A combinatorial approach towards the design of nanofibrous scaffolds for chondrogenesis

Electrospun microfiber composite scaffolds of polyvinyl alcohol, polyhydroxybutyrate, and multiwalled carbon nanotubes for enhancing the osteogenic differentiation of stem cells to promote bone regeneration

Micro/nanofibers fabricated through hybrid co-electrospinning of synthetic polymers and carbon nanomaterials offer significant potential for bone tissue engineering. Addressing the challenges of poor biocompatibility and insufficient mechanical strength inherent in single-polymer systems, this study pioneers the application of dual-nozzle hybrid electrospinning, enabling the simultaneous processing of materials from distinct solvent systems. Poly (3-hydroxybutyric acid-co-4-hydroxybutyric acid) (P34HB) and polyvinyl alcohol (PVA) were employed as matrix materials, with multi-walled carbon nanotubes (MWCNTs) incorporated at varying mass fractions to enhance material performance. This approach capitalized on the complementary advantages of different components, improving fiber spinnability under diverse solvent conditions while optimizing the physicochemical properties of the resultant scaffolds. Comprehensive characterization was conducted to assess scaffold morphology, hydrophilicity, degradability, mechanical performance, and bioactivity. Biocompatibility and osteogenic potential were evaluated through in vitro studies using human bone marrow mesenchymal stem cells (HBMSCs), while in vivo bone integration and screw stability were analyzed in a rabbit femur model. Findings revealed that MWCNT-modified scaffolds exhibited enhanced fiber morphology, enhanced elasticity, improved tensile strength, superior biocompatibility, and increased osteoinductive activity. Notably, PVA-P34HB-1 %MWCNTs scaffolds demonstrated significant clinical potential in bone tissue engineering by reinforcing screw stability through induced osteogenesis.

Mechanical and Physical Characterization of a Biphasic 3D Printed Silk-Infilled Scaffold for Osteochondral Tissue Engineering

Osteochondral tissue damage is a serious concern, with even minor cartilage damage dramatically increasing an individual's risk of osteoarthritis. Therefore, there is a need for an early intervention for osteochondral tissue regeneration. 3D printing is an exciting method for developing novel scaffolds, especially for creating biological scaffolds for osteochondral tissue engineering. However, many 3D printing techniques rely on creating a lattice structure, which often demonstrates poor cell bridging between filaments due to its large pore size, reducing regenerative speed and capacity. To tackle this issue, a novel biphasic scaffold was developed by a combination of 3D printed poly(ethylene glycol)-terephthalate-poly(butylene-terephthalate) (PEGT/PBT) lattice infilled with a porous silk scaffold (derived from Bombyx mori silk fibroin) to make up a bone phase, which continued to a seamless silk top layer, representing a cartilage phase. Compression testing showed scaffolds had Young's modulus, ultimate compressive strength, and fatigue resistance that would allow for their theoretical survival during implantation and joint articulation without stress-shielding mechanosensitive cells. Fluorescent microscopy showed biphasic scaffolds could support the attachment and spreading of human mesenchymal stem cells from bone marrow (hMSC-BM). These promising results highlight the potential utilization of this novel scaffold for osteochondral tissue regeneration as well as highlighting the potential of infilling silk materials within 3D printed scaffolds to further increase their versatility.

Design of multiple-function matrix encapsulated with Marjoram extract to support cellular functions, stimulate collagen synthesis and decrease infection in wound

This study aimed to assess the role of the combination of design techniques of the engineered substrates, and the effect of encapsulating Marjoram (Origanum Majorana L.) into the matrix network was studied. To this end, PVA-PEG matrices were designed through 3 techniques of freeze-thaw (FT), the combination of both methods of freeze-drying and freeze-thawing(FT-FD), and ternary technique(freeze-drying,freeze-thawing,cross-linking(FT-FD/CL)), by combining equal volume ratios of both polymers. The results indicated the ternary technique can provide better physicochemical properties(porosity: 96%, lower degradation rate, higher modulus) compared to FT and FT-FD methods. Afterward, encapsulation of Marjoram-extracted bio-actives in the matrix network designed with the ternary technique demonstrated that the increase in the extract concentration up to 3% can increase encapsulation efficiency. The encapsulation also caused a more cohesive network by better bonding between functional groups in herbal biomolecules and polymer chains of the matrix. Mass transport mechanisms and release kinetics of matrix-encapsulated bio-actives indicated a deviation from Fickian diffusion and the release by diffusion and swelling process. Biologically, matrix-loaded herbal carbohydrate(Epi-alpha-Cadinol) improved fibroblast adhesion and distribution on the substrate surface, and led to the better synthesis of collagen fibers, especially in 3% herbal extract, and antibacterial activities owing to the controlled release of sesquiterpenoids and N-Acetyl-L-proline.

