Purpose: Knee osteoarthritis (OA) is a degenerative disease associated with pain, loss of function and possible need for total knee replacement (TKR). TKR is driven by disease severity and many other non-clinical factors; consequently, studying TKR endpoints for OA clinical trials has not been optimal. The recent report from Kim et al. (Kim et al., 2020) proposes the use of composite clinical endpoints based on combinations of severe pain and/or functional impairment utilizing WOMAC (Likert version) or the occurrence of TKR.

Osteoarthritis (OA) is a common, debilitating, chronic disease with no disease-modifying drug approved to date. We discovered LNA043—a derivative of angiopoietin-like 3 (ANGPTL3)—as a potent chondrogenesis inducer using a phenotypic screen with human mesenchymal stem cells. We show that LNA043 promotes chondrogenesis and cartilage matrix synthesis in vitro and regenerates hyaline articular cartilage in preclinical OA and cartilage injury models in vivo. LNA043 exerts at least part of these effects through binding to the fibronectin receptor, integrin α 5 β 1 on mesenchymal stem cells and chondrocytes. In a first-in-human (phase 1), randomized, double-blinded, placebo-controlled, single ascending dose, single-center trial ( NCT02491281 ; sponsored by Novartis Pharmaceuticals), 28 patients with knee OA were injected intra-articularly with LNA043 or placebo (3:1 ratio) either 2 h, 7 d or 21 d before total knee replacement. LNA043 met its primary safety endpoint and showed short serum pharmacokinetics, cartilage penetration and a lack of immunogenicity (secondary endpoints). Post-hoc transcriptomics profiling of cartilage revealed that a single LNA043 injection reverses the OA transcriptome signature over at least 21 d, inducing the expression of hyaline cartilage matrix components and anabolic signaling pathways, while suppressing mediators of OA progression. LNA043 is a novel disease-modifying OA drug candidate that is currently in a phase 2b trial ( NCT04864392 ) in patients with knee OA.

Purpose: Knee osteoarthritis (OA) is currently evaluated clinically using structural imaging. Meaningful change in biomechanical gait variables has been strongly associated with disease progression in knee OA, which can help to advance the understanding of this disease progression. Measurement of gait biomechanics is often performed in laboratories using optical motion capture systems and floor mounted force plates. However, these systems are expensive, not conveniently portable and require skilled staff to operate.

Advances in sensor technology have provided an opportunity to measure gait characteristics using body-worn inertial measurement units (IMUs). Whilst research investigating the validity of IMUs in reporting gait characteristics is extensive, research investigating the reliability of IMUs is limited. This study aimed to investigate the inter-session reliability of wireless IMU derived measures of gait (i.e., knee angle, range of motion) taking multiple test administrators into account. Fifteen healthy volunteers (43 ± 15 years) completed two visits. Within each visit, participants were required to perform two sets of 6 gait trials (6-metre walk tests). IMUs were placed on the participant in 7 locations on the lower limbs and waist. A different test administrator (n = 3) applied the IMUs at each set. At visit 2, this procedure was repeated with the same test administrators as visit 1. Kinematic measures of maximum angle (Knee_Max), minimum angle (Knee_Min), and range of motion (RoM) are reported for the left and right knee. The intraclass correlation coefficients (ICC), standard error of measurement (SEM) and minimum detectable change (MDC) are reported to determine IMU reliability. The results confirmed moderate to good inter-session reliability across all features (0.73-0.87). SEM values ranged from 1.21-3.32° and MDC values ranged from 3.37 – 9.21°. Therefore, IMUs appear to be a reliable method to determine inter-session gait characteristics across multiple test administrators.

