In vitro tenocyte metabolism in aging and oestrogen deficiency

The influence of sex is a neglected focus in rotator cuff repair: A systematic review and meta-analysis

PURPOSE

Rotator cuff (RC) disorders are the most common cause of shoulder disability. The aim of this study was to quantify the evidence on the sex-related differences in RC repair.

METHODS

A systematic review of the literature was performed in January 2023 in PubMed, Wiley Cochrane Library and Web of Science on research articles on humans with RC tears treated surgically. A meta-analysis was performed to compare results in men and women. The Downs and Black score and the modified Coleman methodology score (MCMS) were used to assess the retrieved studies.

RESULTS

A total of 39,909 patients were enroled in the 401 studies analysed (45% women, 55% men). A trend toward more sex-balanced recruitment was observed over time. Only 4% of the studies on 1.5% of the documented patients presented disaggregated outcome data and were quantitatively analysed. A tendency for lower range of motion values after surgery was found for external shoulder rotation in women, with 39.9° ± 6.9° versus 45.3° ± 4.1° in men (p = 0.066). According to Downs and Black scores, four studies were good and 12 fair, with a main MCMS score of 69/100.

CONCLUSION

There is a lack of awareness on the importance to document women- and men-specific data. Only 4% of the articles disaggregated data, and it was possible to analyse only 1.5% of the literature population, a sample which cannot be considered representative of all patients. The lack of disaggregated data is alarming and calls for action to better study men and women differences to optimise the management of RC tears. This will be necessary to provide sex-specific information that could be of clinical relevance when managing RC repair.

LEVEL OF EVIDENCE

Level IV.

The Relationship Among Probable SARCopenia, Osteoporosis and SuprasPinatus Tendon Tears in Postmenopausal Women: The SARCOSP Study

We aimed to investigate the relationship among probable sarcopenia, osteoporosis (OP) and supraspinatus tendon (SSP) tears in postmenopausal women. Postmenopausal women screened/followed for OP were recruited. Demographic data, comorbidities, exercise/smoking status, and handgrip strength values were recorded. Probable sarcopenia was diagnosed as handgrip strength values < 20 kg. Achilles and SSP thicknesses were measured using ultrasound. Among 1443 postmenopausal women, 268 (18.6%) subjects had SSP tears. Unilateral tears were on the dominant side in 146 (10.1%) and on the non-dominant side in 55 women (3.8%). In contrast to those without, women with SSP tears had older age, lower level of education, thinner SSP and lower grip strength (all p < 0.05). In addition, they had higher frequencies of hypertension, hyperlipidemia, DM, OP and probable sarcopenia, but lower exercise frequency (all p < 0.05). Binary logistic regression modeling revealed that age [odds ratio (OR): 1.046 (1.024-1.067 95% CI)], hypertension [OR: 1.560 (1.145-2.124 95% CI)], OP [OR: 1.371 (1.022-1.839 95% CI)] and probable sarcopenia [OR: 1.386 (1.031-1.861 95% CI)] were significant predictors for SSP tears (all p < 0.05). This study showed that age, presence of hypertension, probable sarcopenia and OP were related with SSP tears in postmenopausal women. To this end, although OP appeared to be related to SSP tears, SSP tear/thickness evaluation can be recommended for OP patients, especially those who have other risk factors such as older age, higher BMI, hypertension, and probable sarcopenia.

The tendon unit: biochemical, biomechanical, hormonal influences

The current literature has mainly focused on the biology of tendons and on the characterization of the biological properties of tenocytes and tenoblasts. It is still not understood how these cells can work together in homeostatic equilibrium. We put forward the concept of the "tendon unit" as a morpho-functional unit that can be influenced by a variety of external stimuli such as mechanical stimuli, hormonal influence, or pathological states. We describe how this unit can modify itself to respond to such stimuli. We evidence the capability of the tendon unit of healing itself through the production of collagen following different mechanical stimuli and hypothesize that restoration of the homeostatic balance of the tendon unit should be a therapeutic target.

Impact of aging on tendon homeostasis, tendinopathy development, and impaired healing

Aging is a complex and progressive process where the tissues of the body demonstrate a decreased ability to maintain homeostasis. During aging, there are substantial cellular and molecular changes, with a subsequent increase in susceptibility to pathological degeneration of normal tissue function. In tendon, aging results in well characterized alterations in extracellular matrix (ECM) structure and composition. In addition, the cellular environment of aged tendons is altered, including a marked decrease in cell density and metabolic activity, as well as an increase in cellular senescence. Collectively, these degenerative changes make aging a key risk factor for the development of tendinopathies and can increase the frequency of tendon injuries. However, inconsistencies in the extent of age-related degenerative impairments in tendons have been reported, likely due to differences in how "old" and "young" age-groups have been defined, differences between anatomically distinct tendons, and differences between animal models that have been utilized to study the impact of aging on tendon homeostasis. In this review, we address these issues by summarizing data by well-defined age categories (young adults, middle-aged, and aged) and from anatomically distinct tendon types. We then summarize in detail how aging affects tendon mechanics, structure, composition, and the cellular environment based on current data and underscore what is currently not known. Finally, we discuss gaps in the current understanding of tendon aging and propose key avenues for future research that can shed light on the specific mechanisms of tendon pathogenesis due to aging.

Tendon Aging

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

Mediators and Moderators of Education Plus Exercise on Perceived Improvement in Individuals With Gluteal Tendinopathy: An Exploratory Analysis of a 3-Arm Randomized Trial

OBJECTIVE: To investigate mediators and moderators of effects of an education-plus-exercise program compared to corticosteroid injections or wait and see on perceived improvement in individuals with gluteal tendinopathy. METHODS: Exploratory analysis from a clinical trial (n = 204) comparing education plus exercise, corticosteroid injection, and wait and see on global rating of change at 52 weeks. Potential mediators measured at baseline and 8 weeks were hip active abduction range, abductor muscle torque, pain self-efficacy, pain constancy, and patient-specific function. Potential moderators at baseline were Victorian Institute of Sport Assessment for gluteal tendinopathy, menopausal status, symptom duration, magnetic resonance imaging-determined tendon pathology, and pain catastrophizing. RESULTS: There is evidence from mediation analysis that the beneficial effect of education plus exercise on global rating of change relative to corticosteroid injection or wait and see may be due to changes in patient-specific function (indirect effect relative risk; 95% CI: 1.14 [1.05-1.29], 1.29 [1.12-1.58], respectively), pain constancy (1.12 [1.03-1.27], 1.2 [1.08-1.41]), and pain self-efficacy (1.1 [1.02-1.25], 1.18 [1.04-1.44])-not active hip movement/muscle torque. Moderation analysis did not support our included patient characteristics. CONCLUSION: Education plus exercise is likely to improve global rating of change for persons with gluteal tendinopathy relative to corticosteroid injection and wait and see through improvements in patient-specific function, pain self-efficacy, and reduced pain constancy. We found no evidence of differences in the effect of education plus exercise in patient subgroups based on disability, menopausal status, symptom duration, tendon pathology, or pain catastrophizing. J Orthop Sports Phys Ther 2022;52(12):826-836. Epub: 17 October 2022. doi:10.2519/jospt.2022.11261.

Age-related changes in mechanical properties of semitendinosus tendon used for anterior cruciate ligament reconstruction

Background

Hamstring tendons are a popular choice for autografts in anterior cruciate ligament (ACL) reconstruction. However, there is increasing evidence that hamstring tendon autografts carry a high risk of revision and residual instability in young patients. To elucidate the reasons for the inferior outcome of the reconstructed ACL with hamstring tendon autografts in young patients, we investigated the Young’s modulus and the extent of cyclic loading-induced slackening of the semitendinosus tendon used for ACL reconstruction across a broad range of ages.

Methods

Twenty-six male patients (aged 17–53 years), who were scheduled for ACL reconstruction surgery using the semitendinosus tendon autograft, participated in this study. The distal portion of the harvested semitendinosus tendon, which was not used to construct the autograft, was used for cyclic tensile testing to calculate the Young’s modulus and the extent of slackening (i.e., increase in slack length).

