Quantitative imaging of cartilage and bone for functional assessment of gene therapy approaches in experimental arthritis

In Vitro Study of Extracellular Vesicles Migration in Cartilage-Derived Osteoarthritis Samples Using Real-Time Quantitative Multimodal Nonlinear Optics Imaging

Mesenchymal stromal cells (MSCs)-derived extracellular vesicles (EVs) are promising therapeutic nano-carriers for the treatment of osteoarthritis (OA). The assessment of their uptake in tissues is mandatory but, to date, available technology does not allow to track and quantify incorporation in real-time. To fill this knowledge gap, the present study was intended to develop an innovative technology to determine kinetics of fluorescent MSC-EV uptake by means of time-lapse quantitative microscopy techniques. Adipose-derived mesenchymal stromal cells (ASCs)-EVs were fluorescently labeled and tracked during their uptake into chondrocytes micromasses or cartilage explants, both derived from OA patients. Immunofluorescence and time-lapse coherent anti-Stokes Raman scattering, second harmonic generation and two-photon excited fluorescence were used to follow and quantify incorporation. EVs penetration appeared quickly after few minutes and reached 30-40 μm depth after 5 h in both explants and micromasses. In explants, uptake was slightly faster, with EVs signal overlapping both extracellular matrix and chondrocytes, whereas in micromasses a more homogenous diffusion was observed. The finding of this study demonstrates that this innovative technology is a powerful tool to monitor EVs migration in tissues characterized by a complex extracellular network, and to obtain data resembling in vivo conditions.

Consensus approach for 3D joint space width of metacarpophalangeal joints of rheumatoid arthritis patients using high-resolution peripheral quantitative computed tomography

Background

Joint space assessment for rheumatoid arthritis (RA) by ordinal conventional radiographic scales is susceptible to floor and ceiling effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides superior resolution, and may detect earlier changes. The goal of this work was to compare existing 3D methods to calculate joint space width (JSW) metrics in human metacarpophalangeal (MCP) joints with HR-pQCT and reach consensus for future studies. Using the consensus method, we established reproducibility with repositioning as well as feasibility for use in second-generation HR-pQCT scanners.

Methods

Three published JSW methods were compared using datasets from individuals with RA from three research centers. A SPECTRA consensus method was developed to take advantage of strengths of the individual methods. Using the SPECTRA method, reproducibility after repositioning was tested and agreement between scanner generations was also established.

Results

When comparing existing JSW methods, excellent agreement was shown for JSW minimum and mean (ICC 0.987-0.996) but not maximum and volume (ICC 0.000-0.897). Differences were identified as variations in volume definitions and algorithmic differences that generated high sensitivity to boundary conditions. The SPECTRA consensus method reduced this sensitivity, demonstrating good scan-rescan reliability (ICC >0.911) except for minimum JSW (ICC 0.656). There was strong agreement between results from first- and second-generation HR-pQCT (ICC >0.833).

Conclusions

The SPECTRA consensus method combines unique strengths of three independently-developed algorithms and leverages underlying software updates to provide a mature analysis to measure 3D JSW. This method is robust with respect to repositioning and scanner generations, suggesting its suitability for detecting change.

PLGA-based microcarriers induce mesenchymal stem cell chondrogenesis and stimulate cartilage repair in osteoarthritis

In the present study, we aimed at evaluating the ability of novel PLGA-P188-PLGA-based microspheres to induce the differentiation of mesenchymal stem/stromal cells (MSC) into chondrocytes. To this aim, we tested microspheres releasing TGFβ3 (PAM-T) in vitro and in situ, in a pathological osteoarthritic (OA) environment. We first evaluated the chondrogenic differentiation of human MSCs seeded onto PAM-T in vitro and confirmed the up-regulation of chondrogenic markers while the secretome of the cells was not changed by the 3D environment. We then injected human MSC seeded onto PAM-T in the knee joints of mice with collagenase-induced OA. After 6 weeks, histological analysis revealed that formation of a cartilage-like tissue occurred at the vicinity of PAM-T that was not observed when MSCs were seeded onto PAM. We also noticed that the endogenous articular cartilage was less degraded. The extent of cartilage protection was further analysed by confocal laser microscopy. When MSCs seeded onto PAM-T were injected early after OA induction, protection of cartilage against degradation was evidenced and this effect was associated to a higher survival of MSCs in presence of TGFβ3. This study points to the interest of using MSCs seeded onto PAM for cartilage repair and stimulation of endogenous cartilage regeneration.

Reproducibility of compartmental subchondral bone morphometry in the mouse tibiofemoral joint

AIM

Evidence suggests that subchondral bone can be used as a predictor for the onset of osteoarthritis. As such, there is a need to accurately and reproducibly quantify subchondral bone in areas where osteoarthritis develops. In this paper, we present a novel technique for the segmentation of subchondral bone in the tibiofemoral joint and assess the reproducibility of this method with multiple measures and users.

METHODS

The right hind leg of seven C57BL/6 mice were excised and imaged in μCT. The menisci and patella were manually segmented and the image data was Gaussian filtered and binarized. An in-house algorithm was used to generate cortical and epiphyseal volumes of interest and standard morphometric indices for bone were computed. The intraclass correlation coefficient (ICC), absolute precision error (PE(SD)), and precision error as a percentage of the coefficient of variation of the repeated measurements (PE(%CV)) were calculated for each index. Additionally, an inter-user study was performed using the same indices and statistics.

