Summary Statement. A single, locally-delivered injection of a human placental product containing multipotent stromal cells reduced severity of infection in an immunosuppressed murine osteomyelitis model and eliminated infection in 25% of animals compared with 0% of controls without the use of antibiotics. Introduction. Implant–associated osteomyelitis is a serious orthopaedic condition and is particularly difficult to treat in immunosuppressed individuals. Despite great advancement in the field of biomaterials and pharmaceuticals, emerging patterns of antibiotic resistance, complex biofilm production and penetration of therapeutic concentrations of effective antibiotics into bone continue to represent unmet clinical challenges. The promise of adult multipotent stromal cells (MSCs) for tissue regeneration has been of intense interest in recent years. Among their many potential therapeutic uses, MSCs have also been shown to have direct antimicrobial properties. The objective of this study was to evaluate the efficacy of a locally–delivered human placental-based tissue product containing multipotent stromal cells (hAmSC) to reduce the severity of implant-associated Staphylococcus aureus osteomyelitis in an immunosuppressed murine model. We hypothesised that athymic mice with implant-associated osteomyelitis would have diminished infection following treatment with hAmSC as evidenced by decreased bioluminescence intensity and lower histologic scores for infection and bacterial load when compared to saline-treated controls. Methods. An athymic murine model of chronic implant-associated osteomyelitis was developed using luciferase-transfected Staphylococcus aureus to study the antimicrobial effects of a human placental-based product containing multi-potent stromal cells (hAmSC). Sixteen athymic mice had osteomyelitis established in the right femoral diaphysis. Fifteen days after inducing luc S. aureus osteomyelitis, the mice were randomised to receive a single 0.5 cc injection of hAmSC (n=8) or vehicle (0.9% saline) (n=8) into the soft tissues immediately adjacent to the infected bone. No antibiotics were administered throughout the duration of the study. Mice were imaged with an In Vivo Imaging System (IVIS 1000, PerkinElmer) twice weekly for 30 days to assess change in bioluminescence intensity from baseline immediately prior to treatment with either hAmSC or saline. Radiographs were obtained at days −10, 0, 10, 20 and 30 days post-injection and scored for bone changes secondary to osteomyelitis by a reviewer blinded to treatment group. Mice were sacrificed 30 days after treatment and femurs were examined histologically and scored for bacterial load and degree of inflammation by a pathologist blinded to treatment group. Results. Osteomyelitis was successfully established in all mice as evidenced by baseline bioluminescence imaging and radiographs. Mean bioluminescence intensity decreased from baseline in animals receiving hAmSC and remained below baseline for 28 days, whereas vehicle-treated animals showed an increase in mean bioluminescence intensity throughout the study period. Osteomyelitis resolved in 2/8 hAmSC-treated animals and 0/8 vehicle-treated animals as evidenced by bioluminescence imaging and histological examination for bacteria/inflammation at sacrifice. Radiograph scores for secondary bone changes were lower in mice treated with hAmSC than vehicle at 10, 20 and 30 days post injection. Median inflammatory score was lower in the hAmSC-treated mice than vehicle treated controls. Conclusions. A single injection of hAmSC was effective at reducing the severity of S. aureus infection without the use of antibiotics in this chronic implant associated osteomyelitis immunosuppressed murine model. In addition to reduced bioluminescence intensity below baseline for 28 days during the study period, infection was eliminated in 25% of animals in the hAmSC-treated group

Purpose. In patients with multiple trauma delayed fracture healing is often diagnosed, but the pathomechanisms are not well known yet. The purpose of the study is to evaluate the effect of a severe hemorrhagic shock on fracture healing in a murine model. Methods. 10 male C57BL/6N mice per group (Fx, TH, THFx, Sham) and point in time were used. The Fx-group received an osteotomy after implantation of a fixateur extern. The TH-group got a pressure controlled hemorrhagic shock with a mean arterial blood pressure of 35 mmHg over 90 minutes. Resuscitation with 4 times the shed blood volume of Ringer solution was performed. The THFx group got both. Sham-animals received the implantation of a catheter and a fixateur extern but no blood loss or osteotomy. After 1, 2, 3, 4 or 6 weeks the animals were sacrificed. For the biomechanics the bones were analyzed via X-ray, µCT and underwent a 3-point bending test. The nondecalcified histology based on slices of Technovit 9100. The signaling pathway was analyzed via RT. 2. Profiler™ PCR Array Mouse Osteoporosis, Western Blot and Quantikine ELISA for RankL and OPG. Statistical significance was set at p < 0.05. Comparisons between groups were performed using the Mann–Whitney U (Fx vs. THFx) or Kruskal-Wallis Test (other groups). Results. The experiment showed that after 1 week the bones of the Fx- and THFx-mice were macroscopically instable. After 2 weeks the Fx-group showed macroscopically a stable bridging whereas the bones of the THFx-group were partly not stable bridged. 3 weeks after surgery the bones of both groups were stable bridged. Analysis via µCT showed that trauma hemorrhage leads to decreased density of the bone and callus and also to increased share of callus per bone volume after 2 weeks. The 3-point-bending test showed that the maximum bending moment is decreased in the group THFx compared to Fx after 2 weeks. The studies of the histology showed after 2 weeks a decrease in bone and cartilage after trauma-hemorrhage by optical analysis of photographs of the slices. The analyses of the signaling pathway pointed to an involvement of the RankL/Opg and IL6 pathway. Conclusion. A hemorrhagic shock has a negative effect on fracture healing in terms of reduced density of the bone and callus, increased share of callus per bone volume, decreased maximum bending moment, reduced mineralization of the callus and leads to changes in the RankL/Opg and IL6 pathways

