Tendon Fibrosis Research Articles

Resveratrol ameliorates pathological fibrosis of the myodural bridge by regulating the SIRT3/TGF-β1/Smad pathway

PurposePathological fibrosis of the myodural bridge (MDB) affects cerebrospinal fluid circulation. However, no optimal drug treatments are available. We aimed to explore the antifibrotic effect of resveratrol on bleomycin-induced pathological fibrosis of the MDB and its underlying mechanisms. MethodsGenes common to the potential targets of resveratrol were determined using network pharmacology, genes related to muscle and tendon fibrosis were acquired from the GeneCards database, and genes related to MDB development were determined using Venny. These genes were considered potential resveratrol treatment targets in bleomycin-induced pathological fibrosis of the MDB and were annotated using bioinformatics methods. We validated the intersected genes using quantitative real-time polymerase chain reaction (qRT-PCR) and performed molecular docking analysis to calculate the binding activity between the target gene and resveratrol. Hematoxylin and eosin and Masson staining were used to detect the morphological changes in bleomycin-induced fibrosis of the MDB following resveratrol treatment. We used qRT-PCR and immunohistochemistry to evaluate the expression of the sirtuin 3 (SIRT3)/transforming growth factor-β1 (TGF-β1)/Smad pathway and the profibrotic markers α-smooth muscle actin (α-SMA) and Collagen Ⅰ. ResultsThrough network pharmacology and bioinformatics analyses, we identified four core intersected genes, and SIRT3 expression was validated using qRT-PCR. Molecular docking analysis revealed that resveratrol had good binding affinity for SIRT3. Resveratrol ameliorated morphological abnormalities in bleomycin-induced pathological fibrosis of the MDB by inhibiting fibroblast activation and excessive collagen fiber deposition. Resveratrol exerted its antifibrotic effect by regulating the SIRT3/TGF-β1/Smad pathway. ConclusionResveratrol has an antifibrotic effect in bleomycin-induced pathological fibrosis of the MDB in vivo and may be considered a novel therapeutic strategy.

Understanding Tendon Fibroblast Biology and Heterogeneity.

Tendon regeneration has emerged as an area of interest due to the challenging healing process of avascular tendon tissue. During tendon healing after injury, the formation of a fibrous scar can limit tendon strength and lead to subsequent complications. The specific biological mechanisms that cause fibrosis across different cellular subtypes within the tendon and across different tendons in the body continue to remain unknown. Herein, we review the current understanding of tendon healing, fibrosis mechanisms, and future directions for treatments. We summarize recent research on the role of fibroblasts throughout tendon healing and describe the functional and cellular heterogeneity of fibroblasts and tendons. The review notes gaps in tendon fibrosis research, with a focus on characterizing distinct fibroblast subpopulations in the tendon. We highlight new techniques in the field that can be used to enhance our understanding of complex tendon pathologies such as fibrosis. Finally, we explore bioengineering tools for tendon regeneration and discuss future areas for innovation. Exploring the heterogeneity of tendon fibroblasts on the cellular level can inform therapeutic strategies for addressing tendon fibrosis and ultimately reduce its clinical burden.

Reduction of Tendon Fibrosis Using Galectin-3 Inhibitors.

