Supporting Biomaterials for Articular Cartilage Repair

Agarose Hydrogels for Bone Tissue Engineering, from Injectables to Bioprinting

A great interest in agarose, with many health-promoting and gel properties, has been registered, especially in the field of bone regeneration and repair. Agarose and its major bioactive compounds are involved in biological activities such as inflammation, cell adhesion and proliferation, and the promotion of tissue repair. Due to its unique physical properties like gelation and solubility, agarose is increasingly utilized in the medical industry. The aim of this review is to present an overview of the applications of agarose hydrogels in bone tissue engineering, introducing agarose and its modified products as innovative solutions for bone regeneration. Additionally, the injectability of agarose hydrogels and their applications in bioprinting are also summarized. Data indicate that agarose will play an increasing role in current and future global medical sectors.

Engineering with Biomedical Sciences Changing the Horizon of Healthcare-A Review

In the dynamic realm of healthcare, the convergence of engineering and biomedical sciences has emerged as a pivotal frontier. In this review we go into specific areas of innovation, including medical imaging and diagnosis, developments in biomedical sensors, and drug delivery systems. Wearable biosensors, non-wearable biosensors, and biochips, which include gene chips, protein chips, and cell chips, are all included in the scope of the topic that pertains to biomedical sensors. Extensive research is conducted on drug delivery systems, spanning topics such as the integration of computer modeling, the optimization of drug formulations, and the design of delivery devices. Furthermore, the paper investigates intelligent drug delivery methods, which encompass stimuli-responsive systems such as temperature, redox, pH, light, enzyme, and magnetic responsive systems. In addition to that, the review goes into topics such as tissue engineering, regenerative medicine, biomedical robotics, automation, biomechanics, and the utilization of green biomaterials. The purpose of this analysis is to provide insights that will enhance continuing research and development efforts in engineering-driven biomedical breakthroughs, ultimately contributing to the improvement of healthcare. These insights will be provided by addressing difficulties and highlighting future prospects.

Injectable Janus Base Nanomatrix (JBNm) in Maintaining Long-Term Homeostasis of Regenerated Cartilage for Tissue Chip Applications

Engineered cartilage tissues have wide applications in in vivo cartilage repair as well as in vitro models, such as cartilage-on-a-chip or cartilage tissue chips. Currently, most cartilage tissue engineering approaches focus on promoting chondrogenesis of stem cells to produce regenerated cartilage. However, this regenerated cartilage can dedifferentiate into fibrotic tissue or further differentiate into hypertrophic or calcified cartilage. One of the most challenging objectives in cartilage tissue engineering is to maintain long-term cartilage homeostasis. Since the microenvironment of engineered cartilage tissue is crucial for stem cell adhesion, proliferation, differentiation, and function, we aim to develop a novel scaffold that can maintain the long-term homeostasis of regenerated cartilage. Therefore, we developed a library of Janus base nanomatrices (JBNms), composed of DNA-inspired Janus nanotubes (JBNts) as well as cartilage extracellular matrix (ECM) proteins. The JBNms were developed to selectively promote chondro-lineage cell functions while inhibiting bone and endothelial cell growth. More importantly, the JBNm can effectively promote chondrogenesis while inhibiting hypertrophy, osteogenesis, angiogenesis, and dedifferentiation. Additionally, the JBNm is injectable, forming a solid scaffold suitable for producing and maintaining regenerated cartilage tissue in microfluidic chips, making it ideal for tissue chip applications. In this study, we successfully created cartilage tissue chips using JBNms. These chips can model cartilage tissue even after long-term culture and can also mimic arthritis progression, making them useful for drug screening. Thus, we have developed a novel nanomaterial approach for improved cartilage tissue engineering and cartilage tissue chip applications.

Polysaccharide base electrospun nanofibrous scaffolds for cartilage tissue engineering: Challenges and opportunities

Polysaccharides, known as naturally abundant macromolecular materials which can be easily modified chemically, have always attracted scientists' interest due to their outstanding properties in tissue engineering. Moreover, their intrinsic similarity to cartilage ECM components, biocompatibility, and non-harsh processing conditions make polysaccharides an excellent option for cartilage tissue engineering. Imitating the natural ECM structure to form a fibrous scaffold at the nanometer scale in order to recreate the optimal environment for cartilage regeneration has always been attractive for researchers in the past few years. However, there are some challenges for polysaccharides electrospun nanofibers preparation, such as poor solubility (Alginate, cellulose, chitin), high viscosity (alginate, chitosan, and Hyaluronic acid), high surface tension, etc. Several methods are reported in the literature for facing polysaccharide electrospinning issues, such as using carrier polymers, modification of polysaccharides, and using different solvent systems. In this review, considering the importance of polysaccharide-based electrospun nanofibers in cartilage tissue engineering applications, the main achievements in the past few years, and challenges for their electrospinning process are discussed. After careful investigation of reported studies in the last few years, alginate, chitosan, hyaluronic acid, chondroitin sulfate, and cellulose were chosen as the main polysaccharide base electrospun nanofibers used for cartilage regeneration.

Tissue engineering strategies hold promise for the repair of articular cartilage injury

Articular cartilage damage and wear can result in cartilage degeneration, ultimately culminating in osteoarthritis. Current surgical interventions offer limited capacity for cartilage tissue regeneration and offer only temporary alleviation of symptoms. Tissue engineering strategies are increasingly recognized as promising modalities for cartilage restoration. Currently, various biological scaffolds utilizing tissue engineering materials are extensively employed in both fundamental and clinical investigations of cartilage repair. In order to optimize the cartilage repair ability of tissue engineering scaffolds, researchers not only optimize the structure and properties of scaffolds from the perspective of materials science and manufacturing technology to enhance their histocompatibility, but also adopt strategies such as loading cells, cytokines, and drugs to promote cartilage formation. This review provides an overview of contemporary tissue engineering strategies employed in cartilage repair, as well as a synthesis of existing preclinical and clinical research. Furthermore, the obstacles faced in the translation of tissue engineering strategies to clinical practice are discussed, offering valuable guidance for researchers seeking to address these challenges.

A review of advanced hydrogels for cartilage tissue engineering

With the increase in weight and age of the population, the consumption of tobacco, inappropriate foods, and the reduction of sports activities in recent years, bone and joint diseases such as osteoarthritis (OA) have become more common in the world. From the past until now, various treatment strategies (e.g., microfracture treatment, Autologous Chondrocyte Implantation (ACI), and Mosaicplasty) have been investigated and studied for the prevention and treatment of this disease. However, these methods face problems such as being invasive, not fully repairing the tissue, and damaging the surrounding tissues. Tissue engineering, including cartilage tissue engineering, is one of the minimally invasive, innovative, and effective methods for the treatment and regeneration of damaged cartilage, which has attracted the attention of scientists in the fields of medicine and biomaterials engineering in the past several years. Hydrogels of different types with diverse properties have become desirable candidates for engineering and treating cartilage tissue. They can cover most of the shortcomings of other treatment methods and cause the least secondary damage to the patient. Besides using hydrogels as an ideal strategy, new drug delivery and treatment methods, such as targeted drug delivery and treatment through mechanical signaling, have been studied as interesting strategies. In this study, we review and discuss various types of hydrogels, biomaterials used for hydrogel manufacturing, cartilage-targeting drug delivery, and mechanosignaling as modern strategies for cartilage treatment.