Introduction

Osteoarthritis (OA) is a chronic degenerative disease of the entire joint leading to joint stiffness and pain (PMID:33571663). Recent evidence suggests that the sympathetic nervous system (SNS) plays a role in the pathogenesis of OA (PMID:34864169). A typical cause for long-term hyperactivity of the SNS is chronic stress. To study the contribution of increased sympathetic activity, we analyzed the progression of OA in chronically stressed mice.

Osteochondral injuries are a recognised factor in the development of osteoarthritis (OA). Mesenchymal stromal cells (MSCs) represent a promising biological therapeutic option as an OA-modifying treatment, and they also secrete factors that may have an anti-catabolic effect and/or encourage endogenous repair. We aim to study the effects of (i) intra-articular injection of human bone-marrow-derived MSCs and (ii) their secretome on recovery in a murine knee osteochondral injury model.

The MSC secretome was generated by stimulating human bone-marrow-derived MSCs with tumour necrosis factor alpha (TNFα). Mice (n=48) were injected with i) MSC secretome, ii) MSCs or iii) cell culture medium (control). Pain was assessed by activity monitoring, and cartilage repair, subchondral bone volume and synovial inflammation were evaluated using histology and microCT.

Both MSC- and MSC-secretome-injected mice showed significant pain reduction at day 7 when compared to control mice, but only the MSC-injected mice maintained a significant improvement over the controls at day 28. Cartilage repair was significantly improved in MSC-injected mice. No significant effects were observed with regards to synovial inflammation or subchondral bone volume.

The MSC secretome demonstrates regenerative effects but this does not appear to be as sustained as a MSC cell therapy. Further studies are required to investigate if this can be overcome using different dosing regiments for injection of the MSC secretome. As we further understand the regenerative properties of the MSC secretome, we may be able to enhance the clinical translatability of these therapies. Direct intra-articular injection of MSCs for the treatment of OA also appears promising as a potential future strategy for OA management.

Acknowledgements: MS is supported by a grant from the Wellcome Trust (PhD Programme for Clinicians)

Osteoarthritis (OA), the most common chronic degenerative joint disease, is characterized by inflammation, degradation of the articular cartilage and subchondral bone lesions, causing pain and decreased functionality.

NF-κB pathway is involved in OA and, in most cases, its activation depends on the phosphorylation and degradation of IκBα, the NF-κB endogenous inhibitor that sequesters NF-κB in the cytosol. Under inflammatory stimuli, IκBα is degraded by the IKK signalosome and NF-κB moves into the nucleus, inducing the transcription of inflammatory mediator genes and catabolic enzymes. The IKK signalosome includes IKKβ and IKKα kinases, the latter shown to be pivotal in the OA extracellular matrix derangement. The current OA therapies are not curative and nowadays, the preclinical research is evaluating new structure-modifying pharmacological treatments, able to prevent or delay cartilage degradation.

N-acetyl phenylalanine derivative (NAPA), is a derivative of glucosamine, a constituent of the glycosaminoglycans of cartilage and a chondroprotective agent. Previous in vitro studies showed the ability of NAPA to increase cartilage components and to reduce inflammatory cytokines, inhibiting IKKα kinase activity and its nuclear migration.

The present study aims to further clarify the effect of NAPA in counteracting OA progression, in an in vivo mouse model after destabilization of the medial meniscus (DMM).

Mice were divided into 3 groups:

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DMM group: DMM surgery without NAPA;

DMM surgery was performed in the right knee, according to Glasson SS [2], while the left knee did not undergo any surgery. Four weeks after surgery (mild-to-moderate OA), some animals received one intra-articular injection of NAPA (2.5 mM) and after 2 weeks, the animals were pharmacologically euthanized. The mice of the 1^st group were euthanized 4 weeks after DMM and those of the 3^rd group after 6 weeks from their arrival in the animal facility. At the end of experimental times, both knee joints of the animals were analyzed through histology, histomorphometry, immunohistochemistry and subchondral bone microhardness.

