Current pharmacological approaches to the treatment of tendinopathy

In Vitro CO-Releasing and Antioxidant Properties of Sulfonamide-Based CAI-CORMs in a H2O2-Stimulated Human Achilles Tendon-Derived Cell Model

Tendinopathy is often described as a complex and multifactorial condition which affects tendons. Tendon disorders are marked by a reduction in mechanical function, accompanied by pain and swelling. At the molecular level, tendinopathy leads to oxidative stress-driven inflammation, increased cell death, disruption of extracellular matrix balance, abnormal growth of capillaries and arteries, and degeneration of collagen formation. Here, we report an innovative approach to modulate oxidative stress during tendinopathy based on sulfonamide-based Carbonic Anhydrase Inhibitors-carbon monoxide releasing molecules (CAI-CORMs) hybrids endowed with dual carbon monoxide (CO) releasing activity and carbonic anhydrase (CA) inhibition. The synthesised compounds have been studied in a model of human Achilles tendon-derived cells stimulated by H2O2. Among the library, compound 1c and, to a greater extent, compound 1a, showed to be extremely effective in terms of restoration of cell metabolic activity and cell proliferation due to their capacity to release CO and inhibit the CA isoforms involved in inflammatory processes in the nanomolar range. Moreover, 1a can restore collagen type 1 secretion under pro-oxidant conditions.

Evaluating the effect of VersaWrap tendon protector on functional outcomes in operative tendon repairs

Background

Tendon repairs often result in adhesion formation which can cause persisting functional deficits. Close proximity of healing tissues increases friction during tendon excursion, often leading to tendon tethering postoperatively. Despite continued improvements in techniques for tendon repairs, there is currently no consensus on the most effective modality to reduce adhesion formation. The VersaWrap Tendon Protector is a bioresorbable hydrogel that is FDA-cleared for use in tendon repair by separating healing tendons from surrounding tissues and improving tendon gliding. We conducted a study to assess the efficacy of VersaWrap in improving clinical outcomes related to adhesions and tethering in tendon repairs involving the hand.

Materials & methods

Age, sex, injury type, mechanism of injury, visual analogue scale (VAS) pain scores, active and passive range of motion (ROM), percent return to normal function, and patient-reported outcomes forms (QuickDASH) were collected at baseline and routine follow up visits. Functional outcomes were classified according to Strickland and Glogovac grading system.

Results

90 patients were included, with an average age of 39.8 years and a 44% female gender. The most common mechanism of injury was sharp laceration, and the majority of repairs involved the extensor mechanism (58.8% extensor, 35.3% flexor, 5.8% both). At a mean follow-up of 4.6 months, the mean active and passive ROM was 88.8% and 94.3%, respectively. Mean percent return of function was 87.7%. Good or Excellent functional outcomes were achieved in 92.3% of patients - 70.5% Excellent, 21.8% Good, 6.4% Fair, 1.3% Poor. The average QuickDASH score was 30.7, and the average final VAS pain score was 1.3.

Conclusions

Tendon repairs and tenolysis procedures often result in reduced functionality due to impeded tendon gliding, and there is currently no consensus on optimal treatment to prevent tethering to surrounding tissues. The VersaWrap Tendon Protector creates a gelatinous layer between the tendon and surrounding soft tissue to improve gliding resistance, thereby limiting tendon sheath adhesions. Our data suggests that VersaWrap may be a useful adjunct in preventing tendon tethering adhesion post-repair.

High-volume injections in Achilles tendinopathy: a systematic review

INTRODUCTION

Achilles tendinopathy (AT) is common, particularly in runners. High-volume injections (HVIs) may be beneficial in the management of AT compared to other conservative management options, including exercise regimens, platelet-rich plasma (PRP) injections, and extracorporeal shockwave therapy. The published research on the effectiveness of HVI in the treatment of AT was evaluated in this systematic review.

SOURCES OF DATA

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed when conducting this systematic review. The electronic databases PubMed, Embase, Cochrane, Web of Science, CINAHL, and OVID were thoroughly searched, from inception to 13 September 2023, for articles assessing HVI for AT.

AREAS OF AGREEMENT

A total of 10 studies with 460 participants met the inclusion criteria. HVI typically consisted of saline, local anaesthetic, and corticosteroids. HVI combined with corticosteroids demonstrated immediate and long-term improvements in ankle function. Compared to HVI without corticosteroids, HVI with corticosteroids exhibited greater, early improvements in pain and function, with no significant differences at later follow-up points. Significant reductions in tendon thickness and neovascularity were also found with HVI treatment over time.

AREAS OF CONTROVERSY

No adverse events were reported with HVI, despite the use of corticosteroids.

GROWING POINTS

HVI is an effective and safe modality, particularly in the short term, to significantly reduce pain and discomfort in the Achilles tendon, especially when supplemented with corticosteroids.

AREAS TIMELY FOR DEVELOPING RESEARCH

More robust randomized controlled trials, with longer-term follow-ups and homogeneity, are needed to fully establish its efficacy for AT.

Platelet-Rich Plasma Versus Corticosteroid Injections for Chronic Tendinopathies: A Systematic Review and Meta-Analysis

Chronic tendinopathy is a degenerative condition characterized by persistent pain, functional limitations, and tendon thickening, often resulting from repetitive overuse or failed tendon healing. Left untreated, it can progress to tendon rupture, prolonged disability, and impaired quality of life. Management typically includes conservative therapies, such as physical therapy, corticosteroid (CS) injections for short-term relief, and platelet-rich plasma (PRP) as a regenerative therapy with potential long-term benefits. This systematic review and meta-analysis evaluates and compares the effectiveness of PRP and CS injections for chronic tendinopathies regarding pain reduction, functional improvement, and long-term outcomes. A structured search of PubMed, Scopus, Google Scholar, and the Cochrane Library identified randomized controlled trials (RCTs) and comparative studies. Primary outcomes included pain reduction and functional improvement while secondary outcomes assessed heterogeneity and publication bias. PRP and CS injections demonstrated no significant difference in short-term pain reduction. Functional outcomes were comparable in the short term but showed a trend favoring PRP at longer follow-up periods. PRP exhibited a slight advantage in long-term functional recovery, though the results were not statistically significant. Substantial heterogeneity across studies highlights the need for standardized protocols and larger trials to confirm these findings and optimize treatment strategies.

