Musculoskeletal diseases are having a growing impact worldwide. It is therefore crucial to have an evidence base to most effectively and efficiently implement future health services across different healthcare systems. International trials are an opportunity to address these challenges and have many potential benefits. They are, however, complex to set up and deliver, which may impact on the efficient and timely delivery of a project. There are a number of models of how international trials are currently being delivered across a range of orthopaedic patient populations, which are discussed here. The examples given highlight that the key to overcoming these challenges is the development of trusted and equal partnerships with collaborators in each country. International trials have the potential to address a global burden of disease, and in turn optimize the benefit to patients in the collaborating countries and those with similar health services and care systems. Cite this article: Bone Joint J 2023;105-B(7):719–722

Introduction

Studies have addressed the issue of increasing prevalence of work-related musculoskeletal (MSK) pain among different occupations. However, contributing factors to MSK pain have not been fully investigated among orthopaedic surgeons. Thus, this study aimed to approximate the prevalence and predictors of MSK pain among Saudi orthopaedic surgeons working in Riyadh, Saudi Arabia.

Biomaterials with mechanical or biological competence are ubiquitous in musculoskeletal disorders, and understanding the inflammatory response they trigger is key to guide tissue regeneration. While macrophage role has been widely investigated, immune response is regulated by other immune cells, including neutrophils, the most abundant leukocyte in human blood. As first responders to injury, infection or material implantation, neutrophils recruit other immune cells, and therefore influence the onset and resolution of chronic inflammation, and macrophage polarization. This response depends on the physical and chemical properties of the biomaterials, among other factors. In this study we report an in vitro culture model to describe the most important neutrophil functions in relation to tissue repair. We identified neutrophil survival and death, neutrophils extracellular trap formation, release of reactive oxygen species and degranulation with cytokines release as key functions and introduced a corresponding array of assays. These tests were suitable to identify clear differences in the response by neutrophils that were cultured on material of different origin, stiffness and chemical composition. Overall, substrates from biopolymers of natural origin resulted in increased survival, less neutrophil extracellular trap formation, and more reactive oxygen species production than synthetic polymers. Within the range of mechanical properties explored (storage modulus below 5 k Pa), storage modulus of covalently crosslinked hyaluronic acid hydrogels did not significantly alter neutrophils response, whereas polyvinyl alcohol gels of matching mechanical properties displayed a response indicating increased activation. Additionally, we present the effect of material stiffness, charge, coating and culture conditions in the measured neutrophils response. Further studies are needed to correlate the neutrophil response to tissue healing. By deciphering how neutrophils initiate and modulate the immune response to material implantation, we aim at introducing new principles to design immunomodulatory biomaterials for musculoskeletal disorders. Acknowledgments. This work was supported by the AO Foundation, AO CMF, grant AOCMF-21-04S

Aims. Degenerative cervical spondylosis (DCS) is a common musculoskeletal disease that encompasses a wide range of progressive degenerative changes and affects all components of the cervical spine. DCS imposes very large social and economic burdens. However, its genetic basis remains elusive. Methods. Predicted whole-blood and skeletal muscle gene expression and genome-wide association study (GWAS) data from a DCS database were integrated, and functional summary-based imputation (FUSION) software was used on the integrated data. A transcriptome-wide association study (TWAS) was conducted using FUSION software to assess the association between predicted gene expression and DCS risk. The TWAS-identified genes were verified via comparison with differentially expressed genes (DEGs) in DCS RNA expression profiles in the Gene Expression Omnibus (GEO) (Accession Number: GSE153761). The Functional Mapping and Annotation (FUMA) tool for genome-wide association studies and Meta tools were used for gene functional enrichment and annotation analysis. Results. The TWAS detected 420 DCS genes with p < 0.05 in skeletal muscle, such as ribosomal protein S15A (RPS15A) (PTWAS = 0.001), and 110 genes in whole blood, such as selectin L (SELL) (PTWAS = 0.001). Comparison with the DCS RNA expression profile identified 12 common genes, including Apelin Receptor (APLNR) (PTWAS = 0.001, PDEG = 0.025). In total, 148 DCS-enriched Gene Ontology (GO) terms were identified, such as mast cell degranulation (GO:0043303); 15 DCS-enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified, such as the sphingolipid signalling pathway (ko04071). Nine terms, such as degradation of the extracellular matrix (R-HSA-1474228), were common to the TWAS enrichment results and the RNA expression profile. Conclusion. Our results identify putative susceptibility genes; these findings provide new ideas for exploration of the genetic mechanism of DCS development and new targets for preclinical intervention and clinical treatment. Cite this article: Bone Joint Res 2023;12(1):80–90

