A Hypothesis for the Anti-Inflammatory and Mechanotransduction Molecular Mechanisms Underlying Acupuncture Tendon Healing

The roles and mechanisms of the NF-κB signaling pathway in tendon disorders

Both acute and chronic tendon injuries are the most frequently occurring musculoskeletal diseases in human and veterinary medicine, with a limited repertoire of successful and evidenced-based therapeutic strategies. Inflammation has been suggested as a key driver for the formation of scar and adhesion tissue following tendon acute injury, as well as pathological alternations of degenerative tendinopathy. However, prior efforts to completely block this inflammatory process have yet to be largely successful. Recent investigations have indicated that a more precise targeted approach for modulating inflammation is critical to improve outcomes. The nuclear factor-kappaB (NF-κB) is a typical proinflammatory signal transduction pathway identified as a key factor leading to tendon disorders. Therefore, a comprehensive understanding of the mechanism or regulation of NF-κB in tendon disorders will aid in developing targeted therapeutic strategies for human and veterinary tendon disorders. In this review, we discuss what is currently known about molecular components and structures of basal NF-κB proteins and two activation pathways: the canonical activation pathway and the non-canonical activation pathway. Furthermore, we summarize the underlying mechanisms of the NF-κB signaling pathway in fibrosis and adhesion after acute tendon injury, as well as pathological changes of degenerative tendinopathy in all species and highlight the effect of targeting this signaling pathway in tendon disorders. However, to gain a comprehensive understanding of its mechanisms underlying tendon disorders, further investigations are required. In the future, extensive scientific examinations are warranted to full characterize the NF-κB, the exact mechanisms of action, and translate findings into clinical human and veterinary practice.

The Role of p38 Mitogen-Activated Protein Kinase-Mediated F-Actin in the Acupuncture-Induced Mitigation of Inflammatory Pain in Arthritic Rats

The analgesic efficacy of acupuncture has been widely recognized. However, the mechanism by which manual acupuncture-generated mechanical stimuli translate into biological signals remains unclear. This study employed a CFA-induced inflammatory pain rat model. Acupuncture intervention was then performed following standardized procedures. Enzyme-linked immunosorbent assay (ELISA) assessed inflammatory cytokines levels, while immunofluorescence and qRT-PCR screened the level of p38 and F-actin expression in the ST36 acupoint area of rats. Results indicated increased inflammatory factors, including IL-1β and TNFα, with reduced paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) in CFA rats compared to unmodeled rats. After acupuncture intervention, the heightened expression level of F-actin and p38 mRNA and the phosphorylation of p38 in the acupoint area was observed alongside decreased inflammatory factors in diseased ankle joints. The application of lifting and thrusting manipulations further enhanced the effect of acupuncture, in which the molecular expression level of muscle and connective tissue increased most significantly, indicating that these two tissues play a major role in the transformation of acupuncture stimulation. Moreover, antagonizing p38 expression hindered acupuncture efficacy, supporting the hypothesis that p38 MAPK-mediated F-actin transduces mechanical signals generated by acupuncture and related manipulation into biological signals.

Animal model for tendinopathy

Background

Tendinopathy is a common motor system disease that leads to pain and reduced function. Despite its prevalence, our mechanistic understanding is incomplete, leading to limited efficacy of treatment options. Animal models contribute significantly to our understanding of tendinopathy and some therapeutic options. However, the inadequacies of animal models are also evident, largely due to differences in anatomical structure and the complexity of human tendinopathy. Different animal models reproduce different aspects of human tendinopathy and are therefore suitable for different scenarios. This review aims to summarize the existing animal models of tendinopathy and to determine the situations in which each model is appropriate for use, including exploring disease mechanisms and evaluating therapeutic effects.

Methods

We reviewed relevant literature in the PubMed database from January 2000 to December 2022 using the specific terms ((tendinopathy) OR (tendinitis)) AND (model) AND ((mice) OR (rat) OR (rabbit) OR (lapin) OR (dog) OR (canine) OR (sheep) OR (goat) OR (horse) OR (equine) OR (pig) OR (swine) OR (primate)). This review summarized different methods for establishing animal models of tendinopathy and classified them according to the pathogenesis they simulate. We then discussed the advantages and disadvantages of each model, and based on this, identified the situations in which each model was suitable for application.