Mitochondrial destabilization in tendinopathy and potential therapeutic strategies

Tendinopathy is a prevalent aging-related disorder characterized by pain, swelling, and impaired function, often resulting from micro-scarring and degeneration caused by overuse or trauma. Current interventions for tendinopathy have limited efficacy, highlighting the need for innovative therapies. Mitochondria play an underappreciated and yet crucial role in tenocytes function, including energy production, redox homeostasis, autophagy, and calcium regulation. Abnormalities in mitochondrial function may lead to cellular senescence. Within this context, this review provides an overview of the physiological functions of mitochondria in tendons and presents current insights into mitochondrial dysfunction in tendinopathy. It also proposes potential therapeutic strategies that focus on targeting mitochondrial health in tenocytes. These strategies include: (1) utilizing reactive oxygen species (ROS) scavengers to mitigate the detrimental effects of aberrant mitochondria, (2) employing mitochondria-protecting agents to reduce the production of dysfunctional mitochondria, and (3) supplementing with exogenous normal mitochondria. In conclusion, mitochondria-targeted therapies hold great promise for restoring mitochondrial function and improving outcomes in patients with tendinopathy. The translational potential of this article: Tendinopathy is challenging to treat effectively due to its poorly understood pathogenesis. This review thoroughly analyzes the role of mitochondria in tenocytes and proposes potential strategies for the mitochondrial treatment of tendinopathy. These findings establish a theoretical basis for future research and the clinical translation of mitochondrial therapy for tendinopathy.

Efficacy and safety of extracorporeal shock wave therapy for upper limb tendonitis: a systematic review and meta-analysis of randomized controlled trials

Objective

This study synthesized the highest level of evidence to analyse the effectiveness and safety of using extracorporeal shock wave therapy (ESWT) to treat upper limb tendonitis, which was unknown.

Design

We conducted a systematic review and meta-analysis of 18 randomized controlled trials (RCTs) in PubMed, Embase, Web of Science, Medline, and the Cochrane Library.

Methods

Two researchers performed the screening, data extraction, literature quality assessment, and heterogeneity analysis of the searched RCTs.

Results

The main types of morbidity included rotator cuff tendonitis, lateral epicondylitis, finger tendonitis, and long bicipital tendonitis. The results of the meta-analysis showed that ESWT was effective in relieving pain in all four types of tendonitis. In addition, ESWT was more effective in relieving pain in patients with upper limb tendonitis than placebo at the 3- and 6-month follow-ups, especially with radial ESWT (RESWT). Data analysis of the forest plot showed that the experimental group with ESWT as an intervention had a significant improvement in function in patients with rotator cuff tendonitis at the 3-month follow-up. However, subgroup analysis showed that low-energy ESWT was effective in improving function in patients with calcified and non-calcified rotator cuff tendonitis, whereas it was not effective in relieving pain.

Conclusion

ESWT can effectively improve the functional activity in patients with rotator cuff tendonitis and may produce positive analgesic effects in patients with upper limb tendonitis. The incidence of adverse effects is low.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023403594, identifier: PROSPERO, CRD42023403594.

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.

Does radiofrequency application improve function and reduce pain in patients with insertional Achilles tendinopathy? A retrospective study with a minimum 2-year follow-up

This case series study aimed to investigate patients with insertional Achilles tendinopathy (IAT) who underwent radiofrequency (RF), how much do their patient-reported outcomes scores improve and what percentage return to sport, and what patient-related factors are associated with improved scores and increased odds of return to sport, at a minimum of 2-year follow-up. Between 2012 and 2018, 41 patients were followed up. The median Victorian Institute of Sports Assessment-Achilles (VISA-A) score increased from 20 (range, 3-62) to 97 (range, 53-100), the median 11-point visual analogue scale (VAS) reduced from 8 (range, 1-10) to 0 (range, 0-3) and the median Tenger score increased from 1 (range, 0-1) to 3 (range, 2-8). Thirty-eight (92.7%) patients returned to sports with a mean time of 11 ± 4.8 months. In linear regression analysis, age was significantly associated with return-to-sports outcome (b = -0.07, 95% CI = -0.13 to -0.02, p = 0.02), while in logistic regression, symptoms duration revealed a significant impact on pain presence (OR = 1.07, 95% CI = 1.01 to 1.14, p = 0.02). In summary, RF for IAT had a 68.7 ± 14.5 VISA-A improvement at 5.4 years of follow-up regarding reliable functional restoration and pain reduction; however, the current evidence remains insufficient to support RF as an effective treatment for IAT.

Tissue-engineered mesenchymal stem cell constructs alleviate tendinopathy by suppressing vascularization

Tendinopathy leads to low-grade tissue inflammation and chronic damage, which progresses due to pathological imbalance in angiogenesis. Reducing early pathological vascularization may be a new approach in helping to regenerate tendon tissue. Conventional stem cell therapy and tissue engineering scaffolds have not been highly effective at treating tendinopathy. In this study, tissue engineered stem cells (TSCs) generated using human umbilical cord mesenchymal stem cells (hUC-MSCs) were combined with microcarrier scaffolds to limit excessive vascularization in tendinopathy. By preventing VEGF receptor activation through their paracrine function, TSCs reduced in vitro angiogenesis and the proliferation of vascular endothelial cells. TSCs also decreased the inflammatory expression of tenocytes while promoting their anabolic and tenogenic characteristics. Furthermore, local injection of TSCs into rats with collagenase-induced tendinopathy substantially reduced early inflammation and vascularization. Mechanistically, transcriptome sequencing revealed that TSCs could reduce the progression of pathological angiogenesis in tendon tissue, attributed to Rap1-mediated vascular inhibition. TSCs may serve as a novel and practical approach for suppressing tendon vascularization, and provide a promising therapeutic agent for early-stage clinical tendinopathy.

Cellular and Structural Changes in Achilles and Patellar Tendinopathies: A Pilot In Vivo Study

Tendinopathies continue to be a challenge for both patients and the medical teams providing care as no universal clinical practice guidelines have been established. In general, tendinopathies are typically characterized by prolonged, localized, activity-related pain with abnormalities in tissue composition, cellularity, and microstructure that may be observed on imaging or histology. In the lower limb, tendinopathies affecting the Achilles and the patellar tendons are the most common, showing a high incidence in athletic populations. Consistent diagnosis and management have been challenged by a lack of universal consensus on the pathophysiology and clinical presentation. Current management is primarily based on symptom relief and often consists of medications such as non-steroidal anti-inflammatories, injectable therapies, and exercise regimens that typically emphasize progressive eccentric loading of the affected structures. Implementing the knowledge of tendon stem/progenitor cells (TSPCs) and assessing their potential in enhancing tendon repair could fill an important gap in this regard. In the present pilot in vivo study, we have characterized the structural and cellular alterations that occur soon after tendon insult in models of both Achilles and patellar tendinopathy. Upon injury, CD146+ TSPCs are recruited from the interfascicular tendon matrix to the vicinity of the paratenon, whereas the observed reduction in M1 macrophage polarization is related to a greater abundance of reparative CD146+ TSPCs in situ. The robust TSPCs' immunomodulatory effects on macrophages were also demonstrated in in vitro settings where TSPCs can effectively polarize M1 macrophages towards an anti-inflammatory therapeutic M2 phenotype. Although preliminary, our findings suggest CD146+ TSPCs as a key phenotype that could be explored in the development of targeted regenerative therapies for tendinopathies.

