Differences in tumor necrosis factor (TNF)alpha and TNF receptor-1-mediated intracellular signaling factors in normal, inflamed and scar-formed horse tendons

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

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

Histoarchitecture of the fibrillary matrix of human fetal posterior tibial tendons

Adult tendons are highly differentiated. In mature individuals, tendon healing after an injury occurs through fibrotic tissue formation. Understanding the intrinsic reparative properties of fetal tendons would help to understand the maturation tissue process and tendon tissue repair. The present study evaluated the evolution of histoarchitecture, cellularity and the distribution of collagens I, III and V in the posterior tibial tendon in human fetuses at different gestational ages. Morphological profiles were assessed in nine fresh spontaneously aborted fetuses (Group I: five fetuses aged between 22 and 28 weeks of gestation; Group II: four fetuses aged between 32 and 38 weeks of gestation), characterized by a combination of histology, fluorescence and immunohistochemistry. In Group I, the posterior tibial tendon showed statistically significant greater cellularity and presence of collagen III and V than in Group II tendon, which showed a predominance of collagenous I and a better organization of the extracellular matrix compared with Group I tendons. In addition, a statistically significant higher rate of CD90, a marker of mesenchymal cells, was found in Group I tendons. In fetuses with gestational age between 22 and 28 weeks, the posterior tibialis tendons showed a thin and disorganized fibrillar structure, with an increase in collagen III and V fibers and mesenchymal cells. In the posterior tibialis tendons of fetuses with gestational age between 32 and 38 weeks, the fibrillar structure was thicker with a statistically significant increase in type I collagen and decreased cellularity.

A Global Phosphorylation Atlas of Proteins Within Pathological Site of Rotator Cuff Tendinopathy

Rotator cuff tendinopathy (RCT) is the most common cause of shoulder pain, therefore posing an important clinical problem. Understanding the mechanism and biochemical changes of RCT would be of crucial importance and pave the path to targeting novel and effective therapeutic strategies in translational perspectives and clinical practices. Phosphorylation, as one of the most important and well-studied post-translational modifications, is tightly associated with protein activity and protein functional regulation. Here in this study, we generated a global protein phosphorylation atlas within the pathological site of human RCT patients. By using Tandem Mass Tag (TMT) labeling combined with mass spectrometry, an average of 7,741 phosphorylation sites (p-sites) and 3,026 proteins were identified. Compared with their normal counterparts, 1,668 p-sites in 706 proteins were identified as upregulated, while 73 p-sites in 57 proteins were downregulated. GO enrichment analyses have shown that majority of proteins with upregulated p-sites functioned in neutrophil-mediated immunity whereas downregulated p-sites are mainly involved in muscle development. Furthermore, pathway analysis identified NF-κB–related TNF signaling pathway and protein kinase C alpha type (PKCα)–related Wnt signaling pathway were associated with RCT pathology. At last, a weighted kinase-site phosphorylation network was built to identify potentially core kinase, from which serine/threonine-protein kinase 39 (STLK3) and mammalian STE20-like protein kinase 1 (MST1) were proposed to be positively correlated with the activation of Wnt pathway.

Species variations in tenocytes' response to inflammation require careful selection of animal models for tendon research

For research on tendon injury, many different animal models are utilized; however, the extent to which these species simulate the clinical condition and disease pathophysiology has not yet been critically evaluated. Considering the importance of inflammation in tendon disease, this study compared the cellular and molecular features of inflammation in tenocytes of humans and four common model species (mouse, rat, sheep, and horse). While mouse and rat tenocytes most closely equalled human tenocytes’ low proliferation capacity and the negligible effect of inflammation on proliferation, the wound closure speed of humans was best approximated by rats and horses. The overall gene expression of human tenocytes was most similar to mice under healthy, to horses under transient and to sheep under constant inflammatory conditions. Humans were best matched by mice and horses in their tendon marker and collagen expression, by horses in extracellular matrix remodelling genes, and by rats in inflammatory mediators. As no single animal model perfectly replicates the clinical condition and sufficiently emulates human tenocytes, fit-for-purpose selection of the model species for each specific research question and combination of data from multiple species will be essential to optimize translational predictive validity.

