Biology subjects

Pitsillides, A. A.

Publications and source records attributed to Pitsillides, A. A..

15 recordsLinked to original sources

bioRxiv2026

Cross-species structure-mechanics prediction in the intervertebral disc

Despite long-standing uncertainty regarding the suitability of animal intervertebral disc (IVD) models for the study of human IVD pathophysiology, few cross-species studies have integrated hierarchical structure with mechanical function. In this study, we present a multiscale structure-mechanics framework combining synchrotron computed tomography (sCT), fibre tracing, digital volume correlation (DVC) with structure-based mechanical inference and finite-element modelling. Rat, mini-pig and human IVDs (n = 3/species) were imaged by sCT, with rat and mini-pig discs additionally subjected to in situ uniaxial compression and DVC. A Structure Index (SI), integrating local structural anisotropy and fibre orientation, was developed to regionally pinpoint the location of mechanically vulnerable regions. Cross-species comparison showed scale-dependent structural conservation: gross disc and lamellar organisation retained common regional features, whereas fibre-bundle architecture exhibited greater species- and regional divergence. Despite these differences, lower SI was consistently associated with elevated deformation in rat and mini-pig discs across multiple strain measures. Structure-strain inverse correlations became tighter within progressively higher-strain domains, reaching Spearman p values of approximately -0.5 to -0.7 for several strain components. Synthetic fibre phantoms confirmed that SI reflects a coupling of fibre orientation and organisation, with additional sensitivity to fibre number in poorly organised configurations. In human discs with varying degrees of degeneration, SI revealed spatial heterogeneity and redistribution of structurally vulnerable regions. Fibril-informed homogenisation provided anisotropic material properties for organ-scale finite-element modelling that independently supported SI-based predictions. Overall, these findings establish a cross-species framework linking hierarchical collagen architecture to mechanical vulnerability and provide a basis for non-invasive, structure-driven biomechanical assessment of human IVD degeneration and mechanical risk.

bioengineering↗

bioRxiv2026

Revealing multiscale architecture of the intact human spine using hierarchical phase contrast tomography

Background: Computed tomography (CT) and magnetic resonance imaging (MRI) provide detailed clinical assessment of the human spine; however, their millimeter-scale spatial resolution limits direct visualization of tissue microarchitecture and interfaces. Hierarchical phase-contrast tomography (HiP-CT) enables ex vivo non-destructive, micron-resolution imaging of intact human organs without exogenous contrast agents, extending anatomical assessment to spatial scales inaccessible to conventional clinical imaging. Purpose: To evaluate the capability of HiP-CT to visualize macro- to microanatomy of an intact adult human spine ex vivo. Methods: An intact spine (C1-L5) from a 62-year-old male donor without known skeletal disease was formalin-fixed and imaged by HiP-CT at the European Synchrotron. Whole-spine imaging was performed at 16.26 m isotropic voxels, with selected regions of interest imaged using 2.2 m voxels. Ex vivo MRI using clinical sequences was performed for anatomical comparison. Three-dimensional segmentation and quantitative analyses included intervertebral disc (IVD) grading, annulus fibrosus fiber tracing, and vertebral trabecular micro-morphometry. Results: HiP-CT enabled high spatial-resolution, multiscale imaging of the intact human spine, simultaneously visualizing vertebral bone and endplate, IVDs, spinal cord and meninges, nerve roots and ganglia, vasculature, ligaments, and musculature. Three-dimensional segmentation and virtual sectioning mapped neurovascular anatomy and vertebral vascular supply, without exogenous contrast enhancement, while preserving their relationships with surrounding tissues. Whole-spine images enabled quantitative analysis of annulus fibrosus fiber organization and vertebral trabecular microarchitecture, permitting the detection of focal posterolateral fiber disruption at the L4-L5 IVD and regional differences in trabecular architecture between cervical and lumbar vertebral bodies. Local tomography resolved annulus fibrosus lamellae, vertebral endplate Haversian systems, and facet joint hyaline cartilage at micron resolution. Conclusions: HiP-CT enables non-destructive, multiscale three-dimensional imaging of the intact human spine while preserving tissue relationships across spatial scales and hard-soft tissue boundaries. HiP-CT could provide an ex vivo microanatomical reference for future correlation with clinical imaging investigations of spinal disease and in the development and validation of imaging biomarkers.

bioengineering↗

bioRxiv2026

Articular calcified cartilage microarchitecture has a predictive role in abnormal osteochondral strain distributions in murine age-related osteoarthritis