RESULTS

For repeated measures, ICC ranged from 0.869 (cortical bone volume fraction, femur) to 0.994 (degree of anisotropy, femur). Similarly, PE(%CV) ranged from 0.84% (cortical bone volume fraction, femur) to 5.11% (connectivity density, tibia). For repeated users, no effect was seen in the femur with a slight effect in the tibia.

CONCLUSIONS

A novel method for the automatic segmentation of cortical and epiphyseal bone is presented and is shown to be reproducible in C57BL/6 mice. This tool will allow for high-throughput studies of osteoarthritis in animal models.

Development and optimization of a high-throughput micro-computed tomography imaging method incorporating a novel analysis technique to evaluate bone mineral density of arthritic joints in a rodent model of collagen induced arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease resulting in joint inflammation, pain, and eventual bone loss. Bone loss and remodeling caused by symmetric polyarthritis, the hallmark of RA, is readily detectable by bone mineral density (BMD) measurement using micro-CT. Abnormalities in these measurements over time reflect the underlying pathophysiology of the bone. To evaluate the efficacy of anti-rheumatic agents in animal models of arthritis, we developed a high throughput knee and ankle joint imaging assay to measure BMD as a translational biomarker. A bone sample holder was custom designed for micro-CT scanning, which significantly increased assay throughput. Batch processing 3-dimensional image reconstruction, followed by automated image cropping, significantly reduced image processing time. In addition, we developed a novel, automated image analysis method to measure BMD and bone volume of knee and ankle joints. These improvements significantly increased the throughput of ex vivo bone sample analysis, reducing data turnaround from 5 days to 24 hours for a study with 200 rat hind limbs. Taken together, our data demonstrate that BMD, as quantified by micro-CT, is a robust efficacy biomarker with a high degree of sensitivity. Our innovative approach toward evaluation of BMD using optimized image acquisition and novel image processing techniques in preclinical models of RA enables high throughput assessment of anti-rheumatic agents offering a powerful tool for drug discovery.

Effect of sclerostin-neutralising antibody on periarticular and systemic bone in a murine model of rheumatoid arthritis: a microCT study

Introduction

Patients with chronic inflammatory diseases have increased bone loss and bone fragility and are at increased risk of fracture. Although anti-resorptive drugs are effective in blocking inflammation-induced bone loss, they are less effective at rebuilding bone. We have previously shown that treatment with sclerostin antibody (Scl-AbI) builds bone and can prevent or restore bone loss in a murine model of inflammatory bowel disease. In this study, we tested the effect of Scl-AbI in a murine model of rheumatoid arthritis (the collagen-induced arthritis model, CIA). We hypothesised that sclerostin blockade can protect and restore bone both locally and systemically without affecting progression of inflammation.

Methods

CIA was induced in male DBA/1 mice, which were treated with either PBS or Scl-AbI (10 mg/kg, weekly) prophylactically for 55 days or therapeutically for 21 days (starting 14 days post onset of arthritis). Systemic inflammation was assessed by measuring the serum concentration of anti-CII IgG1, IgG2a and IgG2b by ELISA. Changes in bone mass and structure, either at sites remote from the joints or at periarticular sites, were measured using DEXA and microCT. Bone focal erosion was assessed in microCT scans of ankle and knee joints.

Results

Circulating anti-CII immunoglobulins were significantly elevated in mice with CIA and there were no significant differences in the levels of anti-CII immunoglobulins in mice treated with PBS or Scl-ABI. Prophylactic Scl-AbI treatment prevented the decrease in whole body bone mineral density (BMD) and in the bone volume fraction at axial (vertebral body) and appendicular (tibial proximal metaphysis trabecular and mid-diaphysis cortical bone) sites seen in PBS-treated CIA mice, but did not prevent the formation of focal bone erosions on the periarticular bone in the knee and ankle joints. In the therapeutic study, Scl-AbI restored BMD and bone volume fraction at all assessed sites but was unable to repair focal erosions.

Conclusions

Sclerostin blockade prevented or reversed the decrease in axial and appendicular bone mass in the murine model of rheumatoid arthritis, but did not affect systemic inflammation and was unable to prevent or repair local focal erosion.

Platelet-derived growth factor BB gene-released scaffolds: biosynthesis and characterization

Tissue engineering generally requires three basic elements; stem/progenitor cells, inductive agents and a biomaterial scaffold; the latter is one of the key components which directly influences cellular activity and matrix formation. Commonly used scaffolds to repair defects in general do not induce stem cell recruitment, which is an essential element to tissue regeneration. In this study, fabrication of a scaffold which is capable of restoring damaged tissue through the recruitment of mesenchymal stem cells (MSCs) by gene therapy of the gene encoding platelet-derived growth factor-B (PDGF-B) was investigated. PDGF-B adenovirus (AdPDGF) was combined into novel mesoporous bioglass-silk fibrin scaffolds, which were characterized for their controlled release and sustained bioactivity. Our results demonstrate that these scaffolds can release PDGF-B adenovirus for up to 3 weeks and increase MSC recruitment, both in vitro and following subcutaneous implantation in mice. Osseous calvarial defects in mice further demonstrate the ability of these scaffolds to enhance tissue regeneration through stem cell homing. This study demonstrates the potent ability of host stem cells to regenerate tissue defects through recruitment of MSCs via gene therapy. Copyright © 2013 John Wiley & Sons, Ltd.