Results

Spearman correlation analysis revealed that the Young’s modulus of the semitendinosus tendon was positively correlated with the patient’s age (ρ = 0.559, P = 0.003). In contrast, the extent of tendon slackening did not correlate with the patient’s age.

Conclusions

We demonstrated that the Young’s modulus of the semitendinosus tendon increases with age, indicating that the semitendinosus tendon used for ACL reconstruction is compliant in young patients.

Orbital Aging: A Computed Tomography-Based Study of 240 Orbits

BACKGROUND

Previous studies have attempted to explain age-related changes to the orbit in isolation, often producing conflicting results. The authors used highly accurate imaging software to analyze computed tomographic scans to characterize changes related to age objectively.

METHODS

In this case-control study, patients seen in an ear, nose, and throat clinic were screened for study entry. Male and female participants were divided into two age groups (20 to 30 years and 60 to 75 years). Primary outcomes included measurement of bony orbital dimensions, volume of soft tissues (muscle and fat volume), and anterior globe position. Three-dimensional reconstructions were created of each orbit allowing these measurements. The generalized estimating equation was used so that both orbits from each patient could be included without any bias.

RESULTS

The final sample included 240 orbits from 120 patients. There were 30 patients in each age group. Among female participants, the bony orbital volume ( p < 0.05), fat volume ( p < 0.01), and central width ( p < 0.001) of the bony orbit increased with age. The anterior globe position was significantly greater in older female participants ( p < 0.01). For male participants, the fat volume ( p < 0.0001) and central height ( p < 0.03) increased with age; the lateral rim moved posteriorly with age ( p < 0.007). The anterior globe position was not different between the age groups in male participants ( p = 0.56).

CONCLUSION

The female bony orbit expands with age and is associated with a more anterior position of the globe; the male bony orbital volume remains the same and the lateral rim moves posteriorly.

Tendinopathy: sex bias starts from the preclinical development of tendon treatments. A systematic review

Tendinopathies are common overuse disorders that arise both in athletes and the general population. Available tendon treatments are used both for women and men without distinction. However, the existence of a sex-based difference in tendon biology is widely demonstrated. Since basic research represents the foundation for treatment development, an equal female–male representation should be pursued in preclinical studies. This systematic review quantified the current evidence by analyzing 150 studies on 8231 animals. Preclinical studies largely neglected the importance of sex, none analyzed sex-based differences, and only 4% of the studies reported disaggregated data suitable for the analysis of treatment results in males and females. There is an alarming female under-representation, in particular in the field of injective therapies. Despite the growing awareness on the importance of investigating treatments in both males and females, the investigated field proved resistant from properly designing studies including both sexes, and the lack of sex-representation remains critical.

Tendinopathy has sex-specific features, with sex hormones affecting tendon metabolism, structure, biomechanical properties, and injury risk.

The preclinical research on tendinopathy treatments still neglects sex-based differences, leading to translation of male data to females which may affect clinical effectiveness in women.

None of the reviewed studies looked at differences between sexes, and only 4% of the studies reported disaggregated data. Besides, female animals are under-represented.

The lack of sex-representation in tendinopathy research remains critical.

Increasing Vascular Response to Injury Improves Tendon Early Healing Outcome in Aged Rats

Tendon injuries positively correlate with patient age, as aging has significant effects on tendon homeostatic maintenance and healing potential after injury. Vascularity is also influenced by age, with both clinical and animal studies demonstrating reduced blood flow in aged tissues. However, it is unknown how aging effects vascularity following tendon injury, and if this vascular response can be modulated through the delivery of angiogenic factors. Therefore, the objective of this study is to evaluate the vascular response following Achilles tendon injury in adult and aged rats, and to define the alterations to tendon healing in an aged model following injection of angiogenic factors. It was determined that aged rat Achilles tendons have a reduced angiogenesis following injury. Further, the delivery of vascular endothelial growth factor, VEGF, caused an increase in vascular response to tendon injury and improved mechanical outcome in this aged population. This work suggests that reduced angiogenic potential with aging may be contributing to impaired tendon healing response and that the delivery of angiogenic factors can rescue this impaired response. This study was also the first to relate changes in vascular response in an aged model using in vivo measures of blood perfusion to alterations in healing properties.

The Prevalence and Risk Factors for Trigger Digits in a Random Sampling of a Japanese Population Registry between 50 and 89 Years of Age

Background: Trigger digit(s) (TD) is one of the most common disorders of the hand in the elderly population. The aim of this study is to determine the prevalence and identify the risk factors for TD in an elderly Japanese population. Methods: We randomly sampled 1,297 subjects between the ages of 50 and 89 years from the population registry of a town in Japan. About 413 subjects agreed to participate in the study, and all were examined for the presence of TD. Subjects were divided into three groups namely history of treatment for TD in the past (PTD), current evidence of TD (CTD) or both (BTD). The prevalence of TD was weighted by age according to the composition of the Japanese population. Age, female gender, obesity, hard manual work, exposure to vibration tools, sports activity, smoking, alcohol, wrist fracture, hypertension, hypothyroidism, diabetes mellitus, rheumatoid arthritis and carpal tunnel syndrome were assessed as risk factors for TD using univariate and multivariate logistic regression analysis. Results: Forty subjects had TD. This included 18, 19 and 3 subjects with PTD, CTD and BTD, respectively. The weighted prevalence of TD was 9.7% (female, 14.3%; male, 4.4%) in the Japanese population aged 50-89 years. Age 70-79 and female gender were identified as risk factors for TD. Conclusions: The random sampling of a Japanese population registry between the ages of 50 and 89 years revealed the prevalence of TD as 9.7% and identified age between 70 and 79 and female gender as risk factors for developing TD. Level of Evidence: Level II (Therapeutic).

Does Menopausal Hormone Therapy, Exercise, or Both Improve Pain and Function in Postmenopausal Women With Greater Trochanteric Pain Syndrome? A 2 × 2 Factorial Randomized Clinical Trial

BACKGROUND

Greater trochanteric pain syndrome (GTPS) is a debilitating chronic condition, most prevalent in postmenopausal women. A positive association between high estrogen levels and tendon health may exist, and postmenopausal women have reduced estrogen. Menopausal hormone therapy (MHT) may reduce the incidence of tendon abnormality, particularly when combined with exercise.

PURPOSE

To determine the effect of MHT and exercise on tendon pain and function in postmenopausal women with GTPS.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Postmenopausal women (N = 132; n = 12, lost to follow-up) with GTPS were randomized into MHT and placebo transdermal cream groups combined with tendon-specific or sham exercise. All groups received education about avoiding gluteal tendon compression and load management throughout 12 weeks of intervention. The primary outcome was the Victorian Institute of Sport Assessment for gluteal tendinopathy (VISA-G), and secondary outcomes were measured at baseline and at 12 and 52 weeks. The Global Rating of Change was assessed at 12 and 52 weeks. A linear mixed-effects model was used to assess differences. Body mass index (BMI) was included as a covariate.

RESULTS

All participant groups improved over time (baseline vs 12 weeks, P < .001; baseline vs 52 weeks, P < .001). There was no difference among exercise groups measured by all outcomes (VISA-G: baseline, P = .97, mean difference [MD] = 0.10; 12 weeks, P = .49, MD = 2.15; 52 weeks, P = .32, MD = -3.08). There was a significant interaction effect between cream and BMI; therefore, the population was stratified by BMI levels (<25, <30, ≥30). The MHT groups (with exercise and education) had significantly better VISA-G outcomes (baseline, P = .04, MD = -11.20, 95% CI = -21.70 to -0.70; 12 weeks, P < .001, MD = -20.72, 95% CI = -31.22 to -10.22; 52 weeks, P = .002, MD = -16.71, 95% CI = -27.21 to -6.22) and secondary measure scores as compared with placebo at all time points when BMI was <25.

