Advanced hydrogels for the repair of cartilage defects and regeneration

Cartilage defects are one of the most common symptoms of osteoarthritis(OA),a degenerative disease that affects millions of people world-wide and places a significant socio-economic burden on society.Hydrogels,which are a class of biomaterials that are elastic,and display smooth surfaces while exhibiting high water content,are promising candidates for cartilage regeneration.In recent years,various kinds of hydrogels have been developed and applied for the repair of cartilage defects in vitro or in vivo,some of which are hopeful to enter clinical trials.In this review,recent research findings and developments of hydrogels for cartilage defects repair are summarized.We discuss the principle of cartilage regeneration,and outline the requirements that have to be fulfilled for the deployment of hydrogels for medical applications.We also highlight the development of advanced hydrogels with tailored properties for different kinds of cartilage defects to meet the requirements of cartilage tissue engineering and precision medicine.

Repairing cartilage defects using chondrocyte and osteoblast composites developed using a bioreactor

Background Articular cartilage injury is a common disease, and the incidence of articular wear, degeneration, trauma and sports injury is increasing, which often lead to disability and reduced quality of life. Unfortunately repair of articular cartilage defects do not always provide satisfactory outcomes. Methods Chondrocyte and osteoblast composites were co-cultured using a bioreactor. The cartilage defects were treated with cell-β-tricalcium phosphate （β-TCP） composites implanted into osteochondral defects in dogs, in vivo, using mosaicplasty, by placing chondrocyte-β-TCP scaffold composites on top of the defect and osteoblast-β-TCP scaffold composites below the defect.Results Electron microscopy revealed that the induced chondrocytes and osteoblast showed fine adhesive progression and proliferation in the β-TCP scaffold. The repaired tissues in the experimental group maintained their thickness to the full depth of the original defects, as compared with the negative control group （q=12.3370, P 〈0.01; q=31.5393, P 〈0.01）. Conclusions Perfusion culture provided sustained nutrient supply and gas exchange into the center of the large scaffold. This perfusion bioreactor enables the chondrocytes and osteoblasts to survive and proliferate in a three-dimensional scaffold.

Accurate 3D Reconstruction of Subject-Specific Knee Finite Element Model to Simulate the Articular Cartilage Defects

The biomechanical relationship between the articular cartilage defect and knee osteoarthritis (OA) has not been clearly defined. This study presents a 3D knee finite element model (FEM) to determine the effect of cartilage defects on the stress distribution around the defect rim. The complete knee FEM, which includes bones, articular cartilages, menisci and ligaments, is developed from computed tomography and magnetic resonance images. This FEM then is validated and used to simulate femoral cartilage defects. Based on the obtained results, it is confirmed that the 3D knee FEM is reconstructed with high-fidelity level and can faithfully predict the knee contact behavior. Cartilage defects drastically affect the stress distribution on articular cartilages. When the defect size was smaller than 1.00cm2, the stress elevation and redistribution were found undistinguishable. However, significant stress elevation and redistribution were detected due to the large defect sizes ( 1.00cm2). This alteration of stress distribution has important implications relating to the progression of cartilage defect to OA in the human knee joint.

Nanocomposite Hydrogel Materials for Defective Cartilage Repair and Its Mechanical Tribological Behavior—A Review

Osteoarthritis(OA)is a regressive ailment that affects a large population of patients.The most common symptoms of OA in humans are cartilage abnormalities.Hydrogels are excellent candidates for cartilage regeneration and are widely accepted as implants.In the past few decades,numerous types of hydrogels have been synthesized to repair cartilage defects.This study highlights recent advances in hydrogel development for the treatment of cartilage defects.In addition,the detailed progression of tailored nanocomposite hydrogels is summarized,and emphasis has been placed on the mechanical properties,especially the tribological behavior of the developed nanocomposite hydrogels.