Even though osteoarthritis is considered a disease of the whole joint, integrated analysis of articular calcified cartilage (ACC) behaviour with adjacent tissues remains a persistent limitation. Herein, we performed synchrotron X-ray computed tomography in intact loaded joints and coupled anatomical analysis with digital volume correlation to examine whether microarchitectural ACC features serve as predictive mechano-biomarkers of osteoarthritis. We reveal that male osteoarthritis-prone STR/Ort mice have thicker yet more porous ACC that contains larger but less spherical chondrocyte lacunae than their healthy parental-control CBA mice. This was linked to asymmetrical distribution of tensile and compressive strains generated under physiological loads in the ACC and underlying subchondral bone in tibial epiphyses of STR/Ort mice. Together these data suggest that murine ACC microarchitecture has a mechano-predictive role in age-related osteoarthritis.

physiology↗

bioRxiv2026

Sex differences in osteoblast matrix maturation regulate osteoblast-endothelial interactions

BackgroundBone formation during development and repair is divergently modulated by osteoblast (OB)-derived vascular endothelial growth factor (VEGF) which drives the skeletal sexual dimorphism of the bone vasculature. While the extracellular matrix (ECM) provides both structural and instructive cues to developing vasculature, the contributions of the bone matrix to this skeletal vascular dimorphism in bone remains undefined at the cellular level. MethodsPrimary OBs were isolated from neonatal female and male C57BL/6 long bones and cultured under basal or osteogenic conditions. ECM composition was quantified by Raman spectroscopy. Primary murine bone marrow endothelial cells (BMECs) were seeded directly onto established OB layers and maintained in heterotypic cocultures to assess contact-mediated effects of OB ECM on BMEC survival and expansion. OB-conditioned media (CM) was used to evaluate soluble-factor contributions, with VEGF-A concentration quantified by ELISA. ResultsRaman spectroscopy, on individual OBs from monotypic cultures, revealed sexually dimorphic ECM signatures that were independent of cellular growth profiles. Female OB matrices were enriched with type I collagen-specific proline and hydroxyproline and octacalcium phosphate with enhanced collagen intra-strand stability consistent with a matrix-dominant signature. Male OB matrices exhibited relatively lower type I collagen content and higher carbonated apatite resulting in an elevated mineral-to-matrix ratio indicative of advanced mineral maturation. After 24-hours of heterotypic culture of BMECs with OBs, BMEC numbers were 1.39-fold higher when in contact with male OBs. CM treatment of BMECs did not recapitulate these effects despite higher VEGF-A release from male OBs. ConclusionsSex differences in OB ECM are linked to divergent, contact-dependent regulation of BMEC behaviour. These findings suggest that differences in matrix maturation stat contribute to the sex-specific regulation of the skeletal vascular niche. Elucidating the mechanisms that regulate sex-specific OB-ECM production may reveal new therapeutic targets for selectively modulating pathological skeletal angiogenesis in men and women. SummaryBone is a sexually dimorphic organ, with men and women differing in bone size, strength and risk of fracture. The skeletal vasculature is essential for bone growth and repair, with bone forming osteoblast (OB) cells influencing blood vessel development through the skeletal extracellular matrix (ECM). Although the interactions between OB and vascular cells are crucial for lifelong skeletal health, it is not yet known whether sex differences in bone structure between men and women arise from differences in OB activity, or whether this divergence is driven by sex differences in blood vessel growth. Here, we show that male and female mouse OBs deposit distinct ECMs that differentially influence vascular endothelial cell behaviour. Female OBs produce a collagen-rich matrix with low mineral content. In contrast, male OB matrices contain less collagen and more mineral while releasing elevated levels of blood vessel promoting VEGF-A than females. When placed directly onto these OBs, vascular cell growth was greater when in contact with male than female OBs. Notably, this sex-dependent effect requires direct contact between both cell types and was not reproduced by exposure to OB-derived substances alone. These findings identify a cellular mechanism by which sex differences in OB matrix composition influences vascular cell behaviour in bone. Understanding how OB-vascular interactions differ by sex may help explain variation in bone health, healing capacity and disease risk between men and women. Further, our approach may support the discovery of new therapeutic targets that support bone growth and repair while targeting abnormal blood vessel growth in a sex-specific manner. HighlightsO_LIPrimary OBs from male and female C57BL/6 mouse long bones synthesise compositionally distinct ECMs. C_LIO_LIFemale OB matrices are type I collagen-rich and enriched with octacalcium phosphate, whereas male OB matrices contain less type I collagen and higher levels of carbonated apatite. C_LIO_LIBone marrow-derived endothelial cell (BMEC) growth is enhanced in heterotypic cocultures with male, but not female, OBs after 24 hours. C_LIO_LIMale OBs release higher levels of the pro-angiogenic factor VEGF-A than female OBs. C_LIO_LIThe sex-specific effects of the OB ECM on BMECs is contact-dependent and are not reproduced by treatment with OB-derived conditioned media. C_LI

cell biology↗

bioRxiv2026

Regulation and function of trans-physeal growth plate bridges: evidence for a mechanical base isolation role to minimise epiphyseal shear stress