When using wearable sensors for measurement and analysis of human performance, it is often necessary to integrate and synchronise data from separate sensor systems. This paper describes a synchronization technique between IMUs attached to the shanks and insoles attached at the feet and aims to solve the need to compute the ankle joint angle, which relies on synchronized sensor data. This will additionally enable concurrent analysis using gait kinematic and kinetic features. A proof-of-concept of the algorithm, which relies on cross-correlation of gyroscope sensor data from the shank and foot, to align the sensor systems is demonstrated. The algorithm output is validated against those signals synchronized using manually annotated heel-strike and toe-off ground-truth signal landmarks, identified in both the shank and feet signals using previously published definitions. Results demonstrate that the developed algorithm is capable of synchronizing both sensor systems, based on IMU data from both healthy participants and participants suffering from knee osteoarthritis, with a mean lag time bias of 25.56ms when compared to the ground truth. A proof-of-concept of technique to synchronise IMUs attached to the shanks and insoles attached at the feet is demonstrated and offers an alternative approach to sensor system synchronisation.

Purpose: Cartilage degeneration is one of the hallmarks in the development of osteoarthritis. LNA043 is a modified, recombinant version of the human angiopoietin-like 3 (ANGPTL3) protein acting directly on cartilage-resident cells to transmit a chondro-anabolic effect. A first-in-human study in patients scheduled for total knee replacement demonstrated a favourable safety profile and the modulation of several pathways involved in cartilage homeostasis and osteoarthritis (OA). A previous proof-of-mechanism study focussed on imaging using 7 Tesla magnetic resonance imaging (MRI) to show the formation of hyaline-like tissue after a single injection of 20 mg LNA04.

Purpose: The goal of this study was to identify a disease modifying osteoarthritis drug (DMOAD) that regenerates healthy hyaline cartilage in osteoarthritis (OA) through differentiation of endogenous mesenchymal stem cells (MSCs) into chondrocytes and the production of healthy hyaline cartilage matrix. Using a phenotypic screen, we discovered LNA043, a derivative of the angiopoietin-like 3 (ANGPTL3) protein and confirmed that it promotes chondrogenesis in vitro and cartilage regeneration in vivo.

