Regeneration of articular cartilage defects: Therapeutic strategies and perspectives

Bionic ECM scaffolds for directional articular hyaline cartilage regeneration and long-term homeostasis maintenance

Cartilage defects play a key role in osteoarthritis, causing functional impairment as the disease progresses. Microfracture surgery is commonly used to treat articular cartilage defects, providing early pain relief and functional improvement. However, the blood clot formed during the procedure differs from the natural cartilage microenvironment, hindering hyaline cartilage formation and promoting fibrocartilage, which limits long-term outcomes. This study proposes combining a bionic flexible extracellular matrix (ECM) scaffold with microfracture surgery as a treatment for cartilage defects. By filling the microfracture site with the scaffold and thermosensitive agarose gel, we can anchor BMSCs leaking from the bone marrow while creating a 3D microenvironment that regulates stem cell differentiation. Our results show that the scaffold's mechanical strength is comparable to that of hyaline cartilage, offering excellent biomimetic properties and biocompatibility. In vitro, BMSCs migrating into the scaffold exhibited a survival rate of nearly 90 % by day 2, significantly higher than the 25 % survival rate in the control agarose gel group, with cells observed anchoring around the scaffold. In vivo, stem cells anchored to the scaffold successfully differentiated into articular hyaline cartilage, driven by the combined effects of the scaffold's physical structure and its contained cytokines. The generated hyaline cartilage maintains homeostasis over time, reducing the risk of fibrocartilage formation. This strategy addresses a key limitation of microfracture surgery, where regenerated cartilage is often fibrocartilage, offering a promising new approach for cartilage repair.

Fabrication of 3-Dimensional-Printed Bilayered Scaffold Carboxymethyl Chitosan/Oxidized Xanthan Gum, Biphasic Calcium Phosphate for Osteochondral Regeneration

Cartilage tissue regeneration remains challenging due to the tissue's poor self-healing capacity, attributed to its hypocellular and avascular nature, which limits nutrient delivery to the defect site and complicates healing. Traditional methods often utilize the subchondral tissue layer to improve nutrient exchange through its vascular network, although these approaches have limitations. To address these issues, 3-dimensional (3D) printing has been employed to create the bilayered scaffold that mimics the complex structure of osteochondral tissue. In this study, the N,O-carboxymethyl chitosan (NOCC) and oxidized xanthan gum (OXG) hydrogel was fabricated for the cartilage layer due to its similarity to the native cartilage structure, while the biphasic calcium phosphate (BCP) incorporation enhanced the osteoconductivity to promote new bone growth for osteochondral tissue regeneration. Various characterization tests, including compression strength, scanning electron microscopy analysis, and biological properties, were conducted to evaluate and balanced to achieve the highest regenerative capacity for implantation. No cytotoxicity was caused, while the in vitro testing highlighted that the addition of BCP considerably supported cellular behavior on the scaffold and improved the regeneration rate. With 60% BCP content, the 3D scaffold demonstrated a high osteochondral tissue regeneration rate, as evidenced by visual inspection, x-ray imaging, and histological analysis, outperforming other experimental models.

3D bio-printed proteinaceous bioactive scaffold loaded with dual growth factor enhanced chondrogenesis and in situ cartilage regeneration

Articular cartilage has a limited self-healing capacity, leading to joint degeneration and osteoarthritis over time. Therefore, bioactive scaffolds are gaining attention as a promising approach to regenerating and repairing damaged articular cartilage through tissue engineering. In this study, we reported on a novel 3D bio-printed proteinaceous bioactive scaffolds combined with natural porcine cancellous bone dECM, tempo-oxidized cellulose nanofiber (TOCN), and alginate carriers for TGF-β1, FGF-18, and ADSCs to repair cartilage defects. The characterization results demonstrate that the 3D scaffolds are physically stable and facilitate a controlled dual release of TGF-β1 and FGF-18. Moreover, the key biological proteins within the bioactive scaffold actively interact with the biological systems to create a favorable microenvironment for cartilage regeneration. Importantly, the in vitro, in vivo, and in silico simulation showed that the scaffolds promote stem cell recruitment, migration, proliferation, and ECM deposition, and synergistic effects of TGF-β1/FGF-18 with the bioactive scaffolds significantly regulate stem cell chondrogenesis by activating the PI3K/AKT and TGFβ1/Smad4 signaling pathways. After implantation, the proteinaceous bioactive scaffold led to the regeneration of mechanically robust, full-thickness cartilage tissue that closely resembles native cartilage. Thus, these findings may provide a promising approach for regulating stem cell chondrogenesis and treating in situ cartilage regeneration.

MRI monitoring of USPIO-labeled BMSCs combined with alginate scaffold for cartilage defect repair

Objective

This study aimed to evaluate the effectiveness of bone marrow mesenchymal stem cells (BMSCs) combined with sodium alginate scaffolds in repairing knee cartilage defects in New Zealand rabbits. Additionally, it assessed the potential of functional magnetic resonance imaging (fMRI) for non-invasive monitoring of the dynamic repair process.

Methods

Rabbits were randomly divided into four groups: Group A (control), Group B (sodium alginate scaffold), Group C (BMSCs-sodium alginate scaffold), and Group D (USPIO-labeled BMSCs-sodium alginate scaffold). A cartilage defect model was created, and the respective materials were implanted into the defect regions. T2 mapping MRI was performed at weeks 1, 2, and 4 post-surgery to evaluate the repair process, followed by histological analysis to confirm the outcomes.

Results

BMSCs significantly promoted cartilage defect repair and accelerated the degradation of sodium alginate scaffolds. Macroscopic and histological evaluations revealed repair tissue formation in Groups C and D by week 1, with most defect regions filled with new cartilage by week 4. T2 mapping analysis showed a gradual decline in T2 values in Group B, a more pronounced decrease in Group C, and consistently lower T2 values in Group D compared to Group C, with a slow upward trend over time.

