A Gelatin-Hyaluronic Acid Double Cross-Linked Hydrogel for Regulating the Growth and Dual Dimensional Cartilage Differentiation of Bone Marrow Mesenchymal Stem Cells

An in situ forming cartilage matrix mimetic hydrogel scavenges ROS and ameliorates osteoarthritis after superficial cartilage injury

Superficial cartilage defects represent the most prevalent type of cartilage injury encountered in clinical settings, posing significant treatment challenges. Here, we fabricated a cartilage extracellular matrix mimic hydrogel (GHC, consisting of Gelatin, Hyaluronic acid, and Chondroitin sulfate) to avoid the exacerbation of cartilage deterioration, which is often driven by the accumulation of reactive oxygen species (ROS) and a pro-inflammatory microenvironment. The GHC hydrogel exhibited multifunctional properties, including in situ formation, tissue adhesiveness, anti-ROS capabilities, and the promotion of chondrogenesis. The enhancement of tissue adhesion was achieved by chemically modifying hyaluronic acid and chondroitin sulfate with o-nitrobenzene, enabling a covalent connection to the cartilage surface upon light irradiation. In vitro characterization revealed that GHC hydrogel facilitated chondrocyte adhesion, migration, and differentiation into cartilage. Additionally, GHC hydrogels demonstrated the ability to scavenge ROS in vitro and inhibit the production of inflammatory factors by chondrocytes. In the animal model of superficial cartilage injury, the hydrogel effectively promoted cartilage ECM regeneration and facilitated the interface integration between the host tissue and the material. These findings suggest that the multifunctional GHC hydrogels hold considerable promise as a strategy for cartilage defect repair. STATEMENT OF SIGNIFICANCE: Superficial cartilage defects represent the most prevalent type of cartilage injury encountered in the clinic. Previous cartilage tissue engineering materials are only suitable for full-thickness cartilage defects or osteochondral defects. Here, we developed a multifunctional GHC hydrogel composed of gelatin, hyaluronic acid, and chondroitin sulfate, which are natural cartilage extracellular matrix components. The drug-free and cell-free hydrogel not only avoids immune rejection and drug toxicity, but also shows good mechanical properties and biocompatibility. More importantly, the GHC hydrogel could adhere tightly to the superficial cartilage defects and promote cartilage regeneration while protecting against oxidation. This natural ingredients and multifunctional hydrogel is a potential material for repairing superficial cartilage defects.

Application of gelatin-based composites in bone tissue engineering

Natural bone tissue has the certain function of self-regeneration and repair, but it is difficult to repair large bone damage. Recently, although autologous bone grafting is the "gold standard" for improving bone repair, it has high cost, few donor sources. Besides, allogeneic bone grafting causes greater immune reactions, which hardly meet clinical needs. The bone tissue engineering (BTE) has been developed to promote bone repair. Gelatin, due to its biocompatibility, receives a great deal of attention in the BTE research field. However, the disadvantages of natural gelatin are poor mechanical properties and single structural property. With the development of BTE, gelatin is often used in combination with a range of natural, synthetic polymers, and inorganic materials to achieve synergistic effects for the complex physiological process of bone repair. The review delves into the fundamental structure and unique properties of gelatin, as well as the excellent properties necessary for bone scaffold materials. Then this review explores the application of modified gelatin three-dimensional (3D) scaffolds with various structures in bone repair, including 3D fiber scaffolds, hydrogels, and nanoparticles. In addition, the review focuses on the excellent efficacy of composite bone tissue scaffolds consisting of modified gelatin, various natural or synthetic polymeric materials, as well as bioactive ceramics and inorganic metallic/non-metallic materials in the repair of bone defects. The combination of these gelatin-based composite scaffolds provides new ideas for the design of scaffold materials for bone repair with good biosafety.

