Overexpression of nitric oxide synthases in tendon overuse

Rotator Cuff Tendinopathy: Pathways of Apoptosis

Rotator cuff repair is usually successful, but retear is not uncommon. It has been previously identified that there is a higher incidence of apoptosis in the edges of the torn supraspinatus tendon. A prospective cohort study was conducted with 28 patients-14 rotator cuff tear patients, 5 instability patients, and 9 Anterior cruciate ligament reconstruction patients to determine whether there was any increase in several genes implicated in apoptosis, including Fas receptor (FasR), Fas ligand, Aifm-1, Bcl-2, Fadd, Bax, and caspase-3. There was a significant expression of Bax (P=0.2) and FasR (P=0.005) in the edges of torn supraspinatus tendons, and in intact subscapularis tendons, there was a significant expression of caspase-3 (P=0.02) compared with samples from the torn supraspinatus tendon (P=0.04). The cytochrome c pathway, with its subsequent activation of caspase-3, as well as the TRAIL-receptor signaling pathway involving FasR have both been implicated. The elevated expression of Bax supported the model that the Bax to Bcl-2 expression ratio represents a cell death switch. The elevated expression of Bax in the intact subscapularis tissue from rotator cuff tear patients also may confirm that tendinopathy is an ongoing molecular process.

Shoulder Intra-Articular Temperature Is Higher In Patients With Small Rotator Cuff Tears Compared With Patients Who Have Larger Tears

Purpose

The purpose of this study was to determine whether the intra-articular temperature of the shoulder correlates with the size of the tendon tear in patients with rotator cuff tears (RCTs).

Methods

The shoulder intra-articular temperature of 75 consecutive (32 female, 43 male; mean age 61.12; standard deviation = 7.10) patients who underwent arthroscopic rotator cuff repair was measured with a digital thermometer, at first in 2 points (biceps anchor and glenoid labrum) during dry arthroscopy, followed by a third measurement during wet arthroscopy. A fourth measurement, represented by the patient's axillary body temperature, was taken upon admission. The RCTs were classified during surgery according to the Southern California Orthopedic Institute classification system as small, large, and massive. Data were submitted for statistical analysis.

Results

The intra-articular temperature differs in patients with different-sized RCTs regardless of the location of the thermometer. A significantly higher temperature was found in patients with small RCTs (36.2°C ± 0.57°C) (P < .01). When the in-flow of the arthroscopic fluid was opened, the temperature dropped to an average of 24.5°C.

Conclusions

The shoulder intra-articular temperature was significantly associated with RCT size. A significantly higher temperature was found in small RCTs. No correlation was found between age and sex, age and RCT size, sex and RCT size, or sex and temperature.

Clinical Relevance

An early diagnosis and treatment of RCTs may avoid further degeneration and damage of the tendon caused by the increased temperature.

Tendinopathy and tendon material response to load: What we can learn from small animal studies

Tendinopathy is a debilitating disease that causes as much as 30% of all musculoskeletal consultations. Existing treatments for tendinopathy have variable efficacy, possibly due to incomplete characterization of the underlying pathophysiology. Mechanical load can have both beneficial and detrimental effects on tendon, as the overall tendon response depends on the degree, frequency, timing, and magnitude of the load. The clinical continuum model of tendinopathy offers insight into the late stages of tendinopathy, but it does not capture the subclinical tendinopathic changes that begin before pain or loss of function. Small animal models that use high tendon loading to mimic human tendinopathy may be able to fill this knowledge gap. The goal of this review is to summarize the insights from in-vivo animal studies of mechanically-induced tendinopathy and higher loading regimens into the mechanical, microstructural, and biological features that help characterize the continuum between normal tendon and tendinopathy. STATEMENT OF SIGNIFICANCE: This review summarizes the insights gained from in-vivo animal studies of mechanically-induced tendinopathy by evaluating the effect high loading regimens have on the mechanical, structural, and biological features of tendinopathy. A better understanding of the interplay between these realms could lead to improved patient management, especially in the presence of painful tendon.

Prospects for the Personalized Multimodal Therapy Approach to Pain Management via Action on NO and NOS

Chronic pain syndromes are an important medical problem generated by various molecular, genetic, and pathophysiologic mechanisms. Back pain, neuropathic pain, and posttraumatic pain are the most important pathological processes associated with chronic pain in adults. Standard approaches to the treatment of them do not solve the problem of pain chronicity. This is the reason for the search for new personalized strategies for the prevention and treatment of chronic pain. The nitric oxide (NO) system can play one of the key roles in the development of peripheral pain and its chronicity. The purpose of the study is to review publications devoted to changes in the NO system in patients with peripheral chronical pain syndromes. We have carried out a search for the articles published in e-Library, PubMed, Oxford Press, Clinical Case, Springer, Elsevier, and Google Scholar databases. The search was carried out using keywords and their combinations. The role of NO and NO synthases (NOS) isoforms in peripheral pain development and chronicity was demonstrated primarily from animal models to humans. The most studied is the neuronal NOS (nNOS). The role of inducible NOS (iNOS) and endothelial NOS (eNOS) is still under investigation. Associative genetic studies have shown that single nucleotide variants (SNVs) of NOS1, NOS2, and NOS3 genes encoding nNOS, iNOS, and eNOS may be associated with acute and chronic peripheral pain. Prospects for the use of NOS inhibitors to modulate the effect of drugs used to treat peripheral pain syndrome are discussed. Associative genetic studies of SNVs NOS1, NOS2, and NOS3 genes are important for understanding genetic predictors of peripheral pain chronicity and development of new personalized pharmacotherapy strategies.

Metabolic and inflammatory links to rotator cuff tear in hand osteoarthritis: A cross sectional study

Objectives

To estimate the prevalence and associated factors of rotator cuff tear (RCT) in patients with hand osteoarthritis (HOA).

Methods

Between June 2013 and December 2015, we recruited 1150 participants in rural area of South Korea. Of the 1150 participants, 307 participants with HOA were analyzed. Plain radiography of both hands, magnetic resonance imaging of both shoulders, and serum levels of high-sensitive C-reactive protein (hsCRP) and high-density lipoprotein (HDL) were obtained for all patients. HOA and RCT were diagnosed by clinical and radiologic findings.

Results

The prevalence of RCT in patients with HOA (192/307, 62.5%) was higher than that in those without HOA (410/827, 49.5%, p<0.001). Among the 307 patients with HOA, the patients with RCT were older, and had higher hsCRP and lower HDL levels than the patients without RCT. Multiple logistic regression analysis confirmed significant associations of age (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.02–1.11), serum hsCRP levels ≥0.6mg/L (OR, 1.68; CI, 1.00–2.80), and low HDL levels (male, <50 mg/dL; female, <40 mg/dL) (OR, 1.93; CI, 1.05–3.56) with RCT in patients with HOA. For patients below 60 years old, the prevalence of RCT was 2.8-fold higher in the low HDL group than normal HDL group (p = 0.048). Finally, the prevalence of RCT was 2.6-fold higher in patients with HOA with both elevated hsCRP and low HDL levels compared with those with neither (p<0.05).

