Challenges and perspectives of tendon-derived cell therapy for tendinopathy: from bench to bedside.

Tendon is composed of dense fibrous connective tissues, connecting muscle at the myotendinous junction (MTJ) to bone at the enthesis and allowing mechanical force to transmit from muscle to bone. Tendon diseases occur at different zones of the tendon, including enthesis, MTJ and midsubstance of the tendon, due to a variety of environmental and genetic factors which consequently result in different frequencies and recovery rates. Self-healing properties of tendons are limited, and cell therapeutic approaches in which injured tendon tissues are renewed by cell replenishment are highly sought after. Homologous use of individual's tendon-derived cells, predominantly differentiated tenocytes and tendon-derived stem cells, is emerging as a treatment for tendinopathy through achieving minimal cell manipulation for clinical use. This is the first review summarizing the progress of tendon-derived cell therapy in clinical use and its challenges due to the structural complexity of tendons, heterogeneous composition of extracellular cell matrix and cells and unsuitable cell sources. Further to that, novel future perspectives to improve therapeutic effect in tendon-derived cell therapy based on current basic knowledge are discussed.

Reduction of mechanical loading in tendons induces heterotopic ossification and activation of the ß-catenin signaling pathway.

BACKGROUND: Tendons are the force transferring tissue that enable joint movement. Excessive mechanical loading is commonly considered as a primary factor causing tendinopathy, however, an increasing body of evidence supports the hypothesis that overloading creates microdamage of collagen fibers resulting in a localized decreased loading on the cell population within the damaged site. Heterotopic ossification is a complication of late stage tendinopathy, which can significantly affect the mechanical properties and homeostasis of the tendon. Here, we the examine the effect of mechanical underloading on tendon ossification and investigate its underlying molecular mechanism. METHOD: Rabbit Achilles tendons were dissected and cultured in an underloading environment (3% cyclic tensile stain,0.25 â€‹Hz, 8 â€‹h/day) for either 10, 15 or 20 days. Using isolated tendon-derived stem cells (TDSCs) 3D constructs were generated, cultured and subjected to an underloading environment for 6 days. Histological assessments were performed to evaluate the structure of the 3D constructs; qPCR and immunohistochemistry were employed to study TDSC differentiation and the ß-catenin signal pathway was investigated by Western blotting. Mechanical testing was used to determine ability of the tendon to withstand force generation. RESULT: Tendons cultured for extended times in an environment of underloading showed progressive heterotopic ossification and a reduction in biomechanical strength. qPCR revealed that 3D TDSCs constructs cultured in an underloading environment exhibited increased expression of several osteogenic genes: these include RUNX2, ALP and osteocalcin in comparison to tenogenic differentiation markers (scleraxis and tenomodulin). Immunohistochemical analysis further confirmed high osteocalcin production in 3D TDSCs constructs subject to underloading. Western blotting of TDSC constructs revealed that ß-catenin accumulation and translocation were associated with an increase in phosphorylation at Ser552 and decrease phosphorylation at Ser33. CONCLUSION: These findings unveil a potential mechanism for heterotopic ossification in tendinopathy due to the underloading of TDSCs at the damage sites, and also that ß-catenin could be a potential target for treating heterotopic ossification in tendons. THE TRANSLATIONAL POTENTIAL: Tendon heterotopic ossification detrimentally affect quality of life especially for those who has atheletic career. This study reveals the possible mechanism of heterotpic ossification in tendon related to mechanical loading. This study provided the possible to develop a mechanical stimulation protocol for preventive and therapeutic purpose for tendon heterotopic ossification.

Load-induced regulation of tendon homeostasis by SPARC, a genetic predisposition factor for tendon and ligament injuries.

Tendons and tendon interfaces have a very limited regenerative capacity, rendering their injuries clinically challenging to resolve. Tendons sense muscle-mediated load; however, our knowledge on how loading affects tendon structure and functional adaption remains fragmentary. Here, we provide evidence that the matricellular protein secreted protein acidic and rich in cysteine (SPARC) is critically involved in the mechanobiology of tendons and is required for tissue maturation, homeostasis, and enthesis development. We show that tendon loading at the early postnatal stage leads to tissue hypotrophy and impaired maturation of Achilles tendon enthesis in Sparc -/- mice. Treadmill training revealed a higher prevalence of spontaneous tendon ruptures and a net catabolic adaptation in Sparc -/- mice. Tendon hypoplasia was attenuated in Sparc -/- mice in response to muscle unloading with botulinum toxin A. In vitro culture of Sparc -/- three-dimensional tendon constructs showed load-dependent impairment of ribosomal S6 kinase activation, resulting in reduced type I collagen synthesis. Further, functional calcium imaging revealed that lower stresses were required to trigger mechanically induced responses in Sparc -/- tendon fascicles. To underscore the clinical relevance of the findings, we further demonstrate that a missense mutation (p.Cys130Gln) in the follistatin-like domain of SPARC, which causes impaired protein secretion and type I collagen fibrillogenesis, is associated with tendon and ligament injuries in patients. Together, our results demonstrate that SPARC is a key extracellular matrix protein essential for load-induced tendon tissue maturation and homeostasis.