CONCLUSION

MHT or placebo combined with tendon-specific or sham exercise plus education reduced pain and increased function for this population. For women with a BMI <25, MHT with any exercise plus education was better than placebo. A targeted exercise or sham exercise strategy is effective when prescribed with education about avoiding gluteal tendon compression and load management.

REGISTRATION

ACTRN12614001157662 (Australian New Zealand Clinical Trials Registry).

The effect of estrogen-like compound on rotator cuff tendon healing in a murine model

Estrogen deficiency has been shown to negatively influence rotator cuff tendon healing. Therefore, the addition of an estrogen-like-compound (ELC) in a nonestrogen-deficient animal may improve the quality of a rotator cuff repair. The purpose of this study was to evaluate the effects of an ELC, diethylstilbestrol (DES), on tendon healing in a murine rotator cuff repair model. Thirty-three male wild-type mice (C57BL/6NJ) were randomly divided into three study groups. Group 1-unoperated mice with normal rotator cuff tendons. Groups 2 and 3 consisted of surgically repaired rotator cuff tendons; Group 2 (repair-only) was the standard repair group (no DES injected), whereas Group 3 (repair + DES) was the experimental repair group (injected with DES). Comparing the maximal thickness of calcified fibrocartilage to uncalcified fibrocartilage, the ratios for the control (intact tendon), repair-only, and repair + DES groups were 2:1, 0.9:1, and 1.7:1. RNA expression data demonstrated upregulation of chondrogenic, angiogenic, and tendon modulation genes in the repair- only group compared to the control (intact tendon) group (p < 0.04 for all), and that addition of DES further increased the osteogenic, angiogenic, and tendon modulation gene expression compared to the repair-only group (p < 0.02). Immunohistochemical analysis indicated that the addition of DES further increased osteogenic, angiogenic, and tendon maturation protein expression at the enthesis compared to standard repairs.

The role of estrogen and progesterone receptors in the rotator cuff disease: a retrospective cohort study

Background

Rotator cuff (RC) tears represent a common cause of shoulder pain and dysfunction in adults. The disease affects primarily women and occurs mainly in the postmenopausal period.

This study aimed to investigate immunohistochemically the presence of estrogen receptor-alpha (ER-⍺), estrogen receptor-beta (ER-β) and progesterone receptor (PR) in the supraspinatus tendon of patients with RC tendinopathy, searching for gender differences of expression. A secondary aim was to evaluate potential links between their expression and the typical histopathological findings of the ailment.

Methods

Biopsies of the supraspinatus tendon were collected intraoperatively from 15 postmenopausal women and 9 men undergoing RC surgery. Specimens were stained with Haematoxylin/Eosin, Masson-Goldner Trichrome, Alcian Blu and immunohistochemical stainings for ER-⍺, ER-β and PR were performed. Tendon alterations were evaluated with the Bonar histopathological scale. Statistical tests used in this study were the Spearman correlation coefficient and the Mann-Whitney U test.

Results

In the supraspinatus tendon, cells expressed ER-⍺ (p = 0.043), ER-β (p = 0.048) and PR (p = 0.004) with statistically significant differences related to age and sex of patients. Immunoreactivity was seen in the nuclei of tenocytes and vascular cells. Postmenopausal women’s samples showed a markedly higher expression of these receptors compared to their male counterpart. There was a positive correlation between the expression of ER-⍺ and ER-β (r = 0.59; p = 0.02) and between ER-β and PR (r = 0.72; p = 0.002) in women’s samples. Furthermore, in postmenopausal women the PR expression decreased with age (r = − 0.56; p = 0.027). Only in women, the ER-β expression positively correlated with the total Bonar histopathological score (p = 0.019) and the ER-β vascular expression positively correlated with ground substance alterations (p = 0.029).

Conclusions

These results reveal that ERs and PR are present in the supraspinatus tendon of patients with RC tears, suggesting a role of sex hormones in the pathogenesis of the disease.

Pregnancy and Lactation Impair Subchondral Bone Leading to Reduced Rat Supraspinatus Tendon-to-Bone Insertion Site Failure Properties

Pregnant women experience weight gain, gait changes, and biochemical fluctuations that impair joint function and alter the maternal skeleton. Hormonal changes increase pelvic ligament laxity in preparation for childbirth and affect peripheral joint laxity. Calcium demands also rise during pregnancy and lactation, resulting in reduced bone mineral density (BMD) and maternal bone loss. Altered tendon properties and bone loss during pregnancy and lactation may impact tendon insertion sites, such as rotator cuff tendons where insertion site ruptures are common. However, the effects of pregnancy and lactation at the tendon-to-bone interface have not been investigated. Therefore, the objective of this study was to evaluate supraspinatus tendon mechanical properties and insertion site microstructure during pregnancy, lactation, and postweaning recovery in female rats. We hypothesized that pregnancy and lactation would compromise supraspinatus tendon mechanical properties and subchondral bone microstructure. Female rats were divided into virgin, pregnancy, lactation, and recovery groups, and supraspinatus tendons were mechanically evaluated. Surprisingly, tendon mechanics was unaffected by pregnancy and lactation. However, tendon modulus decreased two-weeks postweaning. Additionally, tendons failed by bony avulsion at the insertion site, and the lactation group exhibited reduced failure properties corresponding to decreased subchondral bone mineralization. Lactation also resulted in dramatic bone loss at the epiphysis, but trabecular bone microarchitecture recovered postweaning. In conclusion, lactation following pregnancy impaired trabecular bone microstructure and subchondral bone mineralization, leading to reduced supraspinatus tendon-to-bone insertion site failure properties. These findings will contribute toward understanding the pathogenesis of tendon-to-bone disorders.

Association of estrogen receptor β polymorphisms with posterior tibial tendon dysfunction

Posterior tibial tendon (PTT) dysfunction is three times more common in females, and some patients may have a predisposition without a clinically evident cause, suggesting that individual characteristics play an important role in tendinopathy. The present study investigated the association of rs4986938 (+ 1730G > A; AluI RFLP) and rs1256049 (- 1082G > A; RsaI RFLP) single nucleotide polymorphisms (SNPs) of estrogen receptor-beta (ER-β) gene with PTT dysfunction. A total of 400 participants were recruited. The PTT dysfunction group: these patients underwent surgery, with PTT tendinopathy confirmed by histopathology and magnetic resonance image (MRI). The control group was composed of participants with no clinical or MRI evidence of PTT dysfunction. Each group was composed of 100 postmenopausal women, 50 premenopausal women, and 50 men. Genomic DNA was extracted from saliva samples, and genotypes were obtained by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Concerning the ER-β SNP rs4986938, there were significant differences in the frequencies of alleles between test and control groups of all the cases, only postmenopausal women and only men (p < 0.0001, p = 0.0016 and p = 0.0001). Considering the PTT dysfunction group and comparing postmenopausal women versus premenopausal women adding men, the analysis showed significant differences in the allelic distribution (p = 0.0450): the allele A in postmenopausal women is a risk factor. The ER-β SNP rs1256049 did not show differences in the frequencies of alleles and genotypes between groups. The ER-β SNP rs4986938, but not ER -β SNPs rs1256049, may contribute to PTT insufficiency in the Brazilian population, with additional risk in postmenopausal women. Addition, in men the genetic factor could be more determinant.

The Impact of Genistein Supplementation on Tendon Functional Properties and Gene Expression in Estrogen-Deficient Rats

Tendinopathy risk increases with menopause. The phytoestrogen genistein prevents collagen loss during estrogen deficiency (ovariectomy [OVX]). The influence of genistein on tendon function and extracellular matrix (ECM) regulation is not well known. We determined the impact of genistein on tendon function and the expression of several genes important for the regulation of tendon ECM. Eight-week-old rats (n = 42) were divided into three groups: intact, OVX, or OVX-genistein (6 mg/kg/day) for 6 weeks. Tail fascicles were assessed with a Deben tensile stage. Achilles tendon mRNA expression was determined with digital droplet polymerase chain reaction. Compared to intact, fascicle stress tended to be lower in untreated OVX rats (P = .022). Furthermore, fascicle modulus and energy density were greater in genistein-treated rats (P < .05) compared to intact. Neither OVX nor genistein altered expression of Col1a1, Col3a1, Casp3, Casp8, Mmp1a, Mmp2, or Mmp9 (P > .05). Compared to intact, Tnmd and Esr1 expression were greater and Pcna and Timp1 expression were lower in OVX rats (P < .05). Genistein treatment returned Tnmd, Pcna, and Timp1 to levels of intact-vehicle (P < .05), but did not alter Scx or Esr1 (P > .05). Several β-catenin/Wnt signaling-related molecules were not altered by OVX or genistein (P > .05). Our findings demonstrate that genistein improves tendon function in estrogen-deficient rats. The effect of genistein in vivo was predominately on genes related to cell proliferation rather than collagen remodeling.