Purpose: LNA043 is a modified human angiopoietin-like 3 (ANGPTL3) protein that induces chondrogenesis and cartilage repair. In a first-in-human trial (FIH), it displayed a favorable safety profile while eliciting a chondro-anabolic response as supported by the modulation of several pathways in chondrocytes involved in osteoarthritis (OA) at the RNA level. The primary objective of this trial (NCT 03334812) was to assess the efficacy of a single intra-articular (i.a.) injection of LNA043 in the regeneration of hyaline cartilage tissue at the donor site of patients undergoing autologous chondrocyte implantation (ACI). Methods: This was a randomized, placebo-controlled, double-blind, single dose, proof-of-mechanism study in subjects with cartilage lesions undergoing ACI. In total, 14 subjects were treated with a single i.a. injection (9 in LNA043 20 mg and 5 in placebo, 2:1 randomization ratio) that was administered at the end of the first surgical procedure. The study was designed to assess cartilage regeneration in 1) the artificially created ACI biopsy donor site in the intercondylar notch with a full thickness cartilage defect and 2) clinical, natural cartilage lesions (defect site). Spontaneous repair was minimized by avoiding breaching the bone lamina while performing the biopsy. Assessments of the treatment effects were done at Day 3 (baseline), Week 4 (primary endpoint), Week 12 and Week 28 using 7T magnetic resonance imaging (MRI) to detect early signs of cartilage matrix production both at the biopsy (donor) site and the clinical lesion (defect) site, along with histological confirmation at Week 4 (2nd ACI-mandated arthroscopy). The defect site being treated with ACI was assessed with MRI only at Day 3 and Week 4, prior to the implantation of the ACI graft. Volumes of the biopsy donor site and the cartilage sub-region containing the main lesion, as well as their glycosaminoglycan content (GAG), were measured by high-resolution morphological (proton)-MRI and indirectly by sodium-MRI, respectively. While the volume of the donor site was measured via manual segmentation of the 3D proton images, the cartilage sub-region volume containing the main lesion, whose shape is by nature more complex than the surgically created lesion, was measured via an automated segmentation approach using a 3D-active shape model. All sodium-MRI measurements were performed using a 15-channel sodium-only knee array coil and images with a resolution of 1.5x1.5x3 mm3 were obtained in 25 min of scanning time. For region of interest (ROI) analyses, sodium concentration maps were rescaled to the resolution of morphological proton images and overlaid with the corresponding morphological image. Cartilage sodium concentrations were calculated by using a calibration curve obtained for each scan from agarose phantoms having different sodium concentrations. GAG content in the index region was normalized to that of corresponding healthy regions of the same knee. During the second surgical procedure on Week 4, a biopsy of the regenerated tissue was taken at the donor site, and tissue debris from the defect site was collected for histological and immunohistochemical analysis prior to the ACI graft implantation. Results: The i.a. injection of LNA043 resulted in a 65±8% refilling (vs placebo: 38±11%, p=0.04) of the donor site after 4 weeks in all treated patients (Fig. 1), and increased to 86±11% at Week 28 (vs placebo: 63±14%, p=0.12) measured by manual segmentation of morphological MRIs. In two placebo patients, a partial refilling of the donor site was seen at Week 4, but it was not maintained at Week 12 and therefore considered blood contamination, absorbed at Week 12. Similarly, partial repair of the main cartilage lesion was observed at Week 4, prior to the ACI graft implantation (change from baseline in the volume of the sub-region encompassing the defect - LNA043: +128±97 mm3 vs placebo: +16±30 mm3, p=0.03). Sodium-MRI confirmed the hyaline-like cartilage nature of the regenerated tissue in the donor site: The sodium signal in the donor site increased by 26±5%, 16±6% and 38±7% in the LNA043 group vs. -2±12% (p=0.12), 13±10% (p=0.51) and 8±21% (p=0.15) in the placebo group at Weeks 4, 12 and 28, respectively indicating increasing GAG content in the LNA043 group (Fig. 2). Post-hoc pooled analysis of the sodium MRI data from both the donor and defect sites showed a significant increase in sodium signal intensity at Week 4 (p=0.01). Histological and immunohistochemical assessments of biopsies taken at the donor site on Week 4 demonstrated features of hyaline cartilage in the regenerated tissue of LNA043-treated patients, as suggested by semi-quantitative International Cartilage Regeneration & Joint Preservation Society (ICRS) II histological scoring, and by collagen type 2 staining. LNA043 was rapidly distributed from the joint to the systemic circulation and no drug-related adverse events (AEs) or serious AEs were reported during the course of this study. There were no detectable binding anti-LNA043 antibodies during the study. Conclusions: A single i.a. injection of LNA043 at 20 mg promoted refilling of the biopsy donor site with a full thickness cartilage defect in patients undergoing an ACI procedure. The newly regenerated cartilage tissue at the donor site appeared of hyaline-like quality as evidenced from its enriched content in proteoglycans detected by sodium MRI. Exploratory assessment of the main natural cartilage lesion, prior to receiving the ACI graft 4 weeks after the i.a. injection of LNA043, also showed signs of tissue formation from filling of the lesion. Finally, LNA043 displayed a consistent systemic pharmacokinetic profile with the FIH study, together with a favorable safety profile with no significant drug related safety signals and no immunogenicity. Limitations of this study include filling of the biopsy donor site with blood after the first surgery in 2 placebo patients. While the filling resolved by absorption of the blood clot at Week 12, the spontaneous repair also observed in these patients at Week 28 is an intrinsic limitation of this model, which is sensitive to drug induced changes in repair only at earlier timepoints. LNA043 is currently being investigated for the treatment of OA in phase 2 trials.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

