Strategies for articular cartilage lesion repair and functional restoration

Control and interplay of scaffold-biomolecule interactions applied to cartilage tissue engineering

Cartilage tissue engineering based on the combination of biomaterials, adult or stem cells and bioactive factors is a challenging approach for regenerative medicine with the aim of achieving the formation of a functional neotissue stable in the long term. Various 3D scaffolds have been developed to mimic the extracellular matrix environment and promote cartilage repair. In addition, bioactive factors have been extensively employed to induce and maintain the cartilage phenotype. However, the spatiotemporal control of bioactive factor release remains critical for maximizing the regenerative potential of multipotent cells, such as mesenchymal stromal cells (MSCs), and achieving efficient chondrogenesis and sustained tissue homeostasis, which are essential for the repair of hyaline cartilage. Despite advances, the effective delivery of bioactive factors is limited by challenges such as insufficient retention at the site of injury and the loss of therapeutic efficacy due to uncontrolled drug release. These limitations have prompted research on biomolecule-scaffold interactions to develop advanced delivery systems that provide sustained release and controlled bioavailability of biological factors, thereby improving therapeutic outcomes. This review focuses specifically on biomaterials (natural, hybrid and synthetic) and biomolecules (molecules, proteins, nucleic acids) of interest for cartilage engineering. Herein, we review in detail the approaches developed to maintain the biomolecules in scaffolds and control their release, based on their chemical nature and structure, through steric, non-covalent and/or covalent interactions, with a view to their application in cartilage repair.

An injectable active hydrogel based on BMSC-derived extracellular matrix for cartilage regeneration enhancement

Articular cartilage injury impairs joint function and necessitates orthopedic intervention to restore the structure and function of the cartilage. Extracellular matrix (ECM) scaffolds derived from bone marrow mesenchymal stem cells (BMSCs) can effectively promote cell adhesion, proliferation, and chondrogenesis. However, pre-shaped ECM scaffolds have limited applicability due to their poor fit with the irregular surface of most articular cartilage defects. In this study, we fabricated an injectable active ECM hydrogel from autologous BMSCs-derived ECM by freeze-drying, liquid nitrogen milling, and enzymatic digestion. Moreover, our in vitro and in vivo results demonstrated that the prepared hydrogel enhanced chondrocyte adhesion and proliferation, chondrogenesis, cartilage regeneration, and integration with host tissue, respectively. These findings indicate that active ECM components can provide trophic support for cell proliferation and differentiation, restoring the structure and function of damaged cartilage.

Advancements in tissue engineering for articular cartilage regeneration

Articular cartilage injury is a prevalent clinical condition resulting from trauma, tumors, infection, osteoarthritis, and other factors. The intrinsic lack of blood vessels, nerves, and lymphatic vessels within cartilage tissue severely limits its self-regenerative capacity after injury. Current treatment options, such as conservative drug therapy and joint replacement, have inherent limitations. Achieving perfect regeneration and repair of articular cartilage remains an ongoing challenge in the field of regenerative medicine. Tissue engineering has emerged as a key focus in articular cartilage injury research, aiming to utilize cultured and expanded tissue cells combined with suitable scaffold materials to create viable, functional tissues. This review article encompasses the latest advancements in seed cells, scaffolds, and cytokines. Additionally, the role of stimulatory factors including cytokines and growth factors, genetic engineering techniques, biophysical stimulation, and bioreactor systems, as well as the role of scaffolding materials including natural scaffolds, synthetic scaffolds, and nanostructured scaffolds in the regeneration of cartilage tissues are discussed. Finally, we also outline the signaling pathways involved in cartilage regeneration. Our review provides valuable insights for scholars to address the complex problem of cartilage regeneration and repair.

Articular cartilage repair biomaterials: strategies and applications

Articular cartilage injury is a frequent worldwide disease, while effective treatment is urgently needed. Due to lack of blood vessels and nerves, the ability of cartilage to self-repair is limited. Despite the availability of various clinical treatments, unfavorable prognoses and complications remain prevalent. However, the advent of tissue engineering and regenerative medicine has generated considerable interests in using biomaterials for articular cartilage repair. Nevertheless, there remains a notable scarcity of comprehensive reviews that provide an in-depth exploration of the various strategies and applications. Herein, we present an overview of the primary biomaterials and bioactive substances from the tissue engineering perspective to repair articular cartilage. The strategies include regeneration, substitution, and immunization. We comprehensively delineate the influence of mechanically supportive scaffolds on cellular behavior, shedding light on emerging scaffold technologies, including stimuli-responsive smart scaffolds, 3D-printed scaffolds, and cartilage bionic scaffolds. Biologically active substances, including bioactive factors, stem cells, extracellular vesicles (EVs), and cartilage organoids, are elucidated for their roles in regulating the activity of chondrocytes. Furthermore, the composite bioactive scaffolds produced industrially to put into clinical use, are also explicitly presented. This review offers innovative solutions for treating articular cartilage ailments and emphasizes the potential of biomaterials for articular cartilage repair in clinical translation.

Decellularized allogeneic cartilage paste with human costal cartilage and crosslinked hyaluronic acid-carboxymethyl cellulose carrier augments microfracture for improved articular cartilage repair

Articular cartilage lacks natural healing abilities and necessitates surgical treatments for injuries. While microfracture (MF) is a primary surgical approach, it often results in the formation of unstable fibrocartilage. Delivering hyaline cartilage directly to defects poses challenges due to the limited availability of autologous cartilage and difficulties associated with allogeneic cartilage delivery. We developed a decellularized allogeneic cartilage paste (DACP) using human costal cartilage mixed with a crosslinked hyaluronic acid (HA)-carboxymethyl cellulose (CMC) carrier. The decellularized allogeneic cartilage preserved the extracellular matrix and the nanostructure of native hyaline cartilage. The crosslinked HA-CMC carrier provided shape retention and moldability. In vitro studies confirmed that DACP did not cause cytotoxicity and promoted migration, proliferation, and chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells. After 6 months of implantation in rabbit knee osteochondral defects, DACP combined with MF outperformed MF alone, demonstrating improved gait performance, defect filling, morphology, extracellular matrix deposition, and biomechanical properties similar to native cartilage. Thus, DACP offers a safe and effective method for articular cartilage repair, representing a promising augmentation to MF. STATEMENT OF SIGNIFICANCE: Directly delivering hyaline cartilage to repair articular cartilage defects is an ideal treatment. However, current allogeneic cartilage products face delivery challenges. In this study, we developed a decellularized allogeneic cartilage paste (DACP) by mixing human costal cartilage with crosslinked hyaluronic acid (HA)-carboxymethyl cellulose (CMC). DACP preserves extracellular matrix components and nanostructures similar to native cartilage, with HA-CMC ensuring shape retention and moldability. Our study demonstrates improved cartilage repair by combining DACP with microfracture, compared to microfracture alone, in rabbit knee defects over 6 months. This is the first report showing better articular cartilage repair using decellularized allogeneic cartilage with microfracture, without the need for exogenous cells or bioactive substances.

