs12722; EMILIN1 rs2289360; IL6 rs1800795; MMP3 rs679620). As well as replication by independent groups, large-scale genome-wide association studies are required to identify new genetic markers. Future research should also investigate the physiological mechanisms associating these polymorphisms with specific phenotypes. Further, researchers should investigate the above associations in female and non-Caucasian soccer players, as almost all published studies have recruited male participants of European ancestry. Only after robust, independently replicated genetic data have been generated, can genetic testing be considered an additional tool to potentially inform future practice in soccer.

Increased Expression of Adipokines in Patients With Frozen Shoulder

BACKGROUND

Adipokines represent a spectrum of bioactive molecules that could modulate fibroblastic and inflammatory processes. The role of adipokines in the pathogenesis of frozen shoulder (FS), a common musculoskeletal disorder characterized by chronic inflammation, remains obscure.

PURPOSE

To evaluate whether adipokines contribute to the pathogenic mechanisms of FS and to evaluate any potential correlation of adipokines with patients' symptoms.

STUDY DESIGN

Controlled laboratory study.

METHODS

Shoulder capsule specimens were obtained from 10 patients with FS and 10 patients with shoulder instability (control group). The specimens were dyed using hematoxylin and eosin and immunohistochemically assessed with antibodies targeting adipokines, collagen I, collagen III, and tumor necrosis factor α. Immunoreactivity was graded from "no" to "strong" in a blinded manner. Reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) analysis was conducted. Before the surgery, patient-reported frequency of pain, severity of pain, stiffness, and shoulder range of motion were documented.

RESULTS

In comparison with the control group, patients with FS had significantly greater pain frequency, pain severity, and stiffness and more limited shoulder range of motion (P < .001). Hematoxylin and eosin- and Masson trichrome-stained samples from the FS group displayed hypercellularity and increased collagen fibers. Immunohistochemistry and RT-qPCR analyses indicated that expression of adipokines was significantly increased in FS capsules compared with the control group. The expression of collagen I, collagen III, and tumor necrosis factor α was also increased in FS capsules. No significant correlation was noted between adipokine expression and patient-reported outcomes in the control group, whereas in patients with FS, adiponectin expression was correlated with pain frequency (r = 0.78; P = .01) and stiffness (r = 0.73; P = .02). Visfatin was also correlated with pain frequency (r = 0.70; P = .02).

CONCLUSION/CLINICAL RELEVANCE

This study indicated a potential role for adipokines in the pathogenesis of FS and demonstrated a correlation between adipokine expression and patients' pain and stiffness.

Platelet-rich plasma in the pathologic processes of tendinopathy: a review of basic science studies

Tendinopathy is a medical condition that includes a spectrum of inflammatory and degenerative tendon changes caused by traumatic or overuse injuries. The pathological mechanism of tendinopathy has not been well defined, and no ideal treatment is currently available. Platelet-rich plasma (PRP) is an autologous whole blood derivative containing a variety of cytokines and other protein components. Various basic studies have found that PRP has the therapeutic potential to promote cell proliferation and differentiation, regulate angiogenesis, increase extracellular matrix synthesis, and modulate inflammation in degenerative tendons. Therefore, PRP has been widely used as a promising therapeutic agent for tendinopathy. However, controversies exist over the optimal treatment regimen and efficacy of PRP for tendinopathy. This review focuses on the specific molecular and cellular mechanisms by which PRP manipulates tendon healing to better understand how PRP affects tendinopathy and explore the reason for the differences in clinical trial outcomes. This article has also pointed out the future direction of basic research and clinical application of PRP in the treatment of tendinopathy, which will play a guiding role in the design of PRP treatment protocols for tendinopathy.

Association of Severe Histological Degeneration of the Torn Supraspinatus Tendon and Retear After Arthroscopic Repair of Full-Thickness Rotator Cuff Tears Using the Suture Bridge Technique

BACKGROUND

Previous studies have demonstrated several prognostic factors for retear after arthroscopic rotator cuff repair (ARCR). However, studies that histologically evaluate the quality of the torn rotator cuff (RC) tendon and its association with postoperative outcomes are limited.

PURPOSE

To investigate factors associated with retear after ARCR using the suture bridge (SB) technique, including the degree of histological degeneration of the RC tendon edge.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

The authors retrospectively evaluated 187 patients who underwent ARCR for full-thickness tears using the SB technique; intraoperative biopsy samples were taken to assess the degree of histological degeneration using the Bonar score. The cohort was divided into healed (n = 165) and retear (n = 22) groups according to magnetic resonance imaging results obtained ≥6 months postoperatively. The evaluation included preoperative patient data (age, sex, symptom duration, trauma history, history of heavy manual work, smoking habit, hypertension, diabetes mellitus, and hyperlipidemia) and radiological data (Hamada classification, Patte classification, Goutallier classification, and global fatty degeneration index [GFDI]). Additionally, intraoperative data (anteroposterior tear size, Lafosse classification for concomitant subscapularis tendon tear, and long head of biceps injury) and preoperative and postoperative clinical findings (active range of motion, University of California, Los Angeles [UCLA], score) were evaluated.

RESULTS

The retear rate was 11.8%. The retear group had a higher percentage of men (P = .031), higher Bonar score (P < .001), higher mean GFDI value (P = .002), higher rate of tear retraction degree (P = .010), and larger anteroposterior tear size (P = .020) than the healed group. The retear group had lower postoperative internal rotation (P = .031) and lower UCLA score (P < .001). Multivariate logistic regression analysis with a stepwise variable selection revealed anteroposterior tear size (odds ratio [OR], 2.4; 95% CI, 1.3-4.5; P = .004) and Bonar score (OR, 1.7; 95% CI, 1.3-2.4; P < .001) as independent predictors for a retear.

CONCLUSION

The results indicate that end-stage severe tendon degeneration might affect retear. Therefore, further investigation on the progression mechanisms of tendon degeneration and development of methods to assess degenerative tissue might improve clinical outcomes after ARCR.

Effect of CCR2 Knockout on Tendon Biomechanical Properties in a Mouse Model of Delayed Rotator Cuff Repair

BACKGROUND

The high incidence of incomplete or failed healing after rotator cuff repair (RCR) has led to an increased focus on the biologic factors that affect tendon-to-bone healing. Inflammation plays a critical role in the initial tendon-healing response. C-C chemokine receptor type 2 (CCR2) is a chemokine receptor linked to the recruitment of monocytes in early inflammatory stages and is associated with an increase in pro-inflammatory macrophages. The purpose of this study was to evaluate the role of CCR2 in tendon healing following RCR in C57BL/6J wildtype (WT) and CCR2-/- knockout (CCR2KO) mice in a delayed RCR model.

METHODS

Fifty-two 12-week-old, male mice were allocated to 2 groups (WT and CCR2KO). All mice underwent unilateral supraspinatus tendon (SST) detachment at the initial surgical procedure, followed by a delayed repair 2 weeks later. The primary outcome measure was biomechanical testing. Secondary measures included histology, gene expression analysis, flow cytometry, and gait analysis.

RESULTS

The mean load-to-failure was 1.64 ± 0.41 N in the WT group and 2.50 ± 0.42 N in the CCR2KO group (p = 0.030). The mean stiffness was 1.43 ± 0.66 N/mm in the WT group and 3.00 ± 0.95 N/mm in the CCR2KO group (p = 0.008). Transcriptional profiling demonstrated 7 differentially expressed genes (DEGs) when comparing the CCR2KO and WT groups (p < 0.05) and significant differences in Type-I and Type-II interferon pathway scores (p < 0.01). Flow cytometry demonstrated significant differences between groups for the percentage of macrophages present (8.1% for the WT group compared with 5.8% for the CCR2KO group; p = 0.035). Gait analysis demonstrated no significant differences between groups.

CONCLUSIONS

CCR2KO may potentially improve tendon biomechanical properties by decreasing macrophage infiltration and/or by suppressing inflammatory mediator pathways in the setting of delayed RCR.

CLINICAL RELEVANCE

CCR2 may be a promising target for novel therapeutics that aim to decrease failure rates following RCR.

