Tough and elastic hydrogel of hyaluronic acid and chondroitin sulfate as potential cell scaffold materials

An enzymatically crosslinked collagen type II/hyaluronic acid hybrid hydrogel: A biomimetic cell delivery system for cartilage tissue engineering

This study presents new injectable hydrogels based on hyaluronic acid and collagen type II that mimic the polysaccharide-protein structure of natural cartilage. After collagen isolation from chicken sternal cartilage, tyramine-grafted hyaluronic acid and collagen type II (HA-Tyr and COL-II-Tyr) were synthesized. Hybrid hydrogels were prepared with different ratios of HA-Tyr/COL-II-Tyr using horseradish peroxidase and noncytotoxic concentrations of hydrogen peroxide to encapsulate human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). The findings showed that a higher HA-Tyr content resulted in a higher storage modulus and a lower hydrogel shrinkage, resulting in hydrogel swelling. Incorporating COL-II-Tyr into HA-Tyr hydrogels induced a more favorable microenvironment for hBM-MSCs chondrogenic differentiation. Compared to HA-Tyr alone, the hybrid HA-Tyr/COL-II-Tyr hydrogel promoted enhanced chondrocyte adhesion, spreading, proliferation, and upregulation of cartilage-related gene expression. These results highlight the promising potential of injectable HA-Tyr/COL-II-Tyr hybrid hydrogels to deliver cells for cartilage regeneration.

Modification of hyaluronic acid to enable click chemistry photo-crosslinking of hydrogels with tailorable degradation profiles

Hyaluronic acid (HA) is a naturally occurring mucopolysaccharide that, due to its inherent bioactivity and extracellular matrix-like structure, has the potential to be utilised extensively in tissue engineering. However, this glycosaminoglycan lacks the properties required for cellular adhesion and photo-crosslinking by UV light, which significantly hinders this polymers applicability. This research presents a method for modifying hyaluronic acid via thiolation and methacrylation to generate a novel photo-crosslinkable polymer with improved physicochemical properties, biocompatibility and the potential to customize biodegradability according to the ratio of monomers used. A decrease in stiffness proportional to increasing thiol concentration was observed when testing the compressive strength of hydrogels. Conversely, it was noted that the storage moduli of hydrogels increased proportionally to thiol concentration indicating a greater degree of cross-linking with the addition of thiol. The addition of thiol to HA increased the biocompatibility of the material in both neuronal and glial cell lines and improved the degradability of methacrylated HA. Due to the enhanced physicochemical properties and biocompatibility imparted by the introduction of thiolated HA, this novel hydrogel system could have numerous bioengineering applications.

Pushing the Natural Frontier: Progress on the Integration of Biomaterial Cues toward Combinatorial Biofabrication and Tissue Engineering

The engineering of fully functional, biological-like tissues requires biomaterials to direct cellular events to a near-native, 3D niche extent. Natural biomaterials are generally seen as a safe option for cell support, but their biocompatibility and biodegradability can be just as limited as their bioactive/biomimetic performance. Furthermore, integrating different biomaterial cues and their final impact on cellular behavior is a complex equation where the outcome might be very different from the sum of individual parts. This review critically analyses recent progress on biomaterial-induced cellular responses, from simple adhesion to more complex stem cell differentiation, looking at the ever-growing possibilities of natural materials modification. Starting with a discussion on native material formulation and the inclusion of cell-instructive cues, the roles of shape and mechanical stimuli, the susceptibility to cellular remodeling, and the often-overlooked impact of cellular density and cell-cell interactions within constructs, are delved into. Along the way, synergistic and antagonistic combinations reported in vitro and in vivo are singled out, identifying needs and current lessons on the development of natural biomaterial libraries to solve the cell-material puzzle efficiently. This review brings together knowledge from different fields envisioning next-generation, combinatorial biomaterial development toward complex tissue engineering.

A novel multifunctional Salecan/κ-carrageenan composite hydrogel with anti-freezing properties: Advanced rheology, thermal analysis and model fitting

The multifunctional hydrogels (HGs) have attracted intensive concern in biomedicine, food, and flexible devices. Nevertheless, chemically crosslinked synthetic HGs are commonly under specific restrictions because of their possible biotoxicity. This study focuses on the employment of physical approaches to prepare novel Salecan/κ-carrageenan composites HGs (CHGs) without changing their basic structures. Comprehensive rheological and thermal studies have been performed to investigate their distinctive properties. The data obtained from the tests and model fitting confirmed that the highest activation energy of CHGs was 172,142.2 J/mol, and the maximum equilibrium creep compliance was 0.0085 1/Pa. The sample recovery rate could reach 92.6%, while the anti-freezing temperature can be as low as -20 °C. It is the first report focusing on novel CHGs made from Salecan and κ-carrageenan with ideal anti-freezing ability, enhanced thermostability, good injectability, self-recovery, and other rheological properties that will provide effective support for various future applications.