Results

For studies that aim to study the pathophysiology of tendinopathy, naturally occurring models, treadmill models, subacromial impingement models and metabolic models are ideal. They are closest to the natural process of tendinopathy in humans. For studies that aim to evaluate the efficacy of possible treatments, the selection should be made according to the pathogenesis simulated by the modeling method. Existing tendinopathy models can be classified into six types according to the pathogenesis they simulate: extracellular matrix synthesis-decomposition imbalance, inflammation, oxidative stress, metabolic disorder, traumatism and mechanical load.

Conclusions

The critical factor affecting the translational value of research results is whether the selected model is matched with the research purpose. There is no single optimal model for inducing tendinopathy, and researchers must select the model that is most appropriate for the study they are conducting.

The translational potential of this article

The critical factor affecting the translational value of research results is whether the animal model used is compatible with the research purpose. This paper provides a rationale and practical guide for the establishment and selection of animal models of tendinopathy, which is helpful to improve the clinical transformation ability of existing models and develop new models.

The Effect of Electroacupuncture on Tendon Repair in a Rat Achilles Tendon Rupture Model

Objective

To examine the effect of electroacupuncture (EA) on early post-rupture tendon repair in a rat model of Achilles tendon rupture using histological and mechanical evaluation.

Methods

An Achilles tendon rupture model was prepared in 90 Wistar rats, which were randomly assigned to EA, manual acupuncture or control groups. Rats in the EA group received EA (pulse width 5 ms; stimulation frequency 50 Hz; stimulation strength 20 μA; stimulation time 20 min) daily from 1 day following model preparation until the day of assessment (either 7 or 10 days after model preparation), when the region of interest was sampled to assess tendon repair using in vitro methods. Total cell count and the number of cells staining positive for transforming growth factor-β1 (TGF-β1) and basic fibroblast growth factor (b-FGF) were measured. Tension tests were performed 10 days after model preparation to measure the maximum breaking strength of the repaired tendon.

Results

Both the total cell count and the number of cells positive for b-FGF were significantly higher in the EA group (p<0.05). In the EA group only, immunostaining showed strong expression of TGF-β1 7 days after model preparation (p<0.05). Maximum breaking strength of the repaired tendon 10 days after model preparation was significantly higher in the EA group (p<0.01).

Conclusions

The marked increase in cell count and growth factor expression as well as increased tendon strength in the EA group suggest that EA may be a useful method for promoting tendon repair.

Birefringence of Collagen Fibres in Rat Calcaneal Tendons Treated with Acupuncture during Three Phases of Healing

Background

Birefringence is an optical anisotropy that is investigated by polarisation microscopy, and has been valuable for the study of the oriented organisation of collagen fibres in tendons. However, the application of this technology to evaluate the effect of different acupuncture points during tendon healing has not yet been described.

Objectives

To evaluate the concentration of non-collagenous proteins (NCP) and birefringence in rat calcaneal tendons following injury during the three different phases of healing: inflammatory (7th day), proliferative (14th day), and remodelling (21st day).

Methods

Tendons of 120 Wistar rats were tenotomised and left untreated (teno group, n=24), treated with manual acupuncture at ST36 (ST36 group, n=24), BL57 (BL57 group, n=24) or ST36+BL57 (SB group, n=24), or treated with electroacupuncture at ST36+BL57 (EA group, n=24). Tendon samples were collected at 7, 14 and 21 days after injury (n=8 per group). NCP concentrations were measured using the Bradford method (n=4 each) and birefringence was examined using polarisation microscopy and image analysis (n=4 each). Comparison was also made with healthy (non-tenotomised) tendons in a subgroup of rats (n=4 each).

Results

Manual acupuncture at ST36 and BL57 increased molecular organisation of collagen fibres on day 14 and 21 after injury. Isolated use of BL57 and ST36 also increased collagen fibre organisation when examined on day 14 and 21, respectively. No significant increase in NCP concentration was observed in any of the treated tenotomised groups.

Conclusions

Acupuncture, through putative anti-inflammatory and mechanotransductor effects, may have a role in strengthening tendons and increasing resistance to re-rupture.

Characteristics of Traditional Chinese Medicine Use in Pediatric Dislocations, Sprains and Strains

BACKGROUND AND OBJECTIVES

Dislocations, sprains and strains are common childhood musculoskeletal injuries, requiring medical attention. We investigated the characteristics associated with using traditional Chinese medicine (TCM) for children suffering from these injuries.