The injection of NAPA significantly improved cartilage structure, increased cartilage thickness (p<0.0005), reduced Chambers and Mankin scores (p<0.005), fibrillation index (p<0.005) and decreased MMP13 (p<0.05) and ADAMTS5, MMP10, and IKKα (p<0.0005) staining. The microhardness measurements did not shown statistically significant differences between groups.

This study demonstrated the chondroprotective activities exerted by NAPA in vivo. NAPA markedly improved the physical structure of articular cartilage and reduced the amount of catabolic enzymes, and therefore of extracellular matrix remodeling. The reduction in OA grading and catabolic enzymes paralleled the reduction of IKKα expression. This further hints at a pivotal role of IKKα in OA development by regulating MMP activity through the control of procollagenase (MMP10) expression. We believe that the preliminary preclinical data, here presented, contribute to improve the knowledge on the development of disease modifying drugs since we showed the ability of NAPA of reverting the surgically induced OA in the widely accepted DMM model.

Chondrocytes are essential to the maintenance of articular cartilage and it is thought that chondrocyte death occurs early in septic arthritis. Understanding the causes of chondrocyte death will allow the development of chondroprotective strategies to improve long-term outcomes following septic arthritis. We utilised a murine model of septic arthritis using intra-articular injection of 10µL of a 107 concentration of S. aureus suspended in PBS. Seventy-five adult male C57/Bl6 mice were randomised to receive injection of either S. aurues 8325-4 (a wild-type of S. aurues capable of alpha toxin production), DU1090 (an isogenic mutant of 8325-4 that is identical to 8325-4 other than being incapable of producing alpha toxin) or a PBS control. Establishment of septic arthritis was confirmed through gait changes (5 mice/group), limb swelling and histological changes (10 mice/group). 10 animals from each group were sacrificed at 48 hours and the injected knee joints were dissected before being stained with CFMDA (labelling live chondrocytes green) and PI (labelling dead chondrocytes red). The samples were imaged using a confocal laser scanning microscope and the percentage of chondrocyte death was calculated. Mice injected with S. aureus 8325-4 or DU1090 developed septic arthritis with evidence of weight loss, limb swelling and gait changes whereas these were absent in the control group. There was a significantly higher level of chondrocyte death in the group infected with 8325-4 (2.7% chondrocyte viability) when compared to DU1090 (73.9% chondrocyte viability) and PBS injected mice (95% chondrocyte viability). One-Way ANOVA revealed that the difference between each group was statistically different (p < 0.05). Alpha toxin is the major damaging toxin in S. aurues septic arthritis. Any adverse effect of the immune system is negligible in comparison. Development of treatments counteracting the effect of alpha toxin is required

Chondrocytic activity is downregulated by compromised autophagy and mitochondrial dysfunction to accelerate the development of osteoarthritis (OA). Irisin is a cleaved form of fibronectin type III domain containing 5 (FNDC5) and known to regulate bone turnover and muscle homeostasis. However, little is known about the role of irisin in chondrocytes and the development of OA. This talk will shed light on FNDC5 expression by human articular chondrocytes and compare normal and osteoarthritic cells with respect to autophagosome marker LC3-II and oxidative DNA damage marker 8-hydroxydeoxyguanosine (8-OHdG). In chondrocytes in vitro, irisin improves IL-1β-mediated growth inhibition, loss of specific cartilage markers and glycosaminoglycan production. Irisin further suppressed Sirt3 and UCP- 1 to improve mitochondrial membrane potential, ATP production, and catalase. This attenuated IL-1β-mediated production of reactive oxygen species, mitochondrial fusion, mitophagy, and autophagosome formation. In a surgical murine model of destabilization of the medial meniscus (DMM) intra-articular administration of irisin alleviates symptoms like cartilage erosion and synovitis. Furthermore, gait profiles of the treated limbs improved. In chondrocytes, irisin treatment upregulates autophagy, 8-OHdG and apoptosis in cartilage of DMM limbs. Loss of FNDC5 in chondrocytes correlates with human knee OA and irisin repressed inflammation-mediated oxidative stress and deficient extracellular matrix synthesis through retaining mitochondrial biogenesis and autophagy. The talk sheds new light on the chondroprotective actions of this myokine and highlights the remedial effects of irisin during progression of OA