Supraspinatus Tendons Have Different Mechanical Properties Across Sex

Sex differences in the mechanical properties of different musculoskeletal tissues and their impact on tendon function and disease are becoming increasingly recognized. Tendon mechanical properties are influenced by the presence or absence of sex hormones and these effects appear to be tendon- or ligament-specific. The objective of this study was to determine how sex and hormone differences in rats affect supraspinatus tendon and muscle properties. We hypothesized that male supraspinatus tendons would have increased cross-sectional area but no differences in tendon material properties or muscle composition when compared to supraspinatus tendons from female or ovariectomized (OVX) female rats. Uninjured supraspinatus tendons and muscles from male, female, and OVX female rats were collected and mechanical and histological properties were determined. Our analysis demonstrated decreased dynamic modulus and increased hysteresis and cross-sectional area in male tendons. We found that male tendons exhibited decreased dynamic modulus (during low strain frequency sweep and high strain fatigue loading), increased hysteresis, and increased cross-sectional area compared to female and OVX female tendons. Despite robust mechanical differences, tendon cell density and shape, and muscle composition remained unchanged between groups. Interestingly, these differences were unique compared to previously reported sex differences in rat Achilles tendons, which further supports the concept that the effect of sex on tendon varies anatomically. These differences may partially provide a mechanistic explanation for the increased rate of acute supraspinatus tendon ruptures seen in young males.

Factors associated with positive outcomes of platelet-rich plasma therapy in Achilles tendinopathy

BACKGROUND

The efficacy of platelet-rich plasma in the treatment for Achilles tendinopathy is debated. Therefore, it is important to know which factors, related to the subjects and/or the disease, are associated with positive or negative outcomes. Aim of this study was to evaluate in a large cohort of patients with Achilles mid-portion tendinopathy which variables were independently associated with a positive outcome after platelet-rich plasma treatment.

MATERIAL AND METHODS

Eighty-four subjects with Achilles tendinopathy were evaluated by means of VISA-A score and ultrasound and treated with a single platelet-rich plasma injection once a week for 3 weeks. Afterward, a rehabilitation program, based on eccentric training, was implemented. At 3 and 6 months, the relationship between the mean VISA-A score and the following putative predictors was evaluated: sex, age, physical activity, sport, smoking, metabolic risk factors, BMI, symptoms duration, tendon damage, neovessels, adherence to eccentric training. Finally, the percentage of clinically evident positive outcomes (defined as an increase in VISA-A score ≥ 20 points) related to each variable was computed.

RESULTS

At final follow-up, using the General Linear Model for Repeated Measures procedure, male sex (0.02), age ≤ 40 (0.05) and adequate eccentric training (0.02) were found to be independently associated with a significant increase in the mean VISA-A score. Moreover, the clinically evident positive outcomes, as previously defined, were significantly associated with male sex (0.01), age ≤ 40 (0.000), BMI ≤ 25 (0.001), symptoms duration ≤ 12 months (0.02) and good adherence to eccentric training (0.004).

CONCLUSION

Younger age, male sex and good adherence to eccentric training can be considered predictors of better results after platelet-rich plasma therapy in Achilles tendinopathy.

Biology of Tendon Stem Cells and Tendon in Aging

Both tendon injuries and tendinopathies, particularly rotator cuff tears, increase with tendon aging. Tendon stem cells play important roles in promoting tendon growth, maintenance, and repair. Aged tendons show a decline in regenerative potential coupled with a loss of stem cell function. Recent studies draw attention to aging primarily a disorder of stem cells. The micro-environment (“niche”) where stem cells resided in vivo provides signals that direct them to metabolize, self-renew, differentiate, or remain quiescent. These signals include receptors and secreted soluble factors for cell-cell communication, extracellular matrix, oxidative stress, and vascularity. Both intrinsic cellular deficits and aged niche, coupled with age-associated systemic changes of hormonal and metabolic signals can inhibit or alter the functions of tendon stem cells, resulting in reduced fitness of these primitive cells and hence more frequent injuries and poor outcomes of tendon repair. This review aims to summarize the biological changes of aged tendons. The biological changes of tendon stem cells in aging are reviewed after a systematic search of the PubMed. Relevant factors of stem cell aging including cell-intrinsic factors, changes of microenvironment, and age-associated systemic changes of hormonal and metabolic signals are examined, with findings related to tendon stem cells highlighted when literature is available. Future research directions on the aging mechanisms of tendon stem cells are discussed. Better understanding of the molecular mechanisms underlying the functional decline of aged tendon stem cells would provide insight for the rational design of rejuvenating therapies.

Absence of estrogen receptor beta leads to abnormal adipogenesis during early tendon healing by an up-regulation of PPARγ signalling

Achilles tendon injury is one of the challenges of sports medicine, the aetiology of which remains unknown. For a long time, estrogen receptor β (ERβ) has been known as a regulating factor of the metabolism in many connective tissues, such as bone, muscle and cartilage, but little is known about its role in tendon. Recent studies have implicated ERβ as involved in the process of tendon healing. Tendon-derived stem cells (TDSCs) are getting more and more attention in tendon physiological and pathological process. In this study, we investigated how ERβ played a role in Achilles tendon healing. Achilles tendon injury model was established to analyse how ERβ affected on healing process in vivo. Cell proliferation assay, Western blots, qRT-PCR and immunocytochemistry were performed to investigate the effect of ERβ on TDSCs. Here, we showed that ERβ deletion in mice resulted in inferior gross appearance, histological scores and, most importantly, increased accumulation of adipocytes during the early tendon healing which involved activation of peroxisome proliferator-activated receptor γ (PPARγ) signalling. Furthermore, in vitro results of ours confirmed that the abnormity might be the result of abnormal TDSC adipogenic differentiation which could be partially reversed by the treatment of ERβ agonist LY3201. These data revealed a role of ERβ in Achilles tendon healing for the first time, thereby providing a new target for clinical treatment of Achilles tendon injury.

The Potential Roles of Tendon Stem/Progenitor Cells in Tendon Aging

Aging is a key dangerous factor for the occurrence and severity of tendon injury, but the exact cognition of the relationship is elusive at present. More previous studies suggest age-related changes occur at tendon mechanical properties, structure and composition, but the pathological alternations may be overlooked, which might be a cause for the structure and function variations, and even speed up the progress of age-related disorders. Recently, the presence of tendon stem/progenitor cells (TSPCs) would provide new insights for the pathogenesis of tendon aging. In this review, the tendon mechanical properties, structure and composition are presented in brief, then, the pathological changes of the aging tendon are described firstly, and the latest researches on alterations of TSPCs in the pathogenesis of tendon aging have also been analyzed. At a cellular level, the hypothetical model of altered TSPCs fate for tendon aging is also proposed. Moreover, the regulation of TSPCs as a potential way of the therapies for age-related tendon diseases is discussed. Therefore, reversing the impaired function of TSPCs and promoting the tenogenic differentiation of TSPCs could become hot spots for further study and give the opportunity to establish new treatment strategies for age-related tendon injuries.

Effects of Estrogen-Deficient State on Rotator Cuff Healing

BACKGROUND

Rotator cuff retears after surgical repair are a concern, despite advances in operative techniques, but few studies have investigated the effects of the estrogen-deficient state on tendon-to-bone healing at the repair site.