Antioxidant and anti-inflammatory injectable hydrogel microspheres for in situ treatment of tendinopathy

Tendinopathy is a common disorder that causes local dysfunction and reduces quality of life. Recent research has indicated that alterations in the inflammatory microenvironment play a vital role in the pathogenesis of tendinopathy. Herein, injectable methacrylate gelatin (GelMA) microspheres (GM) were fabricated and loaded with heparin-dopamine conjugate (HDC) and hepatocyte growth factor (HGF). GM@HDC@HGF were designed to balance the inflammatory microenvironment by inhibiting oxidative stress and inflammation, thereby regulating extracellular matrix (ECM) metabolism and halting tendon degeneration. Combining growth factors with heparin was expected to improve the encapsulation rate and maintain the long-term efficacy of HGF. In addition, the catechol groups on dopamine have adhesion and antioxidant properties, allowing potential attachment at the injured site, and better function synergized with HGF. GM@HDC@HGF injected in situ in rat Achilles tendinopathy (AT) models significantly down-regulated oxidative stress and inflammation, and ameliorated ECM degradation. In conclusion, the multifunctional platform developed presents a promising alternative for the treatment of tendinopathy.

A pilot study exploring the use of hyaluronic acid in treating insertional achilles tendinopathy

PURPOSE

This study explores the use of ultrasound-guided Hyaluronic Acid (HA) injections for Insertional Achilles Tendinopathy (IAT).

METHODS

A cohort of 15 ankles diagnosed with IAT received three weekly ultrasound-guided HA injections. The Victorian Institute of Sport Assessment - Achilles (VISA-A) questionnaire scored the severity of symptoms and functional impairment before treatment, and at one and six months post-treatment.

RESULTS

Significant improvement was observed in VISA-A scores post-treatment, rising from an average baseline of 34.8 ± 15.2 (11-63) to 53.6 ± 20.9 (15-77) after one month, and then to 50.7 ± 18.6 (20-75) after six months. No adverse reactions were noted, underscoring the safety of the intervention.

CONCLUSION

The pilot study presents HA injections as a potentially effective treatment for IAT, while interpretation of these findings must take into account the variability in results, indicating a range of patient responses. It encourages further research to confirm these findings and to explore HA's full potential in managing IAT, despite the limitations of a small sample size and lack of control group.

Patellar tendinopathy: an overview of prevalence, risk factors, screening, diagnosis, treatment and prevention

Patellar tendinopathy (PT), or jumper's knee, is an overuse injury that occurs in professional, as well as recreational, athletes. This condition is a noncontact injury, typically characterized by gradually increasing pain in the patellar tendon. It is prevalent in participants of several sports, but it occurs mostly in jumping sports. The diagnosis of PT is primarily clinical; however, imaging techniques can be useful as well. Risk factors differ between sexes, playing conditions, the kind of sport, playing level and personal characteristics. Screening is an essential tool to assess PT. This condition affects athletic performance and often persists for years. The use of preventative methods is imperative because of the persistence of this condition, especially in elite athletes who sometimes end their career after long and failed treatments. There are a wide variety of treatment and rehabilitation options available, the majority of which are non-operative, such as eccentric exercises, cryotherapy, platelet-rich plasma (PRP) injections, and anti-inflammatory strategies. If conservative treatment fails, surgery is the next most preferable step. Even though there are many surgical treatment methods, there is no clear evidence on what is the most effective approach to address PT. Taking this into consideration, as well as the extent of this clinical entity, novel therapeutic techniques, as well as screening and prevention methods, are expected to emerge in the near future.

Safety and Efficacy of Bone Marrow-Derived Mesenchymal Stem Cells for Chronic Patellar Tendinopathy (With Gap >3 mm) in Patients: 12-Month Follow-up Results of a Phase 1/2 Clinical Trial

Background

In a previous study, the authors found that at 6 months after treatment with a 20 × 106 dose of bone marrow-derived mesenchymal stem cells (BM-MSCs), patients showed improved tendon structure and regeneration of the gap area when compared with treatment using leukocyte-poor platelet-rich plasma (Lp-PRP). The Lp-PRP group (n = 10), which had not seen tendon regeneration at the 6-month follow-up, was subsequently offered treatment with BM-MSCs to see if structural changes would occur. In addition, the 12-month follow-up outcomes of the original BM-MSC group (n = 10) were evaluated.

Purpose

To evaluate the outcomes of all patients (n = 20) at 12 months after BM-MSC treatment and observe if the Lp-PRP pretreated group experienced any type of advantage.

Study Design

Cohort study; Level of evidence, 2.

Methods

Both the BM-MSC and original Lp-PRP groups were assessed at 12 months after BM-MSC treatment with clinical examination, the visual analog scale (VAS) for pain during daily activities and sports activities, the Victorian Institute of Sport Assessment-Patella score for patellar tendinopathy, dynamometry, and magnetic resonance imaging (MRI). Differences between the 2 groups were compared with the Student t test.

Results

The 10 patients originally treated with BM-MSCs continued to show improvement in tendon structure in their MRI scans (P < .0001), as well as in the clinical assessment of their pain by means of scales (P < .05). Ten patients who were originally treated with Lp-PRP and then with BM-MSCs exhibited an improvement in tendon structure in their MRI scans, as well as a clinical pain improvement, but this was not significant on the VAS for sports (P = .139). Thus, applying Lp-PRP before BM-MScs did not yield any type of advantage.

Conclusion

The 12-month follow-up outcomes after both groups of patients (n = 20) received BM-MSC treatment indicated that biological treatment was safe, there were no adverse effects, and the participants showed a highly statistically significant clinical improvement (P < .0002), as well as an improvement in tendon structure on MRI (P < .0001). Preinjection of Lp-PRP yielded no advantages.