Photo-crosslinked chitosan-gelatin xerogel-like coating onto "cold" plasma functionalized poly(lactic acid) film as cell culture support

This paper reports on biofunctionalisation of a poly(lactic acid) (PLA) film by surface activation through cold plasma treatment followed by coating with a chitosan-gelatin xerogel. The UV cross-linking of the xerogel precursor was simultaneously performed with the fixation onto the PLA support. This has a strong effect on surface properties, in terms of wettability, surface free energy, morphology and micromechanical features. The hydrophilic - hydrophobic character of the surface, determined by contact angle measurements, was tuned along the process, passing from moderate hydrophobic PLA to enhanced hydrophilic plasma activated surface, which favors coating adhesion, then to moderate hydrophobic chitosan-gelatin coating. The coating has a Lewis amphoteric surface, with a porous xerogel-like morphology, as revealed by scanning electron microscopy images. By riboflavin mediated UV cross-linking the chitosan-gelatin coating becomes high adhesive and with a more pronounced plasticity, as shown by AFM force-distance spectroscopy. Thus prepared surface-coated PLA supports were successfully tested for growth of dermal fibroblasts, which are known for their induction potential of chondrogenic cells, which is very important in cartilage tissue engineering.

Photo-/thermo-responsive bioink for improved printability in extrusion-based bioprinting

Extrusion-based bioprinting has demonstrated significant potential for manufacturing constructs, particularly for 3D cell culture. However, there is a greatly limited number of bioink candidates exploited with extrusion-based bioprinting, as they meet the opposing requirements for printability with indispensable rheological features and for biochemical functionality with desirable microenvironment. In this study, a blend of silk fibroin (SF) and iota-carrageenan (CG) was chosen as a cell-friendly printable material. The SF/CG ink exhibited suitable viscosity and shear-thinning properties, coupled with the rapid sol-gel transition of CG. By employing photo-crosslinking of SF, the printability with Pr value close to 1 and structural integrity of the 3D constructs were significantly improved within a matter of seconds. The printed constructs demonstrated a Young's modulus of approximately 250 kPa, making them suitable for keratinocyte and myoblast cell culture. Furthermore, the high cell adhesiveness and viability (maximum >98%) of the loaded cells underscored the considerable potential of this 3D culture scaffold applied for skin and muscle tissues, which can be easily manipulated using an extrusion-based bioprinter.

3D edible scaffolds with yeast protein: A novel alternative protein scaffold for the production of high-quality cell-cultured meat

The purpose of this study was to develop a novel edible scaffold by utilizing yeast proteins, which could partially replace collagen and produce hypoallergenic, odorless, and highly nutritious cell-cultured meat that meets the demands of a more significant number of consumers. The scaffold comprised proanthocyanidins, dialdehyde chitosan, collagen, and different proportions of yeast proteins (YP). The results indicated that the scaffold possessed excellent mechanical properties and biocompatibility, and supported cell proliferation and myogenic differentiation. Additionally, we evaluated the texture characteristics of the cultured meat models and traditional beef and discovered that the YP30 cultured meat model had similar springiness and chewiness as beef. Subsequently, further analyzed the similarity between the cultured meat models and traditional beef in appearance, taste, and nutrition. Further results illustrated that the yeast protein cultured meat model exhibited a complete model structure and comparable color and taste to beef after frying. Moreover, it was concluded that the protein content of the YP30 cultured meat model was closer to that of beef. These findings suggested that the edible scaffold using yeast proteins has enormous potential to facilitate the sustainable development of the cell-cultured meat industry.