A combination of omega-3 and exercise reduces experimental Achilles tendinopathy induced with a type-1 collagenase in rats

This study aimed to evaluate the effectiveness of omega-3 supplementation with exercise in a collagenase-induced Achilles tendinopathy (AT) rat model. Experimental groups (healthy control (HC), AT, exercise (Ex), omega-3 (W), and Ex+W) were randomly allocated. After a week of adaptation, oral omega-3 was initiated for 8 weeks (5 days/week). The exercise groups performed treadmill running for 30 min/day (5 days/week, 20 m/min, 8 weeks) following one week of adaptation (10 m/min, 15 min/day). Matrix metalloproteinase-13 (MMP-13), interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and total antioxidant-oxidant status (TAS) levels were determined in serum samples. Tendon samples were obtained for biomechanical, histopathological, and immunohistochemical assessments. Ultimate tensile force, yield force, stiffness values, collagen type-I alpha 1 expression, and serum TAS significantly decreased (P < 0.05) in AT vs. HC. These values and expression significantly increased in the Ex+W group vs. AT. Serum MMP-13, IL-1β, and TNF-α levels decreased in all treatment groups vs. AT. The most significant decrease was found in the Ex+W group (P < 0.01). Histopathologically, the improvement in degeneration was statistically significant in the Ex+W group (P < 0.05). Immunohistochemically, MMP-13, IL-1β, TNF-α, and nitric oxide synthase-2 expression was decreased in all treatment groups vs. AT. In conclusion, omega-3 and exercise might be recommended in AT patients.

Regulating Macrophages through Immunomodulatory Biomaterials Is a Promising Strategy for Promoting Tendon-Bone Healing

The tendon-to-bone interface is a special structure connecting the tendon and bone and is crucial for mechanical load transfer between dissimilar tissues. After an injury, fibrous scar tissues replace the native tendon-to-bone interface, creating a weak spot that needs to endure extra loading, significantly decreasing the mechanical properties of the motor system. Macrophages play a critical role in tendon-bone healing and can be divided into various phenotypes, according to their inducing stimuli and function. During the early stages of tendon-bone healing, M1 macrophages are predominant, while during the later stages, M2 macrophages replace the M1 macrophages. The two macrophage phenotypes play a significant, yet distinct, role in tendon-bone healing. Growing evidence shows that regulating the macrophage phenotypes is able to promote tendon-bone healing. This review aims to summarize the impact of different macrophages on tendon-bone healing and the current immunomodulatory biomaterials for regulating macrophages, which are used to promote tendon-bone healing. Although macrophages are a promising target for tendon-bone healing, the challenges and limitations of macrophages in tendon-bone healing research are discussed, along with directions for further research.

Structural and pathological changes in the enthesis are influenced by the muscle contraction type during exercise

Mechanical stress is involved in the onset of sports-related enthesopathy. Although the amount of exercise undertaken is a recognized problem during disease onset, changes in muscle contraction type are also involved in the increase in mechanical stress during exercise. This study aimed to clarify the effects of increased mechanical stress associated with muscle contraction type and amount of exercise on enthesis. Twenty mice underwent treadmill exercise, and the muscle contraction type and overall load during exercise were adjusted by varying the angle and speed conditions. Histological analysis was used to the cross-sectional area of the muscle; area of the enthesis fibrocartilage (FC), and expression of inflammation-, degeneration-, and calcification-related factors in the FC area. In addition, the volume and structure of the bone and FC area were examined using microcomputer imaging. Molecular biological analysis was conducted to compare relative expression levels of inflammation and cytokine-related factors in tendons. The Overuse group, which increased the amount of exercise, showed no significant differences in parameters compared to the sedentary mice (Control group). The mice subjected to slow-speed downhill running (Misuse group) showed pathological changes compared to the Control and Overuse groups, despite the small amount of exercise. Thus, the enthesis FC area may be altered by local mechanical stress that would be increased by eccentric muscle contraction rather than by mechanical stress that increases with the overall amount of exercise. Clinical Significance: The muscle contraction type might be more involved in the onset of sports-related enthesopathy rather than the amount of exercise.

The Usefulness of Serological Inflammatory Markers in Patients with Rotator Cuff Disease—A Systematic Review

Background and Objectives: Rotator cuff disease (RCD) is a prominent musculoskeletal pain condition that spans a variety of pathologies. The etiology and precise diagnostic criteria of this condition remain unclear. The current practice of investigating the biochemical status of RCD is by conducting biopsy studies but their invasiveness is a major limitation. Recent biochemical studies on RCD demonstrate the potential application of serological tests for evaluating the disease which may benefit future clinical applications and research. This systematic review is to summarize the results of available studies on serological biochemical investigations in patients with RCD. Methods: An electronic search on databases PubMed and Virtual Health Library was conducted from inception to 1 September 2021. The inclusion criteria were case-control, cross-sectional, and cohort studies with serological biochemical investigations on humans with RCD. Methodological quality was assessed using the Study Quality Assessment Tool for Observational Cohort and Cross-sectional studies from the National Heart, Lung, and Blood Institute. Results: A total of 6008 records were found in the databases; of these, 163 full-text studies were checked for inclusion and exclusion criteria. Nine eligible studies involving 984 subjects with RCD emerged from this systematic review. The quality of the studies found ranged from poor to moderate. In summarizing all the studies, several fatty acids, nonprotein nitrogen, interleukin-1 β, interleukin-8, and vascular endothelial growth factor were found to be significantly higher in blood samples of patients with RCD than with control group patients, while Omega-3 Intex, vitamin B12, vitamin D, phosphorus, interleukin-10, and angiogenin were observed to be significantly lower. Conclusions: This is the first systematic review to summarize current serological studies in patients with RCD. Results of the studies reflect several systemic physiological changes in patients with RCD, which may prove helpful to better understand the complex pathology of RCD. In addition, the results also indicate the possibility of using serological tests in order to evaluate RCD; however, further longitudinal studies are required.

Evaluation of Therapeutic Effects of Quercetin Against Achilles Tendinopathy in Rats via Oxidative Stress, Inflammation, Apoptosis, Autophagy, and Metalloproteinases

BACKGROUND

Achilles tendinopathy, seen in athletes and manual labor workers, is an inflammatory condition characterized by chronic tendon pain. Owing to the toxicity that develops in various organs attributed to the use of anti-inflammatory drugs, there is a need for new therapeutic agents.

PURPOSE

In the present study, the effects of quercetin (Que), the one that attracted the most attention of researchers studying this group of flavonoids, were investigated against collagenase-induced tendinopathy.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 35 Sprague-Dawley rats were used in the study. Tendinopathy was created by injecting a single dose of collagenase (10 μL; 10 mg/mL) into the tendons of rats. Thirty minutes after the injection, Que was administered at doses of 25 or 50 mg/kg. Que administration was carried out for 7 days. Animals underwent a motility test at the end of the study. In addition, markers of oxidative stress, inflammation, apoptosis, and autophagy, as well as the expression levels of matrix metalloproteinases (MMPs 2, 3, 9, and 13), ICAM-1, and STAT3, were measured in tendon tissues with biochemical, molecular, and Western blot techniques.

RESULTS

The results showed that oxidative stress, inflammation, apoptosis, and autophagy were triggered by the injection of collagenase. In addition, MMPs, ICAM-1, and STAT3 were activated to participate in the development of tendinopathy. Que was found to reduce ICAM-1 levels in tendon tissue. Moreover, Que showed antioxidant, anti-inflammatory, antiapoptotic, and antiautophagic effects on tendons against tendinopathy. More important, Que suppressed the expression of MMPs in the tendon tissues.

CONCLUSION

Que has protective properties against collagenase-induced tendon damage in rats.

CLINICAL RELEVANCE

We believe that with further study, Que may be shown to be an alternative treatment option for athletes or others who experience tendon injuries.