Conclusions

Our findings suggest inflammation and metabolic factors were associated with the prevalence of RCT in HOA patients.

Risk Factors for Rotator Cuff Disease: An Experimental Study on Intact Human Subscapularis Tendons

Although several studies revealed a multifactorial pathogenesis of degenerative rotator cuff disorders, the impact and interaction of extrinsic variables is still poorly understood. Thus, this study aimed at uncovering the effect of patient- and pathology-specific risk factors that may contribute to degeneration of the rotator cuff tendons. Between 2015 and 2018, 54 patients who underwent arthroscopic shoulder surgery at three specialized shoulder clinics were prospectively included. Using tendon samples harvested from the macroscopically intact subscapularis (SSC) tendon, targeted messenger RNA expression profile analysis was performed in the first cohort (n = 38). Furthermore, histological analyses were conducted on tendon tissue samples obtained from a second cohort (n = 16). Overall, both study cohorts were comparable concerning patient demographics. Results were then analyzed with respect to specific extrinsic factors, such as patient age, body mass index, current as well as previous professions and sport activities, smoking habit, and systemic metabolic diseases. While patient age, sports-activity level, and preexisting rotator cuff lesions were considered to contribute most strongly to tendinopathogenesis, no further coherences were found. With regards to gene expression analysis, change in expression correlated most strongly with patient age and severity of the rotator cuff pathology. Further, chronic disorders increased overall gene expression variation. Taken together, our study provides further evidence that tendon degeneration is the consequence of a multifactorial process and pathological changes of the supraspinatus tendon affect the quality of SSC tendon and most likely vice versa. Therefore, the rotator cuff tendons need to be considered as a unit when managing rotator cuff pathologies. © 2019 The Authors. Journal of Orthopaedic Research^® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 38:182-191, 2020.

Immunohistochemical features of rotator cuff tendinopathy

BACKGROUND

Rotator cuff tendinopathy is a common musculoskeletal ailment in sedentary and athletic individuals. Various mediators of inflammation have been detected in human tendons: they are thought to initiate or progress the course of tendinopathy.

SOURCES OF DATA

An online search was conducted using AMED, CINAHL, Embase, The Cochrane Library, PEDro and Pubmed, using the terms tendinopathy, tendon, tendinitis, tendinosis, histology, histopathology, immunohistochemistry, immunohistochemical, rotator cuff and pain.

AREAS OF AGREEMENT

Histological examination of tendinopathic tendons shows degeneration of the collagen structure and infiltration of fat and vessels, together with increased expression of inflammatory cytokines, MMP-1, 2, 3, 9, 13, vascular endothelial growth factor and Hypoxia inducible factor (HIF).

AREAS OF CONTROVERSY

Most of the studies about this topic exhibited limited validity because of lack of appropriately matched controls and no inclusion or exclusion criteria. The evidence associated with the histopathological analysis of the rotator cuff is limited.

GROWING POINTS

The histochemical and immunohistochemical features of rotator cuff tendinopathy are still unclear. A thorough understanding of the vascularity, innervation and biochemical mediators of pain could be used to target rotator cuff pathology, and possibly guide the therapy of painful rotator cuff disorders.

AREAS TIMELY FOR DEVELOPING RESEARCH

There is a need for a validated reproducible method of rotator cuff tendon biopsy evaluation. We require further studies with improved designs to effectively evaluate the histological and immunohistochemical features of rotator cuff tendinopathy.

The Evaluation of Exogenous Melatonin Administration in Supraspinatus Overuse Tendinopathy in an Experimental Rat Model

Background

Increased oxidative stress and inflammation play a critical role in the etiopathogenesis of chronic tendinopathy. Melatonin is an endogenous molecule that exhibits antioxidant and anti-inflammatory activity. The aim of this study was to evaluate the biochemical and histopathological effects of exogenous melatonin administrations in supraspinatus overuse tendinopathy.

Methods

Fifty rats were divided into the following four groups: cage activity, melatonin treatment, corticosteriod therapy, and control. Melatonin (10 mg/kg, intraperitoneal; twice a day) and triamcinolone (0.3 mg/kg, subacromial; weekly) were administered to the treatment groups after the overuse period. Biochemical and histopathological evaluations were performed on serum samples and biopsies obtained from rats. Plasma inducible nitric oxide synthase (iNOS), vascular endothelial growth factor (VEGF), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) levels were evaluated biochemically.

Results

The TAS, TOS, OSI, iNOS, and VEGF values were significantly lower than the pre-treatment levels in rats receiving exogenous melatonin treatment (3 or 6 weeks) (p<0.05). TOS, iNOS, VEGF, and OSI values after 3 weeks of triamcinolone administration, and TOS, VEGF, and OSI levels after 6 weeks of triamcinolone application, were significantly lower than the pre-treatment levels (p<0.05).

Conclusions

Exogenous melatonin application in overuse tendinopathy reduces oxidative stress and inflammation. Melatonin might be an alternative potential molecule to corticosteroids in the treatment of chronic tendinopathy.

KDR inferred haplotype is associated with upper limb dysfunction in breast cancer survivors of mixed ancestry

Introduction: Shoulder pain and disability are well-documented sequelae of breast cancer treatment. Angiogenesis signaling may have a role in the development of shoulder pain or shoulder disability in breast cancer survivors. The aim of this study was to determine if polymorphisms in angiogenesis-related genes are associated with shoulder pain or disability following breast cancer treatment.

Participants and methods: A cross-sectional study was conducted on 220 South African breast cancer survivors. The study aimed to evaluate associations between shoulder pain/disability and seven single nucleotide polymorphisms (SNPs) within five angiogenesis-associated genes: KDR (rs2305948 C>T; rs7667298 C>T), NOS3 (rs1549758 C>T), MMP2 (rs708269 A>T), THBS2 (rs9766678 A>G) and TIMP3 (rs5754312 T>A; rs715572 G>A). In addition, associations between shoulder pain/disability and inferred haplotypes for KDR and TIMP3 SNPs were evaluated. Participants were grouped into no–low and moderate–high shoulder pain/disability based on total pain/disability scores: ≤30 and >30, respectively using the shoulder pain and disability index (SPADI).

Results: No independent associations with shoulder pain/disability categories were found for all SNPs. However, 1 inferred haplotype (KDR “TT”) differed significantly (P=0.014) between the shoulder disability categories. After adjusting for participants’ age, the differences in KDR inferred haplotype frequencies between shoulder disability categories became non-significant (P=0.052).

Conclusion: Our findings provide a preliminary suggestion of a possible association between polymorphisms in genes involved in angiogenesis and the presence of moderate–high shoulder disability among South African breast cancer survivors. A larger prospective cohort study is currently being conducted by our group.

Rotator Cuff Degeneration: The Role of Genetics

BACKGROUND

The literature is certain regarding the multifactorial etiology of rotator cuff degeneration. However, it remains unclear if rotator cuff degeneration exclusively depends on intrinsic and extrinsic factors or if it is also genetically determined. We compared the health status of cuff tendons, evaluated with a magnetic resonance imaging (MRI) study, between elderly monozygotic and dizygotic twins with the aim of separating the contributions of genetics from shared and unique environments.