Suppressing Chondrocyte Hypertrophy to Build Better Cartilage

Current clinical strategies for restoring cartilage defects do not adequately consider taking the necessary steps to prevent the formation of hypertrophic tissue at injury sites. Chondrocyte hypertrophy inevitably causes both macroscopic and microscopic level changes in cartilage, resulting in adverse long-term outcomes following attempted restoration. Repairing/restoring articular cartilage while minimizing the risk of hypertrophic neo tissue formation represents an unmet clinical challenge. Previous investigations have extensively identified and characterized the biological mechanisms that regulate cartilage hypertrophy with preclinical studies now beginning to leverage this knowledge to help build better cartilage. In this comprehensive article, we will provide a summary of these biological mechanisms and systematically review the most cutting-edge strategies for circumventing this pathological hallmark of osteoarthritis.

RETRACTED: The Dosidicus gigas Collagen for Scaffold Preparation and Cell Cultivation: Mechanical and Physicochemical Properties, Morphology, Composition and Cell Viability

Directed formation of the structure of the culture of living cells is the most important task of tissue engineering. New materials for 3D scaffolds of living tissue are critical for the mass adoption of regenerative medicine protocols. In this manuscript, we demonstrate the results of the molecular structure study of collagen from Dosidicus gigas and reveal the possibility of obtaining a thin membrane material. The collagen membrane is characterized by high flexibility and plasticity as well as mechanical strength. The technology of obtaining collagen scaffolds, as well as the results of studies of its mechanical properties, surface morphology, protein composition, and the process of cell proliferation on its surface, are shown in the given manuscript. The investigation of living tissue culture grown on the surface of a collagen scaffold by X-ray tomography on a synchrotron source made it possible to remodel the structure of the extracellular matrix. It was found that the scaffolds obtained from squid collagen are characterized by a high degree of fibril ordering and high surface roughness and provide efficient directed growth of the cell culture. The resulting material provides the formation of the extracellular matrix and is characterized by a short time to living tissue sorption.

Nanofiber scaffolds based on extracellular matrix for articular cartilage engineering: A perspective

Articular cartilage has a low self-repair capacity due to the lack of vessels and nerves. In recent times, nanofiber scaffolds have been widely used for this purpose. The optimum nanofiber scaffold should stimulate new tissue's growth and mimic the articular cartilage nature. Furthermore, the characteristics of the scaffold should match those of the cellular matrix components of the native tissue to best merge with the target tissue. Therefore, selective modification of prefabricated scaffolds based on the structure of the repaired tissues is commonly conducted to promote restoring the tissue. A thorough analysis is required to find out the architectural features of scaffolds that are essential to make the treatment successful. The current review aims to target this challenge. The article highlights different optimization approaches of nanofibrous scaffolds for improved cartilage tissue engineering. In this context, the influence of the architecture of nanoscaffolds on performance is discussed in detail. Finally, based on the gathered information, a future outlook is provided to catalyze development in this promising field.

Polycaprolactone-chitosan/multi-walled carbon nanotube: A highly strengthened electrospun nanocomposite scaffold for cartilage tissue engineering

Articular cartilage is an avascular connective tissue with a slow healing rate. Tissue engineering scaffolds can provide appropriate condition to stimulate the natural healing mechanism of the damaged tissue. In this study, the electrospun nanocomposite scaffolds based on polycaprolactone (PCL)-chitosan/carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs) were fabricated with different concentrations of MWCNTs including 0.5 and 1 wt%. The samples were characterized in terms of morphology, porosity, physicochemical structure, hydrophilicity, tensile strength, bioactivity, biodegradation and cell response. The scaffold containing 0.5 wt% MWCNTs presented the lowest fiber diameter (99 ± 15 nm) and the highest tensile strength (33.81 ± 6.76 MPa) (p ≤ 0.05), which were considerable for electrospun structures. The porosity percentage of the scaffolds were maintained above 80% which is appropriate for tissue engineering. As the MWCNTs increased, the water contact angle decreased due to the increase in the hydrophilic carboxyl functional groups related to the MWCNTs. MWCNTs increased the crystallinity of the scaffold, leading to a more bioactivity and stability proportional to healing rate of a natural cartilage. Chondrocytes were well cultured on the scaffold containing MWCNTs and presented more cell viability compared to the sample without MWCNTs. The PCL-chitosan/0.5wt.%MWCNTs scaffold can be considered for supplemental studies in cartilage tissue engineering applications.