METHODS

From a nationwide representative insurance database of Taiwan, this cross-sectional study identified 50,769 children with dislocations, sprains and strains under 18 years of age, newly diagnosed between 1999 and 2009, without previous TCM experience. Children who initiated treatment with TCM (n = 24,063, 47.4%) were defined as TCM users, others were in the non-TCM group. Multivariable logistic regression models estimated odds ratios (ORs) of TCM use.

RESULTS

Girls and children living in central Taiwan (vs. northern) were associated with higher TCM use. The adjusted ORs (95% confidence interval (CI)) of TCM uses were 1.60 (1.42-1.79) for patients of 3-5 years, 2.20 (1.99-2.42) of 6-12 years and 1.82 (1.64-2.01) of 13-17 years, compared with those of the <2 years group. TCM users were less likely to have outpatient visits for Western medicine care and hospitalizations in the previous year. The TCM group was nearly twice more likely than the non-user group to receive treatments at local clinics (99.1% vs. 53.3%, p < 0.001).

CONCLUSIONS

This study reveals important demographic and medical factors associated with TCM uses for children with dislocations, sprains and strains. Interestingly, local clinics are the main healthcare facilities providing TCM services. Further studies are needed to evaluate the outcomes of TCM treatment for these musculoskeletal injuries.

Autonomic Responses to Ultrasound-Guided Percutaneous Needle Electrolysis: Effect of Needle Puncture or Electrical Current?

OBJECTIVE

The aim of this study was to establish if the changes in sympathetic and parasympathetic activity (analyzed through heart-rate variability [HRV]) during ultrasound (US)-guided percutaneous needle electrolysis (PNE) is due to the effect of needle puncture only or of the PNE technique per se where the puncture and galvanic current are combined.

METHODS

This was an experimental, case-control study that took place at the University of Seville. Subjects were 36 male footballers who were randomly allocated to three groups: a control group (CG; 12 players), for whom HRV was recorded for 10 min, both at rest and during an exhaustive US examination of the patellar tendon and adjacent structures; a first experimental group (PNE group; 12 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE in the patellar tendon; and a second experimental group (needle group; 12 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE without electrical current in the patellar tendon. The outcome measures were the diameters of the Poincaré plot (SD1, SD2), stress score, and sympathetic/parasympathetic ratio.

RESULTS

There were no differences between groups in any baseline measurements, nor were there any significant differences between CG measurements (baseline vs. intervention). The PNE group exhibited statistically significant increases in SD1 (p = 0.01) and SD2 (p = 0.004) and statistically significant decreases in SS and S/PS ratio (p = 0.03), indicating increased parasympathetic and decreased sympathetic activity, respectively. The needle group exhibited statistically significant increases in SD2 (p = 0.02) and statistically significant decreases in SS (p = 0.02), indicating decreased sympathetic activity.

CONCLUSIONS

The application of the US-guided PNE technique caused a measurable increase in parasympathetic activity (detected by HRV), which was due to the combination of needle puncture and electric current.

Manipulation Therapy Relieved Pain More Rapidly Than Acupuncture among Lateral Epicondylalgia (Tennis Elbow) Patients: A Randomized Controlled Trial with 8-Week Follow-Up

Radial bone adjustment manipulation treatment may be effective to reduce pain rapidly in lateral epicondylalgia patients and the pathological tension in the biceps brachii muscle is highly concerned. To prove this hypothesis, we conducted a randomized controlled trial and included 35 patients with lateral epicondylalgia for more than 2 months. Either manipulation treatment (n = 16) or acupuncture (n = 19) was given to these patients for 2 weeks and all patients' symptoms were followed up for 8 weeks after treatment. Both groups demonstrated changes in pain VAS score, grip strength, and DASH questionnaire. Lateral epicondylalgia patients who received manipulation treatment felt pain relief sooner than those who had acupuncture treatments during the first few treatments. However, both acupuncture and manipulation are effective, while the difference has no significance at the 8-week follow-up. The trial was registered with Current Controlled Trials ISRCTN81308551 on 5 February 2016.

Autonomic responses to ultrasound-guided percutaneous needle electrolysis of the patellar tendon in healthy male footballers

BACKGROUND

Ultrasound (US)-guided percutaneous needle electrolysis (PNE) is a novel minimally invasive approach, which involves the application of a galvanic current via an acupuncture needle. As in any procedure involving needling, vagal reactions have been reported during PNE.