Impact of local delivery of allogeneic chondrocytes on the biological response and healing of the sternum bones after sternotomy

Median sternotomy is the surgical method of choice for many procedures where one of the main problems is the long post-operative wound healing process leading to sternal dehiscence and the development of infection. This leads to prolonged hospital stay and increased mortality due to post-operative complications. A promising solution seems to be the use of allogeneic chondrocytes for wound treatment, whose properties in the field of cartilage reconstruction are widely used in medicine, mainly in orthopedics. In the present study, we investigated the effect of local delivery of allogeneic chondrocytes on the biological response and healing of the sternum after sternotomy. We optimized the culture conditions for the isolated chondrocytes, which were then applied to the sternal incision wound. Chondrocytes in the culture were assessed on the basis of the presence of chondrocyte-specific genes: Sox9, Aggrecan and Collagen II. In turn, the histopathological and immunohistochemical evaluation was used to assess the safety of implantation. In our work, we demonstrated the possibility of obtaining a viable culture of chondrocytes, which were successfully introduced into the sternal wound after sternotomy. Importantly, implantation of allogeneic chondrocytes showed no significant side effects. The obtained results open new possibilities for research on the use of allogeneic chondrocytes in the process of accelerating wound healing after median sternotomy.

Scaffolds containing GAG-mimetic cellulose sulfate promote TGF-β interaction and MSC Chondrogenesis over native GAGs

Cartilage tissue engineering strategies seek to repair damaged tissue using approaches that include scaffolds containing components of the native extracellular matrix (ECM). Articular cartilage consists of glycosaminoglycans (GAGs) which are known to sequester growth factors. In order to more closely mimic the native ECM, this study evaluated the chondrogenic differentiation of mesenchymal stem cells (MSCs), a promising cell source for cartilage regeneration, on fibrous scaffolds that contained the GAG-mimetic cellulose sulfate. The degree of sulfation was evaluated, examining partially sulfated cellulose (pSC) and fully sulfated cellulose (NaCS). Comparisons were made with scaffolds containing native GAGs (chondroitin sulfate A, chondroitin sulfate C and heparin). Transforming growth factor-beta3 (TGF-β3) sequestration, as measured by rate of association, was higher for sulfated cellulose-containing scaffolds as compared to native GAGs. In addition, TGF-β3 sequestration and retention over time was highest for NaCS-containing scaffolds. Sulfated cellulose-containing scaffolds loaded with TGF-β3 showed enhanced chondrogenesis as indicated by a higher Collagen Type II:I ratio over native GAGs. NaCS-containing scaffolds loaded with TGF-β3 had the highest expression of chondrogenic markers and a reduction of hypertrophic markers in dynamic loading conditions, which more closely mimic in vivo conditions. Studies also demonstrated that TGF-β3 mediated its effect through the Smad2/3 signaling pathway where the specificity of TGF-β receptor (TGF- βRI)-phosphorylated SMAD2/3 was verified with a receptor inhibitor. Therefore, studies demonstrate that scaffolds containing cellulose sulfate enhance TGF-β3-induced MSC chondrogenic differentiation and show promise for promoting cartilage tissue regeneration.

Engineered biomimetic micro/nano-materials for tissue regeneration

The incidence of tissue and organ damage caused by various diseases is increasing worldwide. Tissue engineering is a promising strategy of tackling this problem because of its potential to regenerate or replace damaged tissues and organs. The biochemical and biophysical cues of biomaterials can stimulate and induce biological activities such as cell adhesion, proliferation and differentiation, and ultimately achieve tissue repair and regeneration. Micro/nano materials are a special type of biomaterial that can mimic the microstructure of tissues on a microscopic scale due to its precise construction, further providing scaffolds with specific three-dimensional structures to guide the activities of cells. The study and application of biomimetic micro/nano-materials have greatly promoted the development of tissue engineering. This review aims to provide an overview of the different types of micro/nanomaterials, their preparation methods and their application in tissue regeneration.

Anatomy, molecular structures, and hyaluronic acid - Gelatin injectable hydrogels as a therapeutic alternative for hyaline cartilage recovery: A review

Cartilage damage caused by trauma or osteoarthritis is a common joint disease that can increase the social and economic burden in society. Due to its avascular characteristics, the poor migration ability of chondrocytes, and a low number of progenitor cells, the self-healing ability of cartilage defects has been significantly limited. Hydrogels have been developed into one of the most suitable biomaterials for the regeneration of cartilage because of its characteristics such as high-water absorption, biodegradation, porosity, and biocompatibility similar to natural extracellular matrix. Therefore, the present review article presents a conceptual framework that summarizes the anatomical, molecular structure and biochemical properties of hyaline cartilage located in long bones: articular cartilage and growth plate. Moreover, the importance of preparation and application of hyaluronic acid - gelatin hydrogels for cartilage tissue engineering are included. Hydrogels possess benefits of stimulating the production of Agc1, Col2α1-IIa, and SOX9, molecules important for the synthesis and composition of the extracellular matrix of cartilage. Accordingly, they are believed to be promising biomaterials of therapeutic alternatives to treat cartilage damage.

Computational model of articular cartilage regeneration induced by scaffold implantation in vivo

Computational models allow to explain phenomena that cannot be observed through an animal model, such as the strain and stress states which can highly influence regeneration of the tissue. For this purpose, we have developed a simulation tool to determine the mechanical conditions provided by the polymeric scaffold. The computational model considered the articular cartilage, the subchondral bone, and the scaffold. All materials were modeled as poroelastic, and the cartilage had linear-elastic oriented collagen fibers. This model was able to explain the remodeling process that subchondral bone goes through, and how the scaffold allowed the conditions for cartilage regeneration. These results suggest that the use of scaffolds might lead the cartilaginous tissue growth in vivo by providing a better mechanical environment. Moreover, the developed computational model demonstrated to be useful as a tool prior experimental in vivo studies, by predicting the possible outcome of newly proposed treatments allowing to discard approaches that might not bring good results.