tfmkPurpose: Osteoarthritis longitudinal studies, whether related to the progression of the disease or the effect of new therapies, require very precise measurements of cartilage structure and in some cases of its composition. Meanwhile new tools are also needed to meet the growing needs for fast and reliable image analysis. The purpose of this study was to develop a fully automated reproducible tool for analysis of morphological and compositional quantitative MR parameters in well-defined cartilage sub-fields across the human knee. This tool was deployed to proton (1H) and sodium (23Na) MR images and the reproducibility was assessed by test re-test scan of patients at baseline and after eight days. Methods: Ten patients with low-grade femoral cartilage defects were included in the study and were scanned twice on a 7T MRI scanner eight days apart. A three-dimensional double-echo steady-state (3D-DESS) sequence with isotropic resolution (0.45mm3) was used to acquire high-resolution MR images for automated cartilage segmentation, and T2 mapping, as a potential marker of cartilage quality, was performed using a 3D-triple-echo steady-state (3D-TESS) sequence. Sodium MR was also performed using a double-tuned sodium/proton coil to generate morphological images necessary for co-registration with sodium images and thus allow for assessment of glycosaminoglycan (GAG) content in specific cartilage regions of the knee. Each dataset was processed by the MRChondralHealth 2.1 prototype software (Siemens Healthcare GmbH, Erlangen, Germany) for automated segmentation of knee articular cartilage and its reconstruction in 3D. Resulting segmentation files containing 21 sub-fields determined based on anatomical landmarks that are visible on MR images but also during arthroscopy were converted to nifty files and loaded in Matlab for further post-processing. T2, T2* and sodium maps were co-registered with 3D-DESS images and corresponding values were automatically extracted for each of the 21 sub-fields (Figure 1). In case of sodium, DESS images needed to be resampled and cropped before using in MRChondralHealth. Before co-registration with sodium images, all steps must be reverted (Figure 2). Then, a multimodal co-registration method was applied using spatial mapping of fixed images (DESS) and moving images (TESS). Affine transformation with 12 degrees of freedom was used. Optimizer function parameters were determined by a previous iterative process, while a similarity index map was used as a quantitative co-registration quality marker. The resultant optimizer parameters were: initial radius = 0.001; epsilon = 1.5e-4; growth factor = 1.01; and maximum iterations = 300. Finally, the resulting transformation was applied to the actual map. Cartilage volume, thickness, and mean T2, and sodium values were automatically extracted for each of the 21 cartilage sub-fields. Similarly, seven texture features were extracted from T2 maps from each sub-field using a Gray-Level Co-Occurrence Matrix (GLCM) approach. The reproducibility of each variable was expressed as a coefficient of variation (CV, %). Results: The mean analysis time for the 3D automated segmentation was 8.2 ± 2.0 minutes per dataset. In most cases, small corrections of the automated segmentation were required, most often in the lateral posterior femur, and the lateral anterior and posterior tibia, and this took approximately 3 minutes per case. Test re-test analysis of automated cartilage segmentation and quantitative parameter extraction revealed excellent reproducibility for cartilage volume (mean CV of patella was 1,7%, tibia 0.8% and femur 1.5%) and thickness determination (mean CV of patella was 1,2%, tibia 1.7% and femur 2.4%). Similarly, T2 values from test re-test showed mean CV of 2.3% for the patella, 3.0% for the tibia and 1.4% for the femur. Sodium values from test re-test showed mean CV of 4.1% for the patella, 4.6% for the tibia and 3.2% for the femur. Finally, textural features such as homogeneity (mean CV of 1.0%), entropy (mean CV of 1.8%) and correlation (mean CV of 2.1%) were highly reproducible, while others such as autocorrelation (mean CV of 4.0%), contrast (mean CV of 6.8%), energy (mean CV of 6.7%) and dissimilarity (mean CV of 4.1%) revealed larger variability. Conclusions: This newly developed fully automated analysis of knee articular cartilage combines quantitative morphological and compositional information from 21 anatomically well-defined subfields of the knee joint and provides reproducible and robust evaluation of the cartilage volume, thickness and composition throughout the whole knee, in particular collagen specific (T2 maps) and glycosaminoglycan specific (sodium MRI) parameters. Therefore, this approach may be considered as a good alternative to manual evaluation which, as being extremely expertise-dependent and time-consuming, could represents a considerable burden for large clinical osteoarthritis trials. MRChondralHealth can automatically segment knee cartilage from large variety of isotropic sequences with sufficient bone/cartilage contrast and obtained from both 7T and 3T scanners. Multi-center trials usually accommodate protocols based on the vendor-specific sequence capabilities, therefore a robust and protocol-independent tool is required for central-reading site. MR Chondral Health also includes a registration step and automatic evaluation of parametric maps as for example T2 maps. The integrated registration algorithm however, is not optimized to the input data used in this work. As another advantage, this tool can be easily extended to other parametric and quantitative MR techniques such as gagCEST or various types of T2 and T1 mapping method.