PURPOSE

We evaluated the effect of the estrogen-deficient state on tendon-to-bone healing after rotator cuff repair in an ovariectomized rat model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Female Sprague Dawley rats underwent detachment and immediate repair of the supraspinatus tendon. Surgery was performed in 24 rats at 4.5 weeks of age 17 weeks after ovariectomy (OVX group) and in 24 age-matched control rats without ovariectomy (control group). Animals were sacrificed at 2, 4, 8, and 12 weeks after surgery for biomechanical and histological evaluations of reattachment. Bone mineral density (BMD) at the insertion site and cancellous bone in the humeral head was assessed by micro-computed tomography.

RESULTS

BMD was significantly lower both at the insertion site and in cancellous area in the OVX group than in the control group at weeks 2 to 12. Ultimate load to failure, ultimate stress, linear stiffness, and the Young modulus were significantly lower in the OVX group than in the control group at 2 and 4 weeks, but the difference was no longer significant at 8 and 12 weeks. At 2 and 4 weeks, relatively immature granulation tissue was observed in the OVX group compared with the control group. At 8 and 12 weeks after surgery, there were differences in the tendon-bone interface in the 2 groups: Direct insertion with well-established chondroid tissue was seen in the control group, and indirect insertion without chondroid tissue was seen in the OVX group. Consistently, the amount of chondroid tissue was greater and collagen organization was better in the control group than in the OVX group. Cells expressing cathepsin K were significantly more numerous both at the insertion site and in cancellous bone in the OVX group than in the control group.

CONCLUSION

The estrogen-deficient state by ovariectomy, compared with control rats, led to decreased biomechanical properties and poor development of chondroid tissue that influenced the repair of the tendon insertion after surgery.

CLINICAL RELEVANCE

Agents that modulate bone metabolism might improve tendon-to-bone healing in patients with an estrogen-deficient state, such as postmenopausal women who undergo rotator cuff surgery.

ERα PvuII and XbaI polymorphisms in postmenopausal women with posterior tibial tendon dysfunction: a case control study

Background

Posterior tibial tendon (PTT) insufficiency is considered as the main cause of adult acquired flat foot and is three times more frequent in females. High estrogen levels exert a positive effect on the overall collagen synthesis in tendons. We have previously demonstrated the association between some genetic single-nucleotide polymorphism (SNP) and tendinopathy. In the present study, we investigated the association of PvuII c454-397T>C (NCBI ID: rs2234693) and XbaI c454-351A>G (NCBI ID: rs9340799) SNPs in estrogen receptor alfa (ER-α) gene with PPT dysfunction.

Methods

A total of 92 female subjects with PTT dysfunction, with histopathological examination of the tendon and magnetic resonance image (MRI) evidence of tendinopathy, were compared to 92 asymptomatic females who presented an intact PPT at MRI for PvuII and XbaI SNPs in the ER-α gene. Genomic DNA was extracted from saliva and genotypes were obtained by polymerase chain reaction restriction fragment length polymorphism.

Results

The analysis of PvuII SNPs showed no significant differences in the frequency of alleles and genotypes between control and PTT dysfunction groups. The XbaI SNPs in the ER-α gene showed significant differences in the frequency of genotypes between control and test groups (p = 0.01; OR 95% 1.14 (0.55–2.33).

Conclusions

The XbaI SNP in the ERα gene may contribute to tendinopathy, and the A/A genotype could be a risk factor for PTT tendinopathy in this population. The PvuII SNP studied was not associated with PTT tendinopathy.

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.

A Comparative Study to Evaluate the Risk Factors for Medium-Sized Rotator Cuff Tear in Patients Younger Than 50 Years of Age

PURPOSE

The purpose of this study was to evaluate preoperative and intraoperative factors associated with rotator cuff tears (RCTs) among patients younger than 50 years and to compare arthroscopic rotator cuff repair (RCR) results in patients younger than 50 years (group A) and patients older than 70 years (group B). We also analyzed the results after arthroscopic RCR in these 2 age groups.

METHODS

Data were collected from 56 patients allocated to group A and 55 patients allocated to group B who had medium-sized RCTs and had undergone arthroscopic RCR between January 2006 and August 2015. Preoperative variables included demographic data, radiologic data, and surgical procedure. We evaluated fatty degeneration on preoperative magnetic resonance imaging (MRI) and intraoperative variables, including concomitant subscapularis repair, as well as repair technique. Pain visual analog scale, functional visual analog scale, American Shoulder and Elbow Surgeons, and Constant scores were documented to compare functional results in each age group. Postoperative MRI scans were conducted to evaluate the retear rate after RCR after a mean postoperative duration of 5.4 months (range, 2-48 months).

RESULTS

Multivariate regression analysis showed acute-on-chronic injury and a history of hypertension were independent factors for differentiation of the groups. Stepwise regression analysis found sex, hypertension, and fatty infiltration of the supraspinatus and infraspinatus to be comparable factors for each group. All patients showed improved results after arthroscopic RCR, but there was no difference between the 2 groups in functional outcomes. However, cuff retears on postoperative MRI scans were found in only 3.9% of the patients in group A versus 16% of the patients in group B.

CONCLUSIONS

The results of this study showed that sex, acute-on-chronic injury, and preoperative fatty infiltration of the rotator cuff were significant factors affecting medium-sized RCTs in patients younger than 50 years. In addition, there were no significant differences in functional outcomes after arthroscopic RCR in both groups at 2 years, but postoperative MRI showed a lower retear rate in group A.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The impact of loading, unloading, ageing and injury on the human tendon

A tendon transfers force from the contracting muscle to the skeletal system to produce movement and is therefore a crucial component of the entire muscle-tendon complex and its function. However, tendon research has for some time focused on mechanical properties without any major appreciation of potential cellular and molecular changes. At the same time, methodological developments have permitted determination of the mechanical properties of human tendons in vivo, which was previously not possible. Here we review the current understanding of how tendons respond to loading, unloading, ageing and injury from cellular, molecular and mechanical points of view. A mechanistic understanding of tendon tissue adaptation will be vital for development of adequate guidelines in physical training and rehabilitation, as well as for optimal injury treatment.

Multiscale Poroviscoelastic Compressive Properties of Mouse Supraspinatus Tendons Are Altered in Young and Aged Mice

Rotator cuff disorders are one of the most common causes of shoulder pain and disability in the aging population but, unfortunately, the etiology is still unknown. One factor thought to contribute to the progression of disease is the external compression of the rotator cuff tendons, which can be significantly increased by age-related changes such as muscle weakness and poor posture. The objective of this study was to investigate the baseline compressive response of tendon and determine how this response is altered during maturation and aging. We did this by characterizing the compressive mechanical, viscoelastic, and poroelastic properties of young, mature, and aged mouse supraspinatus tendons using macroscale indentation testing and nanoscale high-frequency AFM-based rheology testing. Using these multiscale techniques, we found that aged tendons were stiffer than their mature counterparts and that both young and aged tendons exhibited increased hydraulic permeability and energy dissipation. We hypothesize that regional and age-related variations in collagen morphology and organization are likely responsible for changes in the multiscale compressive response as these structural parameters may affect fluid flow. Importantly, these results suggest a role for age-related changes in the progression of tendon degeneration, and we hypothesize that decreased ability to resist compressive loading via fluid pressurization may result in damage to the extracellular matrix (ECM) and ultimately tendon degeneration. These studies provide insight into the regional multiscale compressive response of tendons and indicate that altered compressive properties in aging tendons may be a major contributor to overall tendon degeneration.

Possible association of oestrogen and Cryba4 with masticatory muscle tendon-aponeurosis hyperplasia

OBJECTIVE

Masticatory muscle tendon-aponeurosis hyperplasia, which is associated with limited mouth opening, progresses very slowly from adolescence. The prevalence rates of this disease are higher among women than among men, suggesting oestrogen involvement. As parafunctional habits are frequently observed, mechanical stress is likely involved in the pathogenesis and advancement of this disease. To elucidate the pathological condition, we examined the effect of oestrogen on tenocyte function and the relationship between mechanical stress and crystallin beta A4 (Cryba4), using murine TT-D6 tenocytes.

