An increased number of neutrophils (NEUs) has long been associated with infections in the knee joints; their contribution to knee osteoarthritis (KOA) pathophysiology remains largely unexplored. This study aimed to compare the phenotypic and functional characteristics of synovial fluid (SF)-derived NEUs in KOA and knee infection (INF). Flow cytometric analysis, protein level measurements (ELISA), NEU oxidative burst assays, detection of NEU phagocytosis (pHrodo. TM. Green Zymosan Biparticles. TM. Conjugate for Phagocytosis), morphological analysis of the SF-derived/synovial tissue NEUs, and cultivation of human umbilical vein endothelial cells (HUVECs) using SF supernatant were used to characterise NEUs functionally/morphologically. Results: Compared with INF NEUs, KOA NEUs were characterised by a lower expression of CD11b, CD54 and CD64, a higher expression of CD62L, TLR2 and TLR4, and lower production of inflammatory mediators and proteases, except CCL2. Functionally, KOA NEUs displayed an increased production of radical oxygen species and phagocytic activity compared with INF NEUs. Morphologically, KOA and INF cells displayed different cell sizes and morphology, histological characteristics of the surrounding synovial tissues and influence on endothelial cells. KOA NEUs were further subdivided into two groups: SF containing <10% and SF with 10%–60% of NEUs. Analyses of two KOA NEU subgroups revealed that NEUs with SF <10% were characterised by 1) higher CD54, CD64, TLR2 and TLR4 expression on their surface; 2) higher concentrations of TNF-α, sTREM-1, VILIP-1, IL-1RA and MMP-9 in SFs. Our findings reveal a key role for NEUs in the pathophysiology of KOA, indicating that these cells are morphologically and functionally different from INF NEUs. Further studies should explore the mechanisms that contribute to the increased number of NEUs and their crosstalk with other immune cells in KOA. This study was supported by the Ministry of Health of the Czech Republic (NU20-06-00269; NU21-06-00370)

In approximately 20 years, surgical treatment of femoro-acetabular impingement (FAI) has been widely accepted, and its indications refined. However, the current approach of the disease prevents a good understanding of its pathophysiology, and numerous uncertainties remain. Comprehending inter-individual spine-hip relations (SHRs) can further clarify the pathophysiology of impingement, and explain occasional surprising mismatch between clinical assessment and imaging or intraoperative findings. The rational is simple, the more the spino-pelvic complex is mobile (sagittal ROM) and the more the hip is protected against hip impingement but would probably become at risk of spine-hip syndrome if the spino-pelvic complex comes to degenerate. Grouping patients based on their spine-hip relation can help predict and diagnose hip impingement, and assess the relevance of physiotherapy. With the proposed new classification of FAIs, every patient can be classified in homogeneous groups of complexity of treatment. The primary aim of this paper is to raise awareness of the potential impact that the spine-hip relations have on the hip impingement disease. Two new classifications are proposed, for FAIs and SHRs that can help surgeons in their comprehension, and could be beneficial in clinical and research areas

Introduction and Objective

Intervertebral disc (IVD) degeneration is one of the major contributors to low back pain, the leading cause of disability worldwide. This multifactorial pathological process involves the degradation of the extracellular matrix, inflammation, and cell loss due to apoptosis and senescence. While the deterioration of the extracellular matrix and cell loss lead to structural collapse of the IVD, increased levels of inflammation result in innervation and the development of pain. Amongst the known regulators of inflammation, toll-like receptors (TLRs) and more specifically TLR-2 have been shown to be specifically relevant in IVD degeneration. As strong post-transcriptional regulators, microRNAs (miRNAs) and their dysregulation has been connected to multiple pathologies, including degenerative diseases such as osteoarthritis and IVD degeneration. However, the role of miRNAs in TLR signalling in the IVD is still poorly understood and was hence investigated in this study.