Chemical Modification of Hyaluronan and Their Biomedical Applications

Hyaluronan, the extracellular matrix glycosaminoglycan, is an important structural component of many tissues playing a critical role in a variety of biological contexts. This makes hyaluronan, which can be biotechnologically produced in large scale, an attractive starting polymer for chemical modifications. This review provides a broad overview of different synthesis strategies used for modulating the biological as well as material properties of this polysaccharide. We discuss current advances and challenges of derivatization reactions targeting the primary and secondary hydroxyl groups or carboxylic acid groups and the N-acetyl groups after deamidation. In addition, we give examples for approaches using hyaluronan as biomedical polymer matrix and consequences of chemical modifications on the interaction of hyaluronan with cells via receptor-mediated signaling. Collectively, hyaluronan derivatives play a significant role in biomedical research and applications indicating the great promise for future innovative therapies.

Functional mechanical attributes of natural and synthetic gel-based scaffolds in tissue engineering: strain-stiffening effects on apparent elastic modulus and compressive toughness

The accurate identification and determination of elastic modulus and toughness, as well as other functional mechanical attributes of artificial tissues, are of paramount importance in several fields of tissue science, tissue engineering and technology, since biomechanical and biophysical behavior is strongly linked to biological features of the medical implants and tissue-engineering scaffolds. When soft or ultra-soft materials are investigated, a relevant dispersion of elastic modulus values can be achieved, due to the strain-stiffening effects, inducing a typical non-linear behavior of these materials, as a function of strain-range. In this short communication, the Apparent elastic modulus strain-range dependence is estimated from a segmentation of the strain stiffening curve, and the related compressive toughness is investigated and discussed, based on experimental evidence, for 6 different kinds of gels, used for artificial tissue fabrication; experimental results are compared to mechanical properties of native human tissues.

Development of novel biopolymer-based nanoparticles loaded cream for potential treatment of topical fungal infections

OBJECTIVE

Biodegradable polymers are extensively used due to their efficient safety profiles. The aim of the current study was to fabricate, evaluate, and characterize biodegradable, biocompatible fluconazole (FLZ) loaded chitosan (CHS) chondroitin sulfate (CS) nanoparticles (NPs) for topical delivery. Polymers utilized in the formulation not only served as a carrier system but also aided in fighting with complex etiology of the disease due to their innate antifungal activities.

METHODS

NPs were prepared by the complex coacervation method, then were optimized for various parameters and subsequently loaded into a cream.

RESULTS

Scanning electron microscopic (SEM) analysis showed spherical morphology of the NPs. Prepared NPs showed an average particle size in the range of 350-450 nm and an encapsulation efficiency (EE) of 86%. The polydispersity index (PDI) was found to be 0.148 that showed a uniform distribution of NPs. Fourier transform infrared (FTIR) spectroscopy confirmed the absence of any electrostatic interaction between ingredients. In vitro drug release analyses exhibited a sustained release of the drug and higher antifungal activity than free FLZ. Ex vivo permeability and drug distribution in different skin layers ensured a site-specific delivery of the FLZ-NPs. As compared with free FLZ and other control groups, the prepared NPs also exhibited significantly higher antifungal activity against Candida albicans (p < .01).

CONCLUSION

It was concluded from the results that the FLZ-NPs laden cream could be a potential candidate for topical and site-specific delivery of the drug cargo for the potential treatment of fungal infections.

A composite scaffold of Wharton's jelly and chondroitin sulphate loaded with human umbilical cord mesenchymal stem cells repairs articular cartilage defects in rat knee

To evaluate the performance of a composite scaffold of Wharton's jelly (WJ) and chondroitin sulfate (CS) and the effect of the composite scaffold loaded with human umbilical cord mesenchymal stem cells (hUCMSCs) in repairing articular cartilage defects, two experiments were carried out. The in vitro experiments involved identification of the hUCMSCs, construction of the biomimetic composite scaffolds by the physical and chemical crosslinking of WJ and CS, and testing of the biomechanical properties of both the composite scaffold and the WJ scaffold. In the in vivo experiments, composite scaffolds loaded with hUCMSCs and WJ scaffolds loaded with hUCMSCs were applied to repair articular cartilage defects in the rat knee. Moreover, their repair effects were evaluated by the unaided eye, histological observations, and the immunogenicity of scaffolds and hUCMSCs. We found that in vitro, the Young's modulus of the composite scaffold (WJ-CS) was higher than that of the WJ scaffold. In vivo, the composite scaffold loaded with hUCMSCs repaired rat cartilage defects better than did the WJ scaffold loaded with hUCMSCs. Both the scaffold and hUCMSCs showed low immunogenicity. These results demonstrate that the in vitro construction of a human-derived WJ-CS composite scaffold enhances the biomechanical properties of WJ and that the repair of knee cartilage defects in rats is better with the composite scaffold than with the single WJ scaffold if the scaffold is loaded with hUCMSCs.

Glycosaminoglycans in Tissue Engineering: A Review

Glycosaminoglycans are native components of the extracellular matrix that drive cell behavior and control the microenvironment surrounding cells, making them promising therapeutic targets for a myriad of diseases. Recent studies have shown that recapitulation of cell interactions with the extracellular matrix are key in tissue engineering, where the aim is to mimic and regenerate endogenous tissues. Because of this, incorporation of glycosaminoglycans to drive stem cell fate and promote cell proliferation in engineered tissues has gained increasing attention. This review summarizes the role glycosaminoglycans can play in tissue engineering and the recent advances in their use in these constructs. We also evaluate the general trend of research in this niche and provide insight into its future directions.

