Aims

Pain is the most frequent complaint associated with osteonecrosis of the femoral head (ONFH), but the factors contributing to such pain are poorly understood. This study explored diverse demographic, clinical, radiological, psychological, and neurophysiological factors for their potential contribution to pain in patients with ONFH.

Aims. Osteoarthritis (OA) is a common degenerative disease. PA28γ is a member of the 11S proteasome activator and is involved in the regulation of several important cellular processes, including cell proliferation, apoptosis, and inflammation. This study aimed to explore the role of PA28γ in the occurrence and development of OA and its potential mechanism. Methods. A total of 120 newborn male mice were employed for the isolation and culture of primary chondrocytes. OA-related indicators such as anabolism, catabolism, inflammation, and apoptosis were detected. Effects and related mechanisms of PA28γ in chondrocyte endoplasmic reticulum (ER) stress were studied using western blotting, real-time polymerase chain reaction (PCR), and immunofluorescence. The OA mouse model was established by destabilized medial meniscus (DMM) surgery, and adenovirus was injected into the knee cavity of 15 12-week-old male mice to reduce the expression of PA28γ. The degree of cartilage destruction was evaluated by haematoxylin and eosin (HE) staining, safranin O/fast green staining, toluidine blue staining, and immunohistochemistry. Results. We found that PA28γ knockdown in chondrocytes can effectively improve anabolism and catabolism and inhibit inflammation, apoptosis, and ER stress. Moreover, PA28γ knockdown affected the phosphorylation of IRE1α and the expression of TRAF2, thereby affecting the mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signalling pathways, and finally affecting the inflammatory response of chondrocytes. In addition, we found that PA28γ knockdown can promote the phosphorylation of signal transducer and activator of transcription 3 (STAT3), thereby inhibiting ER stress in chondrocytes. The use of Stattic (an inhibitor of STAT3 phosphorylation) enhanced ER stress. In vivo, we found that PA28γ knockdown effectively reduced cartilage destruction in a mouse model of OA induced by the DMM surgery. Conclusion. PA28γ knockdown in chondrocytes can inhibit anabolic and catabolic dysregulation, inflammatory response, and apoptosis in OA. Moreover, PA28γ knockdown in chondrocytes can inhibit ER stress by promoting STAT3 phosphorylation. Cite this article: Bone Joint Res 2024;13(11):659–672

Aims

The Bankart and Latarjet procedures are two of the most common surgical techniques to treat anterior shoulder instability with satisfactory clinical and functional outcomes. However, the outcomes in the adolescent population remain unclear, and there is no information regarding the arthroscopic Latarjet in this population. The purpose of this study was to evaluate the outcomes of the arthroscopic Bankart and arthroscopic Latarjet procedures in the management of anterior shoulder instability in adolescents.

Introduction. Osteoarthritis (OA) is a prevalent joint disorder characterized by cartilage degeneration, inflammation, and pain. Current treatments provide only symptomatic relief, necessitating novel molecular targets. The caspase family, known for its roles in apoptosis and inflammation regulation, may additionally influence crucial processes for cartilage homeostasis such as differentiation and proliferation. However, the specific roles of individual caspases in OA pathogenesis remain unclear. This study aims to investigate the involvement of the caspase family in OA and as potential targets for therapy, with a focus on caspase-1 and -8. Method. Chondrocytes from both healthy and OA donors were cultured in 2D and 3D culture models and stimulated with TNF-α or IL-1β. The expression and activation of caspase-1 and -8 was assessed using RT-PCR, ELISA. Transcriptome analysis of OA and healthy cartilage samples, along with Mendelian randomization (MR) analysis were conducted to explore the involvement of caspase family in OA and to assess its potential as therapeutic targets. Result. Higher expression levels of caspase-1, -8 were observed in OA cartilage compared to healthy cartilage. TNF-α stimulation increased their expression in both healthy and OA chondrocytes, while IL-1β had limited impact. Caspase-8 expression was causally associated with knee OA in MR analysis, suggesting a potential therapeutic target. The caspase-1 inhibitor VX-765 mildly reduced chondrocyte viability, with no significant effect in the presence of TNF-α. While the caspase-8 inhibitor Z-IETD-FMK exhibited slight enhancements in cell viability, these improvements were not statistically significant. Nevertheless, its effectiveness significantly increased in the presence of TNF-α. Conclusion. This study highlights the involvement of caspase-1 and caspase-8 in OA pathology, with caspase-8 emerging as a potential therapeutic target for knee OA treatment. Further investigation into the roles of caspase-1 and -8 in OA pathophysiology, including the efficacy and potential side effects of their corresponding inhibitors, is warranted. Acknowledgements. Funding Inter-Action/Inter-Excellence project (BTHA-JC-2022-36/LUABA22019)