Injectable heat-sensitive nanocomposite hydrogel for regulating gene expression in the treatment of alcohol-induced osteonecrosis of the femoral head

For repairing lesions, it is important to recover physiological and cellular activities. Gene therapy can restore these activities by regulating the expression of genes in lesion cells; however, in chronic diseases, such as alcohol-induced osteonecrosis of the femoral head (ONFH), gene therapy has failed to provide long-term effects. In this study, we developed a heat-sensitive nanocomposite hydrogel system with a secondary nanostructure that can regulate gene expression and achieve long-term gene regulation in lesion cells. This nanocomposite hydrogel exists in a liquid state at 25 °C and is injectable. Once injected into the body, the hydrogel can undergo solidification induced by body heat, thereby gaining the ability to be retained in the body for a prolonged time period. With the gradual degradation of the hydrogel in vivo, the internal secondary nanostructures are continuously released. These nanoparticles carry plasmids and siRNA into lesion stem cells to promote the expression of B-cell lymphoma 2 (inhibiting the apoptosis of stem cells) and inhibit the secretion of peroxisome proliferators-activated receptors γ (PPARγ, inhibiting the adipogenic differentiation of stem cells). Finally, the physiological activity of the stem cells in the ONFH area was restored and ONFH repair was promoted. In vivo experiments demonstrated that this nanocomposite hydrogel can be indwelled for a long time, thereby providing long-term treatment effects. As a result, bone reconstruction occurs in the ONFH area, thus enabling the treatment of alcohol-induced ONFH. Our nanocomposite hydrogel provides a novel treatment option for alcohol-related diseases and may serve as a useful biomaterial for other gene therapy applications.

Progress of Microfluidic Hydrogel-Based Scaffolds and Organ-on-Chips for the Cartilage Tissue Engineering

Cartilage degeneration is among the fundamental reasons behind disability and pain across the globe. Numerous approaches have been employed to treat cartilage diseases. Nevertheless, none have shown acceptable outcomes in the long run. In this regard, the convergence of tissue engineering and microfabrication principles can allow developing more advanced microfluidic technologies, thus offering attractive alternatives to current treatments and traditional constructs used in tissue engineering applications. Herein, the current developments involving microfluidic hydrogel-based scaffolds, promising structures for cartilage regeneration, ranging from hydrogels with microfluidic channels to hydrogels prepared by the microfluidic devices, that enable therapeutic delivery of cells, drugs, and growth factors, as well as cartilage-related organ-on-chips are reviewed. Thereafter, cartilage anatomy and types of damages, and present treatment options are briefly overviewed. Various hydrogels are introduced, and the advantages of microfluidic hydrogel-based scaffolds over traditional hydrogels are thoroughly discussed. Furthermore, available technologies for fabricating microfluidic hydrogel-based scaffolds and microfluidic chips are presented. The preclinical and clinical applications of microfluidic hydrogel-based scaffolds in cartilage regeneration and the development of cartilage-related microfluidic chips over time are further explained. The current developments, recent key challenges, and attractive prospects that should be considered so as to develop microfluidic systems in cartilage repair are highlighted.

Design of short peptides and peptide amphiphiles as collagen mimics and an investigation of their interactions with collagen using molecular dynamics simulations and docking studies

Short peptide sequences and bolaamphiphiles derived from natural proteins are gaining importance due to their ability to form unique nanoscale architectures for a variety of biological applications. In this work, we have designed six short peptides (triplet or monomeric forms) and two peptide bolaamphiphiles that either incorporate the bioactive collagen motif (Gly-X-Y) or sequences where Gly, Pro, or hydroxyproline (Hyp) are replaced by Ala or His. For the bolaamphiphiles, a malate moiety was used as the aliphatic linker for connecting His with Hyp to create collagen mimics. Stability of the assemblies was assessed through molecular dynamics simulations and results indicated that (Pro-Ala-His)₃ and (Ala-His-Hyp)₃ formed the most stable structures, while the amphiphiles and the monomers showed some disintegration over the course of the 200 ns simulation, though most regained structural integrity and formed fibrillar structures, and micelles by the end of the simulation, likely due to the formation of more thermodynamically stable conformations. Multiple replica simulations (REMD) were also conducted where the sequences were simulated at different temperatures. Our results showed excellent convergence in most cases compared to constant temperature molecular dynamics simulation. Furthermore, molecular docking and MD simulations of the sequences bound to collagen triple helix structure revealed that several of the sequences had a high binding affinity and formed stable complexes, particularly (Pro-Ala-His)₃ and (Ala-His-Hyp)₃. Thus, we have designed new hybrid-peptide-based sequences which may be developed for potential applications as biomaterials for tissue engineering or drug delivery.

Current concepts and perspectives for articular cartilage regeneration

Articular cartilage injuries are common in the population. The increment in the elderly people and active life results in an increasing demand for new technologies and good outcomes to satisfy longer and healthier life expectancies. However, because of cartilage's low regenerative capacity, finding an efficacious treatment is still challenging for orthopedics.

Since the pioneering studies based on autologous cell transplantation, regenerative medicine has opened new approaches for cartilage lesion treatment.

Tissue engineering combines cells, biomaterials, and biological factors to regenerate damaged tissues, overcoming conventional therapeutic strategies. Cells synthesize matrix structural components, maintain tissue homeostasis by modulating metabolic, inflammatory, and immunologic pathways. Scaffolds are well acknowledged by clinicians in regenerative applications since they provide the appropriate environment for cells, can be easily implanted, reduce surgical morbidity, allow enhanced cell proliferation, maturation, and an efficient and complete integration with surrounding articular cartilage. Growth factors are molecules that facilitate tissue healing and regeneration by stimulating cell signal pathways.

To date, different cell sources and a wide range of natural and synthetic scaffolds have been used both in pre-clinical and clinical studies with the aim to find the suitable solution for recapitulating cartilage microenvironment and inducing the formation of a new tissue with the biochemical and mechanical properties of the native one. Here, we describe the current concepts for articular cartilage regeneration, highlighting the key actors of this process trying to identify the best perspectives.

[Scanning electron microscope of the human nasal septum]

Objective:Explore the significance of ultrastructural differences in tissue engineering, 3D printing, and rhinoplasty. Methods: 32 specimens （8 vomers, 8 perpendicular plates of ethmoid bone, 8 maxillary nasal crests, and 8 septal cartilage） of the nasal septum from patients with a nasal deviated septum and chronic sinusitis undergoing septoplasty were selected and examined using scanning electron microscopy. Results: The nasal septum of patients of different ages behaves similarly under the scanning electron microscope, and the bones of different parts of the nasal septum have similarities and differences. Conclusion:By observing the scanning electron micrograph of the nasal septum and analyzing the surface ultrastructure, it provides important information for the development of tissue engineering, assists in the refined modeling of 3D printing technology, and provides more ideal restoration materials for clinical operations.

Preclinical studies and clinical trials on mesenchymal stem cell therapy for knee osteoarthritis: A systematic review on models and cell doses

AIM

To provide a systematic analysis of the study design in knee osteoarthritis (OA) preclinical studies, focusing on the characteristics of animal models and cell doses, and to compare these to the characteristics of clinical trials using mesenchymal stem cells (MSCs) for the treatment of knee OA.

METHOD

A systematic and comprehensive search was conducted using the PubMed, Web of Science, Ovid, and Embase electronic databases for research papers published in 2009-2020 on testing MSC treatment in OA animal models. The PubMed database and ClinicalTrials.gov website were used to search for published studies reporting clinical trials of MSC therapy for knee OA.

