Inflammation in Tendon Disorders

Physical fitness in adolescent patients with familial Mediterranean fever

INTRODUCTION

Familial Mediterranean fever (FMF) is the most frequent monogenic auto-inflammatory disease worldwide responsible for episodes of fever, serositis and musculoskeletal symptoms. Inflammatory attacks are responsible for sedentary behavior and FMF patients may be at increased cardiovascular risk. Cardiorespiratory Fitness (CRF) and physical capacities during adolescence are associated with cardiovascular mortality in adulthood. In this study, we aimed to describe the physical fitness of FMF adolescents.

METHODS

A monocentric retrospective study at the Versailles Hospital between January 2020 and June 2023. All FMF patients over 14-year-old who had completed a routine physical test were included. Clinical and physical data including results of the 6-minute walking test, timed unipedal stance test, Ruffier-Dickson index, 30-seconds chair-stand test and sit-and-reach test were extracted from medical records. Results were compared with previously published normative reference values and criterion-referenced standards for healthy subjects.

RESULTS

Eighteen FMF patients (12 girls, 6 boys) were included. The median age was 16 years old [14-18]. Clinical history included joint symptoms (n = 11), chest pleuritis (n = 8), and leg pain (n = 11). Estimated VO2max was below the recommended thresholds in 13 patients, which predicts cardiovascular risk. Cardiovascular adaptation was poor in 11 patients. Low VO2max was associated with CRP > 5 mg/l on test day and history of joint symptoms.

CONCLUSION

FMF patients displayed altered physical capacities compared to normative values of healthy subjects. History of musculoskeletal pain, systemic inflammation and sedentary behavior may participate in impaired physical abilities and promote cardiovascular diseases in adulthood. Specific exercise programs could benefit patients for disease control and cardiovascular risk reduction.

Anti-Inflammatory and Antioxidant Properties of a New Mixture of Vitamin C, Collagen Peptides, Resveratrol, and Astaxanthin in Tenocytes: Molecular Basis for Future Applications in Tendinopathies

Tendinopathy is one of the most frequent musculoskeletal disorders characterized by sustained tissue inflammation and oxidative stress, accompanied by extracellular matrix remodeling. Patients suffering from this pathology frequently experience pain, swelling, stiffness, and muscle weakness. Current pharmacological interventions are based on nonsteroidal anti-inflammatory drugs; however, the effectiveness of these strategies remains ambiguous. Accumulating evidence supports that oral supplementation of natural compounds can provide preventive, and possibly curative, effects. Vitamin C (Vit C), collagen peptides (Coll), resveratrol (Res), and astaxanthin (Asx) were reported to be endowed with potential beneficial effects based on their anti-inflammatory and antioxidant activities. Here, we analyzed the efficacy of a novel combination of these compounds (Mix) in counteracting proinflammatory (IL-1β) and prooxidant (H2O2) stimuli in human tenocytes. We demonstrated that Mix significantly impairs IL-6-induced IL-1β secretion, NF-κB nuclear translocation, and MMP-2 production; notably, a synergistic effect of Mix over the single compounds could be observed. Moreover, Mix was able to significantly counteract H2O2-triggered ROS production. Together, these results point out that Mix, a novel combination of Vit C, Coll, Resv, and Asx, significantly impairs proinflammatory and prooxidant stimuli in tenocytes, mechanisms that contribute to the onset of tendinopathies.

Recent advances in tendon tissue engineering strategy

Tendon injuries often result in significant pain and disability and impose severe clinical and financial burdens on our society. Despite considerable achievements in the field of regenerative medicine in the past several decades, effective treatments remain a challenge due to the limited natural healing capacity of tendons caused by poor cell density and vascularization. The development of tissue engineering has provided more promising results in regenerating tendon-like tissues with compositional, structural and functional characteristics comparable to those of native tendon tissues. Tissue engineering is the discipline of regenerative medicine that aims to restore the physiological functions of tissues by using a combination of cells and materials, as well as suitable biochemical and physicochemical factors. In this review, following a discussion of tendon structure, injury and healing, we aim to elucidate the current strategies (biomaterials, scaffold fabrication techniques, cells, biological adjuncts, mechanical loading and bioreactors, and the role of macrophage polarization in tendon regeneration), challenges and future directions in the field of tendon tissue engineering.

