Quantitative and Qualitative Change of Collagen of Achilles Tendons in Rats With Systemic Administration of Glucocorticoids

Fabrication of atelocollagen-coated bioabsorbable suture and the evaluation of its regenerative efficacy in Achilles tendon healing using a rat experimental model

Recently, the incidence of Achilles tendon ruptures (ATRs) has become more common, and repair surgery using a bioabsorbable suture is generally preferred, particularly in the case of healthy patients. Sutures composed of poly(lactic-co-glycolic acid) (PLGA) are commonly used in ATR surgeries. Nevertheless, owing to the inherent limitations of PLGA, novel bioabsorbable sutures that can accelerate Achilles tendon healing are sought. Recently, several studies have demonstrated the beneficial effects of atelocollagen on tendon healing. In this study, poly(3,4-dihydroxy-L-phenylalanine) (pDOPA), a hydrophilic biomimetic material, was used to modify the hydrophobic surface of a PLGA suture (Vicryl, VC) for the stable coating of atelocollagen on its surface. The main objective was to fabricate an atelocollagen-coated VC suture and evaluate its performance in the healing of Achilles tendon using a rat model of open repair for ATR. Structural analyses of the surface-modified suture indicated that the collagen was successfully coated on the VC/pDOPA suture. Postoperative in vivo biomechanical analysis, histological evaluation, ultrastructural/morphological analyses, and western blotting confirmed that the tendons in the VC/pDOPA/Col group exhibit superior healing than those in the VC and VC/pDOPA groups after 1 and 6 weeks following the surgery. The this study suggests that atelocollagen-coated PLGA/pDOPA sutures are preferable for future medical applications, especially in the repair of ATR.

An Atelocollagen Injection Enhances the Healing of Nonoperatively Treated Achilles Tendon Tears: An Experimental Study in Rats

Background

There is growing interest in nonoperative treatment for the management of Achilles tendon ruptures (ATRs). However, nonoperative treatment is limited by the risk of tendon reruptures and low satisfaction rates. Recently, atelocollagen injections have been reported to have beneficial effects on tendon healing.

Purpose

To evaluate the beneficial effects of injected atelocollagen on Achilles tendon healing and investigate the mechanism of atelocollagen on tendon healing.

Study Design

Controlled laboratory study.

Methods

Percutaneous tenotomy of the right Achilles tendon in 66 rats was performed. The animals were equally divided into the noninjection group (NG) and the collagen injection group (CG). At 1, 3, and 6 weeks, the Achilles functional index, cross-sectional area, load to failure, stiffness, stress, and the modified Bonar score were assessed. Transmission electron microscopy, western blotting, and immunohistochemistry were also performed.

Results

The Achilles functional index (-6.8 vs -43.0, respectively; P = .040), load to failure (42.1 vs 27.0 N, respectively; P = .049), and stiffness (18.8 vs 10.3 N/mm, respectively; P = .049) were higher in the CG than those in the NG at 3 weeks. There were no significant differences in histological scores between the 2 groups. Transmission electron microscopy analysis showed that the mean diameter of collagen fibrils in the CG was greater than that in the NG at 3 weeks (117.2 vs 72.6 nm, respectively; P < .001) and 6 weeks (202.1 vs 144.0 nm, respectively; P < .001). Western blot analysis showed that the expression of collagen type I in the CG was higher than that in the NG at 1 week (P = .005) and 6 weeks (P = .001).

Conclusion

An atelocollagen injection had beneficial effects on the healing of nonoperatively treated Achilles tendon injuries. The Achilles tendon of CG rats exhibited better functional, biomechanical, and morphological outcomes compared with NG rats. The molecular data indicated that the mechanism of atelocollagen injections may be associated with an increased amount of collagen type I.

Clinical Relevance

An atelocollagen injection might be a good adjuvant option for the nonoperative treatment of ATRs.

Diabetes and treatment with orally administrated corticosteroids negatively affect treatment outcome at follow-up after acute Achilles tendon rupture

PURPOSE

Studies investigating the influence of comorbidities on patient-reported outcomes after acute Achilles tendon ruptures (ATR) are lacking. In this study, the aim was to investigate the effect of comorbidity and medical treatment on the patient-reported outcome measure Achilles tendon total rupture score (ATRS).