The paramount importance of synovial fluid in lubrication and protection of articular joints has long been recognized. Synovial fluid, a dialysate of plasma, forms an interface with both the synovium and cartilage and plays a crucial role in joint lubrication and bearing functions. In an osteoarthritic joint, damage to the articular cartilage causes modifications in the rheological properties of synovial fluid and, reducing the viscoelasticity and increasing the friction between articular surfaces. Viscosupplementation is a treatment for osteoarthritis that uses hyaluronic acid as a (visco)supplement to the diseased joint. The aim of this treatment is to restore the rheological properties of synovial fluid. Osteoarthritis is the most common disease affecting the joints in human population and among the most important causes of pain, disability and economic loss. Therefore, innovative methods are needed to more effectively treat osteoarthritis, directly addressing the disease process. Among various locomotor mechanisms that could serve to illustrate the integrated nature of functional morphology, perhaps none is more complex than the equine locomotor system.

Confronting the need for evaluating the current methods to control joint disease, the horse provides an excellent animal model. As it suffers similar clinical manifestations to those seen in human, it may provide tentative biomedical extrapolations.

Vascular inflammation and activation of myofibroblasts are significant contributors to the progression of fibrosis, which can severely impair tissue function. In various tissues, including tendons, Transforming growth factor beta 1 (TGF-β1) has been identified as a critical driver of adhesion and scar formation. Nevertheless, the mechanisms that underlie fibrotic peritendinous adhesions are still not well comprehended, and human microphysiological systems to help identify effective therapies remain scarce. To address this issue, we developed a novel human Tendon-on-a-Chip (hToC), comprised of an endothelialized vascular compartment harboring circulating monocytes and separated by a 5 μm/100 nm dual-scale ultrathin porous membrane from a type I/III collagen hydrogel with primary tendon fibroblasts and tissue-resident macrophages, all under defined serum-free conditions. The hToC models the crosstalk of the various cells in the system leading to the induction of inflammatory and fibrotic pathways including the activation of mTOR signaling. Consistent with phenotypes observed in vivo in mouse models and clinical human samples, we observed myofibroblast differentiation and senescence, tissue contraction, excessive extracellular matrix deposition, and monocytes’ transmigration and macrophages’ secretion of inflammatory cytokines, which were dependent on the presence of the endothelial barrier. This model offers novel insights on the role of vasculature in the pathophysiology of adhesions, which were previously underappreciated. Moreover, in testing whether the hToC could be used to evaluate efficacy of therapeutics, we were able to capture donor-specific variability in the response to Rapamycin treatment, which reduced myofibroblast activation regardless. Thus, our findings demonstrate the value of the hToC as a human microphysiological system for investigating the pathophysiology of fibrotic conditions in the context of peritendinous injury and similar fibrotic conditions, providing an alternative to animal testing

Imaging can provide valuable information about the function of tissues and organs. The capacity for detecting and measuring imaging biomarkers of biological activities, allows for a better understanding of the pathophysiology of any process in the human body, including the musculoskeletal system. This is of particular importance in oncologic, metabolic and rheumatologic diseases, but not limited to these. In the domain of the musculoskeletal system, functional imaging also means to be able to address biomechanical evaluations. Weight-bearing imaging and dynamic studies have a prominent role. All imaging techniques (X-rays, CT, MR, ultrasound) are in demand, and offer different applications, specific equipment and novel methods for addressing this. Functional imaging is also essential to drive minimally invasive treatments – i.e. interventional radiology, and new treatment approaches move together with the advances on imaging guidance methods. On both the diagnostic and the interventional side, the increasing availability of dedicated equipment and the development of specific imaging methods and protocols greatly helps the transition from research to clinical practice

