Rapidly dissociated autologous meniscus tissue enhances meniscus healing: An in vitro study

Development of Biphasic Injectable Hydrogels for Meniscus Scaffold from Photocrosslinked Glycidyl Methacrylate-Modified Poly(Vinyl Alcohol)/Glycidyl Methacrylate-Modified Silk Fibroin

The development of a hydrogel material with a modified chemical structure of poly(vinyl alcohol) (PVA) and silk fibroin (SF) using glycidyl methacrylate (GMA) (denoted as PVA-g-GMA and SF-g-GMA) is an innovative approach in the field of biomaterials and meniscus tissue engineering in this study. The PVA-g-GMA/SF-g-GMA hydrogel was fabricated using different ratios of PVA-g-GMA to SF-g-GMA: 100/0, 75/25, 50/50, 25/75, and 0/100 (w/w of dry substances), using lithium phenyl (2,4,6-trimethylbenzoyl)phosphinate (LAP) as a free radical photoinitiator, for 10 min at a low ultraviolet (UV) intensity (365 nm, 6 mW/cm2). The mechanical properties, morphology, pore size, and biodegradability of the PVA-g-GMA/SF-g-GMA hydrogel were investigated. Finally, for clinical application, human chondrocyte cell lines (HCPCs) were mixed into PVA-g-GMA/SF-g-GMA solutions and fabricated into hydrogel to study the viability of live and dead cells and gene expression. The results indicate that as the SF-g-GMA content increased, the compressive modulus of the PVA-g-GMA/SF-g-GMA hydrogel dropped from approximately 173 to 11 kPa. The degradation rates of PVA-g-GMA/SF-g-GMA 100/0, 75/25, and 50/50 reached up to 15.61%, 17.23%, and 18.93% in 4 months, respectively. In all PVA-g-GMA/SF-g-GMA conditions on day 7, chondrocyte cell vitality exceeded 80%. The PVA-g-GMA/SF-g-GMA 75:25 and 50:50 hydrogels hold promise as a biomimetic biphasic injectable hydrogel for encapsulated augmentation, offering advantages in terms of rapid photocurability, tunable mechanical properties, favorable biological responses, and controlled degradation.

Reinforcement of Injectable Hydrogel for Meniscus Tissue Engineering by Using Cellulose Nanofiber from Cassava Pulp

Injectable hydrogels can be applied to treat damaged meniscus in minimally invasive conditions. Generally, injectable hydrogels can be prepared from various polymers such as polycaprolactone (PCL) and poly (N-isopropylacrylamide) (PNIPAAm). Poly (ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer-diacrylate (PEO-PPO-PEO-DA) is an interesting polymer due to its biodegradability and can be prepared as water-insoluble injectable hydrogel after curing with UV light at low intensity. However, mechanical and cell adhesion properties are not optimal for these hydrogels. For the improved mechanical performance of the injectable hydrogel, cellulose nanofiber (CNF) extracted from cassava pulp was used as a reinforcing filler in this study. In addition, gelatin methacrylate (GelMA), the denatured form of collagen was used to enhance cell adhesion. PEO-PPO-PEO-DA/CNF/GelMA injectable hydrogels were prepared with 2-hydroxy-1-(4-(hydroxy ethoxy) phenyl)-2-methyl-1-propanone as a photoinitiator and then cured with UV light, 365 nm at 6 mW/cm². Physicochemical characteristics of the hydrogels and hydrogels with CNF were studied in detail including morphology characterization, pore size diameter, porosity, mechanical properties, water uptake, and swelling. In addition, cell viability was also studied. CNF-reinforced injectable hydrogels were successfully prepared after curing with UV light within 10 min with a thickness of 2 mm. CNF significantly improved the mechanical characteristics of injectable hydrogels. The incorporation of GelMA into the injectable hydrogels improved the viability of human cartilage stem/progenitor cells. At optimum formulation, 12%PEO-PPO-PEO-DA/0.5%CNF/3%GelMA injectable hydrogels significantly promoted cell viability (>80%) and also showed good physicochemical properties, which met tissue engineering requirements. In summary, this work shows that these novel injectable hydrogels have the potential for meniscus tissue engineering.