µCT images are commonly analysed to assess changes in bone density and architecture in preclinical murine models. Several platforms provide automated analysis of bone architecture parameters from volumetric regions of interest (ROI). However, segmentation of the regions of subchondral bone to create the volumetric ROIs remains a manual and time-consuming task. This study aimed to develop and evaluate automated pipelines for trabecular bone architecture analysis of mouse proximal tibia subchondral bone. A segmented dataset involving 62 knees (healthy and arthritic) from 10-week male C57BL/6 mice were used to train a U-Net type architecture, with µCT scans (downsampled) input that output segmentation and bone volume density (BV/TV) of the subchondral trabecular bone. Segmentations were upsampled and used in tandem with the original scans (10µ) as input for architecture analysis along with the thresholded trabecular bone. The analysis considered the manually and U-Net segmented ROIs using two available pipelines: the ITKBoneMorphometry library and CTan (SKYSCAN). The analyses included: bone volume (BV), total volume (TV), BV/TV, trabecular number (TbN), trabecular thickness (TbTh), trabecular separation (TbSp), and bone surface density (BSBV). There was good agreement for bone measures between the manual and U-Net pipelines utilizing ITK (R=0.88-0.98) and CTan (R=0.91-0.98). ITK and CTan showed good agreement for BV, TV, BV/TV, TbTh and BSBV (R=0.9-0.98). However, a limited agreement was seen between TbN (R=0.73) and TbSb (R=0.59) due to methodological differences in how spacing is evaluated. This U-Net/ITK pipeline seamlessly automated both segmentation and quantification of the proximal tibia subchondral bone. This automated pipeline allows the analysis of large volumes of data, and its open-source nature may enable the standardization of stereologic analysis of trabecular bone across different research groups

In osteoarthritis, chondrocytes acquire a hypertrophic phenotype that contributes to matrix degradation. Inflammation is proposed as trigger for the shift to a hypertrophic phenotype. Using in vitro culture of human chondrocytes and cartilage explants we could not find evidence for a role of inflammatory signalling activation. We found, however, that tissue repair macrophages may contribute to the onset of hypertrophy (doi: 10.1177/19476035211021907) Intra-articularly injected triamcinolone acetonide to inhibit inflammation in a murine model of collagenase-induced osteoarthritis, increased synovial macrophage numbers and osteophytosis, confirming the role of macrophages in chondrocyte hypertrophy occurring in osteophyte formation (doi: 10.1111/bph.15780). In search of targets to inhibit chondrocyte hypertrophy, we combined existing microarray data of different cartilage layers of murine growth plate and murine articular cartilage after induction of collagenase-induced osteoarthritis. We identified common differentially expressed genes and selected those known to be associated to inflammation. This revealed EPHA2, a tyrosine kinase receptor, as a new target. Using in silico, in vitro and in vivo models we demonstrated that inhibition of EPHA2 might be a promising treatment for osteoarthritis. Recently, single cell RNA-seq. has revealed detailed information about different populations of chondrocytes in articular cartilage during osteoarthritis. We re-analysed a published scRNA-seq data set of healthy and osteoarthritic cartilage to obtain the differentially expressed genes in the population of hypertrophic chondrocytes compared to the other chondrocytes, applied pathway analyses and then used drug databases to search for upstream inhibitors of these pathways. This drug repurposing approach led to the selection of 6 drugs that were screened and tested using several in vitro models with human chondrocytes and cartilage explants. In this lecture I will present this sequence of studies to highlight different approaches and models that can be used in the quest for a disease modifying drug for osteoarthritis

Intervertebral disc degeneration (IDD) is a major cause of low back pain, which affects 80% of the adult population at least once in their life. The pathophysiological conditions underlying IDD are still poorly understood. Genetic makeup, aging, smoking, physical inactivity and mechanical overloading, especially due to obesity, are among the strongest risk factors involved. Moreover, IDD is often associated with chronic inflammation within disc tissues, which increases matrix breakdown, glycosaminoglycan (GAG) loss and cell death. This micro-inflammatory environment is typical of several metabolic disorders, including diabetes mellitus (DM). As the etiopathogenesis of IDD in diabetic subjects remains scarcely understood, we hypothesised that this may be driven by a DM-induced inflammation leading to a combination of reduced GAG levels, decreased proteoglycan synthesis and increased matrix breakdown within the disc. The objective of the study was to investigate the pathogenesis of IDD in a murine model of type 1 DM (T1DM), namely non-obese diabetic (NOD) mouse. Total disc glycosaminoglycan (GAG) content, proteoglycan synthesis, aggrecan fragmentation mediated by matrix metalloproteinases (MMPs) and a Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS), glucose transporter (mGLUT1) gene expression and apoptosis (TUNEL assay) were assessed in NOD mice and wild-type euglycemic control mice. Spinal structural and molecular changes were analysed by micro-computed tomography (mCT), histological staining (Safranin-O and fast green) and quantitative immunofluorescence (anti-ADAMTS-4 and 5 antibodies). Statistical analysis was conducted considering the average of 35 samples ± standard error for each measurement, with 95% confidence intervals calculated to determine statistical significance (p-value < 0.05). IVDs of NOD mice showed increased disc apoptosis (p < 0.05) and higher aggrecan fragmentation mediated by ADAMTS (p < 0.05). However, ADAMTS-4 and −5 did not appear to be involved in this process. The total GAG content normalized to DNA and PG synthesis showed no statistically significant alterations, as well as Safranin O staining. Although not significantly, NOD mice showed reduced glucose uptake. In addition, the vertebral structure of NOD mice at mCT seemed not to be altered. These data demonstrate that DM may contribute to IDD by increasing aggrecan degradation and promoting cell apoptosis, which may represent early indicators of the involvement of DM in the pathogenesis of IDD