Conclusion

This study demonstrated that BMSCs exhibit significant regenerative potential for cartilage defect repair. USPIO labeling enables non-invasive, dynamic monitoring of the repair process without adverse effects on cell viability or differentiation. These findings provide experimental evidence supporting the application of BMSCs combined with magnetic labeling technology in cartilage regeneration.

CircTBCK protects against osteoarthritis by regulating extracellular matrix and autophagy

Osteoarthritis (OA) is a widespread chronic bone and joint disease for which there is currently no effective preventive or therapeutic treatment. Accumulating evidence indicates that circular RNAs (circRNAs), a class of noncoding RNAs, play critical roles in OA. Therefore, in this study, we aimed to reveal an unexplored circTBCK and elucidate its mechanism of action in the pathological process of OA. The different expression of circTBCK was obtained both in vitro and in vivo. In the in vivo model, mice were induced via destabilization of the medial meniscus (DMM) surgery, while in vitro model, mouse cells like primary chondrocytes of newborn mice and ATDC5 cell line were treated with IL-1β treatment (10 ng/mL for 24 h). The level of circTBCK was examined by quantitative real-time polymerase chain reaction (qRT-PCR). After circTBCK was overexpressed or knocked down, IL-1β treatment was performed, and then, chondrocyte viability was detected via a Cell Counting Kit-8 (CCK-8) assay at 0, 24, 48, or 72 h. To assess type II collagen (Collagen II) expression, immunofluorescence (IF) analysis was used. The levels of mRNAs and proteins related to proliferation, the extracellular matrix (ECM) and autophagy were determined by qRT-PCR and Western blotting. Compared with OA treatment, primary chondrocytes with treatment of both circTBCK overexpression and IL-1βincreased the expression of anabolic factors-Collagen II and SRY-box transcription factor 9 (SOX9), proliferation-related molecules-Ki-67 and proliferating cell nuclear antigen (PCNA), and autophagy-related molecules-Microtubule-associated protein 1 light chain 3 (LC3), B-cell lymphoma 1 (Bcl1), and autophagy-related 5 (Atg5) and decreased Sequestosome 1 (SQSTM1 or P62). In contrast, knockdown of circTBCK aggravated the chondrocyte degeneration induced by IL-1β. Overall, our findings suggest that circTBCK, an unexplored circRNA, could regulate autophagy, proliferation, and the extracellular matrix (ECM) to mitigate the development of OA, suggesting a possible target for OA prevention and therapy.

Mucin-Based Dual Cross-Linkable IPN Hydrogel Bioink for 3D Bioprinting and Cartilage Tissue Engineering

The cartilage possesses limited regenerative capacity, necessitating advanced approaches for its repair. This study introduces a bioink designed for cartilage tissue engineering (TE) by incorporating ionically cross-linkable alginate into the photo-cross-linkable MuMA bioink, resulting in a double cross-linked interpenetrating network (IPN) hydrogel. Additionally, hyaluronic acid (HA), a natural component of cartilage and synovial fluid, was added to enhance the scaffold's properties. HA has been demonstrated to improve cartilage lubrication, regulate inflammation, promote cell proliferation, and support extracellular matrix (ECM) deposition and regeneration, making it valuable for cartilage TE. Comprehensive experiments were conducted to assess morphology, swelling, degradation, mechanical and rheological properties, printability, and biocompatibility. Results indicated that the double cross-linked scaffolds comprising MuMA, alginate, and HA exhibited compressive moduli comparable to native cartilage, unlike single cross-linked variants. The double cross-linking also influenced degradation, water uptake, and porosity, contributing to the scaffold durability and stability for chondrocyte support. Biocompatibility tests with C28/I2 cells demonstrated the cell-supportive and chondrogenic potential of the bioink. This study establishes mucin as a versatile material for specialized cartilage tissue engineering applications.

Inconsistencies in clinically significant outcome metrics for knee cartilage repair: a systematic review

To systematically review the variability of reporting of clinically significant outcomes (CSOs) including minimal clinically important difference (MCID), substantial clinical benefit (SCB) and patient acceptable symptom state (PASS), and threshold calculation methods following surgical treatments for cartilage defects of the knee. A systematic review was performed using the 2020 Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. A literature search was performed on August 12th, 2024, using the PubMed, Embase, and Scopus online databases for human clinical studies with publication dates ranging from 2010 to 2024 reporting on MCID, SCB, or PASS following surgical treatments for cartilage defects of the knee. Study demographics, patient-reported outcome measures (PROMs), CSO thresholds, and methods of CSO calculation were collected. A total of 19 studies (n = 3659 patients) with an average follow-up of 36.5 months were included. A total of 14 (93.3%) studies reported MCID, six (31.8%) studies reported SCB, and five (26.3%) studies reported PASS. Of the included studies, 16 (80%) referenced another study for calculating their CSO whereas three (20%) studies calculated their own CSO. A total of 16 different PROMs were reported among the included studies. Eight studies utilized the anchor-based method for CSO calculation, ten studies used both the anchor and the distribution-based methods for calculation, while only one study used the distribution-based method alone. There is considerable variation in the reporting and calculation methods of MCID, SCB, and PASS for different PROMs following surgical treatments for cartilage defects of the knee.Level of Evidence: IV, Systematic Review of Level I-IV studies.