Introduction. Osteoarthritis (OA) causes pain, stiffness, and loss of function due to degenerative changes in joint cartilage and bone. In some forms of OA, exercise can alleviate symptoms by improving joint mobility and stability. However, excessive training after joint injury may have negative consequences for OA development. Sensory nerve fibers in joints release neuropeptides like alpha-calcitonin gene-related peptide (alpha-CGRP), potentially affecting OA progression. This study investigates the role of alpha-CGRP in OA pathogenesis under different exercise regimen in mice. Method. OA was induced in C57Bl/6J WT mice and alpha-CGRP KO mice via surgical destabilization of the medial meniscus (DMM) at 12 weeks of age (N=6). Treadmill exercise began 2 weeks post-surgery and was performed for 30 minutes, 5 days a week, for 2 or 6 weeks at intense (16 m/min, 15° incline) or moderate (10 m/min, 5° incline) levels. Histomorphometric assessment of cartilage degradation (OARSI scoring), serum cytokine analysis, immunohistochemistry, and nanoCT analysis were conducted. Result. OARSI scoring confirmed OA induction 4 weeks post-DMM surgery, with forced exercise exacerbating cartilage degradation regardless of intensity. No significant genotype-dependent differences were observed. Serum analysis revealed elevated cytokine levels associated with OA and inflammation in KO mice compared to WT mice 4 and 8 weeks post-surgery (VEGF-A, MCP-1, CXCL10, RANTES, MIP1-alpha, MIP1-beta, and RANKL). The observed effects were often exacerbated by intense exercise but rarely by DMM surgery. NanoCT analysis demonstrated increased sclerotic bone changes after 6 weeks of forced exercise in KO mice compared to WT mice. Conclusion. Our results suggest an OA promoting effect of exercise in early disease stages of posttraumatic OA. Intense exercise induced inflammatory processes correlated to increased cytokine levels in the serum that might exacerbate OA pathogenesis in later stages. The neuropeptide alpha-CGRP might play a role in protecting against these adverse effects

Introduction. The current methods for measuring femoral torsion have limitations, including variability and inaccuracies. Existing 3D methods are not reliable for abnormal femoral anteversion measurement. A new 3D method is needed for accurate measurement and planning of proximal femoral osteotomies. Currently available software for viewing and modelling CT data lacks measurement capabilities. The MSK Hip planner aims to address these limitations by combining measurement, planning, and analysis functionalities into one tool. We aim to answer 5 key questions: Is there a difference between 2D measurement methods? Is there a difference between 3D measurement methods? Is there a difference between 2D and 3D measurement methods? Are any of the measurement methods affected by the presence of osteoarthritis or a CAM deformity?. Method. After segmentation was carried out on 42 femoral CT scans using Osirix, 3D bone models were landmarked in the MSK lab hip planning software. Murphy's, Reikeras’, McBryde, and the novel MSK lab method were used to measure femoral anteversion. Result. Murphy's method had the lowest mean femoral neck anteversion (FNA) at 24.98°, while the MSK method had the highest at 28.55°. Bland-Altman plots showed systematic errors between 2D (1.201°) and 3D (1.074°) methods. All methods demonstrated good intra- and inter-user reliability. Significant differences were found between measurement methods and between patient groups. Conclusion. The MSK Hip Planner software proved useful and convenient to measure FNA. Statistically significant differences in FNA were observed between the measurement methods, as well as between patient groups when split by presence of osteoarthritis and cam deformity. Complex joint pathology and altered femoral morphology should be considered by clinicians when deciding which method to use when measuring FNA

