Aims. Mesenchymal stem cells (MSCs) are usually cultured in a normoxic atmosphere (21%) in vitro, while the oxygen concentrations in human tissues and organs are 1% to 10% when the cells are transplanted in vivo. However, the impact of hypoxia on MSCs has not been deeply studied, especially its translational application. Methods. In the present study, we investigated the characterizations of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) in hypoxic (1%) and normoxic (21%) atmospheres with a long-term culture from primary to 30 generations, respectively. The comparison between both atmospheres systematically analyzed the biological functions of MSCs, mainly including stemness maintenance, immune regulation, and resistance to chondrocyte apoptosis, and studied their joint function and anti-inflammatory effects in osteoarthritis (OA) rats constructed by collagenase II. Results. We observed that long-term hypoxic culture surpassed normoxic atmosphere during hUC-MSCs culture in respect of promoting proliferation, anti-tumorigenicity, maintaining normal karyotype and stemness, inhibiting senescence, and improving immunoregulatory function and the role of anti-apoptosis in chondrocytes. Furthermore, we demonstrated that the transplantation of long-term hypoxic hUC-MSCs (Hy-MSCs) had a better therapeutic effect on OA rats compared with the hUC-MSCs cultured in the normoxic atmosphere (No-MSCs) in terms of the improved function and swelling recovery in the joints, and substantially inhibited the secretion of pro-inflammatory factors, which effectively alleviated cartilage damage by reducing the expression of matrix metallopeptidase 13 (MMP-13). Conclusion. Our results demonstrate that Hy-MSCs possess immense potential for clinical applications via promoting stemness maintenance and enhancing immunoregulatory function. Cite this article: Bone Joint Res 2024;13(12):763–777

Aims

In the treatment of basal thumb osteoarthritis (OA), intra-articular autologous fat transplantation has become of great interest within recent years as a minimally invasive and effective alternative to surgical intervention with regard to pain reduction. This study aims to assess its long-term effectiveness.

Aims

Better prediction of outcome after total hip arthroplasty (THA) is warranted. Systemic inflammation and central neuroinflammation are possibly involved in progression of osteoarthritis and pain. We explored whether inflammatory biomarkers in blood and cerebrospinal fluid (CSF) were associated with clinical outcome, and baseline pain or disability, 12 months after THA.

Addressing bone defects is a complex medical challenge that involves dealing with various skeletal conditions, including fractures, osteoporosis (OP), bone tumours, and bone infection defects. Despite the availability of multiple conventional treatments for these skeletal conditions, numerous limitations and unresolved issues persist. As a solution, advancements in biomedical materials have recently resulted in novel therapeutic concepts. As an emerging biomaterial for bone defect treatment, graphene oxide (GO) in particular has gained substantial attention from researchers due to its potential applications and prospects. In other words, GO scaffolds have demonstrated remarkable potential for bone defect treatment. Furthermore, GO-loaded biomaterials can promote osteoblast adhesion, proliferation, and differentiation while stimulating bone matrix deposition and formation. Given their favourable biocompatibility and osteoinductive capabilities, these materials offer a novel therapeutic avenue for bone tissue regeneration and repair. This comprehensive review systematically outlines GO scaffolds’ diverse roles and potential applications in bone defect treatment.

Cite this article: Bone Joint Res 2024;13(12):725–740.

Aims

This cross-sectional study aimed to investigate the in vivo ankle kinetic alterations in patients with concomitant chronic ankle instability (CAI) and osteochondral lesion of the talus (OLT), which may offer opportunities for clinician intervention in treatment and rehabilitation.

Aims. Extracellular matrix (ECM) is a critical determinant of tissue mechanobiology, yet remains poorly characterized in joint tissues beyond cartilage in osteoarthritis (OA). This review aimed to define the composition and architecture of non-cartilage soft joint tissue structural ECM in human OA, and to compare the changes observed in humans with those seen in animal models of the disease. Methods. A systematic search strategy, devised using relevant matrix, tissue, and disease nomenclature, was run through the MEDLINE, Embase, and Scopus databases. Demographic, clinical, and biological data were extracted from eligible studies. Bias analysis was performed. Results. A total of 161 studies were included, which covered capsule, ligaments, meniscus, skeletal muscle, synovium, and tendon in both humans and animals, and fat pad and intervertebral disc in humans only. These studies covered a wide variety of ECM features, including individual ECM components (i.e. collagens, proteoglycans, and glycoproteins), ECM architecture (i.e. collagen fibre organization and diameter), and viscoelastic properties (i.e. elastic and compressive modulus). Some ECM changes, notably calcification and the loss of collagen fibre organization, have been extensively studied across osteoarthritic tissues. However, most ECM features were only studied by one or a few papers in each tissue. When comparisons were possible, the results from animal experiments largely concurred with those from human studies, although some findings were contradictory. Conclusion. Changes in ECM composition and architecture occur throughout non-cartilage soft tissues in the osteoarthritic joint, but most of these remain poorly defined due to the low number of studies and lack of healthy comparator groups. Cite this article: Bone Joint Res 2024;13(12):703–715

Aims

This study aimed to determine clinical outcomes; relationships between postoperative anterior, lateral, and posterior acetabular coverage and joint survival; and prognostic factors for joint survival after transposition osteotomy of the acetabulum (TOA).