Three-dimensional cell-laden collagen scaffolds: From biochemistry to bone bioengineering

The bones can be viewed as both an organ and a material. As an organ, the bones give structure to the body, facilitate skeletal movement, and provide protection to internal organs. As a material, the bones consist of a hybrid organic/inorganic three-dimensional (3D) matrix, composed mainly of collagen, noncollagenous proteins, and a calcium phosphate mineral phase, which is formed and regulated by the orchestrated action of a complex array of cells including chondrocytes, osteoblasts, osteocytes, and osteoclasts. The interactions between cells, proteins, and minerals are essential for the bone functions under physiological loading conditions, trauma, and fractures. The organization of the bone's organic and inorganic phases stands out for its mechanical and biological properties and has inspired materials research. The objective of this review is to fill the gaps between the physical and biological characteristics that must be achieved to fabricate scaffolds for bone tissue engineering with enhanced performance. We describe the organization of bone tissue highlighting the characteristics that have inspired the development of 3D cell-laden collagenous scaffolds aimed at replicating the mechanical and biological properties of bone after implantation. The role of noncollagenous macromolecules in the organization of the collagenous matrix and mineralization ability of entrapped cells has also been reviewed. Understanding the modulation of cell activity by the extracellular matrix will ultimately help to improve the biological performance of 3D cell-laden collagenous scaffolds used for bone regeneration and repair as well as for in vitro studies aimed at unravelling physiological and pathological processes occurring in the bone.

PEOT/PBT Polymeric Pastes to Fabricate Additive Manufactured Scaffolds for Tissue Engineering

The advantages of additive manufactured scaffolds, as custom-shaped structures with a completely interconnected and accessible pore network from the micro- to the macroscale, are nowadays well established in tissue engineering. Pore volume and architecture can be designed in a controlled fashion, resulting in a modulation of scaffold’s mechanical properties and in an optimal nutrient perfusion determinant for cell survival. However, the success of an engineered tissue architecture is often linked to its surface properties as well. The aim of this study was to create a family of polymeric pastes comprised of poly(ethylene oxide therephthalate)/poly(butylene terephthalate) (PEOT/PBT) microspheres and of a second biocompatible polymeric phase acting as a binder. By combining microspheres with additive manufacturing technologies, we produced 3D scaffolds possessing a tailorable surface roughness, which resulted in improved cell adhesion and increased metabolic activity. Furthermore, these scaffolds may offer the potential to act as drug delivery systems to steer tissue regeneration.

Biophysical properties of electrospun chitosan-grafted poly(lactic acid) nanofibrous scaffolds loaded with chondroitin sulfate and silver nanoparticles

The aim of this work was to study the biophysical properties of the chitosan-grafted poly(lactic acid) (CH-g-PLA) nanofibers loaded with silver nanoparticles (AgNPs) and chondroitin-4-sulfate (C₄S). The electrospun CH-g-PLA:AgNP:C₄S nanofibers were manufactured using the electrospinning technique. The microstructure of the CH-g-PLA:AgNP:C₄S nanofibers was investigated by proton nuclear magnetic resonance (¹H-NMR), scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), and Fourier transform infrared (ATR-FTIR) spectroscopy. ATR-FTIR and ¹H-NMR confirm the CH grafting successfully by PLA with a substitution degree of 33.4%. The SEM measurement results indicated apparently smooth nanofibers having a diameter range of 340 ± 18 nm with porosity of 89 ± 3.08% and an average pore area of 0.27 μm². UV-Vis and XRD suggest that silver nanoparticles with the size distribution of 30 nm were successfully incorporated into the electrospun nanofibers. The water contact angle of 12.8 ± 2.7° reveals the hydrophilic nature of the CH-g-PLA:AgNP:C₄S nanofibers has been improved by C₄S. The electrospun CH-g-PLA:AgNP:C₄S nanofibers are found to release ions Ag+ at a concentration level capable of rendering an antimicrobial efficacy. Gram-positive bacteria (S.aureus) were more sensitive to CH-g-PLA:AgNP:C₄S than Gram-negative bacteria (E. coli). The electrospun CH-g-PLA:AgNP:C₄S nanofibers exhibited no cytotoxicity to the L-929 fibroblast cells, suggesting cytocompatibility. Fluorescence microscopy demonstrated that C₄S promotes the adhesion and proliferation of fibroblast cells onto electrospun CH-g-PLA:AgNP:C₄S nanofibers.