Inflammatory mechanisms linking obesity and tendinopathy

Chronic tendinopathy is a debilitating tendon disorder with disappointing treatment outcomes. This review focuses on the potential roles of chronic low-grade inflammation in promoting tendinopathy in obesity. A systematic literature search was performed to identify all clinical studies supporting the actions of obesity-associated inflammatory mediators in the development of tendinopathy. The mechanisms of obesity-induced chronic inflammation in adipose tissue are firstly reviewed. Common inflammatory mediators potentially linking obesity and the development of tendinopathy, and their association with mechanical overuse, are discussed, along with pre-clinical evidences and a systematic literature search on clinical studies. The potential contribution of local adipose tissues in the promotion of inflammation, pain and tendon degeneration is then discussed. The future research directions are proposed.

Translational potential statement

Better understanding of the roles of obesity-associated inflammatory mediators on tendons will clarify the pathophysiological drivers of tendinopathy in patients with obesity and identify possible treatment targets. Further studies on the mechanisms of obesity-induced chronic inflammation on tendon are a promising direction for the treatment of tendinopathy.

No differences in histopathological degenerative changes found in acute, trauma-related rotator cuff tears compared with chronic, nontraumatic tears

PURPOSE

Acute trauma-related rotator cuff tears are believed to have better healing potential than chronic tears due to less degenerative changes of the tendons. However, the histopathological condition of tendons from trauma-related tears is not well investigated. The purpose of this study was to explore specific histopathological features in tendons from acute trauma-related full-thickness rotator cuff tears and to compare them to findings in tendons from nontraumatic, chronic tears.

METHODS

In a prospective cohort study, 62 previously asymptomatic patients [14 women, median age 61 years (range 42-75)] with trauma-related full-thickness rotator cuff tears were consecutively included. Arthroscopic repair was performed within 30 (median, IQR 25-37) days after the injury. During surgery, tissue biopsies were harvested from the supraspinatus tendons in 53 (86%) of the patients. In addition, similar biopsies were harvested from 10 patients undergoing surgery for chronic tears without history of trauma. All tissue samples were examined by a well-experienced pathologist under light microscope. Tendon degeneration was determined using the Bonar score whereas immunostaining was used for proliferation (Ki67), inflammation (CD45), apoptosis (p53) and haemosiderin staining to study traces of bleeding.

RESULTS

The median (IQR) Bonar score for the acute trauma-related biopsies was 10.5 (7.5-14.5) compared to 11 (5-12.8) for the control group with no statistically significant difference between the groups. No statistically significant between-group difference was found for the inflammatory index whereas tendons from patients with trauma-related full-thickness rotator cuff tears had statistically significantly higher apoptosis [3.1 (0.5-8.9) vs. 0.1 (0-1.5), p = 0.003] and proliferation [4.0 (1.8-6.9) vs. 0.4 (0-2.0), p = 0.001) indices than those undergoing surgery for chronic tears. Positive haemosiderin staining was found in 34% of tissue samples from patients with trauma-related tears compared to 10% in the control group (n.s).

CONCLUSION

This study suggests that there is no difference with regard to degenerative changes between supraspinatus tendons harvested from patients with acute, trauma-related rotator cuff tears and patients with nontraumatic, chronic tears.

LEVEL OF EVIDENCE

II.

Treatment With Glycogen Synthase Kinase 3β Inhibitor Decreases Apoptotic and Autophagic Reactions in Rat Rotator Cuff Tears

Background:

Apoptosis and autophagy are known to be correlated with the extent of damage in torn rotator cuffs, and there is no biological evidence for self-recovery or healing of the rotator cuff tear.

Purpose:

To establish in a rat model of partial- and full-thickness rotator cuff tears how a glycogen synthase kinase 3β (GSK-3β) inhibitor affects the expression of apoptotic and autophagic markers.

Study Design:

Controlled laboratory study.

Methods:

Twelve-week-old Sprague Dawley rats were divided into 3 groups (n = 16 per group). Group 1 acted as the control, with no treatment; group 2 received partial-thickness (right side) and full-thickness (left side) rotator cuff tears only; and group 3 received the same rotator cuff injuries, with GSK-3β inhibitor injected afterward. The tendons from each group were harvested 42 days after surgery. Evaluation of gene expression, immunohistochemistry, and TUNEL staining (terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling) were performed for the following markers: caspases 3, 8, and 9 as well as Bcl-2 (B-cell lymphoma 2); BAX (Bcl-2-associated X protein); beclin 1; p53; and GSK-3β; which represented apoptotic and autophagic reactions. Statistical analysis was performed using 1-way analysis of variance.

Results:

In the group 2 rats with partial- and full-thickness tears, there were significant increases in the mRNA levels (fold changes) of all 8 markers as compared with group 1 (control). All these increased markers showed significant downregulation by the GSK-3β inhibitor in partial-thickness tears. However, the response to the GSK-3β inhibitor in full-thickness tears was not as prominent as in partial-thickness tears. The number of TUNEL-positive cells in group 2 (partial, 35.08% ± 1.625% [mean ± SE]; full, 46.92% ± 1.319%) was significantly higher than in group 1 (18.02% ± 1.036%; P < .01) and group 3 (partial, 28.04% ± 2.607% [P < .01]; full, 38.97% ± 2.772% [P < .01]), and immunohistochemistry revealed increased expression of all the markers in group 2 as compared with control.

Conclusion:

The apoptotic and autophagic activity induced in a rat model of an acute rotator cuff tear was downregulated after treatment with a GSK-3β inhibitor, particularly with partial-thickness rotator cuff tears.

Clinical Relevance:

A GSK-3β inhibitor may be able to modulate deterioration in a torn rotator cuff.

Tendon healing is adversely affected by low-grade inflammation

BACKGROUND

Tendinopathy is common, presents with pain and activity limitation, and is associated with a high risk of recurrence of the injury. Tendinopathy usually occurs as a results of a disrupted healing response to a primary injury where cellular and molecular pathways lead to low grade chronic inflammation.

MAIN FINDINGS

There has been a renewed interest in investigating the role of Inflammation in the pathogenesis of tendinopathy, in particular during the initial phases of the condition where it may not be clinically evident. Understanding the early and late stages of tendon injury pathogenesis would help develop new and effective treatments addressed at targeting the inflammatory pathways.

CONCLUSION

This review outlines the role of low-grade Inflammation in the pathogenesis of tendinopathy, stressing the role of proinflammatory cytokines, proteolytic enzymes and growth factors, and explores how Inflammation exerts a negative influence on the process of tendon healing.

CTRP3 exacerbates tendinopathy by dysregulating tendon stem cell differentiation and altering extracellular matrix composition

Tendinopathy, the most common disorder affecting tendons, is characterized by chronic disorganization of the tendon matrix, which leads to tendon tear and rupture. The goal was to identify a rational molecular target whose blockade can serve as a potential therapeutic intervention for tendinopathy. We identified C1q/TNF-related protein-3 (CTRP3) as a markedly up-regulated cytokine in human and rodent tendinopathy. Overexpression of CTRP3 enhanced the progression of tendinopathy by accumulating cartilaginous proteoglycans and degenerating collagenous fibers in the mouse tendon, whereas CTRP3 knockdown suppressed the tendinopathy pathogenesis. Functional blockade of CTRP3 using a neutralizing antibody ameliorated overuse-induced tendinopathy of the Achilles and rotator cuff tendons. Mechanistically, CTRP3 elicited a transcriptomic pattern that stimulates abnormal differentiation of tendon stem/progenitor cells and ectopic chondrification as an effect linked to activation of Akt signaling. Collectively, we reveal an essential role for CTRP3 in tendinopathy and propose a potential therapeutic strategy for the treatment of tendinopathy.

Tendinopathy and tendon material response to load: What we can learn from small animal studies

Tendinopathy is a debilitating disease that causes as much as 30% of all musculoskeletal consultations. Existing treatments for tendinopathy have variable efficacy, possibly due to incomplete characterization of the underlying pathophysiology. Mechanical load can have both beneficial and detrimental effects on tendon, as the overall tendon response depends on the degree, frequency, timing, and magnitude of the load. The clinical continuum model of tendinopathy offers insight into the late stages of tendinopathy, but it does not capture the subclinical tendinopathic changes that begin before pain or loss of function. Small animal models that use high tendon loading to mimic human tendinopathy may be able to fill this knowledge gap. The goal of this review is to summarize the insights from in-vivo animal studies of mechanically-induced tendinopathy and higher loading regimens into the mechanical, microstructural, and biological features that help characterize the continuum between normal tendon and tendinopathy. STATEMENT OF SIGNIFICANCE: This review summarizes the insights gained from in-vivo animal studies of mechanically-induced tendinopathy by evaluating the effect high loading regimens have on the mechanical, structural, and biological features of tendinopathy. A better understanding of the interplay between these realms could lead to improved patient management, especially in the presence of painful tendon.