The pathophysiological basis of alterations in trabecular bone of patients with osteonecrosis of the femoral head (ONFH) remains unclear. ONFH has classically been considered a vascular disease with secondary changes in the subchondral bone. However, there is increasing evidence suggesting that ONFH could be a bone disease, since alterations in the functionality of bone tissue distant from the necrotic lesion have been observed. We comparatively studied the transcriptomic profile of trabecular bone obtained from the intertrochanteric region of patients with ONFH without an obvious aetiological factor, and patients with osteoarthritis (OA) undergoing total hip replacement in our Institution. To explore the biological processes that could be affected by ONFH, we compared the transcriptomic profile of trabecular bone from the intertrochanteric region and the femoral head of patients affected by this condition. Differential gene expression was studied using an Affymetrix microarray platform. Transcriptome analysis showed a differential signature in trabecular bone from the intertrochanteric region between patients with ONFH and those with OA. The gene ontology analyses of the genes overexpressed in bone tissue of patients with ONFH revealed a range of enriched biological processes related to cell adhesion and migration and angiogenesis. In contrast, most downregulated transcripts were involved in cell division. Trabecular bone in the intertrochanteric region and in the femoral head also exhibited a differential expression profile. Among the genes differentially expressed, we highlighted those related with cytokine production and immune response. This study identified a set of differently expressed genes in trabecular bone of patients with idiopathic ONFH, which might underlie the pathophysiology of this condition. Acknowledgements: This work was supported by grants PI18/00643 and PI22/00939 from ISCIII-FEDER, Ministerio de Ciencia, Innovación y Universidades (MICINN)-AES

In the past decades, a huge amount of effort has been devoted to translate evidence based on standard preclinical models of bone tumours to effective tools for clinical applications. Although cancer is a genetic disease, hence the emphasis on -omics approaches, the complexity of cancer tissue, a mix of competing clones of transformed elements that react differently to microenvironmental stimuli, may hardly be reproduced by standard approaches. Cost, biological differences and ethical concerns are increasingly recognized as weaknessess of animal models. To overcome these limitations and provide reliable, reproducible, and affordable tools for predicting the effectiveness of treatments, environmental-controlled 3D cultures and co-cultures (spheroids, organoids) coupled with microfluidics and advanced imaging have recently being considered as effective instrument to increase knowledge on the pathophysiology of bone tumours and define effective therapeutic solutions

Breast cancer is the most frequent malignancy in women with an estimation of 2.1 million new diagnoses in 2018. Even though primary tumours are usually efficiently removed by surgery, 20–40% of patients will develop metastases in distant organs. Bone is one of the most frequent site of metastases from advanced breast cancer, accounting from 55 to 58% of all metastases. Currently, none of the therapeutic strategies used to manage breast cancer bone metastasis are really curative. Tailoring a suitable model to study and evaluate the disease pathophysiology and novel advanced therapies is one of the major challenges that will predict more effectively and efficiently the clinical response. Preclinical traditional models have been largely used as they can provide standardization and simplicity, moreover, further advancements have been made with 3D cultures, by spheroids and artificial matrices, patient derived xenografts and microfluidics. Despite these models recapitulate numerous aspects of tumour complexity, they do not completely mimic the clinical native microenvironment. Thus, to fulfil this need, in our study we developed a new, advanced and alternative model of human breast cancer bone metastasis as potential biologic assay for cancer research. The study involved breast cancer bone metastasis samples obtained from three female patients undergoing wide spinal decompression and stabilization through a posterior approach. Samples were cultured in a TubeSpin Bioreactor on a rolling apparatus under hypoxic conditions at time 0 and for up to 40 days and evaluated for viability by the Alamar Blue test, gene expression profile, histology and immunohistochemistry. Results showed the maintenance and preservation, at time 0 and after 40 days of culture, of the tissue viability, biological activity, as well as molecular markers, i.e. several key genes involved in the complex interactions between the tumour cells and bone able to drive cancer progression, cancer aggressiveness and metastasis to bone. A good tis sue morphological and microarchitectural preservation with the presence of lacunar osteolysis, fragmented trabeculae locally surrounded by osteoclast cells and malignant cells and an intense infiltration by tumour cells in bone marrow compartment in all examined samples. Histomorphometrical data on the levels of bone resorption and bone apposition parameters remained constant between T0 and T40 for all analysed patients. Additionally, immunohistochemistry showed homogeneous expression and location of CDH1, CDH2, KRT8, KRT18, Ki67, CASP3, ESR1, CD8 and CD68 between T0 and T40, thus further confirming the invasive behaviour of breast cancer cells and indicating the maintaining of the metastatic microenvironment. The novel tissue culture, set-up in this study, has significant advantages in comparison to the pre-existent 3D models: the tumour environment is the same of the clinical scenario, including all cell types as well as the native extracellular matrix; it can be quickly set-up employing only small samples of breast cancer bone metastasis tissue in a simple, ethically correct and cost-effective manner; it bypasses and/or decreases the necessity to use more complex preclinical model, thus reducing the ethical burden following the guiding principles aimed at replacing/reducing/refining (3R) animal use and their suffering for scientific purposes; it can allow the study of the interactions within the breast cancer bone metastasis tissue over a relatively long period of up to 40 days, preserving the tumour morphology and architecture and allowing also the evaluation of different biological factors, parameters and activities. Therefore, the study provides for the first time the feasibility and rationale for the use of a human-derived advanced alternative model for cancer research and testing of drugs and innovative strategies, taking into account patient individual characteristics and specific tumour subtypes so predicting patient specific responses

