Matrix metallopeptidase 2 activity in tendon regions: effects of mechanical loading exercise associated to anabolic-androgenic steroids

Initiating Testosterone Therapy Without Indication for Treatment of Low Testosterone Is Associated With Higher Risk of Tendon Tear

BACKGROUND

Studies have demonstrated an increasing rate of testosterone supplementation in patients who do not meet criteria for testosterone deficiency, but the risks associated with testosterone supplementation are unclear.

HYPOTHESIS

Patients initiating testosterone therapy would be diagnosed with significantly more tendon tears and undergo significantly more tendon repairs than matched controls never on testosterone therapy.

STUDY DESIGN

Cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Male patients who initiated testosterone therapy within 30 days of a primary care visit and who did not meet criteria for treatment of low testosterone were identified (n = 112,242). Propensity score matching generated a control cohort (n = 448,968) with no history of testosterone therapy and based on several comorbidities at the time of said age-matched primary care visit. Rates of tendon tears and tendon repairs within 1 and 2 years after primary care visit were compared using multivariable logistic regression.

RESULTS

Within 1 and 2 years, compared with controls, the testosterone supplementation cohort demonstrated significantly higher rates of rotator cuff tear (odds ratio [OR], 1.35; OR, 1.31), patellar tendon tear (OR, 2.06; OR, 2.14), and any tendon tear (OR, 1.33; OR, 1.31). The testosterone supplementation cohort demonstrated significantly higher rates of quadriceps tendon tears within 1 year (OR, 1.59). Within 1 and 2 years, compared with controls, the testosterone supplementation cohort demonstrated significantly higher rates of rotator cuff repair (OR, 1.28; OR, 1.23), distal biceps tendon repair (OR, 1.65; OR, 1.54), patellar tendon repair (OR, 2.28; OR, 2.18), and any tendon repair (OR, 1.27; OR, 1.23).

CONCLUSION

Testosterone supplementation is associated with an increased risk of tendon tears and repairs for at least the first and second year after initiating therapy in patients with no documented laboratory testing. Patients considering testosterone therapy should be counseled on this increased risk of tendon injury.

Functional changes to Achilles tendon and enthesis in an adolescent mouse model of testosterone hormone therapy

PURPOSE/AIM

Some youth seek puberty suppression to prolong decision-making prior to starting hormone therapy to help align their physical sex characteristics with their gender identity. During peripubertal growth, connective tissues such as tendon rapidly adapt to applied mechanical loads (e.g. exercise) yet if and how tendon adaptation is influenced by sex and gender-affirming hormone therapy during growth remains unknown. The goal of this study was to understand how pubertal suppression followed by testosterone influences the structural and functional properties of the Achilles tendon using an established adolescent mouse model of testosterone hormone therapy.

MATERIALS AND METHODS

C57BL/6N female mice were assigned at postnatal day 26 to the following experimental groups: control (vehicle treated), gonadotropin release hormone analogue (GnRHa) treatment alone to delay puberty, testosterone (T) alone after puberty, or delayed puberty with T treatment (i.e. GnRHa followed by T).

RESULTS

We found that pubertal suppression using GnRHa with and without T, as well as treatment with T alone post-puberty, increased the ultimate load of tendon in female mice. Additionally, we found that GnRHa, but not T treatment resulted in a significant increase in cell density at the Achilles enthesis.

CONCLUSIONS

These findings demonstrate that delayed puberty and T have no negative influence on structural or functional properties of mouse tendon.

Functional Changes to Achilles Tendon and Enthesis in a Mouse Model of an Adolescent Masculine Gender-Affirming Hormone Treatment

Many transgender youth seek gender affirming care, such as puberty suppression, to prolong decision-making and to align their physical sex characteristics with their gender identity. During peripubertal growth, connective tissues such as tendon rapidly adapt to applied mechanical loads (e.g., exercise) yet if and how tendon adaptation is influenced by sex and gender affirming hormone therapy during growth remains unknown. The goal of this study was to understand the how pubertal suppression influences the structural and functional properties of the Achilles tendon using an established mouse model of transmasculine gender affirming hormone therapy. C57BL/6N female-born mice were assigned to experimental groups to mimic gender-affirming hormone therapy in human adolescents, and treatment was initiated prior to the onset of puberty (at postnatal day 26, P26). Experimental groups included controls and mice serially treated with gonadotropin release hormone analogue (GnRHa), delayed Testosterone (T), or GnRHa followed by T. We found that puberty suppression using GnRHa, with and without T, improved the overall tendon load capacity in female-born mice. Treatment with T resulted in an increase in the maximum load that tendon can withstand before failure. Additionally, we found that GnRHa, but not T, treatment resulted in a significant increase in cell density at the Achilles enthesis.