METHODS

The study was performed as a registry study from the Danish Achilles tendon Database (DADB). In the DADB, ATRS was registered at baseline (prior to rupture), at 3-6 month, 1-year and 2-year follow-ups. The outcomes were ATRS at follow-up and the change in ATRS from baseline to follow-up. Variables of interest were diabetes, hypertension, rheumatic disease and treatment with orally administrated corticosteroids. Linear mixed-effects models including all follow-up time points in the same model were used adjusting for sex, age group, treatment (operative or non-operative) and the investigated comorbidities.

RESULTS

Data were collected from 2012 to 2019. Two thousand and four patients with ATR were included. Patients with the investigated comorbidities and treatment with orally administrated corticosteroid scored 10.6-19.1 points lower in mean ATRS at baseline (prior to rupture) compared to patients without the respective disease or treatment. At follow-up, patients with diabetes (mean difference, [95% CI]) (- 6.2, [- 11.7; - 0.8]; P = 0.03) and patients in treatment with orally administrated corticosteroids (- 10.9, [- 16.2; - 5.7]; P < 0.01) had a statistically significantly worse ATRS than patients without the respective disease. However, change in ATRS from baseline to follow-up was not affected. Hypertension and rheumatic disease did not affect ATRS at follow-up but had a positive effect on change in ATRS (4.3, [0.5; 8.1]; P = 0.03) and (12.0, [5.0; 19.9]; P < 0.01), respectively. No other statistically significant differences were found.

CONCLUSION

This study showed that patients with diabetes, hypertension, rheumatic disease and patients in treatment with orally administrated corticosteroids had a lower ATRS at baseline (prior to the rupture) when compared to patients without the respective disease or treatment. Diabetes and treatment with orally administrated corticosteroids did negatively affect ATRS at follow-up, but none of the investigated comorbidities or treatment with orally administrated corticosteroids did negatively affect change in ATRS from baseline to follow-up.

LEVEL OF EVIDENCE

Level III.

Taping, Bracing, and Injection Treatment for Patellofemoral Pain and Patellar Tendinopathy

PURPOSE OF REVIEW

This article will focus on additional treatment options for the two most common causes of anterior knee pain, patellofemoral pain syndrome, and patellar tendinopathy. Conservative management is the first-line treatment for these conditions. For clinicians to maximize the efficacy of conservative treatment options for their patients, they must understand the most up-to-date literature evaluating the potential benefit of taping, bracing, and injections as adjunctive treatments for maximizing treatment success.

RECENT FINDINGS

Recent studies of bracing and taping have found them to be helpful for patients in the short-term management of pain and improving function. However, less is known about their exact mechanism but studies are encouraging that they have a subtle role in changing patellofemoral biomechanics. Injections remain a commonly used treatment for musculoskeletal conditions; however, the evidence for their use in patellofemoral pain and patellar tendinopathy is limited. The use of platelet-rich plasma (PRP), sclerosing, high volume, or stem cell injections is an exciting new area in the treatment of patellar tendinopathy. However, evidence at this time to recommend these treatments is lacking, and more well-designed studies are needed. The treatment of patellofemoral pain and patellar tendinopathy consists of a multi-faceted approach of physiotherapy and physical modalities. There is evidence for short-term use of taping and bracing for these conditions. The evidence for injections at this time is limited and remains under investigation. Future well-designed randomized controlled studies will provide insight into the efficacy of several different types of injections in the treatment of patellar tendinopathy. Physicians should feel comfortable integrating taping and bracing into their anterior knee pain treatment paradigm while making cautious use of invasive injections as adjunctive therapy.

