Biochemical markers in the synovial fluid of glenohumeral joints from patients with rotator cuff tear

Exploring the impact of vitamin D on tendon health: a comprehensive review

Tendons are vital components of the musculoskeletal system, facilitating movement and supporting mechanical loads. Emerging evidence suggests that vitamin D, beyond its well-established role in bone health, exerts significant effects on tendon physiology. The aim of this manuscript is to review the impact of vitamin D on tendons, focusing on its mechanisms of action, clinical implications, and therapeutic applications. A comprehensive search of scientific electronic databases was conducted to identify articles on the effects of vitamin D on tendon health. Fourteen studies were included in this review. Five studies were performed in vitro, and nine studies were conducted in vivo. Despite some conflicting results, the included studies showed that vitamin D regulates collagen synthesis, inflammation, and mineralization within tendons through its interaction with vitamin D receptors. Epidemiological studies link vitamin D deficiency with tendon disorders, including tendinopathy and impaired healing. Supplementation with vitamin D shows promise in improving tendon strength and function, particularly in at-risk populations such as athletes and the elderly. Future research should address optimal supplementation strategies and explore the interplay between vitamin D and other factors influencing tendon health. Integrating vitamin D optimization into clinical practice could enhance tendon integrity and reduce the burden of tendon-related pathologies.

Basic calcium phosphate crystals induce the expression of extracellular matrix remodelling enzymes in tenocytes

OBJECTIVES

Basic calcium phosphate (BCP) crystals contribute to several syndromes associated with tendon disease, including acute calcific tendinitis and Milwaukee shoulder syndrome. Interactions between BCP crystals and tenocytes (tendon cells) may contribute to these clinical syndromes. This study aimed to determine the direct effects of BCP crystals on tenocyte function and viability.

METHODS

In vitro assays were used to assess changes in human tenocytes cultured with BCP crystals. Real-time PCR was used to determine changes in the expression of tendon-related genes and extracellular matrix remodelling enzymes (MMPs; a disintegrin and metalloproteases, ADAMTS; and tissue inhibitor of metalloproteinases, TIMPs). ELISA was used to measure protein concentrations in tenocyte supernatants. MTT and alamarBlue™ assays were used to determine changes in cell viability.

RESULTS

BCP crystals upregulated tenocyte gene expression of MMP-1, MMP-3, ADAMTS-4 and TIMP-1 after 24 h. Time-course experiments showed expression peaked at 8 h for TIMP-1 and 48 h for MMP-1 and ADAMTS-4. Cyclooxygenase (COX)-1 gene expression was upregulated after 48 h. Tenocytes did not alter expression of scleraxis and tendon collagens, and expression of pro-inflammatory cytokines was not induced with BCP crystals. BCP crystals increased tenocyte release of prostaglandin E2 (PGE2) and MMP-1 protein after 24 h. However, neither COX-1 inhibition nor COX-2 inhibition led to consistent change in BCP crystal-induced tenocyte gene expression of extracellular matrix remodelling enzymes. BCP crystals had no effect on tenocyte viability.

CONCLUSION

BCP crystals induce extracellular matrix remodelling enzymes, but not inflammatory cytokines, in tenocytes.

Macroscopic aspects of glenohumeral synovitis are related to rotator cuff tear severity

BACKGROUND

The microscopic pattern of inflammatory mediators associated with rotator cuff pathology is well documented; however, little is known regarding the contemporary presence of macroscopic inflammatory joint involvement. Our aim was to investigate shoulder synovitis in a large group of patients with different sized rotator cuff tears (RCTs) and to correlate the degree of macroscopic inflammatory changes of the glenohumeral joint with RCT severity.

MATERIALS AND METHODS

A total of 296 consecutive patients (169 F, 127 M; mean age ± standard deviation: 60.75 ± 7.91) submitted to arthroscopic RCT repair were enrolled. RCT was classified intraoperatively. Glenohumeral synovitis was investigated according to 4 parameters (Davis classification 2017: capsule color, villous projections, capillaries, and axillary recess). A total score was calculated, and a 3-grade severity scale was introduced. Statistics was performed.

RESULTS

Intraclass correlation coefficient (ICC) results show good to excellent reliability: capsule color (ICC: 0.95; 95% confidence interval [CI]: 0.89-0.99), villous projections (ICC: 0.90; 95% CI: 0.85-0.95), capillaries (ICC: 0.91; 95% CI: 0.86-0.95), and axillary recess (ICC: 0.55; 95% CI: 0.80-0.89).The synovitis total score was found to be 1.47 ± 1.16, 2.86 ± 1.84, and 3.99 ± 1.64 in patients with type I, II, and III RCTs, respectively. A significant difference was found between groups (P < .001). The prevalence of all the examined parameters was found to be significantly different between the different sized RCT groups (capsule color: P < .001; villous projections: P < .001; capillaries: P < .001; and axillary recess: P < .001). According to a 3-grade severity scale, the prevalence of absent, mild, and severe glenohumeral synovitis significantly differed between the RCT severity groups (P < .001).

CONCLUSIONS

The present study demonstrated that synovitis is a constant finding of rotator cuff pathology; it is present in 75% of patients with RCTs and correlates with tear severity. Whether synovitis is the cause or effect of RCT is still questionable. Further studies are also needed to better understand its role as a pain generator, as documented in other diseases.

Elevation of MMP1 and ADAMTS5 mRNA expression in glenohumeral synovia of patients with hypercholesterolemia

Background

Epidemiological studies have reported a positive association between hypercholesterolemia and shoulder disease. Previous studies have focused on the effect of hypercholesterolemia on tendinopathy. Moreover, hypercholesterolemia has also been linked to joint pathology in the knee and hand. However, the effect of hyperlipidemia on glenohumeral joint remain unclear. A hypercholesterolemic condition has been reported to alter levels of A Disintegrin and Metalloprotease with Thrombospondin Motifs (ADAMTSs) and matrix metalloproteases (MMPs) in synovium of the knee joint. Here, we evaluated the mRNA expression of ADAMTSs and MMPs in the glenohumeral synovium of patients with and without hypercholesterolemia.

Methods

Study participants were 73 patients who underwent arthroscopic rotator cuff repair for degenerative rotator cuff tears. They were divided into two groups according to total cholesterol (TC) and triglyceride levels. Synovial membrane samples were harvested at the rotator interval during surgery, and mRNA expression levels of the aggrecanases ADAM-TS4 and ADAM-TS5 and MMPs (MMP-1, 3, 9, and 13) were analyzed quantitatively.

Results

ADAM-TS5 and MMP1 mRNA levels were significantly higher in the high TC group than in the low TC group (P = 0.023 and P = 0.025, respectively). In contrast, no significant differences were observed in ADAMTS4 or MMPs 3, 9, and 13 (ADAMTS4, P = 0.547; MMP3, P = 0.55; MMP9, P = 0.521; and MMP13, P = 0.785).

Conclusion

Hypercholesterolemia may alter MMP1 and ADAMTS5 expression in the synovium of the glenohumeral joint.

Evaluating various radiographic methods of shoulder joint damage in patients with rheumatoid arthritis receiving biological disease-modifying antirheumatic drugs

Objectives

This study aims to clarify shoulder joint damage in rheumatoid arthritis patients receiving biological disease-modifying antirheumatic drugs (bDMARDs) and the relationship between joint damage and clinical factors.

Patients and methods

In this retrospective study conducted between April 2005 and December 2008, 36 shoulders in 19 patients (2 males, 17 females; mean age: 58.9 years; range 42 to 75 years) were evaluated at baseline and two years after the initiation of bDMARD therapy with infliximab (n=14) or etanercept (n=5). Standard anteroposterior radiographs of the shoulder joints were taken at baseline and two years after institution of biological therapy. Structural damage in the shoulder joints was assessed using the Larsen scoring method, the medial displacement index (MDI), and the upward migration index (UMI).

Results

There was a significant correlation between MDI, UMI, and Larsen grade before biological therapy. Univariate analysis revealed that the disease activity score 28-count erythrocyte sedimentation rate (ESR) at baseline (odds ratio [OR]: 4.298) was associated with progression of MDI. But multivariate logistic regression revealed that there was no association with the progression of MDI. Univariate analysis revealed that ESR at baseline (OR: 0.967) and matrix metalloproteinase-3 (MMP-3) at baseline (OR: 0.996) were associated with the progression of UMI. Multivariate logistic regression revealed that MMP-3 at baseline (OR: 0.994) was independently associated with the progression of UMI.