Introduction and Objective. The use of microfragmented adipose tissue (mFAT) for the treatment of musculoskeletal disorders, especially osteoarthritis, is gaining popularity following the positive results reported in recent case series and clinical trials. The purpose of this study is to characterize mFAT in terms of structure, cell content and secretome (i.e. protein and microvescicles released as paracrine mediators), and to compare it with unprocessed lipoaspirate tissue, in order to understand the possible mechanisms of action and the benefit derived from tissue processing. Materials and Methods. Unprocessed lipoaspirate (LA) and mFAT were obtained from 7 donors. Each tissue sample was divided in four aliquots: A) fixed in formalin for histological evaluation; B) enzymatically digested to harvest cells with the exclusion of adipocytes; C) cultured for 24 hours in serum-free DMEM to harvest secretome; D) freshly frozen for proteomic evaluation. Hematoxylin and eosin staning, as well as immunohistochemistry for CD31, CD90, CD146 were performed on aliquot A. Cell count, viability, senescence and immunophenotype were assessed on aliquot B. Culture medium from aliquot C was collected and used for proteomic analysis and micro-RNA extraction and quantitation from extracellular vesicles. Aliquot D was lysed, protein were extracted and analyzed using a high-throughput proteomic approach. Results. Histological investigations showed a lower red blood cell content in mFAT with respect to LA, while the presence of blood vessels (CD31+), stromal cells (CD90) and pericytes (CD146) was similar in all samples. These results were confirmed by flow cytometry, with reduction of erythrocytes (CD235a+) by 76% and reduction of lymphocytes (CD45+) by 79% in mFAT compared to LA. Otherwise, the proportions of stromal cells, pericytes and endothelial cells in LA and mFAT remained comparable. The percentage of senescent cells resulted similar before and after tissue processing, with very low values (< 5%). The analysis of the miRNAs contained in the extracellular vesicles in culture media identified 376 miRNAs in LA secretome and 381 in mFAT secretome. A high correlation in the expression of these miRNAs within subjects (LA and mFAT of each donor) was observed (R2> 0.8), indicating that processing in mFAT does not significantly alter the portfolio of miRNAs associated with extracellular vesicles. Proteomic analysis of secretome revealed that 217 proteins significantly differ between LA and mFAT. In particular, protein associated with acute phase were less represented in mFAT secretome, while intracellular proteins were more frequent. Proteomic analysis of tissues demonstrated a reduction of protein related to extracellular matrix and of proteins closely related to peripheral blood contamination in mFAT with respect to LA. Conclusions. Taken together, these results suggest that processing of LA into mFAT allow for removal of blood elements, in terms of red blood cells, lymphocytes, acute phase and complement system proteins, and for the reduction of extracellular matrix components. Otherwise, tissue structure, cell populations, cell viability and senescence are not influenced by tissue processing. Then, microfragmentation process represents a safe and efficient method for the application of adipose tissue properties to musculoskeletal disorders, allowing for the maintenance of all the effector elements for tissue regeneration while removing possible detrimental agents such as inflammatory mediators

Bone tissue is known to possess an intrinsic regeneration potential. However, in cases of major injury, trauma, and disease, bone loss is present, and the regeneration potential of the tissue is often impaired. The process of bone regeneration relies on a complex interaction of molecules. MicroRNAs (miRNA) are small, non-coding RNAs that inhibit messenger RNAs (mRNA). One miRNA can inhibit several mRNAs and one mRNA can be inhibited by several miRNAs. Functionally, miRNAs regulate the entire proteome via the local inhibition of translation. In fact, miRNA modulation has been shown to be involved in several musculoskeletal diseases. 1. In those pathologies, they modulate the transcriptional activity of mRNAs important for differentiation, tissue-specific activity, extracellular matrix production, etc. Because of their function in inhibiting translation, miRNAs are being researched in many diseases and are already being used for interventional treatment. 2. Bone tissue and its related conditions have been widely investigated up to this day. 1,3. This talk will focus on the relevancy of miRNAs to bone tissue, its homeostasis, and disease. After, examples will be given of how miRNAs can be used in bone regeneration and diseases such as osteoporosis and osteosarcoma. The use of miRNAs in both, detection and therapy will be discussed

