A human osteoarthritis osteochondral organ culture model for cartilage tissue engineering

A comprehensive review on 3D tissue models: Biofabrication technologies and preclinical applications

The limitations of traditional two-dimensional (2D) cultures and animal testing, when it comes to precisely foreseeing the toxicity and clinical effectiveness of potential drug candidates, have resulted in a notable increase in the rate of failure during the process of drug discovery and development. Three-dimensional (3D) in-vitro models have arisen as substitute platforms with the capacity to accurately depict in-vivo conditions and increasing the predictivity of clinical effects and toxicity of drug candidates. It has been found that 3D models can accurately represent complex tissue structure of human body and can be used for a wide range of disease modeling purposes. Recently, substantial progress in biomedicine, materials and engineering have been made to fabricate various 3D in-vitro models, which have been exhibited better disease progression predictivity and drug effects than convention models, suggesting a promising direction in pharmaceutics. This comprehensive review highlights the recent developments in 3D in-vitro tissue models for preclinical applications including drug screening and disease modeling targeting multiple organs and tissues, like liver, bone, gastrointestinal tract, kidney, heart, brain, and cartilage. We discuss current strategies for fabricating 3D models for specific organs with their strengths and pitfalls. We expand future considerations for establishing a physiologically-relevant microenvironment for growing 3D models and also provide readers with a perspective on intellectual property, industry, and regulatory landscape.

Progress in Osteochondral Regeneration with Engineering Strategies

Osteoarthritis, the main cause of disability worldwide, involves not only cartilage injury but also subchondral bone injury, which brings challenges to clinical repair. Tissue engineering strategies provide a promising solution to this degenerative disease. Articular cartilage connects to subchondral bone through the osteochondral interfacial tissue, which has a complex anatomical architecture, distinct cell distribution and unique biomechanical properties. Forming a continuous and stable osteochondral interface between cartilage tissue and subchondral bone is challenging. Thus, successful osteochondral regeneration with engineering strategies requires intricately coordinated interplay between cells, materials, biological factors, and physical/chemical factors. This review provides an overview of the anatomical composition, microstructure, and biomechanical properties of the osteochondral interface. Additionally, the latest research on the progress related to osteochondral regeneration is reviewed, especially discussing the fabrication of biomimetic scaffolds and the regulation of biological factors for osteochondral defects.

Regeneration of Articular Cartilage Using Membranes of Polyester Scaffolds in a Rabbit Model

One promising method for cartilage regeneration involves combining known methods, such as the microfracture technique with biomaterials, e.g., scaffolds (membranes). The most important feature of such implants is their appropriate rate of biodegradation, without the production of toxic metabolites. This study presents work on two different membranes made of polyester (L-lactide-co-ε-caprolactone-PLCA) named “PVP and “Z”. The difference between them was the use of different pore precursors—polyvinylpyrrolidone in the “PVP” scaffold and gelatin in the “Z” scaffold. These were implemented in the articular cartilage defects of rabbit knee joints (defects were created for the purpose of the study). After 8, 16, and 24 weeks of observation, and the subsequent termination of the animals, histopathology and gel permeation chromatography (GPC) examinations were performed. Statistical analysis proved that the membranes support the regeneration process. GPC testing proved that the biodegradation process is progressing exponentially, causing the membranes to degrade at the appropriate time. The surgical technique we used meets all the requirements without causing the membrane to migrate after implantation. The “PVP” membrane is better due to the fact that after 24 weeks of observation there was a statistical trend for higher histological ratings. It is also better because it is easier to implant due to its lower fragility then membrane “Z”. We conclude that the selected membranes seem to support the regeneration of articular cartilage in the rabbit model.

Instructive cartilage regeneration modalities with advanced therapeutic implantations under abnormal conditions

The development of interdisciplinary biomedical engineering brings significant breakthroughs to the field of cartilage regeneration. However, cartilage defects are considerably more complicated in clinical conditions, especially when injuries occur at specific sites (e.g., osteochondral tissue, growth plate, and weight-bearing area) or under inflammatory microenvironments (e.g., osteoarthritis and rheumatoid arthritis). Therapeutic implantations, including advanced scaffolds, developed growth factors, and various cells alone or in combination currently used to treat cartilage lesions, address cartilage regeneration under abnormal conditions. This review summarizes the strategies for cartilage regeneration at particular sites and pathological microenvironment regulation and discusses the challenges and opportunities for clinical transformation.