Activated hyaluronic acid/collagen composite hydrogel with tunable physical properties and improved biological properties

Self-crosslinkable and injectable hydrogels were fabricated with collagen type I (Col I) and N-hydroxy sulfosuccinimide activated hyaluronic acid (HA-sNHS) at physiological conditions without any initiators or crosslinkers. The physical properties of hydrogels, such as gelation time, swelling property, degradation property and mechanical property could be regulated by adjusting the substitution degree (DS) of HA-sNHS. Chondrocytes were encapsulated into hydrogels and their proliferation, phenotype maintenance and matrix secretion were characterized. The results demonstrated that chondrocytes in hydrogel Col I/HA-sNHS32% in which the DS of HA-sNHS was 32% secreted more cartilage specific matrix than others. The results of animal experiment demonstrated that hydrogels Col I and Col I/HA-sNHS32% both had good biodegradability and cytocompatibility. This study provided a novel and simple method for fabrication of self-crosslinkable and injectable hydrogels with tunable physical properties. It implied that these hydrogels could find some applications in the fields of cell encapsulation and tissue engineering.

Hyaluronic acid containing scaffolds ameliorate stem cell function for tissue repair and regeneration

Recent evidence based studies have proposed hyaluronic acid (HA) as an emerging biopolymer for various tissue engineering application. Meanwhile, stem cells (SCs) have also gained immense popularity for their tissue regenerative capacity. Thus, combining HA and stem cells for tissue engineering application have shown to foster tissue repair and regeneration process. HA possesses the ability to interact with SCs via cellular surface receptors along with the capacity to elicit the process of differentiation. The influence of HA on stem cells has been widely investigated in cartilage and bone repair but their properties of reducing inflammation has also been explored in various other tissue repair processes. In this review, we have provided an insight to the effect of crosslinked and non-crosslinked HA on various stem cells. Further, HA based scaffolds combined with stem cells have shown to have a synergistic effect in the regeneration capacity. Also, various chemically modified HA and biomolecules conjugated HA as a suitable carrier or matrix for stem cells delivery and the effect of HA in fine tuning the stem cells function is discussed.

Highly elastic, electroconductive, immunomodulatory graphene crosslinked collagen cryogel for spinal cord regeneration

Novel amino-functionalized graphene crosslinked collagen based nerve conduit having appropriate electric (3.8 ± 0.2 mSiemens/cm) and mechanical cues (having young modulus value of 100-347 kPa) for stem cell transplantation and neural tissue regeneration was fabricated using cryogelation. The developed conduit has shown sufficiently high porosity with interconnectivity between the pores. Raman spectroscopy analysis revealed the increase in orderliness and crosslinking of collagen molecules in the developed cryogel due to the incorporation of amino-functionalized graphene. BM-MSCs grown on graphene collagen cryogels have shown enhanced expression of CD90 and CD73 gene upon electric stimulation (100 mV/mm) contributing towards maintaining their stemness. Furthermore, an increased secretion of ATP from BM-MSCs grown on graphene collagen cryogel was also observed upon electric stimulation that may help in regeneration of neurons and immuno-modulation. Neuronal differentiation of BM-MSCs on graphene collagen cryogel in the presence of electric stimulus showed an enhanced expression of MAP-2 kinase and β-tubulin III. Immunohistochemistry studies have also demonstrated the improved neuronal differentiation of BM-MSCs. BM-MSCs grown on electro-conductive collagen cryogels under inflammatory microenvironment in vitro showed high indoleamine 2,3 dioxygenase activity. Moreover, macrophages cells grown on graphene collagen cryogels have shown high CD206 (M2 polarization marker) and CD163 (M2 polarization marker) and low CD86 (M1 polarization marker) gene expression demonstrating M2 polarization of macrophages, which may aid in tissue repair. In an organotypic culture, the developed cryogel conduit has supported cellular growth and migration from adult rat spinal cord. Thus, this novel electro-conductive graphene collagen cryogels have potential for suppressing the neuro-inflammation and promoting the neuronal cellular migration and proliferation, which is a major barrier during the spinal cord regeneration.

Interpenetrating polymer networks of collagen, hyaluronic acid, and chondroitin sulfate as scaffolds for brain tissue engineering