Spatiotemporal Modulated Scaffold for Endogenous Bone Regeneration via Harnessing Sequentially Released Guiding Signals

The design of a scaffold that can regulate the sequential differentiation of bone marrow mesenchymal stromal cells (BMSCs) according to the endochondral ossification (ECO) mechanism is highly desirable for effective bone regeneration. In this study, we successfully fabricated a dual-networked composite hydrogel composed of gelatin and hyaluronic acid (termed GCDH-M), which can sequentially release chondroitin sulfate (CS) and magnesium/silicon (Mg/Si) ions to provide spatiotemporal guidance for chondrogenesis, angiogenesis, and osteogenesis. The fast release of CS is from the GCDH hydrogel, and the sustained releases of Mg/Si ions are from poly(lactide-co-glycolide) microspheres embedded in the hydrogel. There is a difference in the release rates between CS and ions, resulting in the ability for the fast release of CS and sustained release of ions. The dual networks between the modified gelatin and hyaluronic acid via covalent bonding and host-guest interactions render the hydrogel with some dynamic feature to meet the differentiation development of BMSCs laden inside the hydrogel, i.e., transforming into a chondrogenic phenotype, further to a hypertrophic phenotype and eventually to an osteogenic phenotype. As evidenced by the results of in vitro and in vivo evaluations, this GCDH-M composite hydrogel was proved to be able to create an optimal microenvironment for embedded BMSCs responding to the sequential guiding signals, which aligns with the rhythm of the ECO process and ultimately boosts bone regeneration. The promising outcome achieved with this innovative hydrogel system sheds light on novel scaffold design targeting bone tissue engineering.

Fabrication and characterization of porous, degradable, biocompatible poly(vinyl alcohol)/tannic acid/gelatin/hyaluronic acid hydrogels with good mechanical properties for cartilage tissue engineering

At present, articular cartilage repair and regeneration remain still one of the most concerned problems due to its poor self-healing capacity. Among the tissue engineering materials, hydrogel is considered an ideal candidate due to its similarity to extracellular matrices. Despite the good biocompatibility of gelatin and hyaluronic acid hydrogels, they are still limited to serve as tissue engineering materials by fast degradation rate and poor mechanical performances. In order to solve these problems, novel polyvinyl alcohol/tannic acid/gelatin/hyaluronic acid (PTGH) hydrogels are prepared by a facile physical crosslinked method. The PTGH hydrogels exhibit a high moisture content (85%) and porosity (87%). Meanwhile, the porous microstructures and mechanical properties (compressive strength: 0.85-2.59 MPa; compressive modulus: 57.88-124.27 kPa) can be controlled by adjusting the mass ratio of PT/GH. In vitro degradation analysis shows that the PTGH hydrogels can be degraded gradually in PBS solution with the presence of lysozyme. For this gel system, based on the hydrogen bonds among molecules, it improved the mechanical properties of gelatin and hyaluronic acid hydrogels. With the degradation of PTGH hydrogels, the release of gelatin and hyaluronic acid can have a continuous effort for the cartilage tissue regeneration and repair. In addition, in vitro cell culture results show that the PTGH hydrogels have no negative effects on chondrocytes growth and proliferation. In all, the PTGH hydrogels exhibit potential applications for articular cartilage tissue repair and regeneration.

Gelatin/Hyaluronic Acid Photocrosslinked Double Network Hydrogel with Nano-Hydroxyapatite Composite for Potential Application in Bone Repair

The application of hydrogels in bone repair is limited due to their low mechanical strength. Simulating bone extracellular matrix, methylacrylylated gelatin (GelMA)/methylacrylylated hyaluronic acid (HAMA)/nano-hydroxyapatite(nHap) composite hydrogels were prepared by combining the double network strategy and composite of nHap in this study. The precursor solutions of the composite hydrogels were injectable due to their shear thinning property. The compressive elastic modulus of the composite hydrogel was significantly enhanced, the fracture strength of the composite hydrogel nearly reached 1 MPa, and the composite hydrogel retained its high water content at above 88%. The composite hydrogels possess good compatibility with BMSCS and have the potential to be used as injectable hydrogels for bone defect treatment.