Diatoms are unicellular microalgae whose cell walls are composed of remarkably uniform, hierarchical micro/nanopatterned, amorphous biosilica that cannot be replicated synthetically. Each species hosts its own unique morphology which is identically replicated generation-to-generation. There are currently estimated to be over 200,000 different diatom species, each with their own unique shape and morphology. This offers a huge array of surface topographies, particle sizes and shapes, each with the same silica precursor. Our research to date has shown that diatom-biosilica is non-cyctotoxic to J774.2 macrophages and hBMSC cells and does not invoke an immunological response or organ toxicity (kidney, spleen and liver) when tested in a murine model. Before testing diatom-biosilica in vivo in an animal fracture model, methods to incorporate the frustules into the defect are being investigated. Two methods have been developed 1) using a bioresorbable hydrogel and 2) 3-D printed polymer-biosilica scaffolds. Both methods have shown promising results with enhanced mechanical properties with the addition of the diatom-biosilica. Work is ongoing to further map and quantify the role of surface topography and chemical cues on cell fate through the systematic in vitro studies of different species of diatom-biosilica

Osteoarthritis (OA) is a degenerative and inflammatory joint disease that affects the whole joint. Mesenchymal stem cells ability to secrete anti-inflammatory and immuno-modulatory factors represents an attractive tool in the treatment of OA. Considering the risk of cell leakage and the massive cell death upon intra-articular injection, we developed a micromolding protocol of encapsulation that allows to obtain particles that (i) could be injected with a 26G needle into a mouse joint and (ii) could provide a 3D microenvironment supporting cell biological activity. Polydimethylsiloxane (PDMS) chips containing circular micromolds were manufactured and a solution of alginate (2% w/v) containing human adipose stem cells (3 millions/mL) was deposited on the chips. Cell loading into the micromolds was performed either by sedimentation or by centrifugation. Following Ca2+ crosslinking, alginate particles (diameter 150±0.7μm) were obtained. The number of cells per particle was 5 times higher when the micromolds were loaded by centrifugation. Cell number and metabolic activity remained stable for 7 days after encapsulation and injection through a 26G needle had no impact on cell viability. When cells were stimulated with TNF-alpha and INF-gamma, prostaglandin E2 (PGE2) concentration in the supernatant was multiplied by 13 and 7 and indoleamine2,3-dioxygenase (IDO) activity was 2 and 4 times higher when cell loading was performed by sedimentation or centrifugation, respectively. We have demonstrated that encapsulated cells were able to sense and respond to an inflammatory stimulus and their therapeutic potential will be evaluated in a murine model of osteoarthritis

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

There are clinical situations in fracture repair, e.g. osteochondral fragments, where current implant hardware is insufficient. The proposition of an adhesive enabling fixation and healing has been considered but no successful candidate has emerged thus far. The many preclinical and few clinical attempts include fibrin glue, mussel adhesive and even “Kryptonite” (US bone void filler). The most promising recent attempts are based on phosphorylating amino acids, part of a common cellular adhesion mechanism linking mussels, caddis fly larvae, and mammals. Rapid high bond strength development in the wetted fatty environment of fractured bone, that is sustained during biological healing, is challenging to prove both safety and efficacy. Additionally, there are no “predicate” preclinical animal and human models which led the authors to develop novel evaluations for an adhesive candidate “OsStic. tm. ” based on calcium salts and amino acids. Adhesive formulations were evaluated in both soft (6/12 weeks) and hard tissue (3,7,10,14 & 42 days) safety studies in murine models. The feasibility of a novel adhesiveness test, initially proven in murine cadaver femoral bone, is being assessed in-vivo (3,7,10,14 & 42 days) in bilateral implantations with a standard tissue glue as the control. In parallel an ex-vivo human bone model using freshly harvested human donor bone is under development to underwrite the eventual clinical application of such an adhesive. This is part of a risk mitigation project bridging between laboratory biomaterial characterisation and a commercial biomaterial development where safety and effectiveness have to meet today´s new medical device requirements