Two-Dimensional and Three-Dimensional Cartilage Model Platforms for Drug Evaluation and High-Throughput Screening Assays

Osteoarthritis (OA) is a severely painful and debilitating disease of the joint, which brings about degradation of the articular cartilage and currently has few therapeutic solutions. Two-dimensional (2D) high-throughput screening (HTS) assays have been widely used to identify candidate drugs with therapeutic potential for the treatment of OA. A number of small molecules which improve the chondrogenic differentiation of progenitor cells for tissue engineering applications have also been discovered in this way. However, due to the failure of these models to accurately represent the native joint environment, the efficacy of these drugs has been limited in vivo. Screening systems utilizing three-dimensional (3D) models, which more closely reflect the tissue and its complex cell and molecular interactions, have also been described. However, the vast majority of these systems fail to recapitulate the complex, zonal structure of articular cartilage and its unique cell population. This review summarizes current 2D HTS techniques and addresses the question of how to use existing 3D models of tissue-engineered cartilage to create 3D drug screening platforms with improved outcomes. Impact statement Currently, the use of two-dimensional (2D) screening platforms in drug discovery is common practice. However, these systems often fail to predict efficacy in vivo, as they do not accurately represent the complexity of the native three-dimensional (3D) environment. This article describes existing 2D and 3D high-throughput systems used to identify small molecules for osteoarthritis treatment or in vitro chondrogenic differentiation, and suggests ways to improve the efficacy of these systems based on the most recent research.

Directed Regeneration of Osteochondral Tissue by Hierarchical Assembly of Spatially Organized Composite Spheroids

The use of engineered scaffolds or stem cells is investigated widely in the repair of injured musculoskeletal tissue. However, the combined regeneration of hierarchical osteochondral tissue remains a challenge due to delamination between cartilage and subchondral bone or difficulty in spatial control over differentiation of transplanted stem cells. Here, two types of composite spheroids are prepared using adipose-derived stem cells (hADSCs) and nanofibers coated with either transforming growth factor-β3 or bone morphogenetic growth factor-2 for chondrogenesis or osteogenesis, respectively. Each type of spheroid is then cultured within a 3D-printed microchamber in a spatially arranged manner to recapitulate the bilayer structure of osteochondral tissue. The presence of inductive factors regionally modulates in vitro chondrogenic or osteogenic differentiation of hADSCs within the biphasic construct without dedifferentiation. Furthermore, hADSCs from each spheroid proliferate and sprout and successfully connect the two layers mimicking the osteochondral interface without apertures. In vivo transplantation of the biphasic construct onto a femoral trochlear groove defect in rabbit knee joint results in 21.2 ± 2.8% subchondral bone volume/total volume and a cartilage score of 25.0 ± 3.7. The present approach can be an effective therapeutic platform to engineer complex tissue.

Hydrogel composite scaffolds with an attenuated immunogenicity component for bone tissue engineering applications

Xenogeneic bones are potential templates for bone regeneration. In this study, decellularized porcine bone powder with attenuated immunogenicity was incorporated into a photocurable hydrogel, gelatin methacryloyl (GelMA), to obtain scaffolds with good mechanical properties for bone tissue engineering. The decellularized bone powder (DCB)-GelMA hybrid scaffolds had higher compressive strength and stiffness values when the DCB content was increased. In vitro evaluations revealed the biocompatibility of these scaffolds. The scaffolds could induce human bone marrow mesenchymal stem cells (hMSCs) to undergo osteogenic differentiation even in the absence of an induction medium. The efficiency of the scaffolds for bone regeneration applications was further evaluated using an in vivo cranial bone defect model in rats. Micro-CT images showed that the hybrid scaffolds with 20% DCB content had the best effect in promoting new bone regeneration. Thus, it was concluded that the DCB-GelMA hybrid scaffolds have high potential in bone tissue engineering applications.