Achilles Tendinopathy Pathogenesis and Management: A Narrative Review

The Achilles tendon is the thickest and strongest tendon of the human body, and it is frequently injured during sports activity. The incidence of Achilles tendon pathologies has increased over recent decades, especially in the last few years, because of increased sports participation among the general population and due to the diffusion of competitive sports at a high level. Tendinopathies are common in athletes and in middle-aged overweight patients. The term "tendinopathy" refers to a condition characterised clinically by pain and swelling, with functional limitations of tendon and nearby structures, and consequently to chronic failure of healing response process. Tendinopathies can produce marked morbidity, and at present, scientifically validated management modalities are limited. Despite the constantly increasing interest and number of studies about Achilles tendinopathy (AT), there is still not a consensual point of view on which is the best treatment, and its management is still controversial. AT can be treated conservatively primarily, with acceptable results and clinical outcomes. When this approach fails, surgery should be considered. Several surgical procedures have been described for both conditions with a relatively high rate of success with few complications and the decision for treatment in patients with AT should be tailored on patient's needs and level of activity. The aim of this article is to give insights about the pathogenesis and most used and recent treatment options for AT.

Local injection therapy in the complex treatment of musculoskeletal disorders: principles of application, evidence base, safety

Local injection therapy (LIT)  is an important component of the complex treatment of musculoskeletal disorders (MSD), which is widely used in real clinical practice. Glucocorticoids, hyaluronic acid drugs (HA), autologous cell drugs, botulinum toxin type A, radioactive isotopes, etc. are used for LIT.  LIT makes it possible to achieve a pronounced symptomatic effect, while in some cases, for example, repeated HA treatments in patients with osteoarthritis, the possibility of slowing the progression of the disease and reducing the need for surgical treatment is discussed.

The performance of LIT requires special skills and abilities of the physician, careful compliance with the rules of asepsis and antisepsis, and instrumental visualization. LIT can be associated with serious complications and therefore must be performed according to strict indications.

The Expert Council was devoted to defining the basic principles of LIT. The indications for the use of certain types of this therapies, the evidence base for its efficacy and safety, the order of application of different drugs, and the need to combine LIT with other drug and non-drug treatments of MSD were reviewed.

Pathways driving tendinopathy and enthesitis: siblings or distant cousins in musculoskeletal medicine?

Tendinopathy and enthesitis share clinical, anatomical, and molecular parallels. However, their relationship is complex, presenting challenges in diagnosis and treatment. The biomechanics underlying these pathologies, together with relative immune and stromal contributions to pathology, are characterised by crucial comparative elements. However, methodologies used to study enthesitis and tendinopathy have been divergent, which could account for discrepancies in how these conditions are perceived and treated. In this Review, we summarise key clinical parallels between these two common presentations in musculoskeletal medicine and address factors that currently preclude development of more effective therapeutics. Furthermore, we describe molecular similarities and disparities that govern pathological mechanisms in tendinopathy and enthesitis, thus informing translational studies and treatment strategies.

Tendon pain - what are the mechanisms behind it?

OBJECTIVES

Management of chronic tendon pain is difficult and controversial. This is due to poor knowledge of the underlying pathophysiology of chronic tendon pain, priorly known as tendinitis but now termed tendinopathy. The objective of this topical review was to synthesize evolving information of mechanisms in tendon pain, using a comprehensive search of the available literature on this topic.

CONTENT

This review found no correlations between tendon degeneration, collagen separation or neovascularization and chronic tendon pain. The synthesis demonstrated that chronic tendon pain, however, is characterized by excessive nerve sprouting with ingrowth in the tendon proper, which corresponds to alterations oberserved also in other connective tissues of chronic pain conditions. Healthy, painfree tendons are devoid of nerve fibers in the tendon proper, while innervation is confined to tendon surrounding structures, such as sheaths. Chronic painful tendons exhibit elevated amounts of pain neuromediators, such as glutamate and substance p as well as up-regulated expression and excitability of pain receptors, such as the glutamate receptor NMDAR1 and the SP receptor NK1, found on ingrown nerves and immune cells. Increasing evidence indicates that mast cells serve as an important link between the peripheral nervous system and the immune systems resulting in so called neurogenic inflammation.

SUMMARY

Chronic painful tendons exhibit (1) protracted ingrowth of sensory nerves (2) elevated pain mediator levels and (3) up-regulated expression and excitability of pain receptors, participating in (4) neuro-immune pathways involved in pain regulation. Current treatments that entail the highest scientific evidence to mitigate chronic tendon pain include eccentric exercises and extracorporeal shockwave, which both target peripheral neoinnervation aiming at nerve regeneration.

OUTLOOK

Potential mechanism-based pharmacological treatment approaches could be developed by blocking promotors of nerve ingrowth, such as NGF, and promoting inhibitors of nerve ingrowth, like semaphorins, as well as blocking glutamate-NMDA-receptor pathways, which are prominent in chronic tendon pain.

Optimizing repair of tendon ruptures and chronic tendinopathies: Integrating the use of biomarkers with biological interventions to improve patient outcomes and clinical trial design

Tendons are dense connective tissues of the musculoskeletal system that link bones with muscles to foster mobility. They have complex structures and exist in varying biomechanical, metabolic and biological environments. In addition, tendon composition and mechanical properties can change over the lifespan as an individual ages. Many tendons function in high stress conditions with a low vascular and neuronal supply, conditions often leading to development of chronic tendinopathies, and in some cases, overt rupture of the tissues. Given their essential nature for human mobility and navigation through the environment, the effective repair and regeneration of different tendons after injury or damage is critical for quality of life, and for elite athletes, the return to sport participation at a high level. However, for mainly unknown reasons, the outcomes following injury are not always successful and lead to functional compromise and risk for re-injury. Thus, there is a need to identify those patients who are at risk for developing tendon problems, as well those at risk for poor outcomes after injury and to design interventions to improve outcomes after injury or rupture to specific tendons. This review will discuss recent advances in the identification of biomarkers prognostic for successful and less successful outcomes after tendon injury, and the mechanistic implications of such biomarkers, as well as the potential for specific biologic interventions to enhance outcomes to improve both quality of life and a return to participation in sports. In addition, the implication of these biomarkers for clinical trial design is discussed, as is the issue of whether such biomarkers for successful healing of one tendon can be extended to all tendons or are valid only for tendons in specific biomechanical and biological environments. As maintaining an active lifestyle is critical for health, the successful implementation of these advances will benefit the large number of individuals at risk.