RESULTS

In total, 9234 articles and two additional records were retrieved, of which 120 studies comprising preclinical and clinical studies were included for analysis. Among the preclinical studies, rats were the most commonly used species for modeling knee OA, and anterior cruciate ligament transection was the most commonly used method for inducing OA. There was a correlation between the cell dose and body weight of the animal. In clinical trials, there was large variation in the dose of MSCs used to treat knee OA, ranging from 1 × 10⁶ to 200 × 10⁶ cells with an average of 37.91 × 10⁶ cells.

CONCLUSION

Mesenchymal stem cells have shown great potential in improving pain relief and tissue protection in both preclinical and clinical studies of knee OA. Further high-quality preclinical and clinical studies are needed to explore the dose effectiveness relationship of MSC therapy and to translate the findings from preclinical studies to humans.

Role of Canonical Wnt/β-Catenin Pathway in Regulating Chondrocytic Hypertrophy in Mesenchymal Stem Cell-Based Cartilage Tissue Engineering

In the past 3 decades, the cartilage repair potential of mesenchymal stromal cells, or mesenchymal stem cells (MSCs), has been widely examined in animal studies. Unfortunately, the phenotype and physical properties of MSC-derived cartilage tissue are not comparable to native hyaline cartilage. In particular, chondrocytic hypertrophy, a phenotype that is not observed in healthy hyaline cartilage, is concomitant with MSC chondrogenesis. Given that hypertrophic chondrocytes potentially undergo apoptosis or convert into osteoblasts, this undesired phenotype needs to be prevented or minimized before MSCs can be used to repair cartilage injuries in the clinic. In this review, we first provide an overview of chondrocytic hypertrophy and briefly summarize current methods for suppressing hypertrophy in MSC-derived cartilage. We then highlight recent progress on modulating the canonical Wnt/β-catenin pathway for inhibiting hypertrophy. Specially, we discuss the potential crosstalk between Wnt/β-catenin with other pathways in regulating hypertrophy. Lastly, we explore future perspectives to further understand the role of Wnt/β-catenin in chondrocytic hypertrophy.

Novel nanocomposite scaffold based on gelatin/PLGA-PEG-PLGA hydrogels embedded with TGF-β1 for chondrogenic differentiation of human dental pulp stem cells in vitro

In the current study, a novel nanocomposite hydrogel scaffold comprising of natural-based gelatin and synthetic-based (poly D, L (lactide-co-glycolide) -b- poly (ethylene glycol)-b- poly D, L (lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymer was developed and loaded with transforming growth factor- β1 (TGF-β1). Synthesized scaffolds' chemical structure was examined by ¹H NMR and ATR-FTIR. Scanning electron microscopy (SEM) confirmed particle size and morphology of the prepared nanoparticles as well as the scaffolds. The morphology analysis revealed a porous interconnected structure throughout the scaffold with a pore size dimension of about 202.05 µm. The swelling behavior, in vitro degradation, mechanical properties, density, and porosity were also evaluated. Phalloidin/DAPI staining was utilized for confirming the extended cytoskeleton of the chondrocytes. Alcian blue staining was conducted to determine cartilaginous matrix sulfated glycosaminoglycan (sGAG) synthesis. Eventually, over a period of 21 days, a real-time RT-PCR analysis was applied to measure the mRNA expression of chondrogenic marker genes, type-II collagen, SOX 9, and aggrecan, in hDPSCs cultured for up to 21 days to study the influence of gelatin/PLGA-PEG-PLGA-TGF-β1 hydrogels on hDPSCs. The findings of the cell-encapsulating hydrogels analysis suggested that the adhesion, viability, and chondrogenic differentiation of hDPSCs improved by gelatin/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogels. These data supported the conclusion that gelatin/PLGA-PEG-PLGA-TGF-β1 nanocomposite hydrogels render the features that allow thein vitrofunctionality of encapsulated hDPSCs and hence can contribute the basis for new effective strategies for the treatment of cartilage injuries.

A 3-Dimensional In Vitro Model of Zonally Organized Extracellular Matrix

OBJECTIVE

Functional cartilage repair requires the new formation of organized hyaline cartilaginous matrix to avoid the generation of fibrous repair tissue. The potential of mesenchymal progenitors was used to assemble a 3-dimensional structure in vitro, reflecting the zonation of collagen matrix in hyaline articular cartilage.

DESIGN

The 3-dimensional architecture of collagen alignment in pellet cultures of chondroprogenitors (CPs) was assessed with Picrosirius red staining analyzed under polarized light. In parallel assays, the trilineage capability was confirmed by calcium deposition during osteogenesis by alizarin S staining and alkaline phosphatase staining. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), mRNA levels of ALP, RUNX2, and BGLAP were assessed after 21 days of osteoinduction. Lipid droplets were stained with oil red O and adipogenic differentiation was confirmed by RT-qPCR analysis of PPARG and LPL gene expression.

RESULTS

Under conditions promoting the chondrogenic signature in self-assembling constructs, CPs formed an aligned extracellular matrix, positive for glycosaminoglycans and collagen type II, showing developing zonation of birefringent collagen fibers along the cross section of pellets, which reflect the distribution of collagen fibers in hyaline cartilage. Induced osteogenic and adipogenic differentiation confirmed the trilineage potential of CPs.

CONCLUSION

This model promotes the differentiation and self-organization of postnatal chondroprogenitors, resulting in the formation of zonally organized engineered hyaline cartilage comparable to the 3 zones of native cartilage.

Mechanical Integrity in a Dynamic Interpenetrating Hydrogel Network of Supramolecular Peptide-Polysaccharide Supports Enhanced Chondrogenesis

Tissue engineering demands intelligently designed scaffolds that encompass the properties of the target tissues in terms of mechanical and bioactive properties. An ideal scaffold for engineering a cartilage tissue should provide the chondrocytes with a favorable 3D microarchitecture apart from possessing optimal mechanical characteristics such as compressibility, energy dissipation, strain stiffening, etc. Herein, we used a unique design approach to develop a hydrogel having a dynamic interpenetrating network to serve as a framework to support chondrocyte growth and differentiation. An amyloid-inspired peptide amphiphile (1) was self-assembled to furnish kinetically controlled nanofibers and incorporated in a dynamic covalently cross-linked polysaccharide network of carboxymethyl cellulose dialdehyde (CMC-D) and carboxymethyl chitosan (CMCh) using Schiff base chemistry. The dynamic noncovalent interaction played a pivotal role in providing the desired modulation in the structure and mechanical properties of the double-network hydrogels that are imperative for cartilage scaffold design. The adaptable nature supported shear-induced extrusion of the hydrogel and facilitated various cellular functions while maintaining its integrity. The potential of the as-developed hydrogels to support in vitro chondrogenesis was explored using human chondrocytes. Evidence of improved cell growth and cartilage-specific ECM production confirmed the potential of the hydrogel to support cartilage tissue engineering while reaffirming the significance of mimicking the biophysical microenvironment to induce optimal tissue regeneration.