Conclusion

Medial displacement index and UMI correlated with the Larsen grade of the shoulder joint strongly and moderately, respectively. This study suggests that MDI and UMI may help to evaluate radiographic progression of damage in shoulder joints in patients on bDMARDs, which is difficult to detect using the Larsen grade.

Monitoring Changes in Biochemical and Biomechanical Properties of Collagenous Tissues Using Label-Free and Nondestructive Optical Imaging Techniques

We demonstrate the ability of nondestructive optical imaging techniques such as second-harmonic generation (SHG), two-photon fluorescence (TPF), fluorescence lifetime imaging (FLIM), and Raman spectroscopy (RS) to monitor biochemical and mechanical alterations in tissues upon collagen degradation. Decellularized equine pericardium (EP) was treated with 50 μg/mL bacterial collagenase at 37 °C for 8, 16, 24, and 32 h. The SHG ratio (defined as the normalized ratio between SHG and TPF signals) remained unchanged for untreated EP (stored in phosphate-buffered solution (PBS)), whereas treated EP showed a trend of a decreasing SHG ratio with increasing collagen degradation. In the fluorescence domain, treated EP experienced a red-shifted emission and the fluorescence lifetime had a trend of decreasing lifetime with increasing collagen digestion. RS monitors collagen degradation, the spectra had less intense Raman bands at 814, 852, 938, 1242, and 1270 cm^-1. Non-negative least-squares (NNLS) modeling quantifies collagen loss and relative increase of elastin. The Young's modulus, derived from atomic force microscope-based nanoindentation experiments, showed a rapid decrease within the first 8 h of collagen degradation, whereas more gradual changes were observed for optical modalities. We conclude that optical imaging techniques like SHG, RS, and FLIM can monitor collagen degradation in a label-free manner and coarsely access mechanical properties in a nondestructive manner.

Vitamin D and the athlete-patient: state of the art

Vitamin D deficiency is common in athletes. The conventional measurement of vitamin D levels provides a general indicator of body stores. However, there are nuances in its interpretation as values of 25(OH)D do not correlate absolutely with the amount of 'bioavailable' vitamin to the cells. Vitamin D should be regarded as a hormone and influences between 5% and 10% of our total genome. Determining the precise effect of the vitamin, isolated from the actions of other cofactors, is not straightforward and restricts our complete understanding of all of its actions. Deficiency has harmful effects on not only bone and muscle but also wider areas, including immunity and respiratory and neurological activities. More caution should be applied regarding the ability of supranormal vitamin D levels to elevate athletic performance. Hopefully, future research will shed more light on optimal levels of vitamin D and supplementation regimes, and improved understanding of its intracellular control of our genetic mechanisms and how extrinsic influences modify its activity.

Synovial Fluid Volume at the Time of Arthroscopic Rotator Cuff Repair Correlates With Tear Size

Background

Inflammatory biomarkers are increased in the synovium and tendon of rotator cuff tears. Several studies demonstrate an associated increase in these markers and size of the tear, with implications of chondral destruction leading to rotator cuff tear arthropathy and glenohumeral arthritis.

Methods

This is a prospective study of 105 patients undergoing arthroscopic rotator cuff repair in which intra-articular synovial fluid was aspirated just prior to arthroscopy. Adult patients with a partial or full-thickness rotator cuff tear undergoing arthroscopic repair were included, and those with inflammatory arthritis, active infection, open cuff repair, intraoperative findings of osteoarthritis, or those undergoing revision cuff repair were excluded.

Results

The average patient age was 58 years (range 33-74 years), with 59 (56.2%) males. The mean aspirate volume of partial tears was 0.76 ± 0.43 mL, small tears 1.46 ± 1.88 mL, medium tears 3.04 ± 2.21 mL, and large tears 6.60 ± 3.23 mL. Full-thickness versus partial tears had significantly more synovial fluid (3.64 vs. 0.76 mL, respectively, p < 0.0001). An aspiration volume of 1.5 mL or greater resulted in 91.3% specificity and 96.8% positive predictive value for a full-thickness tear. Smoking (p = 0.017), tear size (p < 0.0001), and tears of the infraspinatus (p = 0.048) were significantly correlated with synovial fluid volume. Age, body mass index, chronicity of tear, sex, subscapularis involvement, supraspinatus involvement, and teres minor involvement had no association to synovial fluid volume.

Conclusion

Preoperative aspiration of the glenohumeral joint to identify the volume of synovial fluid can aid to identify full-thickness rotator cuff tears, and increased fluid volume should alert the clinician of a large tear.

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.

Arthroscopic Rotator Cuff Repair in 2019: Linked, Double Row Repair for Achieving Higher Healing Rates and Optimal Clinical Outcomes

The primary aim of rotator cuff repair surgery is to restore the musculotendinous units by creating a complete, tension-free repair construct that optimizes conditions for tendon-to-bone healing. There are many factors outside the control of the surgeon that are capable of affecting the healing process; however, there are also a number of important technical considerations that the surgeon can control, including familiarity with methods to deal with immobile tissues and techniques to perform novel repair constructs. It is clear that linked double row repairs are more likely to heal, and healed rotator cuff repairs best restore shoulder strength, improve patients' satisfaction, and maximize functional outcomes.

Full-thickness rotator cuff tear in rat results in distinct temporal expression of multiple proteases in tendon, muscle, and cartilage

The etiology of joint tissue degeneration following rotator cuff tear remains unclear. Thus, the purpose of this study was to understand the timeline of protease activity in the soft tissues of the shoulder (tendon, muscle, and cartilage) that may lead to down-stream degeneration following rotator cuff tear. A well-established rat model involving suprascapular nerve denervation and supraspinatus/infraspinatus tendon transection was employed. Histological staining and/or micro-computed tomography (µCT) were used to observe structural damage in the supraspinatus tendon and muscle, humeral head cartilage, and subchondral bone. Multiplex gelatin zymography was utilized to assess protease activity in the supraspinatus tendon and muscle, and humeral head cartilage. Zymography analysis demonstrated that cathepsins were upregulated in the first week in all tissues, while MMP-2 maintained prolonged activity in supraspinatus tendon between 1 and 3 weeks and increased only at 3 weeks in supraspinatus muscle. In supraspinatus tendon, increased cathepsin L and MMP-2 activity in the first week was concurrent with matrix disorganization and infiltration of inflammatory cells. In contrast, significant upregulation of cathepsin L and K activity in supraspinatus muscle and humeral head cartilage did not correspond to any visible tissue damage at 1 week. However, focal defects developed in half of all animals' humeral head cartilage by 12 weeks (volume: 0.12 ± 0.09 mm³ ). This work provides a more comprehensive understanding of biochemical changes to joint tissue over time following rotator cuff tear. Overall, this provides insight into potential therapeutic targets and will better inform ideal intervention times and treatments for each tissue. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:490-502, 2019.

A Systematic Summary of Systematic Reviews on the Topic of the Rotator Cuff

BACKGROUND

The number of systematic reviews and meta-analyses published on the rotator cuff (RC) has increased markedly.

PURPOSE

To quantify the number of systematic reviews and meta-analyses published on the RC and to provide a qualitative summary of the literature.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic search for all systematic reviews and meta-analyses pertaining to the RC published between January 2007 and September 2017 was performed with PubMed, MEDLINE, and the Cochrane Database of Systematic Reviews. Narrative reviews and non-English language articles were excluded.

RESULTS

A total of 1078 articles were found, of which 196 met the inclusion criteria. Included articles were summarized and divided into 15 topics: anatomy and function, histology and genetics, diagnosis, epidemiology, athletes, nonoperative versus operative treatment, surgical repair methods, concomitant conditions and surgical procedures, RC tears after total shoulder arthroplasty, biological augmentation, postoperative rehabilitation, outcomes and complications, patient-reported outcome measures, cost-effectiveness of RC repair, and quality of randomized controlled trials.

CONCLUSION

A qualitative summary of the systematic reviews and meta-analyses published on the RC can provide surgeons with a single source of the most current literature.