OA pathophysiology has a vascular component consisting of venous stasis resulting in intraosseous hypertension and hypoxia. In response, osteoblasts change their cytokine expression, accelerating bone remodelling and cartilage breakdown consistent with OA. We have characterized circulatory kinetics in OA bone in animal models with dynamic contrast enhanced MRI (DCE-MRI) and . 18. F PET and have demonstrated venous stasis and reduced perfusion that temporally precede and spatially coincide with OA lesions. Osteoblast uptake of . 18. F is consistent with abnormal perfusion, bone remodelling, and severity of OA. Circulatory kinetics with DCE-MRI in humans with OA of the knee exhibit similar venous outflow obstruction. Venous stasis is associated with hypoxia in subchondral bone. As an example of the effects of hypoxia on OA osteoblasts, we have described upregulation of fibrinolytic peptides, but a deficiency in the upregulation of PAI-1, leading to the generation of plasmin by human OA osteoblasts exposed to hypoxia in vitro. Plasmin is a serine protease that has been shown to degrade cartilage in OA. Abnormal circulatory kinetics by DCE-MRI may be an imaging biomarker of OA. Pharmacologic modulation of venous stasis would have a salutary effect on the physicochemical microcirculation of subchondral osteoblasts and the pathophysiology of OA

While knee osteoarthritis (OA) is now recognized as a complex disease affecting the whole joint, not just the cartilages, there remains a paucity of data regarding the interactions between knee components. One relationship of particular interest is between the spatial variations in cartilage thickness (CTh) and subchondral bone mineral density (BMD). Indeed, bone and cartilage are two mechanosensitive tissues that interact as a functional unit and there is evidence of a biomechanical coupling between both tissues. Particularly, a recent in vivo study has shown a positive relationship in non-OA knees with thicker cartilage where bone is denser, and an alteration of this relationship in OA knees. These observations support the concept of an osteochondral unit and warrant additional research to assess the influence of bone depth. Therefore, this study aimed to characterize the relationship between spatial variations in CTh and BMD measured at various depths below the bone surface. CT-arthrography of 20 non-OA tibias and 20 severe medial-compartment OA tibias were segmented to build 3D mesh models of the bones and cartilages. Each individual tibia model was registered to a reference tibia, allowing to calculate BMD maps at 1, 3, 5 and 10mm below the bone-cartilage interface in the medial compartment. Pearson correlations between CTh maps and the four BMD maps were then calculated for each knee. Lastly, differences in correlation coefficients between successive bone layers were assessed using Wilcoxon signed-rank tests. In both OA and non-OA tibias, the correlation coefficients were higher with the BMD measured in the 1mm layer, and followed a pattern of statistically significant decrease with bone layers of increasing depth (p < 0.021). In non-OA tibias, the median relationship was positive with a strong effect size in the 1, 3 and 5mm layers, while in OA tibias the median relationship was positive only in the 1mm layer and with a medium effect size. In the OA tibias, the median relationship was negative with a weak effect size in the 3 and 5mm layers, and it was negative with a medium effect size in the 10mm layer. In conclusion, the results of the present study support the value of considering bone and cartilage as a unit, and more generally support OA pathophysiology models based on relationships among knee properties