Skatole Alleviates Osteoarthritis by Reprogramming Macrophage Polarization and Protecting Chondrocytes

Osteoarthritis (OA) is the most prevalent joint disease, yet effective disease-modifying OA drugs (DMOADs) remain elusive. Targeting macrophage polarization has emerged as a promising avenue for OA treatment. This study identified skatole through high-throughput screening as an efficient modulator of macrophage polarization. In vivo experiments demonstrated that skatole administration markedly reduced synovitis and cartilage damage in both destabilization of medial meniscus (DMM)-induced OA mice and monosodium iodoacetate (MIA)-induced OA rats. Mechanistically, skatole activated signal transducer and activator of transcription 6 (Stat6) signaling, promoting M2 macrophage polarization, while inhibiting nuclear factor-κB (NFκB) and mitogen-activated protein kinase (MAPK) signaling pathways to suppress M1 polarization. RNA-sequencing analysis, targeted metabolomics, and mitochondrial stress tests further revealed that skatole treatment shifted macrophages toward oxidative phosphorylation for energy production. Additionally, it up-regulated genes associated with glutathione metabolism and reactive oxygen species (ROS) pathways, reducing intracellular ROS production. The CUT&Tag assay results indicated that the downstream transcription factor p65 of NFκB can directly bind to gene loci related to inflammation, oxidative phosphorylation, and glutathione metabolism, thereby modulating gene expression. This regulatory process is inhibited by skatole. At the chondrocyte level, conditional medium from skatole-treated M1 macrophages balanced anabolism and catabolism in mouse chondrocytes and inhibited apoptosis. In IL1β-treated chondrocytes, skatole suppressed inflammation and catabolism without affecting apoptosis or anabolism. Overall, skatole maintains immune microenvironment homeostasis by modulating macrophage polarization in joints and preserves cartilage function by balancing chondrocyte anabolism and catabolism, effectively alleviating OA. These findings suggest skatole's potential as a DMOAD.

Impact of eggshell membrane on metabolism and cell adhesion in oxidatively stressed canine chondrocytes

Eggshell membrane (ESM) is a rich source of bioactive compounds, including proteins, peptides, and antioxidants, contributing to its potential therapeutic benefits. These natural antioxidants might help neutralize reactive oxygen species (ROS) and modulate inflammatory responses, which are often linked with chondrocyte damage in osteoarthritis. In this study, we investigated the functional effects of ESM proteins on H2O2-induced oxidative stress in a neonatal canine chondrocytes. The isolated neonatal chondrocytes demonstrated a high proliferation rate and increased glycosaminoglycan (GAG) production during cultivation. In addition, the expression of key cartilage markers, including collagen types II and IX, and aggrecan, confirmed the retention of the chondrocyte phenotype. Under in vitro conditions, post-treatment with ESM improved chondrocyte viability, indicating that ESM may have a reparative role in mitigating oxidative damage. This significant therapeutic potential was validated through XTT assays, which measured cell metabolic activity at 24 h, and Real-time Cell Analysis (RTCA), providing continuous monitoring over 98 h. In contrast, the preventive effects of ESM against stress were observed exclusively in the XTT analysis. By investigating these aspects, we provide insight into the potential of ESM proteins to protect chondrocytes from oxidative damage, particularly in cartilage repair and joint health. This study is one of the first to create a vital platform based on canine neonatal chondrocytes for monitoring dietary supplements designed to prevent or repair dog cartilage damage. Thus, the study offers a valuable contribution to understanding how ESM bioactive compounds can be used therapeutically, bridging the gap between in vitro findings and practical applications in veterinary medicine.

Therapeutic role of aripiprazole in cartilage defects explored through a drug repurposing approach

Articular cartilage has a limited regenerative capacity, resulting in poor spontaneous healing of damaged tissue. Despite various scientific efforts to enhance cartilage repair, no single method has yielded satisfactory results. With rising drug development costs, drug repositioning has emerged as a viable alternative. This study aimed to identify a drug capable of improving cartilage defects by analyzing chondrogenesis-related microarray data from the Gene Expression Omnibus (GEO) public database. We utilized datasets GSE69110, GSE107649, GSE111822, and GSE116173 to identify genes associated with cartilage differentiation, employing StringTie for differential gene expression analysis and extracting drug data from the Drug-Gene Interaction database. Additionally, we aimed to verify the cartilage regeneration potential of the identified drug through experiments using cellular and animal models. We evaluated the effects of aripiprazole on adipose-derived mesenchymal stem cells (ADMSCs) and chondrocytes using qRT-PCR and a 3D pellet culture system. In vivo, we assessed cartilage restoration by combining aripiprazole with a scaffold and implanting it into artificially induced cartilage defects in Sprague-Dawley rats. Subsequent mRNA sequencing provided insights into the mechanistic pathways involved. Our results showed that aripiprazole significantly increased mRNA expression of COL2A1 and SOX9, markers of chondrogenesis, and promoted chondrogenic condensation in vitro. Furthermore, aripiprazole effectively enhanced cartilage regeneration in the rat model. KEGG pathway and Gene Ontology Biological Processes (GOBP) analyses of the mRNA sequencing data revealed that aripiprazole upregulated genes related to ribosomes and cytoplasmic translation, thereby facilitating chondrogenesis. In conclusion, our findings suggest that aripiprazole is a promising candidate for improving damaged cartilage, offering a novel approach to cartilage regeneration.

Hybrid Nanoparticle Engineered with Transforming Growth Factor -β1-Overexpressed Extracellular Vesicle and Cartilage-Targeted Anti-Inflammatory Liposome for Osteoarthritis

Extracellular vesicles (EVs) possess the characteristics of their parent cells, based on which various studies have actively investigated treatments for diseases using mesenchymal stem cell-derived EVs due to their regenerative activity. Furthermore, in recent years, there have been significant efforts to engineer EVs to improve their native activities and integrate additional functions. Although both endogenous and exogenous methods are used for engineering EVs, endogenous methods may pose the problem of administering substances to cells undergoing metabolic changes, which can cause potential side effects. In addition, exogenous methods may have the limitation of losing beneficial factors inside EVs due to membrane disruption during engineering processes. Surface modification of EVs may also impair efficiency due to the presence of proteins on the EV surface. Therefore, in this study, a stable and efficient engineering method was achieved through the ethanol-mediated hybridization of EVs and functionalized lipid nanoparticles (LNPs) with a fusogenic lipid component. During hybridization, the internal bioactive factors and targeting moiety were maintained to possess the characteristics of both LNPs and EVs. The Ab-Hybrid, which was successfully synthesized through hybridization with nicotinamide-encapsulated and Col2A1 antibody-modified liposome and Transforming growth factor-β1 (TGF-β1)-overexpressed EVs, was administered to osteoarthritis (OA)-induced rats undergoing the destabilization of the medial meniscus surgery. Ultimately, the Ab-Hybrid demonstrated excellent chondroprotective and anti-inflammatory effects with targeting and long-lasting properties in OA lesions. We anticipate that this approach for manufacturing hybrid particles will serve as a valuable EV engineering method and a versatile platform technology applicable to various diseases.