Human Tendon Stem/Progenitor Cell Features and Functionality Are Highly Influenced by in vitro Culture Conditions

Our understanding of tendon biology continues to evolve, thus leading to opportunities for developing novel, evidence-based effective therapies for the treatment of tendon disorders. Implementing the knowledge of tendon stem/progenitor cells (TSPCs) and assessing their potential in enhancing tendon repair could fill an important gap in this regard. We described different molecular and phenotypic profiles of TSPCs modulated by culture density, as well as their multipotency and secretory activities. Moreover, in the same experimental setting, we evaluated for different responses to inflammatory stimuli mediated by TNFα and IFNγ. We also preliminarily investigated their immunomodulatory activity and their role in regulating degradation of substance P. Our findings indicated that TSPCs cultured at low density (LD) exhibited cobblestone morphology and a reduced propensity to differentiate. A distinctive immunophenotypic profile was also observed with high secretory and promising immunomodulatory responses when primed with TNFα and IFNγ. In contrast, TSPCs cultured at high density (HD) showed a more elongated fibroblast-like morphology, a greater adipogenic differentiation potential, and a higher expression of tendon-related genes with respect to LD. Finally, HD TSPCs showed immunomodulatory potential when primed with TNFα and IFNγ, which was slightly lower than that shown by LD. A shift from low to high culture density during TSPC expansion demonstrated intermediate features confirming the cellular adaptability of TSPCs. Taken together, these experiments allowed us to identify relevant differences in TSPCs based on culture conditions. This ability of TSPCs to acquire distinguished morphology, phenotype, gene expression profile, and functional response advances our current understanding of tendons at a cellular level and suggests responsivity to cues in their in situ microenvironment.

Effect of Hypertonic Dextrose Injection on Pain and Shoulder Disability in Patients with Chronic Supraspinatus Tendinosis: A Randomized Double-Blind Controlled Study

OBJECTIVES

To investigate the effect of hypertonic dextrose injection on pain and disability in patients with chronic supraspinatus tendinosis. The secondary aim was to evaluate its effect on the tendon range of motion (ROM) and morphology.

DESIGN

Randomized double-blind placebo-controlled trial.

SETTING

Outpatient clinic.

PARTICIPANTS

Individuals (N=57) with symptomatic chronic supraspinatus tendinosis.

INTERVENTIONS

Participants were randomly administered ultrasound-guided injections of 20% hypertonic dextrose (study group, n=29) or 5% normal saline (control group, n=28).

MAIN OUTCOME MEASURES

The primary outcome measure was visual analog scale (VAS) scores for pain and Shoulder Pain and Disability Index (SPADI) scores. Secondary outcomes included the ROM and ultrasound examination findings of the supraspinatus tendon at baseline and at 2, 6, and 12 weeks postintervention.

RESULTS

The study group exhibited significant improvements in the VAS (mean difference [MD], -2.1; 95% confidence interval [CI], -2.7 to -1.4; P<.001) and SPADI (MD, -11.6; 95% CI, -16.5 to -6.7; P<.001) scores compared with baseline scores at week 2. However, the effect was not sustained to week 6. Flexion ROM increased at weeks 2 (MD, 14.1; 95% CI, 5.7-22.5; P<.001) and 6 (MD, 8.9; 95% CI, 2.4-15.4; P=.003) compared with baseline. The thickness of the supraspinatus tendon improved at weeks 6 (MD, .50; 95% CI, .26-.74; P<.001) and 12 (MD, .61; 95% CI, .37-.84; P<.001) compared with baseline. The ratio of histograms also improved at weeks 6 (MD, .19; 95% CI, .06-.32; P=.002) and 12 (MD, .26; 95% CI, .10-.41; P<.001) compared with baseline.

CONCLUSION

Hypertonic dextrose injection could provide short-term pain and disability relief in patients with chronic supraspinatus tendinosis. Ultrasound imaging at week 6 revealed changed tendon morphology.

Tendon-Derived Progenitor Cells With Multilineage Potential Are Present Within Human Patellar Tendon

Background:

Progenitor cells serve as a promising source of regenerative potential in a variety of tissue types yet remain underutilized in tendinopathy. Tendon-derived progenitor cells (TDPCs) have previously been isolated from hamstring tendon but only as part of a concomitant medical procedure. Determining the presence of TDPCs in patellar tendon may facilitate clinical utilization of these cells because of the relative accessibility of this location for tissue harvest.

Purpose:

To characterize TDPCs in human patellar tendon samples.

Study Design:

Descriptive laboratory study.

Methods:

Human patellar tendon samples were obtained during elective knee surgery. TDPCs were isolated and seeded at an optimal low cell density and subcultured to confluence for up to 2 passages. Flow cytometry was used to analyze for the expression of CD90+, CD105+, CD44+, and CD31–, CD34–, and CD45– markers. The multilineage differentiation potential of TDPCs was tested in vitro via adipogenic, osteogenic, and chondrogenic culture with subsequent cytochemical staining for Oil Red O, Alizarin Red, and Alcian Blue, respectively. Enzyme-linked immunosorbent assay was used to quantify the amount of adiponectin, alkaline phosphatase, and SRY-box transcription factor 9 secreted into cell culture supernatant for further confirmation of lineage differentiation. Results were analyzed statistically using the 2-tailed Student t test.

Results:

TDPCs demonstrated near-uniform expression of CD90, CD105, and CD44 with minimal expression of CD34, CD31, and CD45. Adipogenic, osteogenic, and chondrogenic differentiation of TDPCs was confirmed using qualitative analysis. The expression of adiponectin, alkaline phosphatase, and SRY-box transcription factor 9 were significantly increased in differentiated cells versus undifferentiated TDPCs (P < .05).

Conclusion:

TDPCs can be successfully isolated from human patellar tendon samples, and they exhibit characteristics of multipotent progenitor cells.

Clinical Relevance:

These data demonstrate the promise of patellar tendon tissue as a source of progenitor cells for use in biologic therapies for the treatment of tendinopathy.

Ginsenoside Rg1 enhances the healing of injured tendon in achilles tendinitis through the activation of IGF1R signaling mediated by oestrogen receptor

Background

During the pathogenesis of tendinopathy, the chronic inflammation caused by the injury and apoptosis leads to the generation of scars. Ginsenoside Rg1 (Rg1) is extracted from ginseng and has anti-inflammatory effects. Rg1 is a unique phytoestrogen that can activate the estrogen response element. This research aimed to explore whether Rg1 can function in the process of tendon repair through the estrogen receptor.

Methods

In this research, the effects of Rg1 were evaluated in tenocytes and in a rat model of Achilles tendinitis (AT). Protein levels were shown by western blotting. qRT-PCR was employed for evaluating mRNA levels. Cell proliferation was evaluated through EdU assay and cell migration was evaluated by transwell assay and scratch test assay.

Results

Rg1 up-regulated the expression of matrix-related factors and function of tendon in AT rat model. Rg1 reduced early inflammatory response and apoptosis in the tendon tissue of AT rat model. Rg1 promoted tenocyte migration and proliferation. The effects of Rg1 on tenocytes were inhibited by ICI182780. Rg1 activates the insulin-like growth factor-I receptor (IGF1R) and MAPK signaling pathway.

Conclusion

Rg1 promotes injured tendon healing in AT rat model through IGF1R and MAPK signaling pathway activation.

Association of TNF-α -308G > A polymorphism with susceptibility to tendinopathy in athletes: a case-control study

BACKGROUND

High levels of the tumor necrosis factor alpha (TNF-α) induce apoptosis and pro-inflammatory effects for primary degeneration of tendon and development of tendinopathy. The aim of this study was to investigate the association between the TNF-α polymorphisms and tendinopathy in athletes.