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Background:LNA043 is a modified, recombinant version of the human angiopoietin-like 3 (ANGPTL3) protein acting directly on cartilage-resident cells to transmit its cartilage anabolic effect. A first-in-human study previously demonstrated the favourable safety profile and the modulation of several pathways involved in cartilage homeostasis and osteoarthritis (OA)1. A previous proof-of-mechanism imaging study used high field (7 Tesla) magnetic resonance imaging (MRI) to show formation of hyaline-like tissue after a single injection of 20 mg LNA043 (unpublished data).Objectives:To evaluate non-invasively the chondro-regenerative capacity of multiple intra-articular (i.a.) injections of LNA043 in patients with articular cartilage lesions in the knee (NCT03275064).Methods:This was a randomised, double-blind, placebo (PBO)-controlled, proof-of-concept study in patients with a partial thickness cartilage lesion. In total, 58 patients (43 [20 mg LNA043]; 15 [PBO]), stratified by lesion type (condylar or patellar) were treated with 4 weekly i.a. injections. The primary endpoint was T2 relaxation time measurement as a marker of collagen fiber network, and cartilage lesion-volume was a secondary endpoint, both using 3-Tesla MRI. Assessments were performed at baseline, weeks (wks) 8, 16, 28 and 52 (the latter in 23/58 patients). While lesion-volume for the secondary endpoint was determined from manually segmented images, the cartilage volume of 21 sub-regions spanning the entire knee was also measured from 3D isotropic MR images employing an automated segmentation prototype software (MR Chondral Health 2.1 [MRCH], Siemens Healthcare)2. An exploratory analysis evaluated the treatment effect for the additive volume of the 3 subregions in the weight-bearing area of the medial femur.Results:No change in T2 relaxation time was detected between treatment and PBO groups. Manual segmentation showed continuous filling of the cartilage lesions up to wk 28 in LNA043-treated patients with femoral lesions (p=0.08, vs PBO) while no effect was detected for patients with patellar lesions. Given the limitations of measuring small, irregularly shaped lesions with manual image-analysis, the MRCH approach was used (Figure 1). In the medial femoral weight-bearing region, refilling was detected over time (Δ=123 mm3 at wk 28, N= 37, p= 0.05). No overgrowth was detected in the lateral femoral condyles without cartilage damage. The overall safety profile was favourable; only mild/moderate local reactions were reported, including a higher incidence of joint swelling (9.3% vs 0%) and arthralgia (11.6% vs 6.7%) for LNA043 vs PBO resolving spontaneously or with paracetamol/NSAIDs. No anti-drug antibodies were detected.Conclusion:Treatment with 4 weekly i.a. injections of 20 mg LNA043 resulted in regeneration of damaged cartilage in patients with femoral articular cartilage lesions. Automated measurement of cartilage volume in the femoral index region was able to detect a relevant treatment effect and was found to be more sensitive than the manual segmentation method. No sign of cartilage overgrowth was observed in healthy femoral regions. A Phase 2b study in patients with mild to moderate knee OA is in preparation.References:[1]Scotti et al. ACR Convergence 2020; Abstract #1483[2]Juras et al. Cartilage 2020; Sep 29:1-12Disclosure of Interests:Siegfried Trattnig: None declared, Celeste Scotti Shareholder of: Novartis, Employee of: Novartis, Didier Laurent Shareholder of: Novartis, Employee of: Novartis, Vladimir Juras: None declared, Scott Hacker Grant/research support from: Novartis, Brian Cole: None declared, Libor Pasa: None declared, Roman Lehovec: None declared, Pavol Szomolanyi: None declared, Esther Raithel Employee of: Siemens Healthcare GmbH, Franziska Saxer Shareholder of: Novartis, Employee of: Novartis, Jens Praestgaard Shareholder of: Novartis, Employee of: Novartis, Fabiola La Gamba Shareholder of: Novartis, Employee of: Novartis, José L. Jiménez Employee of: Novartis, David Sanchez Ramos Shareholder of: Novartis, Employee of: Novartis, Ronenn Roubenoff Shareholder of: Novartis, Employee of: Novartis, Matthias Schieker Shareholder of: Novartis, Employee of: Novartis