Fibrosis is a complication of both tendon injuries and repairs. The authors aimed to develop a mouse model to assess tendon fibrosis and to identify an antifibrotic agent capable of overcoming it. The Achilles tendon of adult C57Bl/6 mice was exposed via skin incision, followed by 50% tendon injury and abrasion with sandpaper. Sham operations were conducted on contralateral hindlimbs. Histologic analyses and immunofluorescent staining for fibrotic markers (collagen type 1 [ Col1 ], α-smooth muscle actin [ α-SMA ]) were used to confirm that the model induced tendon fibrosis. A second experiment further examined the role of α-SMA in adhesion formation using α-SMA.mTmG mice (6 to 8 weeks old; n = 3) with the same injury model. Lastly, α-SMA.mTmG mice were randomized to either condition 1 (tendon injury [control group]) or condition 2 (tendon injury with galectin-3 inhibitor [Gal3i] treatment at time of injury [treatment group]). Histologic analyses confirmed tendon thickening and collagen deposition after tendon injury and abrasion compared with control. Immunofluorescence showed higher levels of Col1 and α-SMA protein expression after injury compared with sham ( P < 0.05). Real-time quantitative polymerase chain reaction also demonstrated increased gene expression of Col1 and α-SMA after injury compared with sham ( P < 0.05). Gal3 protein expression also increased after injury and colocalized with α-SMA+ fibroblasts surrounding the fibrotic tendon. Gal3i treatment decreased collagen deposition and scarring observed in the treatment group ( P < 0.05). The authors' study provides a reproducible and reliable model to investigate tendon fibrosis. Findings suggest the potential of Gal3i to overcome fibrosis resulting from tendon injuries. Tendon injuries are common presentations to hand surgeons. Complications include adhesion formation, which results in reduced strength and frequent reinjury. Advancements in management require a better understanding of the mechanisms behind tendon fibrosis in order to identify ways to overcome it.

Effects Of Thoracic Manipulation in Increasing Rom and Pain in Frozen Shoulder Randomized Control Study

Adhesive capsulitis is a common musculoskeletal condition that can cause discomfort and a limited range of motion (ROM) in the shoulder. Unknown is the precise pathophysiology of frozen shoulder. The tendon fibrosis and capsule contractors that limit mobility at the glenohumeral joint are often to blame. Objective: To determine the efficacy of thoracic spine manipulation on shoulder ROM, pain and disability in patients with frozen shoulder. Methods: This study was conducted in a randomized control fashion at the HHIRS Rehabilitation Department in Mansehra. Patients experiencing shoulder discomfort between the ages of 40 and 60 were included, both male and female. The analysis was carried out using SPSS version 22.0. For normality, the Shapiro-Walk test was applied. Tests both parametric and non-parametric were used to compare results within and across groups. Results: Friedman test presented comparison within group of variables via non parametric test for shoulder pain and ROMs. There is significant improving in variables on VAS scale and range of motions in both groups showed significant improvement p&lt;0.001. Both group A and B showed statistically significant improvement in disability p&lt;0.001 while in B group there was an irrelevant alteration in 3rd week. Conclusions: In comparison to traditional physical therapy alone, thoracic spine manipulation is more successful in improving shoulder discomfort, disability and ROM

TGFβ1-transfected tendon stem cells promote tendon fibrosis

BackgroundIn aged people, tendon injuries frequently occur during sporting and daily activities. In clinical practice, typical physiotherapeutic, pharmacotherapeutic, and surgical techniques do not result in the full recovery of injured tendons, which may lead to chronic degenerative disease.MethodsWe first isolated tendon stem cells (TSCs) from rats and transfected them with the TGFβ1 gene, resulting in TGFβ1-TSCs. The proliferation of TSCs was detected using the Cell Counting Kit 8, and TSCs were identified by immunofluorescence analysis and differentiation capacity analysis. Aggrecan, COL2A1, alpha smooth muscle actin (α-SMA), and p-Smad2 expression levels were detected using western blotting and quantitative reverse transcription polymerase chain reaction. Additionally, a tendon injury model was generated to explore the effect of TGFβ1 on the repair of the tendon by TSCs.ResultsCompared with fibrinogen treatment, TSC + fibrinogen or TGFβ1-TSC + fibrinogen treatment significantly promoted the fibrosis of injured tendons, as evidenced by histological analyses, with TGFβ1-TSC + fibrinogen having a greater effect than TSC + fibrinogen. In TGFβ1-TSCs, increased expression levels of aggrecan and COL2A1 indicated that TGFβ1 signaling induced chondrogenic differentiation. Meanwhile, the increased collagen and α-SMA protein levels indicated that TGFβ1 promoted fibrogenesis. Additionally, TGFβ1 stimulated the production of phosphorylated Smad2 in TSCs, which suggested that the chondrogenic and fibrogenic differentiation of TSCs, as well as tissue regeneration, may be associated with the TGFβ1/Smad2 pathway.ConclusionTGFβ1-TSC therapy may be a candidate for effective tendon fibrosis.