Spinal cord injury (SCI) is a devastating disorder for which the identification of exacerbating factors is urgently needed. Although age, blood pressure and infection are each considered to be prognostic factors in patients with SCI, exacerbating factors that are amenable to treatment remain to be elucidated. Microglial cells, the resident immune cell in the CNS, form the first line of defense after being stimulated by exposure to invading pathogens or tissue injury. Immediately after SCI, activated microglia enhance and propagate the subsequent inflammatory response by expressing cytokines, such as TNF-α, IL-6 and IL-1β. Recently, we demonstrated that the activation of microglia is associated with the neuropathological outcomes of SCI. Although the precise mechanisms of microglial activation remain elusive, several basic research studies have reported that hyperglycemia is involved in the activation of resident monocytic cells, including microglia. Because microglial activation is associated with secondary injury after SCI, we hypothesized that hyperglycemia may also influence the pathophysiology of SCI by altering microglial responses. The mice were anesthetized with pentobarbital (75 mg/kg i.p.) and were subjected to a contusion injury (70 kdyn) at the 10th thoracic level using an Infinite Horizons Impactor (Precision Systems Instrumentation). For flow cytometry, the samples were stained with the antibodiesand analyzed using a FACS Aria II flow cytometer and the FACSDiva software program (BD Biosciences). We retrospectively identified 528 SCI patients admitted to the Department of Orthopaedic Surgery at the Spinal Injuries Center (Fukuoka, Japan) between June 2005 and May 2011. The patients' data were obtained from their charts. We demonstrate that transient hyperglycemia during acute SCI is a detrimental factor that impairs functional improvement in mice and human patients after acute SCI. Under hyperglycemic conditions, both in vivo and in vitro, inflammation was enhanced through promotion of the nuclear translocation of the nuclear factor kB (NF-kB) transcription factor in microglial cells. During acute SCI, hyperglycemic mice exhibited progressive neural damage, with more severe motor deficits than those observed in normoglycemic mice. Consistent with the animal study findings, a Pearson χ2 analysis of data for 528 patients with SCI indicated that hyperglycemia on admission (glucose concentration ≥126 mg/dl) was a significant risk predictor of poor functional outcome. Moreover, a multiple linear regression analysis showed hyperglycemia at admission to be a powerful independent risk factor for a poor motor outcome, even after excluding patients with diabetes mellitus with chronic hyperglycemia (regression coefficient, −1.37; 95% confidence interval, −2.65 to −0.10; P < 0.05). Manipulating blood glucose during acute SCI in hyperglycemic mice rescued the exacerbation of pathophysiology and improved motor functional outcomes. Our findings suggest that hyperglycemia during acute SCI may be a useful prognostic factor with a negative impact on motor function, highlighting the importance of achieving tight glycemic control after central nervous system injury

Human in vitro models of the neuromuscular junction (NMJ) are currently moving from embryonic stem cells to induced Pluripotent Stem Cells (iPSCs). With this, a robust model could be optimised for physiology and pathophysiology studies, as well as representing a drug screening platform. For this reason, the work presented here represents the optimisation of a human co-culture model of skeletal muscle (hSkM)/ iPSC-derived motor neurons (MNs) both in monolayer and in 3D tissue engineering collagen constructs. Firstly, human iPSC-derived motor neurons (MNs) were characterised over a period of 35 days to test their cholinergic potential. Then, primary human skeletal muscle (hSkM) and MNs were co-cultured on different substrates (gelatin and SureBond+ReadySet (Axol Bioscience)) and differentiated in various combinations of media to allow both myotube formation and neurite extension. Morphological (β-III Tubulin and Rhodamine Phalloidin) and interaction (α-Bungarotoxin and Synaptic Vesicle 2) immunofluorescent stainings were used to evaluate cell differentiation and co-localisation of pre and post-synaptic markers. Results from this study showed that the MNs presented a cholinergic phenotype up to 21 days; hSkM and MNs co-existed in culture and differentiated in neuronal Maintenance Medium (MM, Axol Bioscience); the 3D constructs allowed alignment and maturation of the muscle tissue, while providing a matrix for neurite extension and NMJ formation. This model has the potential to become a valid tool for in vitro drug screening while reducing the use of animals in research and providing the scientific community with a platform for personalised medicine