Introduction. Homogenous and consistent preparations of mesenchymal stem cells (MSCs) can be acquired by selecting them for integrin α10β1 (integrin a10-MSCs). Safety and efficacy of intra-articular injection of allogeneic integrin a10-MSCs were shown in two post-traumatic osteoarthritis horse studies. The current study investigated immunomodulatory capacities of human integrin a10-MSCs in vitro and their cell fait after intra-articular injection in rabbits. Method. The concentration of produced immunomodulatory factors was measured after licensing integrin a10-MSCs with pro-inflammatory cytokines. Suppression of T-cell proliferation was determined in co-cultures with carboxyfluorescein N-succinimidyl ester (CFSE) labelled human peripheral blood mononuclear cells (PBMCs) stimulated with anti-CD3/CD28 and measuring the CFSE intensity of CD4+ cells. Macrophage polarization was assessed in co-cultures with differentiated THP-1 cells stimulated with lipopolysaccharide and analysing the M2 macrophage cell surface markers CD163 and CD206. In vivo homing and regeneration were investigated by injecting superparamagnetic iron oxide nanoparticles conjugated with Rhodamine B-labeled human integrin a10-MSCs in rabbits with experimental osteochondral defects. MSC distribution in the joint was followed by MRI and fluorescence microscopy. Result. The production of the immunomodulatory factors indoleamine 2,3-dioxygenase and prostaglandin E2 was increased after inflammatory licensing integrin a10-MSCs. Co-cultures with integrin a10-MSCs suppressed T-cell proliferation and increased the frequency of M2 macrophages. In vivo injected integrin a10-MSCs homed to osteochondral defects and were detected in the repair tissue of the defects up to 10 days after injection, colocalized with aggrecan and type II collagen. Conclusion. This study showed that human integrin a10-MSCs have immunomodulatory capacities and in vivo can home to the site of osteochondral damage and directly participate in cartilage regeneration. This suggests that human integrin α10β1-selected MSCs may be a promising therapy for osteoarthritis with dual mechanisms of action consisting of immunomodulation and homing to damage followed by early engraftment and differentiation into chondrocyte-like cells that deposit hyaline cartilage matrix molecules

Introduction. Weight is a modifiable risk factor for osteoarthritis (OA) progression. Despite the emphasis on weight loss, data quantifying the changes seen in joint biomechanics are limited. Bariatric surgery patients experience rapid weight loss. This provides a suitable population to study changes in joint forces and function as weight changes. Method. 10 female patients undergoing gastric bypass or sleeve gastrectomy completed 3D walking gait analysis at a self-selected pace, pre- and 6 months post-surgery. Lower limb and torso kinematic data for 10 walking trials were collected using a Vicon motion capture system and kinetics using a Kistler force plate. An inverse kinematic model in Visual 3D allowed for no translation of the hip joint centre. 6 degrees of freedom were allowed at other joints. Data were analysed using JASP with a paired samples t-test. Result. On average participants lost 28.8±7.60kg. No significant changes were observed in standing knee and hip joint angles. Walking velocity increased from 1.10±0.11 ms. -1. to 1.23±0.17 ms. -1. (t(9)=-3.060, p = 0.014) with no change in step time but a mean increase in stride length of 0.12m (SE: 0.026m; t(9)=-4.476, p = 0.002). A significant decrease of 21.5±4.2% in peak vertical ground reaction forces was observed (t(9)=12.863, p <0.001). Stride width significantly decreased by 0.04m (SE: 0.010m; t(9)=4.316, p = 0.002) along with a decrease in lateral impulse of 21.2Ns (SE: 6.977Ns; t(7), p = 0.019), but no significant difference in knee joint angles were observed. Double limb support time also significantly reduced by 0.02s (SE: 0.006s; t(9) = 3.639, p=0.005). Conclusion. The reduction in stance width and lateral impulse suggests a more sagittal compass-gait walk is being achieved. This would reduce valgus moments on the knee reducing loading in the medial compartment. The reduction in peak ground reaction force would reduce knee contact forces and again potentially slow OA progression