48. Reduction of Tendon Fibrosis Using Galectin-3 Inhibitors

Purpose: Healing after tendon injuries results in formation of a fibrotic scar, resulting in reduced tendon strength and frequent reinjury. Galectins have shown to be involved in the inflammation and fibrosis of muscle and tendon injuries. Understanding the role of galectins in tendon fibrosis is limited due to the lack of reproducible murine models that evaluate tendon fibrosis. Our study demonstrates a novel Achilles tendon model that can assess tendon fibrosis. We further identify an antifibrotic agent capable of overcoming tendon fibrosis. Methods: Adult C57Bl/6 mice (6–8-week-old) (n = 6) underwent a 1cm skin incision to expose the Achilles tendon. The Achilles tendon then underwent a 50% rupture followed by abrasion of the ruptured tendon with sandpaper. At 14 days post injury tendons were evaluated by histology to confirm tendon fibrosis. Following the confirmation that the murine model can reliably induce tendon fibrosis, adult C57Bl/6 mice (6–8-week-old) (n = 6) were randomized to three conditions. Tendon injury (Control group), 2. Tendon injury with simultaneous treatment with a galectin-3 inhibitor (Treatment group), and 3. Skin incision with no tendon injury (Sham group). At post-operative day 14 (POD14), tendons were analyzed for histological and flow cytometry analysis (FACS). Tendon sections underwent immunofluorescent staining for fibrosis (e.g., collagen type I/col-I, collagen type 3/col-3, and alpha smooth muscle actin/a-SMA), vascularization (CD31 staining), inflammation (F4/80 antigen), and were imaged on a confocal microscope. Results: Histological analysis by H&E and picrosirius red staining confirmed tendon thickening and collagen deposition in the control group compared to the sham group (*p<0.05), validating the reproducibility of the murine model to induce tendon fibrosis. Immunohistochemistry further confirmed greater levels of col-I, col-III, and α-SMA protein expression in the control group compared to the sham group (P <0.05). RT-qPCR further confirmed greater gene expression of col- I, col-III, and α-SMA in the control compared to the sham group (*p<0.05). Fibroblasts surrounding the fibrotic tendon illustrated high levels of Galectin-1, 2, and 3 protein expression by immunohistochemistry, with galectin-3 being significantly greater in the Control group compared to the Sham group (*p<0.05). Galectin-3 inhibitor treatment decreased the collagen deposition and scarring observed in the Control group (*p<0.05). The Treatment group also demonstrated reduced tendon fibrosis with decreased col- I, col-III, and a-SMA gene and protein expression compared to the Control group (*p<0.05). Flow cytometry analysis further showed reduced numbers of profibrotic fibroblasts (CD26+) in the Treatment compared to the Control group (*p<0.05). Mice receiving the Galectin-3 inhibitor also demonstrated improved vascularization as shown by CD31 staining and a decreased inflammatory infiltrate evidenced by F4/80 macrophage staining (*p<0.05) following tendon injury. Conclusion: Our study provides a novel tendon fibrosis model that is reproducible and cost effective. Targeting galectins using Galectin-3 inhibitors may be an effective method to reduce the tendon fibrosis following injury.

Roles of Oxidative Stress in Acute Tendon Injury and Degenerative Tendinopathy-A Target for Intervention.

Both acute and chronic tendon injuries are disabling sports medicine problems with no effective treatment at present. Sustained oxidative stress has been suggested as the major factor contributing to fibrosis and adhesion after acute tendon injury as well as pathological changes of degenerative tendinopathy. Numerous in vitro and in vivo studies have shown that the inhibition of oxidative stress can promote the tenogenic differentiation of tendon stem/progenitor cells, reduce tissue fibrosis and augment tendon repair. This review aims to systematically review the literature and summarize the clinical and pre-clinical evidence about the potential relationship of oxidative stress and tendon disorders. The literature in PubMed was searched using appropriate keywords. A total of 81 original pre-clinical and clinical articles directly related to the effects of oxidative stress and the activators or inhibitors of oxidative stress on the tendon were reviewed and included in this review article. The potential sources and mechanisms of oxidative stress in these debilitating tendon disorders is summarized. The anti-oxidative therapies that have been examined in the clinical and pre-clinical settings to reduce tendon fibrosis and adhesion or promote healing in tendinopathy are reviewed. The future research direction is also discussed.