MATERIALS AND METHODS

Cell proliferation assays, RT-PCR, real-time RT-PCR, Western blot analysis and mechanical loading experiments were performed.

RESULTS

The physiological dose of oestrogen increased the levels of scleraxis and tenomodulin in TT-D6 tenocytes. In contrast, forced expression of Cryba4 inhibited scleraxis expression in these cells. Surprisingly, oestrogen significantly promoted cell differentiation in the Cryba4-overexpressing TT-D6 tenocytes. Moreover, tensile force induced Cryba4 expression in these tendon cells.

CONCLUSION

Oestrogen and Cryba4 may be associated with the progression of masticatory muscle tendon-aponeurosis hyperplasia.

Donor age affects proteome composition of tenocyte-derived engineered tendon

Background

The concept of tissue engineering is to deliver to the injury site biological scaffolds carrying functional cells that will enhance healing response. The preferred cell source is autologous in order to reduce immune response in the treated individual. However, in elderly patients age-related changes in synthetic activity of the implanted cells and subsequent alterations in tissue protein content may affect therapeutic outcomes. In this study we investigated the effect of donor age on proteome composition of tenocyte-derived tendon tissue-engineered constructs.

Results

Liquid chromatography tandem mass spectrometry was used to assess the proteome of tissue-engineered constructs derived from young and old equine tenocytes. Ageing was associated with altered extracellular matrix composition, especially accumulation of collagens (type I, III and XIV), and lower cytoskeletal turnover. Proteins involved in cell responsiveness to mechanical stimuli and cell-extracellular matrix interaction (calponin 1, palladin, caldesmon 1, cortactin) were affected.

Conclusions

This study demonstrated significant changes in proteome of engineered tendon derived from young and old tenocytes, indicating the impact of donor age on composition of autologous constructs.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0414-5) contains supplementary material, which is available to authorized users.

The effect of estrogen on tendon and ligament metabolism and function

Tendons and ligaments are crucial structures inside the musculoskeletal system. Still many issues in the treatment of tendon diseases and injuries have yet not been resolved sufficiently. In particular, the role of estrogen-like compound (ELC) in tendon biology has received until now little attention in modern research, despite ELC being a well-studied and important factor in the physiology of other parts of the musculoskeletal system. In this review we attempt to summarize the available information on this topic and to determine many open questions in this field.

Genetic and familial predisposition to rotator cuff disease: a systematic review

BACKGROUND

Rotator cuff disease is a common disorder leading to shoulder pain and loss of function. Its etiology in atraumatic cases is uncertain and is likely to extend beyond repetitive microtrauma or overuse. Our objective was to determine whether there is a genetic or familial predisposition to rotator cuff disease.

METHODS

A literature search of PubMed and Embase databases identified 251 citations. After review of the titles, abstracts, and full articles, 7 met our inclusion and exclusion criteria.

RESULTS

Four studies assessed familial predisposition to rotator cuff disease. One of these demonstrated that siblings of an individual with a rotator cuff tear were more likely to develop a full-thickness tear and more likely to be symptomatic. A 5-year follow-up showed that the relative risks were increased for the siblings to have a full-thickness tear, for a tear to progress in size, and for being symptomatic. Another study demonstrated that a significantly higher number of individuals with tears had family members with a history of tears or surgery than those without tears did. The other 3 studies investigated whether a genetic predisposition to rotator cuff disease exists and found significant association of haplotypes in DEFB1, FGFR1, FGF3, ESRRB, and FGF10 and 2 single-nucleotide polymorphisms within SAP30BP and SASH1.

CONCLUSION

Prior studies provide preliminary evidence for genetic and familial predisposition to rotator cuff disease. However, there is a lack of large genome-wide studies that can provide more definitive information and guide early detection of individuals at risk, prophylactic rehabilitation, and potential gene therapies and regenerative medicine interventions.

Combined supplementation of ascorbic acid and thyroid hormone T3 affects tenocyte proliferation. The effect of ascorbic acid in the production of nitric oxide

BACKGROUND

Tissue engineering is now increasingly focusing on cell-based treatments as promising tools to improve tendon repair. However, many crucial aspects of tendon biology remain to be understood before adopting the best experimental approach for cell-tissue engineering.

METHODS

The role played by Ascorbic Acid (AA) alone and in combination with thyroid hormone T₃ in the viability and proliferation of primary human tendon-derived cells was investigated. Human tenocyte viability was detected by Trypan blue exclusion test and cellular proliferation rate was evaluated by CFSE CellTrace™. In addition, the potential role of the AA in the production of Nitric Oxide (NO) was also examined.

RESULTS

In this in vitro model, an increase in tenocyte proliferation rate was observed as a consequence of progressively increased concentrations of AA (from 10 to 50 µg/ml). The addition of the T₃ hormone to the culture further increased tenocyte proliferation rate. In detail, the most evident effect on cellular growth was achieved using the combined supplementation of 50 µg/ml AA and 10^-7 M T₃.

CONCLUSION

We showed that the highest concentration of AA (100 and 500 µg/ml) caused cytotoxicity to human tenocytes. Moreover, it was shown that AA reduces NO synthesis. These results show that AA is a cell proliferation inducer that triggers tenocyte growth, while it reduces NO synthesis.

Follow-up of surgical and minimally invasive treatment of Achilles tendon pathology: a brief diagnostic imaging review

The follow-up of an operated tendon is primarily clinical, although clinical examination may not be sufficient in the presence of certain complications. The imaging techniques are of great value not only in the diagnosis of tendon pathologies, but also as an adjunct to clinical evaluation. This is particularly true in the follow-up of patients submitted to surgical tendon reconstruction, by monitoring morphological effects of different interventions and evaluating tendon healing processes. Interpretation of imaging findings requires knowledge of the imaging appearance of the operated tendon during the healing phase, to distinguish between normal postsurgical changes and real pathology, as well as knowledge of surgical technique, postoperative course (including type of prescribed therapy) and possible postoperative complications. The most important imaging modalities to examine the Achilles tendon are ultrasound and magnetic resonance imaging. This article gives a review of some of the most common treatment strategies for Achilles tendon pathology, expected postoperative imaging findings and postoperative complications.

Effect of aging and exercise on the tendon

Here, we review the literature on how tendons respond and adapt to ageing and exercise. With respect to aging, there are considerable changes early in life, but this seems to be maturation rather than aging per se. In vitro data indicate that aging is associated with a decreased potential for cell proliferation and a reduction in the number of stem/progenitor-like cells. Further, there is persuasive evidence that turnover in the core of the tendon after maturity is very slow or absent. Tendon fibril diameter, collagen content, and whole tendon size appear to be largely unchanged with aging, while glycation-derived cross-links increase substantially. Mechanically, aging appears to be associated with a reduction in modulus and strength. With respect to exercise, tendon cells respond by producing growth factors, and there is some support for a loading-induced increase in tendon collagen synthesis in humans, which likely reflects synthesis at the very periphery of the tendon rather than the core. Average collagen fibril diameter is largely unaffected by exercise, while there can be some hypertrophy of the whole tendon. In addition, it seems that resistance training can yield increased stiffness and modulus of the tendon and may reduce the amount of glycation. Exercise thereby tends to counteract the effects of aging.