Introduction. Recent studies suggested that the progression of osteoarthritis (OA), a chronic degenerative joint disease, may be affected by the autonomic nervous system (ANS). Under healthy conditions, the sympathetic (SNS) and parasympathetic (PNS) branches of the ANS are well coordinated to maintain homeostasis. However, pathological conditions are frequently associated with a disturbance of this fine-tuned balance. Therefore, we analyzed whether an autonomic dysfunction occurs in OA patients. Method. 225 participants with early- or late-stage knee OA as well as 40 healthy age-matched probands were included in this study. Autonomic activity was investigated by analyzing heart rate variability (HRV), which decreases under chronic sympathetic overactivity. Time- and frequency-domain HRV indices SDRR, RMSSD, pRR50 and LF were examined. Linear regression analysis was performed to adjust for clinical characteristics, such as age, sex, BMI, or medication. Moreover, perceived chronic stress (PSQ) and pain (WOMAC) were assessed via questionnaires. In addition, the serum stress hormones cortisol, DHEA-S and IL-6 were analyzed via ELISA. Result. SDRR, RMSSD, and pRR50 were slightly reduced in the early stage of OA and showed significant decrease in the later stage of the disease. Also LF decreased significantly with OA progression. HRV was significantly influenced by the grade of OA, but not other patient characteristics. Moreover, late-stage OA patients demonstrated significantly higher PSQ and WOMAC levels compared to healthy controls. In addition, cortisol/DHEA-S ratio and IL-6 serum concentrations were significantly higher in late-stage than in early-stage OA patients and healthy controls. Conclusion. Reduced HRV, increased cortisol/DHEA-S ratio and PSQ level as well as elevated systemic IL-6 concentration indicated an autonomic shift towards a more pronounced SNS activity due to PNS deficiency in OA patients, particularly in the late-stage of the disease. Therefore, modulation of the ANS, for example by vagus nerve stimulation, might be a potential treatment strategy for of knee OA patients

Introduction. Exercise is recommended as first-line treatment for patients with hip osteoarthritis (OA). Interestingly, content and dose of exercise interventions seem to be important for the effect of exercise interventions, but the optimal content and dose is unknown. This warrants randomized controlled trials providing evidence for the optimal exercise program in Hip OA. The aim of this trial was to investigate whether progressive resistance training (PRT) is superior to neuromuscular exercise (NEMEX) for improving functional performance, hip pain and hip-related quality of life in patients with hip OA. Method. This was a multicenter, cluster-randomized, controlled, parallel-group, assessor-blinded, superiority trial. 160 participants with clinically diagnosed hip OA were recruited from hospitals and physiotherapy clinics and randomly assigned to twelve weeks of PRT or NEMEX. The PRT intervention consisted of 5 high-intensity resistance training exercises targeting muscles at the hip and knee joints. The NEMEX intervention included 10 exercises and emphasized sensorimotor control and functional stability. The primary outcome was change in the 30-second chair stand test (30s-CST). Key secondary outcomes were changes in scores on the pain and hip-related quality of life (QoL) subscales of the Hip Disability and Osteoarthritis Outcome Score (HOOS). Result. The mean changes from baseline to 12-week follow-up in the 30s-CST were 1.5 (95% CI, 0.9 to 2.1) chair stands with PRT and 1.5 (CI, 0.9 to 2.1) chair stands with NEMEX (difference, 0.0 [CI, 0.8 to 0.8] chair stands). For the HOOS pain subscale, mean changes were 8.6 (CI, 5.3 to 11.8) points with PRT and 9.3 (CI, 5.9 to 12.6) points with NEMEX. For the HOOS QoL subscale, mean changes were 8.0 (CI, 4.3 to 11.7) points with PRT and 5.7 (CI, 1.9 to 9.5) points with NEMEX. Conclusion. In patients with hip OA, PRT is not superior to NEMEX for improving functional performance, hip pain, or hip-related QoL

Introduction

A recent study to identify clinically meaningful benchmarks for gait improvement after total hip replacement (THA) has shown that the minimum clinically important improvement (MCII) in gait speed after THA is 0.32 m/sec. Currently, it remains to be investigated what preoperative factors link to suboptimal recovery of gait function after THA. This study aimed to identify preoperative lower-limb muscle predictors for gait speed improvement after THA for hip osteoarthritis.