Innovative Reports on the Effects of Anabolic Androgenic Steroid Abuse-How to Lose Your Mind for the Love of Sport

Anabolic-androgenic steroids (anabolic-androgenic steroids, AAS) are testosterone-derived compounds whose popularity and use are constantly growing. Chronic use of AAS leads to many hormonal and metabolic disorders in the human body, which often lead to permanent health damage. Changes affect the following systems: cardiovascular, musculoskeletal, reproductive, digestive, and nervous. We decided to collect the existing knowledge in the literature and enrich it with the latest research reports in the field of degenerative effects of AAS on the nervous system. The work aimed to increase public awareness of the dangers and consequences of AAS use and improve it with the latest research on the neurodegenerative effects of AAS. We hope that our work will contribute to raising public awareness and reducing the use of AAS.

Early Neuromuscular Electrical Stimulation Preserves Muscle Size and Quality and Maintains Systemic Levels of Signaling Mediators of Muscle Growth and Inflammation in Patients with Traumatic Brain Injury: A Randomized Clinical Trial

Objective

To investigate the effects of an early neuromuscular electrical stimulation (NMES) protocol on muscle quality and size as well as signaling mediators of muscle growth and systemic inflammation in patients with traumatic brain injury (TBI).

Design

Two-arm, single-blinded, parallel-group, randomized, controlled trial with a blinded assessment. Setting. Trauma intensive care unit at a university hospital. Participants. Forty consecutive patients on mechanical ventilation (MV) secondary to TBI were prospectively recruited within the first 24 hours following admission. Interventions. The intervention group (NMES; n = 20) received a daily session of NMES on the rectus femoris muscle for five consecutive days (55 min/each session). The control group (n = 20) received usual care. Main Outcome Measures. Muscle echogenicity and thickness were evaluated by ultrasonography. A daily blood sample was collected to assess circulating levels of insulin-like growth factor I (IGF-I), inflammatory cytokines, and matrix metalloproteinases (MMP).

Results

Both groups were similar at baseline. A smaller change in muscle echogenicity and thickness (difference between Day 1 and Day 7) was found in the control group compared to the NMES group (29.9 ± 2.1 vs. 3.0 ± 1.2, p < 0.001; -0.79 ± 0.12 vs. -0.01 ± 0.06, p < 0.001, respectively). Circulating levels of IGF-I, pro-inflammatory cytokines (IFN-y), and MMP were similar between groups.

Conclusion

An early NMES protocol can preserve muscle size and quality and maintain systemic levels of signaling mediators of muscle growth and inflammation in patients with TBI. This trial is registered with https://www.ensaiosclinicos.gov.br under number RBR-2db.

The use of prescription testosterone is associated with an increased likelihood of experiencing a distal biceps tendon injury and subsequently requiring surgical repair

BACKGROUND

In the United States, the use of testosterone therapy has increased over recent years. Anabolic steroid use has been associated with tendon rupture, although there is a paucity of evidence evaluating the risk of biceps tendon injury (BTI) with testosterone therapy. The aim of this study was to quantify the risk of BTI after the initiation of testosterone therapy.

METHODS

This was a retrospective cohort study using the PearlDiver database. Records between 2011 and 2018 were queried to identify patients aged 35-75 years who filled a testosterone prescription for a minimum of 3 months. A control group was created, comprising patients aged 35-75 years who had never filled a prescription for exogenous testosterone. International Classification of Diseases, Ninth Revision, International Classification of Diseases, Tenth Revision, and Current Procedural Terminology codes were used to identify patients with distal biceps injuries and those undergoing surgical repair. Three matching processes were completed: one for the overall cohort, one for the cohort comprising only male patients, and one for the cohort comprising only female patients. Each cohort was matched to its control on age, sex, Charlson Comorbidity Index, diabetes, tobacco use, and osteoporosis. Multivariate logistic regression was used to compare rates of distal BTI and subsequent surgical repair in the testosterone groups with their control groups.

RESULTS

A total of 776,974 patients had filled a prescription for testosterone for a minimum of 3 consecutive months. In the overall matched analysis between the testosterone and control groups (n = 291,610 in both), the mean age of the patients was 53.9 years and 23.1% were women. Within 1 year of filling exogenous testosterone prescriptions for a minimum of 3 consecutive months, 650 patients experienced a distal BTI compared with 159 patients in the control group (odds ratio [OR], 4.10; 95% confidence interval [CI], 3.45-4.89; P < .001). At any time after testosterone therapy, patients with testosterone use were more than twice as likely to experience a distal BTI as their matched controls (OR, 2.07; 95% CI, 1.94-2.38). Patients who filled prescriptions for testosterone were more likely to undergo surgical repair within a year of the injury compared with the control group. A similar trend was seen in the cohort comprising male patients (OR, 1.63; 95% CI, 1.29-2.07).

CONCLUSION

Patients with prior prescription testosterone exposure have an increased rate of BTI and biceps tendon repair compared with patients without such exposure. This finding provides insight into the risk profile of testosterone therapy, and doctors should consider counseling patients about this risk, particularly male patients.

Role of resistance training in bone macro and micro damages in an estrogen absence animal model

AIMS

We evaluated the effects of resistance training (RT) on bone properties, morphology, and bone extracellular matrix (ECM) remodeling markers in an ovariectomy (OVX) rat model.