Engineered biochemical cues of regenerative biomaterials to enhance endogenous stem/progenitor cells (ESPCs)-mediated articular cartilage repair

As a highly specialized shock-absorbing connective tissue, articular cartilage (AC) has very limited self-repair capacity after traumatic injuries, posing a heavy socioeconomic burden. Common clinical therapies for small- to medium-size focal AC defects are well-developed endogenous repair and cell-based strategies, including microfracture, mosaicplasty, autologous chondrocyte implantation (ACI), and matrix-induced ACI (MACI). However, these treatments frequently result in mechanically inferior fibrocartilage, low cost-effectiveness, donor site morbidity, and short-term durability. It prompts an urgent need for innovative approaches to pattern a pro-regenerative microenvironment and yield hyaline-like cartilage with similar biomechanical and biochemical properties as healthy native AC. Acellular regenerative biomaterials can create a favorable local environment for AC repair without causing relevant regulatory and scientific concerns from cell-based treatments. A deeper understanding of the mechanism of endogenous cartilage healing is furthering the (bio)design and application of these scaffolds. Currently, the utilization of regenerative biomaterials to magnify the repairing effect of joint-resident endogenous stem/progenitor cells (ESPCs) presents an evolving improvement for cartilage repair. This review starts by briefly summarizing the current understanding of endogenous AC repair and the vital roles of ESPCs and chemoattractants for cartilage regeneration. Then several intrinsic hurdles for regenerative biomaterials-based AC repair are discussed. The recent advances in novel (bio)design and application regarding regenerative biomaterials with favorable biochemical cues to provide an instructive extracellular microenvironment and to guide the ESPCs (e.g. adhesion, migration, proliferation, differentiation, matrix production, and remodeling) for cartilage repair are summarized. Finally, this review outlines the future directions of engineering the next-generation regenerative biomaterials toward ultimate clinical translation.

Extracellular matrix composition analysis of human articular cartilage for the development of organ-on-a-chip

INTRODUCTION

Articular cartilage has a complex extracellular matrix (ECM) that provides it a defined architecture for its load-bearing properties. The complete understanding of ECM components is imperative for developing biomimetic organ-on-a-chip tissue construct.

OBJECTIVE

This study aimed to decellularize and characterize the ECM for its protein profiling to generate a niche for enhanced chondrocyte proliferation.

METHODS

Articular cartilage scrapings were subjected to mechanical and collagenase digestion, followed by sodium dodecyl sulfate (SDS) treatment for 8 h and 16 h. The de-cellularization efficiency was confirmed by hematoxylin & eosin, alcian blue, masson's trichrome staining, and scanning electron microscopy (SEM). The ECM protein profile was quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS) using a bottom-up approach.

RESULTS

Histological characterization revealed void lacunae that lacked staining for cellular components. The ECM, sulfated glycosaminoglycan content, and collagen fibers were preserved after 8 h and 16 h of de-cellularization. The SEM ultrastructure images showed that few chondrocytes adhered to the ECM after 8 h and cell-free ECM after 16 h of de-cellularization. LC-MS/MS analysis identified 66 proteins with heterotypic collagen types COL1A1-COL6A1, COL14A1, COL22A1 and COL25A1 showed moderate fold change and expression levels, while COL18A1, COL26A1, chondroitin sulfate, matrix metalloproteinase-9 (MMP9), fibronectin, platelet glycoprotein 1 beta alpha (GP1BA), vimentin, bone morphogenetic protein 6 (BMP6), fibroblast growth factor 4 (FGF4) and growth hormone receptor (GHR) showed maximum fold change and expression levels.

CONCLUSIONS

The standardized de-cellularization process could preserve majority of ECM components, providing structural integrity and architecture to the ECM. The Identified proteins quantified for their expression levels provided insight into engineering the ECM composition for developing cartilage-on-a-chip.

The role of three-dimensional scaffolds based on polyglycerol sebacate/ polycaprolactone/ gelatin in the presence of Nanohydroxyapatite in promoting chondrogenic differentiation of human adipose-derived mesenchymal stem cells

BACKGROUND

Tissue engineering for cartilage regeneration has made great advances in recent years, although there are still challenges to overcome. This study aimed to evaluate the chondrogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs) on three-dimensional scaffolds based on polyglycerol sebacate (PGS) / polycaprolactone (PCL) / gelatin(Gel) in the presence of Nanohydroxyapatite (nHA).

MATERIALS AND METHODS

In this study, a series of nHA-nanocomposite scaffolds were fabricated using 100:0:0, 60:40:0, and 60:20:20 weight ratios of PGS to PCL: Gel copolymers through salt leaching method. The morphology and porosity of prepared samples was characterized by SEM and EDX mapping analysis. Also, the dynamic contact angle and PBS adsorption tests are used to identify the effect of copolymerization and nanoparticles on scaffolds' hydrophilicity. The hydrolytic degradation properties were also analyzed. Furthermore, cell viability and proliferation as well as cell adhesion are evaluated to find out the biocompatibility. To determine the potential ability of nHA-nanocomposite scaffolds in chondrogenic differentiation, RT-PCR assay was performed to monitor the expression of collagen II, aggrecan, and Sox9 genes as markers of cartilage differentiation.

RESULTS

The nanocomposites had an elastic modulus within a range of 0.71-1.30 MPa and 0.65-0.43 MPa, in dry and wet states, respectively. The PGS/PCL sample showed a water contact angle of 72.44 ± 2.2°, while the hydrophilicity significantly improved by adding HA nanoparticles. It was found from the hydrolytic degradation study that HA incorporation can accelerate the degradation rate compared with PGS and PGS/PCL samples. Furthermore, the in vitro biocompatibility tests showed significant cell attachment, proliferation, and viability of adipose-derived mesenchymal stem cells (ADMSCs). RT-PCR also indicated a significant increase in collagen II, aggrecan and Sox9 mRNA levels.

CONCLUSIONS

Our findings demonstrated that these nanocomposite scaffolds promote the differentiation of hADSCs into chondrocytes possibly by the increase in mRNA levels of collagen II, aggrecan, and Sox9 as markers of chondrogenic differentiation. In conclusion, the addition of PCL, Gelatin, and HA into PGS is a practical approach to adjust the general features of PGS to prepare a promising scaffold for cartilage tissue engineering.

Finite Element Analysis of Different Osseocartilaginous Reconstruction Techniques in Animal Model Knees

Lesions of the articular cartilage are frequent in all age populations and lead to functional impairment. Multiple surgical techniques have failed to provide an effective method for cartilage repair. The aim of our research was to evaluate the effect of two different compression forces on three types of cartilage repair using finite element analysis (FEA). Initially, an in vivo study was performed on sheep. The in vivo study was prepared as following: Case 0-control group, without cartilage lesion; Case 1-cartilage lesion treated with macro-porous collagen implants; Case 2-cartilage lesion treated with collagen implants impregnated with bone marrow concentrate (BMC); Case 3-cartilage lesion treated with collagen implants impregnated with adipose-derived stem cells (ASC). Using the computed tomography (CT) data, virtual femur-cartilage-tibia joints were created for each Case. The study showed better results in bone changes when using porous collagen implants impregnated with BMC or ASC stem cells for the treatment of osseocartilaginous defects compared with untreated macro-porous implant. After 7 months postoperative, the presence of un-resorbed collagen influences the von Mises stress distribution, total deformation, and displacement on the Z axis. The BMC treatment was superior to ASC cells in bone tissue morphology, resembling the biomechanics of the control group in all FEA simulations.