Efficacy of Platelet-Rich Plasma Versus Placebo in the Treatment of Tendinopathy: A Meta-analysis of Randomized Controlled Trials

OBJECTIVE

To evaluate the efficacy of platelet-rich plasma (PRP) injections versus placebo in the treatment of tendinopathy.

DATA SOURCES

We performed a systematic literature search in MEDLINE, Embase, Scopus, CINAHL, Cochrane Library, and ClinicalTrials.gov through November 2020 to identify randomized controlled trials (RCTs) that evaluated the clinical efficacy of PRP versus placebo for the treatment of tendinopathy. Outcomes were analyzed on an intention-to-treat basis with random-effects models.

MAIN RESULTS

A total of 13 RCTs were included in this meta-analysis. The pooled analysis showed no significant difference in pain relief at 4 to 6 weeks (standard mean difference [SMD]: -0.18, 95% confidence intervals [CI]: -0.62 to 0.26), 12 weeks (SMD: -0.14, 95% CI: -0.55 to 0.26), and ≥24 weeks (SMD: -0.56, 95% CI: -1.16 to 0.05) or function improvement at 4 to 6 weeks (SMD: 0.11, 95% CI: -0.13 to 0.35), 12 weeks (SMD: 0.18, 95% CI: -0.13 to 0.49), and ≥24 weeks (SMD: 0.26, 95% CI: -0.14 to 0.66) for PRP compared with placebo in the treatment of tendinopathy. The sensitivity analysis indicated no significant difference in pain relief or function improvement at 12 weeks between PRP and placebo for different types of tendinopathies, treatment regimens, leukocyte concentrations, or cointerventions.

CONCLUSIONS

Platelet-rich plasma injection was not found to be superior to placebo in the treatment of tendinopathy, as measured by pain relief and functional improvement at 4 to 6, 12, and ≥24 weeks.

Fullerenol inhibits tendinopathy by alleviating inflammation

Tendinopathy is a common disease in orthopaedics, seriously affecting tendon functions. However, the effects of non-surgical treatment on tendinopathy are not satisfactory and surgical treatments possibly impair the function of tendons. Biomaterial fullerenol has been proved to show good anti-inflammatory effects on various inflammatory diseases. For in vitro experiments, primary rat tendon cells (TCs) were treated by interleukin-1 beta (IL-1β) combined with aqueous fullerenol (5, 1, 0.3 μg/mL). Then inflammatory factors, tendon-related markers, migration and signaling pathways were detected. For in vivo experiments, rat tendinopathy model was constructed by local injection of collagenase into Achilles tendons of rats and fullerenol (0.5, 1 mg/mL) was locally injected 7 days after collagenase injection. Inflammatory factors and tendon-related markers were also investigated. Fullerenol with good water-solubility showed excellent biocompatibility with TCs. Fullerenol could increase expression of tendon-related factors (Collagen I and tenascin C) and decrease expression of inflammatory factors (matrix metalloproteinases-3, MMP-3, and MMP-13) and reactive oxygen species (ROS) level. Simultaneously, fullerenol slowed the migration of TCs and inhibited activation of Mitogen-activated protein kinase (MAPK) signaling pathway. Fullerenol also attenuated tendinopathy in vivo, including reduction of fiber disorders, decrease of inflammatory factors and increase of tendon markers. In summary, fullerenol is a promising biomaterial that can be used to treat tendinopathy.

Tendon Aging

Tendons are mechanosensitive connective tissues responsible for the connection between muscles and bones by transmitting forces that allow the movement of the body, yet, with advancing age, tendons become more prone to degeneration followed by injuries. Tendon diseases are one of the main causes of incapacity worldwide, leading to changes in tendon composition, structure, and biomechanical properties, as well as a decline in regenerative potential. There is still a great lack of knowledge regarding tendon cellular and molecular biology, interplay between biochemistry and biomechanics, and the complex pathomechanisms involved in tendon diseases. Consequently, this reflects a huge need for basic and clinical research to better elucidate the nature of healthy tendon tissue and also tendon aging process and associated diseases. This chapter concisely describes the effects that the aging process has on tendons at the tissue, cellular, and molecular levels and briefly reviews potential biological predictors of tendon aging. Recent research findings that are herein reviewed and discussed might contribute to the development of precision tendon therapies targeting the elderly population.

Tendon tissue engineering: An overview of biologics to promote tendon healing and repair

Tendons are dense connective tissues with a hierarchical polarized structure that respond to and adapt to the transmission of muscle contraction forces to the skeleton, enabling motion and maintaining posture. Tendon injuries, also known as tendinopathies, are becoming more common as populations age and participation in sports/leisure activities increases. The tendon has a poor ability to self-heal and regenerate given its intrinsic, constrained vascular supply and exposure to frequent, severe loading. There is a lack of understanding of the underlying pathophysiology, and it is not surprising that disorder-targeted medicines have only been partially effective at best. Recent tissue engineering approaches have emerged as a potential tool to drive tendon regeneration and healing. In this review, we investigated the physiochemical factors involved in tendon ontogeny and discussed their potential application in vitro to reproduce functional and self-renewing tendon tissue. We sought to understand whether stem cells are capable of forming tendons, how they can be directed towards the tenogenic lineage, and how their growth is regulated and monitored during the entire differentiation path. Finally, we showed recent developments in tendon tissue engineering, specifically the use of mesenchymal stem cells (MSCs), which can differentiate into tendon cells, as well as the potential role of extracellular vesicles (EVs) in tendon regeneration and their potential for use in accelerating the healing response after injury.

Efficacy of low-level laser therapy in patients with lower extremity tendinopathy or plantar fasciitis: systematic review and meta-analysis of randomised controlled trials

OBJECTIVES

We investigated the effectiveness of low-level laser therapy (LLLT) in lower extremity tendinopathy and plantar fasciitis on patient-reported pain and disability.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Eligible articles in any language were identified through PubMed, Embase and Physiotherapy Evidence Database (PEDro) on the 20 August 2020, references, citations and experts.

ELIGIBILITY CRITERIA FOR SELECTION OF STUDIES

Only randomised controlled trials involving participants with lower extremity tendinopathy or plantar fasciitis treated with LLLT were included.

DATA EXTRACTION AND SYNTHESIS

Random effects meta-analyses with dose subgroups based on the World Association for Laser Therapy treatment recommendations were conducted. Risk of bias was assessed with the PEDro scale.