Stem cells can provide neuro-protection and potentially neuro-replacement to patients suffering from traumatic brain injuries (TBI), with a practical option being delivery via engineered scaffolds. Collagen (Coll) and glycosaminoglycan (GAG) have been used as scaffolds for brain tissue engineering yet they often do not support cell differentiation and survival. In this study, we developed interpenetrating polymer network scaffolds comprising Coll, and incorporating two commonly found GAGs in the brain, chondroitin sulfate (CS) and/or hyaluronic acid (HA). We seeded these scaffolds with mouse neural stem cells from the subventricular zone (SVZ) niche. Compared to Coll-alone, all other substrates decreased the percent of nestin+ stem cells. Coll-CS-HA was more efficient at suppressing nestin expression than the other scaffolds; all SVZ cells lost nestin expression within 7 days of culture. In contrast to nestin, the percentage of microtubule associated protein 2 (MAP2+) neurons was greater in scaffolds containing, CS, HA or CS-HA, compared to Coll alone. Finally, Coll-CS increased the percentage of glial fibrillary acidic protein (GFAP+) astrocytes compared to Coll scaffolds. Overall, this work shows that Coll-HA and Coll-CS-HA scaffolds selectively enhance neurogenesis and may be advantageous in tissue engineering therapy for TBI. STATEMENT OF SIGNIFICANCE: Brain injury is devastating yet with few options for repair. Stem cells that reside in the subventricular zone (SVZ) only repair damage inefficiently due to poor control of their cellular progeny and unsuitable extracellular matrix substrates. To solve these problems, we have systematically generated collagen (Coll) scaffolds with interpenetrating polymer networks (IPN) of hyaluronic acid (HA) or chondroitin sulfate proteoglycans (CS) or both. The scaffolds had defined pore sizes, similar mechanical properties and all three stimulated neurogenesis, whereas only CS stimulated astrocyte genesis. Overall, this work suggests that Coll-HA and Coll-CS-HA scaffolds selectively enhance neurogenesis and may be advantageous in tissue engineering therapy for brain repair.

Multifunctional Nano and Collagen-Based Therapeutic Materials for Skin Repair

A novel strategy is needed for treating nonhealing wounds, which is able to simultaneously eradicate pathogenic bacteria and promote tissue regeneration. This would improve patient outcome and reduce the number of lower limb amputations. In this work, we present a multifunctional therapeutic approach able to control bacterial infections, provide a protective barrier to a full-thickness wound, and improve wound healing in a clinically relevant animal model. Our approach uses a nanoengineered antimicrobial nanoparticle for creating a sprayable layer onto the wound bed that prevents bacterial proliferation and also eradicates preformed biofilms. As a protective barrier for the wound, we developed a thermoresponsive collagen-based matrix that has prohealing properties and is able to fill wounds independent of their geometries. Our results indicate that using a combination of the matrix with full-thickness microscopic skin tissue columns synergistically contributed to faster and superior skin regeneration in a nonhealing wound model in diabetic mice.

Chondroitin: a natural biomarker with immense biomedical applications

Naturally extracted glycosaminoglycan chondroitin sulphate is the reactive product of N-acetylgalactosamine and d-glucuronic acid. Chondroitin sulfate (CS) extracted from Scophthalmus maximus, H. scabra, E. fraudatrix, M. magnum, and H. mexicana has shown remarkable anticoagulant, articular cartilage repair, corneal lesion healing, antidiabetic, and antiproliferative effects. Also, platinum and strontium nanoparticles of chondroitin sulfate are effective in osteoarthritis and exert anti-HSV2 and anti-angiogenic properties. A combination of chondroitin sulfate and RNA lipolexes demonstrates gene silencing effects in liver fibrosis. Chondroitin sulfate has also been used as a carrier for loxoprofen hydrogel preparation. Oligosaccharides of chondroitin sulfate showed effective inhibition of bovine testicular hyaluronidase enzyme as an antibacterial agent during pregnancy. Monoclonal antibody-recognized chondroitin sulfate A was effectively used to treat ameloblastoma. Selenium-chondroitin sulfate nanoparticles demonstrated positive effects in therapy of Kashin-Beck disease (KBD) and osteoarthritis.

Hyaluronan-Based Grafting Strategies for Liver Stem Cell Therapy and Tracking Methods

Cell adhesion is essential for survival, it plays important roles in physiological cell functions, and it is an innovative target in regenerative medicine. Among the molecular interactions and the pathways triggered during cell adhesion, the binding of cluster of differentiation 44 (CD44), a cell-surface glycoprotein involved in cell-cell interactions, to hyaluronic acid (HA), a major component of the extracellular matrix, is a crucial step. Cell therapy has emerged as a promising treatment for advanced liver diseases; however, so far, it has led to low cell engraftment and limited cell repopulation of the target tissue. Currently, different strategies are under investigation to improve cell grafting in the liver, including the use of organic and inorganic biomatrices that mimic the microenvironment of the extracellular matrix. Hyaluronans, major components of stem cell niches, are attractive candidates for coating stem cells since they improve viability, proliferation, and engraftment in damaged livers. In this review, we will discuss the new strategies that have been adopted to improve cell grafting and track cells after transplantation.

Tissue Engineering Strategies for Intervertebral Disc Treatment Using Functional Polymers

Intervertebral disc (IVD) is the fibrocartilage between the vertebrae, allowing the spine to move steadily by bearing multidirectional complex loads. Aging or injury usually causes degeneration of IVD, which is one of the main reasons for low back pain prevalent worldwide and reduced quality of life. While various treatment strategies for degenerative IVD have been studied using in vitro studies, animal experiments, and clinical trials, there are unsolved limitations for endogenous regeneration of degenerative IVD. In this respect, several tissue engineering strategies that are based on the cell and scaffolds have been extensively researched with positive outcomes for regeneration of IVD tissues. Scaffolds made of functional polymers and their diverse forms mimicking the macro- and micro-structure of native IVD enhance the biological and mechanical properties of the scaffolds for IVD regeneration. In this review, we discuss diverse morphological and functional polymers and tissue engineering strategies for endogenous regeneration of degenerative IVD. Tissue engineering strategies using functional polymers are promising therapeutics for fundamental and endogenous regeneration of degenerative IVD.