Engineering gene-activated bioprinted scaffolds for enhancing articular cartilage repair

Untreated articular cartilage injuries often result in severe chronic pain and dyskinesia. Current repair strategies have limitations in effectively promoting articular cartilage repair, underscoring the need for innovative therapeutic approaches. A gene-activated matrix (GAM) is a promising and comprehensive therapeutic strategy that integrates tissue-engineered scaffold-guided gene therapy to promote long-term articular cartilage repair by enhancing gene retention, reducing gene loss, and regulating gene release. However, for effective articular cartilage repair, the GAM scaffold must mimic the complex gradient structure of natural articular cartilage. Three-dimensional (3D) bioprinting technology has emerged as a compelling solution, offering the ability to precisely create complex microstructures that mimic the natural articular cartilage. In this review, we summarize the recent research progress on GAM and 3D bioprinted scaffolds in articular cartilage tissue engineering (CTE), while also exploring future challenges and development directions. This review aims to provide new ideas and concepts for the development of gene-activated bioprinted scaffolds with specific properties tailored to meet the stringent requirements of articular cartilage repair.

3D-printed constructs deliver bioactive cargos to expedite cartilage regeneration

Cartilage is solid connective tissue that recovers slowly from injury, and pain and dysfunction from cartilage damage affect many people. The treatment of cartilage injury is clinically challenging and there is no optimal solution, which is a hot research topic at present. With the rapid development of 3D printing technology in recent years, 3D bioprinting can better mimic the complex microstructure of cartilage tissue and thus enabling the anatomy and functional regeneration of damaged cartilage. This article reviews the methods of 3D printing used to mimic cartilage structures, the selection of cells and biological factors, and the development of bioinks and advances in scaffold structures, with an emphasis on how 3D printing structure provides bioactive cargos in each stage to enhance the effect. Finally, clinical applications and future development of simulated cartilage printing are introduced, which are expected to provide new insights into this field and guide other researchers who are engaged in cartilage repair.

Hydrogel-Enhanced Autologous Chondrocyte Implantation for Cartilage Regeneration-An Update on Preclinical Studies

Autologous chondrocyte implantation (ACI) and matrix-induced ACI (MACI) have demonstrated improved clinical outcomes and reduced revision rates for treating osteochondral and chondral defects. However, their ability to achieve lasting, fully functional repair remains limited. To overcome these challenges, scaffold-enhanced ACI, particularly utilizing hydrogel-based biomaterials, has emerged as an innovative strategy. These biomaterials are intended to mimic the biological composition, structural organization, and biomechanical properties of native articular cartilage. This review aims to provide comprehensive and up-to-date information on advancements in hydrogel-enhanced ACI from the past decade. We begin with a brief introduction to cartilage biology, mechanisms of cartilage injury, and the evolution of surgical techniques, particularly looking at ACI. Subsequently, we review the diversity of hydrogel scaffolds currently undergoing development and evaluation in preclinical studies for articular cartilage regeneration, emphasizing chondrocyte-laden hydrogels applicable to ACI. Finally, we address the key challenges impeding effective clinical translation, with particular attention to issues surrounding fixation and integration, aiming to inform and guide the future progression of tissue engineering strategies.

Therapeutic potential of resveratrol and autologous chondrocytes in male rat knee joint cartilage repair

Osteochondral defects (OCDs) in synovial joints are caused by trauma or inflammatory joint diseases, with no definitive treatment available. This study examined the effects of resveratrol and chondrocyte injections in a rat model of OCD. Twenty-four male Sprague-Dawley rats were divided into four groups: a control group, a resveratrol-only group (10 mg/kg), a chondrocyte-only group (1 × 105 cells), and a combined treatment group that received both treatments. After two months, the rats were euthanized, and their knee joints were analysed histologically and immunohistochemically. The results showed that the combined resveratrol and chondrocyte treatment significantly reduced fibrous tissue, increased cartilage tissue volume, improved cellular distribution, and enhanced the regularity of the articular surface. Collagen types I and II and proteoglycan levels were also elevated. These findings suggest that the combination of resveratrol and chondrocytes has a synergistic effect, promoting effective OCD repair in this rat model, offering potential for future therapeutic approaches.

In Vitro Investigation of 3D Printed Hydrogel Scaffolds with Electrospun Tidemark Component for Modeling Osteochondral Interface

Osteochondral (OC) tissue plays a crucial role due to its ability to connect bone and cartilage tissues. To address the complexity of structure and functionality at the bone-cartilage interface, relevant to the presence of the tidemark as a critical element at the bone-cartilage boundary, we fabricated graded scaffolds through sequential 3D printing. The scaffold's bottom layer was based on a gelatin/oxidized alginate mixture enriched with hydroxyapatite (HAp) to create a rougher surface and larger pores to promote osteogenesis. In contrast, the upper layer was engineered to have smaller pores and aimed to promote cartilage tissue formation and mimic the physical properties of the cartilage. An electrospun ε-polycaprolactone (PCL) membrane with micrometer-range pores was incorporated between the layers to replicate the function of tidemark-a barrier to prevent vascularization of cartilage from subchondral bone tissue. In vitro cell studies confirmed the viability of the cells on the layers of the scaffolds and the ability of PCL mesh to prevent cellular migration. The fabricated scaffolds were thoroughly characterized, and their mechanical properties were compared to native OC tissue, demonstrating suitability for OC tissue engineering and graft modeling. The distance of gradient of mineral concentration was found to be 151 µm for grafts and the native OC interface.