MAIN METHODS

Thirty-six female rats were divided into four groups: sham sedentary, OVX sedentary, sham RT, and OVX RT. Rats performed RT for ten weeks, during which they climbed a ladder with progressive loads attached to the tail. Tibias were stored for dual-energy X-ray densitometry (DXA), micro-computed tomography (micro-CT), and biomechanical, biophysical, and biochemical analysis. Femurs were stored for morphological, gene expression, and gelatin zymography analysis.

KEY FINDINGS

OVX decreased bone mineral density, stiffness, maximal load, and calcium content, which was reversed by RT. The trabecular number, connectivity, and MMP-13 gene expression decreased in OVX groups. Furthermore, OVX increased run-related transcription factor-2 (RUNX-2) and osteoprotegerin (OPG) gene expression, and increased the number of adipocytes in bone marrow and MMP-2 activity.

SIGNIFICANCE

RT was efficient in preventing or reversing changes in bone biomechanical properties in OVX groups, improving fracture load and resilience, which is relevant to prevent fractures. On the other hand, RT did not decrease the number of bone adipocytes in the OVX-RT group. However, RT was efficient for increasing trabecular thickness and cortical bone volume, which improved bone resistance. Our findings provide further insights into the mechanisms involved in the role of RT in OVX damage protection.

Anabolic Androgenic Steroids in Orthopaedic Surgery: Current Concepts and Clinical Applications

Despite the well-documented effects of testosterone and its synthetic derivatives—collectively termed anabolic androgenic steroids (AASs)—on the musculoskeletal system, the therapeutic use of these agents has received limited investigation within the field of orthopaedic surgery. In the last 2 decades, preclinical and clinical research has started to identify promising applications of the short-term use of AASs in the perioperative period. There is evidence to suggest that AASs may improve postoperative recovery after anterior cruciate ligament reconstruction and total joint arthroplasty. In addition, AASs may augment the biological healing environment in specific clinical scenarios including muscle injury, fracture repair, and rotator cuff repair. Current literature fails to present strong evidence for or against the use of AASs in orthopaedics, but there is continuous research on this topic. The purpose of this study was to provide a comprehensive overview of the current status of AAS applications in orthopaedic surgery, with an emphasis on preclinical data, clinical studies, and future directions.

Asynchronous Bilateral Achilles Tendon Rupture with Selective Androgen Receptor Modulators: A Case Report

CASE

A 36-year-old male competitive powerlifter sustained asynchronous bilateral Achilles tendon ruptures after using 2 types of selective androgen receptor modulators (SARMs). Both tendon ruptures occurred near the myotendinous junction and were treated with open surgical repair and an initial period of immobilization followed by progressive weightbearing and rehabilitation; no postoperative complications were observed.

CONCLUSION

Previous studies have reported that anabolic androgenic steroids have a deleterious impact on tendon structure and function. This case suggests that SARM compounds may also predispose users to Achilles tendon rupture.

Adverse Effects of Anabolic-Androgenic Steroids: A Literature Review

Anabolic-androgenic steroids (AASs) are a large group of molecules including endogenously produced androgens, such as testosterone, as well as synthetically manufactured derivatives. AAS use is widespread due to their ability to improve muscle growth for aesthetic purposes and athletes’ performance, minimizing androgenic effects. AAS use is very popular and 1–3% of US inhabitants have been estimated to be AAS users. However, AASs have side effects, involving all organs, tissues and body functions, especially long-term toxicity involving the cardiovascular system and the reproductive system, thereby, their abuse is considered a public health issue. The aim of the proposed review is to highlight the most recent evidence regarding the mechanisms of action of AASs and their unwanted effects on organs and lifestyle, as well as suggesting that AAS misuse and abuse lead to adverse effects in all body tissues and organs. Oxidative stress, apoptosis, and protein synthesis alteration are common mechanisms involved in AAS-related damage in the whole body. The cardiovascular system and the reproductive system are the most frequently involved apparatuses. Epidemiology as well as the molecular and pathological mechanisms involved in the neuropsychiatric side-effects of AAS abuse are still unclear, further research is needed in this field. In addition, diagnostically reliable tests for AAS abuse should be standardized. In this regard, to prevent the use of AASs, public health measures in all settings are crucial. These measures consist of improved knowledge among healthcare workers, proper doping screening tests, educational interventions, and updated legislation.

Resistance training decreases matrix metalloproteinase-2 activity in quadriceps tendon in a rat model of osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a degenerative disease that induces peri-articular tissue degradation. OA induces an imbalance between synthesis and degradation of the extracellular matrix components in favor of catabolic events, promoting pathological remodeling and involving degradative enzymes, such as matrix metalloproteinases (MMPs).

OBJECTIVE

This study aimed to investigate the effects of 8-weeks resistance training (RT) on MMP-2 activity in the quadriceps tendon and patellar tendon in an OA model.