METHODS

The rotator cuff tendon status was assessed using the Sugaya classification by MRI. Heritability, defined as the proportion of total variance of a specific characteristic in a particular population due to a genetic cause, was calculated as twice the difference between the intraclass correlation coefficients for monozygotic and dizygotic pairs. The influence of shared environment, which contributes to twin and sibling similarity, was calculated as the difference between the monozygotic correlation coefficient and the heritability index.

RESULTS

We identified 33 pairs of elderly twins: 17 monozygotic pairs and 16 dizygotic pairs, with a mean age (and standard deviation) of 64.62 ± 3.32 years. The polychoric correlation was 0.62 in monozygotic twins and 0.53 in dizygotic twins. The calculated heritability index was 0.18 (18%), and the contribution was 0.44 (44%) for the shared environment and 0.38 (38%) for the unique environment.

CONCLUSIONS

The role of genetics in rotator cuff degeneration is quantified by our study on elderly monozygotic and dizygotic twins; however, it is only partial with respect to the contribution of shared and unique environments.

Development of an Injectable Nitric Oxide Releasing Poly(ethylene) Glycol-Fibrin Adhesive Hydrogel

Fibrin microparticles were incorporated into poly(ethylene) glycol (PEG)-fibrinogen hydrogels to create an injectable, composite that could serve as a wound healing support and vehicle to deliver therapeutic factors for tissue engineering. Nitric oxide (NO), a therapeutic agent in wound healing, was loaded into fibrin microparticles by blending S-Nitroso-N-acetyl penicillamine (SNAP) with a fibrinogen solution. The incorporation of microparticles affected swelling behavior and improved tissue adhesivity of composite hydrogels. Controlled NO release was induced via photolytic and thermal activation, and modulated by weight percent of particles incorporated. These NO-releasing composites were non-cytotoxic in culture. Cells maintained morphology, viability, and proliferative character. Fibrin microparticles loaded with SNAP and incorporated into a PEG-fibrinogen matrix, creates a novel injectable composite hydrogel that offers improved tissue adhesivity and inducible NO-release for use as a regenerative support for wound healing and tissue engineering applications.

Overuse injuries in sport: a comprehensive overview

BACKGROUND

The absence of a single, identifiable traumatic cause has been traditionally used as a definition for a causative factor of overuse injury. Excessive loading, insufficient recovery, and underpreparedness can increase injury risk by exposing athletes to relatively large changes in load. The musculoskeletal system, if subjected to excessive stress, can suffer from various types of overuse injuries which may affect the bone, muscles, tendons, and ligaments.

METHODS

We performed a search (up to March 2018) in the PubMed and Scopus electronic databases to identify the available scientific articles about the pathophysiology and the incidence of overuse sport injuries. For the purposes of our review, we used several combinations of the following keywords: overuse, injury, tendon, tendinopathy, stress fracture, stress reaction, and juvenile osteochondritis dissecans.

RESULTS

Overuse tendinopathy induces in the tendon pain and swelling with associated decreased tolerance to exercise and various types of tendon degeneration. Poor training technique and a variety of risk factors may predispose athletes to stress reactions that may be interpreted as possible precursors of stress fractures. A frequent cause of pain in adolescents is juvenile osteochondritis dissecans (JOCD), which is characterized by delamination and localized necrosis of the subchondral bone, with or without the involvement of articular cartilage. The purpose of this compressive review is to give an overview of overuse injuries in sport by describing the theoretical foundations of these conditions that may predispose to the development of tendinopathy, stress fractures, stress reactions, and juvenile osteochondritis dissecans and the implication that these pathologies may have in their management.

CONCLUSIONS

Further research is required to improve our knowledge on tendon and bone healing, enabling specific treatment strategies to be developed for the management of overuse injuries.

Streptozotocin-induced diabetes alters transcription of multiple genes necessary for extracellular matrix remodeling in rat patellar tendon

OVERVIEW

Tendon collagen fibril degradation is commonly seen in tendons of diabetics, but the mechanisms responsible for these changes remain to be elucidated. We have demonstrated that streptozotocin (STZ)-induced diabetes increases tendon cell proliferation and collagen content. In the present study, we evaluated that impact of STZ-induced diabetes on mRNA transcripts involved with collagen fibril organization, extracellular matrix (ECM) remodeling, apoptosis, and proliferation.

MATERIALS AND METHODS

Rats were divided into four groups: nondiabetic (control, n = 9), 1 week (acute, n = 8) or 10 weeks of diabetes (chronic, n = 7), and 10 weeks of diabetes with insulin (insulin, n = 8). RNA was isolated from the patellar tendon for determination of mRNA transcripts using droplet digital PCR (ddPCR).

RESULTS

Transcripts for Col1a1, Col3a1, Mmp2, Timp1, Scx, Tnmd, Casp3, Casp8, and Ager were lower in acute relative to control and insulin rats (p ≤ 0.05). With the exception of Scx, transcripts for Col1a1, Col3a1, Mmp2, Timp1, Tnmd, Casp3, Casp8, and Ager were also lower in chronic when compared to control (p < 0.05). Transcripts for Col1a1, Col3a1, Mmp2, Timp1, Tnmd, Casp3, Casp8, and Ager were not different between control and insulin (p > 0.05). Transcripts for Dcn, Mmp1a, Mmp9, Pcna, Tgfbr3, Ptgs2, Ptger2, Ptges, and iNos were not altered by diabetes or insulin (p > 0.05).

CONCLUSION

Our findings indicated that STZ-induced diabetes results in rapid and large changes in the expression of several genes that are key to ECM remodeling, maintenance, and maturation.

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

BACKGROUND

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

PURPOSE

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

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

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

RESULTS

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

CONCLUSION

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

Rescue plan for Achilles: Therapeutics steering the fate and functions of stem cells in tendon wound healing

Due to the increasing age of our society and a rise in engagement of young people in extreme and/or competitive sports, both tendinopathies and tendon ruptures present a clinical and financial challenge. Tendon has limited natural healing capacity and often responds poorly to treatments, hence it requires prolonged rehabilitation in most cases. Till today, none of the therapeutic options has provided successful long-term solutions, meaning that repaired tendons do not recover their complete strength and functionality. Our understanding of tendon biology and healing increases only slowly and the development of new treatment options is insufficient. In this review, following discussion on tendon structure, healing and the clinical relevance of tendon injury, we aim to elucidate the role of stem cells in tendon healing and discuss new possibilities to enhance stem cell treatment of injured tendon. To date, studies mainly apply stem cells, often in combination with scaffolds or growth factors, to surgically created tendon defects. Deeper understanding of how stem cells and vasculature in the healing tendon react to growth factors, common drugs used to treat injured tendons and promising cellular boosters could help to develop new and more efficient ways to manage tendon injuries.

Rotator cuff degeneration of the healthy shoulder in patients with unilateral arm amputation is not worsened by overuse

PURPOSE

In order to evaluate whether overuse has a significant role in rotator cuff tear (RCT) aetiology, we evaluated both shoulders of patients with old unilateral arm amputation expecting a higher rate of RC degeneration in the healthy side.