A novel mesenchymal stem cell-targeting dual-miRNA delivery system based on aptamer-functionalized tetrahedral framework nucleic acids: Application to endogenous regeneration of articular cartilage

Articular cartilage injury (ACI) remains one of the key challenges in regenerative medicine, as current treatment strategies do not result in ideal regeneration of hyaline-like cartilage. Enhancing endogenous repair via microRNAs (miRNAs) shows promise as a regenerative therapy. miRNA-140 and miRNA-455 are two key and promising candidates for regulating the chondrogenic differentiation of mesenchymal stem cells (MSCs). In this study, we innovatively synthesized a multifunctional tetrahedral framework in which a nucleic acid (tFNA)-based targeting miRNA codelivery system, named A-T-M, was used. With tFNAs as vehicles, miR-140 and miR-455 were connected to and modified on tFNAs, while Apt19S (a DNA aptamer targeting MSCs) was directly integrated into the nanocomplex. The relevant results showed that A-T-M efficiently delivered miR-140 and miR-455 into MSCs and subsequently regulated MSC chondrogenic differentiation through corresponding mechanisms. Interestingly, a synergistic effect between miR-140 and miR-455 was revealed. Furthermore, A-T-M successfully enhanced the endogenous repair capacity of articular cartilage in vivo and effectively inhibited hypertrophic chondrocyte formation. A-T-M provides a new perspective and strategy for the regeneration of articular cartilage, showing strong clinical application value in the future treatment of ACI.

Harnessing Peptide-Based Hydrogels for Enhanced Cartilage Tissue Engineering

Cartilage tissue engineering remains a formidable challenge due to its complex, avascular structure and limited regenerative capacity. Traditional approaches, such as microfracture, autografts, and stem cell delivery, often fail to restore functional tissue adequately. Recently, there has been a surge in the exploration of new materials that mimic the extracellular microenvironment necessary to guide tissue regeneration. This review investigates the potential of peptide-based hydrogels as an innovative solution for cartilage regeneration. These hydrogels, formed via supramolecular self-assembly, exhibit excellent properties, including biocompatibility, ECM mimicry, and controlled biodegradation, making them highly suitable for cartilage tissue engineering. This review explains the structure of cartilage and the principles of supramolecular and peptide hydrogels. It also delves into their specific properties relevant to cartilage regeneration. Additionally, this review presents recent examples and a comparative analysis of various peptide-based hydrogels used for cartilage regeneration. The review also addresses the translational challenges of these materials, highlighting regulatory hurdles and the complexities of clinical application. This comprehensive investigation provides valuable insights for biomedical researchers, tissue engineers, and clinical professionals aiming to enhance cartilage repair methodologies.

Enhancing Cartilage Repair: Surgical Approaches, Orthobiologics, and the Promise of Exosomes

Treating cartilage damage is challenging as its ability for self-regeneration is limited. Left untreated, it can progress to osteoarthritis (OA), a joint disorder characterized by the deterioration of articular cartilage and other joint tissues. Surgical options, such as microfracture and cell/tissue transplantation, have shown promise as techniques to harness the body's endogenous regenerative capabilities to promote cartilage repair. Nonetheless, these techniques have been scrutinized due to reported inconsistencies in long-term outcomes and the tendency for the defects to regenerate as fibrocartilage instead of the smooth hyaline cartilage native to joint surfaces. Orthobiologics are medical therapies that utilize biologically derived substances to augment musculoskeletal healing. These treatments are rising in popularity because of their potential to enhance surgical standards of care. More recent developments in orthobiologics have focused on the role of exosomes in articular cartilage repair. Exosomes are nano-sized extracellular vesicles containing cargo such as proteins, lipids, and nucleic acids, and are known to facilitate intercellular communication, though their regenerative potential still needs to be fully understood. This review aims to demonstrate the advancements in cartilage regeneration, highlight surgical and biological treatment options, and discuss the recent strides in understanding the precise mechanisms of action involved.

Collagen-based hydrogels induce stem cell chondrogenesis and hyaline cartilage regeneration: an in vivo study

Injectable, self-crosslinking collagen-based hydrogels are beneficial for chondrocytes to secrete matrix, positioning them as promising candidates for cartilage tissue engineering. However, previous studies lacked insight into the ability of cell-free collagen-based hydrogels to regenerate hyaline cartilage defect. Therefore, this study aimed to evaluate the potential of collagen-based hydrogels (Col and ColHA) to induce chondrogenic differentiation of stem cells and in situ hyaline cartilage regeneration. Both Col and ColHA hydrogels self-crosslinked in situ and exhibited similar physical properties. In vitro experiments showed they supported the survival, adhesion, spreading, and proliferation of bone marrow stem cells (BMSCs). Moreover, both hydrogels induced ectopic differentiation of BMSCs into chondrocytes when implanted subcutaneously into the back of nude mice. ColHA hydrogel notably enhanced type II collagen secretion. The results of repairing cartilage defects in situ revealed both hydrogels facilitated hyaline cartilage regeneration and maintained cartilage phenotype without exogenous BMSCs. Hydrogels encapsulating BMSCs expedited cartilage repair, and ColHA/BMSC constructs showed better mechanical properties, suggesting their potential for cartilage repair applications. This study implies that collagen-based hydrogels are good candidates for hyaline cartilage regeneration.