RESULTS

LLLT was compared with placebo (10 trials), other interventions (5 trials) and as an add-on intervention (3 trials). The study quality was moderate to high.Overall, pain was significantly reduced by LLLT at completed therapy (13.15 mm Visual Analogue Scale (VAS; 95% CI 7.82 to 18.48)) and 4-12 weeks later (12.56 mm VAS (95% CI 5.69 to 19.42)). Overall, disability was significantly reduced by LLLT at completed therapy (Standardised Mean Difference (SMD)=0.39 (95% CI 0.09 to 0.7) and 4-9 weeks later (SMD=0.32 (95% CI 0.05 to 0.59)). Compared with placebo control, the recommended doses significantly reduced pain at completed therapy (14.98 mm VAS (95% CI 3.74 to 26.22)) and 4-8 weeks later (14.00 mm VAS (95% CI 2.81 to 25.19)). The recommended doses significantly reduced pain as an add-on to exercise therapy versus exercise therapy alone at completed therapy (18.15 mm VAS (95% CI 10.55 to 25.76)) and 4-9 weeks later (15.90 mm VAS (95% CI 2.3 to 29.51)). No adverse events were reported.

CONCLUSION

LLLT significantly reduces pain and disability in lower extremity tendinopathy and plantar fasciitis in the short and medium term. Long-term data were not available. Some uncertainty about the effect size remains due to wide CIs and lack of large trials.

PROSPERO REGISTRATION NUMBER

CRD42017077511.

Application of Biomaterials in Prevention and Treatment of Calf Tendon Injury in Football Games

Football sports can easily lead to a calf strain and tendon damage. To this end, we explored the therapeutic effect of sodium hyaluronate biomaterial-assisted micro-suturing in treating calf tendon injury after football sports. Given this, we will group the patients to compare the test and conduct the efficacy analysis. One group was sutured by ordinary microsurgery. The other was sutured and combined with sodium hyaluronate treatment. The study found that there were statistical differences in tendon recovery between the two groups of patients. Sodium hyaluronate biomaterial can improve the treatment effect of calf tendon injury in football sports. This biological material is worthy of clinical application.

Farrerol alleviates collagenase-induced tendinopathy by inhibiting ferroptosis in rats

Tendinopathy is mainly characterized by local pain, functional limitation and decreased athletic ability, which seriously affects the quality of life of patients and the career of athletes. Farrerol (FA), one of the main active compounds extracted from Rhododendron and plants in the Rhododendron family, has a wide range of pharmacological activities, such as immunomodulatory, anti-inflammatory and antiviral effects. However, the effect of FA on tendinopathy is unclear. Here, we investigated the pharmacological effect and mechanism of FA in tendon injury through collagenase-induced tendinopathy in vivo and RSL3-induced tenocytes injury in vitro. The results showed that FA alleviated the infiltration of inflammatory cells, promoted tenogenesis and improved mechanical properties of the Achilles tendon in rats. In addition, ferroptosis inducer RSL3 inhibits the tenogenesis in vitro and in vivo, which accelerates the progression of tendinopathy. Moreover, FA effectively inhibited iron accumulation and alleviated ferroptosis in the Achilles tendon. Using in vitro experiments, we found that FA antagonized ferroptosis by reducing lipid peroxidation and iron accumulation in tenocytes. Finally, we found that glutathione peroxidase 4 silencing could block the protective effect of FA on ferroptosis of tenocytes. Therefore, the results of this study suggest that FA can relieve collagenase-induced tendinopathy by inhibiting ferroptosis, and reveal that FA may be a potentially effective drug for the treatment of tendinopathy in the future.

The tendon microenvironment: Engineered in vitro models to study cellular crosstalk

Tendinopathy is a multi-faceted pathology characterized by alterations in tendon microstructure, cellularity and collagen composition. Challenged by the possibility of regenerating pathological or ruptured tendons, the healing mechanisms of this tissue have been widely researched over the past decades. However, so far, most of the cellular players and processes influencing tendon repair remain unknown, which emphasizes the need for developing relevant in vitro models enabling to study the complex multicellular crosstalk occurring in tendon microenvironments. In this review, we critically discuss the insights on the interaction between tenocytes and the other tendon resident cells that have been devised through different types of existing in vitro models. Building on the generated knowledge, we stress the need for advanced models able to mimic the hierarchical architecture, cellularity and physiological signaling of tendon niche under dynamic culture conditions, along with the recreation of the integrated gradients of its tissue interfaces. In a forward-looking vision of the field, we discuss how the convergence of multiple bioengineering technologies can be leveraged as potential platforms to develop the next generation of relevant in vitro models that can contribute for a deeper fundamental knowledge to develop more effective treatments.

The Cincinnati incision is safe and effective for revision surgery for insertional tendinopathy of the Achilles tendon

The present study reports the outcomes of revision surgery using a Cincinnati incision with tendon debridement and calcaneoplasty for insertional Achilles tendinopathy (IAT) in a cohort of patients at 24-month follow-up. Patients undergoing revision surgery following failed previous surgery for IAT were prospectively recruited. Patients were assessed pre-operatively and at 3, 6,12 and 24 months. The Victorian Institute of Sport Assessment Scale for Achilles Tendinopathy (VISA-A), the EQ5D questionnaire and the visual analogue scale (VAS) were used for evaluation. Data from 33 patients with a mean age of 43.9 years old are reported. 27% (9 of 33 patients) were female. The left side was involved in 58% (19/33) of patients. No clinically relevant complications were reported in any of the patients. Most of subscales of EQ5D improved at last follow-up: Usual Activities (P = 0.01), Mobility (P = 0.03), Pain/Discomfort (P = 0.001), Thermometer (P = 0.04). No statistically significant change for the subscales Self-Care (P = 0.08) and Anxiety-Depression (P = 0.1) was evidenced. The VISA-A score improved significantly at last follow-up (P < 0.0001), as did the VAS score (P < 0.0001). These results indicated that a Cincinnati incision followed by tendon debridement and calcaneoplasty for revision surgery for IAT is feasible and reliable, achieving clinically relevant improvement in the VISA-A, EQ5D and VAS at 24 months follow-up.

The effects of orthobiologics in the treatment of tendon pathologies: a systematic review of preclinical evidence

Purpose

The aim of this systematic review is to explore the current available knowledge about tendon disorders and orthobiologics derived by preclinical experiments to evaluate their role and efficacy in the different stages and conditions related to the tendon healing processes.

Methods

The systematic review was performed according to the PRISMA guidelines. Different electronic databases (MEDLINE, Web of Science, EMBASE) were searched for studies investigating orthobiologics (PRP and cell-based products from adipose tissue or bone marrow) in animal models or veterinary clinical trials for tendon pathologies (complete/partial tendon ruptures, rotator cuff tears, tendinopathy, enthesis-related injuries). Data regarding the specific product used, the treatment site/pathology, the host and the model were collected. The results were classified into the following categories: histological, biomechanical, molecular and imaging.