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

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

Equine suspensory ligament and tendon explants cultured with platelet-rich gel supernatants release different anti-inflammatory and anabolic mediators

The aim of this study was to evaluate the release of pro- and anti-inflammatory as well as anabolic mediators stimulated by a leukocyte-reduced platelet-rich gel supernatant (Lr-PRGS) and a leukocyte-reduced plasma supernatant (Lr-PL) at two concentrations (25 and 50%) on normal equine suspensory ligament explants (SLEs) and tendon explants (TEs). SLEs and TEs from six horses were independently incubated for 48 h with Lr-PRGS and Lr-PL at concentrations of 25 and 50%, respectively. Samples were collected from the incubated tissues at 1 h and 48 h, which were employed for ELISA determination of interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α),  IL-4, IL-1 receptor antagonist (IL-1ra), platelet-derived growth factor isoform BB (PDGF-BB), transforming growth factor beta-1 (TGF-β₁, and hyaluronic acid (HA). Overall, 50% Lr-PRGS induced significantly less IL-1β release than the other hemoderivatives in both tissues. At 48 h, both Lr-PRGS and 25% Lr-PL induced significantly higher TNF-α concentrations in SLEs when compared to TEs, whereas both Lr-PRGS concentrations induced significantly higher IL-4 concentrations in SLEs in comparison to TEs. IL-1ra release was not different between tissues. However, this cytokine was significantly higher in tissue explants cultured with both Lr-PRGS concentrations. HA concentration was lower in tissue explants cultured with all hemoderivatives at two concentrations when compared to the control group. The positive effects observed for ligaments and tendons treated with Lr-PRGS may be mediated by the inhibition of IL-1β release of and increased release of IL-4 and IL-1ra. Furthermore, PDGF-BB could be a polypeptide responsible for mediating the release of anti-inflammatory cytokines in SLEs and TEs incubated with Lr-PRGS.

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.

Cytokines in tendon disease: A Systematic Review

OBJECTIVES

Emerging evidence indicates that tendon disease is an active process with inflammation that is critical to disease onset and progression. However, the key cytokines responsible for driving and sustaining inflammation have not been identified.

METHODS

We performed a systematic review of the literature using MEDLINE (U.S. National Library of Medicine, Bethesda, Maryland) in March 2017. Studies reporting the expression of interleukins (ILs), tumour necrosis factor alpha (TNF-α) and interferon gamma in diseased human tendon tissues, and animal models of tendon injury or exercise in comparison with healthy control tissues were included.

RESULTS

IL-1β, IL-6, IL-10, and TNF-α are the cytokines that have been most frequently investigated. In clinical samples of tendinopathy and tendon tears, the expression of TNF-α tended not to change but IL-6 increased in tears. Healthy human tendons showed increased IL-6 expression after exercise; however, IL-10 remained unchanged. Animal tendon injury models showed that IL-1β, IL-6, and TNF-α tend to increase from the early phase of tendon healing. In animal exercise studies, IL-1β expression showed a tendency to increase at the early stage after exercise, but IL-10 expression remained unchanged with exercise.

CONCLUSIONS

This review highlights the roles of IL-1β, IL-6, IL-10, and TNF-α in the development of tendon disease, during tendon healing, and in response to exercise. However, there is evidence accumulating that suggests that other cytokines are also contributing to tendon inflammatory processes. Further work with hypothesis-free methods is warranted in order to identify the key cytokines, with subsequent mechanistic and interaction studies to elucidate their roles in tendon disease development.Cite this article: W. Morita, S. G. Dakin, S. J. B. Snelling, A. J. Carr. Cytokines in tendon disease: A Systematic Review. Bone Joint Res 2017;6:656-664. DOI: 10.1302/2046-3758.612.BJR-2017-0112.R1.