The cartilaginous growth plate (GP) is responsible for all bone elongation during post-natal growth yet must simultaneously contribute to mechanical epiphyseal stability for articulation. How the GP balances these dual functions across the bone-cartilage-bone epiphyseal interface during complex load-growth transitions is not defined. Herein, we examine regulation and mechanobiology of GP bridges - mineralised trans-physeal GP structures - to explore whether they serve these dual GP functions. We have determined the effects of age and sex, short- and long-term joint loading and several established and new osteotropic pharmacological agents on mouse tibial GP bridge number and areal density using micro-computed tomography. We also explored temporal formation and progression of GP bridges by serial in vivo scanning and we imaged epiphyseal load-transfer in young and mature mice in situ via synchrotron X-ray computed tomography (sCT) of intact joints under physiologically oriented load. Our utilisation of digital volume correlation revealed regional 3D load-induced strain inhomogeneities in the GP that are synchronised to bridge location and this was substantiated using finite element modelling. Furthermore, direct micro- and sCT examinations showed that bridges consistently contain a singular epiphyseal/metaphyseal discontinuity which appear to serve a novel mechanical base isolation role to minimise shear stress across the GP. Our data indicate that bridges are regulatable, dynamic structures that synchronise GP strains and exhibit sensitivity to local joint mechanics. We highlight that trans-physeal bridges may contribute to longitudinal bone growth cessation whilst simultaneously stabilising the epiphysis by absorbing compression and shear strains.

bioengineering↗

bioRxiv2025

In situ profiling of nanoscale displacements uncovers mechano-architectural predictors of osteoarthritis emergence

Mechanical and anatomical interplay between the distinct tissues of the knee joint is essential for maintaining functional integrity during healthy ageing and contributes to the mechanisms that drive osteoarthritis (OA). In this study, we investigate how age- and disease-associated alterations in joint anatomy influence load transmission and tissue-level strain distribution. Using full-field synchrotron X-ray computed tomography coupled with digital volume correlation, we hierarchically characterised in situ nanoscale strains generated in response to mechanical loading across the tibial epiphysis. Our findings show that greater compressive strains accumulate in the articular condyle of male OA-prone (STR/Ort) epiphyses. Finite element modelling further demonstrated that these strain concentrations are associated with reduced load-bearing capacity, which arise from architectural differences localised to the subchondral bone plate. By coupling high-resolution imaging with computational modelling, our work provides new insights into how structural-function changes to joint anatomy contribute to the initiation and progression of mechanically driven OA. Our approach offers a means to identify early imaging biomarkers prior to OA diagnosis and has potential for monitoring interventions aimed at preserving joint mechanics while promoting healthy joint ageing.

bioengineering↗

bioRxiv2024

Synchrotron Tomography-Based Finite Element Analysis of Vertebral Endplate Loading Reveals Functional Roles for Architectural Features

Lower back pain is linked to vertebral biomechanics, with vertebral endplates (VEPs) playing a key role. Finite element modelling (FEM) is a powerful tool for studying VEP biomechanics but relies on accurate material property inputs, which remain difficult to obtain. Synchrotron computed tomography (sCT) allows for detailed visualisation of the microstructure of intact VEPs under near-physiological loads and, when coupled with digital volume correlation (DVC), can be used to quantify three-dimensional (3D) strain fields, providing experimental reference data for FEM validation. We developed an inversion pipeline to spatially couple DVC data with an image-based FE model, and thus to estimate the elastic properties of rat VEPs. On the first rat lumbar FEM, the pipeline estimated a VEP elastic modulus of 129 MPa and a Poissons ratio of 0.24. Welchs ANOVA revealed statistically significant differences between FEM and DVC strain distributions (p < 0.001) but with small effect sizes ({superscript 2} = 0.1%-0.6%), indicating high practical similarity. Its efficacy was further validated using Bland-Altman analysis, demonstrating over 95% spatial agreement between the FEM-predicted strains and the DVC measurements across multiple loading steps. The pipelines consistency was further evaluated across multiple rat lumbar FE models (n = 3), yielding an estimated VEP elastic modulus = 145 {+/-} 18 MPa and a Poissons ratio = 0.28 {+/-} 0.04. Statistically significant regional variations of strain distribution in VEPs were also identified (p < 0.05 to p < 0.001, {superscript 2} up to 41.8%). This study highlighted the efficacy of the developed pipeline in estimating the isotropic elastic modulus and Poissons ratio of VEP FEMs in a physiologically relevant, complex load transfer system. Our pipeline may be used in estimating properties of VEP in larger animals and humans.