Results

A large pool of preclinical studies on tendon disorders have been found on platelet-rich plasma (PRP), while data about stromal vascular fraction (SVF) and bone marrow concentrate (BMAC) are still limited and frequently focused on expanded cells, rather than orthobiologics prepared at the point of care.

The effect of PRP is related to an acceleration of the healing process, without improvements in the final structure and properties of repaired tendon. Cell-based products have been reported to produce more durable results, but the level of evidence is currently insufficient to draw clear indications.

Conclusions

The preclinical results about orthobiologics applications to tendon pathologies would support the rationale of their clinical use and encourage the performance of clinical trials aimed to confirm these data in human subjects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-022-00468-w.

Therapeutic Effects of Platelet-Derived Extracellular Vesicles in a Bioengineered Tendon Disease Model

Tendon injuries represent over 30-50% of musculoskeletal disorders worldwide, yet the available therapies do not provide complete tendon repair/regeneration and full functionality restoring. Extracellular vesicles (EVs), membrane-enclosed nanoparticles, have emerged as the next breakthrough in tissue engineering and regenerative medicine to promote endogenous tissue regeneration. Here, we developed a 3D human in vitro model mimicking the signature of pathological tendon and used it to evaluate the influence that different platelet-derived EVs might have in tendon tissue repair mechanisms. For this, different EV populations isolated from platelets, small EVs (sEVs) and medium EVs (mEVs), were added to the culture media of human tendon-derived cells (hTDCs) cultured on isotropic nanofibrous scaffolds. The platelet-derived EVs increased the expression of tenogenic markers, promoted a healthy extracellular matrix (ECM) remodeling, and the synthesis of anti-inflammatory mediators. These findings suggest that platelet EVs provided relevant biochemical cues that potentiated a recovery of hTDCs phenotype from a diseased to a healthy state. Thus, this study opens new perspectives for the translation of platelet-derived EVs as therapeutics.

In vitro effect of triamcinolone and platelet-rich plasma on cytokine levels of elbow lateral epicondylitis-derived cells

Background

The pathogenesis and treatment of lateral elbow epicondylitis (LEE) are still controversial. The purpose of the current study was to evaluate the production of inflammatory cytokines by LEE-derived cells and to compare the anti-inflammatory effect of triamcinolone acetonide with platelet-rich plasma (PRP) on cytokines production in primary culture of these cells.

Methods

Third passage cells from primary cultures of LEE were assessed for the production of the cytokines IL-1β, IL-6, IL-8, IL-10 and TNF-α by immune-enzymatic assay (ELISA), after the treatment with 1, 10 and 100 μM triamcinolone compared to no treated controls at the time points 6, 12, 18, 24, 48, 72 and 96 h, and to PRP at 48, 72 and 96 h.

Results

The cytokines IL-6 and IL-8 were produced in high concentrations by LEE cells. One, 10 and 100 μM triamcinolone induced significant decrease in the production of IL-6 and IL-8 at 48, 72 and 96 h, adding the time point 12 h for IL-8. Compared to controls, PRP caused a significant increase in the production of IL-6 and IL-8 and there was a significant increase in IL-10 production with the use of 100 μM triamcinolone at 48 h. The production of IL1-β and TNF-α was very low and did not change when the cultures were treated with triamcinolone or PRP.

Conclusion

LEE-derived cells produce IL-6 and IL-8, confirming the inflammatory nature of this condition. While triamcinolone inhibited the production of IL-6 and IL-8 by LEE cells, PRP induced an increase in these cytokines compared with controls.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-02990-0.

Low Molecular Weight Hyaluronic Acid (500-730 Kda) Injections in Tendinopathies-A Narrative Review

Tendinopathies are common causes of pain and disability in general population and athletes. Conservative treatment is largely preferred, and eccentric exercise or other modalities of therapeutic exercises are recommended. However, this approach requests several weeks of consecutive treatment and could be discouraging. In the last years, injections of different formulations were evaluated to accelerate functional recovery in combination with usual therapy. Hyaluronic acid (HA) preparations were proposed, in particular LMW-HA (500-730 kDa) for its unique molecular characteristics in favored extracellular matrix homeostasis and tenocyte viability. The purpose of our review is to evaluate the state-of-the-art about the role of 500-730 kDa in tendinopathies considering both preclinical and clinical findings and encourage further research on this emerging topic.

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

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

Adipose micro-grafts enhance tendinopathy healing in ovine model: An in vivo experimental perspective study

In Europe, approximatively 100 000 to 500 000 tendon repairs are performed every year. These procedures are associated with a considerable rate of postoperative complications (from 6% to 11%). Autologous micro-grafts (AAMG) and stromal vascular fraction (SVF) have been shown to improve tendon healing in 60% to 70% of treated rodents. The purpose of this study was to evaluate the effects of AAMG in a sheep model with tendinopathy. We used sheep models because, as a large animal, they are more comparable to humans. The hypothesis was that SVF injection would improve tendon healing compared with the control group, reducing inflammatory and matrix degrading, while increasing anti-inflammatory expression and collagen synthesis in the early stage of tendon injury. Sixteen Apennine sheep aged 2 to 5 years underwent 500 UI type I collagenase injection into both common calcaneal tendons (CCT) to induce tendinopathy. After 15 days (T0), one CCT in every ovine underwent randomly to 2.5 mL of AAMG obtained by mechanical disruption and the contralateral CCTs received no treatment. Clinical, ecographic, and sonographic evaluations were performed after 4 weeks (T1) and 8 weeks (T2). Histological, immunohistochemical, real-time polymerase chain reaction (RT-PCR), and biomechanical evaluations were performed at T2. At T2, the treated group showed a final tendon diameter (9.1 ± 1.4 mm) and a hardness expression (62%) that were similar to the original healthy tendon (8.1 ± 1.1 mm; 100%), with a significant recovery compared with the control group (9.5 ± 1.7 mm; 39%). Moreover, histological analysis of the treated group revealed an improvement in the fiber orientation score, fiber edema score, infiltrative-inflammatory process, and necrosis score (4.3 ± 3.3) compared with control group (8.8 ± 2.9). Immunohistochemically, the treated group showed high expression of collagen 1, Factor VIII and significantly low expression of collagen 3. These data were confirmed by RT-PCR analysis. The study findings suggested that AAMGs obtained through mechanical disruption present a safe, efficient, and reliable technique, enhancing tendon healing.