METHODS

Twenty-four Wistar rats were randomly divided into six groups: Control, Exercise, Sham, Sham with Exercise, OA, and OA with Exercise (OAE). The OA model was performed by anterior cruciate ligament transection surgery on the left knee. The 8-week RT consisted of climbing a 1.1-m vertical ladder three times per week with progressive weights secured to the animals' tails. MMP-2 activity was analyzed by zymography.

RESULTS

The OAE group displayed lower pro, intermediate, and active MMP-2 activity in the quadriceps tendon compared with the OA group (p<0.05). For the patellar tendon, there was no significant difference between the OAE group compared with the other groups (p>0.05) for pro, intermediate, and active MMP-2 activity. Moreover, MMP-2 activity differed between tissues, the OA and OAE groups presented lower pro, intermediate, and active MMP-2 activity in the quadriceps tendon compared to the patellar tendon.

CONCLUSION

RT induced down-regulated MMP-2 activity in the quadriceps tendon. RT is a potential therapeutic approach to minimize the deleterious effects of extracellular matrix degeneration.

Achilles Tendon Repair by Decellularized and Engineered Xenografts in a Rabbit Model

Tendon tissue ruptures often require the replacement of damaged tissues. The use of auto- or allografts is notoriously limited due to the scarce supply and the high risks of immune adverse reactions. To overcome these limitations, tissue engineering (TE) has been considered a promising approach. Among several biomaterials, decellularized xenografts are available in large quantity and could represent a possible solution for tendon reconstruction. The present study is aimed at evaluating TE xenografts in Achilles tendon defects. Specifically, the ability to enhance the biomechanical functionality, while improving the graft interaction with the host, was tested. The combination of decellularized equine-derived tendon xenografts with or without the matrix repopulation with autologous bone marrow mesenchymal stem cells (BMSCs) under stretch-perfusion dynamic conditions might improve the side-to-side tendon reconstruction. Thirty-six New Zealand rabbits were used to create 2 cm long segmental defects of the Achilles tendon. Then, animals were implanted with autograft (AG) as the gold standard control, decellularized graft (DG), or in vitro tissue-engineered graft (TEG) and evaluated postoperatively at 12 weeks. After sacrifice, histological, immunohistochemical, biochemical, and biomechanical analyses were performed along with the matrix metalloproteinases. The results demonstrated the beneficial role of undifferentiated BMSCs loaded within decellularized xenografts undergoing a stretch-perfusion culture as an immunomodulatory weapon reducing the inflammatory process. Interestingly, AG and TEG groups exhibited similar results, behaved similarly, and showed a significant superior tissue healing compared to DG in terms of newly formed collagen fibres and biomechanical parameters. Whereas, DG demonstrated a massive inflammatory and giant cell response associated with graft destruction and necrosis, absence of type I and III collagen, and a higher amount of proteoglycans and MMP-2, thus unfavourably affecting the biomechanical response. In conclusion, this in vivo study suggests a potential use of the proposed tissue-engineered constructs for tendon reconstruction.

Androgen deprivation therapy and the risk of tenosynovitis in prostate cancer patients

OBJECTIVES

Androgen deprivation therapy (ADT) use in prostate cancer (PCa) patients has been reported to have an association with rheumatoid arthritis. We aimed to assess the impact of ADT on the subsequent risk of tenosynovitis.

METHODS

Using data from the National Health Insurance Research Database of Taiwan between 2001 and 2013, 3309 patients with PCa were identified. Among them, 729 ADT patients comprised the study group with 729 matched non-ADT controls. We used a 1:1 propensity score matched analysis. The demographic characteristics and comorbidities of the patients were analyzed; Cox proportional hazards regression was used to calculate the hazard ratios (HR) for the risk of tenosynovitis.

RESULTS

There were 224 (15.3%) patients with newly diagnosed tenosynovitis. Compared with non-ADT patients, ADT patients had a lower risk of subsequent tenosynovitis with an adjusted HR of 0.38 [95% confidence interval (CI) 0.28-0.51; P < 0.001].

CONCLUSIONS

ADT use apparently did not increase the risk of tenosynovitis in patients with PCa. Further studies are warranted to assess the clinical significance.

Detraining and Anabolic-Androgenic Steroid Discontinuation Change Calcaneal Tendon Morphology

Several side effects of anabolic-androgenic steroid (AAS) administration associated with training are reported in the biomechanical properties of the calcaneal tendon (CT) of rats. Thus, the aim of the present study is to evaluate the effects of the detraining and discontinuation of AAS administration on the CT morphology of rats submitted to exercise in water. Animals were divided into two groups (20/group): (1) Immediately after training (IA), and (2) Six weeks of detraining and AAS discontinuation (6W). The IA group included four subgroups: Sedentary (S), Trained (T), Sedentary with AAS administration (SAAS), and trained with AAS administration (TAAS). The 6W group included four subgroups: Sedentary (6W-S), six weeks of detrained (6W-T), six weeks of sedentary with AAS discontinuation (6W-SAAS), and six weeks of detrained with AAS discontinuation (6W-TAAS). Data show significant reduction in adipose cells volume density (Vv%) in the distal CT in 6W-TAAS group, indicating that training can exert a positive effect on the tendon. The 6W-SAAS group exhibited increased adipose cells Vv% in the distal region, compared with the W6-S and W6-T groups. A decrease in tendon proper cells Vv% and in peritendinous sheath cells Vv% of proximal and distal regions was also observed. In 6W-TAAS group showed increase in adipose cells, blood vessels, peritendinous sheath cells, and tendon proper cells Vv% in the distal region of the CT. The vertical jumps in water were not able to protect CT regions from the negative effects of AAS discontinuation for six weeks. However, after detraining and AAS discontinuation, many protective factors of the mechanical load in the long-term could be observed.