Modulation of Inflammation by Plant-Derived Nutraceuticals in Tendinitis

Tendinitis (tendinopathy) is a pro-inflammatory and painful tendon disease commonly linked with mechanical overuse and associated injuries, drug abuse, and lifestyle factors (including poor diet and physical inactivity) that causes significant healthcare expenditures due to its high incidence. Nuclear factor kappa B (NF-κB) is one of the major pro-inflammatory transcription factors, along with other inflammation signaling pathways, triggered by a variety of stimuli, including cytokines, endotoxins, physical and chemical stressors, hypoxia, and other pro-inflammatory factors. Their activation is known to regulate the expression of a multitude of genes involved in inflammation, degradation, and cell death. The pathogenesis of tendinitis is still poorly understood, whereas efficient and sustainable treatment is missing. Targeting drug suppression of the key inflammatory regulators represents an effective strategy for tendinitis therapy, but requires a comprehensive understanding of their principles of action. Conventional monotherapies are often ineffective and associated with severe side effects in patients. Therefore, agents that modulate multiple cellular targets represent therapeutic treatment potential. Plant-derived nutraceuticals have been shown to act as multi-targeting agents against tendinitis via various anti-oxidant and anti-inflammatory mechanisms, whereat they were able to specifically modulate numerous signaling pathways, including NF-κB, p38/MAPK, JNK/STAT3, and PI3K/Akt, thus down-regulating inflammatory processes. This review discusses the utility of herbal nutraceuticals that have demonstrated safety and tolerability as anti-inflammatory agents for the prevention and treatment of tendinitis through the suppression of catabolic signaling pathways. Limitations associated with the use of nutraceuticals are also described.

Allergy-induced systemic inflammation impairs tendon quality

Background

Treatment of degenerating tendons still presents a major challenge, since the aetiology of tendinopathies remains poorly understood. Besides mechanical overuse, further known predisposing factors include rheumatoid arthritis, diabetes, obesity or smoking all of which combine with a systemic inflammation.

Methods

To determine whether the systemic inflammation accompanying these conditions contributes to the onset of tendinopathy, we studied the effect of a systemic inflammation induced by an allergic episode on tendon properties. To this end, we induced an allergic response in mice by exposing them to a timothy grass pollen allergen and subsequently analysed both their flexor and Achilles tendons. Additionally, we analysed data from a health survey comprising data from more than 10.000 persons for an association between the occurrence of an allergy and tendinopathy.

Findings

Biomechanical testing and histological analysis revealed that tendons from allergic mice not only showed a significant reduction of both elastic modulus and tensile stress, but also alterations of the tendon matrix. Moreover, treatment of 3D tendon-like constructs with sera from allergic mice resulted in a matrix-remodelling expression profile and the expression of macrophage-associated markers and matrix metalloproteinase 2 (MMP2) was increased in allergic Achilles tendons. Data from the human health study revealed that persons suffering from an allergy have an increased propensity to develop a tendinopathy.

Interpretation

Our study demonstrates that the presence of a systemic inflammation accompanying an allergic condition negatively impacts on tendon structure and function.

Funding

This study was financially supported by the Fund for the Advancement of Scientific Research at Paracelsus Medical University (PMU-FFF E-15/22/115-LEK), by the Land Salzburg, the Salzburger Landeskliniken (SALK, the Health Care Provider of the University Hospitals Landeskrankenhaus and Christian Doppler Klinik), the Paracelsus Medical University, Salzburg and by unrestricted grants from Bayer, AstraZeneca, Sanofi-Aventis, Boehringer-Ingelheim.