Introduction. Kienböck's disease is generally defined as the collapse of the lunate bone, and this may lead to early wrist osteoarthritis. Replacing the collapsed lunate with an implant has regained renewed interest with the advancing technology of additive manufacturing, enabling the design of patient-specific implants. The aims of this project are (1) to determine how accurate it is to use the contralateral lunate shape as a template for patient-specific lunate implants, and (2) to study the effects of shape variations wrist kinematics using 4D-computed tomography (CT) scanning. Methods. A 3D statistical shape model (SSM) of the lunate was built based on bilateral CT scans of 54 individuals. Using SMM, shape variations of the lunate were identified and the intra- and inter-subject shape variations were compared by performing an intraclass correlation analysis. A radiolucent motor-controlled wrist-holder was designed to guide flexion/extension and radial/ulnar deviation of ex vivo wrist specimens under 4D-CT scanning. In this pilot, three shape mode variations were tested per specimen in two specimens were. After post-processing each CT, the scapholunate angle (SLA) and capitolunate angle (CLA) were measured. Results. The shape of the lunate was not symmetrical, defined as exceeding the intra-subject variation in five different shape modes. The FE tests show a generalized increase in scapholunate and capitolunate angle when using lunate implants, and comparing variation of shape modes showed that shape mode 3 has a significant effect on the measured angles (p<0.05). Discussion. The design of patient-specific lunate implants may prove to be challenging using a ‘mirror’-design as it will lead to a degree of shape asymmetry. The pilot study, to determine the effects of those shape variations on wrist kinematics suggest that the degree of shape variation observed indeed may alter the wrist kinematics, although this needs to be further investigated in study using more specimens

Introduction. Chondrocytes are enveloped within the pericellular matrix (PCM), a structurally intricate network primarily demarcated by the presence of collagen type VI microfibrils and perlecan, resembling a protective cocoon. The PCM serves pivotal functions in facilitating cell mechanoprotection and mechanotransduction. The progression of osteoarthritis (OA) is associated with alterations in the spatial arrangement of chondrocytes, transitioning from single strings to double strings, small clusters, and eventually coalescing into large clusters in advanced OA stages. Changes in cellular patters coincide with structural degradation of the PCM and loss of biomechanical properties. Here, we systematically studied matrix metalloproteinases (MMPs), their distribution, activity, and involvement in PCM destruction, utilizing chondrocyte arrangement as an OA biomarker. Methods. Cartilage specimens were obtained from 149 osteoarthritis (OA) patients, and selected based on the predominant spatial pattern of chondrocytes. Immunoassays were employed to screen for the presence of various MMPs (-1, -2, -3, -7, -8, -9, -10, -12, -13). Subsequently, the presence and activity of elevated MMPs were further investigated through immunolabeling, western blots and zymograms. Enzymatic assays were utilized to demonstrate the direct involvement of the targeted MMPs in the PCM destruction. Results. Screening revealed increased levels of MMP-1, -2, -3, -7, and -13, with their expression profile demonstrating a distinct dependency on the stage of degeneration. We found that MMP-2 and -3 can directly compromise the integrity of collagen type VI, whereas MMP-3 and MMP-7 disrupt perlecan. Conclusions. Presence of both pro- and active forms of MMP-2, -3, and -7 in OA-induced patterns, along with their direct involvement in collagen type VI and perlecan degradation, underscores their crucial role in early PCM destruction. Given the early stages of the disease already exhibit heightened MMP expression, this understanding could inform early targeted therapies aimed at arresting abnormal PCM remodelling. Acknowledgments. Faculty of Medicine of the University of Tübingen (grant: 2650-0-0)

Introduction. Within articular cartilage, chondrocytes reside within the pericellular matrix (PCM), collectively constituting the microanatomical entity known as a chondron. The PCM functions as a pivotal protective shield and mediator of biomechanical and biochemical cues. In the context of Osteoarthritis (OA), enzymatic degradation of the PCM is facilitated by matrix metalloproteinases (MMPs). This study delves into the functional implications of PCM structural integrity decline on the biomechanical properties of chondrons and impact on Ca. 2+. signaling dynamics. Method. Chondrons isolated from human cartilage explants were incubated with activated MMP-2, -3, or -7. Structural degradation of the pericellular matrix (PCM) was assessed by immunolabelling (collagen type VI and perlecan, n=5). Biomechanical properties of chondrons (i.e. elastic modulus (EM)) were analyzed using atomic force microscopy (AFM). A fluorescent calcium indicator (Fluo-4-AM) was used to record and quantify the intracellular Ca. 2+. influx of chondrons subjected to single cell mechanical loading (500nN) with AFM (n=7). Result. Each of the three MMPs disrupted the structural integrity of the PCM, leading to attenuated fluorescence intensity for both perlecan and collagen VI. A significant decrease of EM was observed for all MMP groups (p<0.005) with the most notable decrease observed for MMP-2 and MMP-7 (p<0.001). In alignment with the AFM results, there was a significant alteration in Ca. 2+. influx observed for all MMP groups (p<0.05), in particular for MMP-2 and MMP-7 (p<0.001). Conclusion. Proteolysis of the PCM by MMP-2, -3, and -7 not only significantly alters the biomechanical properties of articular chondrons but also affects their mechanotransduction profile and response to mechanical loading, indicating a close interconnection between these processes. These findings underscore the influence of an intact pericellular matrix (PCM) in protecting cells from high stress profiles and carry implications for the transmission of mechanical signaling during OA onset and progression