Applications and prospects of different functional hydrogels in meniscus repair

The meniscus is a kind of fibrous cartilage structure that serves as a cushion in the knee joint to alleviate the mechanical load. It is commonly injured, but it cannot heal spontaneously. Traditional meniscectomy is not currently recommended as this treatment tends to cause osteoarthritis. Due to their good biocompatibility and versatile regulation, hydrogels are emerging biomaterials in tissue engineering. Hydrogels are excellent candidates in meniscus rehabilitation and regeneration because they are fine-tunable, easily modified, and capable of delivering exogenous drugs, cells, proteins, and cytokines. Various hydrogels have been reported to work well in meniscus-damaged animals, but few hydrogels are effective in the clinic, indicating that hydrogels possess many overlooked problems. In this review, we summarize the applications and problems of hydrogels in extrinsic substance delivery, meniscus rehabilitation, and meniscus regeneration. This study will provide theoretical guidance for new therapeutic strategies for meniscus repair.

Explant models for meniscus metabolism, injury, repair, and healing

Purpose/Aim: Knee meniscus is a wedge-shaped fibrocartilaginous tissue, playing important roles in maintaining joint stability and function. Injuries to the meniscus, particularly with the avascular inner third zone, hardly heal and frequently progress into structural breakdown, followed by the initiation of osteoarthritis. As the importance of meniscus in joint function and diseases is being recognized, the field of meniscus research is growing. Not only development, biology, and metabolism but also injury, repair, and healing of meniscus are being actively investigated. As meniscus functions as an integrated unit of a knee joint, in vivo models with various species have been the predominant method for studying meniscus pathophysiology and for testing healing/regeneration strategies. However, in vivo models for meniscus studies suffer from low reproducibility and high cost. To complement the limitations of in vivo animal models, several types of meniscus explants have been applied as highly controlled, standardized in vitro models to investigate meniscus metabolism, pathophysiology, and repair or regeneration process. This review summarizes and compares the existing meniscus explant models. We also discuss the advantages and disadvantages of each explant model.Conclusion: Despite few outstanding challenges, meniscus explant models have potential to serve as an effective tool for investigations of meniscus metabolism, injury, repair and healing.

Chondrocyte-based intraoperative processing strategies for the biological augmentation of a polyurethane meniscus replacement

Purpose/aim of study: Menisectomies account for over 1.5 million surgical interventions in Europe annually, and there is a growing interest in regenerative strategies to improve outcomes in meniscal replacement. The overall objective of this study was to evaluate the role of intraoperatively applied fresh chondrocyte (FC) isolates compared to minced cartilage (MC) fragments, used without cell isolation, to improve bioactivity and tissue integration when combined with a polyurethane replacement.

MATERIALS AND METHODS

First, to optimize the intraoperative cell isolation protocol, caprine articular cartilage biopsies were digested with 750 U/ml or 3000 U/ml collagenase type II (ratio of 10 ml per g of tissue) for 30 min, 1 h or 12 h with constant agitation and compared to culture-expanded chondrocytes in terms of matrix deposition when cultured on polyurethane scaffolds. Finally, FCs and MC-augmented polyurethane scaffolds were evaluated in a caprine meniscal explant model to assess the potential enhancements on tissue integration strength.

RESULTS

Adequate numbers of FCs were harvested using a 30 min chondrocyte isolation protocol and were found to demonstrate improved matrix deposition compared to standard culture-expanded cells in vitro. Upon evaluation in a meniscus explant defect model, both FCs and MC showed improved matrix deposition at the tissue-scaffold interface and enhanced push-out strength, fourfold and 2.5-fold, respectively, compared with the acellular implant.

CONCLUSIONS

Herein, we have demonstrated a novel approach that could be applied intraoperatively, using FCs or MC for improved tissue integration with a polyurethane meniscal replacement.

Porous Poly(vinyl alcohol)-Based Hydrogel for Knee Meniscus Functional Repair

The meniscus has a key role within the knee joint, conferring stability, absorbing and redistributing loads, and influencing the overall movement proprioception. Recent developments in the treatment of meniscal injury have progressively shifted the focus from general resection to functional repair, with the recognition that restoring the biomechanical meniscal function helps to prevent degenerative changes in the knee joint and the insurgence of osteoarthritis. To address this clinical need, we have developed a biomimetic implant based on a porous poly(vinyl alcohol) (PVA) hydrogel. Such hydrogels are stable, biocompatible, and suitable to surgical translation, and their mechanical properties can be tuned to reduce the mismatch in the case of partial meniscectomy. The PVA implant structure is porous and permeable, allowing fluid flows and facilitating anatomical integration in situ. Here, we present a chemo-physical characterization of PVA porous hydrogels, focusing on their tunable morphology and associated viscoelastic properties. Biocompatibility was evaluated using primary bovine meniscal fibrochondrocytes, and integration with native tissues was assessed in an ex vivo model. Overall, our results suggest that a synthetic meniscal implant based on a porous PVA hydrogel could restore the physiological function of the meniscus and represent a promising clinical alternative to current resection treatments.