Novel approaches of the nanotechnology-based drug delivery systems for knee joint injuries: A review

The knee joint is one of the largest, most complex, and frequently utilized organs in the body. It is very vulnerable to injuries due to activities, diseases, or accidents, which lead to or cause knee joint injuries in people of all ages. There are several types of knee joint injuries such as contusions, sprains, and strains to the ligament, tendon injuries, cartilage injuries, meniscus injuries, and inflammation of synovial membrane. To date, many drug delivery systems, e.g. nanoparticles, dendrimers, liposomes, micelles, and exosomes, have been used for the treatment of knee joint injuries. They aim to alleviate or reverse the symptoms with an improvement of the function of the knee joint by restoring or curing it. The nanosized structures show good biodegradability, biocompatibility, precise site-specific delivery, prolonged drug release, and enhanced efficacy. They regulate cell proliferation and differentiation, ECM synthesis, proinflammatory factor secretion, etc. to promote repair of injuries. The goal of this review is to outline the finding and studies of the novel strategies of nanotechnology-based drug delivery systems and provide future perspectives to combat the challenges of knee joint injuries by using nanotechnology.

The Role of Hyaluronic Acid in Sport-Related Tendinopathies: A Narrative Review

Tendinopathy is a complex clinical condition with a rising incidence and prevalence, particularly during sports practice. For the return to play in affected patients, adequate functional and structural recovery of the tendon is the ultimate goal, avoiding the high risk of recurrence. In this perspective, local therapies alongside exercise are showing promising results. Despite evidence suggesting hyaluronic acid (HA) injections as effective in the treatment of tendinopathy, current recommendations about the management of this condition do not include this intervention. HA seems to be an effective therapeutic option for the management of sport-related tendinopathies, but further studies with a larger sample size are needed to confirm available findings. In this narrative review, we analyzed available literature about the rationale of the use of HA in the management of tendon injury and, particularly, in sport-related tendinopathies.

Effect of Eriocitrin on Cell Proliferation, Apoptosis, Migration, and Scar Formation-Related Genes Expression in Tendon Stem Cells

Tendinopathy is a common disease in elite and recreational athletes, and Eriocitrin is a flavonoid compound, which has antioxidant properties. The present study was undertaken to investigate the effect of Eriocitrin on tendon stem cells in vitro. Different concentrations of Eriocitrin (0, 25, 50, 75 µM) were used to treat tendon stem cells, cell proliferation was determined by CCK8 assay, apoptosis was detected by propidium iodide (PI) staining assays and caspase-3 activity assessment, wound-healing assaywas selected to detect the migration, and RT-PCR was chosen to detect the expression levels of scar formation-related gene markers (COMP, Fibronectin, and Biglycan). Eriocitrin treatment promoted cell proliferation of tendon stem cells in dose-dependent manner, and it reduced the apoptotic activities and improved the migration of tendon stem cells. It inhibited COMP, Biglycan, and Fibronectin expression. In summary, eriocitrin promoted cell proliferation of tendon stem cells, improved the migration of tendon stem cells, and inhibited the expression levels of some scar formation-related gene markers.

Hamid MS. Efficacy of prolotherapy in comparison to other therapies for chronic soft tissue injuries: A systematic review and network meta-analysis

Introduction

Prolotherapy and other injections, primarily acting on pathways associated with maladaptive tissue repair, are recommended for recalcitrant chronic soft tissue injuries (CSTI). However, selection of injection is challenging due to mixed results. This network meta-analysis (NMA) aimed to compare prolotherapy with other therapies, particularly injections, for CSTI and establish robustness of the results.

Methodology

Pubmed, Medline, SPORTDiscus and Google scholar were searched from inception to 4^th January 2021 for randomised controlled trials (RCTs) involving injection therapies (e.g. blood derivatives, corticosteroid, hyaluronic acid, botulinum toxin) for CSTI. The primary and secondary outcomes were pain and function, respectively, at (or nearest to) 6 months. Effect size (ES) was presented as standardised mean difference with 95% confidence interval (CI). Frequentist random effect NMA was used to generate the overall estimates, subgroup estimates (by region and measurement time point) and sensitivity analyses.

Results

A total of 91 articles (87 RCTs; 5859 participants) involving upper limb (74%), lower limb (23%) and truncal/hip (3%) injuries were included. At all time points, prolotherapy had no statistically significant pain benefits over other therapies. This observation remained unchanged when tested under various assumptions and with exclusion of studies with high risk of bias. Although prolotherapy did not offer statistically significant functional improvement compared to most therapies, its ES was consistently better than non-injections and corticosteroid injection for both outcomes. At selected time points and for selected injuries, prolotherapy demonstrated potentially better pain improvement over placebo (<4 months: shoulder [ES 0.65; 95% CI 0.00 to 1.30]; 4–8 months: elbow [ES 0.91; 95% CI 0.12 to 1.70]; >8 months: shoulder [ES 2.08; 95% CI 1.49, to 2.68]). Injections generally produced greater ES when combined with non-injection therapy.

Conclusion

While clinical outcomes were generally comparable across types of injection therapy, prolotherapy may be used preferentially for selected conditions at selected times.

The effect of the platelet-rich plasma and ozone therapy on tendon-to-bone healing in the rabbit rotator cuff repair model

Background

The aim of this study is to histologically and biomechanically investigate the effects of local PRP and ozone therapy (O₂O₃) on tendon-to-bone healing in a rabbit model of the supraspinatus tendon tear.

Methods

Four groups were formed to have seven rabbits in each group: repair, R; repair + PRP, RP; repair + ozone, RO; and repair + PRP + ozone, RPO. The supraspinatus tendon was detached by sharp dissection from the footprint and an acute tear pattern was created. Thereafter, tendon repair was performed with the transosseous technique. In the RP group, PRP, and in the RPO group, PRP + O2O3 mixture was injected to the tendon repair site. In the RO group, O₂O₃ gas mixture was injected into subacromial space three times a week for a total of 4 weeks. The study was ended at postoperative 6th week.

Results

When compared with the R group, a statistically significant increase was observed in the biomechanical strength of the RP and RPO groups. The highest increase in biomechanical strength was detected in the RPO group. The histology of the RO and RPO groups showed better collagen fiber continuity and orientation than the R and RP groups.

Conclusions

The results obtained from this study show that the ozonized PRP can be used as biological support to increase tendon-to-bone healing. However, these results need to be supported by clinical studies.

Tendinopathy

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