Adipose derived mesenchymal stromal cells (ASC) are adult stem cells exhibiting functional properties that have open the way for cell-based clinical therapies. Primarily, their capacity of multilineage differentiation has been explored in a number of strategies for skeletal tissue regeneration. More recently, MSCs have been reported to exhibit immunosuppressive as well as healing capacities, to improve angiogenesis and prevent apoptosis or fibrosis through the secretion of paracrine mediators. Among the degenerative diseases associated with aging, osteoarthritis is the most common pathology and affects 16% of the female population over 65 years. Up to now, no therapeutic option exists to obtain a sustainable improvement of joint function beside knee arthroplasty. This prompted us to propose adipose derived stem cells as a possible cell therapy. We performed pre-clinical models of osteoarthritis and showed that a local injection of ASC showed a reduction of synovitis, reduction of osteophytes, joint stabilization, reducing the score of cartilage lesions. This work was completed by toxicology data showing the excellent tolerance of the local injection of ADSC and biodistribution showing the persistence of cells after 6 months in murine models. The aim of the ADIPOA trial is to demonstrate the efficacy of adipose derived stem cells therapy in knee osteoarthritis (OA) in a phase 2/3 controlled multicenter study controlled against standard of care. Safety and feasibility as well as dose response was previously assessed in the ADIPOA FP7 project. The bi-centric phase I clinical trial in Montpellier (France) and Würzburg (Germany) included 18 patients with moderate to severe knee OA, each patient received a single injection of autologous ADSC, in a open scale up dose trial, starting form 2 10 6 cells to 50 106 cells. The 107 dose appears to be well tolerated and showed preliminary response in terms of decreasing local inflammation. This first study confirmed the feasibility and safety of local injection of ADSC in knee OA and suggested the most effective dose (107 autologous ADSC). This work constituted a significant step forward treating this disease with ADSC to demonstrate safety of the procedure. we conduct a prospective multicenter randomized Phase 2/3 study with 86 patients with moderate to severe knee OA to demonstrate superiority of stem cell-based therapy compared to standard of care (SOC) in terms in reduction in clinical symptoms (WOMAC score) and structural benefit (assessed by T1rhoMRI that allow quantification of cartilage proteoglycan content). This project will offer EU a unique leadership in OA with strong positions in EU and US due to patents and quality of the methodology to demonstrate efficiency of ADSC. ADIPOA brings together a unique combination of expertises and leaders in clinical rheumatology, MRI specialists, Stem cell Institutes, national GMP grade adipose derived stem cell production platform (ECELLFRANCE) and SME specialized in cell therapy trials in the EU. The production of the cells will be granted to EFS through ECELLFRANCE national platform, which have the GMP facility and will work as a contracting manufacturing organization. The expertise, leadership and critical mass achieved by this Consortium should enable breakthroughs in ASC engineering directly amenable for clinical applications in OA

INTRODUCTION. Staphylococci species account for ∼80 % of osteomyelitis cases. While the most severe infections are caused by Staphylococcus aureus (S. aureus), the clinical significance of coagulase negative Staphylococcus epidermidis (S. epidermidis) infections remain controversial. In general, S. epidermidis was known to be a protective commensal bacterium. However, recent studies have shown that intra-operative low-grade S. epidermidis contamination prevents bone healing. Thus, the purpose of this study is to compare the pathogenic features of S. aureus and S. epidermidis in an established murine model of implant-associated osteomyelitis. METHODS. All animal experiments were performed on IACUC approved protocols. USA300LAC (MRSA) and RP62A(S. epidermidis) were used as prototypic bacterial strains. After sterilization, stainless steel pins were implanted into the tibiae of BALB/c mice (n=5 each) with or without Staphylococci. Mice were euthanized on day 14, and the implants were removed for scanning electron microscopy (SEM). Tibiae were fixed for mCT prior to decalcification for histology. RESULTS. The histology of S. aureus infected tibiae demonstrated massive osteolysis and abscesses formation. In contrast, the histology from S. epidermidis infected tibiae was indistinguishable from uninfected controls. Gross mCT analyses revealed massive bone defects around the infected implant with reactive bone formation only in the S. aureus group. The osteolysis findings were confirmed by quantitative analysis, as the medial hole area of S. aureus infected tibiae (1.67 ± 0.37 mm2) was larger than uninfected (0.15 ± 0.10 mm2) (p < 0.001) and S. epidermidis (0.19 ± 0.14 mm2) (p < 0.001) groups. Consistently, the %biofilm area on the implants of the S. aureus group (39.0 ± 13.7 %) was significantly larger than uninfected (6.3 ± 2.3 %) (p < 0.001) and S. epidermidis (12.9 ± 7.4 %) (p < 0.001). Although the amount of biofilm of S. epidermidis was much smaller than S. aureus, the presence of bacteria on the implant were confirmed by SEM. In addition, the empty lacunae, which is a feature of mature biofilm and evidence of bacterial emigration, were also present on both S. epidermidis and S. aureus infected implants. DISCUSSION. In this study, we confirmed the aggressive pathologic features S. aureus on host bone, soft tissues and biofilm formation. In contrast, we show that S. epidermidis is incapable of inducing osteolysis, reactive bone formation or soft tissue abscesses, even though it colonizes the implant in small biofilms. Collectively, the results support a potential role for S. epidermidis in implant loosening and fracture non-unions, as the bacteria can form small biofilms that could interfere with osseous integration and bone healing. However, future studies are warranted to assess the effects of S. epidermidis biofilm on implant loosening