Postinjury biomechanics of Achilles tendon vary by sex and hormone status

Achilles tendon ruptures are common injuries. Sex differences are present in mechanical properties of uninjured Achilles tendon, but it remains unknown if these differences extend to tendon healing. We hypothesized that ovariectomized females (OVX) and males would exhibit inferior postinjury tendon properties compared with females. Male, female, and OVX Sprague-Dawley rats (n = 32/group) underwent acclimation and treadmill training before blunt transection of the Achilles tendon midsubstance. Injured hindlimbs were immobilized for 1 wk, followed by gradual return to activity and assessment of active and passive hindlimb function. Animals were euthanized at 3 or 6 wk postinjury to assess tendon structure, mechanics, and composition. Passive ankle stiffness and range of motion were superior in females at 3 wk; however, by 6 wk, passive and active function were similar in males and females but remained inferior in OVX. At 6 wk, female tendons had greater normalized secant modulus, viscoelastic behavior, and laxity compared with males. Normalized secant modulus, cross-sectional area and tendon glycosaminoglycan composition were inferior in OVX compared with females at 6 wk. Total fatigue cycles until tendon failure were similar among groups. Postinjury muscle fiber size was better preserved in females compared with males, and females had greater collagen III at the tendon injury site compared with males at 6 wk. Despite male and female Achilles tendons withstanding similar durations of fatigue loading, early passive hindlimb function and tendon mechanical properties, including secant modulus, suggest superior healing in females. Ovarian hormone loss was associated with inferior Achilles tendon healing.

Photobiomodulation therapy on collagen type I and III, vascular endothelial growth factor, and metalloproteinase in experimentally induced tendinopathy in aged rats

This study investigates the effect of photobiomodulation therapy (PBMT) on collagen type I and III, matrix metalloproteinase (MMP), and vascular endothelial growth factor (VEGF) in experimentally induced tendinopathy in female aged rats. Tendinopathy was induced by the Achilles tendoncollagenase peritendinous. Forty-two Wistar rats (Norvegicus albinus) were used; groups consisted of 36 aged animals (18 months old; mean body weight, 517.7 ± 27.54 g) and 6 adult animals (12 weeks old; mean body weight, 266± 19.30 g). The animals were divided into three groups: control, aged tendinopathy, and aged tendinopathy PBMT; the aged groups were subdivided based on time to euthanasia: 7, 14, and 21 days. PBMT involved a gallium-arsenide-aluminum laser (Theralaser, DMC®) with active medium operating at wavelength 830 ± 10 nm, 50 mW power, 0.028 cm² laser beam, 107 J/cm² energy density, 1.8 W/cm² power density, and an energy of 3 J per point. The laser was applied by direct contact with the left Achilles tendon during 60 s per point at a frequency of three times per week, until the euthanasia date (7, 14, and 21 days). VEGF, MMP-3, and MMP-9 were analyzed by immunohistochemistry, and collagen type I and III by Sirius red. PBMT increased the deposition of collagen type I and III in a gradual manner, with significant differences relative to the group aged tendonitis (p < 0.001), and in relation to VEGF (p < 0.001); decreased expression of MMP-3 and 9 were observed in group aged tendinopathy (p < 0.001). PBMT, therefore, increased the production of collagen type I and III, downregulated the expression of MMP-3 and MMP-9, and upregulated that of VEGF, with age and age-induced hormonal deficiency.

Mesenchymal stem cells for tendon healing: what is on the horizon?

Tendon injuries are a noteworthy morbidity but at present there are few effective scientifically proven treatments. In recent decades, a number of new strategies including tissue engineering with mesenchymal stem cells (MSCs) have been proposed to enhance tendon healing. Although MSCs are an interesting and promising approach, many questions regarding their use in tendon repair remain unanswered. This descriptive overview of the literature of the last decade explores the in vivo studies on tendon healing, in small and large animal models, which used MSCs harvested from different tissues, and the state of the art in clinical applications. It was observed that there are still doubts about the optimum amount of MSCs to use and their source and the type of scaffolds to deliver the cells. Thus, further studies are needed to determine the best protocol for MSC use in tendon healing. Copyright © 2016 John Wiley & Sons, Ltd.

Does menopausal hormone therapy (MHT), exercise or a combination of both, improve pain and function in post-menopausal women with greater trochanteric pain syndrome (GTPS)? A randomised controlled trial

BACKGROUND

Greater trochanteric pain syndrome (GTPS) is pathology in the gluteus medius and minimus tendons and trochanteric bursa that causes debilitating tendon pain and dysfunction, particularly in post-menopausal women. Limited evidence in clinical studies suggests hormone changes after menopause may have a negative effect on tendon. This protocol describes a randomised controlled trial comparing the effectiveness of menopausal hormone therapy (MHT) and exercise therapy in reducing pain and dysfunction associated with GTPS in post-menopausal women.

METHOD

One hundred and sixteen post-menopausal women will be recruited and randomised to receive one of two exercise programs (sham or targeted intervention exercise) and transdermal creams (MHT cream containing oestradiol 50mcg and norethisterone acetate 140mcg or placebo cream). Interventions will be 12-weeks in duration and outcomes will be examined at baseline, 12-weeks and 52-weeks. The primary outcome measure will be the VISA-G questionnaire and secondary outcomes measures will include three hip pain and function questionnaires (Hip dysfunction and Osteoarthritis Outcome Score, Oxford Hip Score, Lateral Hip Pain questionnaire), a global change in symptom questionnaire (using a 15-point Likert scale) and a quality of life measure (AQoL-8D questionnaire). Data will be analysed using the intention to treat principle.

DISCUSSION

This study is the first randomised controlled trial to compare the effectiveness of menopausal hormone therapy therapy alone, and with the combination of exercise therapy, to treat pain and dysfunction associated with GTPS. This study has been pragmatically designed to ensure that the interventions in this study can be integrated into policy and clinical practice if found to be effective in the treatment of GTPS in post-menopausal women. If successful, there is potential for this treatment regimen to be explored in future studies of other persistent tendon conditions in the post-menopausal population.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12614001157662 Registered 31 October 2014.

Males have Inferior Achilles Tendon Material Properties Compared to Females in a Rodent Model

The Achilles tendon is the most commonly ruptured tendon in the human body. Numerous studies have reported incidence of these injuries to be upwards of five times as common in men than women. Therefore, the objective of this study was to investigate the sex- and hormone-specific differences between Achilles tendon and muscle between female, ovariectomized female (ovarian hormone deficient), and male rats. Uninjured tissues were collected from all groups for mechanical, structural, and histological analysis. Our results showed that while cross-sectional area and failure load were increased in male tendons, female tendons exhibited superior tendon material properties and decreased muscle fiber size. Specifically, linear and dynamic moduli were increased while viscoelastic properties (e.g., hysteresis, percent relaxation) were decreased in female tendons, suggesting greater resistance to deformation under load and more efficient energy transfer, respectively. No differences were identified in tendon organization, cell shape, cellularity, or proteoglycan content. Additionally, no differences in muscle fiber type distribution were observed between groups. In conclusion, inferior tendon mechanical properties and increased muscle fiber size may explain the increased susceptibility for Achilles tendon injury observed clinically in men compared to women.

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.

The Role of Detraining in Tendon Mechanobiology

Introduction: Several conditions such as training, aging, estrogen deficiency and drugs could affect the biological and anatomo-physiological characteristics of the tendon. Additionally, recent preclinical and clinical studies examined the effect of detraining on tendon, showing alterations in its structure and morphology and in tenocyte mechanobiology. However, few data evaluated the importance that cessation of training might have on tendon. Basically, we do not fully understand how tendons react to a phase of training followed by sudden detraining. Therefore, within this review, we summarize the studies where tendon detraining was examined.

Materials and Methods: A descriptive systematic literature review was carried out by searching three databases (PubMed, Scopus and Web of Knowledge) on tendon detraining. Original articles in English from 2000 to 2015 were included. In addition, the search was extended to the reference lists of the selected articles. A public reference manager (www.mendeley.com) was adopted to remove duplicate articles.

Results: An initial literature search yielded 134 references (www.pubmed.org: 53; www.scopus.com: 11; www.webofknowledge.com: 70). Fifteen publications were extracted based on the title for further analysis by two independent reviewers. Abstracts and complete articles were after that reviewed to evaluate if they met inclusion criteria.