Enthesis Repair: Challenges and Opportunities for Effective Tendon-to-Bone Healing

On May 22, 2017, the National Institutes of Health (NIH)/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) hosted a roundtable on "Innovative Treatments for Enthesis Repair." A summary of the roundtable discussion, as well as a list of the extramural participants, can be found at https://www.niams.nih.gov/about/meetings-events/roundtables/roundtable-innovative-treatments-enthesis-repair. This paper reviews the challenges and opportunities for developing effective treatment strategies for enthesis repair that were identified at the roundtable discussion.

Synovial fluid biomarkers: association with chronic rotator cuff tear severity and pain

BACKGROUND

We tested the hypothesis that biomarkers in the synovial fluid of the glenohumeral (shoulder) joint are correlated with visual analog scale (VAS) scores, functional scores, and ultrasound findings of chronic rotator cuff tear (RCT) severity.

METHODS

We measured biomarkers in shoulder joint synovial fluid of 42 patients with partial-thickness (21), nonmassive full-thickness (10), and massive full-thickness (11) RCTs. Pain duration, tear severity, and VAS and functional scores were compared with interleukin (IL) 1β, IL-6, matrix metalloproteinase (MMP) 1, and MMP-13 levels.

RESULTS

Both MMP-1 and MMP-13 levels were significantly highest in the massive full-thickness group. MMP-13 levels were significantly different between groups, but proinflammatory cytokine IL-1β and IL-6 levels were not. However, IL-1β levels were significantly positively correlated with VAS (r = 0.66; P <.01) and functional scores (r = 0.61; P <.01), but IL-6, MMP-1, and MMP-13 levels were not.

CONCLUSIONS

IL-1β levels in shoulder synovial fluid correlated positively with shoulder pain and functional scores in patients with chronic RCTs. Both MMP-1 and MMP-13 levels were altered and increased with cuff tear severity.

A hydroxamic acid–methacrylated collagen conjugate for the modulation of inflammation-related MMP upregulation

The selective covalent coupling of hydroxamic acid functions on to methacrylated type I collagen led to UV-cured networks with inherent MMP-modulating capability and enhanced proteolytic stability.

Aetiopathogenesis of cuff-tear arthropathy: Could juvenile joint laxity be considered a predisposing factor?

PURPOSE

Although many hypotheses have been formulated, aetiopathogenesis of cuff-tear arthropathy (CTA) is still motive for discussion. Since prevalence of CTA is notoriously higher in women, as is joint hypermobility, we hypothesised a possible correlation between the two conditions.

METHODS

One hundred thirty-three (n = 133) consecutive patients with glenohumeral osteoarthritis [48 men, 85 women; mean age (SD) 72.32 (7.05)] were divided into two groups: Groups 1 (CTA) and 2 (concentric shoulder arthropathy) comprised 71 (22 men, 49 women) and 62 (26 men, 36 women), respectively. The presence of current or previous joint hypermobility was assessed using two standardised methodologies: the Beighton criteria score, and a five-item self-report questionnaire. Data were submitted to statistical analysis.

RESULTS

A moderate association between Beighton criteria and the five-item self-report (φ = 0.481, p < 0.001) was detected. Beighton criteria led to a diagnosis of joint hypermobility in 16 patients (22.5%) in Group 1 and 15 (24.2%) in Group 2. According to five-item self-report questionnaire, juvenile joint laxity was diagnosed in 11 (15.5%) and 12 (19.4%) patients in Groups 1 and 2, respectively. No significant association between groups and the Beighton criteria [χ²(1) = 0.051, p = 0.82] and five-item self-report questionnaire [χ²(1) = 0.67, p = 0.41] was found.

CONCLUSION

Juvenile joint hyperlaxity is not a predisposing factor for cuff arthropathy. Further studies will be needed to explain CTA aetiopathogenesis.

LEVELS OF EVIDENCE

III.

Differences of RNA Expression in the Tendon According to Anatomic Outcomes in Rotator Cuff Repair

BACKGROUND

Despite increased understanding of the pathophysiology of rotator cuff tears and the evolution of rotator cuff repair, healing failure remains a substantial problem. The critical roles played by biological factors have been emphasized, but little is known of the implications of gene expression profile differences at the time of repair.

PURPOSE

To document the relationship between the perioperative gene expression of healed and unhealed rotator cuffs by RNA microarray analysis.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Superior (supraspinatus involvement) and posterosuperior (supraspinatus and infraspinatus involvement) tears were included in the study. Samples of rotator cuff tendons were prospectively collected during rotator cuff surgery. Three samples were harvested at the tendon ends of tears from the anterior, middle (apex), and posterior parts using an arthroscopic punch. Seven patients with an unhealed rotator cuff were matched one-to-one with patients with a healed rotator cuff by sex, age, tear size, and fatty degeneration of rotator cuff muscles. mRNA microarray analysis was used to identify genetic differences between healed and unhealed rotator cuff tendons. Gene ontology and gene association files were obtained from the Gene Ontology Consortium, and the Gene Ontology system in DAVID was used to identify enhanced biological processes.

RESULTS

Microarray analyses identified 262 genes that were differentially expressed by at least 1.5-fold between the healed and unhealed groups. Overall, in the healed group, 103 genes were significantly downregulated, and 159 were significantly upregulated. DAVID Functional Annotation Cluster analysis showed that in the healed group, the genes most upregulated were related to the G protein-coupled receptor protein signaling pathway and to the neurological system. On the other hand, the genes most downregulated were related to immune and inflammatory responses. BMP5 was the gene most upregulated in the healed group, and the majority of downregulated genes were involved in the immune/inflammatory response.

CONCLUSION

The downregulation of inflammatory response genes and the upregulation of cell differentiation genes in torn rotator cuffs at the time of surgery are related to rotator cuff healing. These results provide useful baseline information for future biological studies on rotator cuff healing.

Supraspinatus tendon overuse results in degenerative changes to tendon insertion region and adjacent humeral cartilage in a rat model

The etiology of rotator cuff tendon overuse injuries is still not well understood. Furthermore, how this overuse injury impacts other components of the glenohumeral joint, including nearby articular cartilage, is also unclear. Therefore, this study sought to better understand the time course of tendon protease activity in a rat model of supraspinatus overuse, as well as determine effects of 10 weeks of overuse on humeral head articular cartilage. For these studies, multiplex gelatin zymography was used to characterize protease activity profiles in tendon and cartilage, while histological scoring/mechanical testing and micro-computed tomography (μCT) imaging were used to quantify structural damage in the supraspinatus tendon insertion and humeral articular cartilage, respectively. Histological scoring of supraspinatus tendon insertions revealed tendinopathic cellular and collagen fiber changes after 10 weeks of overuse when compared to controls, while mechanical testing revealed no significant differences between tensile moduli (overuse: 24.5 ± 11.5 MPa; control: 16.3 ± 8.7 MPa). EPIC-μCT imaging on humeral articular cartilage demonstrated significant cartilage thinning (overuse: 119.6 ± 6.34 μm; control: 195.4 ± 13.4μm), decreased proteoglycan content (overuse: 2.1 ± 0.18 cm^-1 ; control: 1.65 ± 0.14 cm^-1 ), and increased subchondral bone thickness (overuse: 216.2 ± 10.9 μm; control: 192 ± 17.8μm) in the overuse animals. Zymography results showed no significant upregulation of cathepsins or matrix metalloproteinases in tendon or cartilage at 2 or 10 weeks of overuse compared to controls. These results have further elucidated timing of protease activity over 10 weeks and suggest that damage occurs to other tissues in addition to the supraspinatus tendon in this overuse injury model. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1910-1918, 2017.

A comparative study of effect of autograft compared with allograft anterior cruciate ligament reconstruction on expressions of LOXs and MMPs

The present study aimed to compare the effect of autograft or allograft anterior cruciate ligament (ACL) reconstruction on the expressions of lipoxygenases (LOXs) and matrix metalloproteinases (MMPs) in a New Zealand white rabbit model. New Zealand white rabbits were divided randomly into control, sham, autograft and allograft groups. At the 4th and 8th week after operation, biomechanical testing was performed to measure the primary length, cross-sectional area, maximum tensile load and stiffness of ACL, and HE staining was used to observe cell morphology and fibre alignment of ACL. At the 2nd, 4th and 8th week after operation, quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemistry were applied to detect LOXs and MMPs expressions, and expressions of adenomatous polyposis coli (APC)/Wnt signalling pathway-related proteins. At the 4th and 8th week after operation, the maximum tensile load and stiffness were higher in the autograft group than in the allograft group, and the values at the 8th week were higher than those at the 4th week after operation. The fibroblast proliferation in the allograft group was more significant than that in the autograft group. Compared with the control group, LOXs and MMPs expressions and the positive expression rates of LOXs and MMPs proteins were elevated, and the values in the allograft group were higher than those in the autograft group at all time points. At 8th week after operation, compared with the autograft group, Wnt expression was higher and APC expression was lower in the allograft group. Autograft and allograft ACL reconstruction can promote LOXs and MMPs expressions by activating the APC/Wnt signalling pathway.