Free patellar tendon grafts used for the intra-articular replacement of ruptured anterior cruciate ligaments (ACL) lack perfusion at the time of implantation. The central core of the graft undergoes a process of ischaemic necrosis which may result in failure. Early reperfusion of the graft may diminish the extent of this process. We assessed the role of peritendinous connective tissue in the revascularisation of the patellar tendon graft from the day of implantation up to 24 days in a murine model using intravital microscopy. The peritendinous connective-tissue envelope of the graft was either completely removed, partially removed or not stripped before implantation into dorsal skinfold chambers of recipient mice. Initial revascularisation of the grafts with preserved peritendinous connective tissues began after two days. The process was delayed by five to six times in completely stripped patellar tendons (p < 0.05). Only grafts with preserved connective tissues showed high viability whereas those which were completely stripped appeared to be subvital. The presence of peritendinous connective tissues accelerates the revascularisation of free patellar tendon grafts

Bone tissue engineering constructs (BTEC) combining natural resorbable osteoconductive scaffolds and mesenchymal stem cells (MSCs) have given promising results to repair critical size bone defect. Yet, results remain inconsistent. Adjonction of an osteoinductive factor to these BTEC, such as rh-BMP-2, to improve bone healing, seems to be a relevant strategy. However, currently supraphysiological dose of this protein are used and can lead to adverse effects such as inflammation, ectopic bone and/or bone cyst formation. Interestingly, in a preliminary study conducted in ectopic site in a murine model, a synergistic effect on bone formation was observed only when a low dose of rh-BMP-2 was associated with MSCs-seeded coral scaffolds but not with a high dose. The objective of the study was then to evaluate a BTEC combining coral scaffold, MSCs and a low dose of rh-BMP-2 in a large animal model of clinical relevance. Sixteen sheep were used for this study. MSCs were isolated from an aspirate of bone marrow harvested from the iliac crest of each sheep receiving BTEC with MSCs, cultivated and seeded on Acroporacoral scaffolds one week before implantation. Rh-BMP-2, used at two different doses (low dose: 68μg/defect and high dose: 680μg/defect), was diluted and absorbed on Acroporacoral scaffold one day before implantation. Metatarsal segmental bone defects (25 mm) were made in the left metatarsal bone of the sheep, stabilized by plate fixation, and filled with Acroporacoral scaffolds loaded with either (i) MSCs and a low dose of rh-BMP-2 (Group 1;n=6), (ii) a low dose of rh-BMP-2 (Group 2;n=5), (iii) a high dose of rh-BMP-2 (Group 3;n=5). Standard radiographs were taken after each surgery and each month until sheep sacrifice, 4 months postoperatively. Bone healing and scaffold resorption were assessed by micro-computed-tomography (μCT) and histomorphometry. Results were compared to a historical control group in which coral scaffolds were loaded with MSCs. Bone volumes (BV) evaluated by μCT and bone surfaces (BS) evaluated by histomorphometry did not differ between groups (BV: 1914±870, 1737±841, 1894±1028 and 1835±1342 mm. 3. ; BS: 25,41±14,25, 19,85±8,31, 25,54±16,98 and 26,08±22,52 %; groups 1, 2, 3 and control respectively); however, an higher bone union was observed in group 1 compared to the others (3, 1, 2 and 2 sheep with bone union in groups 1, 2, 3 and control respectively). No histological abnormalities were observed in any group. Coral resorption was almost complete in all specimens. No significant difference in coral volumes and coral surfaces was observed between groups. A trend towards a higher variability in coral resorption was noted in group 1 compared to the others. There seems to be a benefit to associate low dose of rh-BMP-2 with MSCs-seeded coral scaffolds as this strategy allowed an increase of bone unions in our model. Yet, results remain inconsistent. Although, defective coupling between scaffold resorption and bone formation impaired bone healing in some animals, adjunction of rh-BMP-2 (even at low dose) to CSMs loaded construct is a promising strategy for bone tissue engineering