Introduction. Cartilage damage is a critical aspect of osteoarthritis progression, but effective imaging strategies remain limited. Consequently, multimodal imaging approaches are receiving increased attention. Gold nanomaterials, renowned for their therapeutic and imaging capabilities, hold promise in drug development. However, their potential for cartilage imaging is rarely discussed. Here, we developed a versatile nanomaterial, AuNC@BSA-Gd-I, for cartilage detection. By leveraging electrostatic interactions with sulfated glycosaminoglycans (sGAG), the AuNC@BSA-Gd-I can effectively penetrate damaged cartilage while accumulating minimally in healthy cartilage. This probe can be visualized or detected using CT, MRI, IVIS, and a gamma counter, providing a comprehensive approach to cartilage imaging. Additionally, we compared the imaging abilities, cartilage visualization capacities, and versatility of currently disclosed multimodal gold nanomaterials with those of AuNC@BSA-Gd-I. Method. The physicochemical properties of nanomaterials were measured. The potential for cartilage visualization of these nanomaterials was assessed using an in vitro porcine model. The sGAG content in cartilage was determined using the dimethylmethylene blue (DMMB) assay to establish the correlation between sGAG concentration and imaging intensity acquired at each modality. Results. The cartilage imaging abilities of AuNC@BSA-Gd-I for CT, MRI, and optical imaging were verified, with each imaging intensity demonstrating a strong correlation with the sGAG content (MRI; R2=0.93, CT; R2=0.83, IVIS; R2=0.79). Furthermore, AuNC@BSA-Gd-. 131. I effectively accumulated in defective cartilage tissue compared to healthy cartilage (23755.38 ± 5993.61 CPM/mg vs. 11699.97 ± 794.93 CPM/mg). Additionally, current gold nanomaterials excelled in individual imaging modalities but lacked effective multimodal imaging ability. Conclusion. Compared to current multimodal gold nanomaterials, AuNC@BSA-Gd-I demonstrates the potential to image cartilage across multiple medical instruments, providing investigators with a more powerful, visible, and convenient approach to detect cartilage defects. Acknowledgements. This work was financially supported by the National Health Research Institute, Taiwan (NHRI-EX112-11029SI), the National Science and Technology Council (NSTC 112-2314-B-182A-105-MY3), and Chang Gung Memorial Hospital, Taiwan (CMRPG8N0781 and CMRPG8M1281-3)

Introduction. Assessment of the humeral head translation with respect to the glenoid joint, termed humeral head migration (HHM), is crucial in total shoulder arthroplasty pre-operative planning. Its assessment informs current classification systems for shoulder osteoarthritis as well as the evaluation of surgical correction. In current clinical practice, HHM assessment relies on computed-tomography (CT) imaging. However, the associated supine position might undermine its functional relevance as it does not reflect the weight-bearing condition with active muscle engagement associated with the upright standing position of most daily activities. Therefore, we assessed to what extent HHM in a supine position is associated with HHM in a range of functional arm positions. Method. 26 shoulder osteoarthritis patients and 12 healthy volunteers were recruited. 3D shapes of the humerus and scapula were reconstructed from their respective CT scans using an image processing software. 3. , and their CT-scan-based HHMs were measured. Furthermore, all subjects underwent low-dose biplanar radiography . 4. in four quasi-static functional arm positions while standing: relaxed standing, followed by 45 degrees of shoulder extension, flexion, and abduction. Using a previously validated method implemented in the programming platforms. 5. , 3D shapes were registered to the pairs of biplanar images for each arm position and the corresponding functional HHM was measured. Bivariate correlations were assessed between the CT-based HHM and each functional arm position. Result. HHM in 45 degrees of flexion and extension both showed significant and strong correlations (r>0.66 and P<0.01) with HHM assessed in the supine position. However, such a high correlation was not found for relaxed standing and 45 abduction. Conclusion. Although HHM in a supine position correlates with HHM in 45-degree extension and flexion, it is poorly associated with the HHM in abduction and relaxed standing. These results may suggest the inclusion of more functionally-relevant patient positioning toward better-informed shoulder arthroplasty planning. Acknowledgement. Funding from PRosPERos-II Project