Biological Scaffolds Assembled with Magnetic Nanoparticles for Bone Tissue Engineering: A Review

Superparamagnetic iron oxide nanoparticles (SPION) are widely used in bone tissue engineering because of their unique physical and chemical properties and their excellent biocompatibility. Under the action of a magnetic field, SPIONs loaded in a biological scaffold can effectively promote osteoblast proliferation, differentiation, angiogenesis, and so on. SPIONs have very broad application prospects in bone repair, bone reconstruction, bone regeneration, and other fields. In this paper, several methods for forming biological scaffolds via the biological assembly of SPIONs are reviewed, and the specific applications of these biological scaffolds in bone tissue engineering are discussed.

Recent Advances in 3D Printing of Photocurable Polymers: Types, Mechanism, and Tissue Engineering Application

The conversion of liquid resin into solid structures upon exposure to light of a specific wavelength is known as photopolymerization. In recent years, photopolymerization-based 3D printing has gained enormous attention for constructing complex tissue-specific constructs. Due to the economic and environmental benefits of the biopolymers employed, photo-curable 3D printing is considered an alternative method for replacing damaged tissues. However, the lack of suitable bio-based photopolymers, their characterization, effective crosslinking strategies, and optimal printing conditions are hindering the extensive application of 3D printed materials in the global market. This review highlights the present status of various photopolymers, their synthesis, and their optimization parameters for biomedical applications. Moreover, a glimpse of various photopolymerization techniques currently employed for 3D printing is also discussed. Furthermore, various naturally derived nanomaterials reinforced polymerization and their influence on printability and shape fidelity are also reviewed. Finally, the ultimate use of those photopolymerized hydrogel scaffolds in tissue engineering is also discussed. Taken together, it is believed that photopolymerized 3D printing has a great future, whereas conventional 3D printing requires considerable sophistication, and this review can provide readers with a comprehensive approach to developing light-mediated 3D printing for tissue-engineering applications.

Combinatorial Effect of Mesenchymal Stem Cells and Extracellular Vesicles in a Hydrogel on Cartilage Regeneration

BACKGROUND

Mesenchymal stem cells (MSCs) are used for tissue regeneration due to their wide differentiation capacity and anti-inflammatory effects. Extracellular vesicles (EVs) derived from MSCs are also known for their regenerative effects as they contain nucleic acids, proteins, lipids, and cytokines similar to those of parental cells. There are several studies on the use of MSCs or EVs for tissue regeneration. However, the combinatorial effect of human MSCs (hMSCs) and EVs is not clear. In this study, we investigated the combinatorial effect of hMSCs and EVs on cartilage regeneration via co-encapsulation in a hyaluronic-acid (HA)-based hydrogel.

METHODS

A methacrylic-acid-based HA hydrogel was prepared to encapsulate hMSCs and EVs in hydrogels. Through in vitro and in vivo analyses, we investigated the chondrogenic potential of the HA hydrogel-encapsulated with hMSCs and EVs.

RESULTS

Co-encapsulation of hMSCs with EVs in the HA hydrogel increased the chondrogenic differentiation of hMSCs and regeneration of damaged cartilage tissue compared with that of the HA hydrogel loaded with hMSCs only.

CONCLUSION

Co-encapsulation of hMSCs and EVs in the HA hydrogel effectively enhances cartilage tissue regeneration due to the combinatorial therapeutic effect of hMSCs and EVs. Thus, in addition to cartilage tissue regeneration for the treatment of osteoarthritis, this approach would be a useful strategy to improve other types of tissue regeneration.

Microcarriers in application for cartilage tissue engineering: Recent progress and challenges

Successful regeneration of cartilage tissue at a clinical scale has been a tremendous challenge in the past decades. Microcarriers (MCs), usually used for cell and drug delivery, have been studied broadly across a wide range of medical fields, especially the cartilage tissue engineering (TE). Notably, microcarrier systems provide an attractive method for regulating cell phenotype and microtissue maturations, they also serve as powerful injectable carriers and are combined with new technologies for cartilage regeneration. In this review, we introduced the typical methods to fabricate various types of microcarriers and discussed the appropriate materials for microcarriers. Furthermore, we highlighted recent progress of applications and general design principle for microcarriers. Finally, we summarized the current challenges and promising prospects of microcarrier-based systems for medical applications. Overall, this review provides comprehensive and systematic guidelines for the rational design and applications of microcarriers in cartilage TE.

Synthesis and Characterization of a Novel Composite Scaffold Based on Hyaluronic Acid and Equine Type I Collagen

Herein, the synthesis and characterization of a novel composite biopolymer scaffold—based on equine type I collagen and hyaluronic acid—were described by using a reaction in heterogeneous phase. The resulting biomimetic structure was characterized in terms of chemical, physical, and cytotoxicity properties using human-derived lymphocytes and chondrocytes. Firstly, FT-IR data proved a successful reticulation of hyaluronic acid within collagen structure with the appearance of a new peak at a wavenumber of 1735 cm⁻¹ associated with ester carbonyl stretch. TGA and DSC characterizations confirmed different thermal stability of cross-linked scaffolds while morphological analysis by scanning electron microscopy (SEM) suggested the presence of a highly porous structure with open and interconnected void areas suitable for hosting cells. The enzymatic degradation profile confirmed scaffold higher endurance with collagenase as compared with collagen alone. However, it was particularly interesting that the mechanical behavior of the composite scaffold showed an excellent shape memory, especially when it was hydrated, with an improved Young’s modulus of 9.96 ± 0.53 kPa (p ≤ 0.001) as well as a maximum load at 97.36 ± 3.58 kPa compared to the simple collagen scaffold that had a modulus of 1.57 ± 0.08 kPa and a maximum load of 36.91 ± 0.24 kPa. Finally, in vitro cytotoxicity confirmed good product safety with human lymphocytes (viability of 81.92 ± 1.9 and 76.37 ± 1.2 after 24 and 48 h, respectively), whereas excellent gene expression profiles of chondrocytes with a significant upregulation of SOX9 and ACAN after 10 days of culture indicated our scaffold’s ability of preserving chondrogenic phenotype. The described material could be considered a potential tool to be implanted in patients with cartilage defects.

Biomimetic approach to articular cartilage tissue engineering using carbon nanotube-coated and textured polydimethylsiloxane scaffolds

There is a significant need to understand the complexity and heterogeneity of articular cartilage to develop more effective therapeutic strategies for diseases such as osteoarthritis. Here, we show that carbon nanotubes (CNTs) are excellent candidates as a material for synthetic scaffolds to support the growth of chondrocytes—the cells that produce and maintain cartilage. Chondrocyte morphology, proliferation, and alignment were investigated as nanoscale CNT networks were applied to macroscopically textured polydimethylsiloxane (PDMS) scaffolds. The application of CNTs to the surface of PDMS‐based scaffolds resulted in an up to 10‐fold increase in cell adherence and 240% increase in proliferation, which is attributable to increased nanoscale roughness and hydrophilicity. The introduction of macroscale features to PDMS induced alignment of chondrocytes, successfully mimicking the cell behavior observed in the superficial layer of cartilage. Raman spectroscopy was used as a noninvasive, label‐free method to monitor extracellular matrix production and chondrocyte phenotype. Chondrocytes on these scaffolds successfully produced collagen, glycosaminoglycan, and aggrecan. This study demonstrates that introducing physical features at different length scales allows for a high level of control over tissue scaffold design and, thus, cell behavior. Ultimately, these textured scaffolds can serve as platforms to improve the understanding of osteoarthritis and for early‐stage therapeutic testing.