METHODS

Nineteen males and six females (mean age: 57.3 ± 10.1) with an old (>20 years) unilateral arm amputation were submitted to an MRI of both shoulders. Tendon status and muscle tropism were evaluated according to Sugaya and Fuchs classifications, respectively; the acromion humeral distance was measured. Statistical analysis was performed to verify the prevalence of Sugaya and Fuchs categories in each sides.

RESULTS

A significant prevalence of Sugaya type II in the amputated side (p = 0.02) and of type I in the healthy side (p < 0.001) was found. Rotator cuff was healthy in 28 and 52% of amputated and non-amputated side, respectively. The mean acromio-humeral distances of the amputated and healthy side were 0.8 cm (SD: 0.1) and 0.9 cm (SD: 0.1), respectively, (p = 0.02). A significant prevalence of Fuchs type II category in the healthy side (p < 0.001) was found. Fuchs III/IV were observed in 40 and 12% of amputated and healthy side, respectively.

CONCLUSIONS

The present study resizes the role of overuse on the aetiology of RCT. Cuff tear prevalence in not amputated shoulders, inevitably submitted to functional overload, was not higher than that of coetaneous subjects with two functional upper limbs. Shoulder non-use is a risk factor for rotator cuff tear. As the prevalence of rotator cuff degeneration/tear is higher in the amputee side, non-use is a more relevant risk factor than overuse. In the daily clinical practice, patients with rotator cuff tear should be encouraged to shoulder movement because rotator cuff tendon status could be worsened by disuse.

LEVEL OF EVIDENCE

III.

Subacromial Space Width: Does Overuse or Genetics Play a Greater Role in Determining It? An MRI Study on Elderly Twins

BACKGROUND

Age and peripheral microcirculation disorders are the main causes of rotator cuff degeneration. Acromion variants may affect subacromial space width, causing a pathological narrowing of the space that may compromise the cuff integrity. However, it is not clear if the subacromial space width is genetically determined or if it changes according to loading conditions. To clarify this unresolved question, we performed an MRI (magnetic resonance imaging) study with the aim of evaluating the acromiohumeral distance in a group of elderly monozygotic and dizygotic twins, and we analyzed the obtained data using the twin design to separate the contributions of shared and unique environments.

METHODS

We identified twenty-nine pairs of elderly twins. On MRI scans, we evaluated the acromiohumeral distance and health status of the rotator cuff tendons. Heritability, defined as the proportion of total variance of a specific characteristic in a particular population due to a genetic cause, was estimated as twice the difference between the intraclass correlation coefficients for monozygotic and dizygotic pairs. The influence of shared environment, due to environmental factors that contribute to twin and sibling similarity, was calculated as the difference between the monozygotic correlation coefficient and the heritability index. One-way ANOVA (analysis of variance) was used to estimate the differences among job categories, both in the total cohort and within zygosity groups.

RESULTS

The intraclass correlation coefficient was substantially higher for monozygotic than for dizygotic twins, indicating a high degree of concordance of the acromiohumeral distance in pairs of individuals who shared 100% of their genes. The heritability index was 0.82, and shared and unique environmental contributions were both 0.09. There were no significant differences among subjects in different job categories, either in the total cohort (p = 0.685) or within the monozygotic (p = 0.719) and dizygotic groups (p = 0.957).

CONCLUSIONS

The acromiohumeral distance is mainly genetically determined and only marginally influenced by external factors.

Genetic Response of Rat Supraspinatus Tendon and Muscle to Exercise

Inflammation is a complex, biologic event that aims to protect and repair tissue. Previous studies suggest that inflammation is critical to induce a healing response following acute injury; however, whether similar inflammatory responses occur as a result of beneficial, non-injurious loading is unknown. The objective of this study was to screen for alterations in a subset of inflammatory and extracellular matrix genes to identify the responses of rat supraspinatus tendon and muscle to a known, non-injurious loading condition. We sought to define how a subset of genes representative of specific inflammation and matrix turnover pathways is altered in supraspinatus tendon and muscle 1) acutely following a single loading bout and 2) chronically following repeated loading bouts. In this study, Sprague-Dawley rats in the acute group ran a single bout of non-injurious exercise on a flat treadmill (10 m/min, 1 hour) and were sacrificed 12 or 24 hours after. Rats in the chronic group ran 5 days/wk for 1 or 8 weeks. A control group maintained normal cage activity. Supraspinatus muscle and tendon were harvested for RNA extractions, and a custom Panomics QuantiGene 2.0 multiplex assay was used to detect 48 target and 3 housekeeping genes. Muscle/tendon and acute/chronic groups had distinct gene expression. Components of the arachidonic acid cascade and matrix metalloproteinases and their inhibitors were altered with acute and chronic exercise. Collagen expression increased. Using a previously validated model of non-injurious exercise, we have shown that supraspinatus tendon and muscle respond to acute and chronic exercise by regulating inflammatory- and matrix turnover-related genes, suggesting that these pathways are involved in the beneficial adaptations to exercise.

The pathogenesis of Achilles tendinopathy: a systematic review

Achilles tendinopathy is a degenerative, not an inflammatory, condition. It is prevalent in athletes involved in running sports. A systematic literature review on Achilles tendon tendinopathy has been performed according to the intrinsic (age, sex, body weight, tendon temperature, systemic diseases, muscle strength, flexibility, previous injuries and anatomical variants, genetic predisposition and blood supply) and extrinsic risk factors (drugs and overuse), which can cause tendon suffering and degeneration. Different theories have been found: Neurogenic, Angiogenic, Impingement and "Iceberg" Hypotheses. Multiple databases were utilized for articles published between 1964 and 2013. The different hypothesis were analyzed, differently considering those concerning the pathogenesis of tendinopathy and those concerning the etiology of complaints in patients. This review of the literature demonstrates the heterogeneity of Achilles tendinopathy pathogenesis. Various risk factors have been identified and have shown an interaction between them such as genes, age, circulating and local cytokine production, sex, biomechanics and body composition.

Endothelial dysfunction and tendinopathy: how far have we come?

Symptomatic tendon tears are one of the most important causes of pain and joint dysfunction. Among the intrinsic causes, vascularization recently gained a major role. Endothelial function is indeed a key factor, as well as vascular tone and thrombotic factors, in the regulation of vascular homeostasis and the composition of vascular wall. In this review, we studied systematically whether there is a relationship between endothelial dysfunction and tendinopathy. A literature search was performed using the isolated or combined keywords endothelial dysfunction and tendon,' 'nitric oxide (NO) and tendinopathy,' and 'endothelial dysfunction in tendon healing.' We identified 21 published studies. Of the selected studies, 9 were in vivo studies, 2 focusing on animals and 7 on humans, while 12 reported about in vitro evaluations, where 7 were carried out on humans and 5 on animals. The evidence about a direct relationship between tendinopathy and endothelial dysfunction is still poor. As recent studies have shown, there is no significant improvement in clinical and functional assessments after treatment with NO in patients suffering from tendinopathy in different locations. No significant differences were identified in the outcomes reported for experiment group when compared with controls treated with conventional surgical procedures or rehabilitation programs. Nitric oxide could be a marker to quantify the response of the endothelium to mechanical stress or hypoxia indicating the final balance between vasodilatating and vasoconstricting factors and their effects, but more ad stronger evidence is still needed to fully support this practice.