Sustained Release of Hydrogen and Magnesium Ions Mediated by a Foamed Gelatin-Methacryloyl Hydrogel for the Repair of Bone Defects in Diabetes

Diabetic bone defects, exacerbated by hyperglycemia-induced inflammation and oxidative stress, present significant therapeutic challenges. This study introduces a novel injectable scaffold, MgH2@PLGA/F-GM, consisting of foamed gelatin-methacryloyl (GelMA) and magnesium hydride (MgH2) microspheres encapsulated in poly(lactic-co-glycolic acid) (PLGA). This scaffold is uniquely suited for diabetic bone defects, conforming to complex shapes and fostering an environment conducive to tissue regeneration. As it degrades, Mg(OH)2 is released and dissolved by PLGA's acidic byproducts, releasing therapeutic Mg2+ ions. These ions are instrumental in macrophage phenotype modulation, inflammation reduction, and angiogenesis promotion, all vital for diabetic bone healing. Additionally, hydrogen (H2) released during degradation mitigates oxidative stress by diminishing reactive oxygen species (ROS). This multifaceted approach not only reduces ROS and inflammation but also enhances M2 macrophage polarization and cell migration, culminating in improved angiogenesis and bone repair. This scaffold presents an innovative strategy for addressing the complexities of diabetic bone defect treatment.

Advanced gene nanocarriers/scaffolds in nonviral-mediated delivery system for tissue regeneration and repair

Tissue regeneration technology has been rapidly developed and widely applied in tissue engineering and repair. Compared with traditional approaches like surgical treatment, the rising gene therapy is able to have a durable effect on tissue regeneration, such as impaired bone regeneration, articular cartilage repair and cancer-resected tissue repair. Gene therapy can also facilitate the production of in situ therapeutic factors, thus minimizing the diffusion or loss of gene complexes and enabling spatiotemporally controlled release of gene products for tissue regeneration. Among different gene delivery vectors and supportive gene-activated matrices, advanced gene/drug nanocarriers attract exceptional attraction due to their tunable physiochemical properties, as well as excellent adaptive performance in gene therapy for tissue regeneration, such as bone, cartilage, blood vessel, nerve and cancer-resected tissue repair. This paper reviews the recent advances on nonviral-mediated gene delivery systems with an emphasis on the important role of advanced nanocarriers in gene therapy and tissue regeneration.

A Systematic Review of Human Amnion Enhanced Cartilage Regeneration in Full-Thickness Cartilage Defects

Cartilage defects present a significant challenge in orthopedic medicine, often leading to pain and functional impairment. To address this, human amnion, a naturally derived biomaterial, has gained attention for its potential in enhancing cartilage regeneration. This systematic review aims to evaluate the efficacy of human amnion in enhancing cartilage regeneration for full-thickness cartilage defects. An electronic search was conducted on MEDLINE-PubMed, Web of Science (WoS), and the Scopus database up to 27 December 2023 from 2007. A total of 401 articles were identified. After removing 125 duplicates and excluding 271 articles based on predetermined criteria, only 5 articles remained eligible for inclusion in this systematic review. All five eligible articles conducted in vivo studies utilizing rabbits as subjects. Furthermore, analysis of the literature reveals an increasing trend in the frequency of utilizing human amnion for the treatment of cartilage defects. Various forms of human amnion were utilized either alone or seeded with cells prior to implantation. Histological assessments and macroscopic observations indicated usage of human amnion improved cartilage repair outcomes. All studies highlighted the positive results despite using different forms of amnion tissues. This systematic review underscores the promising role of human amnion as a viable option for enhancing cartilage regeneration in full-thickness cartilage defects, thus offering valuable insights for future research and clinical applications in orthopedic tissue engineering.

Latest Advances in Chondrocyte-Based Cartilage Repair

Chondrocyte-based cell therapy has been used for more than 30 years and is still considered to be a promising method of cartilage repair despite some limitations. This review introduces the latest developments of four generations of autologous chondrocyte implantation and current autologous chondrocyte products. The regeneration of cartilage from adult chondrocytes is limited by culture-induced dedifferentiation and patient age. Cartibeads is an innovative three-step method to produce high-quality hyaline cartilage microtissues, and it is developed from adult dedifferentiated chondrocytes with a high number of cell passages. In addition, allogeneic chondrocyte therapies using the Quantum hollow-fiber bioreactor and several signaling pathways involved in chondrocyte-based cartilage repair are mentioned, such as WNT signaling, the BMP-2/WISP1 pathway, and the FGF19 pathway.

Pioneering nanomedicine in orthopedic treatment care: a review of current research and practices

A developing use of nanotechnology in medicine involves using nanoparticles to administer drugs, genes, biologicals, or other materials to targeted cell types, such as cancer cells. In healthcare, nanotechnology has brought about revolutionary changes in the treatment of various medical and surgical conditions, including in orthopedic. Its clinical applications in surgery range from developing surgical instruments and suture materials to enhancing imaging techniques, targeted drug delivery, visualization methods, and wound healing procedures. Notably, nanotechnology plays a significant role in preventing, diagnosing, and treating orthopedic disorders, which is crucial for patients' functional rehabilitation. The integration of nanotechnology improves standards of patient care, fuels research endeavors, facilitates clinical trials, and eventually improves the patient's quality of life. Looking ahead, nanotechnology holds promise for achieving sustained success in numerous surgical disciplines, including orthopedic surgery, in the years to come. This review aims to focus on the application of nanotechnology in orthopedic surgery, highlighting the recent development and future perspective to bridge the bridge for clinical translation.