Is Elevated Hba1c Level Associated with Achilles Tendon Contracture Development in Diabetic Foot Patients?

Introduction:Chronic hyperglycemia can increase extracellular matrix (ECM) accumulation that leads to tendon fibrosis and subsequent contracture. Considering the reversibility of fibrosis, it is important to identify factors that are associated with it. The purpose of this study was to determine whether elevated HbA1c levels are associated with the development of Achilles tendon contracture in diabetes mellitus patients.Materials and methods:We reviewed 206 patients with diabetic foot problems between January 2015-December 2019. Demographic data, the presence of Achilles tendon contracture, and laboratory results were documented and statistically analysed between patients with contracture and without contracture.Results:Patients’ mean age was 58.46 ± 6.67 years old. Contracture was found in 84 out of 206 patients (40.78%) patients, with female predominance (45/84 patients; 53%). While contracture was found significantly associated with sex difference (0.035) and age groups (p=0.006), there was no meaningful association with HbA1c level groups (p=0.324).Conclusion:Findings do not support the use of HbA1c level as a sole determinant of Achilles tendon contracture. Seemingly, there are other confounding factors affecting the Achilles tendon contracture development in diabetes mellitus patients. It should be emphasised that albeit the association between chronic hyperglycemia and contracture development, the low HbA1c should not be overlooked as having no risk of Achilles tendon contracture and vice versa.

The Functions and Mechanisms of Low-Level Laser Therapy in Tendon Repair (Review).

Tendon injury is a common disease of the musculoskeletal system, accounting for roughly 30%–40% of sports system disorder injuries. In recent years, its incidence is increasing. Many studies have shown that low-level laser therapy (LLLT) has a significant effect on tendon repair by firstly activating cytochrome C oxidase and thus carrying out the photon absorption process, secondly acting in all the three phases of tendon repair, and finally improving tendon recovery. The repair mechanisms of LLLT are different in the three phases of tendon repair. In the inflammatory phase, LLLT mainly activates a large number of VEGF and promotes angiogenesis under hypoxia. During the proliferation phase, LLLT increases the amount of collagen type III by promoting the proliferation of fibroblasts. Throughout the remodeling phase, LLLT mainly activates M2 macrophages and downregulates inflammatory factors, thus reducing inflammatory responses. However, it should also be noted that in the final phase of tendon repair, the use of LLLT causes excessive upregulation of some growth factors, which will lead to tendon fibrosis. In summary, we need to further investigate the functions and mechanisms of LLLT in the treatment of tendon injury and to clarify the nature of LLLT for the treatment of diverse tendon injury diseases.

Role of High Resolution Ultrasound and Magnetic Resonance Imaging in Traumatic Soft Tissue Injuries of the Wrist and Hand

Abstract Aim of the Work To assess the role of ultrasound in the diagnosis of traumatic soft tissue injuries of hand and wrist. Patients and Method This study includes 30 patients with a mean age of 42.17 years ±9, all with history of traumatic soft tissue injuries in hand and wrist, all patients underwent ultrasound and MRI. The U/S&amp;MRI diagnostic criteria of each patient were analyzed, compared and correlated with clinical diagnosis/ or operative findings . Results A comparison of the sensitivity of US versus MRI was done by correlating the final diagnosis of each modality with clinical diagnosis and/or operative findings. In general as regard all types of soft tissue injuries we found that, in correlation with clinical diagnosis US gives (93.3% sensitivity), while MRI gives (73.3% sensitivity). US &amp; MRI result shows agreement in detection of all types of post traumatic soft tissue injuries except in chronic tendinopathy, tendon fibrosis ,and chronic tendon tear heals by fibrosis we found no agreement between them (in which ultrasound can diagnose them, while MRI couldn’t detect them). Conclusion Ultrasound shows higher sensitivity in diagnosis of soft tissue injuries of hand and wrist than MRI, as compared to operative findings and /or clinical data.