Tendon Remodeling in Response to Resistance Training, Anabolic Androgenic Steroids and Aging

Exercise training (ET), anabolic androgenic steroids (AAS), and aging are potential factors that affect tendon homeostasis, particularly extracellular matrix (ECM) remodeling. The goal of this review is to aggregate findings regarding the effects of resistance training (RT), AAS, and aging on tendon homeostasis. Data were gathered from our studies regarding the impact of RT, AAS, and aging on the calcaneal tendon (CT) of rats. We demonstrated a series of detrimental effects of AAS and aging on functional and biomechanical parameters, including the volume density of blood vessel cells, adipose tissue cells, tendon calcification, collagen content, the regulation of the major proteins related to the metabolic/development processes of tendons, and ECM remodeling. Conversely, RT seems to mitigate age-related tendon dysfunction. Our results suggest that AAS combined with high-intensity RT exert harmful effects on ECM remodeling, and also instigate molecular and biomechanical adaptations in the CT. Moreover, we provide further information regarding the harmful effects of AAS on tendons at a transcriptional level, and demonstrate the beneficial effects of RT against the age-induced tendon adaptations of rats. Our studies might contribute in terms of clinical approaches in favor of the benefits of ET against tendinopathy conditions, and provide a warning on the harmful effects of the misuse of AAS on tendon development.

Anabolic steroids and tendons: A review of their mechanical, structural, and biologic effects

One of the suspected deleterious effects of androgenic-anabolic steroids (AAS) is the increased risk for tendon rupture. However, investigations to date have produced inconsistent results and it is still unclear how AAS influence tendons. A systematic review of the literature was conducted to identify studies that have investigated the mechanical, structural, or biologic effects that AAS have on tendons. In total, 18 highly heterogeneous studies were identified. Small animal studies made up the vast majority of published research, and contradictory results were reported frequently. All of the included studies focused on the potential deleterious effects that AAS have on tendon, which is striking given the recent use of AAS in patients following tendon injury. Rather than providing strong evidence for or against the use of AAS, this review highlights the need for additional research. Future studies investigating the use of AAS as a possible treatment for tendon injury/pathology are supported by reports suggesting that AAS may counteract the irreparable structural/functional changes that occur in the musculotendinous unit following rotator cuff tears, as well as studies suggesting that the purported deleterious effects on tendon may be transient. Other possible areas for future research are discussed in the context of key findings that may have implications for the therapeutic application of AAS. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2830-2841, 2018.

Exercise Prevents Diaphragm Wasting Induced by Cigarette Smoke through Modulation of Antioxidant Genes and Metalloproteinases

BACKGROUND

The present study aimed to analyze the effects of physical training on an antioxidant canonical pathway and metalloproteinases activity in diaphragm muscle in a model of cigarette smoke-induced chronic obstructive pulmonary disease (COPD).

METHODS

Male mice were randomized into control, smoke, exercise, and exercise + smoke groups, which were maintained in trial period of 24 weeks. Gene expression of kelch-like ECH-associated protein 1; nuclear factor erythroid-2 like 2; and heme-oxygenase1 by polymerase chain reaction was performed. Metalloproteinases 2 and 9 activities were analyzed by zymography. Exercise capacity was evaluated by treadmill exercise test before and after the protocol.

RESULTS

Aerobic training inhibited diaphragm muscle wasting induced by cigarette smoke exposure. This inhibition was associated with improved aerobic capacity in those animals that were submitted to 24 weeks of aerobic training, when compared to the control and smoke groups, which were not submitted to training. The aerobic training also downregulated the increase of matrix metalloproteinases (MMP-2 and MMP-9) and upregulated antioxidant genes, such as nuclear factor erythroid-2 like 2 (NRF2) and heme-oxygenase1 (HMOX1), in exercise + smoke group compared to smoke group.

CONCLUSIONS

Treadmill aerobic training protects diaphragm muscle wasting induced by cigarette smoke exposure involving upregulation of antioxidant genes and downregulation of matrix metalloproteinases.