The Effect of Age and Intrinsic Aerobic Exercise Capacity on the Expression of Inflammation and Remodeling Markers in Rat Achilles Tendons

Old age, adiposity, and metabolic disorders are known as risk factors for chronic tendinopathy, which is a common problem in both athletes and the general population. However, the importance of these influencing factors has not yet been well understood. This study investigated alterations in gene expression and histology of Achilles tendons of young (10 weeks) and old (100 weeks) rats bred for low (low capacity runners, LCR) and high (high capacity runners, HCR) intrinsic aerobic exercise capacity. In this rat model, LCR displayed a phenotype of reduced exercise capacity, higher body weight, and metabolic dysfunctions compared to HCR. We hypothesized that the risk factors for tendinopathy in old LCR could lead to more pronounced impairments in Achilles tendon tissue. In quantitative real-time PCR (qPCR), age-related downregulation of tenocyte markers e.g., tenomodulin, genes related to matrix modeling and remodeling (e.g., collagens, elastin, biglycan, fibronectin, tenascin C) as well as transforming growth factor beta 3 (Tgfb3) have been detected. Inflammation marker cyclooxygenase 2 (Cox2) was downregulated in old rats, while microsomal prostaglandin E synthase 2 (Ptges2) was upregulated in old HCR and old LCR. In all groups, interleukin 6 (Il6), interleukin 1 beta (Il1b), and tumor necrosis factor alpha (Tnfa) showed no significant alteration. In histological evaluation, tendons of old rats had fewer and more elongated tenocyte nuclei than young rats. Even though a higher content of glycosaminoglycans, a sign of degeneration, was found in old HCR and LCR, no further signs of tendinopathy were detectable in tendons of old rats by histological evaluation. Low intrinsic aerobic exercise capacity and the associated phenotype did not show significant effects on gene expression and tendon histology. These findings indicate that aging seems to play a prominent role in molecular and structural alterations of Achilles tendon tissue and suggests that other risk factors associated with intrinsic aerobic exercise capacity are less influential in this rat model.

Acute-Onset Achilles Tendon Pain and Swelling Treated with an Amniotic Fluid-Derived Allograft: A Case Study

BACKGROUND

Tendinopathies are common musculoskeletal disorders that often develop because of chronic loading and failed healing. Tendinopathy related to systemic inflammation has been less extensively examined. Furthermore, although the use of biological agents to treat tendinopathies continues to gain popularity, the use of amniotic fluid-derived allografts in outpatient settings to resolve tendinopathies requires further evaluation.

METHODS

The focus of this case report is a 25-year-old man who presented for a second opinion, having been diagnosed with Haglund deformity and Achilles tendinopathy. At the time of presentation, he complained of 10 of 10 pain to the right Achilles tendon. He was treating the injury conservatively with intermittent use of a controlled ankle motion boot and working with physiotherapy for approximately 5 months before presentation. Diagnostic ultrasound along with magnetic resonance imaging indicated distal thickening of the Achilles tendon, substantial fluid and edema in the Kager fat pad, and retrocalcaneal erosions with bursitis. Conservative management did not resolve the symptoms. As an alternative to surgery, the patient elected to undergo an Achilles tendon injection of an amniotic fluid-derived allograft. Before and after the initial injection, a microdialysis catheter was inserted into the Achilles peritendinous space to sample local levels of extracellular matrix enzymes and growth factors important for tendon remodeling. The patient received considerable relief with the initial injection, but did not return to full strength. Over the subsequent 8 weeks, the patient was followed closely and was able to return to daily activities with minimal pain. He was not able to return to a more active lifestyle without further Achilles pain, so a second amniotic fluid-derived allograft injection was performed 8 weeks after the initial injection.

RESULTS

Injection of the initial allograft resulted in significant improvement, but not complete resolution of pain and swelling. Microdialysis findings suggested a reduction in peritendinous levels of the cytokine interlukin-6 in addition to changes in extracellular matrix regulatory enzymes. After 8 weeks of additional conservative therapy and a second injection, no further improvement in pain was noted.