Healing of subcutaneous tendons: Influence of the mechanical environment at the suture line on the healing process

Tendon ruptures remain a significant musculoskeletal injury. Despite advances in surgical techniques and procedures, traditional repair techniques maintain a high incidence of rerupture or tendon elongation. Mechanical loading and biochemical signaling both control tissue healing. This has led some researchers to consider using a technique based on tension regulation at the suture line for obtaining good healing. However, it is unknown how they interact and to what extent mechanics control biochemistry. This review will open the way for understanding the interplay between mechanical loading and the process of tendon healing.

Experimental diabetes induces structural, inflammatory and vascular changes of Achilles tendons

This study aims to demonstrate how the state of chronic hyperglycemia from experimental Diabetes Mellitus can influence the homeostatic imbalance of tendons and, consequently, lead to the characteristics of tendinopathy. Twenty animals were randomly divided into two experimental groups: control group, consisting of healthy rats and diabetic group constituted by rats induced to Diabetes Mellitus I. After twenty-four days of the induction of Diabetes type I, the Achilles tendon were removed for morphological evaluation, cellularity, number and cross-sectional area of blood vessel, immunohistochemistry for Collagen type I, VEGF and NF-κB nuclear localization sequence (NLS) and nitrate and nitrite level. The Achilles tendon thickness (µm/100g) of diabetic animals was significantly increased and, similarly, an increase was observed in the density of fibrocytes and mast cells in the tendons of the diabetic group. The average number of blood vessels per field, in peritendinous tissue, was statistically higher in the diabetic group 3.39 (2.98) vessels/field when compared to the control group 0.89 (1.68) vessels/field p = 0.001 and in the intratendinous region, it was observed that blood vessels were extremely rare in the control group 0.035 (0.18) vessels/field and were often present in the tendons of the diabetic group 0.89 (0.99) vessels/field. The immunohistochemistry analysis identified higher density of type 1 collagen and increased expression of VEGF as well as increased immunostaining for NFκB p50 NLS in the nucleus in Achilles tendon of the diabetic group when compared to the control group. Higher levels of nitrite/nitrate were observed in the experimental group induced to diabetes. We conclude that experimental DM induces notable structural, inflammatory and vascular changes in the Achilles tendon which are compatible with the process of chronic tendinopathy.

Local NO synthase inhibition produces histological and functional recovery in Achilles tendon of rats after tenotomy: tendon repair and local NOS inhibition

Repair of injured tendon is a very slow process and involves the release of many molecules, including nitric oxide. We investigate the influence of local nitrergic inhibition in histological and functional recovery of injured Achilles tendon. A standard murine model of tendon injury by rupture was used. The animals were divided into three experimental groups: control, injury + vehicle (normal saline) and injury + Nω-nitro-L-arginine methyl ester (L-NAME). The products were injected into the paratendinous region every 2 days and body weight gain and Achilles functional index (AFI) were evaluated on days 0, 7, 14 and 21 after tendon injury. On day 21 post-injury, the animals were killed to evaluate nitric oxide production and tissue organization. We observed that tendon surgical division led to increased tissue nitrite levels, which were reduced in L-NAME-treated rats. The AFI revealed functional recovery of L-NAME-treated animals on day 21 post-injury, which was not observed in the saline-treated group. Microscopic analysis of hematoxylin-eosin staining and collagen autofluorescence showed that L-NAME-treated rats had more aligned areas of collagen fibers and that the diameter of newly organized collagen in this group was also greater than that in the vehicle-treated one. We demonstrate that local treatment with L-NAME significantly improves the functional parameters and accelerates histomorphological recovery.

Oxygen consumption and usage during physical exercise: the balance between oxidative stress and ROS-dependent adaptive signaling

The complexity of human DNA has been affected by aerobic metabolism, including endurance exercise and oxygen toxicity. Aerobic endurance exercise could play an important role in the evolution of Homo sapiens, and oxygen was not important just for survival, but it was crucial to redox-mediated adaptation. The metabolic challenge during physical exercise results in an elevated generation of reactive oxygen species (ROS) that are important modulators of muscle contraction, antioxidant protection, and oxidative damage repair, which at moderate levels generate physiological responses. Several factors of mitochondrial biogenesis, such as peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitogen-activated protein kinase, and SIRT1, are modulated by exercise-associated changes in the redox milieu. PGC-1α activation could result in decreased oxidative challenge, either by upregulation of antioxidant enzymes and/or by an increased number of mitochondria that allows lower levels of respiratory activity for the same degree of ATP generation. Endogenous thiol antioxidants glutathione and thioredoxin are modulated with high oxygen consumption and ROS generation during physical exercise, controlling cellular function through redox-sensitive signaling and protein-protein interactions. Endurance exercise-related angiogenesis, up to a significant degree, is regulated by ROS-mediated activation of hypoxia-inducible factor 1α. Moreover, the exercise-associated ROS production could be important to DNA methylation and post-translation modifications of histone residues, which create heritable adaptive conditions based on epigenetic features of chromosomes. Accumulating data indicate that exercise with moderate intensity has systemic and complex health-promoting effects, which undoubtedly involve regulation of redox homeostasis and signaling.

The apoptosis pathway and the genetic predisposition to Achilles tendinopathy

Achilles tendinopathy (AT) is a degenerative condition for which several risk factors have been implicated including components of the inflammatory pathway. The aim was to assess functional variants within genes encoding components of the apoptosis signaling cascade and the effectiveness of a polygenic apoptosis profile to capture tendinopathy (TEN) risk. A total of 358 unaffected control (CON) participants [159 South Africa (SA CON) and 199 Australia (AUS CON)] and 166 affected AT (TEN) participants (87 SA TEN and 79 AUS TEN) were genotyped for four variants [CASP8 (rs384129), CASP8 (rs1045485), NOS3 (rs1799983), and NOS2 (rs2779249)]. Logistic regression was used to derive risk models for AT. A receiver operator characteristic (ROC) curve was plotted to determine the effectiveness of a model to capture AT risk. This study indicates the independent association of CASP8_rs1045485 and CASP8_rs3834129 as well as their haplotype with AT risk and the identification of an optimal model which included genetic loci CASP8_rs384129 and CASP8_rs1045485 together with sex to capture AT risk in both SA and AUS. Collectively, these results further implicate the apoptosis signaling cascade as one of the biological pathways involved in the development of AT.