Effectiveness of Biologic Factors in Shoulder Disorders

Background:

Shoulder pathology can cause significant pain, discomfort, and loss of function that all interfere with activities of daily living and may lead to poor quality of life. Primary osteoarthritis and rotator cuff diseases with its sequalae are the main culprits. Management of shoulder disorders using biological factors gained an increasing interest over the last years. This interest reveals the need of effective treatments for shoulder degenerative disorders, and highlights the importance of a comprehensive and detailed understanding of the rapidly increasing knowledge in the field.

Methods:

This study will describe most of the available biology-based strategies that have been recently developed, focusing on their effectiveness in animal and clinical studies.

Results:

Data from in vitro work will also be briefly presented; in order to further elucidate newly acquired knowledge regarding mechanisms of tissue degeneration and repair that would probably drive translational work in the next decade. The role of platelet rich-plasma, growth factors, stem cells and other alternative treatments will be described in an evidence-based approach, in an attempt to provide guidelines for their clinical application. Finally, certain challenges that biologic treatments face today will be described as an initiative for future strategies.

Conclusion:

The application of different growth factors and mesenchymal stem cells appears as promising approaches for enhancing biologic repair. However, data from clinical studies are still limited, and future studies need to improve understanding of the repair process in cellular and molecular level and evaluate the effectiveness of biologic factors in the management of shoulder disorders.

Bmp-12 activates tenogenic pathway in human adipose stem cells and affects their immunomodulatory and secretory properties

BACKGROUND

Cell-based therapy is a treatment method in tendon injuries. Bone morphogenic protein 12 (BMP-12) possesses tenogenic activity and was proposed as a differentiating factor for stem cells directed to transplantation. However, BMPs belong to pleiotropic TGF-β superfamily and have diverse effect on cells. Therefore, the aim of this study was to determine if BMP-12 induces tenogenic differentiation of human adipose stem cells (hASCs) and how it affects other features of this population.

RESULTS

Human ASCs from 6 healthy donors were treated or not with BMP-12 (50 or 100 ng/ml, 7 days) and tested for gene expression (COLL1, SCX, MKH, DCN, TNC, RUNX2), protein expression (COLL1, COLL3, MKH), proliferation, migration, secretory activity, immunomodulatory properties and susceptibility to oxidative stress. RT-PCR revealed up-regulation of SCX, MKH and RUNX2 genes in BMP-12 treated cells (2.05, 2.65 and 1.87 fold in comparison to control, respectively, p < 0.05) and Western Blot revealed significant increase of COLL1 and MHK expression after BMP-12 treatment. Addition of BMP-12 significantly enhanced secretion of VEGF, IL-6, MMP-1 and MPP-8 by hASCs while had no effect on TGF-β, IL-10, EGF and MMP-13. Moreover, BMP-12 presence in medium attenuated inhibitory effect of hASCs on allo-activated lymphocytes proliferation. At the same time BMP-12 displayed no influence on hASCs proliferation, migration and susceptibility to oxidative stress.

CONCLUSION

BMP-12 activates tenogenic pathway in hASCs but also affects secretory activity and impairs immunomodulatory potential of this population that can influence the clinical outcome after cell transplantation.

Association of synovial inflammation and inflammatory mediators with glenohumeral rotator cuff pathology

HYPOTHESIS

We hypothesized that patients with full-thickness rotator cuff tears would have greater synovial inflammation compared with those without rotator cuff tear pathology, with gene expression relating to histologic findings.

METHODS

Synovial sampling was performed in 19 patients with full-thickness rotator cuff tears (RTC group) and in 11 patients without rotator cuff pathology (control group). Cryosections were stained and examined under light microscopy and confocal fluorescent microscopy for anti-cluster CD45 (common leukocyte antigen), anti-CD31 (endothelial), and anti-CD68 (macrophage) cell surface markers. A grading system was used to quantitate synovitis under light microscopy, and digital image analysis was used to quantify the immunofluorescence staining area. Quantitative polymerase chain reaction was performed for validated inflammatory markers. Data were analyzed with analysis of covariance, Mann-Whitney U, and Spearman rank order testing, with significance set at α = .05.

RESULTS

The synovitis score was significantly increased in the RTC group compared with controls. Immunofluorescence demonstrated significantly increased staining for CD31, CD45, and CD68 in the RTC vs control group. CD45+/68- cells were found perivascularly, with CD45+/68+ cells toward the joint lining edge of the synovium. Levels of matrix metalloproteinase-3 (MMP-3) and interleukin-6 were significantly increased in the RTC group, with a positive correlation between the synovitis score and MMP-3 expression.

CONCLUSIONS

Patients with full-thickness rotator cuff tears have greater levels of synovial inflammation, angiogenesis, and MMP-3 upregulation compared with controls. Gene expression of MMP-3 correlates with the degree of synovitis.

Biologic Treatments for Sports Injuries II Think Tank-Current Concepts, Future Research, and Barriers to Advancement, Part 2: Rotator Cuff

Rotator cuff tears are common and result in considerable morbidity. Tears within the tendon substance or at its insertion into the humeral head represent a considerable clinical challenge because of the hostile local environment that precludes healing. Tears often progress without intervention, and current surgical treatments are inadequate. Although surgical implants, instrumentation, and techniques have improved, healing rates have not improved, and a high failure rate remains for large and massive rotator cuff tears. The use of biologic adjuvants that contribute to a regenerative microenvironment have great potential for improving healing rates and function after surgery. This article presents a review of current and emerging biologic approaches to augment rotator cuff tendon and muscle regeneration focusing on the scientific rationale, preclinical, and clinical evidence for efficacy, areas for future research, and current barriers to advancement and implementation.

Development of an Arthroscopic Joint Capsule Injury Model in the Canine Shoulder

BACKGROUND

The natural history of rotator cuff tears can be unfavorable as patients develop fatty infiltration and muscle atrophy that is often associated with a loss of muscle strength and shoulder function. To facilitate study of possible biologic mechanisms involved in early degenerative changes to rotator cuff muscle and tendon tissues, the objective of this study was to develop a joint capsule injury model in the canine shoulder using arthroscopy.

METHODS

Arthroscopic surgical methods for performing a posterior joint capsulectomy in the canine shoulder were first defined in cadavers. Subsequently, one canine subject underwent bilateral shoulder joint capsulectomy using arthroscopy, arthroscopic surveillance at 2, 4 and 8 weeks, and gross and histologic examination of the joint at 10 weeks.

RESULTS

The canine subject was weight-bearing within eight hours after index and follow-up surgeries and had no significant soft tissue swelling of the shoulder girdle or gross lameness. Chronic synovitis and macroscopic and microscopic evidence of pathologic changes to the rotator cuff bony insertions, tendons, myotendinous junctions and muscles were observed.

CONCLUSIONS

This study demonstrates feasibility and proof-of-concept for a joint capsule injury model in the canine shoulder. Future work is needed to define the observed pathologic changes and their role in the progression of rotator cuff disease. Ultimately, better understanding of the biologic mechanisms of early progression of rotator cuff disease may lead to clinical interventions to halt or slow this process and avoid the more advanced and often irreversible conditions of large tendon tears with muscle fatty atrophy.

Identification of shoulder osteoarthritis biomarkers: comparison between shoulders with and without osteoarthritis

BACKGROUND

The biologic factors associated with shoulder osteoarthritis (OA) have not been elucidated. The purpose of this study was to investigate osteoarthritic biomarkers of the shoulder. To our knowledge, this is the first study to analyze shoulder cartilage for OA-associated genes and to examine human shoulder cartilage for a possible biomarker, connexin 43 (Cx43).