Appropriate in vivo models can be used to understand atrophic non-union pathophysiology. In these models, X-ray assessment is essential and a reliable good quality images are vital in order to detect any hidden callus formation or deficiency. However, the radiographic results are often variable and highly dependent on rotation and positioning from the detector/film. Therefore, standardised A-P and lateral x-ray views are essential for providing a full radiological picture and for reliably assessing the degree of fracture union. We established and evaluated a method for standardised imaging of the lower limb and for reliably obtaining two perpendicular views (e.g. true A-P and true lateral views). The normal position of fibula in murine models is posterolateral to the tibia, therefore, a proper technique must show fibula in both views. In order to obtain the correct position, the knee joint and ankle joints were flexed to 90 degrees and the foot was placed in a perpendicular direction with the x-ray film. To achieve this, a leg holder was made and used to hold the foot and the knee while the body was in the supine position. Lateral views were obtained by putting the foot parallel to the x-ray film. Adult Wister rat cadavers were used and serial x-rays were taken. A-P view in supine position showed the upper part of the fibula clearly, however, there was an unavoidable degree of external rotation in the whole lower limb, and the lower part of the fibula appeared behind the tibia. Therefore, a true A-P view whilst the body was in the supine position was difficult. To overcome this, a P-A view of the leg was performed with the body prone position, this allowed both upper and lower parts of the fibula to appear clearly in both views. This method provides two true perpendicular views (P-A and lateral) and helped to optimise radiological assessment

Complex pathophysiologies involve different signalling mechanisms, with a multitude of often interconnected potential therapeutic targets. Therefore, there is a need for the development of multi-compartment delivery vehicles for combinatorial and synergistic therapeutic approaches. In this study it was hypothesized that multi-compartment crosslinked collagen type I systems can deliver multiple bioactive agents in a controlled manner in an in vitro model condition of skin fibrosis. Multi-compartment collagen-based systems were made using solutions of dialyzed type I collagen mixed with 10× PBS, after which they were neutralised and crosslinked with 1 and 2.0 mM 4 arm-succinimidyl glutarate ester PEG (4 arm-PEG-SG), respectively, followed by incubation at 37ºC. The systems were characterised through swelling assessment, collagenase degradation assay and compression tests. The release of encapsulated drugs from the hydrogels was studied by ELISA and the effect of the delivered bioactive agents was assessed through imaging and quantification for fibrotic markers in an in vitro model. A pilot study using FITC-dextran proved that the inner compartment was capable of promoting a sustained release over a long period of time (7 days), which was further confirmed with drug release assays using a TNF-α antagonist and recombinant decorin, fitting the intended therapeutic release profile. Protein expression studies showed a decrease of endogenous collagen type I and α-smooth muscle actin expression (p<0.05) indicating amelioration of fibrosis. In summary, this indicates that this system is suitable for dual delivery of multiple bioactive agents, resulting in a controlled release in vitro and illustrating its potential in therapy