Hip fractures pose a major global health challenge, leading to high rates of morbidity and mortality, particularly among the elderly. With an ageing population, the incidence of these injuries is rising, exerting significant pressure on healthcare systems worldwide. Despite substantial research aimed at establishing best practice, several key areas remain the subject of ongoing debate. This article examines the latest evidence on the place of arthroplasty in the surgical treatment of hip fractures, with a particular focus on the choice of implant, the use of cemented versus uncemented fixation, and advances in perioperative care.

Cite this article: Bone Joint J 2024;106-B(12):1372–1376.

The December 2024 Children’s orthopaedics Roundup³⁶⁰ looks at: Establishing best practice for managing idiopathic toe walking in children: a UK consensus; Long-term outcomes of below-elbow casting in paediatric diaphyseal forearm fractures; Residual dysplasia risk persists in developmental dysplasia of the hip patients after Pavlik harness treatment; 3D printing in paediatricorthopaedics: enhancing surgical efficiency and patient outcomes; Pavlik harness treatment for hip dysplasia does not delay motor skill development in children; High prevalence of hip dysplasia found in adolescents with idiopathic scoliosis on routine spine radiographs; Minifragment plates as effective growth modulation for ulnar deformities of the distal radius in children; Long-term success of Chiari pelvic osteotomy in preserving hip function: 30-year follow-up study.

Aims. There has been limited literature regarding outcomes of acetabular rim syndrome (ARS) with persistent acetabular os in the setting of acetabular dysplasia. The purpose of this study was to characterize a cohort of adolescent and young adult patients with ARS with persistent os and compare their radiological and clinical outcomes to patients with acetabular dysplasia without an os. Methods. We reviewed a prospective database of patients undergoing periacetabular osteotomy (PAO) for symptomatic acetabular dysplasia between January 1999 and December 2021 to identify hips with preoperative os acetabuli, defined as a closed triradiate cartilage but persistence of a superolateral os acetabulum. A total of 14 hips in 12 patients with persistent os acetabuli (ARS cohort) were compared to 50 randomly selected ‘control’ hips without persistent os acetabuli. Preoperative and postoperative radiographs were measured for markers of dysplasia: lateral centre-edge angle, anterior centre-edge angle, acetabular inclination, and migration index. Union of the os was determined in patients with ≥ six months’ follow-up. Patient-reported outcome measures (PROMs) included the University of California, Los Angeles (UCLA) activity score and modified Harris Hip Score (mHHS, maximum score 80) completed at one year postoperatively. Results. There was no significant difference between the ARS and control cohorts with regard to sex distribution (p = 0.270), age at surgery (p = 0.186), or BMI (p = 0.442). Preoperatively, the ARS cohort had more severe dysplasia, including lower lateral centre-edge angle (-9.3° (SD 12.5°) vs 7.6° (SD 10.7°); p < 0.001) and greater acetabular inclination (33.9° (SD 8.2°) vs 21.8° (SD 8.7°); p < 0.001). Postoperatively, 6/13 (46%) hips with ≥ six months of radiological follow up demonstrated union of the os. There was no difference between the ARS and control cohorts at one year in UCLA score (9.1 (SD 1.5) vs 8.2 (SD 1.9); p = 0.167) or mHHS (73.4 (SD 9.5) vs 69.9 (SD 8.8); p = 0.312). Conclusion. ARS with persistent acetabular os may occur in more severe dysplasia. Union occurs in 50% cases following corrective PAO. Cite this article: Bone Joint J 2024;106-B(12):1393–1398

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

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. 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. 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)