Effect of different resistance-training protocols on the extracellular matrix of the calcaneal tendon of rats

The calcaneal tendon extracellular matrix (ECM) is composed of collagen, non-collagenous glycoproteins and proteoglycans, and able to adapt to various biomechanical stimuli. The objective of this study was to analyze the response of different resistance-training protocols, such as hypertrophy, strength and resistance, on the organization of the calcaneal tendon after training. Wistar rats were divided into four groups: untrained (UT), resistance training (RT), hypertrophy training (HT), and strength training (ST). The protocol in a vertical climbing platform was performed thrice per week over twelve weeks. For biochemical study, the tendons of each group were minced and analyzed for gelatinases, quantification of non-collagenous proteins, sulfated glycosaminoglycans, and hydroxyproline. For morphological analysis, sections were stained with HE and toluidine blue. Non-stained sections were used for birefringence analysis under polarization microscopy. The highest hydroxyproline concentrations were found in HT (154.8±14.2) and RT (173.6±25.2) compared with UT (122.4±27.0). A higher concentration of non-collagenous proteins was detected in the RT group (14.98mg/g) compared with the other groups. In polarization microscopy, major birefringence was observed in HT and the lowest in ST compared with UT, indicating higher organization of collagen bundles in HT. In analysis for zymography, the presence of latent MMP-9 was more prominent in the ST group and the active MMP-9 more prominent in the HT group. For MMP-2, significant differences in the latent isoform between the HT (184,867±6765) and UT (173,018±9696) groups were found. In sections stained with toluidine blue (TB), higher metachromasia was observed in the tendon's distal region in HT and RT groups, indicating a greater amount of proteoglycans. We conclude that the different training protocols produced different responses in the ECM. The remarkable presence of MMP-2 and -9 in the hypertrophy training group may be related to the highest organization of collagen bundles and possibly a more efficient remodeling process, observed in that group, as demonstrated by images and measurements of birefringence.

Effects of aging and resistance training in rat tendon remodeling

In elderly persons, weak tendons contribute to functional limitations, injuries, and disability, but resistance training can attenuate this age-related decline. We evaluated the effects of resistance training on the extracellular matrix (ECM) of the calcaneal tendon (CT) in young and old rats and its effect on tendon remodeling. Wistar rats aged 3 mo (young, n = 30) and 20 mo (old, n = 30) were divided into 4 groups: young sedentary, young trained, old sedentary (OS), and old trained (OT). The training sessions were conducted over a 12-wk period. Aging in sedentary rats showed down-regulation in key genes that regulated ECM remodeling. Moreover, the OS group showed a calcification focus in the distal region of the CT, with reduced blood vessel volume density. In contrast, resistance training was effective in up-regulating connective tissue growth factor, VEGF, and decorin gene expression in old rats. Resistance training also increased proteoglycan content in young and old rats in special small leucine-rich proteoglycans and blood vessels and prevented calcification in OT rats. These findings confirm that resistance training is a potential mechanism in the prevention of aging-related loss in ECM and that it attenuates the detrimental effects of aging in tendons, such as ruptures and tendinopathies.-Marqueti, R. C., Durigan, J. L. Q., Oliveira, A. J. S., Mekaro, M. S., Guzzoni, V., Aro, A. A., Pimentel, E. R., Selistre-de-Araujo, H. S. Effects of aging and resistance training in rat tendon remodeling.

Hormones and tendinopathies: the current evidence

BACKGROUND

Tendinopathies negatively affect the quality of life of millions of people, but we still do not know the factors involved in the development of tendon conditions.

SOURCES OF DATA

Published articles in English in PubMed and Google Scholar up to June 2015 about hormonal influence on tendinopathies onset. One hundred and two papers were included following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

AREAS OF AGREEMENT

In vitro and in vivo, tenocytes showed changes in their morphology and in their functional properties according to hormonal imbalances.

AREAS OF CONTROVERSY

Genetic pattern, sex, age and comorbidities can influence the hormonal effect on tendons.

GROWING POINTS

The increasing prevalence of metabolic disorders prompts to investigate the possible connection between metabolic problems and musculoskeletal diseases.

AREAS TIMELY FOR DEVELOPING RESEARCH

The influence of hormones on tendon structure and metabolism needs to be further investigated. If found to be significant, multidisciplinary preventive and therapeutic strategies should then be developed.

Nandrolone increases angiotensin-I converting enzyme activity in rats tendons

INTRODUCTION: The renin-angiotensin system (RAS) has been associated with several biological processes of the human body, regulating, among others blood pressure and water and electrolytes balance. Moreover, RAS also regulates connective tissue growth. Recently, studies have shown that the use of nandrolone modifies the angiotensin-I converting enzyme (ACE) activity and increases collagen deposition in the heart. OBJECTIVE: The aim of study was to evaluate the Angiotensin-I converting enzyme (ACE) activity in the superficial flexor tendon (SFT) and in serum after load exercise in combination with anabolic androgenic steroid (AAS) administration after training session and six weeks of detraining. METHODS: Forty-eight Wistar rats were used into two groups (G1 and G2) subdivided into four subgroups: Sedentary (S); trained (T); AAS-treated (Deca-Durabolin(r), 5mg/kg, twice a week) sedentary rats (AAS) and AAS-treated and trained animals (AAST). Trained groups performed jumps in water: four series of 10 jumps each, followed by a 30 sec interval between the series, for seven weeks. RESULTS: Training increased ACE activity in the SFT compared to the control group (p <0.05). Both AAS and AAST groups presented higher ACE activity levels (p < 0.05). The AAST increased the ACE activity only compared to the trained animals. Only the AAST group presented significant higher levels of ACE in the serum. In the G2 group, all experimental groups presented decreased ACE activity in the serum and in the tendon, as compared to the control group. CONCLUSION: This study indicates that AAS administration and its combination with exercise increased ACE activity of tendons. AAS abuse could compromise tendon adaptation causing maladaptive remodeling.