Key indicators of repetitive overuse-induced neuromuscular inflammation and fibrosis are prevented by manual therapy in a rat model

BackgroundWe examined the effectiveness of a manual therapy consisting of forearm skin rolling, muscle mobilization, and upper extremity traction as a preventive treatment for rats performing an intensive lever-pulling task. We hypothesized that this treatment would reduce task-induced neuromuscular and tendon inflammation, fibrosis, and sensorimotor declines.MethodsSprague-Dawley rats performed a reaching and lever pulling task for a food reward, 2 h/day, 3 days/week, for 12 weeks, while simultaneously receiving the manual therapy treatment 3 times per week for 12 weeks to either the task-involved upper extremities (TASK-Tx), or the lower extremities as an active control group (TASK-Ac). Results were compared to similarly treated control rats (C-Tx and C-Ac).ResultsMedian nerves and forearm flexor muscles and tendons of TASK-Ac rats showed higher numbers of inflammatory CD68+ and fibrogenic CD206+ macrophages, particularly in epineurium, endomysium and epitendons than TASK-Tx rats. CD68+ and CD206+ macrophages numbers in TASK-Tx rats were comparable to the non-task control groups. TASK-Ac rats had more extraneural fibrosis in median nerves, pro-collagen type I levels and immunoexpression in flexor digitorum muscles, and fibrogenic changes in flexor digitorum epitendons, than TASK-Tx rats (which showed comparable responses as control groups). TASK-Ac rats showed cold temperature, lower reflexive grip strength, and task avoidance, responses not seen in TASK-Tx rats (which showed comparable responses as the control groups).ConclusionsManual therapy of forelimbs involved in performing the reaching and grasping task prevented the development of inflammatory and fibrogenic changes in forearm nerves, muscle, and tendons, and sensorimotor declines.

Targeting Cell Contractile Forces: A Novel Minimally Invasive Treatment Strategy for Fibrosis.

Fibrosis is a complication of tendon injury where excessive scar tissue accumulates in and around the injured tissue, leading to painful and restricted joint motion. Unfortunately, fibrosis tends to recur after surgery, creating a need for alternative approaches to disrupt scar tissue. We posited a strategy founded on mechanobiological principles that collagen under tension generated by fibroblasts is resistant to degradation by collagenases. In this study, we tested the hypothesis that blebbistatin, a drug that inhibits cellular contractile forces, would increase the susceptibility of scar tissue to collagenase degradation. Decellularized tendon scaffolds (DTS) were treated with bacterial collagenase with or without external or cell-mediated internal tension. External tension producing strains of 2-4% significantly reduced collagen degradation compared with non-tensioned controls. Internal tension exerted by human fibroblasts seeded on DTS significantly reduced the area of the scaffolds compared to acellular controls and inhibited collagen degradation compared to free-floating DTS. Treatment of cell-seeded DTS with 50mM blebbistatin restored susceptibility to collagenase degradation, which was significantly greater than in untreated controls (p < 0.01). These findings suggest that therapies combining collagenases with drugs that reduce cell force generation should be considered in cases of tendon fibrosis that do not respond to physiotherapy.

Pathogenesis and Development of Patellar Tendon Fibrosis in a Rabbit Overuse Model