METHODS

Two hundred and seventy athletes (135 tendinopathy cases and 135 controls) were included and genotyped (TNF-α -1031T > C; -857 C > T; -308G > A) using TaqMan validated assays. The association of the polymorphisms with tendinopathy was evaluated by a multivariate logistic regression model, using odds ratios (OR) and 95 % confidence intervals (CI).

RESULTS

The variant allele - 308 A was significantly associated with patellar (OR: 1.9; 95 % CI: 1.01-3.6) or Achilles tendinopathies (OR: 2.7; 95 % CI: 1.1-6.7). No significant differences were found in allele or genotype distributions of the - 1031T > C and - 857 C > T polymorphisms between cases and controls. TNF-α TCA haplotype was associated with increased tendinopathies risk, either considering all cases (OR: 2.6, 95 % CI: 1.3-5.3), patellar (OR: 3.3, 95 % CI: 1.5-7.3), rotator cuff (OR: 3.1, 95 % CI: 1.4-7.2) or Achilles tendinopathies (OR: 3.8, 95 % CI: 1.1-12.7).

CONCLUSIONS

These results suggest that the TNF-α polymorphisms could influence the susceptibility to developing tendinopathy among athletes. Knowledge of the TNF-α polymorphisms associated to tendinopathy in athletes can further understanding of the inflammatory role in the early stages of the disease and contribute for sports injury surveillance programmes, in which athletes with TNF-α TCA haplotype could be early subjected to cryotherapy after training and competition to avoid tendinopathy development.

Low serum vitamin B12 levels are associated with degenerative rotator cuff tear

BACKGROUND

Vitamin B₁₂ (Vit B₁₂) deficiency results in elevated homocysteine levels and interference with collagen cross-linking, which may affect tendon integrity. The purpose of this study was to investigate whether serum Vit B₁₂ levels were correlated with degenerative rotator cuff (RC) tear.

METHODS

Eighty-seven consecutive patients with or without degenerative RC tear were enrolled as study participants. Possible risk factors (age, sex, medical history, bone mineral density, and serum chemistries including glucose, magnesium, calcium, phosphorus, zinc, homocysteine, Vitamin D, Vit B₁₂, homocysteine, and folate) were assessed. Significant variables were selected based on the results of univariate analyses, and a logistic regression model (backward elimination) was constructed to predict the presence of degenerative RC tear.

RESULTS

In the univariate analysis, the group of patients with degenerative RC tear had a mean concentration of 528.4 pg/mL Vit B₁₂, which was significantly lower than the healthy control group (627.1 pg/mL). Logistic regression analysis using Vit B₁₂ as an independent variable revealed that Vit B₁₂ concentrations were significantly correlated with degenerative RC tear (p = 0.044). However, Vit B₁₂ levels were not associated with tear size.

CONCLUSION

Low serum levels of Vit B₁₂ were independently related to degenerative RC tear. Further investigations are warranted to determine if Vit B₁₂ supplementation can decrease the risk of this condition.

Comparison of the Effectiveness of Ultrasound-Guided Prolotherapy in Supraspinatus Tendon with Ultrasound-Guided Corticosteroid Injection of Subacromial Subdeltoid Bursa in Rotator Cuff-Related Shoulder Pain: A Clinical Trial Study

Background

Shoulder pain is the third most common type of musculoskeletal disorder and rotator cuff (RC) tendinopathy is the most frequent diagnosis. Ultrasound is the most preferable guidance tool for diagnostic and interventional purposes. The aim of this study is to compare the effectiveness of the prolotherapy injection with corticosteroid injection in patients with RC dysfunction.

Materials and Methods

Thirty to sixty-five-year-old patients with chronic RC disease were divided into two groups. Ultrasound-guided dextrose prolotherapy of supraspinatus tendon was done for one group and ultrasound-guided corticosteroid injection in the subacromial bursa was done for the other groups. Visual analog scale (VAS) and Shoulder Pain and Disability Index (SPADI) were evaluated for both groups at baseline, 3 and 12 weeks after injections.

Results

Thirty-three patients were included in the result. Both the groups showed significant improvement in VAS and SPADI scores in 3 and 12 weeks after injections compared with preinjection times with no difference between two groups neither in 3 weeks nor in 12 weeks after injections.

Conclusion

Both ultrasound-guided dextrose prolotherapy and CS injections are effective in the management of RC-related shoulder pain in both short-term and long-term with neither being superior to the other. Therefore, prolotherapy may be a safe alternative therapy instead of corticosteroid injection due to lack of its side effects.

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

OBJECTIVES

Increasing 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 tendon stromal cells or tenocytes to define their functional contribution to tissue remodelling and inflammation amplification and hence disease perpetuation.

METHODS

T cells were quantified and characterised in healthy and tendinopathic tissues by flow cytometry (FACS), imaging mass cytometry (IMC) and single cell RNA-seq. Tenocyte activation induced by conditioned media from primary damaged tendon or interleukin-1β was evaluated by qPCR. The role of tenocytes in regulating T cell migration was interrogated in a standard transwell membrane system. T cell activation (cell surface markers by FACS and cytokine release by ELISA) and changes in gene expression in tenocytes (qPCR) were assessed in cocultures of T cells and explanted tenocytes.

RESULTS

Significant quantitative differences were observed in healthy compared with tendinopathic tissues. IMC showed T cells in close proximity to tenocytes, suggesting tenocyte-T cell interactions. On activation, tenocytes upregulated inflammatory cytokines, chemokines and adhesion molecules implicated in T cell recruitment and activation. Conditioned media from activated tenocytes induced T cell migration and coculture of tenocytes with T cells resulted in reciprocal activation of T cells. In turn, these activated T cells upregulated production of inflammatory mediators in tenocytes, while increasing the pathogenic collagen 3/collagen 1 ratio.

CONCLUSIONS

Interaction between T cells and tenocytes induces the expression of inflammatory cytokines/chemokines in tenocytes, alters collagen composition favouring collagen 3 and self-amplifies T cell activation via an auto-regulatory feedback loop. Selectively targeting this adaptive/stromal interface may provide novel translational strategies in the management of human tendon disorders.

Selected Clinical Features Fail to Predict Inflammatory Gene Expressions for TNF-α, TNFR1, NSMAF, Casp3 and IL-8 in Tendons of Patients with Rotator Cuff Tendinopathy

The pathophysiology of rotator cuff tendinopathy is not fully understood, particularly in terms of the local inflammatory process. This study aimed to investigate the expression of selected molecules in the tumour necrosis factor (TNF)-α transduction pathway, including TNF-α, TNF receptor 1 (TNFR1), neutral sphingomyelinase activation associated factor (NSMAF), caspase 3 (Casp3), and interleukin (IL)-8, in patients with rotator cuff tendinopathy that had undergone surgical treatment. We included 44 participants that underwent arthroscopy, due to rotator cuff tendinopathy. Samples from the injured tendon were collected during arthroscopy, and RT-PCR was performed to determine gene expression. Pearson correlation analyses or U-Mann–Whitney test were performed to identify associations with the following parameters: sex, age at admission, body mass index, the presence of night pain, previous treatment (nonsteroidal anti-inflammatory drugs and/or steroids), medical history of the shoulder injury, upper subluxation of the humeral head, and the number of tendons injured. RT-PCR showed that the selected pro-inflammatory factors involved in the TNF-α signalling pathway expression levels were expressed in the tendon tissues. However, the levels of expression varied from patient to patient. Variations were over 250-fold for TNF-α, about 130-fold for TNFR1, NSMAF, and Casp3, and 1000-fold for IL-8. We could not confirm that any of the clinical parameters investigated were associated with the level of gene expression in the TNF-α pathway and IL-8.

Vancomycin Wrap for Anterior Cruciate Ligament Surgery: Molecular Insights

BACKGROUND

The use of the vancomycin wrap to pretreat the hamstring graft in anterior cruciate ligament reconstruction (ACLR) has grown in popularity since it was first described in 2012 and has significantly reduced rates of postoperative infection. However, it remains unknown if this antibiotic treatment affects the molecular composition of the graft.