Combinatory Nanovesicle with siRNA-Loaded Extracellular Vesicle and IGF-1 for Osteoarthritis Treatments

Extracellular vesicles (EVs) have been found to have the characteristics of their parent cells. Based on the characteristics of these EVs, various studies on disease treatment using mesenchymal stem cell (MSC)-derived EVs with regenerative activity have been actively conducted. The therapeutic nature of MSC-derived EVs has been shown in several studies, but in recent years, there have been many efforts to functionalize EVs to give them more potent therapeutic effects. Strategies for functionalizing EVs include endogenous and exogenous methods. In this study, human umbilical cord MSC (UCMSC)-derived EVs were selected for optimum OA treatments with expectation via bioinformatics analysis based on antibody array. And we created a novel nanovesicle system called the IGF-si-EV, which has the properties of both cartilage regeneration and long-term retention in the lesion site, attaching positively charged insulin-like growth factor-1 (IGF-1) to the surface of the UCMSC-derived Evs carrying siRNA, which inhibits MMP13. The downregulation of inflammation-related cytokine (MMP13, NF-kB, and IL-6) and the upregulation of cartilage-regeneration-related factors (Col2, Acan) were achieved with IGF-si-EV. Moreover, the ability of IGF-si-EV to remain in the lesion site for a long time has been proven through an ex vivo system. Collectively, the final constructed IGF-si-EV can be proposed as an effective OA treatment through its successful MMP13 inhibition, chondroprotective effect, and cartilage adhesion ability. We also believe that this EV-based nanoparticle-manufacturing technology can be applied as a platform technology for various diseases.

N6-Methyladenosine in Cell-Fate Determination of BMSCs: From Mechanism to Applications

The methylation of adenosine base at the nitrogen-6 position is referred to as "N6-methyladenosine (m6A)" and is one of the most prevalent epigenetic modifications in eukaryotic mRNA and noncoding RNA (ncRNA). Various m6A complex components known as "writers," "erasers," and "readers" are involved in the function of m6A. Numerous studies have demonstrated that m6A plays a crucial role in facilitating communication between different cell types, hence influencing the progression of diverse physiological and pathological phenomena. In recent years, a multitude of functions and molecular pathways linked to m6A have been identified in the osteogenic, adipogenic, and chondrogenic differentiation of bone mesenchymal stem cells (BMSCs). Nevertheless, a comprehensive summary of these findings has yet to be provided. In this review, we primarily examined the m6A alteration of transcripts associated with transcription factors (TFs), as well as other crucial genes and pathways that are involved in the differentiation of BMSCs. Meanwhile, the mutual interactive network between m6A modification, miRNAs, and lncRNAs was intensively elucidated. In the last section, given the beneficial effect of m6A modification in osteogenesis and chondrogenesis of BMSCs, we expounded upon the potential utility of m6A-related therapeutic interventions in the identification and management of human musculoskeletal disorders manifesting bone and cartilage destruction, such as osteoporosis, osteomyelitis, osteoarthritis, and bone defect.

Natural based hydrogels promote chondrogenic differentiation of human mesenchymal stem cells

Background: The cartilage tissue lacks blood vessels, which is composed of chondrocytes and ECM. Due to this vessel-less structure, it is difficult to repair cartilage tissue damages. One of the new methods to repair cartilage damage is to use tissue engineering. In the present study, it was attempted to simulate a three-dimensional environment similar to the natural ECM of cartilage tissue by using hydrogels made of natural materials, including Chitosan and different ratios of Alginate. Material and methods: Chitosan, alginate and Chitosan/Alginate hydrogels were fabricated. Fourier Transform Infrared, XRD, swelling ratio, porosity measurement and degradation tests were applied to scaffolds characterization. After that, human adipose derived-mesenchymal stem cells (hADMSCs) were cultured on the hydrogels and then their viability and chondrogenic differentiation capacity were studied. Safranin O and Alcian blue staining, immunofluorescence staining and real time RT-PCR were used as analytical methods for chondrogenic differentiation potential evaluation of hADMSCs when cultured on the hydrogels. Results: The highest degradation rate was detected in Chitosan/Alginate (1:0.5) group The scaffold biocompatibility results revealed that the viability of the cells cultured on the hydrogels groups was not significantly different with the cells cultured in the control group. Safranin O staining, Alcian blue staining, immunofluorescence staining and real time PCR results revealed that the chondrogenic differentiation potential of the hADMSCs when grown on the Chitosan/Alginate hydrogel (1:0.5) was significantly higher than those cell grown on the other groups. Conclusion: Taken together, these results suggest that Chitosan/Alginate hydrogel (1:0.5) could be a promising candidate for cartilage tissue engineering applications.

Research progress of procyanidins in repairing cartilage injury after anterior cruciate ligament tear

Anterior cruciate ligament (ACL) tear is a common sports-related injury, and cartilage injury always emerges as a serious complication following ACL tear, significantly impacting the physical and psychological well-being of affected individuals. Over the years, efforts have been directed toward finding strategies to repair cartilage injury after ACL tear. In recent times, procyanidins, known for their anti-inflammatory and antioxidant properties, have emerged as potential key players in addressing this concern. This article focuses on summarizing the research progress of procyanidins in repairing cartilage injury after ACL tear. It covers the roles, mechanisms, and clinical significance of procyanidins in repairing cartilage injury following ACL tear and explores the future prospects of procyanidins in this domain. This review provides novel insights and hope for the repair of cartilage injury following ACL tear.