Purpose: LNA043 is a modified truncated human angiopoietin-like 3 (ANGPTL3) protein identified in a phenotypic screen for inducers of chondrogenesis and cartilage repair. The primary objective of this trial (NCT02491281) was to assess safety and tolerability of single intraarticular doses of LNA043 into the knee of patients with knee osteoarthritis (OA).

BACKGROUND:Osteoarthritis is a common inflammatory disorder with no disease-modifying therapies. Whether inhibition of interleukin-1β (IL-1β) can reduce the consequences of large joint osteoarthritis is unclear.OBJECTIVE:To determine whether IL-1β inhibition with canakinumab reduces incident total hip or knee replacement (THR/TKR).DESIGN:Exploratory analysis of a randomized trial. (ClinicalTrials.gov: NCT01327846).SETTING:1091 clinical sites in 39 countries.PARTICIPANTS:10 061 CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcomes Study) participants.INTERVENTION:Random allocation to placebo or canakinumab (50, 150, or 300 mg) subcutaneously once every 3 months.MEASUREMENTS:The primary and secondary outcomes were time to first incident THR/TKR and time to first occurrence of an osteoarthritis-related adverse event (AE). Data were obtained through blinded ascertainment of trial clinical and safety databases.RESULTS:Median follow-up was 3.7 years. For the individual canakinumab dose groups, compared with placebo, hazard ratios (HRs) for incident THR/TKR during follow-up were 0.60 (95% CI, 0.38 to 0.95) for the 50-mg group, 0.53 (CI, 0.33 to 0.84) for the 150-mg group, and 0.60 (CI, 0.38 to 0.93) for the 300-mg group. Thus, in the pooled canakinumab groups, compared with the placebo group, incidence rates for THR/TKR were 0.31 and 0.54 events per 100 person-years (HR, 0.58 [CI, 0.42 to 0.80]; P = 0.001), respectively. The HR for the secondary end point of osteoarthritis-related AEs was 0.73 (CI, 0.61 to 0.87). Similar findings were observed in analyses restricted to participants with a history of osteoarthritis.LIMITATION:Because the parent trial was not designed to examine the efficacy of IL-1β inhibitors in osteoarthritis, information on structural joint outcomes was not collected.CONCLUSION:Findings from this exploratory analysis of a randomized controlled trial support further investigation of IL-1β inhibition for treatment of large joint osteoarthritis.PRIMARY FUNDING SOURCE:Novartis Pharmaceuticals.

The first choice for reconstruction of clinical-size bone defects consists of autologous bone flaps, which often lack the required mechanical strength and cause significant donor-site morbidity. We have previously developed biological substitutes in a rabbit model by combining bone tissue engineering and flap pre-fabrication. However, spontaneous vascularization was insufficient to ensure progenitor survival in the core of the constructs. Here, we hypothesized that increased angiogenic stimulation within constructs by exogenous VEGF can significantly accelerate early vascularization and tissue in-growth. Bone marrow stromal cells from NZW rabbits (rBMSC) were transduced with a retroviral vector to express rabbit VEGF linked to a truncated version of rabbit CD4 as a cell-surface marker. Autologous cells were seeded in clinical-size 5.5 cm3 HA scaffolds wrapped in a panniculus carnosus flap to provide an ample vascular supply, and implanted ectopically. Constructs seeded with VEGF-expressing rBMSC showed significantly increased progenitor survivival, depth of tissue ingrowth and amount of mineralized tissue. Contrast-enhanced MRI after 1 week in vivo showed significantly improved tissue perfusion in the inner layer of the grafts compared to controls. Interestingly, grafts containing VEGF-expressing rBMSC displayed a hierarchically organized functional vascular tree, composed of dense capillary networks in the inner layers connected to large-caliber feeding vessels entering the constructs at the periphery. These data constitute proof of principle that providing sustained VEGF signaling, independently of cells experiencing hypoxia, is effective to drive rapid vascularization and increase early perfusion in clinical-size osteogenic grafts, leading to improved tissue formation deeper in the constructs.