Background. The molecular mechanisms underlying non-union bone fractures largely remain elusive. Recently, spatial transcriptomics approaches for musculoskeletal tissue samples have been developed requiring direct placement of histology sections on barcoded slides. However, Formalin-Fixed-Paraffin-Embedded (FFPE) bone sections have been associated with limited RNA quality and read depth compared to soft tissue. Here, we test spatial transcriptomics workflows based on transcriptomic probe transfer to characterize molecular features discriminating non-union and union bone fractures in mice. Method. Histological sections (n=8) used for spatial transcriptomics (Visium CytAssist FFPE; 10x Genomics, n=4 on glass slides, n=4 on hydrogel-coated slides) were obtained from a fracture healing study in female 20-week-old C57BL/6J mice receiving either a femur osteotomy (0.7mm) or a segmental defect (2.4mm) (license 22/2022, Grisons CH). Sequence alignment and manual segmentation of different tissues (bone, defect region/callus, bone marrow, muscle) were performed using SpaceRanger and LoupeBrowser (10x Genomics). Differential gene expression was performed using DESeq2 (Seurat) followed by Gene-Set-Enrichment-Analysis (GSEA) of Gene Ontology (ClusterProfiler). Group comparison of quality measures was done using a Welch's t-test. Results are given as mean±standard deviation. Result. The quality measures, mean counts, and genes per spot, were significantly ~10× higher for sections on hydrogel slides (counts: 4700±1796, genes: 2389±1170) compared to glass slides (counts: 463±415, genes: 250±223). In challenging tissues like cortical bone, we reached high counts+genes in comparison to published data. Direct comparison of a non-union and union section showed a total of 432 differentially regulated genes, 538 in the defect region/callus. GSEA revealed differential regulation of pathways involved in muscle organ morphogenesis, cartilage development and endochondral ossification. Conclusions. Optimized spatial transcriptomics workflows based on transcriptomic probe transfer enable for improved read depth in musculoskeletal tissue enabling the characterization of molecular features discriminating non-union and union bone fractures. Acknowledgements. AO Foundation (AOTRAUMA), SNSF (PhD salary)

Introduction. Three-dimensional (3D) morphological understanding of the hip joint, specifically the joint space and surrounding anatomy, including the proximal femur and the pelvis bone, is crucial for a range of orthopedic diagnoses and surgical planning. While deep learning algorithms can provide higher accuracy for segmenting bony structures, delineating hip joint space formed by cartilage layers is often left for subjective manual evaluation. This study compared the performance of two state-of-the-art 3D deep learning architectures (3D UNET and 3D UNETR) for automated segmentation of proximal femur bone, pelvis bone, and hip joint space with single and multi-class label segmentation strategies. Method. A dataset of 56 3D CT images covering the hip joint was used for the study. Two bones and hip joint space were manually segmented for training and evaluation. Deep learning models were trained and evaluated for a single-class approach for each label (proximal femur, pelvis, and the joint space) separately, and for a multi-class approach to segment all three labels simultaneously. A consistent training configuration of hyperparameters was used across all models by implementing the AdamW optimizer and Dice Loss as the primary loss function. Dice score, Root Mean Squared Error, and Mean Absolute Error were utilized as evaluation metrics. Results. Both the models performed at excellent levels for single-label segmentations in bones (dice > 0.95), but single-label joint space performance remained considerably lower (dice < 0.87). Multi-class segmentations remained at lower performance (dice < 0.88) for both models. Combining bone and joint space labels may have introduced a class imbalance problem in multi-class models, leading to lower performance. Conclusion. It is not clear if 3D UNETR provides better performance as the selection of hyperparameters was the same across the models and was not optimized. Further evaluations will be needed with baseline UNET and nnUNET modeling architectures

Introduction

The human wrist is a highly complex joint, offering extensive motion across various planes. This study investigates scapholunate ligament (SLL) injuries’ impact on wrist stability and arthritis risks using cadaveric experiments and the finite element (FE) method. It aims to validate experimental findings with FE analysis results.

Introduction. Knee Osteoarthritis (KOA) is a prevalent joint disease requiring accurate diagnosis and prompt management. The condition occurs due to cartilage deterioration and bone remodeling. Ultrasonography has emerged as a promising modality for diagnosing KOA. Medial meniscus extrusion (MME), characterized by displacement of medial meniscus beyond the joint line has been recognized as a significant marker of KOA progression. This study aimed to explore potentials Ultrasound findings in timely detection of MME and compare it to magnetic resonance imaging (MRI) as a reference standard. Method. A comprehensive literature search was performed in 4 databases from inception to May 1 2024. Two independent reviewers, initiated screening protocols and selected the articles based on inclusion and exclusion criteria and then extracted the data. Meta-analysis was conducted using R 4.3.2 packages mada and metafor. Result. A total of 2500 articles from 4 databases was retrieved; however, following the application of inclusion and exclusion criteria 23 articles were finally extracted. These studies collectively encompassed a total of 777 patients with mean age of 53.2±7.4. The mean BMI calculated for patients was 28.31 ± 2.45. All patients underwent non-weight bearing knee ultrasonography in supine position with 0° flexion. The reported medial meniscus extrusion was 2.58 mm for articles using MRI and 2.65 mm for those using Ultrasound (MD: 0.05 ± 0.12, P= 0.65, I. 2. : 54%). Our meta-analysis revealed insignificant difference between US and MRI. (SMD: 0.03, 95% CI: -0.18 _0.23, P= 0.77, I. 2. : 56%) Meta analysis for diagnostic accuracy measures yielded a pooled sensitivity and specificity of 90.8% and 77% (95% CI: 84.2% – 94.8%, 35.5% – 95.3%, respectively, I. 2. : 44%). Conclusion. Our results indicate a close alignment in the accuracy of measurements obtained using Ultrasound modality. The narrow range suggests a minimal discrepancy in MME values between MRI and ultrasound, highlighting their comparable precision in diagnostic assessments

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. 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)