Carbohydrate-based nanomaterials for biomedical applications

Carbohydrates are abundant biomolecules, with a strong tendency to form supramolecular networks. A host of carbohydrate-based nanomaterials have been exploited for biomedical applications. These structures are based on simple mono- or disaccharides, as well as on complex, polymeric systems. Chemical modifications serve to tune the shapes and properties of these materials. In particular, carbohydrate-based nanoparticles and nanogels were used for drug delivery, imaging, and tissue engineering applications. Due to the reversible nature of the assembly, often based on a combination of hydrogen bonding and hydrophobic interactions, carbohydrate-based materials are valuable substrates for the creations of responsive systems. Herein, we review the current research on carbohydrate-based nanomaterials, with a particular focus on carbohydrate assembly. We will discuss how these systems are formed and how their properties are tuned. Particular emphasis will be placed on the use of carbohydrates for biomedical applications. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Chondroitin Sulfate-Degrading Enzymes as Tools for the Development of New Pharmaceuticals

Chondroitin sulfates are linear anionic sulfated polysaccharides found in biological tissues, mainly within the extracellular matrix, which are degraded and altered by specific lyases depending on specific time points. These polysaccharides have recently acquired relevance in the pharmaceutical industry due to their interesting therapeutic applications. As a consequence, chondroitin sulfate (CS) lyases have been widely investigated as tools for the development of new pharmaceuticals based on these polysaccharides. This review focuses on the major breakthrough represented by chondroitin sulfate-degrading enzymes and their structures and mechanisms of function in addition to their major applications.

Injectable hydrogels from enzyme-catalyzed crosslinking as BMSCs-laden scaffold for bone repair and regeneration

Bone-marrow-derived mesenchymal stem cells possess great potential for tissue engineering and regenerative medicine. In the work, an injectable BMSCs-laden hydrogel system was formed by enzyme-catalyzed crosslinking of hyaluronic acid-tyramine and chondroitin sulfate-tyramine in the presence of hydrogen peroxide and horseradish peroxidase, which was used as a 3D scaffold to explore the behavior of the mesenchymal stem cells. Afterward, the gelation rate, mechanical properties, as well as the degradation process of the scaffold were well characterized and optimized. Furthermore, bone morphogenetic protein-2 was encapsulated in the scaffold, which was used to improve the osteogenic properties. The results illustrated that such a BMSCs-laden hydrogel not only offered a proper microenvironment for the adhesion, proliferation and differentiation of mesenchymal stem cells in vitro, but also promoted bone regeneration in vivo. Therefore, this injectable BMSCs-laden hydrogel may serve as an efficient 3D scaffold for bone repair and regeneration.

Thermoplastic PCL-b-PEG-b-PCL and HDI Polyurethanes for Extrusion-Based 3D-Printing of Tough Hydrogels

Novel tough hydrogel materials are required for 3D-printing applications. Here, a series of thermoplastic polyurethanes (TPUs) based on poly(ɛ-caprolactone)-b-poly(ethylene glycol)-b-poly(ɛ-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymers and hexamethylene diisocyanate (HDI) were developed with PEG contents varying between 30 and 70 mol%. These showed excellent mechanical properties not only when dry, but also when hydrated: TPUs prepared from PCL-b-PEG-b-PCL with PEG of Mn 6 kg/mol (PCL₇-PEG₆-PCL₇) took up 122 wt.% upon hydration and had an E-modulus of 52 ± 10 MPa, a tensile strength of 17 ± 2 MPa, and a strain at break of 1553 ± 155% in the hydrated state. They had a fracture energy of 17976 ± 3011 N/mm² and a high tearing energy of 72 kJ/m². TPUs prepared using PEG with Mn of 10 kg/mol (PCL₅-PEG10-PCL₅) took up 534% water and were more flexible. When wet, they had an E-modulus of 7 ± 2 MPa, a tensile strength of 4 ± 1 MPa, and a strain at break of 147 ± 41%. These hydrogels had a fracture energy of 513 ± 267 N/mm² and a tearing energy of 16 kJ/m². The latter TPU was first extruded into filaments and then processed into designed porous hydrogel structures by 3D-printing. These hydrogels can be used in 3D printing of tissue engineering scaffolds with high fracture toughness.

Injectable decellularized nucleus pulposus-based cell delivery system for differentiation of adipose-derived stem cells and nucleus pulposus regeneration