Aging contributes to inflammation in upper extremity tendons and declines in forelimb agility in a rat model of upper extremity overuse

We sought to determine if tendon inflammatory and histopathological responses increase in aged rats compared to young rats performing a voluntary upper extremity repetitive task, and if these changes are associated with motor declines. Ninety-six female Sprague-Dawley rats were used in the rat model of upper extremity overuse: 67 aged and 29 young adult rats. After a training period of 4 weeks, task rats performed a voluntary high repetition low force (HRLF) handle-pulling task for 2 hrs/day, 3 days/wk for up to 12 weeks. Upper extremity motor function was assessed, as were inflammatory and histomorphological changes in flexor digitorum and supraspinatus tendons. The percentage of successful reaches improved in young adult HRLF rats, but not in aged HRLF rats. Forelimb agility decreased transiently in young adult HRLF rats, but persistently in aged HRLF rats. HRLF task performance for 12 weeks lead to increased IL-1beta and IL-6 in flexor digitorum tendons of aged HRLF rats, compared to aged normal control (NC) as well as young adult HRLF rats. In contrast, TNF-alpha increased more in flexor digitorum tendons of young adult 12-week HRLF rats than in aged HRLF rats. Vascularity and collagen fibril organization were not affected by task performance in flexor digitorum tendons of either age group, although cellularity increased in both. By week 12 of HRLF task performance, vascularity and cellularity increased in the supraspinatus tendons of only aged rats. The increased cellularity was due to increased macrophages and connective tissue growth factor (CTGF)-immunoreactive fibroblasts in the peritendon. In conclusion, aged rat tendons were overall more affected by the HRLF task than young adult tendons, particularly supraspinatus tendons. Greater inflammatory changes in aged HRLF rat tendons were observed, increases associated temporally with decreased forelimb agility and lack of improvement in task success.

Tendinosis: pathophysiology and nonoperative treatment

Tendinosis is a troublesome clinical entity affecting many active people. Its treatment remains a challenge to sports medicine clinicians. The etiopathophysiology of tendinosis has not been well delineated. The known pathophysiology and the recent advances in the understanding of the etiologic process of tendinosis are discussed here, including new concepts in mechanotransduction and the biochemical alterations that occur during tendon overload. The optimal, nonoperative treatment of tendinosis is not clear. This article reviews recent evidence of the clinical efficacy of the following interventions: eccentric exercise, extracorporal shock wave treatment, corticosteroid and nonsteroidal anti-inflammatory medications, sclerosing injections, nitric oxide, platelet-rich plasma injections, and matrix metalloproteinase inhibitors. Eccentric exercise has strongest evidence of efficacy. Extracorporal shock wave treatment has mixed evidence and needs further study of energy and application protocols. Sclerosing agents show promising early results but require long-term studies. Corticosteroid and nonsteroidal anti-inflammatory medications have not been shown to be effective, and many basic science studies raise possible concerns with their use. Nitric oxide has been shown in several basic science studies to be promising, but clinical efficacy has not been well established. More clinical trials are needed to assess dosing, indications, and clinical efficacy of nitric oxide. Platelet-rich plasma injections have offered encouraging short-term results. Larger and longer-term clinical trials are needed to assess this promising modality. Matrix metalloproteinase inhibitors have had few clinical studies, and their role in the treatment of tendinosis is still in the early phase of investigation.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Short-term outcomes of extracorporeal shock wave therapy for the treatment of chronic non-calcific tendinopathy of the supraspinatus: a double-blind, randomized, placebo-controlled trial

Background

There is evidence supporting the use of extracorporeal shock wave therapy (ESWT) in calcific tendinopathy of the rotator cuff, but the best current evidence does not support its use in non-calcifying tendinopathy. We conducted a randomized placebo-controlled trial to investigate the efficacy and safety of low energy ESWT for non-calcifying tendinopathy of the rotator cuff.

Methods

20 patients with non-calcifying supraspinatus tendinopathy (NCST) were randomized to an active or a sham treatment group. Physical, blood, roentgenographic, and MRI examinations of the shoulder were conducted to verify that patients met the inclusion and exclusion criteria. These examinations were repeated six and twelve weeks after treatments. Effectiveness was determined by comparison of the mean improvement in the Constant and Murley score (CMS) between the treatment and the placebo groups at three months. Safety was assessed by analyzing the number and severity of adverse events.

Results

All the patients completed the investigation protocol. At the final follow-up, significant improvement in the total CMS score and most of the CMS subscales was observed in the ESWT group when compared to the baseline values. Significantly higher total CMS, and significantly higher scores for CMS pain and ROM were observed in the ESWT group when compared to the placebo. No serious adverse events were noted after ESWT.

Conclusions

Patients suffering from NCST may benefit from low energy ESWT, at least in short-term. The application protocol of ESWT is likely to play a key-role in a successful treatment. Future investigations should be undertaken on the long-term effects of this technique for the treatment of NCST.

Trial registration

Current Controlled Trials ISRCTN41236511

Lessons we can learn from gene expression patterns in rotator cuff tears and tendinopathies

Persistently high failure rates that are reported after rotator cuff repairs have encouraged greater understanding of the pathophysiology that underlies rotator cuff tears. Biologic changes that contribute to the pathogenesis of rotator cuff tears and tendinopathies, as well as adaptation after these changes, have been well described. A subset of patients with a genetic predisposition to early onset of rotator cuff tears and earlier symptom and disease progression have been identified. Many biologic changes occurring at the gene level have been identified. Pathways that are believed to contribute to rotator cuff tendinopathies include extracellular matrix remodeling, angiogenesis, changes in metabolism, apoptosis, and stress-related genes. Metaplasia of rotator cuff cells is contributed to by changes in gene expression. Modification of these gene changes may be possible through mechanical loading, drugs, or cellular manipulation. Gene changes may offer greater insight into why certain tears fail to heal and help to identify therapeutic targets.

Histopathology of rotator cuff tears

The pathogenesis of rotator cuff tears is multifactorial. Tendon abnormalities of the rotator cuff include alteration of collagen fiber structure, tenocytes, cellularity, and vascularity. Ruptured tendons show marked collagen degeneration and disordered arrangement of collagen fibers. Fibroblast population decreases as the size of the tear in the rotator cuff increases. The larger fibroblast population seen in the smaller tears is also actively proliferating and is part of an active reparative process. Inflammatory cell infiltrate correlates inversely to rotator cuff tear size in the torn supraspinatus tendon samples, with larger tears showing a marked reduction in all cell types. As tear size increase, there is also a progressive decrease in the number of blood vessels. Whether rotator cuff tear heals spontaneously is an important pathologic and clinical question. Histologic changes indicative of repair and inflammation lead to consider biological options in addition to biomechanical treatment of the rotator cuff tears.

Biological factors in the pathogenesis of rotator cuff tears

Rotator cuff tears are common, and lead to shoulder pain and functional impairment. Despite their frequency and related disability, etiology and pathogenesis are still debated. Multiple factors contribute to tears of the rotator cuff. Extrinsic factors are anatomic variables, such as acromial morphologic characteristics, os acromiale, and acromial spurs that compress the rotator cuff by bony impingement or direct pressure from the surrounding soft tissue. Intrinsic factors arise from the tendon itself, because of tensile overload, aging, microvascular supply, traumatisms, or degeneration. Little information is available from a cellular and molecular point of view. We reviewed the biological factors involved in the pathogenesis of rotator cuff tears. Understanding the mechanism of rotator cuff pathology would facilitate the rationale for therapeutic interventions, by guiding the design, selection, and implementation of treatment strategies such as biologic modulation and preventive measures.