In Vitro Targeted Magnetic Delivery and Tracking of Superparamagnetic Iron Oxide Particles Labeled Stem Cells for Articular Cartilage Defect Repair

To assess a novel cell manipulation technique of tissue engineering with respect to its ability to augment superparamagnetic iron oxide particles （SPIO） labeled mesenchymal stem cells （MSCs） density at a localized cartilage defect site in an in vitro phantom by applying magnetic force. Meanwhile, non-invasive imaging techniques were use to track SPIO-labeled MSCs by magnetic resonance imaging （MRI）. Human bone marrow MSCs were cultured and labeled with SPIO. Fresh degenerated human osteochondral fragments were obtained during total knee arthroplasty and a cartilage defect was created at the center. Then, the osteochondral fragments were attached to the sidewalls of culture flasks filled with phosphate-buffered saline （PBS） to mimic the human joint cavity. The SPIO-labeled MSCs were injected into the culture flasks in the presence of a 0.57 Tesla （T） magnetic force. Before and 90 min after cell targeting, the specimens underwent T2-weighted turbo spin-echo （SET2WI） sequence of 3.0 T MRI. MRI results were compared with histological findings. Macroscopic observation showed that SPIO-labeled MSCs were steered to the target region of cartilage defect. MRI revealed significant changes in signal intensity （P0.01）. HE staining exibited that a great number of MSCs formed a three-dimensional （3D） cell ＂sheet＂ structure at the chondral defect site. It was concluded that 0.57 T magnetic force permits spatial delivery of magnetically labeled MSCs to the target region in vitro. High-field MRI can serve as an very sensitive non-invasive technique for the visualization of SPIO-labeled MSCs.

Repair of a large patellar cartilage defect using human umbilical cord blood-derived mesenchymal stem cells:A case report

BACKGROUND Patellar dislocation may cause cartilage defects of various sizes.Large defects commonly require surgical treatment;however,conventional treatments are problematic.CASE SUMMARY A 15-year-old male with a large patellar cartilage defect due to patellar dislocation was treated via human umbilical cord blood-derived mesenchymal stem cell(hUCB-MSC)implantation.To our knowledge,this is the first report of this treatment for this purpose.The patient recovered well as indicated by good visual analog scale,International Knee Documentation Committee and McMaster Universities Osteoarthritis Index scores.Magnetic resonance imaging showed cartilage regeneration 18 mo postoperatively.CONCLUSION Umbilical cord blood-derived hUCB-MSCs may be a useful treatment option for the repair of large patellar cartilage defects.

Expression of Transforming Growth Factor β_1 in Mesenchymal Stem Cells: Potential Utility in Molecular Tissue Engineering for Osteochondral Repair

Summary: The feasibility of using gene therapy to treat full-thickness articular cartilage defects was investigated with respect to the transfection and expression of exogenous transforming growth factor (TGF)-β 1 genes in bone marrow-derived mesenchymal stem cells (MSCs) in vitro. The full-length rat TGF-β 1 cDNA was transfected to MSCs mediated by lipofectamine and then selected with G418, a synthetic neomycin analog. The transient and stable expression of TGF-β 1 by MSCs was detected by using immunohistochemical staining. The lipofectamine-mediated gene therapy efficiently transfected MSCs in vitro with the TGF-β 1 gene causing a marked up-regulation in TGF-β 1 expression as compared with the vector-transfected control groups, and the increased expression persisted for at least 4 weeks after selected with G418. It was suggested that bone marrow-derived MSCs were susceptible to in vitro lipofectamine mediated TGF-β 1 gene transfer and that transgene expression persisted for at least 4 weeks. Having successfully combined the existing techniques of tissue engineering with the novel possibilities offered by modern gene transfer technology, an innovative concept, i.e. molecular tissue engineering, are put forward for the first time. As a new branch of tissue engineering, it represents both a new area and an important trend in research. Using this technique, we have a new powerful tool with which: (1) to modify the functional biology of articular tissue repair along defined pathways of growth and differentiation and (2) to affect a better repair of full-thickness articular cartilage defects that occur as a result of injury and osteoarthritis.

Molecular Tissue Engineering: Applications for Modulation of Mesenchymal Stem Cells Proliferation by Transforming Growth Factor β_1 Gene Transfer

The effect of transforming growth factor β 1 (TGF β 1 ) gene transfection on the proliferation of bone marrow derived mesenchymal stem cells (MSC S ) and the mechanism was investigated to provide basis for accelerating articular cartilage repairing using molecular tissue engineering technology. TGF β 1 gene at different doses was transduced into the rat bone marrow derived MSCs to examine the effects of TGF β 1 gene transfection on MSCs DNA synthesis, cell cycle kinetics and the expression of proliferating cell nuclear antigen (PCNA). The results showed that 3 μl lipofectamine mediated 1 μg TGF β 1 gene transfection could effectively promote the proliferation of MSCs best; Under this condition (DNA/Lipofectamine=1μg/3μl), flow cytometry and immunohistochemical analyses revealed a significant increase in the 3 H incorporation, DNA content in S phase and the expression of PCNA. Transfection of gene encoding TGF β 1 could induce the cells at G0/G1 phase to S1 phase, modulate the replication of DNA through the enhancement of the PCNA expression, increase the content of DNA at S1 phase and promote the proliferation of MSCs. This new molecular tissue engineering approach could be of potential benefit to enhance the repair of damaged articular cartilage, especially those caused by degenerative joint diseases.

