A Human Osteochondral Tissue Model Mimicking Cytokine-Induced Key Features of Arthritis In Vitro

Cartilage Tissue Engineering in Multilayer Tissue Regeneration

The functional and structural integrity of the tissue/organ can be compromised in multilayer reconstructive applications involving cartilage tissue. Therefore, multilayer structures are needed for cartilage applications. In this review, we have examined multilayer scaffolds for use in the treatment of damage to organs such as the trachea, joint, nose, and ear, including the multilayer cartilage structure, but we have generally seen that they have potential applications in trachea and joint regeneration. In conclusion, when the existing studies are examined, the results are promising for the trachea and joint connections, but are still limited for the nasal and ear. It may have promising implications in the future in terms of reducing the invasiveness of existing grafting techniques used in the reconstruction of tissues with multilayered layers.

Microphysiological System-Generated Physiological Shear Forces Reduce TNF-α-Mediated Cartilage Damage in a 3D Model of Arthritis

Osteoarthritis (OA) is a leading cause of disability, often resulting from overuse or injury, but inactivity can also contribute to cartilage degeneration. Conventional in vivo models struggle to isolate and study the specific effects of mechanical stress on cartilage health. To address this limitation, a microphysiological system (MPS) is established to examine how varying levels of shear stress impact cartilage homeostasis. The system allows for the cultivation of 3D chondrogenic microconstructs (CMCs) derived from human mesenchymal stromal cells, simulating both physiological and pathophysiological shear stress. Inflammation is induced via TNF-α or activated peripheral blood mononuclear cells to model cartilage damage, enabling the evaluation of therapeutic interventions. The study demonstrates the development of an arthritis-like phenotype and successful restoration of cartilage conditions through a JAK inhibitor under physiological shear stress. Physiological shear stress is identified as a critical factor in maintaining cartilage integrity. This MPS offers a standardized method to study shear stress, replicate cytokine-induced cartilage damage, and simulate key features of arthritis, providing a valuable alternative to animal models.

Large-scale multicenter study reveals anticitrullinated SR-A peptide antibody as a biomarker and exacerbator for rheumatoid arthritis

Current diagnosis and treatment of rheumatoid arthritis (RA) is still challenging. More than one-third of patients with RA could not be accurately diagnosed because of lacking biomarkers. Our recent study reported that scavenger receptor-A (SR-A) is a biomarker for RA, especially for anticyclic citrullinated peptide antibody (anti-CCP)-negative RA. Here, we further identified the B cell autoantigenic epitopes of SR-A. By a large-scale multicenter study including one training and three validation cohorts of 1954 participants, we showed that anticitrullinated SR-A peptide antibody (anti-CSP) was exclusively elevated in RA as a biomarker, particularly useful for seronegative RA. Combination of anti-CSP with anti-CCP demonstrated superior diagnostic value for RA, with sensitivity of 84.83% and specificity of 92.43%. Moreover, RA anti-CSP revealed distinct glycosylation patterns, capable of provoking inflammation in cartilage organoids and exacerbating disease progression in experimental arthritis. Together, these data identify anti-CSP as an RA autoantibody clinically applicable and actively involved in disease pathogenesis.

Development and characterization of an in vitro fluorescently tagged 3D bone-cartilage interface model