Nanocellulose-Based Scaffolds for Chondrogenic Differentiation and Expansion

Nanocellulose deserves special attention among the large group of biocompatible biomaterials. It exhibits good mechanical properties, which qualifies it for potential use as a scaffold imitating cartilage. However, the reconstruction of cartilage is a big challenge due to this tissue's limited regenerative capacity resulting from its lack of vascularization, innervations, and sparsely distributed chondrocytes. This feature restricts the infiltration of progenitor cells into damaged sites. Unfortunately, differentiated chondrocytes are challenging to obtain, and mesenchymal stem cells have become an alternative approach to promote chondrogenesis. Importantly, nanocellulose scaffolds induce the differentiation of stem cells into chondrocyte phenotypes. In this review, we present the recent progress of nanocellulose-based scaffolds promoting the development of cartilage tissue, especially within the emphasis on chondrogenic differentiation and expansion.

Applications of Biocompatible Scaffold Materials in Stem Cell-Based Cartilage Tissue Engineering

Cartilage, especially articular cartilage, is a unique connective tissue consisting of chondrocytes and cartilage matrix that covers the surface of joints. It plays a critical role in maintaining joint durability and mobility by providing nearly frictionless articulation for mechanical load transmission between joints. Damage to the articular cartilage frequently results from sport-related injuries, systemic diseases, degeneration, trauma, or tumors. Failure to treat impaired cartilage may lead to osteoarthritis, affecting more than 25% of the adult population globally. Articular cartilage has a very low intrinsic self-repair capacity due to the limited proliferative ability of adult chondrocytes, lack of vascularization and innervation, slow matrix turnover, and low supply of progenitor cells. Furthermore, articular chondrocytes are encapsulated in low-nutrient, low-oxygen environment. While cartilage restoration techniques such as osteochondral transplantation, autologous chondrocyte implantation (ACI), and microfracture have been used to repair certain cartilage defects, the clinical outcomes are often mixed and undesirable. Cartilage tissue engineering (CTE) may hold promise to facilitate cartilage repair. Ideally, the prerequisites for successful CTE should include the use of effective chondrogenic factors, an ample supply of chondrogenic progenitors, and the employment of cell-friendly, biocompatible scaffold materials. Significant progress has been made on the above three fronts in past decade, which has been further facilitated by the advent of 3D bio-printing. In this review, we briefly discuss potential sources of chondrogenic progenitors. We then primarily focus on currently available chondrocyte-friendly scaffold materials, along with 3D bioprinting techniques, for their potential roles in effective CTE. It is hoped that this review will serve as a primer to bring cartilage biologists, synthetic chemists, biomechanical engineers, and 3D-bioprinting technologists together to expedite CTE process for eventual clinical applications.

Extracellular Vesicles from Mesenchymal Stromal Cells for the Treatment of Inflammation-Related Conditions

Over the past two decades, mesenchymal stromal cells (MSCs) have demonstrated great potential in the treatment of inflammation-related conditions. Numerous early stage clinical trials have suggested that this treatment strategy has potential to lead to significant improvements in clinical outcomes. While promising, there remain substantial regulatory hurdles, safety concerns, and logistical issues that need to be addressed before cell-based treatments can have widespread clinical impact. These drawbacks, along with research aimed at elucidating the mechanisms by which MSCs exert their therapeutic effects, have inspired the development of extracellular vesicles (EVs) as anti-inflammatory therapeutic agents. The use of MSC-derived EVs for treating inflammation-related conditions has shown therapeutic potential in both in vitro and small animal studies. This review will explore the current research landscape pertaining to the use of MSC-derived EVs as anti-inflammatory and pro-regenerative agents in a range of inflammation-related conditions: osteoarthritis, rheumatoid arthritis, Alzheimer's disease, cardiovascular disease, and preeclampsia. Along with this, the mechanisms by which MSC-derived EVs exert their beneficial effects on the damaged or degenerative tissues will be reviewed, giving insight into their therapeutic potential. Challenges and future perspectives on the use of MSC-derived EVs for the treatment of inflammation-related conditions will be discussed.

Trends in Articular Cartilage Tissue Engineering: 3D Mesenchymal Stem Cell Sheets as Candidates for Engineered Hyaline-Like Cartilage

Articular cartilage defects represent an inciting factor for future osteoarthritis (OA) and degenerative joint disease progression. Despite multiple clinically available therapies that succeed in providing short term pain reduction and restoration of limited mobility, current treatments do not reliably regenerate native hyaline cartilage or halt cartilage degeneration at these defect sites. Novel therapeutics aimed at addressing limitations of current clinical cartilage regeneration therapies increasingly focus on allogeneic cells, specifically mesenchymal stem cells (MSCs), as potent, banked, and available cell sources that express chondrogenic lineage commitment capabilities. Innovative tissue engineering approaches employing allogeneic MSCs aim to develop three-dimensional (3D), chondrogenically differentiated constructs for direct and immediate replacement of hyaline cartilage, improve local site tissue integration, and optimize treatment outcomes. Among emerging tissue engineering technologies, advancements in cell sheet tissue engineering offer promising capabilities for achieving both in vitro hyaline-like differentiation and effective transplantation, based on controlled 3D cellular interactions and retained cellular adhesion molecules. This review focuses on 3D MSC-based tissue engineering approaches for fabricating “ready-to-use” hyaline-like cartilage constructs for future rapid in vivo regenerative cartilage therapies. We highlight current approaches and future directions regarding development of MSC-derived cartilage therapies, emphasizing cell sheet tissue engineering, with specific focus on regulating 3D cellular interactions for controlled chondrogenic differentiation and post-differentiation transplantation capabilities.

A brief very-low oxygen tension regimen is sufficient for the early chondrogenic commitment of human adipose-derived mesenchymal stem cells

PURPOSE

The aim of this study was to evaluate the effects exerted over chondrogenic commitment of human adipose-derived mesenchymal stem cells (ADSCs) by a very low oxygen tension (<1% pO₂).

MATERIALS/METHODS

Cell morphology, mRNA levels of chondrocyte-specific marker genes and the involvement of p38 MAPK signalling were monitored in human ADSCs under a very low oxygen tension.

RESULTS

Cell morphology was significantly changed after two days of hypoxic preconditioning when they featured as elongated spindle-shaped cells. SRY-box containing gene 9, aggrecan and collagen type II mRNA levels were enhanced under severe hypoxic culture conditions. Moreover, the inhibition of p38 MAPK resulted in a substantial reduction in transcription of the above-mentioned specific genes, proving the pivotal role of this pathway in the transcriptional regulation of chondrogenesis.

CONCLUSIONS

Here, we propose a protocol showing the early commitment of stem cells towards the chondrogenic phenotype in only 2 days of culture via a very low hypoxic environment, in the absence of growth factors added in the culture medium.