Does the Choice of Acellular Scaffold and Augmentation With Bone Marrow Aspirate Concentrate Affect Short-term Outcomes in Cartilage Repair? A Systematic Review and Meta-analysis

BACKGROUND

Matrix-induced chondrogenesis (MIC) is a promising treatment option for critical-size cartilage lesions of the knee; however, there exists substantial heterogeneity in the choice of acellular scaffold matrix for MIC cartilage repairs.

HYPOTHESIS

The choice of acellular matrix will not affect patient outcomes after MIC cartilage repair procedures, and the addition of concentrated bone marrow aspirate (cBMA) will improve short-term patient outcomes regardless of matrix choice.

STUDY DESIGN

Meta-analysis; Level of evidence, 4.

METHODS

Studies were stratified by matrix type: multilayered, single layered, and gel based. Continuous outcomes were analyzed with pairwise meta-analysis using the inverse variance model with random effects applied. Binary outcomes were analyzed as pooled proportions in a single-arm fashion; after which, reconstruction of relative risks (RRs) with confidence intervals was performed using the Katz logarithmic method.

RESULTS

A total of 876 patients were included: 469 received multilayered bioscaffolds; 238, gel-based scaffolds; and 169, single-layered scaffolds. The mean age of patients was 36.2 years (95% CI, 33.9 to 38.4), while the mean lesion size was 3.91 cm² (95% CI, 3.40 to 4.42). The weighted mean follow-up was 23.8 months (95% CI, 20.1 to 27.6). Multilayered bioscaffolds were most effective at improving visual analog scale scores (P = .03; weighted mean difference [WMD], -4.44 [95% CI, -4.83 to -4.06]; P < .001). There were significantly lower risks of incomplete defect filling for gel-based scaffolds when compared with multilayered scaffolds (RR, 0.78 [95% CI, 0.69 to 0.88]; P < .001) and single-layered scaffolds (RR, 0.58 [95% CI, 0.41 to 0.81]; P = .001). Augmentation with cBMA further improved clinical scores across all scaffolds, with significant improvements in Tegner score (P = .02), while decreasing incomplete defect filling rates as well. There was significantly greater improvement in visual analog scale scores (P = .01) for single-layered scaffolds with cBMA augmentation (WMD, -4.88 [95% CI, -5.38 to -4.37]; P < .001) as compared with single-layered scaffolds without cBMA augmentation (WMD, -4.08 [95% CI, -4.46 to -3.71]; P < .001). All significant improvements were below their respective minimum clinically important differences.

CONCLUSION

While cartilage repair with acellular scaffolds provides significant improvements in pain and function for patients, there is insufficient clinical evidence to suggest which scaffold material is the most superior in influencing such improvements. The enhancement of cartilage repair procedures with cBMA may provide further functional improvements and improve defect filling; however, more long-term evidence is required to evaluate the effects.

Methods of Modification of Mesenchymal Stem Cells and Conditions of Their Culturing for Hyaline Cartilage Tissue Engineering

The use of mesenchymal stromal cells (MSCs) for tissue engineering of hyaline cartilage is a topical area of regenerative medicine that has already entered clinical practice. The key stage of this procedure is to create conditions for chondrogenic differentiation of MSCs, increase the synthesis of hyaline cartilage extracellular matrix proteins by these cells and activate their proliferation. The first such works consisted in the indirect modification of cells, namely, in changing the conditions in which they are located, including microfracturing of the subchondral bone and the use of 3D biodegradable scaffolds. The most effective methods for modifying the cell culture of MSCs are protein and physical, which have already been partially introduced into clinical practice. Genetic methods for modifying MSCs, despite their effectiveness, have significant limitations. Techniques have not yet been developed that allow studying the effectiveness of their application even in limited groups of patients. The use of MSC modification methods allows precise regulation of cell culture proliferation, and in combination with the use of a 3D biodegradable scaffold, it allows obtaining a hyaline-like regenerate in the damaged area. This review is devoted to the consideration and comparison of various methods used to modify the cell culture of MSCs for their use in regenerative medicine of cartilage tissue.

A Comprehensive Analysis of SE-lncRNA/mRNA Differential Expression Profiles During Chondrogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Objective: Articular cartilage injury is common and difficult to treat clinically because of the characteristics of the cartilage. Bone marrow-derived mesenchymal stem cell (BMSC)-mediated cartilage regeneration is a promising therapy for treating articular cartilage injury. BMSC differentiation is controlled by numerous molecules and signaling pathways in the microenvironment at both the transcriptional and post-transcriptional levels. However, the possible function of super enhancer long non-coding RNAs (SE-lncRNAs) in the chondrogenic differentiation of BMSCs is still unclear. Our intention was to explore the expression profile of SE-lncRNAs and potential target genes regulated by SE-lncRNAs during chondrogenic differentiation in BMSCs.

Materials and Methods: In this study, we conducted a human Super-Enhancer LncRNA Microarray to investigate the differential expression profile of SE-lncRNAs and mRNAs during chondrogenic differentiation of BMSCs. Subsequent bioinformatic analysis was performed to clarify the important signaling pathways, SE-lncRNAs, and mRNAs associated with SE-lncRNAs regulating the chondrogenic differentiation of BMSCs.

Results: A total of 77 SE-lncRNAs were identified, of which 47 were upregulated and 30 were downregulated during chondrogenic differentiation. A total of 308 mRNAs were identified, of which 245 were upregulated and 63 were downregulated. Some pathways, such as focal adhesion, extracellular matrix (ECM)–receptor interaction, transforming growth factor-β (TGF-β) signaling pathway, and PI3K–Akt signaling pathway, were identified as the key pathways that may be implicated in the chondrogenic differentiation of BMSCs. Moreover, five potentially core regulatory mRNAs (PMEPA1, ENC1, TES, CDK6, and ADIRF) and 37 SE-lncRNAs in chondrogenic differentiation were identified by bioinformatic analysis.

Conclusion: We assessed the differential expression levels of SE-lncRNAs and mRNAs, along with the chondrogenic differentiation of BMSCs. By analyzing the interactions and co-expression, we identified the core SE-lncRNAs and mRNAs acting as regulators of the chondrogenic differentiation potential of BMSCs. Our study also provided novel insights into the mechanism of BMSC chondrogenic and cartilage regeneration.

Silk Fiber-Reinforced Hyaluronic Acid-Based Hydrogel for Cartilage Tissue Engineering

A continuing challenge in cartilage tissue engineering for cartilage regeneration is the creation of a suitable synthetic microenvironment for chondrocytes and tissue regeneration. The aim of this study was to develop a highly tunable hybrid scaffold based on a silk fibroin matrix (SM) and a hyaluronic acid (HA) hydrogel. Human articular chondrocytes were embedded in a porous 3-dimensional SM, before infiltration with tyramine modified HA hydrogel. Scaffolds were cultured in chondropermissive medium with and without TGF-β1. Cell viability and cell distribution were assessed using CellTiter-Blue assay and Live/Dead staining. Chondrogenic marker expression was detected using qPCR. Biosynthesis of matrix compounds was analyzed by dimethylmethylene blue assay and immuno-histology. Differences in biomaterial stiffness and stress relaxation were characterized using a one-step unconfined compression test. Cell morphology was investigated by scanning electron microscopy. Hybrid scaffold revealed superior chondro-inductive and biomechanical properties compared to sole SM. The presence of HA and TGF-β1 increased chondrogenic marker gene expression and matrix deposition. Hybrid scaffolds offer cytocompatible and highly tunable properties as cell-carrier systems, as well as favorable biomechanical properties.