Stem cell-based tissue engineering is a promising treatment for intervertebral disc (IVD) degeneration. A bio-scaffold that can maintain the function of transplanted cells and possesses favorable mechanical properties is needed in tissue engineering. Decellularized nucleus pulposus (dNP) has the potential to be a suitable bio-scaffold because it mimics the native nucleus pulposus (NP) composition. However, matrix loss during decellularization and difficulty in transplantation limit the clinical application of dNP scaffolds. In this study, we fabricated an injectable dNP-based cell delivery system (NPCS) and evaluated its properties by assessing the microstructure, biochemical composition, water content, biosafety, biostability, and mechanical properties. We also investigated the stimulatory effects of the bio-scaffold on the NP-like differentiation of adipose-derived stem cells (ADSCs) in vitro and the regenerative effects of the NPCS on degenerated NP in an in vivo animal model. The results showed that approximately 68% and 43% of the collagen and sGAG, respectively, remained in the NPCS after 30 days. The NPCS also showed mechanical properties similar to those of fresh NP. In addition, the NPCS was biocompatible and able to induce NP-like differentiation and extracellular matrix (ECM) synthesis in ADSCs. The disc height index (almost 81%) and the MRI index (349.05 ± 38.48) of the NPCS-treated NP were significantly higher than those of the degenerated NP after 16 weeks. The NPCS also partly restored the ECM content and the structure of degenerated NP in vivo. Our NPCS has good biological and mechanical properties and has the ability to promote the regeneration of degenerated NP. STATEMENT OF SIGNIFICANCE: Nucleus pulposus (NP) degeneration is usually the origin of intervertebral disc degeneration. Stem cell-based tissue engineering is a promising treatment for NP regeneration. Bio-scaffolds which have favorable biological and mechanical properties are needed in tissue engineering. Decellularized NP (dNP) scaffold is a potential choice for tissue engineering, but the difficulty in balancing complete decellularization and retaining ECM limits its usage. Instead of choosing different decellularization protocols, we complementing the sGAG lost during decellularization by cross-linking via genipin and fabricating an injectable dNP-based cell delivery system (NPCS) which has similar components as the native NP. We also investigated the biological and mechanical properties of the NPCS in vitro and verified its regenerative effects on degenerated IVDs in an animal model.

Fabrication and characterization of collagen-based injectable and self-crosslinkable hydrogels for cell encapsulation

Injectable and self-crosslinkable hydrogels have drawn much attention for their potential application as cell delivery carriers to deliver cells to the injury site of arbitrary shape. In this study, injectable and self-crosslinkable hydrogels were designed and fabricated based on collagen type I (Col I) and activated chondroitin sulfate (CS-sNHS) by physical and chemical crosslinking without the addition of any catalysts. The physical properties of hydrogels, including mechanical properties, swelling and degradation properties, were investigated. The results demonstrated that the physical properties of hydrogels, especially the stiffness of hydrogels, were readily tuned by varying the degree of substitution (DS) of CS-sNHS without changing the concentration of collagen-based precursor. Chondrocytes were encapsulated into hydrogels to investigate the effects of hydrogels on the survival, proliferation and extracellular matrix (ECM) secretion of cells by FDA/PI staining, CCK-8 test and histological staining. The results suggested that all of these hydrogels supported the survival and ECM secretion of chondrocytes, while there was more ECM secretion around chondrocytes encapsulated in hydrogel Col I/CS-sNHS56% in which the DS of CS-sNHS was 56%. When the neutral precursor solution for hydrogel of Col I or Col I/CS-sNHS56% was subcutaneously injected into SD rats, hydrogels both displayed acceptable biocompatibility in vivo. These results imply that these injectable and self-crosslinkable hydrogels are suitable candidates for applications in the fields of cell delivery and tissue engineering.

Biodiversity of CS–proteoglycan sulphation motifs: chemical messenger recognition modules with roles in information transfer, control of cellular behaviour and tissue morphogenesis

Chondroitin sulphate (CS) glycosaminoglycan chains on cell and extracellular matrix proteoglycans (PGs) can no longer be regarded as merely hydrodynamic space fillers. Overwhelming evidence over recent years indicates that sulphation motif sequences within the CS chain structure are a source of significant biological information to cells and their surrounding environment. CS sulphation motifs have been shown to interact with a wide variety of bioactive molecules, e.g. cytokines, growth factors, chemokines, morphogenetic proteins, enzymes and enzyme inhibitors, as well as structural components within the extracellular milieu. They are therefore capable of modulating a panoply of signalling pathways, thus controlling diverse cellular behaviours including proliferation, differentiation, migration and matrix synthesis. Consequently, through these motifs, CS PGs play significant roles in the maintenance of tissue homeostasis, morphogenesis, development, growth and disease. Here, we review (i) the biodiversity of CS PGs and their sulphation motif sequences and (ii) the current understanding of the signalling roles they play in regulating cellular behaviour during tissue development, growth, disease and repair.

Harnessing chondroitin sulphate in composite scaffolds to direct progenitor and stem cell function for tissue repair

This review details the inclusion of chondroitin sulphate in bioscaffolds for superior functional properties in tissue regenerative applications.

Hydrogels for Cartilage Regeneration, from Polysaccharides to Hybrids

The aims of this paper are: (1) to review the current state of the art in the field of cartilage substitution and regeneration; (2) to examine the patented biomaterials being used in preclinical and clinical stages; (3) to explore the potential of polymeric hydrogels for these applications and the reasons that hinder their clinical success. The studies about hydrogels used as potential biomaterials selected for this review are divided into the two major trends in tissue engineering: (1) the use of cell-free biomaterials; and (2) the use of cell seeded biomaterials. Preparation techniques and resulting hydrogel properties are also reviewed. More recent proposals, based on the combination of different polymers and the hybridization process to improve the properties of these materials, are also reviewed. The combination of elements such as scaffolds (cellular solids), matrices (hydrogel-based), growth factors and mechanical stimuli is needed to optimize properties of the required materials in order to facilitate tissue formation, cartilage regeneration and final clinical application. Polymer combinations and hybrids are the most promising materials for this application. Hybrid scaffolds may maximize cell growth and local tissue integration by forming cartilage-like tissue with biomimetic features.