Introduction. Osteoarthritis (OA) occurs due to a multi-scale degradation of articular cartilage (AC) surface which aggravates the disease condition. Investigating the micro-scale structural alterations and mechano-tribological properties facilitates comprehension of disease-mechanisms to improve future injectable-therapies. This study aims to analyze these properties using various experimental and analytical methods to establish correlations between their morpho-physiological features. Method. In this study, Raman-spectroscopy was used to investigate microscale changes in AC constituents and categorize OA damage regions in knee-joint samples from joint replacement patients (Samples = 5 and Regions = 40). Following, microscale indentation and sliding tests were performed on these regions to evaluate variations in aggregate-modulus (AM) and elastic-modulus (EM), with coefficient of friction (COF). Finally, scanning electron microscopy (SEM) was employed to analyze these morphological variations. Result. Raman spectroscopy revealed degree of collagen-damage (Amide-3 α-helix to random-coil ratio I-1250/I-1280), proteoglycan-damage (Sulphated bonds SO. 3-. to CH. 2. twist ratio I-1065/I-1206), amount of bone exposure (Phosphated-hydroxyapatite PO. 4. 3-. to Amide-1 ratio I-959/I-1669) and increased crystallinity (Carbonated hydroxyapatite CO. 3. 2-. to Amide-1 ratio I-1075/I-959) in ECM. Subsequently, these regions were categorized into different groups (G) based on these damages; G1 (Proteoglycan); G2 (Collagen + Proteoglycan); G3 (Collagen + Proteoglycan + Carbonated crystallinity) G4 (Collagen or Proteoglycan + bone exposure); and G5 (Collagen + Proteoglycan + Bone exposure). Further experimentation revealed the differences in mechano-tribological properties (AM, EM, and COF) between the different groups. G5 displayed the highest values of AM (1.5 ± 0.2MPa), EM (0.3 ± 0.01MPa) and COF (0.39 ± 0.08), compared to other groups. These altered properties were confirmed via SEM that revealed micro-asperity junctions, superficial fronding, fibrillations and bone exposure at these damaged regions. Conclusion. This study demonstrated micro-scale changes in AC among OA patients commensurate to the degree of tissue damage, which correlates with disease progression altering joint structure and function particularly in regions with high COF

Introduction. Osteoarthritis (OA) often results from joint misloading, which affects chondrocyte calcium signaling through mechano-sensitive receptors such as Piezo1, -2, and TRPV4. Activation of Piezo1, especially under inflammatory conditions, can trigger premature chondrocyte apoptosis. Intra-articular glucocorticoid therapy, while beneficial against inflammation and pain in osteoarthritis, may induce oxidative stress and chondrotoxicity at higher doses. This study aims to assess the effects of glucocorticoids, particularly triamcinolone, on chondrocyte elasticity and mechanosignaling. Method. Chondrocytes isolated from articular condyles obtained from patients undergoing knee replacement surgery (n= 5) were cultured for 7 days in triamcinolone acetonide (TA) at different concentrations (0.2µM – 2mM). Cytoskeletal changes were assessed by F-actin labeling. Cell elasticity was measured using atomic force microscopy (AFM). Labeling cells (n=6 patients) with the calcium-sensitive dye (Fluo-4) enabled monitoring changes in intracellular calcium fluorescence intensity during guided single-cell mechanical indentation (500 nN) by AFM. Result. Cell exposure to 2 mM TA led to cell death and crystallization of TA in the cell culture media. However, the concentration of TA for intra-articular application is 46 times higher at 92.1 mM (40 mg/ml). The maximal pharmacological effect on viable cells was observed at 0.2 mM. AFM results showed a significant decrease of elasticity (p<0.001), alongside significantly higher calcium intensities both prior to and during mechanical stimulation in the TA-treated samples (p<0.05). Conclusion. Administration of TA significantly impacts the mechanical properties of chondrocytes, reducing cellular elasticity while simultaneously enhancing calcium-dependent mechanosensitivity. This data suggests a correlation between glucocorticoid-induced changes in cell elasticity and cell mechanosensitivity. Finding ways to minimize the effect of glucocorticoids on cell mechanosensitivity could help to make future therapies safer and reduce side effects