In Vivo Cartilage Regeneration with Cell-Seeded Natural Biomaterial Scaffold Implants: 15-Year Study

Articular cartilage can be easily damaged from human's daily activities, leading to inflammation and to osteoarthritis, a situation that can diminish the patients' quality of life. For larger cartilage defects, scaffolds are employed to provide cells the appropriate three-dimensional environment to proliferate and differentiate into healthy cartilage tissue. Natural biomaterials used as scaffolds, attract researchers' interest because of their relative nontoxic nature, their abundance as natural products, their easy combination with other materials, and the relative easiness to establish Marketing Authorization. The last 15 years were chosen to review, document, and elucidate the developments on cell-seeded natural biomaterials for articular cartilage treatment in vivo. The parameters of the experimental designs and their results were all documented and presented. Considerations about the newly formed cartilage and the treatment of cartilage defects were discussed, along with difficulties arising when applying natural materials, research limitations, and tissue engineering approaches for hyaline cartilage regeneration.

Advanced Multi-Dimensional Cellular Models as Emerging Reality to Reproduce In Vitro the Human Body Complexity

A hot topic in biomedical science is the implementation of more predictive in vitro models of human tissues to significantly improve the knowledge of physiological or pathological process, drugs discovery and screening. Bidimensional (2D) culture systems still represent good high-throughput options for basic research. Unfortunately, these systems are not able to recapitulate the in vivo three-dimensional (3D) environment of native tissues, resulting in a poor in vitro–in vivo translation. In addition, intra-species differences limited the use of animal data for predicting human responses, increasing in vivo preclinical failures and ethical concerns. Dealing with these challenges, in vitro 3D technological approaches were recently bioengineered as promising platforms able to closely capture the complexity of in vivo normal/pathological tissues. Potentially, such systems could resemble tissue-specific extracellular matrix (ECM), cell–cell and cell–ECM interactions and specific cell biological responses to mechanical and physical/chemical properties of the matrix. In this context, this review presents the state of the art of the most advanced progresses of the last years. A special attention to the emerging technologies for the development of human 3D disease-relevant and physiological models, varying from cell self-assembly (i.e., multicellular spheroids and organoids) to the use of biomaterials and microfluidic devices has been given.

The treatment of articular cartilage injuries with mesenchymal stem cells in different animal species

One of the major problems observed in veterinary practice is articular cartilage injuries in animals. In terms of agriculture, it leads to their culling from the herd, even if they are highly productive animals. With companion animals, owners usually have to decide between euthanasia or long-term sometimes lifelong treatment of the injury by a veterinarian. The use of mesenchymal stem cells (MSCs) for the treatment of cartilage injury in veterinary medicine is based on the good results observed in preclinical studies, where large animals have been used as experimental models to study the regenerative activity of MSCs. According to the literature, MSCs in veterinary medicine have been used to treat cartilage injury of dogs and horses, whereas sheep and goats are generally models for reproducing the disease in preclinical experimental studies.

3D printed gelatin/hydroxyapatite scaffolds for stem cell chondrogenic differentiation and articular cartilage repair

The hUCB-MSC-laden 3D printed gelatin/HAP scaffold effectively repairs knee cartilage defects in a pig model.

Cartilage tissue engineering for obesity-induced osteoarthritis: Physiology, challenges, and future prospects

Osteoarthritis (OA) is a multifactorial joint disease with pathological changes that affect whole joint tissue. Obesity is acknowledged as the most influential risk factor for both the initiation and progression of OA in weight-bearing and non-weight-bearing joints. Obesity-induced OA is a newly defined phenotypic group in which chronic low-grade inflammation has a central role. Aside from persistent chronic inflammation, abnormal mechanical loading due to increased body weight on weight-bearing joints is accountable for the initiation and progression of obesity-induced OA. The current therapeutic approaches for OA are still evolving. Tissue-engineering-based strategy for cartilage regeneration is one of the most promising treatment breakthroughs in recent years. However, patients with obesity-induced OA are often excluded from cartilage repair attempts due to the abnormal mechanical demands, altered biomechanical and biochemical activities of cells, persistent chronic inflammation, and other obesity-associated factors. With the alarming increase in the number of obese populations globally, the need for an innovative therapeutic approach that could effectively repair and restore the damaged synovial joints is of significant importance for this sub-population of patients. In this review, we discuss the involvement of the systemic and localized inflammatory response in obesity-induced OA and the impact of altered mechanical loading on pathological changes in the synovial joint. Moreover, we examine the current strategies in cartilage tissue engineering and address the critical challenges of cell-based therapies for OA. Besides, we provide examples of innovative ways and potential strategies to overcome the obstacles in the treatment of obesity-induced OA.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Altogether, this review delivers insight into obesity-induced OA and offers future research direction on the creation of tissue engineering-based therapies for obesity-induced OA.

Paracrine Interactions Involved in Human Induced Pluripotent Stem Cells Differentiation into Chondrocytes

Osteoarthritis (OA), as a degenerative joint disease, is the most common form of joint disorder that causes pain, stiffness, and other symptoms associated with OA. Various genetic, biomechanical, and environmental factors have a relevant role in the development of OA. To date, extensive efforts are currently being made to overcome the poor self-healing capacity of articular cartilage. Despite the pivotal role of chondrocytes, their proliferation and repair capacity after tissue injury are limited. Therefore, the development of new strategies to overcome these constraints is urgently needed. Recent advances in regenerative medicine suggest that pluripotent stem cells are promising stem cell sources for cartilage repair. Pluripotent stem cells are undifferentiated cells that have the capacity to differentiate into different types of cells and can self-renew indefinitely. In the past few decades, numerous attempts have been made to regenerate articular cartilage by using induced pluripotent stem cells (iPSCs). The potential applications of patient-specific iPSCs hold great promise for regenerative medicine and OA treatment. However, there are different culture conditions for the preparation and characterization of human iPSCs-derived chondrocytes (hiChondrocytes). Recent biochemical analyses reported that several paracrine factors such as TGFb, BMPs, WNT, Ihh, and Runx have been shown to be involved in cartilage cell proliferation and differentiation from human iPSCs. In this review, we summarize and discuss the paracrine interactions involved in human iPSCs differentiation into chondrocytes in different cell culture media.

Extraction and Characterization of Collagen from Elasmobranch Byproducts for Potential Biomaterial Use

With the worldwide increase of fisheries, fish wastes have had a similar increase, alternatively they can be seen as a source of novel substances for the improvement of society's wellbeing. Elasmobranchs are a subclass fished in high amounts, with some species being mainly bycatch. They possess an endoskeleton composed mainly by cartilage, from which chondroitin sulfate is currently obtained. Their use as a viable source for extraction of type II collagen has been hypothesized with the envisaging of a biomedical application, namely in biomaterials production. In the present work, raw cartilage from shark (Prionace glauca) and ray (Zeachara chilensis and Bathyraja brachyurops) was obtained from a fish processing company and submitted to acidic and enzymatic extractions, to produce acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). From all the extractions, P. glauca PSC had the highest yield (3.5%), followed by ray ASC (0.92%), ray PSC (0.50%), and P. glauca ASC (0.15%). All the extracts showed similar properties, with the SDS-PAGE profiles being compatible with the presence of both type I and type II collagens. Moreover, the collagen extracts exhibited the competence to maintain their conformation at human basal temperature, presenting a denaturation temperature higher than 37 °C. Hydrogels were produced using P. glauca PSC combined with shark chondroitin sulfate, with the objective of mimicking the human cartilage extracellular matrix. These hydrogels were cohesive and structurally-stable at 37 °C, with rheological measurements exhibiting a conformation of an elastic solid when submitted to shear strain with a frequency up to 4 Hz. This work revealed a sustainable strategy for the valorization of fisheries' by-products, within the concept of a circular economy, consisting of the use of P. glauca, Z. chilensis, and B. brachyurops cartilage for the extraction of collagen, which would be further employed in the development of hydrogels as a proof of concept of its biotechnological potential, ultimately envisaging its use in marine biomaterials to regenerate damaged cartilaginous tissues.