PURPOSE

To establish whether treatment with vancomycin at 5 mg/mL, the most commonly used concentration, alters the molecular function of the hamstring graft in ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

Surplus hamstring tendon collected after routine ACLR surgery was used for in vitro cell culture and ex vivo tissue experiments. Vancomycin was used at 5 mg/mL in RPMI or saline diluent to treat cells and tendon tissue, respectively, with diluent control conditions. Cell viability at 30, 60, and 120 minutes was assessed via colorimetric viability assay. Tendon cells treated with control and experimental conditions for 1 hour was evaluated using semiquantitative reverse transcription analysis, immunohistochemistry staining, and protein quantitation via enzyme-linked immunosorbent assay for changes in apoptotic, matrix, and inflammatory gene and protein expression.

RESULTS

Vancomycin treatment at 5 mg/mL significantly reduced tenocyte viability in vitro after 60 minutes of treatment (P < .05); however, this was not sustained at 120 minutes. Vancomycin-treated tendon tissue showed no significant increase in apoptotic gene expression, or apoptotic protein levels in tissue or supernatant, ex vivo. Vancomycin was associated with a reduction in inflammatory proteins from treated tendon supernatants (IL-6; P < .05).

CONCLUSION

Vancomycin did not significantly alter the molecular structure of the hamstring graft. Reductions in matrix protein and inflammatory cytokine release point to a potential beneficial effect of vancomycin in generating a homeostatic environment.

CLINICAL RELEVANCE

Vancomycin ACL wrap does not alter the molecular structure of the ACL hamstring graft and may improve graft integrity.

Tendinopathy

Tendinopathy describes a complex multifaceted pathology of the tendon, characterized by pain, decline in function and reduced exercise tolerance. The most common overuse tendinopathies involve the rotator cuff tendon, medial and lateral elbow epicondyles, patellar tendon, gluteal tendons and the Achilles tendon. The prominent histological and molecular features of tendinopathy include disorganization of collagen fibres, an increase in the microvasculature and sensory nerve innervation, dysregulated extracellular matrix homeostasis, increased immune cells and inflammatory mediators, and enhanced cellular apoptosis. Although diagnosis is mostly achieved based on clinical symptoms, in some cases, additional pain-provoking tests and imaging might be necessary. Management consists of different exercise and loading programmes, therapeutic modalities and surgical interventions; however, their effectiveness remains ambiguous. Future research should focus on elucidating the key functional pathways implicated in clinical disease and on improved rehabilitation protocols.

Tectorigenin Alleviates Inflammation, Apoptosis, and Ossification in Rat Tendon-Derived Stem Cells via Modulating NF-Kappa B and MAPK Pathways

Tendinopathy is a common musculoskeletal disorder that mainly affects athletes and people of older age. Tumor necrosis factor-α (TNF-α) plays an important role in initiating tendinopathy. Tectorigenin, an extract component of Belam-canda Chinesis, possesses anti-inflammatory and anti-apoptosis activity. The present study was established to investigate the role of tectorigenin against the pathogenetic effects of TNF-α on tendon-derived stem cells (TDSCs) in vivo and in vitro. The findings indicated that TNF-α is able to induce TDSC inflammation, apoptosis, and ossification, as well as activate nuclear factor-kappa B and mitogen-activated protein kinase (MAPK). Furthermore, the results confirmed that tectorigenin is able to inhibit the TNF-α-induced inflammation, apoptosis, and ossification. Tectorigenin treatment decreases activation of NF-kappa B and MAPK signaling in TDSCs. Tectorigenin ameliorates tendinopathy in the in vivo rat model. Thus, these data reveal that tectorigenin can serve as a potential treatment for tendinopathy.

Molecular and Structural Effects of Percutaneous Interventions in Chronic Achilles Tendinopathy

Achilles tendinopathy (AT) is a common problem, especially in people of working age, as well as in the elderly. Although the pathogenesis of tendinopathy is better known, therapeutic management of AT remains challenging. Various percutaneous treatments have been applied to tendon lesions: e.g., injectable treatments, platelet-rich plasma (PRP), corticosteroids, stem cells, MMP inhibitors, and anti-angiogenic agents), as well as percutaneous procedures without any injection (percutaneous soft tissue release and dry needling). In this review, we will describe and comment on data about the molecular and structural effects of these treatments obtained in vitro and in vivo and report their efficacy in clinical trials. Local treatments have some impact on neovascularization, inflammation or tissue remodeling in animal models, but evidence from clinical trials remains too weak to establish an accurate management plan, and further studies will be necessary to evaluate their value.

Role of matrix metalloproteases 1/3 gene polymorphisms in patients with rotator cuff tear

An association of Matrix Metalloproteinases-1/3 (MMP-1/3) rs1799750/rs3025058 polymorphism with increased risk of rotator cuff tear (RCT) has been reported in a Brazilian population. However, this significant association has not been confirmed in the Chinese population. Genotyping was conducted by polymerase chain reaction (PCR)-restriction fragment length polymorphism and direct sequencing. Our results demonstrated that individuals with the TT genotype had a significantly higher risk of RCT compared with those with the CC genotype. The increased risk of RCT progression was associated with the 2G allele of the rs1799750 polymorphism. No significant association was observed for genotypic and allelic frequencies of the rs3025058 polymorphism. A significant association of the MMP-1 rs1799750 polymorphism was observed with smokers, drinkers and people aged ≥60 years and non-diabetic people. Additionally, the MMP-1 rs1799750 polymorphism was associated with pre-operative stiffness in RCT patients. In conclusion, a significant correlation was identified between the MMP-1 rs1799750 polymorphism and RCT. The MMP-1 rs1799750 polymorphism might be considered as a biomarker of genetically high-risk RCT, helping to clarify the mechanism of RCT.

Gene Expression in Torn Rotator Cuff Tendons Determined by RNA Sequencing

Background:

Although the cause of rotator cuff tearing is likely multifactorial and a genetic predisposition has been proposed, the biochemical basis remains unknown.

Purpose:

To determine gene expression profiles in torn rotator cuff tendon tissue through use of RNA sequencing.

Study Design:

Controlled laboratory study.

Methods:

The supraspinatus tendon edge was biopsied in 24 patients undergoing arthroscopic rotator cuff repair for full-thickness supraspinatus rotator cuff tears. The supraspinatus tendon was also biopsied in 9 patients undergoing open reduction and internal fixation for a proximal humeral fracture (controls). Total RNA was extracted and sequenced. Differential gene expression was analyzed between the tear and control groups, and a secondary analysis was conducted between groups defined by an unbiased clustering.

Results:

Tear and control transcriptomes demonstrated significant differential expression in more than 3000 genes. The identified differential genes were highlighted in pathways involved in inflammation in control patients and extracellular matrix generation in patients with tears. Secondary analysis using unsupervised and thus unbiased hierarchical clustering revealed 2 clusters (c2 and c3). Cluster c3 contained smaller (P < .001) and less retracted (P = .018) tears (ie, tears earlier in the progression of rotator cuff disease) with increased expression of hypoxia target genes. Cluster c2 contained larger, more retracted tears (ie, tears further in the progression of rotator cuff disease) with increased expression of endothelial cell markers and chronic inflammation target genes. Tears in c2 had significantly worse healing rates compared with tears in c3 (0% vs 89%; P = .007).

Conclusion:

Smaller, less retracted tears had increased expression of hypoxia target genes and improved healing, whereas larger, more retracted tears were associated with endothelial cell markers and worse healing. Thus, hypoxia may be the inciting event for tear development, whereas with tear enlargement, a chronic, inflammatory, angiogenic process may predominate.

Clinical Relevance:

Identification of differential gene expression in rotator cuff tears may be a reliable tool to predict repair healing in the future.

Autologous microfragmented adipose tissue reduces inflammatory and catabolic markers in supraspinatus tendon cells derived from patients affected by rotator cuff tears

PURPOSE

Rotator cuff tears are common musculoskeletal disorders, and surgical repair is characterized by a high rate of re-tear. Regenerative medicine strategies, in particular mesenchymal stem cell-based therapies, have been proposed to enhance tendon healing and reduce the re-tear rate. Autologous microfragmented adipose tissue (μFAT) allows for the clinical application of cell therapies and showed the ability to improve tenocyte proliferation and viability in previous in vitro assessments. The hypothesis of this study is that μFAT paracrine action would reduce the catabolic and inflammatory marker expression in tendon cells (TCs) derived from injured supraspinatus tendon (SST).