Three-dimensional cultures are widely used to study bone and cartilage. These models often focus on the interaction between osteoblasts and osteoclasts or osteoblasts and chondrocytes. A culture of osteoblasts, osteoclasts and chondrocytes would represent the cells that interact in the joint and a model with these cells could be used to study many diseases that affect the joints. The goal of this study was to develop 3D bone-cartilage interface (3D-BCI) that included osteoblasts, osteocytes, osteoclasts, and cartilage. Fluorescently tagged cell lines were developed to assess the interactions as cells differentiate to form bone and cartilage. Mouse cell line, MC3T3, was labeled with a nuclear GFP tag and differentiated into osteoblasts and osteocytes in Matrigel. Raw264.7 cells transfected with a red cytoplasmic tag were added to the system and differentiated with the MC3T3 cells to form osteoclasts. A new method was developed to differentiate chondrocyte cell line ATDC5 in a cartilage spheroid, and the ATDC5 spheroid was added to the MC3T3 and Raw264.7 cell model. We used an Incucyte and functional analysis to assess the cells throughout the differentiation process. The 3D-BCI model was found to be positive for TRAP, ALP, Alizarin red and Alcian blue staining to confirm osteoblastogenesis, osteoclastogenesis, and cartilage formation. Gene expression confirmed differentiation of cells based on increased expression of osteoblast markers: Alpl, Bglap, Col1A2, and Runx2, cartilage markers: Acan, Col2A1, Plod2, and osteoclast markers: Acp5, Rank and Ctsk. Based on staining, protein expression and gene expression results, we conclude that we successfully developed a mouse model with a 3D bone-cartilage interface.

Bioprinted High-Cell-Density Laminar Scaffolds Stimulate Extracellular Matrix Production in Osteochondral Co-Cultures

Many tissues have a laminar structure, but there are limited technologies for establishing laminar co-cultures for in vitro testing. Here, we demonstrate that collagen-alginate-fibrin (CAF) hydrogel scaffolds produced using the reactive jet impingement bioprinting technique can produce osteochondral laminar co-cultures with well-defined interfaces between cell types and high cell densities to support cell-cell interaction across the interfaces. The influence of cell density and the presence of the two cell types on the production of extracellular matrix (ECM) and the emergent mechanical properties of gels is investigated using IHC, ELISA, gel mass, and the compression modulus. The results indicate that high-cell-density cultures and co-cultures with these specific cell types produce greater levels of ECM and a more biomimetic in vitro culture than low-cell-density cultures. In laminar scaffolds produced using TC28a2 chondrocytes and SaoS-2 osteoblasts, both cell density and the presence of the two cell types enhance ECM production and the mechanical properties of the cultures, presenting a promising approach for the production of more biomimetic in vitro models.

A point-of-research decision in synovial tissue engineering: Mesenchymal stromal cells, tissue derived fibroblast or CTGF-mediated mesenchymal-to-fibroblast transition

Rheumatoid arthritis (RA) and osteoarthritis (OA) are prevalent inflammatory joint diseases characterized by synovitis, cartilage, and bone destruction. Fibroblast-like synoviocytes (FLSs) of the synovial membrane are a decisive factor in arthritis, making them a target for future therapies. Developing novel strategies targeting FLSs requires advanced in vitro joint models that accurately replicate non-diseased joint tissue. This study aims to identify a cell source reflecting physiological synovial fibroblasts. Therefore, we newly compared the phenotype and metabolism of "healthy" knee-derived FLSs from patients with ligament injuries (trauma-FLSs) to mesenchymal stromal cells (MSCs), their native precursors. We differentiated MSCs into fibroblasts using connective tissue growth factor (CTGF) and compared selected protein and gene expression patterns to those obtained from trauma-FLSs and OA-FLSs. Based on these findings, we explored the potential of an MSC-derived synovial tissue model to simulate a chronic inflammatory response akin to that seen in arthritis. We have identified MSCs as a suitable cell source for synovial tissue engineering because, despite metabolic differences, they closely resemble human trauma-derived FLSs. CTGF-mediated differentiation of MSCs increased HAS2 expression, essential for hyaluronan synthesis. It showed protein expression patterns akin to OA-FLSs, including markers of ECM components and fibrosis, and enzymes leading to a shift in metabolism towards increased fatty acid oxidation. In general, cytokine stimulation of MSCs in a synovial tissue model induced pro-inflammatory and pro-angiogenic gene expression, hyperproliferation, and increased glucose consumption, reflecting cellular response in human arthritis. We conclude that MSCs can serve as a proxy to study physiological synovial processes and inflammatory responses. In addition, CTGF-mediated mesenchymal-to-fibroblast transition resembles OA-FLSs. Thus, we emphasize MSCs as a valuable cell source for tools in preclinical drug screening and their application in tissue engineering.