Anabolic androgenic steroids reverse the beneficial effect of exercise on tendon biomechanics: an experimental study

BACKGROUND

The effect of anabolic androgenic steroids on tendons has not yet been fully elucidated. Aim of the present study was the evaluation of the impact of anabolic androgenic steroids on the biomechanical and histological characteristics of Achilles tendons.

METHODS

Twenty-four male Wistar rats were randomized into four groups with exercise and anabolic steroids (nandrolone decanoate) serving as variables. Protocol duration was 12 weeks. Following euthanasia, tendons' biomechanical properties were tested with the use of a modified clamping configuration. Histological examination with light and electron microscopy were also performed.

RESULTS

In the group of anabolic steroids and exercise the lowest fracture stress values were observed, while in the exercise group the highest ones. Histological examination by light and electron microscopy revealed areas of collagen dysplasia and an increased epitendon in the groups receiving anabolic steroids and exercise.

CONCLUSIONS

These findings suggest that anabolic androgenic steroids reverse the beneficial effect of exercise, thus resulting in inferior maximal stress values.

Regional molecular and cellular differences in the female rabbit Achilles tendon complex: potential implications for understanding responses to loading

The aim of this study was: (i) to analyze the morphology and expression of extracellular matrix genes in six different regions of the Achilles tendon complex of intact normal rabbits; and (ii) to assess the effect of ovariohysterectomy (OVH) on the regional expression of these genes. Female New Zealand White rabbits were separated into two groups: (i) intact normal rabbits (n = 4); and (ii) OVH rabbits (n = 8). For each rabbit, the Achilles tendon complex was dissected into six regions: distal gastrocnemius (DG); distal flexor digitorum superficialis; proximal lateral gastrocnemius (PLG); proximal medial gastrocnemius; proximal flexor digitorum superficialis; and paratenon. For each of the regions, hematoxylin and eosin staining was performed for histological evaluation of intact normal rabbit tissues and mRNA levels for proteoglycans, collagens and genes associated with collagen regulation were assessed by real-time reverse transcription-quantitative polymerase chain reaction for both the intact normal and OVH rabbit tissues. The distal regions displayed a more fibrocartilaginous phenotype. For intact normal rabbits, aggrecan mRNA expression was higher in the distal regions of the Achilles tendon complex compared with the proximal regions. Collagen Type I and matrix metalloproteinase-2 expression levels were increased in the PLG compared to the DG in the intact normal rabbit tissues. The tendons from OVH rabbits had lower gene expressions for the proteoglycans aggrecan, biglycan, decorin and versican compared with the intact normal rabbits, although the regional differences of increased aggrecan expression in distal regions compared with proximal regions persisted. The tensile and compressive forces experienced in the examined regions may be related to the regional differences found in gene expression. The lower mRNA expression of the genes examined in the OVH group confirms a potential effect of systemic estrogen on tendon.

Exhaustive exercise with different rest periods changes the collagen content and MMP-2 activation on the calcaneal tendon

Tendons adapt to different mechanical stimuli through a remodeling process involving metalloproteinases (MMPs) and collagen synthesis. The purpose of this study was to investigate the activities of MMP-2 and MMP-9 and the collagen content in tendons after exhaustive acute exercise sessions over the course of 1, 3, or 6 days, with 1-hr or 3-hr rest periods between each session. Wistar rats were grouped into control (C), trained with 1-hr (groups 1d1h, 3d1h, and 6d1h) and trained with 3-hr (groups 1d3h, 3d3h and 6d3h) groups with rest periods between the treadmill running sessions, for 1, 3, and 6 days. The analysis of MMP-2 showed a larger presence of the latent isoform in the 1d3h group and a larger presence of the active isoform in the 6d3h group compared to the control. No differences were detected for MMP-9. A lower concentration of hydroxyproline was found in the 6d3h group compared to the 6d1h group. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis showed more prominent collagen bands in the 6d3h group, which was confirmed by Western blotting for collagen type I. A higher concentration of glycosaminoglycans was observed in the 3d3h group compared to the 3d1h group, and the 6d3h group presented the highest value for non-collagenous proteins compared to other groups. In conclusion, different rest periods between exercise sessions had different effects on the composition of the calcaneal tendon because a greater activation of MMP-2 and a reduction of total collagen were observed on day 6 of exercise with 3-hr rest periods compared to 1-hr rest periods.