Introduction. Piezo1 is a mechanosensitive Ca. 2+. ion channel that has been shown to transduce hyper-physiologic mechanical loads in chondrocytes. In osteoarthritic cartilage, Piezo1 expression was shown to be upregulated by interleukin-1 alpha (IL-1α) and resulted in altered calcium dynamics and actin cytoskeleton rarefication. Together these studies highlight the importance of Piezo1 channels during joint injury. However, the mechanism by which Piezo1 regulates chondrocyte physiology and mechanotransduction during homeostasis is still largely unknown. In this study, we investigate the impact of Piezo1 activation on nuclear mechanics and chromatin methylation state. Methods. Porcine chondrocytes (n=3-5 pigs) were treated with Yoda1, a Piezo1-specific agonist, for either 2, 5, 15 or 180 minutes. To characterize chromatin state, we monitored the abundance of a chromatin methylation marker (H3K9Me3) using immunofluorescence (IF). Atomic force microscopy (AFM, 25 nm cantilever) was employed to quantify the nuclear elastic modulus (NEM) of individual cell nuclei. To explore the interplay between cytoskeletal dynamics and nuclear mechanics, chondrocytes were treated with Latrunculin A (LatA), an actin polymerization inhibitor. Result. IF experiments showed chromatin methylation was the lowest 2 minutes post Yoda1 activation of Piezo1 (p=0.027). Additionally, we found that 2 or 5 minutes post-Piezo1 activation resulted in a significantly lower NEM when compared to the control (p<0.00001). The observed decrease in NEM at 2 and 5 minutes post-Piezo1 activation was not observed after knocking down Piezo1 (p>0.99). In LatA treated cells, the elevated NEM persisted even after Piezo1 activation with Yoda1 (p>0.75). Conclusion. These findings illuminate the mechanism by which Piezo1 activation and actin remodeling regulate transient mechanotransduction during homeostasis. Further research into the transient decrease in nuclear stiffness and chromatin methylation observed during the initial 5 minutes of Piezo1-induced Ca2+ signaling, may contribute to a better understanding of the role of Piezo1 channels in joint injury and development of therapeutic interventions for osteoarthritis

Introduction. Articular cartilage has a low self-regeneration capacity. Cartilage defects have to be treated to minimize the risk of the onset of osteoarthritis. Bioactive glass (BG) is a promising source for cartilage tissue engineering. Until now, conventional BGs (like BG1393) have been used, mostly for bone regeneration, as they are able to form a hydroxyapatite layer and are therefore, less suited for cartilage reconstruction. The aim of this study is to study the effect of 3D printed hydrogel scaffolds supplemented with spheres of the BG CAR12N to improve the chondrogenesis of mesenchymal stem cells (MSCs). Method. Based on our new glass composition (CAR12N), small BG spheres (25-40 µm) were produced and mixed with hydrogel and primary human (h) MSCs. Grid printed scaffolds were cultivated up to 21 days in expansion or chondrogenic differentiation medium. Macroscopical images of the scaffolds were taken to observe surface changes. Vitality, DNA and sulfated glycosaminoglycan (GAG) content was semiquantitatively measured as well as extracellular matrix gene transcription. Result. It was possible to print grid shaped hydrogel scaffolds with BG spheres and hMSCs. No significant changes in scaffold shape, surface or pore size were detected after 21 days in culture. The BG spheres were homogeneously distributed inside the grids. Vitality was significantly higher in grids with CAR12N spheres in comparison to those without. The DNA content remained constant over three weeks, but was higher in the sphere containing scaffolds than in those without BG spheres. GAG content in the grids increased not only with additional cultivation time but especially in grids with BG spheres in chondrogenic medium. Aggrecan and type II collagen gene expression was significantly higher grids cultured in the chondrogenic differentiation medium. Conclusion. This developed 3D model, is very interesting to study the effect of BG on hMSCs and to understand the influence of leaking ions on chondrogenesis