Background: The pathogenesis of patellar tendon fibrosis caused by overuse remains unclear. In an effort to further investigate effective treatments for patellar tendon fibrosis attributed to overuse, it is necessary to construct a reliable animal model. Purpose: A rabbit patellar tendon fibrosis model was developed with the use of electrical stimulation to induce jumping. The pathogenesis and development of patellar tendon fibrosis were subsequently investigated with this model. Study Design: Controlled laboratory study. Methods: A total of 32 New Zealand White rabbits were randomly divided into a jumping group and a control group. Rabbits in the control group did not receive any treatment, while those in the jumping group jumped 150 times daily, 5 days per week. At 2, 4, 6, and 8 weeks after the initiation of treatment, the patellar tendons of 4 rabbits from each group were harvested and subjected to hematoxylin and eosin staining, immunohistochemical staining, and real-time polymerase chain reaction. The influence of jumping training on the expressions of histology- and fibrosis-related factors in the patellar tendon was assessed. Results: The histological changes of patellar tendon fibrosis in the jumping group were most pronounced at 4 weeks. When compared with the control group at corresponding time points, the mRNA and protein expressions of TGF-β1, CTGF, COL-I, and COL-III were upregulated significantly in the patellar tendon after jumping training for 4 weeks (P < .05). Intragroup comparison at different time points indicated that the mRNA and protein expressions of TGF-β1, COL-I, and COL-III were the highest at 4 weeks in the jumping group (P < .01). Conclusion: It was found that patellar tendon fibrosis occurred because of overuse and the peak changes occurred at 4 weeks. Jumping load increased the secretions of TGF-β1 and Smad3 in the patellar tendon, with CTGF upregulation and higher synthesis of COL-I and COL-III, which were considered the pathogenesis of fibrosis. Clinical Relevance: This study simulated the effects of jumping load on tendon fibrosis at different time points. Moreover, the time course relationship between jumping training and patellar tendon fibrosis in the rabbit model was determined, which provided a new animal model for the study of patellar tendon fibrosis.

Hydroxycamptothecin Prevents Fibrotic Pathways in Fibroblasts In Vitro.

Peritendinous fibrosis, which leads to impaired tendon function, is a clinical problem worldwide, and it is urgent to explore potential ways to reduce the formation of peritendinous adhesion. Several studies have demonstrated the biological roles of hydroxycamptothecin (HCPT) in inhibiting fibrosis in different tissues. In this study, we investigated whether HCPT could inhibit tendon fibrosis in vitro. Our results revealed that HCPT inhibited transforming growth factor (TGF)-β1-induced cell viability of human fibroblasts, decreased excessive cell hyperproliferation and promoted fibroblasts apoptosis. In addition, HCPT treatment also inhibited expression of fibrosis genes COL3A1 and α-smooth muscle actin (α-SMA). In terms of mechanism, we pretreated fibroblasts with the endoplasmic reticulum stress (ER) inhibitor salubrinal and RNA-dependent protein kinase-like ER kinase (PERK) short hairpin RNA, these treatments abolished the inhibitory effects of HCPT on fibrosis, thereby suggesting that HCPT's inhibition of TGF-β1-induced tendon fibrosis might be mediated by the PERK signaling pathway in vitro. In conclusion, our results suggested that HCPT had protective effects on peritendinous tissue fibrosis and might be promising in future clinical applications. © 2019 IUBMB Life, 71(5):653-662, 2019.

Biologic and mechanical aspects of tendon fibrosis after injury and repair

ABSTRACTTendon injuries of the hand that require surgical repair often heal with excess scarring and adhesions to adjacent tissues. This can compromise the natural gliding mechanics of the flexor tendons in particular, which operate within a fibro-osseous tunnel system similar to a set of pulleys. Even combining the finest suture repair techniques with optimal hand therapy protocols cannot ensure predictable restoration of hand function in these cases. To date, the majority of research regarding tendon injuries has revolved around the mechanical aspects of the surgical repair (i.e. suture techniques) and postoperative rehabilitation. The central principles of treatment gleaned from this literature include using a combination of core and epitendinous sutures during repair and initiating motion early on in hand therapy to improve tensile strength and limit adhesion formation. However, it is likely that the best clinical solution will utilize optimal biological modulation of the healing response in addition to these core strategies and, recently, the research in this area has expanded considerably. While there are no proven additive biological agents that can be used in clinical practice currently, in this review, we analyze the recent literature surrounding cytokine modulation, gene and cell-based therapies, and tissue engineering, which may ultimately lead to improved clinical outcomes following tendon injury in the future.