MATERIALS AND METHODS

Cartilage from 16 osteoarthritic and 10 nonosteoarthritic humeral heads was assessed for expression of the following genes by real-time polymerase chain reaction: types I, II, and X collagen; matrix metalloproteinases (MMPs); tissue inhibitors of MMP (TIMPs); interleukins; versican; cyclooxygenase 2 (Cox-2); inducible nitric oxide synthase (iNOS); tumor necrosis factor α (TNF-α); aggrecanase 2 (ADAMTS5); and Cx43.

RESULTS

In osteoarthritic shoulders, Cx43, Cox-2, versican, collagen type I, ADAMTS5, MMP-3, and TNF-α expressions were significantly increased compared with controls. TIMP-3 and iNOS trended toward significance, with robust expression in osteoarthritic shoulders and low expression in nonosteoarthritic shoulders. In osteoarthritic shoulders, gene expression of Cx43, ADAMTS5, collagen type I, Cox-2, versican, and TIMP-3 showed predominance (85-, 33-, 13-, 12-, 11.5-, and 3-fold increases, respectively) relative to nonosteoarthritic controls. Spearman correlation analysis showed significant correlations between Cx43 and collagen (types I, II, and X), MMP-9, TIMP-2 and TIMP-3, versican, Cox-2, iNOS, and ADAMTS5.

CONCLUSIONS

Certain genes are markedly upregulated in osteoarthritic shoulders compared with nonosteoarthritic shoulders, with Cx43, Cox-2, versican, collagen type I, ADAMTS5, MMP-3, and TNF-α expression being significantly increased. These genes might be useful biomarkers for examining shoulder OA.

CLINICAL RELEVANCE

Identification of osteoarthritic biomarkers can help us better understand shoulder OA and build the foundation for future research on disease progression and treatments.

Expression of modulators of extracellular matrix structure after anterior cruciate ligament injury

The ability of the anterior cruciate ligament (ACL) to heal after injury declines within the first 2 weeks after ACL rupture. To begin to explore the mechanism behind this finding, we quantified the expression of genes for collagen I and III, decorin, tenascin-C, and alpha smooth muscle actin, as well as matrix metalloproteinase (MMP)-1 and -13 gene expression within multiple tissues of the knee joint after ACL injury in a large animal model over a 2-week postinjury period. Gene expression of collagen I and III, decorin, and MMP-1 was highest in the synovium, whereas the highest MMP-13 gene expression levels were found in the ACL. The gene expression for collagen and decorin increased over the 2 weeks to levels approaching that in the ligament and synovium; however, no significant increase in either of the MMPs was found in the provisional scaffold. This suggests that although the ACL and synovium up-regulate both anabolic and catabolic factors, the provisional scaffold is primarily anabolic in function. The relative lack of provisional scaffold formation within the joint environment may thus be one of the key reasons for ACL degradation after injury.

Effect of diet-induced vitamin D deficiency on rotator cuff healing in a rat model

BACKGROUND

Few studies have considered hormonal influences, particularly vitamin D, on healing.

HYPOTHESIS

Vitamin D deficiency would have a negative effect on the structure of the healing tendon-bone interface in a rat model and would result in decreased tendon attachment strength.

STUDY DESIGN

Controlled laboratory study.

METHODS

Vitamin D deficiency was induced in 28 male Sprague-Dawley rats using a specialized vitamin D-deficient diet and ultraviolet light restriction. Serum levels of vitamin D were measured after 6 weeks. These vitamin D-deficient animals (experimental group) plus 32 rats with normal vitamin D levels (controls) underwent unilateral detachment of the right supraspinatus tendon from the greater tuberosity of the humerus, followed by immediate repair using bone tunnel suture fixation. The animals were sacrificed at 2- and 4-week intervals after surgery for biomechanical analysis. A paired t test was used to compare serum vitamin D levels at day 0 and at 6 weeks. A nonparametric Mann-Whitney U test was used to compare load-to-failure and stiffness values between the experimental group and controls. Bone density and new bone formation at the tendon insertion site on the greater tuberosity were assessed with micro-computed tomography (CT). The organization of collagen tissue, new bone formation, vascularity at the tendon-bone interface, fibrocartilage at the tendon-bone interface, and collagen fiber continuity between the tendon and bone tissue were evaluated with safranin O and picrosirius red staining.

RESULTS

Blood draws confirmed vitamin D deficiency at 6 weeks compared with time zero/baseline for rats in the experimental group (10.9 ng/mL vs 6.5 ng/mL, respectively; P < .001). Biomechanical testing demonstrated a significant decrease in load to failure in the experimental group compared with controls at 2 weeks (5.8 ± 2.0 N vs 10.5 ± 4.4 N, respectively; P < .006). There was no difference in stiffness at 2 weeks between the control and experimental groups. At 4 weeks, there was no significant difference in load to failure or stiffness between the control and experimental groups. Histological analysis showed less bone formation and less collagen fiber organization in the vitamin D-deficient specimens at 4 weeks as compared with controls. Micro-CT analysis showed no significant difference between groups for total mineral density and bone volume fraction of cortical, whole, or trabecular bone at 4 weeks.

CONCLUSION

The biomechanical and histological data from this study suggest that low vitamin D levels may negatively affect early healing at the rotator cuff repair site.

CLINICAL RELEVANCE

It is estimated that 1 billion people worldwide are vitamin D deficient. In the deficient state, acutely injured rotator cuffs may have a reduced ability for tendon healing. Further studies are needed to determine the exact mechanism by which vitamin D affects tendon healing and whether vitamin D supplementation can improve rotator cuff tendon healing and reduce the incidence of retears.

Evaluation of cartilage degeneration in a rat model of rotator cuff tear arthropathy

BACKGROUND AND HYPOTHESIS

Rotator cuff tears are the most common injury seen by shoulder surgeons. Glenohumeral osteoarthritis develops in many late-stage rotator cuff tear patients as a result of torn cuff tendons, termed "cuff tear arthropathy." However, the mechanisms of cuff tear arthropathy have not been fully established. It has been hypothesized that a combination of synovial and mechanical factors contribute equally to the development of cuff tear arthropathy. The goal of this study was to assess the utility of this model in investigating cuff tear arthropathy.

MATERIALS AND METHODS

We used a rat model that accurately reflects rotator cuff muscle degradation after massive rotator cuff tears through either infraspinatus and supraspinatus tenotomy or suprascapular nerve transection. Using a modified Mankin scoring system, we found significant glenohumeral cartilage damage after both rotator cuff tenotomy and suprascapular nerve transection after only 12 weeks.

RESULTS

Cartilage degeneration was similar between groups and was present on both the humeral head and the glenoid. Denervation of the supraspinatus and infraspinatus muscles without opening the joint capsule caused cartilage degeneration similar to that found in the tendon transection group.

CONCLUSIONS

Our results suggest that altered mechanical loading after rotator cuff tears is the primary factor in cartilage degeneration after rotator cuff tears. Clinically, understanding the process of cartilage degeneration after rotator cuff injury will help guide treatment decisions in the setting of rotator cuff tears.

LEVEL OF EVIDENCE

Basic science study, animal model.

Increased matrix metalloprotease-3 gene expression in ruptured rotator cuff tendons is associated with postoperative tendon retear

PURPOSE

The role of matrix metalloproteases (MMPs) in ruptured rotator cuff tendons remains unknown. This study aimed to investigate the gene expression of MMPs in ruptured rotator cuff tendons and to compare their expression levels between patients with and without postoperative tendon retear.

METHODS

Twenty-four patients (a median age of 61 years: interquartile range, 55-66 years) with full-thickness rotator cuff tears were examined in this study. The marginal site of the ruptured tendon was harvested during surgery. The mRNA expression levels of collagen types I and III, MMP-1, MMP-3, MMP-7, MMP-9, MMP-13, tissue inhibitor of MMP (TIMP)-1, and TIMP-2 were analysed by real-time reverse transcription polymerase chain reaction. Postoperative retear was evaluated by magnetic resonance imaging at a minimum of 1 year following surgery.

RESULTS

The mRNA expression levels of MMP-3 and TIMP-1 in ruptured rotator cuff tendons were significantly increased in patients with postoperative retear (n = 6), compared with patients without retear (n = 18) (P = 0.04). For collagens, MMP-1, MMP-7, MMP-9, MMP-13, and TIMP-2, there were no significant differences in the mRNA expression levels in ruptured tendons between patients with and without retear.