Summary Statement. The deletion of gangliosides enhanced OA development by elevating MMP-13 and ADAMTS-5 expression and accelerating chondrocyte apoptosis. Gangliosides possibly play suppressive roles in IL-1α-induced inflammatory signaling cascades. Introduction. We have previously reported that glycosphingolipids (GSLs) play chondroprotective roles in the cartilage degradation process [1]. Gangliosides, one of the series of GSLs, are known to be important in intercellular signal transduction and cell-to-cell recognition [2]. Therefore, we hypothesised that gangliosides are important in cartilage metabolisms among the GSLs species. The purpose of this study was to determine the functional role of gangliosides in the development of OA in murine models. Materials & Methods. We adopted systemic GM3 synthase deficient mice (GM3S. −/−. ) which lack most of the gangliosides [3], and wild-type C57BL/6 mice as controls (WT). We applied instability-induced OA model (transecting the medial collateral ligament and removing the cranial half of the medial meniscus [4]) and age-associated OA model (following up to 15 months) with these mice. We also applied IL-1α-induced OA model with femoral head cartilage explants ex vivo. Histological evaluation and quantification of released proteoglycan (PG), secreted MMP-13, and NO in the cultured media were performed. In vitro experiments with chondrocytes extracted from articular cartilages of both genotypes (GM3S. −/−. , WT) were also performed to check the mRNA expression of cartilage degrading enzymes (MMP-13, ADAMTS-5). To test the functional roles of gangliosides, transient GM3S transfection was applied to WT chondrocytes and quantification of MMP-13 and ADAMTS-5 expression was performed. Results. Both age-associated and instability-induced OA models showed cartilage degradation in GM3S. −/−. mice were significantly more severe than WT mice. The results of IL-1α-induced OA model showed gangliosides deletion enhanced chondrocyte apoptosis and accelerated cartilage degradation. Femoral heads from GM3S. −/−. showed significantly higher concentration of MMP-13 and NO in the cultured media than those from WT. In vitro experiments revealed that ganglioside deletion enhanced MMP-13 and ADAMTS-5 expression in the chondrocytes stimulated with IL-1α. The expression of these enzymes was significantly suppressed by overexpressed GM3S in WT chondrocytes. Discussion/Conclusion. The deletion of gangliosides enhanced OA development by elevating MMP-13 and ADAMTS-5 expression and accelerating chondrocyte apoptosis. The results of this study raised the possibility that gangliosides, synthesised mainly from GM3, would play crucial roles in maintaining cartilage homeostasis among the GSLs species. Moreover, the result of overexpression experiment indicated that gangliosides play suppressive roles in IL-1α-triggered inflammatory signaling cascades. Although further studies are required to confirm our speculation, gangliosides may be the target molecules of a novel and effective strategy for the treatment of OA

Despite the development of skeletal or mesenchymal stem cell (MSC) constructs aimed at creating viable cartilage and bone, few studies have examined the effects of cytokines present in rheumatoid arthritis (RA) and osteoarthritis (OA) synovial tissues, or inhibition of these, on such constructs. This work addresses these issues using both in vitro and in vivo approaches and examines potential ways of overcoming the effects of cytokines on the integrity of cartilage and bone constructs. Synovial samples were obtained from RA or OA (n=10) patients undergoing elective hip or knee arthroplasty at Southampton General Hospital. Full ethical approval was obtained. Control bone marrow-derived stromal cells were obtained from patients undergoing emergency fractured neck of femur repair, cultured in basal, osteogenic (ascorbate and dexamethasone) and chondrogenic (transforming growth factor beta (TGFbeta3)) conditions. Differentiation towards bone and cartilage was assessed using alkaline phosphatase (ALP) staining, ALP and DNA biochemical assays and analysis of osteogenic/chondrogenic gene expression using real time polymerase chain reaction (rt-PCR). Exogenous interleukin-1 (IL-1) (10ng/mL), tumour necrosis factor alpha (TNFalpha) (10ng/mL) or interleukin-6 (IL-6) (100ng/mL) was added and effects on differentiation noted. RA and OA synovial samples were digested, cultured for 48 hours then centrifuged to produce supernatants. Cytokine profiles were determined using ELISA. These supernatants were then added to MSCs and their effects on differentiation assessed. Mesenchymal cultures in osteogenic media with IL-1 showed an additive osteogenic effect on biochemical assays. TNF exerted a less marked and IL-6 no apparent effect on osteogenic differentiation. ALP expression by rt-PCR correlated with these findings. Addition of supernatants to mesenchymal cultures produced a marked osteogenic profile that was IL-1 and TNFalpha concentration dependent, correlating with lower supernatant dilutions on initial ELISA analysis. Preliminary studies indicate that exogenous IL-1 and TNFalpha modulate the osteogenic phenotype in MSCs in vitro. OA and RA synovial supernatants affect skeletal cell differentiation. Variations in cytokine profiles between supernatants require analysis for potential confounders. A larger study is underway to investigate these effects, the effects of cytokines on skeletal cell differentiation on commercially available scaffolds both in vitro and in an in vivo murine model of bone formation