Bioprinting of Collagen: Considerations, Potentials, and Applications

Collagen is the most abundant extracellular matrix protein that is widely used in tissue engineering (TE). There is little research done on printing pure collagen. To understand the bottlenecks in printing pure collagen, it is imperative to understand collagen from a bottom-up approach. Here it is aimed to provide a comprehensive overview of collagen printing, where collagen assembly in vivo and the various sources of collagen available for TE application are first understood. Next, the current printing technologies and strategy for printing collagen-based materials are highlighted. Considerations and key challenges faced in collagen printing are identified. Finally, the key research areas that would enhance the functionality of printed collagen are presented.

Biological perspectives and current biofabrication strategies in osteochondral tissue engineering

Articular cartilage and the underlying subchondral bone are crucial in human movement and when damaged through disease or trauma impacts severely on quality of life. Cartilage has a limited regenerative capacity due to its avascular composition and current therapeutic interventions have limited efficacy. With a rapidly ageing population globally, the numbers of patients requiring therapy for osteochondral disorders is rising, leading to increasing pressures on healthcare systems. Research into novel therapies using tissue engineering has become a priority. However, rational design of biomimetic and clinically effective tissue constructs requires basic understanding of osteochondral biological composition, structure, and mechanical properties. Furthermore, consideration of material design, scaffold architecture, and biofabrication strategies, is needed to assist in the development of tissue engineering therapies enabling successful translation into the clinical arena. This review provides a starting point for any researcher investigating tissue engineering for osteochondral applications. An overview of biological properties of osteochondral tissue, current clinical practices, the role of tissue engineering and biofabrication, and key challenges associated with new treatments is provided. Developing precisely engineered tissue constructs with mechanical and phenotypic stability is the goal. Future work should focus on multi-stimulatory environments, long-term studies to determine phenotypic alterations and tissue formation, and the development of novel bioreactor systems that can more accurately resemble the in vivo environment.

Reconstruction of Large Osteochondral Defects Using a Hemicondylar Aragonite-Based Implant in a Caprine Model

PURPOSE

To investigate the safety and regenerative potential of a hemicondylar aragonite-based scaffold in the reconstruction of large osteochondral lesions occupying an extensive portion of the medial femoral condyle in a goat model.

METHODS

Eight Saanen goats were treated by the implantation of an aragonite-based scaffold (size: 19 × 8 × 8 mm) on a previously prepared hemicondylar osteochondral defect located in the right medial femoral condyle of the knee. Goats were euthanized after 12 months and the specimens underwent X-ray imaging, macroscopic, micro-computed tomography, histology, and immunohistochemistry evaluations to assess subchondral bone and cartilage regeneration.

RESULTS

In all 8 goats, no adverse event or persistent inflammation was observed. The evaluations performed showed integration of the scaffold, which almost completely resorbed at 12 months. In all animals, no signs of osteoarthritis progression were seen. Concurrent regeneration of the osteochondral unit was observed, with trabecular bone tissue replacing the implant and restoring the subchondral layer, and the formation of an overlying hyaline cartilage surface, well integrated within the surrounding native tissue, also was observed.

CONCLUSIONS

The use of the hemicondylar biphasic aragonite-based implant in the treatment of osteochondral defects in the goat model proved to be technically feasible and safe. The scaffold degraded and was replaced by regenerated tissue within the 12-month study period, restoring the osteochondral unit both at the level of the cartilaginous layer and the subchondral bone.

CLINICAL RELEVANCE

The present animal study describes a scaffold-based procedure for the treatment of large condylar defects, which often require massive allograft or unicompartmental replacement. The aragonite-based implant promoted a regeneration of both cartilage and subchondral bone, and its use as a "biologic" unicondylar prosthesis might be feasible also in the clinical setting.

The role of SIRT1 in BMP2-induced chondrogenic differentiation and cartilage maintenance under oxidative stress

Articular cartilage defects are common in the clinic but difficult to treat. Exploring the chondrogenic molecular mechanisms of mesenchymal stem cells (MSCs) is of great theoretical interest and industrial significance. Bone morphogenetic protein 2 (BMP2) is a key factor that induces cartilage differentiation and can induce stem cell chondrogenic differentiation. However, the oxidative stress in the microenvironment during cartilage injury and degeneration inhibits cartilage regeneration and homeostasis. Silent mating type information regulator 2 homolog-1 (SIRT1) is an important histone deacetylase that regulates proliferation, differentiation, aging, and inflammation processes; moreover, it is an essential factor for chondrogenesis. The specific mechanism of SIRT1 in cartilage differentiation and homeostasis is still unclear. First, we investigated whether SIRT1 could coordinate BMP2-induced chondrogenic differentiation. Second, we investigated the protective effect of SIRT1 on BMP2-induced MSCs under oxidative stress. The results showed that SIRT1 could promote BMP2-induced chondrogenic differentiation of MSCs, and reduce the apoptosis and decomposition of extracellular matrix under oxidative stress. In summary, these results suggested that SIRT1 plays an important coordination role in BMP2-induced chondrogenic differentiation of stem cells and cartilage maintenance under oxidative stress, establishing the experimental basis for exploring the use of SIRT1 in cartilage defect repair.

Bone Marrow Aspirate Concentrate: Its Uses in Osteoarthritis

Human bone marrow (BM) is a kind of source of mesenchymal stem cells (MSCs) as well as growth factors and cytokines that may aid anti-inflammation and regeneration for various tissues, including cartilage and bone. However, since MSCs in BM usually occupy only a small fraction (0.001%) of nucleated cells, bone marrow aspirate concentrate (BMAC) for cartilage pathologies, such as cartilage degeneration, defect, and osteoarthritis, have gained considerable recognition in the last few years due to its potential benefits including disease modifying and regenerative capacity. Although further research with well-designed, randomized, controlled clinical trials is needed to elucidate the exact mechanism of BMAC, this may have the most noteworthy effect in patients with osteoarthritis. The purpose of this article is to review the general characteristics of BMAC, including its constituent, action mechanisms, and related issues. Moreover, this article aims to summarize the clinical outcomes of BMAC reported to date.