Objectives Several articles have investigated potential of sodium (23Na) magnetic resonance imaging (MRI) for the in vivo evaluation of cartilage health, but so far no study tested its feasibility for the evaluation of focal cartilage lesions of grade 1 or 2 as defined by the International Cartilage Repair Society. The aims of this study were to evaluate the ability of 23Na-MRI to differentiate between early focal lesions and normal-appearing cartilage, to evaluate within-subject reproducibility of 23Na-MRI, and to monitor longitudinal changes in participants with low-grade, focal chondral lesions. Materials and Methods Thirteen participants (mean age, 50.1 ± 10.9 years; 7 women, 6 men) with low-grade, focal cartilage lesions in the weight-bearing region of femoral cartilage were included in this prospective cohort study. Participants were assessed at baseline, 1 week, 3 months, and 6 months using morphological MRI at 3 T and 7 T, compositional 23Na-MRI at 7 T, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire. 23Na signal intensities corrected for coil sensitivity and partial volume effect (23Na-cSI) were calculated in the lesion, and in weight-bearing and non–weight-bearing regions of healthy femoral cartilage. Coefficients of variation, repeated measures analysis of covariance models, and Pearson correlation coefficients were calculated to evaluate within-subject reproducibility as well as cross-sectional and longitudinal changes in 23Na-cSI values. Results The mean coefficients of variation of 23Na-cSI values between the baseline and 1-week follow-up were 5.1% or less in all cartilage regions. Significantly lower 23Na-cSI values were observed in lesion than in weight-bearing and non–weight-bearing regions at all time points (all P values ≤ 0.002). Although a significant decrease from baseline 23Na-cSI values in lesion was found at 3-month visit (P = 0.015), no substantial change was observed at 6 months. KOOS scores have improved in all subscales at 3 months and 6 months visit, with a significant increase observed only in the quality of life subscale (P = 0.004). Conclusions In vivo 23Na-MRI is a robust and reproducible method that allows to differentiate between low-grade, focal cartilage lesions and normal-appearing articular cartilage, which supports the concept that compositional cartilage changes can be found early, before the development of advanced morphological changes visible at clinical 3-T MRI.

Most bones of the human body form and heal through endochondral ossification, whereby hypertrophic cartilage (HyC) is formed and subsequently remodeled into bone. We previously demonstrated that HyC can be engineered from human mesenchymal stromal cells (hMSC), and subsequently devitalized by apoptosis induction. The resulting extracellular matrix (ECM) tissue retained osteoinductive properties, leading to ectopic bone formation. In this study, we aimed at engineering and devitalizing upscaled quantities of HyC ECM within a perfusion bioreactor, followed by in vivo assessment in an orthotopic bone repair model. We hypothesized that the devitalized HyC ECM would outperform a clinical product currently used for bone reconstructive surgery. Human MSC were genetically engineered with a gene cassette enabling apoptosis induction upon addition of an adjuvant. Engineered hMSC were seeded, differentiated, and devitalized within a perfusion bioreactor. The resulting HyC ECM was subsequently implanted in a 10-mm rabbit calvarial defect model, with processed human bone (Maxgraft®) as control. Human MSC cultured in the perfusion bioreactor generated a homogenous HyC ECM and were efficiently induced towards apoptosis. Following six weeks of in vivo implantation, microcomputed tomography and histological analyses of the defects revealed an increased bone formation in the defects filled with HyC ECM as compared to Maxgraft®. This work demonstrates the suitability of engineered devitalized HyC ECM as a bone substitute material, with a performance superior to a state-of-the-art commercial graft. Streamlined generation of the devitalized tissue transplant within a perfusion bioreactor is relevant towards standardized and automated manufacturing of a clinical product.