Effects of Tumor Necrosis Factor Inhibitor on Stress-Shielded Tendons

Mechanical stress plays an important role in preserving the integrity of bone and ligament. Stress shielding reduces mechanical load on bone or tendons, resulting in tissue degradation. Previous studies showed that deterioration of the tendon structure during stress shielding is associated with elevated expression of tumor necrosis factor (TNF)-α. This study examined the therapeutic potential of the TNF inhibitor etanercept in preventing morphologic deterioration of the Achilles tendon after stress shielding. Rats (N=48) were exposed to stress shielding of the left Achilles tendon and treated with etanercept or phosphate-buffered saline for 2 or 4 weeks. The right Achilles tendons were used as controls. After 2 or 4 weeks, stress-shielded tendons appeared less smooth than control tendons, and the stress-shielded tendons formed adhesions with surrounding tissues. Transmission electron microscopy also showed disarray of the collagen fibrils and a significant increase in the number of small-diameter collagen fibrils. These changes were associated with increased expression of TNF-α, matrix metalloproteinase (MMP)-13, MMP-3, collagen I, and collagen III. Treatment with 2 weeks of etanercept injection reduced morphologic changes in collagen organization and structure induced by stress shielding. Etanercept treatment also attenuated upregulation of MMP-13, MMP-3, and collagen III levels. However, no significant difference was observed between the etanercept group and the phosphate-buffered saline group after 4 weeks of treatment. The current findings show that TNF-α inhibition can protect against the early stages of tendon tissue remodeling induced by stress shielding, but additional interventions may be necessary to prevent tendon degeneration with long-term stress shielding. [Orthopedics. 2017; 40(1):49-55.].

The low level laser therapy (LLLT) operating in 660 nm reduce gene expression of inflammatory mediators in the experimental model of collagenase-induced rat tendinitis

Tendinopathy is a common disease with a variety of treatments and therapies. Laser therapy appears as an alternative treatment. Here, we investigate the effects of laser irradiation in an experimental model of tendinitis induced by collagenase injection on rats' Achilles tendon, verifying its action in important inflammatory markers. Male Wistar rats were used and divided into five groups: control saline (C), non-treated tendinitis (NT) and tendinitis treated with sodium diclofenac (D) or laser (1 J) and (3 J). The tendinitis was induced by collagenase (100 μg/tendon) on the Achilles tendon, which was removed for further analyses. The gene expression for COX-2; TNF-α; IL-6; and IL-10 (RT-PCR) was measured. The laser irradiation (660 nm, 100 mW, 3 J) used in the treatment of the tendinitis induced by collagenase in Achilles tendon in rats was effective in the reduction of important pro-inflammatory markers such as IL-6 and TNF-α, becoming a promising tool for the treatment of tendon diseases.

A review of recent advances and current hypotheses on the pathogenesis of acute laminitis

With the increasing number of studies being published on the different experimental models used to induce and study acute laminitis, the pathophysiological events associated with these various models (i.e. starch overload, oligofructose overload, black walnut extract and hyperinsulinaemia) can be compared more realistically. Within this review, the mechanisms for metabolic vs. inflammatory laminitis are discussed, and the question of how pasture laminitis may fit into any of the proposed mechanisms is addressed.