Studies of proliferation and chondrogenic differentiation of rat adipose stem cells using an anti-oxidative polyurethane scaffold combined with cyclic compression culture

The adipose stem cell is a potential candidate for the autologous chondrocytes repairing approach because of the abundance of fat in the animal body and its versatile differentiation capability. In this study, rat adipose stem cells (rASCs) were seeded into anti-oxidative N-acetylcysteine (NAC) grafted polyurethane (PU) scaffold and then combined with short dynamic compressive stimulation (24 h) to induce rASCs chondrogenesis differentiation in vitro. The inner pore surface of the PU scaffold was first modified via alginate and type I collagen to promote rASCs adherence. The modified layers crosslinked by genipin showed outstanding stability after ultrasonic treatment, indicating the modified layers were stable and can keep the cells adhesion well during dynamic compressive stimulation. After inner pore surface modification and 10 mM NAC grafting, the PU scaffold-A-C-G (graft 10 mM NAC) has shown the best proliferation efficiency with homogeneous cell distribution after 72hr static culture. After short term dynamic compressive stimulation, significant gene expression in chondrogenic markers, Sox-9, and Aggrecan, were noted in both PU scaffold-A-C-G and PU scaffold-A-C-G (graft 10 mM NAC). Considering the cell proliferation efficiency and gene expression, the anti-oxidative NAC grafted PU scaffold combined with short term dynamic compressive stimulation could be useful for cell culturing in stem cell therapy.

Micropatterned Biphasic Nanocomposite Platform for Maintaining Chondrocyte Morphology

One major limitation hindering the translation of in vitro osteoarthritis research into clinical disease-modifying therapies is that chondrocytes rapidly spread and dedifferentiate under standard monolayer conditions. Current strategies to maintain rounded morphologies of chondrocytes in culture either unnaturally restrict adhesion and place chondrocytes in an excessively stiff mechanical environment or are impractical for use in many applications. To address the limitations of current techniques, we have developed a unique composite thin-film cell culture platform, the CellWell, to model articular cartilage that utilizes micropatterned hemispheroidal wells, precisely sized to fit individual cells (12-18 μm diameters), to promote physiologically spheroidal chondrocyte morphologies while maintaining compatibility with standard cell culture and analytical techniques. CellWells were constructed of 15-μm-thick 5% agarose films embedded with electrospun poly(vinyl alcohol) (PVA) nanofibers. Transmission electron microscope (TEM) images of PVA nanofibers revealed a mean diameter of 60.9 ± 24 nm, closely matching the observed 53.8 ± 29 nm mean diameter of human ankle collagen II fibers. Using AFM nanoindentation, CellWells were found to have compressive moduli of 158 ± 0.60 kPa at 15 μm/s indentation, closely matching published stiffness values of the native pericellular matrix. Primary human articular chondrocytes taken from ankle cartilage were seeded in CellWells and assessed at 24 h. Chondrocytes maintained their rounded morphology in CellWells (mean aspect ratio of 0.87 ± 0.1 vs three-dimensional (3D) control [0.86 ± 0.1]) more effectively than those seeded under standard conditions (0.65 ± 0.3), with average viability of >85%. The CellWell's design, with open, hemispheroidal wells in a thin film substrate of physiological stiffness, combines the practical advantages of two-dimensional (2D) culture systems with the physiological advantages of 3D systems. Through its ease of use and ability to maintain the physiological morphology of chondrocytes, we expect that the CellWell will enhance the clinical translatability of future studies conducted using this culture platform.

Experimental and numerical study on the performance of printed alginate/hyaluronic acid/halloysite nanotube/polyvinylidene fluoride bio-scaffolds

The growing usage of printed bio scaffolds in the field of regenerative medicine has made this field very important in biomedical engineering. In this regard, three-dimensional printing (3D) technique needs bio-materials with higher mechanical and biological performance. The biomaterials with high mechanical performance beside its bio compatibility are limited. A novel bio-material made of Alginate, Hyaluronic acid, Halloysite Nanotube and Polyvinylidene Fluoride was used and characterized for printing cartilage bio scaffolds through numerical studies. CaCl2 was used for crosslinking of biomaterial. Scanning Electron Microscopy, mechanical tests (tensile and compressive test), MTT assay were conducted for evaluating this novel biomaterial. Different structures of bio material were simulated for numerical studies. The numerical study was performed in ANSYS 18 using three parameter Mooney-Rivlin model. According to experimental and numerical results, Halloysite Nanotube increases the tensile and compressive strength of biomaterial up to 47%. Results show that biomaterial have good mechanical performance due to mechanical forces required for cartilage bio scaffolds besides its high biological performance. Polyvinylidene fluoride reduces the mechanical performance while increasing the cell viability. MTT assay results performed on day 0, day 2 and day 6 show increase in cell number to be about twice for biomaterial containing 40 mg/ml alginate, 40 mg/ml halloysite nanotube, 10 mg/ml hyaluronic acid and 1 w/v Polyvinylidene fluoride. Numerical simulation shows high mechanical performance of bio material in different scaffolds structure. The best structure of bio scaffolds was achieved with 0.4 mm nozzle diameter and 0.4 space between rows.

Polymer- and Hybrid-Based Biomaterials for Interstitial, Connective, Vascular, Nerve, Visceral and Musculoskeletal Tissue Engineering

In this review, materials based on polymers and hybrids possessing both organic and inorganic contents for repairing or facilitating cell growth in tissue engineering are discussed. Pure polymer based biomaterials are predominantly used to target soft tissues. Stipulated by possibilities of tuning the composition and concentration of their inorganic content, hybrid materials allow to mimic properties of various types of harder tissues. That leads to the concept of "one-matches-all" referring to materials possessing the same polymeric base, but different inorganic content to enable tissue growth and repair, proliferation of cells, and the formation of the ECM (extra cellular matrix). Furthermore, adding drug delivery carriers to coatings and scaffolds designed with such materials brings additional functionality by encapsulating active molecules, antibacterial agents, and growth factors. We discuss here materials and methods of their assembly from a general perspective together with their applications in various tissue engineering sub-areas: interstitial, connective, vascular, nervous, visceral and musculoskeletal tissues. The overall aims of this review are two-fold: (a) to describe the needs and opportunities in the field of bio-medicine, which should be useful for material scientists, and (b) to present capabilities and resources available in the area of materials, which should be of interest for biologists and medical doctors.

Animal mesenchymal stem cell research in cartilage regenerative medicine - a review

Healing of articular cartilage is a major clinical challenge as it also lacks a direct vasculature and nerves, and carries a limited number of resident chondrocytes that do not proliferate easily. Damaged articular cartilages are usually replaced by fibrocartilages, which are mechanically and structurally weaker and less resilient. Regenerative medicine involving stem cells is considered to have a definitive potential to overcome the limitations associated with the currently available surgical methods of cartilage repair. Among various stem cell types, mesenchymal stem cells (MSCs) are preferred for clinical applications. These cells can be readily derived from various sources and have the ability to trans-differentiate into various tissue-specific cells, including those of the cartilage by the process of chondrogenesis. Compared to embryonic or induced pluripotent stem cells (iPSCs), no ethical or teratogenic issues are associated with MSCs. These stem cells are being extensively evaluated for the treatment of joint affections and the results appear promising. Unlike human medicine, in veterinary medicine, the literature on stem cell research for cartilage regeneration is limited. This review, therefore, aims to comprehensively discuss the available literature and pinpoint the achievements and limitations associated with the use of MSCs for articular cartilage repair in animal species.