Purpose: If left untreated, early-stage articular cartilage lesions may progress to full-thickness, higher-grade lesions, possibly leading to further degeneration of the joint surface. This process is typically associated with the breakdown of extracellular matrix macromolecules, such as collagen type 2 and proteoglycans. This makes collagen and glycosaminoglycans (GAG) as biomarkers to monitor the status of the articular cartilage and for studies on cartilage repair. The aim of this study was to evaluate the sensitivity of a comprehensive Magnetic Resonance Imaging (MRI) approach in detecting changes in cartilage composition in ICRS grade I/II focal lesions over a 12-month period. Methods: MRI was performed at baseline, 8-day, 3, 6 and 12-month, both at 7T and 3T, on 20 subjects with ICRS Grade I/II cartilage defects. Collagen bi-layer organization was assessed by T2 mapping, and GAG content was measured both by 23Na and gagCEST-MRI (7T only) (Fig. 1). Regions-of-interest were defined in both defective and normal appearing cartilage (weight bearing [WBR] and non-weight bearing [NWBR] regions), and transferred to T2 maps, 23Na and gagCEST images for quantitative analysis. Patient functional status was assessed via the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire. Results: Higher T2 values were measured at baseline in deep and superficial layers of the defective vs healthy WBR and NWBR, both at 3T and 7T. While T2 values remained unchanged at 7T, a T2 decrease was observed over 12 months at 3T in deep (-15%) and superficial (-17%) layers of the damaged cartilage. 23Na-MRI signal intensities were ∼25% lower in the defective area vs other regions, with no large variation over the 12-month follow-up. gagCEST measurements at 7T appeared in good agreement with 23Na-MRI results. KOOS values remained stable over the 12-month time period. Conclusions: These results point to a progressive alteration of collagen structure in the defective region (despite stable KOOS), without large changes in GAG levels over 1 year in this population. These data support the use of MRI as a noninvasive alternative to cartilage biopsy for the detection of subtle changes in cartilage composition.

Objective: To investigate T-2 mapping as a possible marker for low-grade human articular cartilage lesions during a one-year follow-up, possible changes during the follow-up and compare the reliability and sensitivity of these measurements on high-field (3 T) and ultra-high-field (7 T) MRI scanners. Design: Twenty-one patients with femoral, tibial and patellar cartilage defect in the knee joint participated in the study. The MRI protocol consisted of morphological, as well as three-dimensional triple-echo steady-state (3DTESS) T-2 mapping sequences with similar parameters at 3T and 7T. Patients were scanned at five time-points up to 12 months. T-2 values were evaluated in the lesion and healthy-appearing regions for superficial and deep cartilage zone. The repeated ANOVA was used to determine differences in T-2 values at various time points. Results: A significant decrease in T-2 values was observed between baseline and six months in the superficial layer of the lesion in patients at 3 T (decrease from 41.89 +/- 9.3 ms to 31.21 +/- 7.2 ms, which is a difference of - 5.67 +/- 2.2 ms (p = 0.031)), and at 12 months in the superficial layer of the lesion in patients at 3 T (decrease from 41.89 +/- 9.3 ms to 35.28 +/- 4.9 ms, which is a difference of - 6.60 +/- 4.4 ms (p = 0.044). No significant differences were recorded at 7 T. Conclusion: The change in T-2 values acquired with 3 T 3D-TESS appears to be reflecting subtle changes of cartilage composition in the course of low-grade lesion development. 7 T T-2 mapping does not reflect these changes probably due to completely decayed short T-2 component.

Summary StatementThis study reports that hMSC can be manipulated in order to engineer a bone organ, characterised by mature osseous and vascular components and capable to recruit, host and maintain functional HSCs.IntroductionBone tissue engineering strategies are typically based on methods involving adult human Mesenchymal Stromal Cells (hMSC) in a process resembling intramembranous ossification. However, most bones develop and repair through endochondral ossification. In addition, endochondral ossification presents several advantages for regenerative purposes such as osteogenic activity, capability to drive formation of the Hematopoietic Stem Cell (HSC) niche, resistance to hypoxia, intrinsic vasculogenic potential and, consequently, efficiency of engraftment. In this study, we aimed at developing an endochondral bone organ model characterised by functional osseous and hematopoietic compartments by using hMSC.Materials & MethodsExpanded hMSC were seeded onto 8 mm diameter, 2 mm thick collagen sponges (U...