Tendon structure changes after maximal exercise in the Thoroughbred horse: use of ultrasound tissue characterisation to detect in vivo tendon response

Investigations into the response of the superficial digital flexor tendon (SDFT) of the Thoroughbred horse to mechanical stimuli have been limited to in vitro cell culture studies focused primarily on gene expression of critical matrix proteins. It is uncertain how well in vitro outcomes translate to the tendon of the horse during exercise. The current study examined changes in tendon structure in response to maximal exercise using ultrasound tissue characterisation (UTC) to scan the SDFT prior to and after competitive racing. UTC uses contiguous transverse ultrasound images to assess the dynamics of the echopattern, which has a close relationship with changes in the 3-D ultra-structure of the tendon. Using UTC, it was possible to detect subtle changes in the dynamics of the echopattern, with a reduction in pixels that represent aligned and integer collagen tendon bundles on days 1 and 2 post-race when compared to pre-race (P<0.05). The echopattern of these tendons returned to baseline on day 3. This change in echopattern was not seen in control horses. It was concluded that short-term changes in the SDFT following maximal exercise could be detected using UTC.

The role of pro-inflammatory and immunoregulatory cytokines in tendon healing and rupture: new insights

Owing to limited self-healing capacity, tendon ruptures and healing remain major orthopedic challenges. Increasing evidence suggests that post-traumatic inflammatory responses, and hence, cytokines are involved in both cases, and also in tendon exercise and homeostasis. This review summarizes interrelations known between the cytokines interleukin (IL)-1β, tumor necrosis factor (TNF)α, IL-6 and vascular endothelial growth factor (VEGF) in tendon to assess their role in tendon damage and healing. Exogenic cytokine sources are blood-derived leukocytes that immigrate in damaged tendon. Endogenous expression of IL-1β, TNFα, IL-6, IL-10 and VEGF was demonstrated in tendon-derived cells. As tendon is a highly mechanosensitive tissue, cytokine homeostasis and cell survival underlie an intimate balance between adequate biomechanical stimuli and disturbance through load deprivation and overload. Multiple interrelations between cytokines and tendon extracellular matrix (ECM) synthesis, catabolic mediators e.g. matrix-degrading enzymes, inflammatory and angiogenic factors (COX-2, PGE2, VEGF, NO) and cytoskeleton assembly are evident. Pro-inflammatory cytokines affect ECM homeostasis, accelerate remodeling, amplify biomechanical adaptiveness and promote tenocyte apoptosis. This multifaceted interplay might both contribute to and interfere with healing. Much work must be undertaken to understand the particular interrelation of these inflammatory and regulatory mediators in ruptured tendon and healing, which has relevance for the development of novel immunoregulatory therapeutic strategies.

Low-level laser therapy (LLLT; 780 nm) acts differently on mRNA expression of anti- and pro-inflammatory mediators in an experimental model of collagenase-induced tendinitis in rat

Low-level laser therapy (LLLT) has been found to produce anti-inflammatory effects in a variety of disorders. Tendinopathies are directly related to unbalance in expression of pro- and anti-inflammatory cytokines which are responsible by degeneration process of tendinocytes. In the current study, we decided to investigate if LLLT could reduce mRNA expression for TNF-α, IL-1β, IL-6, TGF-β cytokines, and COX-2 enzyme. Forty-two male Wistar rats were divided randomly in seven groups, and tendinitis was induced with a collagenase intratendinea injection. The mRNA expression was evaluated by real-time PCR in 7th and 14th days after tendinitis. LLLT irradiation with wavelength of 780 nm required for 75 s with a dose of 7.7 J/cm(2) was administered in distinct moments: 12 h and 7 days post tendinitis. At the 12 h after tendinitis, the animals were irradiated once in intercalate days until the 7th or 14th day in and them the animals were killed, respectively. In other series, 7 days after tendinitis, the animals were irradiated once in intercalated days until the 14th day and then the animals were killed. LLLT in both acute and chronic phases decreased IL-6, COX-2, and TGF-β expression after tendinitis, respectively, when compared to tendinitis groups: IL-6, COX-2, and TGF-β. The LLLT not altered IL-1β expression in any time, but reduced the TNF-α expression; however, only at chronic phase. We conclude that LLLT administered with this protocol reduces one of features of tendinopathies that is mRNA expression for pro-inflammatory mediators.