Development of Standardized Fetal Progenitor Cell Therapy for Cartilage Regenerative Medicine: Industrial Transposition and Preliminary Safety in Xenogeneic Transplantation

Diverse cell therapy approaches constitute prime developmental prospects for managing acute or degenerative cartilaginous tissue affections, synergistically complementing specific surgical solutions. Bone marrow stimulation (i.e., microfracture) remains a standard technique for cartilage repair promotion, despite incurring the adverse generation of fibrocartilagenous scar tissue, while matrix-induced autologous chondrocyte implantation (MACI) and alternative autologous cell-based approaches may partly circumvent this effect. Autologous chondrocytes remain standard cell sources, yet arrays of alternative therapeutic biologicals present great potential for regenerative medicine. Cultured human epiphyseal chondro-progenitors (hECP) were proposed as sustainable, safe, and stable candidates for chaperoning cartilage repair or regeneration. This study describes the development and industrial transposition of hECP multi-tiered cell banking following a single organ donation, as well as preliminary preclinical hECP safety. Optimized cell banking workflows were proposed, potentially generating millions of safe and sustainable therapeutic products. Furthermore, clinical hECP doses were characterized as non-toxic in a standardized chorioallantoic membrane model. Lastly, a MACI-like protocol, including hECPs, was applied in a three-month GLP pilot safety evaluation in a caprine model of full-thickness articular cartilage defect. The safety of hECP transplantation was highlighted in xenogeneic settings, along with confirmed needs for optimal cell delivery vehicles and implantation techniques favoring effective cartilage repair or regeneration.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles - Silver Linings for Cartilage Regeneration?

As the world's population is aging, the incidence of the degenerative disease Osteoarthritis (OA) is increasing. Current treatment options of OA focus on the alleviation of the symptoms including pain and inflammation rather than on restoration of the articular cartilage. Cell-based therapies including the application of mesenchymal stromal cells (MSCs) have been a promising tool for cartilage regeneration approaches. Due to their immunomodulatory properties, their differentiation potential into cells of the mesodermal lineage as well as the plurality of sources from which they can be isolated, MSCs have been applied in a vast number of studies focusing on the establishment of new treatment options for Osteoarthritis. Despite promising outcomes in vitro and in vivo, applications of MSCs are connected with teratoma formation, limited lifespan of differentiated cells as well as rejection of the cells after transplantation, highlighting the need for new cell free approaches harboring the beneficial properties of MSCs. It has been demonstrated that the regenerative potential of MSCs is mediated by the release of paracrine factors rather than by differentiation into cells of the desired tissue. Besides soluble factors, extracellular vesicles are the major component of a cell's secretome. They represent novel mechanisms by which (pathogenic) signals can be communicated between cell types as they deliver bioactive molecules (nucleic acids, proteins, lipids) from the cell of origin to the target cell leading to specific biological processes upon uptake. This review will give an overview about extracellular vesicles including general characteristics, isolation methods and characterization approaches. Furthermore, the role of MSC-derived extracellular vesicles in in vitro and in vivo studies for cartilage regeneration will be summarized with special focus on transported miRNA which either favored the progression of OA or protected the cartilage from degradation. In addition, studies will be reviewed investigating the impact of MSC-derived extracellular vesicles on inflammatory arthritis. As extracellular vesicles are present in all body fluids, their application as potential biomarkers for OA will also be discussed in this review. Finally, studies exploring the combination of MSC-derived extracellular vesicles with biomaterials for tissue engineering approaches are summarized.

Two-Year Follow-Up and Remodeling Kinetics of ChonDux Hydrogel for Full-Thickness Cartilage Defect Repair in the Knee

OBJECTIVE

To determine performance and repair kinetics of the ChonDux hydrogel scaffold for treating focal articular cartilage defects in the knee over 24 months.

DESIGN

This assessor-blinded trial evaluates ChonDux hydrogel scaffold implantation in combination with microfracture in 18 patients across 6 sites. Male and female patients 18 to 65 years of age with full-thickness femoral condyle defects 2 to 4 cm² in area were enrolled. Eligible patients received ChonDux treatment followed by rehabilitation. Defect volume fill was evaluated after 3, 6 (primary outcome), 12, 18, and 24 months by assessor blinded magnetic resonance imaging (MRI) analysis. Secondary outcomes were T2-weighted MRI relaxation time and patient surveys via visual analogue scale (VAS) pain and International Knee Documentation Committee (IKDC) knee function scoring.

RESULTS

ChonDux maintained durable tissue restoration over 24 months with final defect percent fill of 94.2% ± 16.3% and no significant loss of fill volume at any time points. Tissues treated with ChonDux maintained T2 relaxation times similar to uninjured cartilage between 12 and 24 months. VAS pain scoring decreased between 1 and 6 weeks, and IKDC knee function scores improved by approximately 30.1 with ChonDux over 24 months.

CONCLUSION

ChonDux treatment is a safe adjunct to microfracture therapy and promotes stable restoration of full thickness articular cartilage defects for at least 24 months.

Engineering 3D functional tissue constructs using self-assembling cell-laden microniches

Tissue engineering using traditional size fixed scaffolds and injectable biomaterials are faced with many limitations due to the difficulties of producing macroscopic functional tissues. In this study, 3D functional tissue constructs were developed by inducing self-assembly of microniches, which were cell-laden gelatin microcryogels. During self-assembly, the accumulation of extracellular matrix (ECM) components was found to strengthen cell-cell and cell-ECM interactions, leading to the construction of a 'native' microenvironment that better preserved cell viability and functions. MSCs grown in self-assembled constructs showed increased maintenance of stemness, reduced senescence and improved paracrine activity compared with cells grown in individual microniches without self-assembly. As an example of applying the self-assembled constructs in tissue regeneration, the constructs were used to induce in vivo articular cartilage repair and successfully regenerated hyaline-like cartilage tissue in the absence of other extrinsic factors. This unique approach of developing self-assembled 3D functional constructs holds great promise for the generation of tissue engineered organoids and repair of challenging tissue defects. STATEMENT OF SIGNIFICANCE: We developed 3D functional tissue constructs using a unique gelatin-based microscopic hydrogel (microcryogels). Mesenchymal stem cells (MSCs) were loaded into gelatin microcryogels to form microscopic cell-laden units (microniches), which were induced to undergo self-assembly using a specially designed 3D printed frame. Extracellular matrix accumulation among the microniches resulted in self-assembled macroscopic constructs with superior ability to maintain the phenotypic characteristics and stemness of MSCs, together with the suppression of senescence and enhanced paracrine function. As an example of application in tissue regeneration, the self-assembled constructs were shown to successfully repair articular cartilage defects without any other supplements. This unique strategy for developing 3D functional tissue constructs allows the optimisation of stem cell functions and construction of biomimetic tissue organoids.