Intramuscular injection of Botox causes tendon atrophy by induction of senescence of tendon-derived stem cells.

BACKGROUND: Botulinum toxin (Botox) injection is in widespread clinical use for the treatment of muscle spasms and tendinopathy but the mechanism of action is poorly understood. HYPOTHESIS: We hypothesised that the reduction of patellar-tendon mechanical-loading following intra-muscular injection of Botox results in tendon atrophy that is at least in part mediated by the induction of senescence of tendon-derived stem cells (TDSCs). STUDY DESIGN: Controlled laboratory study METHODS: A total of 36 mice were randomly divided into 2 groups (18 Botox-injected and 18 vehicle-only control). Mice were injected into the right vastus lateralis of quadriceps muscles either with Botox (to induce mechanical stress deprivation of the patellar tendon) or with normal saline as a control. At 2 weeks post-injection, animals were euthanized prior to tissues being harvested for either evaluation of tendon morphology or in vitro studies. TDSCs were isolated by cell-sorting prior to determination of viability, differentiation capacity or the presence of senescence markers, as well as assessing their response to mechanical loading in a bioreactor. Finally, to examine the mechanism of tendon atrophy in vitro, the PTEN/AKT-mediated cell senescence pathway was evaluated in TDSCs from both groups. RESULTS: Two weeks after Botox injection, patellar tendons displayed several atrophic features including tissue volume reduction, collagen fibre misalignment and increased degradation. A colony formation assay revealed a significantly reduced number of colony forming units of TDSCs in the Botox-injected group compared to controls. Multipotent differentiation capacities of TDSCs were also diminished after Botox injection. To examine if mechanically deprived TDSC are capable of forming tendon tissue, we used an isolated bioreactor system to culture tendon constructs using TDSC. These results showed that TDSCs from the Botox-treated group failed to restore tenogenic differentiation after appropriate mechanical loading. Examination of the signalling pathway revealed that injection of Botox into quadriceps muscles causes PTEN/AKT-mediated cell senescence of TDSCs. CONCLUSION: Intramuscular injection of Botox interferes with tendon homeostasis by inducing tendon atrophy and senescence of TDSCs. Botox injection may have long-term adverse consequences for the treatment of tendinopathy. CLINICAL RELEVANCE: Intramuscular Botox injection for tendinopathy or tendon injury could result in adverse effects in human tendons and evaluation of its long-term efficacy is warranted.

In vitro loading models for tendon mechanobiology.

Tendons are the connective tissue responsible for transferring force from muscles to bones. A key factor in tendon development, maturation, repair, and degradation is its biomechanical environment. Understanding tendon mechanobiology is essential for the development of injury prevention strategies, rehabilitation protocols and potentially novel treatments in tendon injury and degeneration. Despite the simple overall loading on tendon tissue, cells within the tissue in vivo experience a much more complex mechanical environment including tension, compression and shear forces. This creates a substantial challenge in the establishment of in vitro loading models of the tendon. This article reviews multiple loading models used for the study of tendon mechanobiology and summarizes the main findings. Although impressive progress has been achieved in the functionality and mimicry of in vitro loading models, an ideal platform is yet to be developed. Multidisciplinary approaches and collaborations will be the key to unveiling the tendon mechanobiology. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:566-575, 2018.

Hospital discharge information after elective total hip or knee joint replacement surgery: A clinical audit of preferences among general practitioners.