Effect of pro-inflammatory and immunoregulatory cytokines on human tenocytes

Tendon injury induces a local inflammatory response, characterized by the induction of pro-inflammatory cytokines. The aim of the present study was to analyze the effects of TNFalpha, IL-6 and IL-10 on key parameters of tendon homeostasis. Cultured primary human tenocytes were treated with the recombinant cytokines IL-6, IL-10, TNFalpha, or combinations of TNFalpha with IL-6 and IL-10 (10 ng/mL, 6, 24 h). Expression of type I collagen, elastin, MMP-1, TNFalpha, IL-1beta, IL-6, IL-10, and suppressors of cytokine signaling (SOCS1, 3) was analyzed with the use of RTD-PCR, immunocytochemistry, and Western blot analysis. In response to TNFalpha, tenocytes reduced their type I collagen deposition but increased their elastin gene expression and highly upregulated their expression for MMP-1, pro-inflammatory (TNFalpha, IL-1beta) and immunoregulatory (IL-6, IL-10) cytokines. TNFalpha stimulation augmented SOCS1, whereas SOCS3 expression in tenocytes was also induced by IL-6. The treatment of tenocytes with IL-6 and IL-10 had no effect on cytokine expression. Neither IL-6 nor IL-10 modulated the observed effects of TNFalpha significantly. These results indicate that TNFalpha strongly activates the tenocytes to amplify their own TNFalpha expression and, subsequently, that of other regulatory cytokines and matrix degrading enzymes. However, the impact of IL-6 and IL-10 on tenocytes remains unclear.

Radial shock waves effectively introduced NF-kappa B decoy into rat achilles tendon cells in vitro

The purpose of this study was to test if radial shock waves could enhance the introduction of nuclear factor-kappa B (NF-kappaB) decoy oligodeoxynucleotides, which is reported to markedly inhibit NF-kappaB activation and suppress pro-inflammatory cytokine gene expression, using rat Achilles tendon cells. In the presence of NF-kappaB decoy labeled with or without fluorescein isothiocyanate (FITC) in culture media, radial shock waves were applied to the tendon cells in variable conditions and cultivated for 24 h. The transfection rate was assessed by counting FITC-positive cells, and IL-1-induced NF-kappaB activation in the cells was assessed. Radial shock waves significantly enhanced introduction of NF-kappaB decoy-FITC into the tendon cells. IL-1-induced NF-kappaB activation was significantly inhibited by pretreatment of the cells with NF-kappaB decoy combined with radial shock wave exposure. The present study demonstrated the effectiveness of radial shock waves on introduction of NF-kappaB decoy into tendon cells. Radial shock wave treatment combined with local NF-kappaB decoy administration could be a novel therapeutic strategy for chronic tendinopathy.

A "polypill" for acute tendon pain in athletes with tendinopathy?

Acute tendon pain in athletes is a condition that is difficult to manage. There are few treatment options that give adequate pain relief and have a theoretical basis for efficacy. We report the use of a novel "polypill" for tendon pain, and provide evidence for the basis for its use. We present it to stimulate discussion and research into a new area of tendinopathy.

Active Expression of Matrix Metalloproteinase-13 mRNA in the Granulation Tissue of Equine Superficial Digital Flexor Tendinitis

The DNA microarray analysis for matrix metalloproteinase (MMP)-related mRNA expression in equine superficial digital flexor tendinitis indicated that mRNA level of MMP-13 was apparently up-regulated in the tendinitis as compared to normal tendon. In situ hybridization also revealed that fibroblastic cells proliferated in the granulation tissue generated in the tendinitis actively expressed MMP-13 mRNA. On the other hand, in normal tendon, a few fibroblastic cells and vascular components lied in the endotenon barely expressed its mRNA, but other cellular components in the tendon bundle were not positively hybridized. As mentioned above, MMP-13 but not other collagenases or gelatinases, may play an important role in tendon injuries in the racehorses.