Aims. Osteoarthritis (OA) is the most prevalent systemic musculoskeletal disorder, characterized by articular cartilage degeneration and subchondral bone (SCB) sclerosis. Here, we sought to examine the contribution of accelerated growth to OA development using a murine model of excessive longitudinal growth. Suppressor of cytokine signalling 2 (SOCS2) is a negative regulator of growth hormone (GH) signalling, thus mice deficient in SOCS2 (Socs2. -/-. ) display accelerated bone growth. Methods. We examined vulnerability of Socs2. -/-. mice to OA following surgical induction of disease (destabilization of the medial meniscus (DMM)), and with ageing, by histology and micro-CT. Results. We observed a significant increase in mean number (wild-type (WT) DMM: 532 (SD 56); WT sham: 495 (SD 45); knockout (KO) DMM: 169 (SD 49); KO sham: 187 (SD 56); p < 0.001) and density (WT DMM: 2.2 (SD 0.9); WT sham: 1.2 (SD 0.5); KO DMM: 13.0 (SD 0.5); KO sham: 14.4 (SD 0.7)) of growth plate bridges in Socs2. -/-. in comparison with WT. Histological examination of WT and Socs2. -/-. knees revealed articular cartilage damage with DMM in comparison to sham. Articular cartilage lesion severity scores (mean and maximum) were similar in WT and Socs2. -/-. mice with either DMM, or with ageing. Micro-CT analysis revealed significant decreases in SCB thickness, epiphyseal trabecular number, and thickness in the medial compartment of Socs2. -/-. , in comparison with WT (p < 0.001). DMM had no effect on the SCB thickness in comparison with sham in either genotype. Conclusion. Together, these data suggest that enhanced GH signalling through SOCS2 deletion accelerates growth plate fusion, however this has no effect on OA vulnerability in this model. Cite this article: Bone Joint Res 2022;11(3):162–170

Distal arthrogryposis (DA) is a collection of rare developmental disorders characterized by congenital joint contractures. Most arthrogryposis mutations are in muscle- and joint-related genes, and the anatomical defects originate cell-autonomously within the musculoskeletal tissues. However, gain-of-function (GOF) mutations in PIEZO2, a principal mechanosensor in somatosensation, cause DA subtype 5 via unknown mechanisms. We show that expression of a GOF PIEZO2 mutation in proprioceptive sensory neurons mainly innervating muscle spindles and tendons is sufficient to induce DA5-like phenotypes in mice. Overactive PIEZO2 causes anatomical defects via increased activity within the peripheral nervous system during postnatal development. Surprisingly, overactive PIEZO2 is likely to cause joint abnormalities via increased exocytosis from sensory neuron endings without involving motor circuitry. This reveals a role for somatosensory neurons: excessive mechanosensation within these neurons disrupts musculoskeletal development. We also present proof-of-concept that Botox injection or dietary treatment can counteract the effect of overactive PIEZO2 function to evade DA-like phenotypes in mice when applied during a developmental critical period. These approaches might have clinical applications. Beyond this, our findings call attention to the importance of considering sensory mechanotransduction when diagnosing and treating other musculoskeletal disorders. Acknowledgements: Our work is supported by National Institutes of Health grant (R35 NS105067, R01 DE022358, R25 SC3GM127195, R25 GM07138, R01GM133845, intramural) and Howard Hughes Medical Institute

The presentation of musculoskeletal disease differs in men and women, and recognition of the differences between men and women's burden of disease and response to treatment is critical to optimizing care. In this presentation, I will discuss the expanding evidence in the literature that examine the role of sex and gender in musculoskeletal disease, including how its examination increases the innovations and contributions, as well as expands the knowledge about musculoskeletal disease, conditions, and injury in a broad sense. We will discuss the role that structural anatomy differences, hormones, and genetics play in differential disease expression, to the historical biases in the subject populations of clinical and basic research projects. Participants will be provided with examples and opportunities to evaluate orthopaedic science through a sex and gender lens, and what impact this may play in setting the stage for both clinical practice and scientific investigation