CONCLUSIONS

These results suggest that, in addition to up-regulation of TIMP-1 gene expression, increased MMP-3 gene expression in ruptured rotator cuff tendons is associated with postoperative tendon retear. Thus, drug therapy specifically targeting MMP-3 after rotator cuff repair should be considered in the future.

Metalloproteases and tendinopathy

Matrix metalloproteinases (MMP) are involved in the development of tendinopathy. These potent enzymes completely degrade all components of the connective tissue, modify the extracellular matrix (ECM), and mediate the development of painful tendinopathy. To control the local activity of activated proteinases, the same cells produce tissue inhibitors of metalloproteinases (TIMP). These latter bind to the enzyme and prevent degradation. The balance between the activities of MMPs and TIMPs regulates tendon remodeling, whereas an imbalance produces a collagen dis-regulation and disturbances in tendons. ADAMs (a disintegrin and metalloproteinase) are cell membrane-linked enzymes with proteolytic and cell signaling functions. ADAMTSs (ADAM with thrombospondin motifs) are secreted into the circulation and constitute a heterogenous family of proteases with both anabolic and catabolic functions. Further studies are needed to better define the mechanism of action, and whether these new strategies are safe and effective in larger models.

Biologics in the management of rotator cuff surgery

The rotator cuff enthesis is not reestablished after a rotator cuff repair. Instead, a scar-mediated healing response occurs at the tendon-bone interface, which is notably weaker than the native enthesis and thus more prone to failure. Biological augmentation through growth factors, AASs, biomimetic scaffolds, or siRNA therapy has the potential to enhance the healing response. The ultimate key, however, is in determining which of these enables a more regenerative healing response of the native tissue rather than enhanced production of scar tissue. In addition, the optimal combination of factors, dosing, and delivery methods remains to be clearly elucidated. Biological augmentation and tissue engineering for tendon healing remains promising, but much work still needs to be done.

Biologically based strategies to augment rotator cuff tears

Lesions of the rotator cuff (RC) are among the most frequent tendon injuries. In spite of the developments in both open and arthroscopic surgery, RC repair still very often fails. In order to reduce the failure rate after surgery, several experimental in vitro and in vivo therapy methods have been developed for biological improvement of the reinsertion. This article provides an overview of the current evidence for augmentation of RC reconstruction with growth factors. Furthermore, potential future therapeutic approaches are discussed. We performed a comprehensive search of the PubMed database using various combinations of the keywords “tendon,” “rotator cuff,” “augmentation,” “growth factor,” “platelet-rich fibrin,” and “platelet-rich plasma” for publications up to 2011. Given the linguistic capabilities of the research team, we considered publications in English, German, French, and Spanish. We excluded literature reviews, case reports, and letters to the editor.

A systematic review of the histological and molecular changes in rotator cuff disease

INTRODUCTION

The pathogenesis of rotator cuff disease (RCD) is complex and not fully understood. This systematic review set out to summarise the histological and molecular changes that occur throughout the spectrum of RCD.

METHODS

We conducted a systematic review of the scientific literature with specific inclusion and exclusion criteria.

RESULTS

A total of 101 studies met the inclusion criteria: 92 studies used human subjects exclusively, seven used animal overuse models, and the remaining two studies involved both humans and an animal overuse model. A total of 58 studies analysed supraspinatus tendon exclusively, 16 analysed subacromial bursal tissue exclusively, while the other studies analysed other tissue or varying combinations of tissue types including joint fluid and muscle. The molecular biomarkers that were altered in RCD included matrix substances, growth factors, enzymes and other proteins including certain neuropeptides.

CONCLUSIONS

The pathogenesis of RCD is being slowly unravelled as a result of the significant recent advances in molecular medicine. Future research aimed at further unlocking these key molecular processes will be pivotal in developing new surgical interventions both in terms of the diagnosis and treatment of RCD.

A watertight construct in arthroscopic rotator cuff repair

BACKGROUND

It is unknown which type of rotator cuff repair technique best isolates the healing zone interface from the synovial fluid environment. The purpose of this study was to determine the leakage area and pattern onto the rotator cuff footprint after 3 different rotator cuff repairs.

MATERIALS AND METHODS

Six fresh frozen cadaveric glenohumeral joints in each of 3 groups were injected with gelatin to a pressure of 103 mm Hg (∼2 psi) after 1 of 3 different rotator cuff repairs of a supraspinatus tear: (1) single-row repair (SR), (2) knotless transosseous equivalent repair (KTE), and (3) traditional transosseous equivalent repair (TTE), which uses medial tied knots. Specimens were cycled in external rotation and abduction and were cooled to allow the gelatin to solidify. The supraspinatus was dissected off the footprint and photographs were taken. Scion Image (Frederick, MD, USA) was used to quantify the area.

RESULTS

The average area of leakage was 1.09 cm(2) for the SR and 1.15 cm(2) for the KTE. The TTE did not demonstrate any leakage. The pattern of leakage for the KTE was medial and central on the footprint, whereas the SR demonstrated leakage up to the tied knots. The difference in the area of leakage in the SR and KTE compared with the TTE was statistically significant. There was no difference in area of leakage between the SR and KTE.

CONCLUSION

A transosseous equivalent repair technique best prevents leakage onto the rotator cuff footprint compared with single-row and knotless repairs.

Matrix metalloproteinase levels as a marker for rotator cuff tears

Although many studies report the role of matrix metalloproteinases (MMPs) in rotator cuff tears, a paucity of data exists correlating the clinical severity of the disease with the implicated MMP levels. The purpose of this study was to investigate and compare the levels of expression of MMP-1, -3, -9 and -13 in patients with rotator cuff tears. We hypothesized that patients with clinically worse symptoms as measured by a standardized pain and function scale would have a higher expression of MMPs.Rotator cuff specimens were obtained from 16 consecutive patients undergoing rotator cuff repair. Total protein was extracted from these specimens and quantified. Equalized total protein extracts were used for performing enzyme-linked immunosorbent assay for quantitative determination of MMP-1, -3, -9 and -13. Preoperatively, the University of California, Los Angeles (UCLA) Shoulder Rating Scale was administered to each patient. Statistical comparisons were performed using analysis of variance. The expression of MMP-13 was notably increased in the rotator cuff extracts of all patients (P=.02). In addition, MMP-13 levels showed a significant proportional correlation with the patient pain score as per their UCLA ratings (r=-0.5). Although higher MMP-9 levels were assayed, this was not statistically significant. Expression of MMP-1 and-3 was insignificant.Our data suggest a critical role for MMP-13 in rotator cuff tears; elevated levels are a possible indicator for an impending tear. Further studies with increased sample size are warranted to prove the possible use of MMP-13 as therapeutic targets that may be inhibited by anti-inflammatory agents to limit disease progression.

Metalloproteases and rotator cuff disease

The molecular changes occurring in rotator cuff tears are still unknown, but much attention has been paid to better understand the role of matrix metalloproteinases (MMP) in the development of tendinopathy. These are potent enzymes that, once activated, can completely degrade all components of the connective tissue, modify the extracellular matrix (ECM), and mediatethe development of painful tendinopathy and tendon rupture. To control the local activity of activated proteinases, the same cells produce tissue inhibitors of metalloproteinases (TIMP) that bind to the enzymes and prevent degradation. The balance between the activities of MMPs and TIMPs regulates tendon remodeling, whereas an imbalance produces a collagen dis-regulation and disturbances intendons. ADAMs (a disintegrin and metalloproteinase) are cell membrane-linked enzymes with proteolytic and cell signaling functions. ADAMTSs (ADAM with thrombospondin motifs) are secreted into the circulation, and constitute a heterogenous family of proteases with both anabolic and catabolic functions. Biologic modulation of endogenous MMP activity to basal levels may reduce pathologic tissue degradation and favorably influence healing after rotator cuff repair. Further studies are needed to better define the mechanism of action, and whether these new strategies are safe and effective in larger models.

Expression of matrix metalloproteinases 1, 3, and 9 in differing extents of tendon retraction in the torn rotator cuff

PURPOSE

Differing extents of tendon retraction are found in full-thickness rotator cuff tears. The pathophysiologic context of tendon degeneration and the extent of tendon retraction are unclear. Tendon integrity depends on the extracellular matrix, which is regulated by matrix metalloproteinases (MMP). It is unknown which enzymes play a role in tendon degeneration. The hypotheses are that (1) the expression of MMPs 1, 3, and 9 is altered in the torn rotator cuff when compared with healthy tendon samples; and (2) that there is a relationship between MMP expression and the extent of tendon retraction in the torn cuff.