METHODS

TCs derived from injured SST were co-cultured with autologous μFAT in transwell for 48 h. Metabolic activity, DNA content, the content of soluble mediators in the media, and the gene expression of tendon-specific, inflammatory, and catabolic markers were analyzed.

RESULTS

μFAT-treated TCs showed a reduced expression of PTGS2 and MMP-3 with respect to untreated controls. Increased IL-1Ra, VEGF, and IL-6 content were observed in the media of μFAT-treated samples, in comparison with untreated TCs.

CONCLUSION

μFAT exerted an anti-inflammatory action on supraspinatus tendon cells in vitro through paracrine action, resulting in the reduction of catabolic and inflammatory marker expression. These observations potentially support the use of μFAT as adjuvant therapy in the treatment of rotator cuff disease.

Suprascapular nerve neuropathy leads to supraspinatus tendon degeneration

BACKGROUND

Nowadays most of attention regarding rotator cuff is payed to how to reduce the failure after rotator cuff surgical repair rather than how to prevent the rotator cuff tear before surgery. The etiologies of rotator cuff tear are still unclear. As we all know, the nerve system include brain, spinal cord, sensory organs and all the neurons allover our body coordinates the homoeostasis of our body. We hypothesis that the nerve injury proximal to suprascapular nerve can leads to rotator cuff degeneration even tear.

METHODS

Thirty-six SD rats were used. A defect on the suprascapular nerve was made on the right side and a sham surgery on the nerve (expose nerve only) at the left side. The insertion of supraspinatus tendon and supraspinatus muscle were harvested for testing. Twelve rats were sacrificed for biomechanical (six rats) and histological (six rats) properties were evaluated at 3, 6, and 9 weeks after surgery, respectively.

RESULTS

Significant inferior biomechanical properties of rotator cuff were found in nerve injured side compared to the nerve intact side at 6-9 weeks. Significant muscle atrophy was found at nerve injured side from 3 to 9 weeks. The enthesis of nerve injured side showed significant excessive cell maturity, reduced cellularity, smaller metachromasia area and more type-III collagen especially at 9 weeks after surgery.

CONCLUSIONS

The neuropathy proximal to suprascapular nerve can leads to rotator cuff degeneration even tear. The nerve dysfunction maybe an important etiology for rotator cuff tear.

Advances in the development of gene therapy, noncoding RNA, and exosome-based treatments for tendinopathy

Tendinopathy is a common musculoskeletal disorder characterized by chronic low-grade inflammation and tissue degeneration. Tendons have poor innate healing ability and there is currently no cure for tendinopathy. Studies elucidating mechanisms underlying the pathogenesis of tendinopathy and mechanisms mediating the genesis of tendons during development have provided novel targets and strategies to enhance tendon healing and repair. This review summarizes the current understanding and treatments for tendinopathy. The review also highlights recent advances in gene therapy, the potential of noncoding RNAs, such as microRNAs, and exosomes, which are nanometer-sized extracellular vesicles secreted from cells, for the treatment of tendinopathy.

Enhanced tendon restoration effects of anti-inflammatory, lactoferrin-immobilized, heparin-polymeric nanoparticles in an Achilles tendinitis rat model

Gradual wear and tear can cause a local inflammatory response in tendons. The trauma and inflammatory reaction eventually impair the biomechanical properties of the tendon. In this study, we prepared lactoferrin-immobilized, heparin-anchored, poly(lactic-co-glycolic acid) nanoparticles (LF/Hep-PLGA NPs) and evaluated their in vitro anti-inflammatory effects on interleukin-1β (IL-1β)-treated tenocytes and in vivo tendon healing effects in a rat model of Achilles tendinitis. Long-term LF-deliverable NPs (LF/Hep-PLGA NPs) remarkably decreased mRNA levels of pro-inflammatory factors [cyclooxygenase-2 (COX-2), IL-1β, matrix metalloproteinase-3 (MMP-3), MMP-13, IL-6, and tumor necrosis factor-α (TNF-α)] and increased mRNA levels of anti-inflammatory cytokines (IL-4 and IL-10) in both IL-1β-treated tenocytes and the Achilles tendons of a collagenase-induced Achilles tendinitis rat model. Interestingly, anti-inflammatory LF/Hep-PLGA NPs greatly enhanced collagen content, mRNA levels of tenogenic markers [collagen type I (COL1A1), decorin (DCN), tenascin-C (TNC)], and biomechanical properties such as tendon stiffness and tensile strength. These results suggest that anti-inflammatory LF/Hep-PLGA NPs are effective at restoring tendons in Achilles tendinitis.

Alda-1, an activator of ALDH2, ameliorates Achilles tendinopathy in cellular and mouse models

Achilles tendinopathy has a high re-injury rate and poor prognosis. Development of effective therapy for Achilles tendinopathy is important. Excessive accumulation of ROS and resulting oxidative stress are believed to cause tendinopathy. Overproduction of hydrogen peroxide (H₂O₂), the most common ROS, could lead to the tendinopathy by causing oxidative damage, activation of endoplasmic reticulum (ER) stress and apoptotic death of tenocytes. Activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) is expected to alleviate oxidative stress and ER stress. Alda-1 is a selective and potent activator of ALDH2. In this study, we examined the cytoprotective benefit of Alda-1, an activator of ALDH2, on H₂O₂-induced Achilles tendinopathy in cellular and mouse models. We prepared cellular and mouse models of Achilles tendinopathy by treating cultured Achilles tenocytes and Achilles tendons with oxidative stressor H₂O₂. Subsequently, we studied the protective benefit of Alda-1 on H₂O₂-induced Achilles tendinopathy. Alda-1 pretreatment attenuated H₂O₂-induced cell death of cultured Achilles tenocytes. Treatment of Alda-1 prevented H₂O₂-induced oxidative stress and depolarization of mitochondrial membrane potential in tenocytes. Application of Alda-1 attenuated H₂O₂-triggered mitochondria- and ER stress-mediated apoptotic cascades in cultured tenocytes. Alda-1 treatment ameliorated the severity of H₂O₂-induced Achilles tendinopathy in vivo by preventing H₂O₂-induced pathological histological features of Achilles tendons, apoptotic death of Achilles tenocytes and upregulated expression of inflammatory cytokines IL-1β and TNF-α. Our results provide the evidence that ALDH2 activator Alda-1 ameliorates H₂O₂-induced Achilles tendinopathy. Alda-1 could be used for preventing and treating Achilles tendinopathy.

The Apoptosis Pathway and CASP8 Variants Conferring Risk for Acute and Overuse Musculoskeletal Injuries

Rotator cuff tendinopathy (RCT), anterior cruciate ligament (ACL) ruptures, and carpal tunnel syndrome (CTS), are examples of chronic (RCT and CTS) and acute (ACL ruptures) musculoskeletal soft tissue injuries. These injuries are multifactorial in nature, with several identified intrinsic and extrinsic risk factors. Previous studies have implicated specific sequence variants within genes encoding structural and regulatory components of the extracellular matrix of tendons and/ligaments to predispose individuals to these injuries. An example, includes the association of sequence variants within the apoptotic regulatory gene, caspase-8 (CASP8) with other musculoskeletal injury phenotypes, such as Achilles tendinopathy. The primary aim of this study was, therefore, to investigate previously implicated DNA sequence variants within CASP8: rs3834129 (ins/del) and rs1045485 (G/C), and the rs13113 (T/A) identified using a whole exome sequencing approach, with risk of musculoskeletal injury phenotypes (RCT, ACL ruptures, and CTS) in three independent studies. In addition, the aim was to implicate a CASP8 genomic interval in the modulation of risk of RCT, ACL ruptures, or CTS. It was found that the AA genotype of CASP8 rs13113 (T/A) was independently associated with increased risk for CTS. In addition, it was found that the del-C haplotype (rs3834129-rs1045485) was significantly associated with non-contact ACL ruptures, which is in alignment with previous research findings. Collectively, the results of this study implicate the apoptosis pathway as biologically significant in the underlying pathogenesis of musculoskeletal injury phenotypes. These findings should be repeated in larger sample cohorts and across different populations. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:680-688, 2020.