Tendinosis-like histologic and molecular changes of the Achilles tendon to repetitive stress: a pilot study in rats

BACKGROUND

Tendinopathy (pain and tendon degeneration) is associated with repetitive use and mechanical overload. However, the etiology of tendinopathy remains unclear. Clarification of histologic and molecular changes of tendon to repetitive stress could provide better understanding of Achilles tendon disorders related to repetitive stress.

QUESTIONS/PURPOSES

We asked whether repetitive stress simulating overuse of the Achilles tendon induced (1) histologic changes in rats similar to tendinosis (increased cellularity of fibrocytes, increased disorganization of collagen fiber, and increased roundness of the nucleus of the fibrocyte), (2) increased collagen Type III occurrence, and (3) increased inducible nitric oxide synthase (iNOS) expression.

METHODS

We used an exercise protocol simulating repetitive, jerky, eccentric contraction of the triceps surae in 15 rats. We conducted the exercise for 2 hours per day, three times per week using the right rear legs only and the left legs as internal controls. We harvested Achilles tendons after either 2, 4, or 6 weeks of exercise, and evaluated changes in tendon thickness, fibrocyte count, collagen fiber arrangement, collagen fiber type, and occurrence of iNOS.

RESULTS

Exercised Achilles tendons showed increased cellularity of fibrocytes at 4 and 6 weeks of exercise, and disorganized collagen fiber arrangement at 6 weeks of exercise. There was a trend for Type III collagen occurrence being greater in experimental groups. Expression of iNOS increased after 2 and 4 weeks of exercise when compared with that of the controls, but decreased after 6 weeks.

CONCLUSIONS

These observations suggest repetitive, synchronized, passive, and jerky exercise induced by electrical stimulation can lead to the tendinosis-like changes in the Achilles tendons in rats with imbalance between synthesis and degeneration after 4 weeks of exercise.

CLINICAL RELEVANCE

This newly designed exercise protocol may be used to design an animal model of Achilles tendon overuse. With this model, therapeutic interventions of tendinopathy could be analyzed by investigation of tendon biology and response in terms of histologic and molecular changes.

What are the validated animal models for tendinopathy?

Chronic tendinopathy refers to a broad spectrum of pathological conditions in tendons and their insertion, with symptoms including activity-related chronic pain. To study the pathogenesis and management strategies of chronic tendinopathy, studies in animal models are essential. The different animal models in the literature present advantages and limitations, and there is no consensus regarding the criteria of a universal tendinopathy animal model. Based on the review of literature and the discussion in the International Symposium on Ligaments and Tendons-X, we concluded that established clinical, histopathological and functional characteristics of human tendinopathy were all important and relevant criteria to be met, if possible, by animal models. As tendinopathy is a progressive, multifactorial tendon disorder affecting different anatomical structures, it may not be realistic to expect a single animal model to study all aspects of tendinopathy. Staging of tendinopathy over time and clearer definition of tendinopathies in relation to severity and type would enable realistic targets with any animal model. The existing animal models can be used for answering specific questions (horses for courses) but should not be used to conclude the general aspects of tendinopathy neither in animals nor in human.

Fourier transform infrared spectroscopic analysis of normal and torn rotator-cuff tendons

We have used Fourier transform infrared spectroscopy (FTIR) to characterise the chemical and structural composition of the tendons of the rotator cuff and to identify structural differences among anatomically distinct tears. Such information may help to identify biomarkers of tears and to provide insight into the rates of healing of different sizes of tear. The infrared spectra of 81 partial, small, medium, large and massive tears were measured using FTIR and compared with 11 uninjured control tendons. All the spectra were classified using standard techniques of multivariate analysis.

FTIR readily differentiates between normal and torn tendons, and different sizes of tear. We identified the key discriminating molecules and spectra altered in torn tendons to be carbohydrates/phospholipids (1030 cm−1 to 1200 cm−1), collagen (1300 cm−1 to 1700 cm−1 and 3000 cm−1 to 3350 cm−1) and lipids (2800 cm−1 to 3000 cm−1).

Our study has shown that FTIR spectroscopy can identify tears of the rotator cuff of varying size based upon distinguishable chemical and structural features. The onset of a tear is mainly associated with altered structural arrangements of collagen, with changes in lipids and carbohydrates. The approach described is rapid and has the potential to be used peri-operatively to determine the quality of the tendon and the extent of the disease, thus guiding surgical repair.

Transient decreases in forelimb gait and ground reaction forces following rotator cuff injury and repair in a rat model

Due to inadequate healing, surgical repairs of torn rotator cuff tendons often fail, limiting the recovery of upper extremity function. The rat is frequently used to study rotator cuff healing; however, there are few systems capable of quantifying forelimb function necessary to interpret the clinical significance of tissue level healing. We constructed a device to capture images, ground reaction forces and torques, as animals ambulated in a confined walkway, and used it to evaluate forelimb function in uninjured control and surgically injured/repaired animals. Ambulatory data were recorded before (D-1), and 3, 7, 14, 28 and 56 days after surgery. Speed as well as step width and length were determined by analyzing ventral images, and ground reaction forces were normalized to body weight. Speed averaged 22+/-6 cm/s and was not affected by repair or time. Step width and length of uninjured animals compared well to values measured with our previous system. Forelimbs were used primarily for braking (-1.6+/-1.5% vs +2.5+/-0.6%), bore less weight than hind limbs (49+/-5% vs 58+/-4%), and showed no differences between sides (49+/-5% vs 46+/-5%) for uninjured control animals. Step length and ground reaction forces of the repaired animals were significantly less than control initially (days 3, 7 and 14 post-surgery), but not by day 28. Our new device provided uninjured ambulatory data consistent with our previous system and available literature, and measured reductions in forelimb function consistent with the deficit expected by our surgical model.

[Tenocytes and the extracellular matrix : a reciprocal relationship]

The characteristic cells in tendons and ligaments are called tenocytes, which are responsible for the formation and turnover of the extracellular matrix. They react to external stimuli and facilitate the functional adaptation of the proteoglycan and collagen network to mechanical requirements. Via numerous cellular processes they form a complex communicating network which demonstrates coordinated directional reactions. As is common to all tissues in the human body, tendons are subject to age changes which influence the tenocytes, but additionally the structural organization and hence the function of the extracellular matrix. The function and organization of tendons are also affected by mechanical forces, as well as by various cytokines produced in the tissue and by the application of anti-inflammatory medication.

Patellar tendinopathy caused by a para-articular/extraskeletal osteochondroma in the lateral infrapatellar region of the knee: a case report

Patellar tendinopathy is characterized by activity-related anterior knee pain. It is most commonly related to sports activity, but has also been reported in the non-athletic population. Most injuries are caused by microtrauma, resulting in tendinitis or tendinosis. Extraskeletal paraarticular osteochondromas, which occur in the soft tissues near the joint, are rare. The infrapatellar fat pad and joint capsule are the most common sites of these tumors. Here, a case of patellar tendinitis caused by an extraskeletal paraarticular osteochondroma is reported. The symptoms included intensifying pain upon flexion and a palpable click that was located at the medial side of the mass. The patient was pain-free within 3 weeks after excision of the tumor and the clicking disappeared. To our best knowledge, no other case of patellar tendinitis caused by an extraskeletal paraarticular osteochondroma has been reported in the English literature.