METHODS

Rotator cuff tendon samples of 33 patients with full-thickness rotator cuff tears (Bateman grade III) were harvested during reconstructive surgery. Samples were dehydrated and paraffin-embedded. Immunohistologic determination of MMP 1, 3, and 9 expression was performed by staining sample slices with MMP antibody. The extent of tendon retraction was determined intraoperatively according to Patte's classification and patients were assigned to 4 groups (control group, and by tendon retraction grade Patte I-III). The control group consisted of six healthy tendon samples.

RESULTS

Expression of MMPs 1 and 9 was significantly higher in torn cuff samples than in healthy tendons whereas MMP 3 expression was significantly decreased (P < 0.05). MMP 9 expression significantly increased with rising extent of tendon retraction in the torn cuff (P < 0.05). No significant association was found between expression of MMPs 1 and 3 and the rising extent of tendon retraction by Patte's classification.

CONCLUSION

Elevated expression of MMPs 1 and 9 as well as decreased MMP 3 expression can be detected in torn rotator cuff tendon tissue. There is a significant association between the extent of tendon retraction and MMP 9 expression. The results of this study give evidence that early surgical treatment of small and partial-thickness rotator cuff tears is required.

Full-thickness supraspinatus tears are associated with more synovial inflammation and tissue degeneration than partial-thickness tears

BACKGROUND

The objective of this study was to determine whether the tear size of a supraspinatus tendon correlated with synovial inflammation and tendon degeneration in patients who underwent shoulder arthroscopy for rotator cuff repair. We hypothesized that increased synovial inflammation would correlate with greater tear size of the supraspinatus tendon at the time of surgery.

MATERIALS AND METHODS

Tissue from the synovium, bursa, torn supraspinatus tendon, and subscapularis tendon was obtained from patients during shoulder arthroscopy to evaluate the messenger RNA expression of proinflammatory cytokines, tissue remodeling, and angiogenesis factors in the tendon, bursa, and synovium. Additional tissue was fixed to determine histologic changes including inflammation, vascular ingrowth, and collagen organization.

RESULTS

Increased expression of interleukin 1β, interleukin 6, cyclooxygenase 2, matrix metalloproteinase (MMP) 9, and vascular endothelial growth factor was found in the synovium of patients with full-thickness tears versus partial-thickness tears (P < .05). In the supraspinatus tendon, increased expression of MMP-1, MMP-9, MMP-13, and vascular endothelial growth factor was found in the full-thickness group. The upregulation of these genes in the full-thickness group was consistent with enhanced synovial inflammation, greater vascular ingrowth, and the loss of collagen organization in both supraspinatus and subscapularis tendons as determined by histology.

CONCLUSION

Increased synovial inflammation and tissue degeneration correlate with the tear size of the supraspinatus tendon. A better understanding of the relationship between synovial inflammation and the progression of tendon degeneration can help in the design of novel and effective treatments to limit the advancement of rotator cuff disease and to improve their clinical outcomes.

Ciprofloxacin up-regulates tendon cells to express matrix metalloproteinase-2 with degradation of type I collagen

Ciprofloxacin-induced tendinopathy and tendon rupture have been previously described, principally affecting the Achilles tendon. This study was designed to investigate the effect of ciprofloxacin on expressions of matrix metalloproteinases (MMP)-2 and -9, tissue inhibitors of metalloproteinase (TIMP)-1 and -2 as well as type I collagen in tendon cells. Tendon cells intrinsic to rat Achilles tendon were treated with ciprofloxacin and then underwent MTT (tetrazolium) assay. Real-time reverse-transcription polymerase chain reaction (RT-PCR) and Western blot analysis were used, respectively, to evaluate the gene and protein expressions of type I collagen, and MMP-2. Gelatin zymography was used to evaluate the enzymatic activities of MMP-2 and -9. Reverse zymography was used to evaluate TIMP-1 and -2. Immunohistochemical staining for MMP-2 in ciprofloxacin-treated tendon explants was performed. Collagen degradation was evaluated by incubation of conditioned medium with collagen. The results revealed that ciprofloxacin up-regulated the expression of MMP-2 in tendon cells at the mRNA and protein levels. Immunohistochemistry also confirmed the increased expressions of MMP-2 in ciprofloxacin-treated tendon explants. The enzymatic activity of MMP-2 was up-regulated whereas that of MMP-9, TIMP-1 or TIMP-2 was unchanged. The amount of secreted type I collagen in the conditioned medium decreased and type I collagen was degraded after ciprofloxacin treatment. In conclusion, ciprofloxacin up-regulates the expressions of MMP-2 in tendon cells and thus degraded type I collagen. These findings suggest a possible mechanism of ciprofloxacin-associated tendinopathy.

The effect of matrix metalloproteinase inhibition on tendon-to-bone healing in a rotator cuff repair model

HYPOTHESIS

Recent studies have demonstrated a potentially critical role of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in the pathophysiology of rotator cuff tears. We hypothesize that local delivery of a MMP inhibitor after surgical repair of the rotator cuff will improve healing at the tendon-to-bone surface interface.

MATERIALS AND METHODS

Sixty-two male Sprague-Dawley rats underwent acute supraspinatus detachment and repair. In the control group (n=31), the supraspinatus was repaired to its anatomic footprint. In the experimental group (n=31), recombinant alpha-2-macroglobulin (A2M) protein, a universal MMP inhibitor, was applied at the tendon-bone interface with an identical surgical repair. Animals were sacrificed at 2 and 4 weeks for histomorphometry, immunohistochemistry, and biomechanical testing. Statistical comparisons were performed using unpaired t tests. Significance was set at P < .05.

RESULTS

Significantly greater fibrocartilage was seen at the healing enthesis in the A2M-treated specimens compared with controls at 2 weeks (P < .05). Significantly greater collagen organization was observed in the A2M-treated animals compared with controls at 4 weeks (P < .01). A significant reduction in collagen degradation was observed at both 2 and 4 weeks in the experimental group (P < .05). Biomechanical testing revealed no significant differences in stiffness or ultimate load-to-failure.

CONCLUSION

Local delivery of an MMP inhibitor is associated with distinct histologic differences at the tendon-to-bone interface after rotator cuff repair. Modulation of MMP activity after rotator cuff repair may offer a novel biologic pathway to augment tendon-to-bone healing after rotator cuff repair.

Biomechanical and biologic augmentation for the treatment of massive rotator cuff tears

Recent studies have reported that massive rotator cuff tears do not heal as predictably as, and may have diminished clinical outcomes compared with, smaller rotator cuff tears. An improved understanding of the biologic degeneration and the biomechanical alterations of massive rotator cuff tears should provide better strategies to optimize outcomes. The approach to patients with massive rotator cuff tears requires careful assessment of the patient and the extent of rotator cuff degeneration to determine the appropriate treatment. For a rotator cuff tear that is repairable, the goal is to produce a tension-free, anatomical repair that restores the footprint using soft tissue releases and various suturing techniques, including double-row, transosseous-equivalent suture bridges or the rip-stop stitch. For irreparable cuff tears, the surgeon may elect to proceed with 1 of 2 approaches: (1) palliative surgical treatment-that is, rotator cuff debridement, synovectomy, biceps tenotomy, tuberoplasty and/or nonanatomical repair with partial repair; or (2) salvage treatment with various tendon transfers. Even though the biomechanical constructs for rotator cuff repairs have been improved, the integrity of the repair still depends on biologic healing at the tendon-to-bone junction. There has been much interest in the development of a scaffold to bridge massive rotator cuff tears and adjuvant biologic modalities including growth factors and tenocyte-seeded scaffolds to augment tendon-to-bone healing. The treatment of rotator cuff disease has improved considerably, but massive rotator cuff tears continue to pose a challenging problem for orthopaedic surgeons.

Doxycycline-mediated inhibition of matrix metalloproteinases improves healing after rotator cuff repair

BACKGROUND

Recent studies demonstrate a potentially critical role of matrix metalloproteinases (MMPs) and their inhibitors in the pathophysiology of rotator cuff tears.