Parasitological and immunological aspects of oral and subcutaneous prednisolone treatment in rats experimentally infected with Strongyloides venezuelensis

Strongyloides venezuelensis is a model to study human strongyloidiasis, which infects wild rodents and shares common antigenic epitopes with Strongyloides stercoralis. This study aimed to evaluate parasitological and immunological parameters of prednisolone immunosuppression protocols in rats (Rattus novergicus) infected with S. venezuelensis. Rats were divided into six groups (n = 36): untreated and uninfected (-) or infected (+); oral treatment and uninfected (o-) or infected (o+); subcutaneous treatment and uninfected (sc-) or infected (sc+). For oral immunosuppression, 5 mg/mL of water diluted prednisolone were given five days before infection, and in the days 8 and 21 (for 5 days). For subcutaneous immunosuppression, 10 mg/kg of prednisolone were given daily. The infection was established by the subcutaneous injection of approximately 3,000 S. venezuelensis filarioid larvae per animal. All animals from the (+) and (o+) groups survived, while four rats from the (sc+) died prior to necropsy date. Parasitological analysis showed higher egg elimination in (o+) in comparison to (+) and (sc+) on 7, 13 and 26 days post infection (d.p.i.).The recovery of parasitic females at day 30 was significantly higher in (o+), compared to (+). The (+) and (o+) groups showed a clear increase in anti-S. venezuelensis IgG, IgG1 and IgG2 from 13th d.p.i. Oral immunosuppression led to a higher number of adult females and increased egg output while maintaining IgG and subclasses antibody levels comparable to the positive control.

Optical Microscopy and Electron Microscopy for the Morphological Evaluation of Tendons: A Mini Review

The morphological characteristics of tendons have been thoroughly evaluated via microscopy. Optical microscopy and electron microscopy are the most commonly used techniques for tendon tissue observation. According to the principles of both microscopy types, preparation and evaluation methods vary. Simple optical microscopy is commonly used in the observation of cells and extracellular matrix, and many stains, including hematoxylin–eosin, Van Gieson, Prussian blue, Alcian blue, and toluidine blue, are used for evaluating cells, collagen fiber arrangement, and noncollagenous proteins. Histological scoring systems have been used in many studies for semi‐quantification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are the most commonly used electron microscopy types, and special consideration is needed for the fixation and embedding protocols. Glutaraldehyde followed by osmium is most commonly used in the chemical fixation of tendon tissue, followed by epoxy resin embedment. Longitudinal sections captured in SEM images show the arrangement of collagen fibrils and the cells and lipid drops among them, while cross sections captured in TEM images show the diameter and distribution of collagen fibrils. SEM and TEM are used together for comprehensive evaluations. This mini review is focused on the preparation methodology and related evaluation indexes for the morphological evaluation of tendons.

Downregulation of type I collagen expression in the Achilles tendon by dexamethasone: a controlled laboratory study

Background

Spontaneous Achilles tendon rupture associated with long-term dexamethasone (Dex) use has been reported. However, few studies have investigated the potential mechanism. The aim of this study was to evaluate the effects of oral Dex on type I collagen in humans and rats and its association with tendon rupture.

Methods

First, six Achilles tendons from patients who received long-term Dex treatment, and another six normal tendons were harvested for histological evaluation. Secondly, 8-week-old rats (n = 72) were randomly assigned to a Dex group or a control group. Type I collagen was studied at the mechanical, histological, and molecular levels after 3 and 5 weeks. Tenocytes isolated from normal human and rat tendon were used to investigate the effect of Dex on cellular scale.

Results

Histological analysis of human and rat tendon tissue revealed an irregular, disordered arrangement of type I collagen in the Dex group compared with the control group. In addition, In the Dex+ group, type I collagen expression decreased in comparison with the Dex− group in both human and rat tenocytes. The mechanical strength of tendons was significantly reduced in the Dex group (68.87 ± 11.07 N) in comparison with the control group (81.46 ± 7.62 N, P = 0.013) after 5 weeks. Tendons in the Dex group were shorter with smaller cross-sectional areas (10.71 ± 0.34 mm², 1.44 ± 0.22 mm², respectively) after 5 weeks than those in the control group (11.13 ± 0.50 mm², P = 0.050, 2.74 ± 0.34 mm², P < 0.001, respectively).

Conclusions

This finding suggests long-term use of Dex that decreases the expression of type I collagen at molecular and tissue levels both in human and rat Achilles tendons. Furthermore, Dex decreases the mechanical strength of the tendon, thereby increasing the risk of Achilles tendon rupture.