Is apoptosis the cause of noninsertional achilles tendinopathy?

BACKGROUND

The pathogenesis of chronic tendinopathy is unclear but it does not appear to be an inflammatory process. Apoptosis may lead to degenerate tissue through a nitric oxide-mediated pathway. Increased levels of nitric oxide have been demonstrated in Achilles tendinopathy.

HYPOTHESIS

Nitric oxide-mediated apoptosis is an important mechanism in the development of Achilles tendinopathy.

STUDY DESIGN

Controlled laboratory study.

METHODS

Samples were obtained from the Achilles tendons of 14 patients with noninsertional Achilles tendinopathy. Control samples were taken from macroscopically normal tendon correlating with areas of normal tissue on magnetic resonance imaging. Immunohistochemical techniques identified the expression of inducible and endothelial nitric oxide synthase as markers of nitric oxide production. Apoptotic cells were identified using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and the demonstration of caspase-3 activation.

RESULTS

Significant differences were found between the diseased tendon and the controls for all parameters. The mean caspase-3 cell count for diseased tendon was 51.9 versus 28.3 for the controls (P < .001). The mean TUNEL cell count for diseased tendon was 24.1 compared with 14.8 (P < .001). Inducible nitric oxide synthase (iNOS) densitometry revealed a mean of 26.1 for the diseased tissue versus 15.0 for the controls (P < .001) and the values for endothelial nitric oxide synthase (eNOS) were 48.3 and 23.7, respectively (P = .015).

CONCLUSION

Apoptosis may play a role in the development of noninsertional Achilles tendinopathy and appears to be related to the presence of raised eNOS and iNOS levels.

CLINICAL RELEVANCE

A clearer understanding of the tendinopathic process may lead to new treatment strategies aimed at modulating apoptosis.

Tendon degeneration is not mediated by regulation of Toll-like receptors 2 and 4 in human tenocytes

We hypothesized that expression of Toll-like receptors (TLRs) 2 and 4 by tenocytes is involved in the catabolic processes of tendon degeneration. We investigated TLR2 and TLR4 expression by tenocytes in healthy and tendinotic Achilles tendons. We also investigated whether TLR2 and TLR4 could be upregulated in tendon explants using proinflammatory cytokines interleukin (IL)-1beta and tumor necrosis factor alphpa (TNFalpha). Peroperatively harvested healthy (n = 5) and tendinotic (n = 13) Achilles tendon samples were examined by real-time RT-PCR and immunohistochemical staining for TLR2 and TLR4. In addition, the catabolic process in tendinopathy was analyzed by real-time RT-PCR for matrix metalloproteinases MMP1, MMP3, MMP9, and MMP13. Furthermore, healthy tendon explants were cultured in the presence of 20 ng/ml IL-1beta (n = 10) or 10 ng/mL TNFalpha (n = 8) for 4, 24, 48, and 72 h before analysis of TLR and MMP expression levels. Although mRNA levels for both TLR2 and TLR4 were detected in healthy and tendinotic Achilles tendons, we could not confirm expression of these receptors by immunohistochemical staining in either healthy or tendinotic tendon samples. Both receptors did not show significant transcriptional regulation in tendinopathy, although MMP3 was downregulated and MMP9 was upregulated in tendinopathy. In tendon explant cultures TLR2 mRNA was upregulated by TNFalpha (p < 0.05) and IL-1beta (not significant). TLR4 gene expression was not altered by addition of IL-1beta or TNFalpha. Tendon tissue can be stimulated to increase TLR2 gene expression by addition of catabolic factors TNFalpha or IL-1beta. However, the catabolic processes in Achilles tendinopathy cannot be attributed to regulation of TLR2 and TLR4 by tenocytes.

Animal models of tendinopathy

PURPOSE

The term tendinopathy describes non-ruptured tendon injuries. While several important studies have evaluated the aetiology, pathogenesis, and treatment of this common condition, further study is needed. Several animal models, which allow for full tissue evaluation on different organizational levels and stages of disease, have been used to investigate tendinopathy.

METHOD

A literature review was conducted to identify and evaluate animal models that have been developed and used to study the aetiology and pathology of tendinopathy.

RESULTS

Animal models of tendinopathy fit into two general categories based on the mode of injury application: (i) models that induce tendinopathy through a change in the mechanical environment, and (ii) models that induce tendinopathy through a chemical agent. The cost, difficulty, invasiveness, reproducibility and time required to induce injury in these models varies. Mechanically-induced models are beneficial since they induce injury through repetitive mechanical loading, similar to how tendinopathy is believed to develop in the human condition. Chemically-induced models are beneficial by allowing for the study of the interplay among inflammatory cells, mechanical loading and tissue healing.

CONCLUSION

Further work is needed to fully characterize and understand tendinopathy. Appropriate animal models provide a greater understanding of human tendinopathy, leading to better prevention and treatment.

Neuropeptides in tendinopathy

Overuse tendinopathy remains a major clinical burden for sports medicine and general practitioners. Recent studies have highlighted the role of sensory and autonomic nerves in generating or perpetuating the symptoms and tissue abnormalities associated with tendinopathy. We outline the neuroanatomy and potential roles of nerves and associated neuropeptides in tendinopathy. In addition, intriguing new data is reviewed which suggests that there may be a substantial intrinsic source of neuropeptides within tendons - namely, the tenocytes themselves. The potential roles of Substance P and mast cells are highlighted in particular. We discuss the implications for conservative management including sclerosing injections and exercise training.

Treatment of tendinopathy: what works, what does not, and what is on the horizon

Tendinopathy is a broad term encompassing painful conditions occurring in and around tendons in response to overuse. Recent basic science research suggests little or no inflammation is present in these conditions. Thus, traditional treatment modalities aimed at controlling inflammation such as corticosteroid injections and nonsteroidal antiinflammatory medications (NSAIDS) may not be the most effective options. We performed a systematic review of the literature to determine the best treatment options for tendinopathy. We evaluated the effectiveness of NSAIDS, corticosteroid injections, exercise-based physical therapy, physical therapy modalities, shock wave therapy, sclerotherapy, nitric oxide patches, surgery, growth factors, and stem cell treatment. NSAIDS and corticosteroids appear to provide pain relief in the short term, but their effectiveness in the long term has not been demonstrated. We identified inconsistent results with shock wave therapy and physical therapy modalities such as ultrasound, iontophoresis and low-level laser therapy. Current data support the use of eccentric strengthening protocols, sclerotherapy, and nitric oxide patches, but larger, multicenter trials are needed to confirm the early results with these treatments. Preliminary work with growth factors and stem cells is promising, but further study is required in these fields. Surgery remains the last option due to the morbidity and inconsistent outcomes. The ideal treatment for tendinopathy remains unclear.

LEVEL OF EVIDENCE

Level II, systematic review.