3D Cultures for Modelling the Microenvironment: Current Research Trends and Applications

The importance of 3D culture systems for drug screening or physio-pathological models has exponentially increased in recent years [...].

Optimization of a Tricalcium Phosphate-Based Bone Model Using Cell-Sheet Technology to Simulate Bone Disorders

Bone diseases such as osteoporosis, delayed or impaired bone healing, and osteoarthritis still represent a social, financial, and personal burden for affected patients and society. Fully humanized in vitro 3D models of cancellous bone tissue are needed to develop new treatment strategies and meet patient-specific needs. Here, we demonstrate a successful cell-sheet-based process for optimized mesenchymal stromal cell (MSC) seeding on a β-tricalcium phosphate (TCP) scaffold to generate 3D models of cancellous bone tissue. Therefore, we seeded MSCs onto the β-TCP scaffold, induced osteogenic differentiation, and wrapped a single osteogenically induced MSC sheet around the pre-seeded scaffold. Comparing the wrapped with an unwrapped scaffold, we did not detect any differences in cell viability and structural integrity but a higher cell seeding rate with osteoid-like granular structures, an indicator of enhanced calcification. Finally, gene expression analysis showed a reduction in chondrogenic and adipogenic markers, but an increase in osteogenic markers in MSCs seeded on wrapped scaffolds. We conclude from these data that additional wrapping of pre-seeded scaffolds will provide a local niche that enhances osteogenic differentiation while repressing chondrogenic and adipogenic differentiation. This approach will eventually lead to optimized preclinical in vitro 3D models of cancellous bone tissue to develop new treatment strategies.

Advances in Engineered Three-Dimensional (3D) Body Articulation Unit Models

Indeed, the body articulation units, commonly referred to as body joints, play significant roles in the musculoskeletal system, enabling body flexibility. Nevertheless, these articulation units suffer from several pathological conditions, such as osteoarthritis (OA), rheumatoid arthritis (RA), ankylosing spondylitis, gout, and psoriatic arthritis. There exist several treatment modalities based on the utilization of anti-inflammatory and analgesic drugs, which can reduce or control the pathophysiological symptoms. Despite the success, these treatment modalities suffer from major shortcomings of enormous cost and poor recovery, limiting their applicability and requiring promising strategies. To address these limitations, several engineering strategies have been emerged as promising solutions in fabricating the body articulation as unit models towards local articulation repair for tissue regeneration and high-throughput screening for drug development. In this article, we present challenges related to the selection of biomaterials (natural and synthetic sources), construction of 3D articulation models (scaffold-free, scaffold-based, and organ-on-a-chip), architectural designs (microfluidics, bioprinting, electrospinning, and biomineralization), and the type of culture conditions (growth factors and active peptides). Then, we emphasize the applicability of these articulation units for emerging biomedical applications of drug screening and tissue repair/regeneration. In conclusion, we put forward the challenges and difficulties for the further clinical application of the in vitro 3D articulation unit models in terms of the long-term high activity of the models.

Fracture Healing Research-Shift towards In Vitro Modeling?

Fractures are one of the most frequently occurring traumatic events worldwide. Approximately 10% of fractures lead to bone healing disorders, resulting in strain for affected patients and enormous costs for society. In order to shed light into underlying mechanisms of bone regeneration (habitual or disturbed), and to develop new therapeutic strategies, various in vivo, ex vivo and in vitro models can be applied. Undeniably, in vivo models include the systemic and biological situation. However, transferability towards the human patient along with ethical concerns regarding in vivo models have to be considered. Fostered by enormous technical improvements, such as bioreactors, on-a-chip-technologies and bone tissue engineering, sophisticated in vitro models are of rising interest. These models offer the possibility to use human cells from individual donors, complex cell systems and 3D models, therefore bridging the transferability gap, providing a platform for the introduction of personalized precision medicine and finally sparing animals. Facing diverse processes during fracture healing and thus various scientific opportunities, the reliability of results oftentimes depends on the choice of an appropriate model. Hence, we here focus on categorizing available models with respect to the requirements of the scientific approach.