Designing functional hyaluronic acid-based hydrogels for cartilage tissue engineering

Damage to cartilage tissues is often difficult to repair owing to chronic inflammation and a lack of bioactive factors. Therefore, developing bioactive materials, such as hydrogels acting as extracellular matrix mimics, that can inhibit the inflammatory microenvironment and promote cartilage repair is crucial. Hyaluronic acid, which exists in cartilage and synovial fluid, has been extensively investigated for cartilage tissue engineering because of its promotion of cell adhesion and proliferation, regulation of inflammation, and enhancement of cartilage regeneration. However, hyaluronic acid-based hydrogels have poor degradation rates and unfavorable mechanical properties, limiting their application in cartilage tissue engineering. Recently, various multifunctional hyaluronic acid-based hydrogels, including alkenyl, aldehyde, thiolated, phenolized, hydrazide, and host–guest group-modified hydrogels, have been extensively studied for use in cartilage tissue engineering. In this review, we summarize the recent progress in the multifunctional design of hyaluronic acid-based hydrogels and their application in cartilage tissue engineering. Moreover, we outline the future research prospects and directions in cartilage tissue regeneration. This would provide theoretical guidance for developing hyaluronic acid-based hydrogels with specific properties to satisfy the requirements of cartilage tissue repair.

Analysis the Lateral Tunnel Position of the Bone Graft and Regeneration of Femur by CT Tunnel Localization

Objective: To analyze, in a retrospective study, the lateral tunnel position of the graft femur by CT after arthroscopic ACL reconstruction via the anteromedial (AM) approach and the tunnel angle shown on X-ray. Methods and Materials: 60 patients undergoing arthroscopic ACL reconstruction via AM approach with 4 femoral hamstring tendon grafts were investigated from October 2019 to October 2021. Postoperative orthogonal x-rays and computed tomography (CT) scans were obtained, and the position of the femoral tunnel obtained after CT reconstruction was correlated with the Bernard-Hertel grid. The angle of the resulting femoral tunnel on the orthogonal x-ray was analyzed against the CT tunnel position. Results: In the study, the anterior–posterior orientation was forward (P = 0.001) and the high-low orientation was similar (taken as 20%, P = 0.066) or slightly higher (taken as 21%, P = 0.025) compared to the AM beam localization in the two-beam reconstruction. Overall, the femoral tunnel angle on non-weight-bearing orthogonal x-ray was negatively correlated with the anterior–posterior (AP) position of the femoral tunnel centre as shown on CT (P = 0.004, r =−0.368) and positively, but weakly, correlated with the high-low (HL) position (P = 0.049, r = 0.254). Conclusion: Non-weight-bearing orthogonal X-rays only can make approximate predictions about the distribution of anatomical reconstruction, I.D.E.A.L reconstruction.

A bioinspired and high-strengthed hydrogel for regeneration of perforated temporomandibular joint disc: Construction and pleiotropic immunomodulatory effects

Due to the lack of an ideal material for TMJ (temporomandibular joint) disc perforation and local inflammation interfering with tissue regeneration, a functional TGI/HA-CS (tilapia type I gelatin/hyaluronic acid-chondroitin sulfate) double network hydrogel was constructed in this paper. It was not only multiply bionic in its composition, structure and mechanical strength, but also endowed with the ability to immunomodulate microenvironment and simultaneously induce in situ repair of defected TMJ discs. On the one hand, it inhibited inflammatory effects of inflammasome in macrophages, reduced the extracellular matrix (ECM)-degrading enzymes secreted by chondrocytes, reversed the local inflammatory state, promoted the proliferation of TMJ disc cells and induced fibrochondrogenic differentiation of synovium-derived mesenchymal stem cells (SMSCs). On the other hand, it gave an impetus to repairing a relatively-large (6 mm-sized) defect in mini pigs' TMJ discs in a rapid and high-quality manner, which suggested a promising clinical application.

Biomimetic hydrogel scaffolds via enzymatic reaction for cartilage tissue engineering

Objective

We aimed to evaluate cytocompatibility of hyaluronic acid (HA) and gelatin (Gela) conjugation with phenolic groups (Phs) via enzyme-mediated crosslinking. Phenolic moieties were substituted on the backbone of HA (HA-Ph) and Gela (Gela-Ph) and subsequently were subjected for horseradish peroxidase crosslinking in the presence of H₂O₂ as an electron donor to create a stable hybrid microenvironment for cellular behavior and cartilage tissue engineering.