CONCLUSIONS

Based on the clinical improvement of symptoms in this individual and the changes seen with microdialysis methodology, the authors find the use of amniotic fluid-derived allograft injection for treatment of Achilles pain in this patient to be a viable treatment. Additional comorbidities of systemic inflammatory polyarthritis and possible seronegative disease were addressed after rheumatology consultation with a variety of medications that provided the patient additional relief of his symptoms. The patient ultimately moved and was lost to further follow-up.

A2A adenosine receptors are involved in the reparative response of tendon cells to pulsed electromagnetic fields

Tendinopathy is a degenerative disease in which inflammatory mediators have been found to be sometimes present. The interaction between inflammation and matrix remodeling in human tendon cells (TCs) is supported by the secretion of cytokines such as IL-1β, IL-6 and IL-33. In this context, it has been demonstrated that pulsed electromagnetic fields (PEMFs) were able to reduce inflammation and promote tendon marker synthesis. The aim of this study was to evaluate the anabolic and anti-inflammatory PEMF-mediated response on TCs in an in vitro model of inflammation. Moreover, since PEMFs enhance the anti-inflammatory efficacy of adenosine through the adenosine receptors (ARs), the study also focused on the role of A_2AARs. Human TCs were exposed to PEMFs for 48 hours. After stimulation, A_2AAR saturation binding experiments were performed. Along with 48 hours PEMF stimulation, TCs were treated with IL-1β and A_2AAR agonist CGS-21680. IL-1Ra, IL-6, IL-8, IL-10, IL-33, VEGF, TGF-β1, PGE₂ release and SCX, COL1A1, COL3A1, ADORA2A expression were quantified. PEMFs exerted A_2AAR modulation on TCs and promoted COL3A1 upregulation and IL-33 secretion. In presence of IL-1β, TCs showed an upregulation of ADORA2A, SCX and COL3A1 expression and an increase of IL-6, IL-8, PGE₂ and VEGF secretion. After PEMF and IL-1β exposure, IL-33 was upregulated, whereas IL-6, PGE₂ and ADORA2A were downregulated. These findings demonstrated that A_2AARs have a role in the promotion of the TC anabolic/reparative response to PEMFs and to IL-1β.

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.

Updates in Tendinopathy Treatment Options

Tendinopathy is a common but disabling condition. The term describes a complex, multifaceted pathology of the tendon characterized by pain, decreased function, and reduced exercise tolerance. Tendinopathy accounts for up to 30% of general practice musculoskeletal consultations. Advances in understanding the disease process include inflammation as part of the early tendinopathy process. Once thought to not contribute to the early process of tendon degeneration, this hypothesis has been refuted. This allows guidance in conservative treatment. However, when conservative treatments fail, there are minimally invasive injections and ultrasonic debridement techniques that offer an intermediate treatment step with low reported morbidity.

The roles of inflammatory mediators and immunocytes in tendinopathy

Tendinopathy is a common disease of the musculoskeletal system, particularly in athletes and sports amateurs. In this review, we will present evidence for the critical role of inflammatory mediators and immunocytes in the pathogenesis of tendinopathy and the efficacy of current antiinflammatory therapy and regenerative medicine in the clinic. We hereby propose a hypothesis that in addition to pulling force there may be compressive forces being exerted on the tendon during physical activities, which may initiate the onset of tendinopathy. We performed literature searches on MEDLINE from the inception of this review to February 2018. No language restrictions were imposed. The search terms were as follows: ("Tendinopathy"[Mesh] OR "Tendon Injuries"[Mesh] OR "Tendinitis"[Mesh] OR "Tendon"[Mesh]) AND (Inflammation OR "Inflammatory mediator*" OR Immunocyte*) OR ("anti inflammatory*" OR "regenerative medicine"). Inclusion criteria included articles that were original and reliable, with the main contents being highly relevant to our review. Exclusion criteria included articles that were not available online or have not been published. We scanned the abstract of these articles first. This was then followed by a careful screening of the articles which might be suitable for our review. Finally, 84 articles were selected as references. This review article is written in the narrative form. The translational potential of this article: Understanding the mechanisms of inflammation and existing antiinflammatory and regenerative therapies is key to the development of therapeutic strategies in tendinopathy.