HYPOTHESIS

Doxycycline-mediated MMP inhibition after rotator cuff repair will improve tendon-to-bone healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Rats (n = 183) underwent acute detachment and repair of the supraspinatus tendon and the animals were divided into 4 groups: In controls (n = 66), the supraspinatus was repaired to its anatomical footprint. In experimental groups, an identical surgery was performed with doxycycline (130 mg/kg/d) administered orally at (1) preoperative day 1 (n = 66), (2) postoperative day (POD) 5 (n = 28), or (3) POD 14 (n = 23). Animals were sacrificed at 5 days, 8 days, 2 weeks, and 4 weeks. Tendon-bone interface was evaluated with histomorphometry. Enzyme-linked immunosorbent assay for local MMP-13 activity was performed at 8 days and 4 weeks. Biomechanical testing of the healing enthesis was performed at 8 days, 2 weeks, and 4 weeks. Serum doxycycline levels were measured at sacrifice. Statistical analysis was performed using unpaired t tests and 2-way analysis of variance (P < .05).

RESULTS

Serum doxycycline levels were significantly higher in all treated groups compared with controls (1830 +/- 835 vs 3 +/- 3 ng/mL, respectively; P < .001). Doxycycline-treated animals demonstrated greater metachromasia and improved collagen organization at the healing enthesis at POD 5 (P < .06), POD 8 (P < .03), and 2 weeks (P < .04). The MMP-13 activity was significantly reduced in doxycycline-treated compared with control animals at POD 8 (6740 +/- 2770 vs 10400 +/- 2930 relative fluorescent units [RFU], respectively; P < .02) but not at 4 weeks (3600 +/- 3280 vs 4530 +/- 2720 RFU, respectively). The healing enthesis of animals started on doxycycline preoperatively or at POD 5 had an increased load to failure compared to controls at 2 weeks (13.6 +/- 1.8 and 13.2 +/- 1.94 N vs 9.1 +/- 2.5 N, respectively; P < .01).

CONCLUSION/CLINICAL RELEVANCE

Modulation of MMP-13 activity after rotator cuff repair may offer a novel biological pathway to augment tendon-to-bone healing.

Correlations between biochemical markers in the synovial fluid and severity of rotator cuff disease

The role of biochemical factors in the onset and natural history of rotator cuff disease is not fully understood, but it is generally recognised that they could induce tendon damage in association with mechanical and vascular factors. In this study, 5 biochemical parameters were analysed (total protein concentration, matrix metalloproteinase (MMP)-2 or gelatinase A, MMP-9 or gelatinase B, type I collagen telopeptides, hyaluronic acid) in the synovial fluid (SF) aspirated from the gleno-humeral joint of 29 patients undergoing surgical therapy for rotator cuff lesions. Four different groups of patients were identified according to the severity of the lesion: partial tear of the rotator cuff, full thickness tear involving <or-1 tendon, full thickness tear involving >1 tendon and cuff tear arthropathy (CTA). The total SF protein concentration progressively increased with loss of integrity of the rotator cuff, reaching the highest levels in CTA. The absolute enzymatic activity of gelatinases was greater in full thickness tears than in partial tears, while it decreased in CTA. Conversely, the ratio between gelatinases and total protein content reached the highest level in partial tears and then progressively decreased. Collagen I telopeptides were significantly increased in full thickness tears and CTA, whereas the levels of hyaluronic acid decreased with worsening of rotator cuff disease. These findings support the hypothesis that gelatinases, which are involved in physiological tendon remodelling, intervene in the evolution of rotator cuff disease, too. Increased levels of type I collagen telopeptides give evidence that tendon tears are associated with an anatomic loss of tendon tissue and not with simple tendon retraction.

Rotator cuff repair fluid extravasation characteristics are influenced by repair technique

BACKGROUND

This study evaluates rotator cuff repair fluid extravasation characteristics for different rotator cuff repair techniques.

METHODS

Eight fresh-frozen cadaveric shoulders were dissected free of soft tissues, with the glenohumeral joint capsule and rotator cuff muscles being left intact. A custom fluid infusion device was used to deliver fluid at constant pressure into the glenohumeral joint. The shoulders were tested in conditions of (1) intact rotator cuff, (2) supraspinatus tear, (3) repaired supraspinatus tear with a single-row technique, and (4) repaired supraspinatus tear with a double-row suture bridge technique.

RESULTS

The volume per minute of saline solution extravasation for single-row repair and double-row suture bridge repair was 48.53 mL/min and 11.73 mL/min, respectively, at 2 psi; 73.3 _ 24.1 mL/min and 24.5 _ 19.7 mL/min, respectively, at 3 psi; and 95.2 _ 22.6 mL/min and 39.2 _ 23.8 mL/min, respectively, at 4 psi. There was a statistically significant greater fluid extravasation for the single-row repair compared with the double-row suture bridge repair at all 3 pressures tested (P < .05).

CONCLUSION

Single-row rotator cuff repair exposes the healing zone to greater extravasation of fluid compared with double-row suture bridge repair. Therefore, double-row repair potentially enhances rotator cuff healing.

LEVEL OF EVIDENCE

Controlled laboratory study.

Characterization of plasma gelsolin as a substrate for matrix metalloproteinases

We previously showed that plasma gelsolin, a major component of the extracellular actin scavenging system, is an matrix metalloproteinase (MMP)-14 substrate. Here we confirmed that plasma gelsolin is cleaved by MMP-14 at the plasma level, and found that it was most efficiently digested by MMP-3 followed by MMP-2, MMP-1, MMP-14, and MMP-9, in that order. Plasma gelsolin (90 kDa) was cut into several fragments of 43-48 kDa by MMP-3. The MMP-3 cleavage sites in plasma gelsolin were determined by labeling the C termini generated by in-gel digestion with 50% H2 18O combined with peptide mass mapping, and sequencing of the N-terminal amino acids. Plasma gelsolin was cleaved at Asn416-Val417, Ser51-Met52, and Ala435-Gln436. Proteolytic cleavage by MMP-3 resulted in considerable loss of its actin filament-depolymerizing activity. This suggests that MMPs weaken the extracellular actin-scavenging system by cleaving plasma gelsolin and may, therefore, be involved in pathological conditions induced by extracellular actin, such as endothelial injury, respiratory distress syndrome, hepatic necrosis, and septic shock.

Gene expression and matrix turnover in overused and damaged tendons

Chronic, painful conditions affecting tendons, frequently known as tendinopathy, are very common types of sporting injury. The tendon extracellular matrix is substantially altered in tendinopathy, and these changes are thought to precede and underlie the clinical condition. The tendon cell response to repeated minor injuries or "overuse" is thought to be a major factor in the development of tendinopathy. Changes in matrix turnover may also be effected by the cellular response to physical load, altering the balance of matrix turnover and changing the structure and composition of the tendon. Matrix turnover is relatively high in tendons exposed to high mechanical demands, such as the supraspinatus and Achilles, and this is thought to represent either a repair or tissue maintenance function. Metalloproteinases are a large family of enzymes capable of degrading all of the tendon matrix components, and these are thought to play a major role in the degradation of matrix during development, adaptation and repair. It is proposed that some metalloproteinase enzymes are required for the health of the tendon, and others may be damaging, leading to degeneration of the tissue. Further research is required to investigate how these enzyme activities are regulated in tendon and altered in tendinopathy. A profile of all the metalloproteinases expressed and active in healthy and degenerate tendon is required and may lead to the development of new drug therapies for these common and debilitating sports injuries.

Multivariate analysis of biochemical markers in synovial fluid from the shoulder joint for diagnosis of rotator cuff tears

Multivariate discriminant analysis allowed definition of cytokine, matrix metalloproteinases (MMP), and tissue inhibitors of metalloproteinases (TIMP) levels in synovial fluid (SF) of patients with rotator cuff tears and other shoulder lesions. We analyzed SF aspirated from the glenohumeral joints of 17 patients with rotator cuff tears; SF from nine patients with other shoulder lesions was used to characterize a non-rotator-cuff-tear (NRCT) group. Discriminant analysis demonstrated statistically significant differences in (1) the determination of whether rotator cuff tear patients are separable from the NRCT group using the influential functions, the most influential of which were interleukin 1-beta, MMP-2, and MMP-13, and (2) the assessment of whether full-thickness rotator cuff tears are distinguishable from partial tears using identical influential functions. The most influential function in the latter analysis was MMP-13. Both interleukin 1-beta and MMP-13 might be biochemical markers of impending rotator cuff tears.