Chondroitin sulfate from Scophthalmus maximus for treating osteoarthritis

Osteoarthritis (OA) is a common joint disease characterized by cartilage degradation. Chondroitin sulfate from shark (CS-S) has a good effect on OA in clinical, but due to source limited of CS from shark. Therefore, it is important to find a novel CS source with similar efficacy to CS-S in the treatment of OA. Herein, we reported a therapeutic effect of CS from scophthalmus maximus (CS-SM) for treating OA in rats. The OA model was established. After intervention with CS-SM by intragastric administration. Our results showed that CS-SM could protect articular cartilage in OA, inhibit the degradation of cartilage, decrease the apoptosis of chondrocytes, decline the content of interleukin-1, tumor necrosis factor-α and Prostaglandins E₂ in synovial fluid, down-regulate the protein expression of matrix metalloproteinase-1 and up-regulate the protein expression of tissue inhibitor of metalloproteinase-1. Our results suggest that oral CS from SM is a new potential therapy for OA.

Decoration of Chondroitin Polysaccharide with Threonine: Synthesis, Conformational Study, and Ice-Recrystallization Inhibition Activity

Several threonine (Thr)- and alanine (Ala)-rich antifreeze glycoproteins (AFGPs) and polysaccharides act in nature as ice recrystallization inhibitors. Among them, the Thr-decorated capsular polysaccharide (CPS) from the cold-adapted Colwellia psychrerythraea 34H bacterium was recently investigated for its cryoprotectant activity. A semisynthetic mimic thereof was here prepared from microbial sourced chondroitin through a four-step strategy, involving a partial protection of the chondroitin polysaccharide as a key step for gaining an unprecedented quantitative amidation of its glucuronic acid units. In-depth NMR and computational analysis suggested a fairly linear conformation for the semisynthetic polysaccharide, for which the antifreeze activity by a quantitative ice recrystallization inhibition assay was measured. We compared the structure-activity relationships for the Thr-derivatized chondroitin and the natural Thr-decorated CPS from C. psychrerythraea.

Glycosaminoglycans from marine sources as therapeutic agents

Glycosaminoglycans (GAGs) in marine animals are different to those of terrestrial organisms, mainly in terms of molecular weight and sulfation. The therapeutic properties of GAGs are related to their ability to interact with proteins, which is very much influenced by sulfation position and patterns. Since currently GAGs cannot be chemically synthesized, they are sourced from natural products, with high intra- but also inter-species variability, in terms of chain length, disaccharide composition and sulfation pattern. Consequently, sulfated GAGs are the most interesting molecules in the marine environment and constitute the focus of the present review. In particular, chondroitin sulfate (CS) appears as the most promising compound. CS-E chains [GlcA-GalNAc(4S,6S)] extracted from squid possess antiviral and anti-metastatic activities and seem to impart signalling properties and improve the mechanical performance of cartilage engineering constructs; Squid CS-E and octopus CS-K [GlcA(3S)-GalNAc(4S)], dermatan sulfate (DS) from sea squirts [-iK units, IdoA(3S)-GalNAc(4S)] and sea urchins [-iE units, IdoA-GalNAc(4S,6S)] and hybrids CS/DS from sharks (-B/iB [GlcA/IdoA(2S)-GalNAc(4S)], -D/iD [GlcA/IdoA(2S)-GalNAc(6S)] and -E/iE units [GlcA/IdoA-GalNAc(4S,6S)]) promote neurite outgrowth and could be valuable materials for nerve regeneration. Also displaying antiviral and anti-metastatic properties, a rare CS with fucosylated branches isolated from sea cucumbers is an anticoagulant and anti-inflammatory agent. In this same line, marine heparin extracted from shrimp and sea squirt has proven anti-inflammatory properties, with the added advantage of decreased risk of bleeding because of its low anticoagulant activity.

Cholangiocytes: Cell transplantation

BACKGROUND

Due to significant limitations to the access to orthotropic liver transplantation, cell therapies for liver diseases have gained large interest worldwide.

SCOPE OF REVIEW

To revise current literature dealing with cell therapy for liver diseases. We discussed the advantages and pitfalls of the different cell sources tested so far in clinical trials and the rationale underlying the potential benefits of transplantation of human biliary tree stem cells (hBTSCs).

MAJOR CONCLUSIONS

Transplantation of adult hepatocytes showed transient benefits but requires immune-suppression that is a major pitfall in patients with advanced liver diseases. Mesenchymal stem cells and hematopoietic stem cells transplanted into patients with liver diseases are not able to replace resident hepatocytes but rather they target autoimmune or inflammatory processes into the liver. Stem cells isolated from fetal or adult liver have been recently proposed as alternative cell sources for advanced liver cirrhosis and metabolic liver disease. We demonstrated the presence of multipotent cells expressing a variety of endodermal stem cell markers in (peri)-biliary glands of bile ducts in fetal or adult human tissues, and in crypts of gallbladder epithelium. In the first cirrhotic patients treated in our center with biliary tree stem cell therapy, we registered no adverse event but significant benefits.