Gene expression in distinct regions of rat tendons in response to jump training combined with anabolic androgenic steroid administration

The aim of this study was to evaluate the expression of key genes responsible for tendon remodeling of the proximal and distal regions of calcaneal tendon (CT), intermediate and distal region of superficial flexor tendon (SFT) and proximal, intermediate and distal region of deep flexor tendon (DFT) submitted to 7 weeks of jumping water load exercise in combination with AAS administration. Wistar male rats were grouped as follows: sedentary (S), trained (jumping water load exercise) (T), sedentary animals treated with AAS (5 mg/kg, twice a week) and animals treated with AAS and trained (AAST). mRNA levels of COL1A1, COL3A1, TIMP-1, TIMP-2, MMP-2, IGF-IEa, GAPDH, CTGF and TGF-β-1 were evaluated by quantitative PCR. Our main results indicated that mRNA levels alter in different regions in each tendon of sedentary animals. The training did not alter the expression of COL1A1, COL3A, IGF-IEa and MMP-2 genes, while AAS administration or its combination with training reduced their expression. This study indicated that exercise did not alter the expression of collagen and related growth factors in different regions of rat tendon. Moreover, the pattern of gene expression was distinct in the different tendon regions of sedentary animals. Although, the RNA yield levels of CT, SFT and DFT were not distinct in each region, these regions possess not only the structural and biochemical difference, but also divergence in the expression of key genes involved in tendon adaptation.

Effects of ovariectomy and resistance training on MMP-2 activity in rat calcaneal tendon

Tendon remodeling relies on extracellular matrix (ECM) restructuring by the matrix metallopeptidases (MMPs). The aim of this study was to investigate MMP-2 activity in different regions of the calcaneal tendon (CT) after resistance training (RT) in ovariectomized rats. Wistar adult female rats were grouped into sedentary (Sed-Intact), ovariectomized sedentary (Sed-Ovx), acute exercise (AcuteEx-Intact), ovariectomized acute exercise (AcuteEx-Ovx), resistance trained (ChronicEx-Intact), and ovariectomized resistance trained (ChronicEx-Ovx) (n = 10 each group). The RT protocol required the animals to climb a 1.1-m vertical ladder with weights attached to their tail. The sessions were performed once every 3 days with 4-9 climbs and 8-12 dynamic movements per scaling. The acute groups performed one session and the chronic groups underwent 12 weeks of RT. There was an increase in total MMP-2 activity in Sed-Ovx, AcuteEx-Intact, and ChronicEx-Intact compared with that in Sed-Intact in the proximal region of CT. AcuteEx-Ovx exhibited higher total MMP-2 than Sed-Ovx and AcuteEx-Intact in the distal region of CT. Chronic-Ovx presented lower total MMP-2 activity than Sed-Ovx and Chronic-Intact in the distal region of tendon. The active MMP-2 was higher for the AcuteEx-Ovx than Sed-Ovx and AcuteEx-Intact in proximal region of tendon. There was higher active MMP-2 in the distal region of tendon in the Acute-Ovx than in the Sed-Ovx and AcuteEx-Intact. Ovariectomy and resistance exercise modulate MMP-2 activity according to specific tendon region, indicating a differentiated tissue remodeling.

Effects of ovariectomy and resistance training on MMP-2 activity in skeletal muscle

Matrix metallopeptidases (MMPs) are crucial to the maintenance of healthy tissue. The aim of this study was to investigate MMP-2 activity in gastrocnemius, soleus, tibialis anterior (TA), and extensor digitorium longus (EDL) muscle after resistance training in ovariectomized rats. Wistar adult female rats were grouped into 7 groups (n = 10 per group): sedentary (Sed-Intact); ovariectomized sedentary (Sed-Ovx); pseudo-ovariectomized sedentary (Sed-Pseudo); acute exercise (AcuteEx-Intact); ovariectomized acute exercise (AcuteEx-Ovx); strength trained (ChronicEx-Intact); and ovariectomized strength trained (ChronicEx-Ovx). A 12-week resistance training period, during which the animals climbed a 1.1-m vertical ladder with weights secured to their tails, was used. The sessions were performed once every 3 days, with 4-9 climbs and 8-12 dynamic movements per climb. The MMP-2 activity was analyzed by zymography. There was higher MMP-2 activity in soleus muscle in the ChronicEx-Intact and ChronicEx-Ovx groups, and lower MMP-2 activity in the AcuteEx-Ovx group, compared with the Sed-Intact group (p < or =0.05). The Sed-Ovx and ChronicEx-Ovx groups presented lower MMP-2 activity than the Sed-Intact group in TA. There was higher MMP-2 activity in AcuteEx-Intact and the AcuteEx-Ovx compared with the Sed-Intact and Sed-Ovx in TA, respectively (p < or = 0.05). In TA and EDL, training increased MMP-2 activity in the Sed-Intact group. No statistically significant alterations were observed for gastrocnemius muscle. Strength training increases MMP-2 activity in soleus, TA, and EDL muscle, which may be important for muscle remodeling. Ovariectomy downregulates MMP-2 in TA and EDL, which may compromise muscle function.