bioengineering↗

bioRxiv2024

Multimodal imaging reveals multiscale mechanical interplay in vertebral endplate microarchitecture during intervertebral disc loading

The function of all musculoskeletal joints depends on hierarchical structures spanning the molecular to whole joint scales. Investigating biomechanics across length scales requires correlative multiscale experimental methods. This study applies multimodal in situ synchrotron imaging techniques to spinal joints - focussing on the vertebral endplates - to explore relationships between structure and mechanical strain across spatial scales. Strain mapping using digital volume correlation combined with microarchitectural analysis reveals that high tensile and shear strains play a role in the cartilage to bone transition. Correlative imaging and diffraction show that bone contains narrower mineral nano-crystallites under greater compressive prestrain compared to calcified cartilage. We hypothesise that this multiscale structural adaptation supports the mechanical function of the intervertebral disc. Future applications of the techniques presented here have potential to help unravel biomechanical underpinnings of pathologies affecting mineralised tissue structure. The multiscale structure-function relationships uncovered here may inspire the design of biomaterials and orthopaedic implants.

bioengineering↗

bioRxiv2024

Cryogenic non-invasive 3D X-ray phase-contrast imaging of unfixed, intact mouse joints reveals shifting chondrocyte hypertrophy across the endochondral interface

Objectivesi) develop and use a new cryogenically-enhanced phase contrast method to visualise hyaline articular cartilage (HAC); ii) to measure HAC, articular calcified cartilage (ACC) and total articular cartilage thicknesses in male STR/Ort (osteoarthritis, OA) and CBA (healthy) mouse tibial epiphyses, reflecting divergent OA predisposition, at three age timepoints chosen to reflect pre-OA, OA onset and late-progression; iii) to compare HAC, trans-zonal and ACC 3D chondrocyte anatomy in tibial epiphyses. MethodsSTR/Ort and CBA mouse knees (n=4 per age and strain group) were synchrotron-CT scanned at high-resolution while fresh frozen, without staining, fixation, dissection or dehydration of the joint capsule. Both cartilage thickness and cellular characteristics (chondrocyte n=420) were manually measured and statistically compared (SPSS). ResultsCryo-enhanced phase contrast allowed cartilage to be seen in full thickness with cellular detail. HAC was thicker in STR/Ort than age-matched CBA mice in 16/24 knee joint compartments and timepoints (all p<0.04). In contrast, HAC was thicker only in the posterior lateral femur of CBA mice at 10weeks (p<0.001, Table 1). ACC and total cartilage were also thicker in STR/Orts. Trans-zonal chondrocytes were smaller than ACC and HAC chondrocytes (p-values<0.001, volumes 878, 1,567m3 and 1,348m3 respectively). O_TBL View this table: org.highwire.dtl.DTLVardef@191d5a9org.highwire.dtl.DTLVardef@162523borg.highwire.dtl.DTLVardef@4b7caorg.highwire.dtl.DTLVardef@1be6005org.highwire.dtl.DTLVardef@192143d_HPS_FORMAT_FIGEXP M_TBL O_FLOATNOTABLE 1:C_FLOATNO O_TABLECAPTIONCondylar compartments in which HAC thickness was measured, and the presence or absence of a significant difference between STR/Ort and CBA mouse strains. * indicates a significant difference between strains (p<0.05). Note that the posterior lateral femur at 10 weeks of age is the only region in which STR/Ort mice have significantly thinner HAC than CBA mice. C_TABLECAPTION C_TBL ConclusionsCryogenically-enhanced phase-contrast imaging allowed cellular detail to be seen in 3D as never before in HAC in this (or any other) model. Our findings challenge current understanding by associating STR/Ort OA vulnerability with regions of thick, rather than thinning-with-age, cartilage. Our data affirm an association between excessively hypertrophic chondrocytes and OA is present in STR/Ort mice.