Structure and biological compatibility of polycaprolactone/zinc-hydroxyapatite electrospun nanofibers for tissue regeneration

Although guided tissue regeneration (GTR) is a useful tool for regenerating lost tissue as bone and periodontal tissue, a biocompatible membrane capable of regenerating large defects has yet to be discovered. This study aimed to characterize the physicochemical properties and biological compatibility of polycaprolactone (PCL) membranes associated with or without nanostructured hydroxyapatite (HA) (PCL/HA) and Zn-doped HA (PCL/ZnHA), produced by electrospinning. PCL, PCL/HA, and PCL/ZnHA were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). Nanoparticles of HA or ZnHA were homogeneously distributed and dispersed inside the PCL fibers, which decreased the fiber thickness. At 1 wt% of HA or ZnHA, these nanoparticles acted as nucleating agents. Moreover, HA and ZnHA increased the onset of the degradation temperature and thermal stability of the electrospun membrane. All tested membranes showed no cytotoxicity and allowed murine pre-osteoblast adhesion and spreading; however, higher concentrations of PCL/ZnHA showed less cells and an irregular cell morphology compared to PCL and PCL/HA. This article presents a cytocompatible, electrospun, nanocomposite membrane with a novel morphology and physicochemical properties that make it eligible as a scaffold for GTR.

Hyaluronic acid hydrogels reinforced with laser spun bioactive glass micro- and nanofibres doped with lithium

The repair of articular cartilage lesions in weight-bearing joints remains as a significant challenge due to the low regenerative capacity of this tissue. Hydrogels are candidates to repair lesions as they have similar properties to cartilage extracellular matrix but they are unable to meet the mechanical and biological requirements for a successful outcome. Here, we reinforce hyaluronic acid (HA) hydrogels with 13-93-lithium bioactive glass micro- and nanofibres produced by laser spinning. The glass fibres are a reinforcement filler and a platform for the delivery of therapeutic lithium-ions. The elastic modulus of the composites is more than three times higher than in HA hydrogels. Modelling of the reinforcement corroborates the experimental results. ATDC5 chondrogenic cells seeded on the composites are viable and more proliferation occurs on the hydrogels containing fibres than in HA hydrogels alone. Furthermore, the chondrogenic behavior on HA constructs with fibres containing lithium is more marked than in hydrogels with no-lithium fibres.

Recent Developed Strategies for Enhancing Chondrogenic Differentiation of MSC: Impact on MSC-Based Therapy for Cartilage Regeneration

Articular cartilage is susceptible to damage, but its self-repair is hindered by its avascular nature. Traditional treatment methods are not able to achieve satisfactory repair effects, and the development of tissue engineering techniques has shed new light on cartilage regeneration. Mesenchymal stem cells (MSCs) are one of the most commonly used seed cells in cartilage tissue engineering. However, MSCs tend to lose their multipotency, and the composition and structure of cartilage-like tissues formed by MSCs are far from those of native cartilage. Thus, there is an urgent need to develop strategies that promote MSC chondrogenic differentiation to give rise to durable and phenotypically correct regenerated cartilage. This review provides an overview of recent advances in enhancement strategies for MSC chondrogenic differentiation, including optimization of bioactive factors, culture conditions, cell type selection, coculture, gene editing, scaffolds, and physical stimulation. This review will aid the further understanding of the MSC chondrogenic differentiation process and enable improvement of MSC-based cartilage tissue engineering.

Elucidation of Antimicrobial Silver Sulfadiazine (SSD) Blend/Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate) Immobilised with Collagen Peptide as Potential Biomaterial

The quest for a suitable biomaterial for medical application and tissue regeneration has resulted in the extensive research of surface functionalization of material. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] is a bacterial polymer well-known for its high levels of biocompatibility, non-genotoxicity, and minimal tissue response. We have designed a porous antimicrobial silver SSD blend/poly(3HB-co-4HB)-collagen peptide scaffold using a combination of simple techniques to develop a scaffold with an inter-connected microporous pore in this study. The collagen peptide was immobilised via -NH₂ group via aminolysis. In order to improve the antimicrobial performance of the scaffold, silver sulfadiazine (SSD) was impregnated in the scaffolds. To confirm the immobilised collagen peptide and SSD, the scaffold was characterized using FTIR. Herein, based on the cell proliferation assay of the L929 fibroblast cells, enhanced bioactivity of the scaffold with improved wettability facilitated increased cell proliferation. The antimicrobial activity of the SSD blend/P(3HB-co-4HB)-collagen peptide in reference to the pathogenic Gram-negative, Gram-positive bacteria and yeast Candida albicans exhibited SSD blend/poly(3HB-co-4HB)-12.5 wt% collagen peptide as significant construct of biocompatible antibacterial biomaterials. Thus, SSD blend/P(3HB-co-4HB)-collagen peptide scaffold from this finding has high potential to be further developed as biomaterial.