Purpose and background. Nearly 70% of UK physiotherapists experience work-related musculoskeletal disorders (WRMSDs) during their career, with a significant proportion occurring in the back and being attributed to patient handling tasks. Evidence suggests that manual handling training alone is ineffective and interventions among nurses indicate that a tailored approach, including targeted exercise (TE), can reduce WRMSD rates. This study aimed to explore physiotherapists’ perspectives of WRMSDs, patient handling, and the role of TE in reducing WRMSDs among physiotherapists. Methods and Results. Key informant interviews were conducted with 4 physiotherapy operational leads and 1 manual handling trainer from NHS Grampian. Interviews were transcribed and Framework Analysis was utilised to identify key themes, including challenges, barriers, and facilitators. Following this, two online focus groups were conducted with 7 qualified NHS physiotherapists across the UK. Views of manual handling training varied across specialities, with some finding it comprehensive and adaptable, and others finding it less applicable to patients in their speciality or community setting. Physiotherapist views on fitness for work varied, with some highlighting the necessity of TE to ensure workforce health whilst others considered exercise to be a personal matter. Facilitators to implementation identified by participants were having support from management and a strong justification for the exercise content. Varied work schedules and facilities were identified as barriers to implementation of a work-based TE intervention. Conclusion. Varying perspectives on TE interventions and barriers to implementation were identified. This work will inform future research to develop TE interventions in consultation with key stakeholders. Conflicts of Interest. No conflicts of interest. Source of Funding. NHS Endowment Research Grant 22/001

Intervertebral disc (IVD) degeneration is responsible for severe clinical symptoms including chronic back pain. Galectins are a family of carbohydrate-binding proteins, some of which can induce functional disease markers in IVD cells and other musculoskeletal diseases. Galectins −4 and −8 were shown to trigger disease-promoting activity in chondrocytes but their effects on IVD cells have not been investigated yet. This study elucidates the role of galectin-4 and −8 in IVD degeneration. Immunohistochemical evidence for the presence of galectin-4 and −8 in the IVD was comparatively provided in specimens of 36 patients with spondylochondrosis, spondylolisthesis, or spinal deformity. Confocal microscopy revealed co-localization of galectin-4 and −8 in chondrocyte clusters of degenerated cartilage. The immunohistochemical presence of galectin-4 correlated with histopathological and clinical degeneration scores of patients, whereas galectin-8 did not show significant correlations. The specimens were separated into annulus fibrosus (AF), nucleus pulposus (NP) and endplate, which was confirmed histologically. Separate cell cultures of AF and NP (n=20) were established and characterized using cell type-specific markers. Potential binding sites for galectins including sialylated N-glycans and LacdiNAc structures were determined in AF and NP cells using LC/ESI-MS-MS. To assess galectin functions, cell cultures were treated with recombinant galectin-4 or −8, in comparison to IL-1β, and analyzed using RT-qPCR and In-cell Western blot. In vitro, both galectins triggered the induction of functional disease markers (CXCL8 and MMP3) on mRNA level and activated the nuclear factor-kB pathway. NP cells were significantly more responsive to galectin-8 and Il-1β than AF cells. Phosphorylation of p-65 was time-dependently induced by both galectins in both cell types to a comparable extent. Taken together, this study provides evidence for a functional role of glycobiological processes in IVD degeneration and highlights galectin-4 and −8 as regulators of pro-inflammatory and degrative processes in AF and NP cells

Purpose and Background. Work-related musculoskeletal disorders (WRMSD) can affect 56–80% of physiotherapists. Patient handling is reported as a significant risk factor for developing WRMSD with the back most frequently injured. Physiotherapists perform therapeutic handling to manually assist and facilitate patients’ movement to aid rehabilitation, which can increase physiotherapists risk of experiencing high forces during patient handling. Methods and Results. A descriptive cross-sectional study was completed to explore and quantitatively measure the movement of ten physiotherapists during patient handling, over one working day, in a neurological setting. A wearable 3-dimensional motion analysis system, Xsens (Movella, Henderson, NV), was used to measure physiotherapist movement and postures in the ward setting during patient treatment sessions. The resulting joint angles were reported descriptively and compared against a frequently used ergonomic assessment tool, the Rapid Upper Limb Assessment (RULA). Physiotherapists adopted four main positions during patient handling tasks: 1) kneeling; 2) half-kneeling; 3) standing; and 4) sitting. Eight patient handling tasks were identified and described: 1) Lie-to-sit; 2) sit-to-lie; 3) sit-to-stand; facilitation of 4) upper limb; 5) lower limb; 6) trunk; and 7) standing treatments; and 8) walking facilitation. Kneeling and sitting positions demonstrated greater neck extension and greater lumbosacral flexion during treatments which scores highly with the RULA. Conclusion. This research identified that patient treatment tasks were more often performed in kneeling or sitting positions than standing. Current moving and handling guidance teaches moving and handling in a standing position; loading and stresses experienced by the physiotherapists may differ in sitting or kneeling positions. Conflicts of interest. None. Sources of funding. None. This work has been presented as a poster at the CSP conference Glasgow 2023