physiology↗

bioRxiv2022

Pharmacologic inhibition of EPHA2 decreases inflammation and pathological endochondral ossification in osteoarthritis

Low-grade inflammation and pathological endochondral ossification are processes underlying the progression of osteoarthritis, the most prevalent joint disease worldwide. In this study, data mining on publicly available transcriptomic datasets revealed EPHA2, a receptor tyrosine kinase associated with cancer, to be associated with both inflammation and endochondral ossification in osteoarthritis. A computational model of cellular signaling networks in chondrocytes predicted that in silico activation of EPHA2 in healthy chondrocytes increases inflammatory mediators and triggers hypertrophic differentiation, the phenotypic switch characteristic of endochondral ossification. We then evaluated the effect of inhibition of EPHA2 in cultured human chondrocytes isolated from individuals with osteoarthritis and demonstrated that inhibition of EPHA2 indeed reduced inflammation and hypertrophy. Additionally, systemic subcutaneous administration of the EPHA2 inhibitor ALW-II-41-27 attenuated joint degeneration in a mouse osteoarthritic model, reducing local inflammation and pathological endochondral ossification. Collectively, we demonstrate that pharmacological inhibition of EPHA2 with ALW-II-41-27 is a promising disease-modifying treatment that paves the way for a novel drug discovery pipeline for osteoarthritis.

pharmacology and toxicology↗

bioRxiv2021

Ablation of the FACIT collagen XII disturbs musculoskeletal ECM organization and causes patella dislocation and myopathy

Collagen XII, belonging to the fibril-associated collagens with interrupted triple helix (FACIT) family, assembles from three identical -chains encoded by the COL12A1 gene. The trimeric molecule consists of three N-terminal noncollagenous NC3 domains joined by disulfide bonds followed by a short interrupted collagen triple helix at the C-terminus. Collagen XII is expressed widely in the musculoskeletal system and mutations in the COL12A1 gene cause an Ehlers-Danlos/myopathy overlap syndrome, which is associated with skeletal abnormalities and muscle weakness. Our study defines the role of collagen XII in patella development using the Col12a1-/- mouse model. Deficiency in Col12a1 expression causes malformed facies patellaris femoris grooves at an early stage, which leads to patella subluxation and growth retardation. Due to the patella subluxation, more muscle fibers with centralized nuclei occur in the quadriceps than in the gastrocnemius muscles indicating a local effect. To further understand the role of collagen XII in the skeletal tissues single cell RNAseq (scRNA-seq) was performed. Comparison of the gene expression in the tenocyte cell sub-population of wild type and Col12a1-/- mice showed that several matrix genes are altered. Finally, we reinvestigated collagen XII deficient patients and observed a patella instability.

genetics↗

bioRxiv2021

A New Straightforward Method for Automated Segmentation of Trabecular Bone from Cortical Bone in Diverse and Challenging Morphologies

Many physiological, biomechanical, evolutionary and clinical studies that explore skeletal structure and function require successful separation of trabecular from cortical compartments of a bone that has been imaged by X-ray micro-computed tomography (microCT) prior to analysis. Separation is often time-consuming, involves user bias and needs manual sub-division of these two similarly radio-opaque compartments. We have developed an objective, automated protocol which reduces user bias and enables straightforward, user-friendly segmentation of trabecular from cortical bone without requiring sophisticated programming expertise. This method can conveniently be used as a "recipe" in commercial programmes (Avizo herein) and applied to a variety of datasets. Here, we characterise and share this recipe, and demonstrate its application to a range of murine and human bone types, including normal and osteoarthritic specimens, and bones with distinct embryonic origins and spanning a range of ages. We validate the method by testing inter-user bias during the scan preparation steps and confirm utility in the architecturally challenging analysis of growing murine epiphyses. We also report details of the recipe, so that other groups can readily re-create a similar method in open access programs. Our aim is that this method will be adopted widely to create a more standardized and time efficient method of segmenting trabecular and cortical bone.

physiology↗

bioRxiv2020

Bimodal Whole-Mount Imaging Of Tendon Using Confocal Microscopy And X-Ray Micro-Computed Tomography