Affinity-bound growth factor within sulfated interpenetrating network bioinks for bioprinting cartilaginous tissues

3D bioprinting has emerged as a promising technology in the field of tissue engineering and regenerative medicine due to its ability to create anatomically complex tissue substitutes. However, it still remains challenging to develop bioactive bioinks that provide appropriate and permissive environments to instruct and guide the regenerative process in vitro and in vivo. In this study alginate sulfate, a sulfated glycosaminoglycan (sGAG) mimic, was used to functionalize an alginate-gelatin methacryloyl (GelMA) interpenetrating network (IPN) bioink to enable the bioprinting of cartilaginous tissues. The inclusion of alginate sulfate had a limited influence on the viscosity, shear-thinning and thixotropic properties of the IPN bioink, enabling high-fidelity bioprinting and supporting mesenchymal stem cell (MSC) viability post-printing. The stiffness of printed IPN constructs greatly exceeded that achieved by printing alginate or GelMA alone, while maintaining resilience and toughness. Furthermore, given the high affinity of alginate sulfate to heparin-binding growth factors, the sulfated IPN bioink supported the sustained release of transforming growth factor-β3 (TGF-β3), providing an environment that supported robust chondrogenesis in vitro, with little evidence of hypertrophy or mineralization over extended culture periods. Such bioprinted constructs also supported chondrogenesis in vivo, with the controlled release of TGF-β3 promoting significantly higher levels of cartilage-specific extracellular matrix deposition. Altogether, these results demonstrate the potential of bioprinting sulfated bioinks as part of a 'single-stage' or 'point-of-care' strategy for regenerating cartilaginous tissues. STATEMENT OF SIGNIFICANCE: This study highlights the potential of using sulfated interpenetrating network (IPN) bioink to support the regeneration of phenotypically stable articular cartilage. Construction of interpenetrating networks in the bioink enables unique high-fidelity bioprinting and provides synergistic increases in mechanical properties. The presence of alginate sulfate enables the capacity of high affinity-binding of TGF-β3, which promoted robust chondrogenesis in vitro and in vivo.

An ex vivo human osteochondral culture model

To reduce animal experimentation and to overcome translational issues in cartilage tissue engineering, there is a need to develop an ex vivo human tissue-based approach. This study aims to demonstrate that a human osteochondral explant at different stages of osteoarthritis (OA) can be kept in long-term culture while preserving its viability and composition. Osteochondral explants with either a smooth or fibrillated cartilage surface, representing different OA stages, were harvested from fresh human tibial plateaus. Explants were cultured for 2 or 4 weeks in a double-chamber culture platform. The biochemical content of the cartilage of cultured explants did not significantly change over a period of 4 weeks and these findings were supported by histology. Chondrocytes mostly preserved their metabolic activity during culture and active bone and marrow were found in the periphery of the explants, while metabolic activity was decreased in the bone core in cultured explants compared to fresh explants. In fibrillated explants, chondrocyte viability decreased in the periphery of the sample in cultured groups compared to fresh explants (fresh, 94 ± 6%; cultured, 64% ± 17%, 2 weeks, and 69% ± 17%, 4 weeks; P < .05). Although biochemical and histological results did not show changes within the cartilage tissue, the viability of the explants should be carefully controlled for each specific use. This system provides an alternative to explore drug treatment and implant performance under more controlled experimental conditions than possible in vivo, in combination with clinically relevant human osteochondral tissue.

Icariin inhibits chondrocyte apoptosis and angiogenesis by regulating the TDP-43 signaling pathway

Background

This study focused on the mechanisms where icariin inhibited chondrocyte apoptosis and angiogenesis by regulating the TDP‐43 signaling pathway.

Methods

A rat osteoarthritis (OA) model was established by collagenase injection. Histological examination of the articular cartilage and synovial tissue was performed 6 weeks after operation. Cartilage cell line overexpressing TDP‐43 and mesenchymal stem cell line (TDP43‐MSCs) of the rat TDP43 gene were established.

Results

In OA rats transplanted with TDP43‐mMSCs, TDP43 was highly expressed in chondrocytes (TDP43‐HC), while TDP43 expression was low in HC and MSCs‐HC (p < 0.05). After the intervention of MSCs‐TDP43, high expression of TDP43 induced the apoptosis and death of chondrocytes. After the addition of icariin, late apoptosis and death of TDP43‐HC were significantly attenuated. Apoptosis and death of HC, MSCs‐HC, and TDP43‐HC cells were effectively controlled with icariin, and no apparent cell death was found. ELISA showed that the VEGF and HIF‐1 alpha were significantly higher in the rat OA model than the normal control rats.

Conclusion

TDP43‐MSC transplantation interfered with the expression of TDP43 in the articular chondrocytes of OA rats, which may impact on inducing apoptosis of chondrocytes as well as inhibiting the proliferation of chondrocytes. Additionally, TDP43‐MSCs appeared to promote the formation of neovascularization in the synovial tissue, which could be significantly attenuated by icariin.