A mini-invasive technique for severe arthrofibrosis of the knee: A technical note

PurposeIn this article, a mini-invasive technique is described, which consists of arthroscopic adhesiolysis and quadriceps pie-crusting lengthening basing on pre-operative sonographic examination. Sonographic diagnostic value of quadriceps tendon fibrosis is also evaluated. MethodsPre-operative sonographic examination was performed to make an accurate location diagnosis of quadriceps fibrosis. After arthroscopic adhesiolysis, percutaneous pie-crusting release was performed basing on preoperative sonographic examination. An 18-gauge needle was used to puncture the stiff fibrous band of the distal and lateral quadriceps tendon under maximum knee flexion. The contractural quadriceps tendon is gradually released after 60–100 needle punctures. ResultsThis technique was performed in five post-traumatic stiff knees and three stiff knees after previous infection. The contractural rectus femoris tendon is average 22% thinner than contralateral parts according to sonographic measurement. Mean maximum flexion increased from 35° preoperatively to 80° after arthroscopic adhesiolysis and 120° after pie-crusting. ConclusionsThis technique is a simple, effective and mini-invasive method, allowing an immediate, aggressive rehabilitation postoperatively. Pre-operative sonographic location of quadriceps tendon fibrosis could potentially improve the efficacy and accuracy of percutaneous pie-crusting procedures.

Comparison of transforming growth factor beta expression in healthy and diseased human tendon.

BackgroundDiseased tendons are characterised by fibrotic scar tissue, which adversely affects tendon structure and function and increases the likelihood of re-injury. The mechanisms and expression profiles of fibrosis in diseased tendon is understudied compared to pulmonary and renal tissues, where transforming growth factor (TGF)β and its associated superfamily are known to be key drivers of fibrosis and modulate extracellular matrix homeostasis. We hypothesised that differential expression of TGFβ superfamily members would exist between samples of human rotator cuff tendons with established disease compared to healthy control tendons.MethodsHealthy and diseased rotator cuff tendons were collected from patients presenting to an orthopaedic referral centre. Diseased tendinopathic (intact) and healthy rotator cuff tendons were collected via ultrasound-guided biopsy and torn tendons were collected during routine surgical debridement. Immunohistochemistry and quantitative real-time polymerase chain reaction were used to investigate the protein and gene expression profiles of TGFβ superfamily members in these healthy and diseased tendons.ResultsTGFβ superfamily members were dysregulated in diseased compared to healthy tendons. Specifically, TGFβ-1, TGFβ receptor (R)1 and TGFβ R2 proteins were reduced (p < 0.01) in diseased compared to healthy tendons. At the mRNA level, TGFβ R1 was significantly reduced in samples of diseased tendons, whereas TGFβ R2 was increased (p < 0.01). BMP-2, BMP-7 and CTGF mRNA remained unchanged with tendon disease.ConclusionsWe propose that downregulation of TGFβ pathways in established tendon disease may be a protective response to limit disease-associated fibrosis. The disruption of the TGFβ axis with disease suggests associated downstream pathways may be important for maintaining healthy tendon homeostasis. The findings from our study suggest that patients with established tendon disease would be unlikely to benefit from therapeutic TGFβ blockade, which has been investigated as a treatment strategy in several animal models. Future studies should investigate the expression profile of fibrotic mediators in earlier stages of tendon disease to improve understanding of the targetable mechanisms underpinning tendon fibrosis.

M1 and M2 macrophage recruitment during tendon regeneration induced by amniotic epithelial cell allotransplantation in ovine