Hydrogel platform with tunable stiffness based on magnetic nanoparticles cross-linked GelMA for cartilage regeneration and its intrinsic biomechanism

Cartilage injury affects numerous individuals,but the efficient repair of damaged cartilage is still a problem in clinic.Hydrogel is a potent scaffold candidate for tissue regeneration,but it remains a big challenge to improve its mechanical property and figure out the interaction of chondrocytes and stiffness.Herein,a novel hybrid hydrogel with tunable stiffness was fabricated based on methacrylated gelatin(GelMA)and iron oxide nanoparticles(Fe_(2)O_(3))through chemical bonding.The stiffness of Fe_(2)O_(3)/GelMA hybrid hydrogel was controlled by adjusting the concentration of magnetic nanoparticles.The hydrogel platform with tunable stiffness modulated its cellular properties including cell morphology,microfilaments and Young’s modulus of chondrocytes.Interestingly,Fe_(2)O_(3)/GelMA hybrid hydrogel promoted oxidative phosphorylation of mitochondria and facilitated catabolism of lipids in chondrocytes.As a result,more ATP and metabolic materials generated for cellular physiological activities and organelle component replacements in hybrid hydrogel group compared to pure GelMA hydrogel.Furthermore,implantation of Fe_(2)O_(3)/GelMA hybrid hydrogel in the cartilage defect rat model verified its remodeling potential.This study provides a deep understanding of the bio-mechanism of Fe_(2)O_(3)/GelMA hybrid hydrogel interaction with chondrocytes and indicates the hydrogel platform for further application in tissue engineering.

3D-printed fish gelatin scaffolds for cartilage tissue engineering

Knee osteoarthritis is a chronic disease caused by the deterioration of the knee joint due to various factors such as aging,trauma,and obesity,and the nonrenewable nature of the injured cartilage makes the treatment of osteoarthritis challenging.Here,we present a three-dimensional(3D)printed porous multilayer scaffold based on cold-water fish skin gelatin for osteoarticular cartilage regeneration.To make the scaffold,cold-water fish skin gelatin was combined with sodium alginate to increase viscosity,printability,and mechanical strength,and the hybrid hydrogel was printed according to a pre-designed specific structure using 3D printing technology.Then,the printed scaffolds underwent a double-crosslinking process to enhance their mechanical strength even further.These scaffolds mimic the structure of the original cartilage network in a way that allows chondrocytes to adhere,proliferate,and communicate with each other,transport nutrients,and prevent further damage to the joint.More importantly,we found that cold-water fish gelatin scaffolds were nonimmunogenic,nontoxic,and biodegradable.We also implanted the scaffold into defective rat cartilage for 12 weeks and achieved satisfactory repair results in this animal model.Thus,cold-water fish skin gelatin scaffolds may have broad application potential in regenerative medicine.

Biodegradable Thermogel as Culture Matrix of Bone Marrow Mesenchymal Stem Cells for Potential Cartilage Tissue Engineering

Poly（lactide-co-glycolide）-poly（ethylene glycol）-poly（lactide-co-glycolide）（PLGA-PEG-PLGA） triblock copolymer was synthesized through the ring-opening polymerization of LA and GA with PEG as macroinitiator and stannous octoate as catalyst. The amphiphilic copolymer self-assembled into micelles in aqueous solutions, and formed hydrogels as the increase of temperature at relatively high concentrations（〉 15 wt%）. The favorable degradability of the hydrogel was confirmed by in vitro and in vivo degradation experiments. The good cellular and tissular compatibilities of the thermogel were demonstrated. The excellent adhesion and proliferation of bone marrow mesenchymal stem cells endowed PLGA-PEGPLGA thermogelling hydrogel with fascinating prospect for cartilage tissue engineering.