Does glucocorticoid exposure explain the association between metabolic dysfunction and tendinopathy?

BACKGROUND

While metabolic health is acknowledged to affect connective tissue structure and function, the mechanisms are unclear. Glucocorticoids are present in almost every cell type throughout the body and control key physiological processes such as energy homeostasis, stress response, inflammatory and immune processes, and cardiovascular function. Glucocorticoid excess manifests as visceral adiposity, dyslipidaemia, insulin resistance, and type 2 diabetes. As these metabolic states are also associated with tendinopathy and tendon rupture, it may be that glucocorticoids excess is the link between metabolic health and tendinopathy.

OBJECTIVE

To synthesise current knowledge linking glucocorticoids exposure to tendon structure and function.

METHODS

Narrative literature review.

RESULTS

We provide an overview of endogenous glucocorticoid production, regulation, and signalling. Next we review the impact that oral glucocorticoid has on risk of tendon rupture and the effect that injected glucocorticoid has on resolution of symptoms. Then we highlight the clinical and mechanistic overlap between tendinopathy and glucocorticoid excess in the areas of visceral adiposity, dyslipidaemia, insulin resistance and type 2 diabetes. In these areas, we highlight the role of glucocorticoids and how these hormones might underpin the connection between metabolic health and tendon dysfunction.

CONCLUSIONS

There are several plausible pathways through which glucocorticoids might mediate the connection between metabolic health and tendinopathy.

Morphological changes during the formation of amoebic liver abscess in vagotomized hamsters

Amoebic liver abscess (ALA) is the main extra-intestinal complication caused by Entamoeba histolytica. Given the histological features of ALA in hamsters and the importance of the vagus nerve in the immune response, the aim of this study was to identify and analyze the major changes in ALA that are caused by a vagotomy. The changes found are related to inflammatory foci and abscess size, the type of collagen formed, and the number of trophozoites in lesions. Male hamsters were divided into three groups: Intact animals (IA) and those undergoing a false operation (SHAM) or a subdiaphragmatic vagotomy (VAG). In each group, E. histolytica trophozoites or culture medium (CM) were inoculated in hamsters by the intrahepatic route, and then euthanized at 6h, 12h, 24h, 48h, 4d or 7d post-infection. Initially the growth of the abscess was more rapid in the VAG group, but at day 7 it was faster in the IA and SHAM groups. VAG animals showed a higher quantity of type III collagen than the IA and SHAM groups. A larger number of amoebic trophozoites/mm² was observed up to day 4 in VAG hamsters (23.3±2.19) compared to IA (14.6±0.23) and SHAM (6.13±0.87) animals. This parameter decreased by day 7 in VAG (13.4±0.87) with respect to IA (24.7±1.47) and SHAM (21.7±1.48). The results show that a subdiaphragmatic vagotomy influenced the development of ALA in hamsters, suggesting a modification of the morphological structure of damaged hepatic tissue.

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.

Cross platform analysis of transcriptomic data identifies ageing has distinct and opposite effects on tendon in males and females

The development of tendinopathy is influenced by a variety of factors including age, gender, sex hormones and diabetes status. Cross platform comparative analysis of transcriptomic data elucidated the connections between these entities in the context of ageing. Tissue-engineered tendons differentiated from bone marrow derived mesenchymal stem cells from young (20-24 years) and old (54-70 years) donors were assayed using ribonucleic acid sequencing (RNA-seq). Extension of the experiment to microarray and RNA-seq data from tendon identified gender specific gene expression changes highlighting disparity with existing literature and published pathways. Separation of RNA-seq data by sex revealed underlying negative binomial distributions which increased statistical power. Sex specific de novo transcriptome assemblies generated fewer larger transcripts that contained miRNAs, lincRNAs and snoRNAs. The results identify that in old males decreased expression of CRABP2 leads to cell proliferation, whereas in old females it leads to cellular senescence. In conjunction with existing literature the results explain gender disparity in the development and types of degenerative diseases as well as highlighting a wide range of considerations for the analysis of transcriptomic data. Wider implications are that degenerative diseases may need to be treated differently in males and females because alternative mechanisms may be involved.