Development of Poly(2-Methacryloyloxyethyl Phosphorylcholine)-Functionalized Hydrogels for Reducing Protein and Bacterial Adsorption

A series of hydrogels with intrinsic antifouling properties was prepared via surface-functionalization of poly(2-hydroxyethyl methacrylate) [p(HEMA)]-based hydrogels with the biomembrane-mimicking zwitterionic polymer, poly(2-methacryloyloxyethyl phosphorylcholine) [p(MPC)]. The p(MPC)-modified hydrogels have enhanced surface wettability, high water content retention (61.0%-68.3%), and good transmittance (>90%). Notably, the presence of zwitterionic MPC moieties at the hydrogel surfaces lowered the adsorption of proteins such as lysozyme and bovine serum albumin (BSA) by 73%-74% and 59%-66%, respectively, and reduced bacterial adsorption by approximately 10%-73% relative to the unmodified control. The anti-biofouling properties of the p(MPC)-functionalized hydrogels are largely attributed to the dense hydration layer formed at the hydrogel surfaces by the zwitterionic moieties. Overall, the results demonstrate that biocompatible and antifouling hydrogels based on p(HEMA)-p(MPC) structures have promising potential for application in biomedical materials.

Development of a Three-Dimensional Bioengineered Platform for Articular Cartilage Regeneration

Degenerative cartilage pathologies are nowadays a major problem for the world population. Factors such as age, genetics or obesity can predispose people to suffer from articular cartilage degeneration, which involves severe pain, loss of mobility and consequently, a loss of quality of life. Current strategies in medicine are focused on the partial or total replacement of affected joints, physiotherapy and analgesics that do not address the underlying pathology. In an attempt to find an alternative therapy to restore or repair articular cartilage functions, the use of bioengineered tissues is proposed. In this study we present a three-dimensional (3D) bioengineered platform combining a 3D printed polycaprolactone (PCL) macrostructure with RAD16-I, a soft nanofibrous self-assembling peptide, as a suitable microenvironment for human mesenchymal stem cells' (hMSC) proliferation and differentiation into chondrocytes. This 3D bioengineered platform allows for long-term hMSC culture resulting in chondrogenic differentiation and has mechanical properties resembling native articular cartilage. These promising results suggest that this approach could be potentially used in articular cartilage repair and regeneration.

Resveratrol Effect on Adipose-Derived Stem Cells Differentiation to Chondrocyte in Three-Dimensional Culture

Purpose: Adipose stem cells (ASCs) are pluripotent cells with the ability of self-renewal and differentiation into different types of mesenchymal cells. As cartilage repair is difficult due to lack of blood capillary, resveratrol (Res) is a polyphenolic compound with diverse biological properties to be possibly used in this case. The aim of the present study was to investigate the effect of Res on differentiation of ASCs into chondrocyte in a three-dimensional (3D) culture model.

Methods: Subcutaneous adipose tissues were prepared and digested enzymatically, and passed through cell strainer. ASCs were harvested in the fourth passage, and divided into five groups. The control group received chondrogenic differentiation medium (CDM) while the experimental groups received CDM plus different doses of Res (1, 10, 20, and 50 µM) for 21 days. Expression of cartilage specific genes and Sirtuin1 (SIRT 1), cell viability, apoptosis and ferric reducing antioxidant power (FRAP) were detected using reverse transcription polymerase chain reaction (RT-PCR), MTT assay, TUNEL and acridine orange/ethidium bromide (AO/EB) staining. One-way ANOVA and non-parametric Mann-Whitney U test were used for data analyses.

Results: ASCs were differentiated to chondrocyte by CDM in a three-dimensional culture. 10 and 20 µM doses of Res showed the most proliferating effect on ADSCs. The SIRT 1 genes expression and FRAP level also increased significantly compared to the control group (P<0.05). Also, OD of cell increased whereas apoptosis decreased.

Conclusion: 3D culture was a suitable condition for ASCs differentiation to chondrocyte, and lower doses of Res exert proliferation effect on ASCs.

Enhanced Antiarthritic Efficacy by Nanoparticles of (-)-Epigallocatechin Gallate-Glucosamine-Casein

This work aims to improve the antiarthritic activity of (-)-epigallocatechin gallate (EGCG) and glucosamine (GA) through fabrication and optimization of casein protein nanoparticles (EGC-NPs). Optimized EGC-NPs were obtained with a EGCG/GA/casein ratio of 1:2:8 (w/w/w). The EGC-NPs gave a mean size of 186 ± 3.5 nm and an entrapment efficiency of 86.8 ± 2.7%, and they exhibited a greater inhibitory activity against human fibroblast-like synoviocytes-osteoarthritis cells and human fibroblast-like synoviocytes-rheumatoid arthritis cells compared with that of the EGCG-GA mixture by 33.5% and 20.8%, respectively. Freeze-dried EGC-NPs stored at 25 °C during 12 months showed high dispersion stability. Moreover, the redispersion of the freeze-dried EGC-NPs produced almost no significant changes in their physicochemical properties and bioactivity. Rat experiments demonstrated that the antiarthritis effect of the EGC-NPs was significantly higher than that of EGCG-GA mixture, as assessed through an analysis of anti-inflammatory efficacy, radiographic images and histopathological assessments of paw joints, and immunohistochemical changes in serum cytokines. The enchanced antiarthritic activity in vivo was consistent with that in vitro. The EGC-NPs demonstrate potential as a food supplement for the treatment of arthritis.

Recent advances in cell sheet technology for bone and cartilage regeneration: from preparation to application

Bone defects caused by trauma, tumour resection, infection and congenital deformities, together with articular cartilage defects and cartilage-subchondral bone complex defects caused by trauma and degenerative diseases, remain great challenges for clinicians. Novel strategies utilising cell sheet technology to enhance bone and cartilage regeneration are being developed. The cell sheet technology has shown great clinical potential in regenerative medicine due to its effective preservation of cell-cell connections and extracellular matrix and its scaffold-free nature. This review will first introduce several widely used cell sheet preparation systems, including traditional approaches and recent improvements, as well as their advantages and shortcomings. Recent advances in utilising cell sheet technology to regenerate bone or cartilage defects and bone-cartilage complex defects will be reviewed. The key challenges and future research directions for the application of cell sheet technology in bone and cartilage regeneration will also be discussed.

Biophysical Stimuli: A Review of Electrical and Mechanical Stimulation in Hyaline Cartilage

OBJECTIVE

Hyaline cartilage degenerative pathologies induce morphologic and biomechanical changes resulting in cartilage tissue damage. In pursuit of therapeutic options, electrical and mechanical stimulation have been proposed for improving tissue engineering approaches for cartilage repair. The purpose of this review was to highlight the effect of electrical stimulation and mechanical stimuli in chondrocyte behavior.

DESIGN

Different information sources and the MEDLINE database were systematically revised to summarize the different contributions for the past 40 years.

RESULTS

It has been shown that electric stimulation may increase cell proliferation and stimulate the synthesis of molecules associated with the extracellular matrix of the articular cartilage, such as collagen type II, aggrecan and glycosaminoglycans, while mechanical loads trigger anabolic and catabolic responses in chondrocytes.