Targeting the NF-κB signaling pathway in chronic tendon disease

Tendon disorders represent the most common musculoskeletal complaint for which patients seek medical attention; inflammation drives tendon degeneration before tearing and impairs healing after repair. Clinical evidence has implicated the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway as a correlate of pain-free return to function after surgical repair. However, it is currently unknown whether this response is a reaction to or a driver of pathology. Therefore, we aimed to understand the clinically relevant involvement of the NF-κB pathway in tendinopathy, to determine its potential causative roles in tendon degeneration, and to test its potential as a therapeutic candidate. Transcriptional profiling of early rotator cuff tendinopathy identified increases in NF-κB signaling, including increased expression of the regulatory serine kinase subunit IKKβ, which plays an essential role in inflammation. Using cre-mediated overexpression of IKKβ in tendon fibroblasts, we observed degeneration of mouse rotator cuff tendons and the adjacent humeral head. These changes were associated with increases in proinflammatory cytokines and innate immune cells within the joint. Conversely, genetic deletion of IKKβ in tendon fibroblasts partially protected mice from chronic overuse-induced tendinopathy. Furthermore, conditional knockout of IKKβ improved outcomes after surgical repair, whereas overexpression impaired tendon healing. Accordingly, targeting of the IKKβ/NF-κB pathway in tendon stromal cells may offer previously unidentified therapeutic approaches in the management of human tendon disorders.

Tendon healing in presence of chronic low-level inflammation: a systematic review

BACKGROUND

Tendinopathy is a common musculoskeletal condition affecting subjects regardless of their activity level. Multiple inflammatory molecules found in ex vivo samples of human tendons are related to the initiation or progression of tendinopathy. Their role in tendon healing is the subject of this review.

SOURCES OF DATA

An extensive review of current literature was conducted using PubMed, Embase and Cochrane Library using the term 'tendon', as well as some common terms of tendon conditions such as 'tendon injury OR (tendon damage) OR tendonitis OR tendinopathy OR (chronic tendonitis) OR tendinosis OR (chronic tendinopathy) OR enthesitis' AND 'healing' AND '(inflammation OR immune response)' as either key words or MeSH terms.

AREAS OF AGREEMENT

An environment characterized by a low level of chronic inflammation, together with increased expression of inflammatory cytokines and growth factors, may influence the physiological tendon healing response after treatment.

AREAS OF CONTROVERSY

Most studies on this topic exhibited limited scientific translational value because of their heterogeneity. The evidence associated with preclinical studies is limited.

GROWING POINTS

The role of inflammation in tendon healing is still unclear, though it seems to affect the overall outcome. A thorough understanding of the biochemical mediators of healing and their pathway of pain could be used to target tendinopathy and possibly guide its management.

AREAS TIMELY FOR DEVELOPING RESEARCH

We require further studies with improved designs to effectively evaluate the pathogenesis and progression of tendinopathy to identify cellular and molecular targets to improve outcomes.

Degenerative rotator cuff tears are associated with a low Omega-3 Index

BACKGROUND

The etiology of degenerative rotator cuff tears is multifactorial but chronic inflammation plays an important role in the pathogenesis. Some polyunsaturated fatty acids (PUFA) can modulate inflammation and marine n-3 (Omega-3) PUFA have anti-inflammatory effects. We hypothesized that the Omega-3 Index is lower in patients with degenerative rotator cuff tears when compared to controls without rotator cuff tendinopathy.

METHODS

From 684 consecutive patients with full thickness rotator cuff tears 655 were excluded because of possible bias. In the remaining 29 patients (22 m, 7 f; 53,9 y) with degenerative full thickness rotator-cuff tears, erythrocyte fatty acids were analyzed using the HS-Omega-3 Index^® methodology. 15 healthy volunteers (10 m, 5 f; 52.5y) served as a control.

RESULTS

The Omega-3 Index (% EPA + DHA) was 5.01% (95% CI: 3.81-4.66) in patients and 6.01% (95% CI: 4.48-5.72) in controls (p = 0.028) CONCLUSIONS: Patients with full thickness degenerative rotator cuff tears had a significantly lower Omega-3 Index than controls without rotator cuff tendinopathy. Whether a lower Omega-3 Index represents an independent risk factor for degenerative rotator cuff tears should be further investigated, e.g. in a longitudinal study.

Functional polymorphisms within the inflammatory pathway regulate expression of extracellular matrix components in a genetic risk dependent model for anterior cruciate ligament injuries

OBJECTIVES

To investigate the functional effect of genetic polymorphisms of the inflammatory pathway on structural extracellular matrix components (ECM) and the susceptibility to an anterior cruciate ligament (ACL) injury.

DESIGN

Laboratory study, case-control study.

METHODS

Eight healthy participants were genotyped for interleukin (IL)1B rs16944 C>T and IL6 rs1800795 G>C and classified into genetic risk profile groups. Differences in type I collagen (COL1A1), type V collagen (COL5A1), biglycan (BGN) and decorin (DCN) gene expression were measured in fibroblasts either unstimulated or following IL-1β, IL-6 or tumor necrosis factor (TNF)-α treatment. Moreover, a genetic association study was conducted in: (i) a Swedish cohort comprised of 116 asymptomatic controls (CON) and 79 ACL ruptures and (ii) a South African cohort of 100 CONs and 98 ACLs. Participants were genotyped for COL5A1 rs12722 C>T, IL1B rs16944 C>T, IL6 rs1800795 G>C and IL6R rs2228145 G>C.

RESULTS

IL1B high-risk fibroblasts had decreased BGN (p=0.020) and COL5A1 (p=0.012) levels after IL-1β stimulation and expressed less COL5A1 (p=0.042) following TNF-α treatment. Similarly, unstimulated IL6 high-risk fibroblasts had lower COL5A1 (p=0.012) levels than IL6 low-risk fibroblasts. In the genetic association study, the COL5A1-IL1B-IL6 T-C-G (p=0.034, Haplo-score 2.1) and the COL5A1-IL1B-IL6R T-C-A (p=0.044, Haplo-score: 2.0) combinations were associated with an increased susceptibility to ACL injury in the Swedish cohort when only male participants were evaluated.

CONCLUSIONS

This study shows that polymorphisms within genes of the inflammatory pathway modulate the expression of structural and fibril-associated ECM components in a genetic risk depended manner, contributing to an increased susceptibility to ACL injuries.

Immunohistochemical features of rotator cuff tendinopathy

BACKGROUND

Rotator cuff tendinopathy is a common musculoskeletal ailment in sedentary and athletic individuals. Various mediators of inflammation have been detected in human tendons: they are thought to initiate or progress the course of tendinopathy.

SOURCES OF DATA

An online search was conducted using AMED, CINAHL, Embase, The Cochrane Library, PEDro and Pubmed, using the terms tendinopathy, tendon, tendinitis, tendinosis, histology, histopathology, immunohistochemistry, immunohistochemical, rotator cuff and pain.

AREAS OF AGREEMENT

Histological examination of tendinopathic tendons shows degeneration of the collagen structure and infiltration of fat and vessels, together with increased expression of inflammatory cytokines, MMP-1, 2, 3, 9, 13, vascular endothelial growth factor and Hypoxia inducible factor (HIF).

AREAS OF CONTROVERSY

Most of the studies about this topic exhibited limited validity because of lack of appropriately matched controls and no inclusion or exclusion criteria. The evidence associated with the histopathological analysis of the rotator cuff is limited.

GROWING POINTS

The histochemical and immunohistochemical features of rotator cuff tendinopathy are still unclear. A thorough understanding of the vascularity, innervation and biochemical mediators of pain could be used to target rotator cuff pathology, and possibly guide the therapy of painful rotator cuff disorders.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is a need for a validated reproducible method of rotator cuff tendon biopsy evaluation. We require further studies with improved designs to effectively evaluate the histological and immunohistochemical features of rotator cuff tendinopathy.