OBJECTIVE

To examine for changes in autonomic activity during the US-guided PNE technique on healthy patellar tendons by measurement and analysis of heart rate variability (HRV).

METHODS

Twenty-two male footballers were randomly allocated to: a control group (11 players), for whom HRV was recorded for 10 min, both at rest and during an exhaustive US examination of the patellar tendon and adjacent structures; and an experimental group (11 players), for whom HRV was recorded for 10 min, both at rest and during application of US-guided PNE on the patellar tendon. The following HRV parameters were assessed: mean NN interval, mean heart rate, time domain parameters (SDNN, rMSSD, pNN50), diameters of the Poincaré plot (SD1, SD2), stress score, and sympathetic/parasympathetic ratio.

RESULTS

There were no differences between groups in any baseline measurements, nor were there any significant differences between control group measurements (baseline vs intervention). The experimental group exhibited statistically significant increases in SDNN/SD1 (p=0.02/p=0.03) and SD2 (p=0.03), indicating increased parasympathetic and decreased sympathetic activity, respectively.

CONCLUSIONS

US-guided PNE was associated with an autonomic imbalance characterised by greater parasympathetic activity, which could potentially result in a vasovagal reaction. Care should be taken to monitor for adverse reactions during US-guided PNE and simple HRV indicators may have a role in early detection.

Acupuncture Increases the Diameter and Reorganisation of Collagen Fibrils during Rat Tendon Healing

Background

Our previous study showed that electroacupuncture (EA) increases the concentration and reorganisation of collagen in a rat model of tendon healing. However, the ultrastructure of collagen fibrils after acupuncture is unknown.

Objectives

To assess the effect of acupuncture protocols on the ultrastructure of collagen fibrils during tendon healing.

Methods

Sixty-four rats were divided into the following groups: non-tenotomised (normal group), tenotomised (teno group), tenotomised and subjected to manual acupuncture at ST36 (ST36 group), BL57 (BL57 group) and ST36+BL57 (SB group) and EA at ST36+BL57 (EA group). The mass-average diameter (MAD) and the reorganisation of collagen fibril diameters were determined during the three phases of tendon healing (at 7, 14 and 21 days).

Results

The MAD increased during the three phases of healing in the SB group. In the EA group, MAD increased initially but was reduced at day 21. The reorganisation of collagen fibrils was improved in the EA and SB groups at days 14 and 21, respectively. EA at day 21 appeared to reduce the reorganisation.

Conclusions

These results indicate that the use of EA up to day 14 and manual acupuncture at ST36+BL57 up to day 21 improve the ultrastructure of collagen fibrils, indicating strengthening of the tendon structure. These data suggest a potential role for acupuncture in rehabilitation protocols.

Ultrasound-guided percutaneous needle electrolysis in chronic lateral epicondylitis: short-term and long-term results

BACKGROUND

Ultrasound (US)-guided percutaneous needle electrolysis (PNE) is a novel minimally invasive approach which consists of the application of a galvanic current through an acupuncture needle.

OBJECTIVE

To evaluate the clinical and ultrasonographic effectiveness of a multimodal programme (PNE, eccentric exercise (EccEx) and stretching) in the short term for patients with chronic lateral epicondylitis, and to determine whether the clinical outcomes achieved decline over time.

METHODS

A one-way repeated measures study was performed in a clinical setting in 36 patients presenting with lateral epicondylitis. The patients received one session of US-guided PNE per week over 4-6 weeks, associated with a home programme of EccEx and stretching. The main outcome measures were severity of pain, disability (Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire), structural tendon changes (US), hypervascularity and patients' perceptions of overall outcome. Measurements at 6, 26 and 52 weeks follow-up included recurrence rates (increase in severity of pain or disability compared with discharge), perception of overall outcome and success rates.

RESULTS

All outcome measures registered significant improvements between pre-intervention and discharge. Most patients (n=30, 83.3%) rated the overall outcome as 'successful' at 6 weeks. The ultrasonographic findings showed that the hypoechoic regions and hypervascularity of the extensor carpi radialis brevis changed significantly. At 26 and 52 weeks, all participants (n=32) perceived a 'successful' outcome. Recurrence rates were null after discharge and at follow-up at 6, 26 and 52 weeks.

CONCLUSIONS

Symptoms and degenerative structural changes of chronic lateral epicondylitis are reduced after US-guided PNE associated with EccEx and stretching, with encouragingly low recurrences in the mid to long term.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier: NCT02085928.