The Use of Nanomaterials in Tissue Engineering for Cartilage Regeneration; Current Approaches and Future Perspectives

The repair and regeneration of articular cartilage represent important challenges for orthopedic investigators and surgeons worldwide due to its avascular, aneural structure, cellular arrangement, and dense extracellular structure. Although abundant efforts have been paid to provide tissue-engineered grafts, the use of therapeutically cell-based options for repairing cartilage remains unsolved in the clinic. Merging a clinical perspective with recent progress in nanotechnology can be helpful for developing efficient cartilage replacements. Nanomaterials, < 100 nm structural elements, can control different properties of materials by collecting them at nanometric sizes. The integration of nanomaterials holds promise in developing scaffolds that better simulate the extracellular matrix (ECM) environment of cartilage to enhance the interaction of scaffold with the cells and improve the functionality of the engineered-tissue construct. This technology not only can be used for the healing of focal defects but can also be used for extensive osteoarthritic degenerative alterations in the joint. In this review paper, we will emphasize the recent investigations of articular cartilage repair/regeneration via biomaterials. Also, the application of novel technologies and materials is discussed.

The interplay between chondrocyte spheroids and mesenchymal stem cells boosts cartilage regeneration within a 3D natural-based hydrogel

Articular cartilage (AC) lacks the ability to self-repair and cell-based approaches, primarily based on using chondrocytes and mesenchymal stem cells (MSCs), are emerging as effective technology to restore cartilage functionality, because cells synergic functionality may support the maintenance of chondrogenic phenotype and promote extracellular matrix regeneration. This work aims to develop a more physiologically representative co-culture system to investigate the influence of MSCs on the activity of chondrocytes. A thermo-sensitive chitosan-based hydrogel, ionically crosslinked with β-glycerophosphate, is optimised to obtain sol/gel transition at physiological conditions within 5 minutes, high porosity with pores diameter <30 µm, and in vitro mechanical integrity with compressive and equilibrium Young's moduli of 37 kPa and 17 kPa, respectively. Live/dead staining showed that after 1 and 3 days in culture, the encapsulated MSCs into the hydrogels are viable and characterised by round-like morphology. Furthermore chondrocyte spheroids, seeded on top of gels that contained either MSCs or no cells, show that the encapsulated MSCs stimulate chondrocyte activity within a gel co-culture, both in terms of maintaining the coherence of chondrocyte spheroids, leading to a larger quantity of CD44 (by immunofluorescence) and a higher production of collagen and glycosaminoglycans (by histology) compared with the mono-culture.

A novel construct with biomechanical flexibility for articular cartilage regeneration

BACKGROUND

Although tissue-engineered cartilage has been broadly studied, complete integration of regenerated cartilage with residual cartilage is still difficult for the inferior mechanical and biochemical feature of neocartilage. Chondrogenesis of mesenchymal stem cells can be induced by biophysical and biochemical factors.

METHODS

In this study, autologous platelet-rich fibrin (PRF) membrane was used as a growth factor-rich scaffold that may facilitate differentiation of the transplanted bone marrow mesenchymal stem cells (BMSCs). At the same time, hydrostatic pressure was adopted for pre-adjustment of the seed cells before transplantation that may promote the mechanical flexibility of neocartilage.

RESULTS

An in vitro study showed that the feasible hydrostatic pressure stimulation substantially promoted the chondrogenic potential of in vitro-cultured BMSC/PRF construct. In vivo results revealed that at every time point, the newborn tissues were the most favorable in the pressure-pretreated BMSC/PRF transplant group. Besides, the transplantation of feasible hydrostatic pressure-pretreated construct by BMSC sheet fragments and PRF granules could obviously improve the integration between the regenerated cartilage and host cartilage milieu, and thereby achieve boundaryless repair between the neocartilage and residual host cartilage tissue in rabbit temporomandibular joints. It could be concluded that feasible hydrostatic pressure may effectively promote the proliferation and chondrogenic differentiation of BMSCs in a BMSC/PRF construct.

CONCLUSION

This newly formed construct with biomechanical flexibility showed a superior capacity for cartilage regeneration by promoting the mechanical properties and integration of neocartilage.

Chitosan-based scaffold counteracts hypertrophic and fibrotic markers in chondrogenic differentiated mesenchymal stromal cells

Cartilage tissue engineering remains problematic because no systems are able to induce signals that contribute to native cartilage structure formation. Therefore, we tested the potentiality of gelatin-polyethylene glycol scaffolds containing three different concentrations of chitosan (CH; 0%, 8%, and 16%) on chondrogenic differentiation of human platelet lysate-expanded human bone marrow mesenchymal stromal cells (hBM-MSCs). Typical chondrogenic (SOX9, collagen type 2, and aggrecan), hypertrophic (collagen type 10), and fibrotic (collagen type 1) markers were evaluated at gene and protein level at Days 1, 28, and 48. We demonstrated that 16% CH scaffold had the highest percentage of relaxation with the fastest relaxation rate. In particular, 16% CH scaffold, combined with chondrogenic factor TGFβ3, was more efficient in inducing hBM-MSCs chondrogenic differentiation compared with 0% or 8% scaffolds. Collagen type 2, SOX9, and aggrecan showed the same expression in all scaffolds, whereas collagen types 10 and 1 markers were efficiently down-modulated only in 16% CH. We demonstrated that using human platelet lysate chronically during hBM-MSCs chondrogenic differentiation, the chondrogenic, hypertrophic, and fibrotic markers were significantly decreased. Our data demonstrate that only a high concentration of CH, combined with TGFβ3, creates an environment capable of guiding in vitro hBM-MSCs towards a phenotypically stable chondrogenesis.

Current Trends in Fabrication of Biomaterials for Bone and Cartilage Regeneration: Materials Modifications and Biophysical Stimulations

The aim of engineering of biomaterials is to fabricate implantable biocompatible scaffold that would accelerate regeneration of the tissue and ideally protect the wound against biodevice-related infections, which may cause prolonged inflammation and biomaterial failure. To obtain antimicrobial and highly biocompatible scaffolds promoting cell adhesion and growth, materials scientists are still searching for novel modifications of biomaterials. This review presents current trends in the field of engineering of biomaterials concerning application of various modifications and biophysical stimulation of scaffolds to obtain implants allowing for fast regeneration process of bone and cartilage as well as providing long-lasting antimicrobial protection at the site of injury. The article describes metal ion and plasma modifications of biomaterials as well as post-surgery external stimulations of implants with ultrasound and magnetic field, providing accelerated regeneration process. Finally, the review summarizes recent findings concerning the use of piezoelectric biomaterials in regenerative medicine.

A Novel Biodegradable and Thermosensitive Poly(Ester-Amide) Hydrogel for Cartilage Tissue Engineering

Thermosensitive hydrogels are attractive alternative scaffolding materials for minimally invasive surgery through a simple injection and in situ gelling. In this study, a novel poly(ester-amide) polymer, methoxy poly(ethylene glycol)-poly(pyrrolidone-co-lactide) (mPDLA, P3L7) diblock copolymer, was synthesized and characterized for cartilage tissue engineering. A series of amphiphilic diblock copolymers was synthesized by ring-opening polymerization of mPEG 550, D,L-lactide, and 2-pyrrolidone. By dynamic light scattering analysis and tube-flipped-upside-down method, viscoelastic properties of the mPDLA diblock copolymer solution exhibited sol-gel transition behavior as a function of temperature. An in vitro degradation assay showed that degradation acidity was effectively reduced by introducing the 2-pyrrolidone monomer into the polyester hydrogel. Besides, mPDLA exhibited great biocompatibility in vitro for cell encapsulation due to a high swelling ratio. Moreover, cell viability and biochemical analysis proved that the mPDLA hydrogel presented a great chondrogenic response. Taken together, these results demonstrate that mPDLA hydrogels are promising injectable scaffolds potentially applicable to cartilage tissue engineering.