BACKGROUND3-dimensional imaging modalities for optically dense connective tissues such as tendons are limited and typically have a single imaging methodological endpoint. Here, we have developed a bimodal procedure that utilises fluorescence-based confocal microscopy and x-ray micro-computed tomography for the imaging of adult tendons to visualise and analyse extracellular sub-structure and cellular composition in small and large animal species. RESULTSUsing fluorescent immunolabelling and optical clearing, we visualised the expression of the basement membrane protein laminin-4 in 3D throughout whole rat Achilles tendons and equine superficial digital flexor tendon 5 mm segments. This revealed a complex network of laminin-4 within the tendon core that predominantly localises to the interfascicular matrix compartment. Furthermore, we implemented a chemical drying process capable of creating contrast densities enabling visualisation and quantification of both fascicular and interfascicular matrix volume and thickness by x-ray micro-computed tomography. We also demonstrated that both modalities can be combined using reverse clarification of fluorescently labelled tissues prior to chemical drying to enable bimodal imaging of a single sample. CONCLUSIONSWhole-mount imaging of tendon allowed us to identify the presence of an extensive network of laminin-4 within tendon, the complexity of which cannot be appreciated using traditional 2D imaging techniques. Creating contrast for x-ray micro-computed tomography imaging of tendon using chemical drying is not only simple and rapid, but also markedly improves on previously published methods. Combining these methods provides the ability to gain spatio-temporal information and quantify tendon substructures to elucidate the relationship between morphology and function.

cell biology↗

bioRxiv2020

Heterogeneity of proteome dynamics between connective tissue phases of adult tendon

Maintenance of connective tissue integrity is fundamental to sustain function, requiring protein turnover to repair damaged tissue. However, connective tissue proteome dynamics remain largely undefined, as do differences in turnover rates of individual proteins in the collagen and glycoprotein phases of connective tissue extracellular matrix (ECM). Here, we investigate proteome dynamics in the collagen and glycoprotein phases of connective tissues by exploiting the spatially distinct fascicular (collagen-rich) and interfascicular (glycoprotein-rich) ECM phases of tendon. Using isotope labelling, mass spectrometry and bioinformatics, we calculate turnover rates of individual proteins within rat Achilles tendon and its ECM phases. Our results demonstrate complex proteome dynamics in tendon, with ~1000-fold differences in protein turnover rates, and overall faster protein turnover within the glycoprotein-rich interfascicular matrix compared to the collagen-rich fascicular matrix. These data provide insights into the complexity of proteome dynamics in tendon, likely required to maintain tissue homeostasis.

biochemistry↗

bioRxiv2019

Meniscal and ligament modifications in spontaneous and post-traumatic mouse models of osteoarthritis

Osteoarthritis (OA) is a whole joint disease that affects all joint tissues, with changes in the articular cartilage (AC), subchondral bone and synovium. Pathologies in menisci and ligaments, however, are rarely analysed, although both are known to play vital roles in the mechanical stability of the joint. The aim of our study was to describe the pathological changes in menisci and ligament during disease development in murine spontaneous and post-traumatic surgically-induced OA and to quantify tissue mineralisation in the joint space using {micro}CT imaging during OA progression. Knees of Str/ort mice (spontaneous OA model; 26-40wks) and C57CBA F1 mice following destabilisation of medial meniscus (DMM) surgery (post-traumatic OA model; 8wks after DMM), were used to assess histological meniscal and ligament pathologies. Joint space mineralised tissue volume was quantified by {micro}CT. Meniscal pathological changes in Str/ort mouse knees were associated with articular cartilage lesion severity. These meniscal changes included ossification, hyperplasia, cell hypertrophy, collagen type II deposition and SOX9 expression in the fibrous region near the attachment to the knee joint capsule. Anterior cruciate ligaments exhibited extracellular matrix changes and chondrogenesis particularly at the tibial attachment site, and ossification was seen in collateral ligaments. Similar changes were confirmed in the post-traumatic DMM model. {micro}CT analysis showed increased joint space mineralised tissue volume with OA progression in both the post-traumatic and spontaneous OA models. Modifications in meniscal and ligament mineralisation and chondrogenesis are seen with overt AC degeneration in murine OA. Although the aetiology and the consequences of such changes remain unknown, they will influence stability and load transmission of the joint and may therefore contribute to OA progression. In addition, these changes may have important roles in movement restriction and pain, which represent major human clinical symptoms of OA. Description of such soft tissue changes, in addition to AC degradation, should be an important aspect of future studies in mouse models in order to furnish a more complete understanding of OA pathogenesis. Summary statementThis manuscript describes histological changes in mouse knee joints in two models of osteoarthritis and correlates joint space mineralised tissue volume measured by {micro}CT with disease severity.

pathology↗