Background. Musculoskeletal disorders, including low back pain, affects 68% of UK physiotherapists across their career with patient handling considered a key risk factor. Manual handling training is mandatory for all allied health professionals, however there is limited research investigating whether professionals adopt recommended manual handling principles following training. Purpose of Study. To investigate spinal angles when facilitating sit-to-stand, and a turning manoeuvre in bed, comparing first-year physiotherapy students (who have not received manual handling training) with final-year physiotherapy students (who have received manual handling training). Methods. Cross-sectional pilot study (n= 20; 10 first-year, 10 final-year). All participants were exposed to a short training video outlining how to safely perform each manoeuvre. Retroreflective markers were attached to: L4, ASIS, PSIS, T12, C7, tragus and canthus. Spinal (neck, thoracic, lumbar and pelvic) angles were established via digital photographs using a bespoke MATLAB programme (MathWorks). A Mann-Whitney U test was conducted to determine between group differences. Results. No statistically significant results were observed between first-year and final-year students for both manoeuvres (p<0.05), except for neck angle during the turning manoeuvre (final-year students demonstrating more upright postures, p=0.037). Interestingly, for the turning manoeuvre in bed it was noted that none of the participants adjusted the bed height. Conclusion. The results suggest that clinical experience and routine manual handling training may not have a significant effect on spinal posture, especially in relation to pelvic, lumbar and thoracic angles. Further work is needed to understand how training relates to adoption of manual handling principles in practice. Conflicts of interest. None. Sources of funding. None

Purpose. The purpose of this study was to discover if student led clinics (SLC) are feasible delivery mechanisms for Low back pain (LBP) self-management support and to develop a service model. Background. LBP is the most commonly reported musculoskeletal disorder worldwide. The increasing service and workforce demands of LBP are challenging for providers and policy makers. self-management is appropriate for many people living with LBP yet guidance for self-management is lacking. One potential delivery mechanism is through SLC. These are ‘clinics’ run by students, supervised by clinicians. Methods and Results. A scoping review has found that SLC can be effective for supporting self-management of various long-term conditions and can provide cost benefits compared with traditional clinical services. In principle, their use for providing LBP services could have similar advantages as well as mitigating the clinical placement shortage. A further scoping review of self-management support for LBP was used to develop a model for student-led LBP clinics. The proposed model is a student led LBP supported self-management service. The service users will be triaged using the Psychosocial Flags Framework to identify obstacles to participation, followed by 1–6 sessions of self-management support comprising of; 1) empathetic listening and education to build a therapeutic relationship and to dispel LBP myths; 2) collaboratively setting meaningful goals; 3) imparting knowledge and skills to overcome the identified obstacles; 4) developing an evidence-informed plan for self-management, agreed with relevant stakeholders. Conclusion. Previous experience and the evidence-base suggest that SLC are feasible for delivering self-management support for LBP. Conflicts of interest: No conflicts of interest. Sources of funding: No funding obtained

Purpose and background. Work-related musculoskeletal disorders, particularly back pain, are a significant issue for healthcare workers, with patient handling being the most frequently reported risk factor. Patient handling is often performed without assistive devices or equipment, which can cause healthcare staff to maintain awkward postures or experience high loads. This review aimed to comprehensively map the literature surrounding manual patient handling (without assistive devices) by healthcare practitioners to identify the current evidence-base on moving and handling of patients and explore what primary research had been conducted. Methods and results. JBI methodology for scoping reviews and an a priori registered protocol (DOI 10.17605/OSF.IO/8PR7A) was followed and AMED, CINAHL, MEDLINE, SPORTDiscus and EMBASE databases were searched. Literature published in English between 2002 and 2021 was included. Forty-nine records were included: 36 primary research studies, 1 systematic review and 12 ‘other’ including narrative and government reports. Primary research predominantly used observational cross-sectional designs (n = 21 studies). Most studies took place in hospitals (n = 13) and laboratories (n = 12). Nurses formed the largest population group (n = 13), with very little research on physiotherapists and other allied health professionals. Conclusion. This scoping review comprehensively reviewed the available literature in the area. Most of the included primary research was observational. Nurses were often investigated in hospitals and laboratories. Qualitative research investigating moving and handling and further biomechanical investigation into therapeutic handling by healthcare staff were identified as areas for further research. Conflicts of interest. None. Sources of funding. None. This work has been published in Physiotherapy: Johnson, K., Swinton, P., Pavlova, A. and Cooper, K., 2023. Manual patient handling in the healthcare setting: a scoping review. Physiotherapy. (120) 60–77 . https://doi.org/10.1016/j.physio.2023.06.003