Results

Successful synthesis of biopolymers confirmed by NRM and UV–Vis spectrophotometry. The physical characteristic of hydrogels including mechanical properties and water contact angle of hydrogels enhanced with addition of Gela-Ph in HA-based hydrogel. The Gela-Ph showed longest gelation time and highest degradation rate. The cellular studies showed cells did not attach to HA-Ph hydrogel. While, proper cell attachment and proliferation observed on blend hydrogel surface compared with the neat hydrogels which interpret by the existence of cell-adhesive motifs of utilized Gela-Ph in this hydrogel. The encapsulated cells in HA-Ph hydrogel were spheroid and just maintained their viability. Hydrogels containing Gela-Ph, the cells were spindle shape with high degrees of cytoplasmic extension. Overall, the results suggest that hybrid biomimetic hydrogel can provide a superior biological microenvironment for chondrocytes in 3D cartilage tissue engineering.

Three-Dimensional Printing Self-Healing Dynamic/Photocrosslinking Gelatin-Hyaluronic Acid Double-Network Hydrogel for Tissue Engineering

Three-dimensional (3D) printing technology has great potential for constructing structurally and functionally complex scaffold materials for tissue engineering. Bio-inks are a critical part of 3D printing for this purpose. In this study, based on dynamic hydrazone-crosslinked hyaluronic acid (HA-HYD) and photocrosslinked gelatin methacrylate (GelMA), a double-network (DN) hydrogel with significantly enhanced mechanical strength, self-healing, and shear-thinning properties was developed as a printable hydrogel bio-ink for extrusion-based 3D printing. Owing to shear thinning, the DN hydrogel bio-inks could be extruded to form uniform filaments, which were printed layer by layer to fabricate the scaffolds. The self-healing performance of the filaments and photocrosslinking of GelMA worked together to obtain an integrated and stable printed structure with high mechanical strength. The in vitro cytocompatibility assay showed that the DN hydrogel printed scaffolds supported the survival and proliferation of bone marrow mesenchymal stem cells. GelMA/HA-HYD DN hydrogel bio-inks with printability, good structural integrity, and biocompatibility are promising materials for 3D printing of tissue engineering scaffolds.

A Rapid Self-Assembly Peptide Hydrogel for Recruitment and Activation of Immune Cells

Self-assembly peptide nanotechnology has attracted much attention due to its regular and orderly structure and diverse functions. Most of the existing self-assembly peptides can form aggregates with specific structures only under specific conditions and their assembly time is relatively long. They have good biocompatibility but no immunogenicity. To optimize it, a self-assembly peptide named DRF3 was designed. It contains a hydrophilic and hydrophobic surface, using two N-terminal arginines, leucine, and two c-terminal aspartate and glutamic acid. Meanwhile, the c-terminal of the peptide was amidated, so that peptide segments were interconnected to increase diversity. Its characterization, biocompatibility, controlled release effect on antigen, immune cell recruitment ability, and antitumor properties were examined here. Congo red/aniline blue staining revealed that peptide hydrogel DRF3 could be immediately gelled in PBS. The stable β-sheet secondary structure of DRF3 was confirmed by circular dichroism spectrum and IR spectra. The observation results of cryo-scanning electron microscopy, transmission electron microscopy, and atomic force microscopy demonstrated that DRF3 formed nanotubule-like and vesicular structures in PBS, and these structures interlaced with each other to form ordered three-dimensional nanofiber structures. Meanwhile, DRF3 showed excellent biocompatibility, could sustainably and slowly release antigens, recruit dendritic cells and promote the maturation of dendritic cells (DCs) in vitro. In addition, DRF3 has a strong inhibitory effect on clear renal cell carcinoma (786-0). These results provide a reliable basis for the application of peptide hydrogels in biomedical and preclinical trials.