CONCLUSION

The biophysical stimuli can increase cell proliferation and stimulate molecules associated with hyaline cartilage extracellular matrix maintenance.

Stem Cell-Derived Extracellular Vesicles for Treating Joint Injury and Osteoarthritis

Extracellular vesicles (EVs) are nanoscale particles secreted by almost all cell types to facilitate intercellular communication. Stem cell-derived EVs theoretically have the same biological functions as stem cells, but offer the advantages of small size, low immunogenicity, and removal of issues such as low cell survival and unpredictable long-term behaviour associated with direct cell transplantation. They have been an area of intense interest in regenerative medicine, due to the potential to harness their anti-inflammatory and pro-regenerative effects to induce healing in a wide variety of tissues. However, the potential of using stem cell-derived EVs for treating joint injury and osteoarthritis has not yet been extensively explored. The pathogenesis of osteoarthritis, with or without prior joint injury, is not well understood, and there is a longstanding unmet clinical need to develop new treatments that provide a therapeutic effect in preventing or stopping joint degeneration, rather than merely relieving the symptoms of the disease. This review summarises the current evidence relating to stem cell-derived EVs in joint injury and osteoarthritis, providing a concise discussion of their characteristics, advantages, therapeutic effects, limitations and outlook in this exciting new area.

Identification of endogenous migratory MSC-like cells and their interaction with the implant materials guiding osteochondral defect repair

Abundant BMSCs and MSC-like cells move up to the defect area and interact with the implant materials, guiding the osteochondral defect repair.

Preparation of Polymeric and Composite Scaffolds by 3D Bioprinting

Over the recent years, the advent of 3D bioprinting technology has marked a milestone in osteochondral tissue engineering (TE) research. Nowadays, the traditional used techniques for osteochondral regeneration remain to be inefficient since they cannot mimic the complexity of joint anatomy and tissue heterogeneity of articular cartilage. These limitations seem to be solved with the use of 3D bioprinting which can reproduce the anisotropic extracellular matrix (ECM) and heterogeneity of this tissue. In this chapter, we present the most commonly used 3D bioprinting approaches and then discuss the main criteria that biomaterials must meet to be used as suitable bioinks, in terms of mechanical and biological properties. Finally, we highlight some of the challenges that this technology must overcome related to osteochondral bioprinting before its clinical implementation.

Particulated Autograft Cartilage Implantation for the Treatment of Osteochondral Lesions of the Talus: A Novel Technique

Osteochondral lesions of the talus often occur following ankle sprains and fractures. Operative intervention is typically required because of the diminished intrinsic repair capability of talar articular cartilage. Several techniques have evolved that emphasize replacing the defect with cartilage that closely mimics the biological properties of hyaline articular cartilage. The goals of operative treatment are resolution of symptoms, physiologic healing, and restoration of function while eliminating the need for further intervention. This article describes a novel, single-step technique for the treatment of osteochondral lesions of the talus with the use of particulated autograft cartilage implantation.

LEVELS OF EVIDENCE

Level V.

Anti-inflammatory effect of hesperidin enhances chondrogenesis of human mesenchymal stem cells for cartilage tissue repair

Background

Articular cartilage diseases are considered a major health problem, and tissue engineering using human mesenchymal stem cells (MSCs) have been shown as a promising solution for cartilage tissue repair. Hesperidin is a flavonoid extract from citrus fruits with anti-inflammatory properties. We aimed to investigate the effect of hesperidin on MSCs for cartilage tissue repair. MSCs were treated by hesperidin, and colony formation and proliferation assays were performed to evaluate self-renewal ability of MSCs. Alcian blue staining and Sox9 expression were measured to evaluate chondrogenesis of MSCs. Secretion of pro-inflammatory cytokines IFN-γ, IL-2, IL-4 and IL-10, and expression of nuclear factor kappa B (NF-κB) subunit p65 were also assessed.

Results

Hesperidin improved self-renewal ability and chondrogenesis of MSCs, inhibited secretion of pro-inflammatory cytokines IFN-γ, IL-2, IL-4 and IL-10, and suppressed the expression of p65. Overexpression of p65 was able to reverse the hesperidin inhibited secretions of pro-inflammatory cytokines, and abolish the enhancing effect of hesperidin on chondrogenesis of MSCs.

Conclusion

Hesperidin could serve as a therapeutic agent to effectively enhance chondrogenesis of human MSCs by inhibiting inflammation to facilitate cartilage tissue repair.

Nanofibrous scaffolds for biomedical applications

Tissue engineering is an emergent and very interesting research field, providing potential solutions for a myriad of challenges in healthcare. Fibrous scaffolds specifically have shown promise as an effective tissue engineering method, as their high length-to-width ratio mimics that of extracellular matrix components, which in turn guides tissue formation, promotes cellular adhesion and improves mechanical properties. In this review paper, we discuss in detail both the importance of fibrous scaffolds for the promotion of tissue growth and the different methods to produce fibrous biomaterials to possess favorable and unique characteristics. Here, we focus on the pressing need to develop biomimetic structures that promote an ideal environment to encourage tissue formation. In addition, we discuss different biomedical applications in which fibrous scaffolds can be useful, identifying their importance, relevant aspects, and remaining significant challenges. In conclusion, we provide comments on the future direction of fibrous scaffolds and the best way to produce them, proposed in light of recent technological advances and the newest and most promising fabrication techniques.

Effects of mechanical loading on human mesenchymal stem cells for cartilage tissue engineering

Today, articular cartilage damage is a major health problem, affecting people of all ages. The existing conventional articular cartilage repair techniques, such as autologous chondrocyte implantation (ACI), microfracture, and mosaicplasty, have many shortcomings which negatively affect their clinical outcomes. Therefore, it is essential to develop an alternative and efficient articular repair technique that can address those shortcomings. Cartilage tissue engineering, which aims to create a tissue-engineered cartilage derived from human mesenchymal stem cells (MSCs), shows great promise for improving articular cartilage defect therapy. However, the use of tissue-engineered cartilage for the clinical therapy of articular cartilage defect still remains challenging. Despite the importance of mechanical loading to create a functional cartilage has been well demonstrated, the specific type of mechanical loading and its optimal loading regime is still under investigation. This review summarizes the most recent advances in the effects of mechanical loading on human MSCs. First, the existing conventional articular repair techniques and their shortcomings are highlighted. The important parameters for the evaluation of the tissue-engineered cartilage, including chondrogenic and hypertrophic differentiation of human MSCs are briefly discussed. The influence of mechanical loading on human MSCs is subsequently reviewed and the possible mechanotransduction signaling is highlighted. The development of non-hypertrophic chondrogenesis in response to the changing mechanical microenvironment will aid in the establishment of a tissue-engineered cartilage for efficient articular cartilage repair.