It is known that the gait dynamics of elderly substantially differs from that of young people. However, it has not been well studied how this age-related gait dynamics affects the knee biomechanics, e.g., cartilage mechanical response. In this study, we investigated how aging affects knee biomechanics in a female population using subject-specific computational models. Two female subjects (ages of 23 and 69) with no musculoskeletal disorders were recruited. Korea National Institute for Bioethics Policy Review Board approved the study. Participants walked at a self-selected speed (SWS), 110% of SWS, and 120% of SWS on 10 m flat ground. Three-dimensional marker trajectories and ground reaction forces (Motion Analysis, USA), and lower limbs’ muscle activities were measured (EMG, Noraxon USA). Knee cartilage and menisci geometries were obtained from subjects’ magnetic resonance images (3T, GE Health Care). An EMG-assisted musculoskeletal finite element modeling workflow was used to estimate knee cartilage tissue mechanics in walking trials. Knee cartilage and menisci were modeled using a transversely isotropic poroviscoelastic material model. Walking speed in SWS, 110%, and 120% of SWS were 1.38 m/s, 1.51 m/s, and 1.65 m/s for the young, and 1.21 m/s, 1.34 m/s and 1.46 m/s for the elderly, respectively. The maximum tensile stress in the elderly tibial cartilage was ~25%, ~33%, and ~32% lower than the young at SWS, 110%, and 120% of SWS, respectively. These preliminary results suggest that the cartilage in the elderly may not have enough stimulation even at 20% increases in walking speed, which may be one reason for tissue degeneration. To enhance these findings, further study with more subjects and different genders will investigate how age-related gait dynamics affects knee biomechanics. Acknowledgments: Australian NHMRC Ideas Grant (APP2001734), KITECH (JE220006)

Tendinopathy is the most frequent musculoskeletal disease that requires medical attention. Mechanical overload has been considered as a key driver of its pathology. However, the underline mechanism on how overload induces tendinopathy and inflammation is unclear. Extracellular mitochondria (EM) are newly identified as cell-to-cell communicators. The aim of this study is to elucidate the role of mitochondria in overload-induced inflammation. We performed three-dimensional uniaxial stretching to mouse tendon organoid in bioreactors. Cyclic strain of uniaxial loadings included underload, normal load, and overload, according to previous work. We then harvested microvesicles including EM, from the bioreactor by differential centrifugation and evaluated their characteristics by flow cytometry and super-resolution confocal microscopy. Raw 264.7 mouse macrophage cell line was used for chemotaxis assay in a Boyden Chamber System with Magnetic-Activated Cell Sorting Technology. EM induced cytokines secretion by macrophages was analyzed by a bead-based multiplex assay panel. N-Acetyl-L-cysteine (NAC) was used as the antioxidant to tendon organoid to regulate mitochondrial fitness. We showed mechanical load induced tendon organoid to release microvesicles including mitochondria. The size of microvesicles is mainly in the range from 220nm to 880nm. More than 75% of microvesicles could be stained by PKH26, confirming they were with lipophilic membrane. Super-resolution confocal microscopy identified two forms of mitochondria, including mitochondria encapsulated in vesicles and free mitochondria. Overload led to the degeneration of the organoid and induced microvesicles release containing most EM. Chemotaxis assay showed that EM from overloaded tendon organoid induced macrophages chemotaxis. In addition, microvesicles extracted from overloaded tendon organoid induced the production of proinflammatory cytokines including IL-6, KC (Keratinocyte-Derived Chemokine) and IL-18. NAC treatment to tendon cells could attenuate overload-induced macrophage chemotaxis. Overload induces EM releasing from tendon cells, which leads to chemotaxis of macrophages toward tendon, resulting in induction of inflammation