The demand for elective joint replacement (EJR) surgery for degenerative joint disease continues to rise in Australia, and relative to earlier practices, patients are discharged back to the care of their general practitioner (GP) and other community-based providers after a shorter hospital stay and potentially greater post-operative acuity. In order to coordinate safe and effective post-operative care, GPs rely on accurate, timely and clinically-informative information from hospitals when their patients are discharged. The aim of this project was to undertake an audit with GPs regarding their preferences about the components of information provided in discharge summaries for patients undergoing EJR surgery for the hip or knee.GPs in a defined catchment area were invited to respond to an online audit instrument, developed by an interdisciplinary group of clinicians with knowledge of orthopaedic surgery practices. The 15-item instrument required respondents to rank the importance of components of discharge information developed by the clinician working group, using a three-point rating scale.Fifty-three GPs and nine GP registrars responded to the audit invitation (11.0% response rate). All discharge information options were ranked as 'essential' by a proportion of respondents, ranging from 14.8-88.5%. Essential information requested by the respondents included early post-operative actions required by the GP, medications prescribed, post-operative complications encountered and noting of any allergies. Non-essential information related to the prosthesis used. The provision of clinical guidelines was largely rated as 'useful' information (47.5-56.7%).GPs require a range of clinical information to safely and effectively care for their patients after discharge from hospital for EJR surgery. Implementation of changes to processes used to create discharge summaries will require engagement and collaboration between clinical staff, hospital administrators and information technology staff, supported in parallel by education provided to junior medical staff.

Clinical results and risk factors for reinjury 15 years after anterior cruciate ligament reconstruction: a prospective study of hamstring and patellar tendon grafts.

BACKGROUND: There is a lack of prospective studies comparing the long-term outcome of endoscopic anterior cruciate ligament (ACL) reconstruction with either a patellar tendon or hamstring tendon autograft. PURPOSE: This prospective longitudinal study compared the results of isolated endoscopic ACL reconstruction utilizing a 4-strand hamstring tendon (HT) or patellar tendon (PT) autograft over a 15-year period with respect to reinjury, clinical outcomes, and the development of osteoarthritis. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Ninety consecutive patients with isolated ACL rupture were reconstructed with a PT autograft, and 90 patients received an HT autograft, with an identical surgical technique. Patients were assessed at 2, 5, 7, 10, and 15 years. Assessment included the International Knee Documentation Committee (IKDC) knee ligament evaluation including radiographic evaluation, KT-1000 arthrometer testing, and Lysholm knee score. RESULTS: Patients who received the PT graft had significantly worse outcomes compared with those who received the HT graft at 15 years for the variables of radiologically detectable osteoarthritis (grade A: 46% in PT and 69% in HT; P = .04), motion loss (extension deficit <3°: 79% in PT and 94% in HT; P = .03), single-legged hop test (grade A: 65% in PT and 92% in HT; P = .001), participation in strenuous activity (very strenuous or strenuous: 62% of PT and 77% of HT; P = .04), and kneeling pain (moderate or greater pain: 42% of PT and 26% of HT; P = .04). There was no significant difference between the HT and PT groups in overall IKDC grade (grade A: 47% of PT and 57% of HT; P = .35). An ACL graft rupture occurred in 17% of the HT group and 8% of the PT group (P = .07). An ACL graft rupture was associated with nonideal tunnel position (odds ratio [OR], 5.0) and male sex (OR, 3.2). Contralateral ACL rupture occurred in significantly more PT patients (26%) than HT patients (12%) (P = .02) and was associated with age ≤18 years (OR, 4.1) and the PT graft (OR, 2.6). CONCLUSION: Anterior cruciate ligament reconstruction using ipsilateral autograft continues to show excellent results in terms of patient satisfaction, symptoms, function, activity level, and stability. The use of HT autograft does, however, show better outcomes than the PT autograft in all of these outcome measures. Additionally, at 15 years, the HT graft-reconstructed ACLs have shown a lower rate of radiological osteoarthritis.

A new technique for cement augmentation of the sliding hip screw in proximal femur fractures.

BACKGROUND: Fractures of the osteoporotic proximal femur are a significant source of mortality and morbidity in today's ageing population. Even with modern fixation techniques such as the sliding hip screw, a certain percentage of fixations will fail due to cut-out of the screw. This study presents a new method for augmenting hip screws with cement to reinforce the fixation. METHODS: Unstable pertrochanteric fractures were created in paired osteoporotic cadaver femora (n=10). The fractures were fixed using either standard fixation techniques (dynamic hip screw), or using a dynamic hip screw augmented with cement. Cement was introduced using a customised jig to guide cement into a region superior to the screw in the femoral head. Cut-out resistance was assessed using a biaxial material testing machine, with loading applied in compression until failure. FINDINGS: The new cement augmentation technique significantly improved the cut-out strength of the fixation (mean 42%; P=0.032). The failure mechanism for both groups was the same, with failure occurring through compression of the cancellous bone superior to the screw. The mean increase in temperature at the femoral neck was 3.7 degrees C in augmented bones, which is much lower than values previously reported for polymethylmethacrylate cements. INTERPRETATION: Several benefits with this technique have emerged. The method is technically straightforward. The risk of cement penetration into the joint is reduced, and cement is targetted to the areas of the femoral head where it is most needed. The exothermic reaction is minimised by reducing the volume of cement used. The first clinical results are promising.