Dynamic loading is necessary for the preservation of native cartilage, but mechanical disuse is one major risk factor for osteoarthritis (OA). As post-transcriptional regulators, microRNAs (miRs) represent promising molecules to quickly adjust the cellular transcriptome in a stimulus-dependent manner. Several miR clusters were related to skeletal development, joint homeostasis and OA pathophysiology but whether miRs are associated with mechanosensitivity and regulated by mechanotransduction is so far unknown. We aimed to investigate the influence of mechanical loading on miR expression and to identify mechanosensitive miR clusters characteristic for non-beneficial loading regimes which may serve as future tools for improved diagnosis or intervention during OA development. Loading regimes leading to an anabolic or catabolic chondrocyte response were established based on an increase or decrease of proteoglycan synthesis after loading of human engineered cartilage. miR microarray profiling at termination of loading revealed only small changes of miR expression (7 significantly upregulated miRs) by an anabolic loading protocol while catabolic stimulation produced a significant regulation of 80 miRs with a clear separation of control and compressed samples by hierarchical clustering. Overall regulation of 8/14 miR was confirmed by qRT-PCR with mean amplitudes of up to 2.5-fold for catabolic loading. Cross-testing revealed that 2 miRs were upregulated by both loading conditions and 6 were specifically elevated by the catabolic loading regime. Conclusively, this study defines the first mechanosensitive miR cluster associated with non-beneficial compressive cyclic loading of human engineered cartilage which can now be tested for its diagnostic potential in healthy versus OA-affected human cartilage

Synovitis has been shown to play a role in pathophysiology of OA promoting cartilage destruction and pain. Synovium is mainly composed of synovial fibroblast (SF) and macrophage (SM) that guide synovial inflammation. Adipose stromal cells (ASC) promising candidate for cell therapy in OA are able to counteract inflammation. Two different subsets of macrophages have been described showing a pro-inflammatory (M1) and an anti-inflammatory (M2) phenotype. Macrophage markers: CD68, CD80 (M1-like) and CD206 (M2-like) were evaluated in osteoarthritic synovial tissue. GMP-clinical grade ASC were isolated from subcutaneous adipose tissue and M1-macrophages were differentiated from CD14+ obtained from peripheral blood of healthy donors. ASC were co-cultured in direct and indirect contact with activated (GM-CSF+IFNγ)-M1 macrophages for 48h. At the end of this co-culture we analyzed IL1β, TNFα, IL6, MIP1α/CCL3, S100A8, S100A9, IL10, CD163 and CD206 by qRT-PCR or immunoassay. PGE2 blocking experiments were performed. In moderate grade OA synovium we found similar percentages of CD80 and CD206. M1-activated macrophage factors IL1β, TNFα, IL6, MIP1α/CCL3, S100A8 and S100A9 were down-modulated both co-culture conditions. Moreover, ASC induced the typical M2 macrophage markers IL10, CD163 and CD206. Blocking experiments showed that TNFα, IL6, IL10, CD163 and CD206 were significantly modulated by PGE2. We confirmed the involvement of PGE2/COX2 also in CD14+ OA synovial macrophages. In conclusion we demonstrated that ASC are responsible for the switching of activated-M1-like to a M2-like anti-inflammatory phenotype, mainly through PGE2. This suggested a specific role of ASC as important determinants in therapeutic dampening of synovial inflammation in OA

Ligaments and tendons are vital musculoskeletal soft tissues, which are commonly injured due to overuse and trauma. Their distinct functions are well known however their unique structure and biochemical composition and how they change with disease is poorly described. The most commonly injured ligament in the dog and man is the cranial cruciate (CCL) and anterior cruciate ligament (ACL) respectively. Therefore, the structure, function and pathophysiology of disease of this ligament has been most commonly studied in both species. Canine cranial cruciate ligament rupture (CCLR) most commonly occurs following gradual ligament degeneration or disease (CCLD) followed by a non-contact injury or a minor trauma. Several studies have described marked degenerative histological changes in ligament structure prior to and following rupture which consist of loss of the collagen fascicular structure, areas of poor collagen fibril staining, a marked increase in “chondroid” type cells and mineralisation. The ECM protein profile is also altered with increased sulphated glycosaminoglycans content, increased immature collagen cross-links as well as enzymes involved in collagen remodelling. In man, similar findings have been described in the ACL with age and in osteoarthritis (OA). Previously it had been thought that ligament degeneration occurred following OA but these more recent studies suggest that ligament degeneration can lead to joint destabilisation and OA. Being able to determine early degenerative ligament changes in spontaneous clinical cohorts and the mechanisms which cause them are ideal starting points to determine targets for future therapies in the prevention of ligament degradation and rupture. Further identification of ligament cell types in terms of degenerative, responsive and regenerative (stem) types is essential to try and alter ligament cellular and extracellular matrices harnessing their therapeutic potential