Recently, we have demonstrated that ovine amniotic epithelial cells (oAECs) allotransplanted into experimentally induced tendon lesions are able to stimulate tissue regeneration also by reducing leukocyte infiltration. Amongst leukocytes, macrophages (Mφ) M1 and M2 phenotype cells are known to mediate inflammatory and repairing processes, respectively. In this research it was investigated if, during tendon regeneration induced by AECs allotransplantation, M1Mφ and M2Mφ phenotype cells are recruited and differently distributed within the lesion site. Ovine AECs treated and untreated (Ctr) tendons were explanted at 7, 14, and 28days and tissue microarchitecture was analyzed together with the distribution and quantification of leukocytes (CD45 positive), Mφ (CD68 pan positive), and M1Mφ (CD86, and IL12b) and M2Mφ (CD206, YM1 and IL10) phenotype related markers. In oAEC transplanted tendons CD45 and CD68 positive cells were always reduced in the lesion site. At day 14, oAEC treated tendons began to recover their microarchitecture, contextually a reduction of M1Mφ markers, mainly distributed close to oAECs, and an increase of M2Mφ markers was evidenced. CD206 positive cells were distributed near the regenerating areas. At day 28 oAECs treated tendons acquired a healthy-like structure with a reduction of M2Mφ. Differently, Ctr tendons maintained a disorganized morphology throughout the experimental time and constantly showed high values of M1Mφ markers. These findings indicate that M2Mφ recruitment could be correlated to tendon regeneration induced by oAECs allotransplantation. Moreover, these results demonstrate oAECs immunomodulatory role also in vivo and support novel insights into their allogeneic use underlying the resolution of tendon fibrosis.

Altered Biomechanical Properties of Gastrocnemius Tendons of Turkeys Infected with Turkey Arthritis Reovirus.

Turkey arthritis reovirus (TARV) causes lameness and tenosynovitis in commercial turkeys and is often associated with gastrocnemius tendon rupture by the marketing age. This study was undertaken to characterize the biomechanical properties of tendons from reovirus-infected turkeys. One-week-old turkey poults were orally inoculated with O'Neil strain of TARV and observed for up to 16 weeks of age. Lameness was first observed at 8 weeks of age, which continued at 12 and 16 weeks. At 4, 8, 12, and 16 weeks of age, samples were collected from legs. Left intertarsal joint with adjacent gastrocnemius tendon was collected and processed for histological examination. The right gastrocnemius tendon's tensile strength and elasticity modulus were analyzed by stressing each tendon to the point of rupture. At 16 weeks of age, gastrocnemius tendons of TARV-infected turkeys showed significantly reduced (P < 0.05) tensile strength and modulus of elasticity as compared to those of noninfected control turkeys. Gastrocnemius tendons revealed lymphocytic tendinitis/tenosynovitis beginning at 4 weeks of age, continuing through 8 and 12 weeks, and progressing to fibrosis from 12 to 16 weeks of age. We propose that tendon fibrosis is one of the key features contributing to reduction in tensile strength and elasticity of gastrocnemius tendons in TARV-infected turkeys.

Rotator cuff re-tear or non-healing: histopathological aspects and predictive factors

The aim of the study was to evaluate the histopathological changes that occur in the tendon and subacromial bursal tissue in patients with rotator cuff tear trying to correlate these changes to their healing capability. Eighty-four patients were clinically evaluated with the Constant Scale. Radiographs and MRI were performed preoperatively and ultrasound were performed postoperatively. For each patient, a biopsy of the supraspinatus tendon and subacromial bursa was performed, and the specimens were histopathologically analyzed. Tendons histopathological features consisted of loss of structural organization, poor or absent neoangiogenesis, chondral metaplasia, and fibrosis. Bursal features consisted of neoangiogenesis, absence of chondral metaplasia, hyperplasia/hypertrophy, and absence of necrosis. Direct correlation was seen between tendon and bursal hyperplasia and time of the onset of symptoms; between tendon chondral metaplasia, fibrosis, bursal neoangiogenesis, inflammation, and patient age; between tendon neoangiogenesis, hyperplasia, necrosis, fibrosis, bursal necrosis, inflammation, and lesion size; on the contrary, tendon fibrosis, necrosis, and bursal tissue inflammation decrease as time passes from the onset of symptoms. Tendon fibers disarray, neoangiogenesis, and inflammation decreases as the patient's age increases. Bursal tissue fibrosis decreases as lesion size increases. Simple histopathological techniques should be employed routinely to assess the tissue quality, with the aim to predict future clinical evolution (repair or non-repair). Comparing the histopathological data with the demographical information and the descriptive statistics, it is possible to define the RCT repair at risk and identify which RCT will be able to heal.