Conclusions: The revised literature comprised four clinical studies and an in vitro and three in vivo reports. Overall, the results showed that tendon structure and properties after detraining are compromised, with an alteration in the tissue structural organization and mechanical properties. Clinical studies usually showed a lesser extent of tendon alterations, probably because preclinical studies permit an in-depth evaluation of tendon modifications, which is hard to perform in human subjects. In conclusion, after a period of sudden detraining (e.g., after an injury), physical activity should be taken with caution, following a targeted rehabilitation program. However, further research should be performed to fully understand the effect of sudden detraining on tendons.

Sex Hormones and Tendon

The risk of overuse and traumatic tendon and ligament injuries differ between women and men. Part of this gender difference in injury risk is probably explained by sex hormonal differences which are specifically distinct during the sexual maturation in the teenage years and during young adulthood. The effects of the separate sex hormones are not fully elucidated. However, in women, the presence of estrogen in contrast to very low estrogen levels may be beneficial during regular loading of the tissue or during recovering after an injury, as estrogen can enhance tendon collagen synthesis rate. Yet, in active young female athletes, physiological high concentration of estrogen may enhance the risk of injuries due to reduced fibrillar crosslinking and enhanced joint laxity. In men, testosterone can enhance tendon stiffness due to an enhanced tendon collagen turnover and collagen content, but testosterone has also been linked to a reduced responsiveness to relaxin. The present chapter will focus on sex difference in tendon injury risk, tendon morphology and tendon collagen turnover, but also on the specific effects of estrogen and androgens.

Platelet Rich Plasma Therapy in Non-insertional Achilles Tendinopathy: The Efficacy is Reduced in 60-years Old People Compared to Young and Middle-Age Individuals

Background: Platelet Rich Plasma (PRP) has shown positive and long-lasting effects in patients with tendinopathies. However, information about age-related differences in the clinical outcome is limited. Aim of this retrospective study was to compare the efficacy of PRP therapy in young and elderly subjects suffering for Achilles tendinopathy.

Materials and method: Patients with recalcitrant non-insertional Achilles tendinopathy were enrolled. Clinical (VISA-A) and instrumental (ultrasonography) data were collected at baseline and after 1, 3, 6, and 12 months. PRP injections (once a week for 3 weeks) were performed in sterile conditions and under ultrasound (US) control.

Results: Forty-four subjects (29 young: mean age 39.5 ± 6.9; 15 elderly: mean age 61.5 ± 5.3) were retrospectively evaluated. At baseline, no significant differences were observed in the clinical and US parameters. Throughout the whole length of the study, a significant increase of VISA-A score was seen in both groups (from 50.3 ± 8.8 to 76.1 ± 6.6 in the young group, and from 48.7 ± 7.6 to 61.1 ± 9.4 in the elderly group); however, the infra-groups comparison showed better results in young patients, compared to the aged counterpart.

Conclusion: Our results show that PRP is less effective in aged people. This finding can be ascribed to several biochemical and biomechanical differences documented in tendons of young and elderly subjects (reduced number and functionality of tenocytes and tenoblasts), which becomes more evident in the long-term tissue healing. However, prospective trials, using different PRP preparations and enrolling a larger number of subjects, are needed to draw more sound and definitive conclusions.

Effects of low-intensity non-coherent light therapy on the inflammatory process in the calcaneal tendon of ovariectomized rats

The aim of this experimental study was to investigate the effects of low-intensity light-emitting diode (LED) phototherapy on the inflammatory process in the calcaneal tendon of ovariectomized rats (OVX) through the involvement of the inflammatory mediators interleukin (IL)-6, IL-10, and tumor necrosis factor-alpha (TNF-α). Thirty-five female Wistar rats were divided into 4 groups: 3 groups of OVX rats totaling 30 rats (untreated OVX rats [OVX injury group], treated OVX rats [OVX LED group], and control OVX rats; subgroups existed based on the sampling times, which were 3, 7, and 14 days) and 1 group of non-OVX rats (not OVX; n = 5). Tendon injury was induced by trauma using a 208-g mass placed at 20 cm from the right tendon of each animal with energy of 0.70 J. The animals were treated 12 h after tendonitis with LED therapy and every 48 h thereafter until euthanasia (at 3, 7, or 14 days). The tendons were dissected and stored in liquid nitrogen at -196 °C, thawed only at the time of immunoenzymatic testing (ELISA). Groups treated with LED showed a decrease in the number of pro-inflammatory cells, IL-6, and TNF-α (p <0.05), and an increase in IL-10 (p < 0.05) when compared to the not OVX group (p < 0.05). It was concluded that low-intensity LED treatment using the parameters and wavelength of 945 nm in the time periods studied reduced the release of IL-6 and TNF-α and increased the release of IL-10, thereby improving the inflammatory response in OVX rats.

Effect of Bone Mineral Density on Rotator Cuff Tear: An Osteoporotic Rabbit Model

Introduction

An increased bone mineral density (BMD) in the proximity to tendon insertion can improve rotator cuff repair and healing. However, how a decrease of BMD in the humeral head affects the biomechanical properties of the rotator cuff tendon is still unclear. Previous studies have demonstrated ovariectomy in animals to lead to osteoporosis and decreased BMD, and Teriparatide (PTH) administration to improve BMD and strength of bone. This study aimed to explore the correlation between humeral head BMD and infraspinatus (ISP) tendon insertion strength, and if an increase in bone quantity of the humeral head can improve the strength of the rotator cuff.

Materials and Methods

Eighteen New England white rabbits were divided into the 3 groups: Control, Ovariectomy-Saline (OVX-Saline), and Ovariectomy-PTH (OVX-PTH). The OVX-Saline group and the OVX-PTH were administered daily saline and Teriparatide injections for 8 weeks starting at 17 weeks of OVX. BMD of the humeral head was measured, the ISP tendon failure load was tested and the failure stress was calculated. One specimen from each group was used for histological analysis. Linear regression analysis was used to derive equations for the BMD and failure stress.

Results

Significant differences were observed in the measured humeral head BMD of the Control and OVX-PTH groups compared to the OVX-Saline group (P = 0.0004 and P = 0.0024, respectively). No significant difference was found in failure stress among the three groups, but an expected trend with the control group and OVX-PTH group presenting higher failure strength compared to the OVX-Saline group. BMD at the humeral head showed a positive linear correlation with stress (r² = 0.54). Histology results showed the superiority in OVX-PTH group ISP enthesis compared to the OVX-Saline group.

Conclusion

Bone loss of the humeral head leads to decreased tendon/bone insertion strength of the infraspinatus tendon enthesis. Teriparatide administration can increase bone density of the humeral head and may improve the mechanical properties of the infraspinatus tendon enthesis.

Moderate Exercise Mitigates the Detrimental Effects of Aging on Tendon Stem Cells

Aging is known to cause tendon degeneration whereas moderate exercise imparts beneficial effects on tendons. Since stem cells play a vital role in maintaining tissue integrity, in this study we aimed to define the effects of aging and moderate exercise on tendon stem/progenitor cells (TSCs) using in vitro and in vivo models. TSCs derived from aging mice (9 and 24 months) proliferated significantly slower than TSCs obtained from young mice (2.5 and 5 months). In addition, expression of the stem cell markers Oct-4, nucleostemin (NS), Sca-1 and SSEA-1 in TSCs decreased in an age-dependent manner. Interestingly, moderate mechanical stretching (4%) of aging TSCs in vitro significantly increased the expression of the stem cell marker, NS, but 8% stretching decreased NS expression. Similarly, 4% mechanical stretching increased the expression of Nanog, another stem cell marker, and the tenocyte-related genes, collagen I and tenomodulin. However, 8% stretching increased expression of the non-tenocyte-related genes, LPL, Sox-9 and Runx-2, while 4% stretching had minimal effects on the expression of these genes. In the in vivo study, moderate treadmill running (MTR) of aging mice (9 months) resulted in the increased proliferation rate of aging TSCs in culture, decreased lipid deposition, proteoglycan accumulation and calcification, and increased the expression of NS in the patellar tendons. These findings indicate that while aging impairs the proliferative ability of TSCs and reduces their stemness, moderate exercise can mitigate the deleterious effects of aging on TSCs and therefore may be responsible for decreased aging-induced tendon degeneration.