GENERAL SIGNIFICANCE

The biliary tree stem cell could represent the ideal cell source for the cell therapy of liver diseases. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Hyaluronan coating improves liver engraftment of transplanted human biliary tree stem/progenitor cells

BACKGROUND

Cell therapy of liver diseases with human biliary tree stem cells (hBTSCs) is biased by low engraftment efficiency. Coating the hBTSCs with hyaluronans (HAs), the primary constituents of all stem cell niches, could facilitate cell survival, proliferation, and, specifically, liver engraftment given that HAs are cleared selectively by the liver.

METHODS

We developed a fast and easy method to coat hBTSCs with HA and assessed the effects of HA-coating on cell properties in vitro and in vivo.

RESULTS

The HA coating markedly improved the viability, colony formation, and population doubling of hBTSCs in primary cultures, and resulted in a higher expression of integrins that mediate cell attachment to matrix components. When HA-coated hBTSCs were transplanted via the spleen into the liver of immunocompromised mice, the engraftment efficiency increased to 11% with respect to 3% of uncoated cells. Notably, HA-coated hBTSC transplantation in mice resulted in a 10-fold increase of human albumin gene expression in the liver and in a 2-fold increase of human albumin serum levels with respect to uncoated cells. Studies in distant organs showed minimal ectopic cell distribution without differences between HA-coated and uncoated hBTSCs and, specifically, cell seeding in the kidney was excluded.

CONCLUSIONS

A ready and economical procedure of HA cell coating greatly enhanced the liver engraftment of transplanted hBTSCs and improved their differentiation toward mature hepatocytes. HA coating could improve outcomes of stem cell therapies of liver diseases and could be immediately translated into the clinic given that GMP-grade HAs are already available for clinical use.

Generation of Large-Scale DNA Hydrogels with Excellent Blood and Cell Compatibility

Hemocompatibility and cytocompatibility of biomaterials codetermine the success of tissue engineering applications. DNA, the natural component of our cells, is an auspicious biomaterial for the generation of designable scaffolds with tailorable characteristics. In this study, a combination of rolling circle amplification and multiprimed chain amplification is used to generate hydrogels at centimeter scale consisting solely of DNA. Using an in vitro rotation model and fresh human blood, the reaction of the hemostatic system on DNA hydrogels is analyzed. The measurements of hemolysis, platelets activation, and the activation of the complement, coagulation, and neutrophils using enzyme-linked immunosorbent assays demonstrate excellent hemocompatibility. In addition, the cytocompatibility of the DNA hydrogels is tested by indirect contact (agar diffusion tests) and material extract experiments with L929 murine fibroblasts according to the ISO 10993-5 specifications and no negative impact on the cell viability is detected. These results indicate the promising potential of DNA hydrogels as biomaterials for versatile applications in the field of regenerative medicine.

A novel multistep method for chondroitin sulphate immobilization and its interaction with fibroblast cells

Polymeric biomaterials are widely used in medical applications owing to their low cost, processability and sufficient toughness. Surface modification by creating a thin film of bioactive agents is promising technique to enhance cellular interactions, regulate the protein adsorption and/or avoid bacterial infections. Polyethylene is one of the most used polymeric biomaterial but its hydrophobic nature impedes its further chemical modifications. Plasma treatment is unique method to increase its hydrophilicity by incorporating hydrophilic oxidative functional groups and tailoring the surface by physical etching. Furthermore, grafting of polymer brushes of amine group containing monomers onto the functionalized surface lead to strongly immobilized bioactive agents at the final step. Chondroitin sulphate is natural polysaccharide mainly found in connective cartilage tissue which used as a bioactive agent to immobilize onto polyethylene surface by multistep method in this study.

Physico-chemical characterization and cytotoxicity evaluation of curcumin loaded in chitosan/chondroitin sulfate nanoparticles

In this study, chitosan (CTS)/chondroitin sulfate (CS) nanoparticles, both pure and curcumin-loaded, were synthesized by ionic gelation. This method is simple and efficient for obtaining nanoparticles with a low polydispersity index (0.151±0.03 to 0.563±0.07) and hydrodynamic diameter in the range of 175.7±2.5 to 710.2±8.9nm, for this study. Samples have a relatively high zeta potential value, a fact that indicates that the colloidal system has good physical and chemical stabilities. The efficiency of the curcumin encapsulation in nanoparticles, which ranged from 62.4±0.61% to 68.3±0.88%, depends on the pH of the chitosan solution. The release of curcumin from the nanoparticles was enabled by a diffusion mechanism, with fast release in a phosphate buffer solution at pH6.8. The assaying of cell viability by the MTT test showed that the presence of both free curcumin and curcumin in the nanoencapsulated form leads to a statistically significant reduction in the viability of A549 cells, by comparison with the control group. The most significant reductions in cell viability of 41.1% and 60.4% (p<0.0001) were observed after 72h, by using 40μmol∙L(-1) free curcumin and curcumin encapsulated in CTS/CS nanoparticles with the chitosan solution at pH6.0, respectively.