Regulation of Oxygen Tension as a Strategy to Control Chondrocytic Phenotype for Cartilage Tissue Engineering and Regeneration

Cartilage defects and osteoarthritis are health problems which are major burdens on health care systems globally, especially in aging populations. Cartilage is a vulnerable tissue, which generally faces a progressive degenerative process when injured. This makes it the 11th most common cause of global disability. Conservative methods are used to treat the initial phases of the illness, while orthopedic management is the method used for more progressed phases. These include, for instance, arthroscopic shaving, microfracturing and mosaicplasty, and joint replacement as the final treatment. Cell-based implantation methods have also been developed. Despite reports of successful treatments, they often suffer from the non-optimal nature of chondrocyte phenotype in the repair tissue. Thus, improved strategies to control the phenotype of the regenerating cells are needed. Avascular tissue cartilage relies on diffusion for nutrients acquisition and the removal of metabolic waste products. A low oxygen content is also present in cartilage, and the chondrocytes are, in fact, well adapted to it. Therefore, this raises an idea that the regulation of oxygen tension could be a strategy to control the chondrocyte phenotype expression, important in cartilage tissue for regenerative purposes. This narrative review discusses the aspects related to oxygen tension in the metabolism and regulation of articular and growth plate chondrocytes and progenitor cell phenotypes, and the role of some microenvironmental factors as regulators of chondrocytes.

Regulating Chondro-Bone Metabolism for Treatment of Osteoarthritis via High-Permeability Micro/Nano Hydrogel Microspheres

Destruction of cartilage due to the abnormal remodeling of subchondral bone (SB) leads to osteoarthritis (OA), and restoring chondro-bone metabolic homeostasis is the key to the treatment of OA. However, traditional intra-articular injections for the treatment of OA cannot directly break through the cartilage barrier to reach SB. In this study, the hydrothermal method is used to synthesize ultra-small size (≈5 nm) selenium-doped carbon quantum dots (Se-CQDs, SC), which conjugated with triphenylphosphine (TPP) to create TPP-Se-CQDs (SCT). Further, SCT is dynamically complexed with hyaluronic acid modified with aldehyde and methacrylic anhydride (AHAMA) to construct highly permeable micro/nano hydrogel microspheres (SCT@AHAMA) for restoring chondro-bone metabolic homeostasis. In vitro experiments confirmed that the selenium atoms scavenged reactive oxygen species (ROS) from the mitochondria of mononuclear macrophages, inhibited osteoclast differentiation and function, and suppressed early chondrocyte apoptosis to maintain a balance between cartilage matrix synthesis and catabolism. In vivo experiments further demonstrated that the delivery system inhibited osteoclastogenesis and H-vessel invasion, thereby regulating the initiation and process of abnormal bone remodeling and inhibiting cartilage degeneration in SB. In conclusion, the micro/nano hydrogel microspheres based on ultra-small quantum dots facilitate the efficient penetration of articular SB and regulate chondro-bone metabolism for OA treatment.

Exploring the roles of noncoding RNAs in craniofacial abnormalities: A systematic review

Congenital craniofacial abnormalities are congenital anomalies of variable expressivity and severity with a recognizable set of abnormalities, which are derived from five identifiable primordial structures. They can occur unilaterally or bilaterally and include various malformations such as cleft lip with/without palate, craniosynostosis, and craniofacial microsomia. To date, the molecular etiology of craniofacial abnormalities is largely unknown. Noncoding RNAs (ncRNAs), including microRNAs, long ncRNAs, circular RNAs and PIWI-interacting RNAs, function as major regulators of cellular epigenetic hallmarks via regulation of various molecular and cellular processes. Recently, aberrant expression of ncRNAs has been implicated in many diseases, including craniofacial abnormalities. Consequently, this review focuses on the role and mechanism of ncRNAs in regulating craniofacial development in the hope of providing clues to identify potential therapeutic targets.

Regeneration of Mechanically Enhanced Tissue-Engineered Cartilage Based on the Decalcified Bone Matrix Framework

Human decalcified bone matrix (HDBM) is a framework with a porous structure and good biocompatibility. Nevertheless, its oversized pores lead to massive cell loss when seeding chondrocytes directly over it. Gelatin (GT) is a type of protein obtained by partial hydrolysis of collagen. The GT scaffold can be prepared from the GT solution through freeze-drying. More importantly, the pore size of the GT scaffold can be controlled by optimizing the concentration of the GT solution. Similarly, when different concentrations of gelatin are combined with HDBM and then freeze-dried, the pore size of the HDBM can be modified to different degrees. In this study, the HDBM framework was modified with 0.3, 0.6, and 0.9%GT, resulting in an improved pore size and adhesion rate. Results showed that the HDBM framework with 0.6%GT (HDBM-0.6%GT) had an average pore size of 200 μm, which was more suitable for chondrocyte seeding. Additionally, our study validated that porcine decalcified bone matrix (PDBM) had a proper pore structure. Chondrocytes were in vitro seeded on the three frameworks for 4 weeks and then implanted in nude mice and autologous goats, respectively. The in vivo cartilage regeneration results showed that HDBM-0.6%GT and PDBM frameworks compensated for the oversized pores of the HDBM framework. Moreover, they showed successfully regenerated more mature cartilage tissue with a certain shape in animals.

The Dual-Responsive Interaction of Particulated Hyaline Cartilage and Plasma Rich in Growth Factors (PRGF) in the Repair of Cartilage Defects: An In Vitro Study

The treatment of chondral and osteochondral defects is challenging. These types of lesions are painful and progress to osteoarthritis over time. Tissue engineering offers tools to address this unmet medical need. The use of an autologous cartilage construct consisting of hyaline cartilage chips embedded in plasma rich in growth factors (PRGF) has been proposed as a therapeutic alternative. The purpose of this study was to dig into the potential mechanisms behind the in vitro remodelling process that might explain the clinical success of this technique and facilitate its optimisation. Chondrocyte viability and cellular behaviour over eight weeks of in vitro culture, type II collagen synthesis, the dual delivery of growth factors by hyaline cartilage and PRGF matrix, and the ultrastructure of the construct and its remodelling were characterised. The main finding of this research is that the cartilage fragments embedded in the three-dimensional PRGF scaffold contain viable chondrocytes that are able to migrate into the fibrin network, proliferate and synthesise extracellular matrix after the second week of in vitro culture. The characterization of this three-dimensional matrix is key to unravelling the molecular kinetics responsible for its efficacy.