Confirming clinical evidence, we recently demonstrated in a rodent model that a severe trauma which induces an acute systemic inflammation considerably impairs fracture healing. Interleukin-6 (IL-6) is a key cytokine in posttraumatic inflammation as its serum level correlates with injury severity and mortality. IL-6 signals are transmitted by the transmembrane glycoprotein 130 (gp130) via two distinct mechanisms: firstly, through classic signalling via the membrane-anchored IL-6 receptor and secondly, through trans-signalling using a soluble IL-6 receptor. Whereas IL-6 trans-signalling is considered a danger signal driving inflammation, classic signalling may mediate anti-inflammatory, pro-regenerative processes. The role of the two distinct pathways in bone healing has not yet been elucidated. Here, we studied the function of IL-6 in the pathophysiology of compromised bone healing induced by severe trauma. Male C57BL/6J mice received an osteotomy of the right femur stabilized with an external fixator. Systemic inflammation was induced by additional blunt chest trauma (TxT) applied immediately after the osteotomy. Mice were injected with either fusion protein sgp130Fc, which selectively inhibits IL-6 trans-signalling, or a neutralizing anti-IL-6 antibody (IL-6 Ab), blocking both signalling pathways. Control mice received vehicle solution. Animals were euthanised 21 days after surgery. Fracture healing was analysed by biomechanical testing, μCT, and histomorphometry (n= 6–9; p=0.05; ANOVA/Fisher LSD post hoc). Thoracic trauma significantly impaired fracture healing [bending stiffness (EI) −57%, p<0.00]. Treatment with sgp130Fc significantly attenuated bone regeneration as demonstrated by an increased EI (+110%, p<0.00) and a trend of augmented apparent Young”s modulus (+69%, p=0.13) compared to TxT control. Histomorphometric analysis could not detect differences in the amount of bone, confirming µCT results, but revealed a significantly decreased cartilage area after treatment with sgp130Fc (−76%, p=0.01). Inhibition of both signalling pathways with IL-6 Ab, however, did not have any effects. In conclusion, severe trauma significantly impaired fracture healing, confirming previous studies. Treatment with sgp130Fc ameliorated the negative effects providing evidence that IL-6 trans-signalling triggers the excessive immune response after trauma impairing bone regeneration. Injection of IL-6 Ab did not improve fracture healing thereby implying that classic signalling may rather have beneficial effects

In vivo animal experimentation has been one of the cornerstones of biological and biomedical research, particularly in the field of clinical medicine and pharmaceuticals. The conventional in vivo model system is invariably associated with high production costs and strict ethical considerations. These limitations led to the evolution of an ex vivo model system which partially or completely surmounted some of the constraints faced in an in vivo model system. The ex vivo rodent bone culture system has been used to elucidate the understanding of skeletal physiology and pathophysiology for more than 90 years. This review attempts to provide a brief summary of the historical evolution of the rodent bone culture system with emphasis on the strengths and limitations of the model. It encompasses the frequency of use of rats and mice for ex vivo bone studies, nutritional requirements in ex vivo bone growth and emerging developments and technologies. This compilation of information could assist researchers in the field of regenerative medicine and bone tissue engineering towards a better understanding of skeletal growth and development for application in general clinical medicine. Cite this article: A. A. Abubakar, M. M. Noordin, T. I. Azmi, U. Kaka, M. Y. Loqman. The use of rats and mice as animal models in ex vivo bone growth and development studies. Bone Joint Res 2016;5:610–618. DOI: 10.1302/2046-3758.512.BJR-2016-0102.R2