Application of electrospun nanofibers in bone, cartilage and osteochondral tissue engineering

Tissue damage related to bone and cartilage is a common clinical disease. Cartilage tissue has no blood vessels and nerves. The limited cell migration ability results in low endogenous healing ability. Due to the complexity of the osteochondral interface, the clinical treatment of osteochondral injury is limited. Tissue engineering provides new ideas for solving this problem. The ideal tissue engineering scaffold must have appropriate porosity, biodegradability and specific functions related to tissue regeneration, especially bioactive polymer nanofiber composite materials with controllable biodegradation rate and appropriate mechanical properties have been getting more and more research. The nanofibers produced by electrospinning have high specific surface area and suitable mechanical properties, which can effectively simulate the natural extracellular matrix (ECM) of bone or cartilage tissue. The composition of materials can affect mechanical properties, plasticity, biocompatibility and degradability of the scaffold, thereby further affect the repair efficiency. This article reviews the characteristics of polymer materials and the application of its electrospun nanofibers in bone, cartilage and osteochondral tissue engineering.

Chondrogenic differentiation of Wharton's Jelly mesenchymal stem cells on silk spidroin-fibroin mix scaffold supplemented with L-ascorbic acid and platelet rich plasma

In this research, hWJ-MSCs were grown on silk scaffolds and induced towards chondrogenesis by supplementation with L-ascorbic acid (LAA) or platelet rich plasma (PRP). Silk scaffolds were fabricated with salt leaching method by mixing silk fibroin (SF) with silk spidroin (SS). The silk fibroin was obtained from Bombyx mori cocoon that had been degummed, and the silk spidroin was obtained from wild-type spider Argiope appensa. The effect of scaffold composition and inducer on cell proliferation was observed through MTT assay. The most optimal treatment then continued to be used to induce hWJ-MSC towards chondrogenic differentiation for 7 and 21 days. Scaffolds characterization showed that the scaffolds produced had 3D structure with interconnected pores, and all were biocompatible with hWJ-MSCs. Scaffold with the addition of 10% SS + 90% SF showed higher compressive strength and better pore interconnectivity in comparison to 100% silk fibroin scaffold. After 48 h, cells seeded on scaffold with spidroin and fibroin mix had flattened morphology in comparison to silk fibroin scaffold which appeared to be more rounded on the scaffold surface. Scaffold with 10% (w/w) of silk spidroin (SS) + 90% (w/w) of silk fibroin (SF) was the most optimal composition for cell proliferation. Immunocytochemistry of integrin β1 and RGD sequence, showed that scaffold with SS 10% provide better cell attachment with the presence of RGD sequence from the spidroin silk which could explain the higher cell proliferation than SF100% scaffold. Based on Alcian Blue staining and Collagen Type II immunocytochemistry (ICC), cells grown on 10% SS + 90% SF scaffold with 10% PRP supplementation were the most optimal to support chondrogenesis of hWJ-MSCs. These results showed that the addition of spidroin silk from A. appensa. had impact on scaffold compressive strength and chondrogenic differentiation of hWJ-MSC and had the potential for further development of bio-based material scaffold in cartilage tissue engineering.

Repair of Damaged Articular Cartilage: Current Approaches and Future Directions

Articular hyaline cartilage is extensively hydrated, but it is neither innervated nor vascularized, and its low cell density allows only extremely limited self-renewal. Most clinical and research efforts currently focus on the restoration of cartilage damaged in connection with osteoarthritis or trauma. Here, we discuss current clinical approaches for repairing cartilage, as well as research approaches which are currently developing, and those under translation into clinical practice. We also describe potential future directions in this area, including tissue engineering based on scaffolding and/or stem cells as well as a combination of gene and cell therapy. Particular focus is placed on cell-based approaches and the potential of recently characterized chondro-progenitors; progress with induced pluripotent stem cells is also discussed. In this context, we also consider the ability of different types of stem cell to restore hyaline cartilage and the importance of mimicking the environment in vivo during cell expansion and differentiation into mature chondrocytes.

Hybrid graphene-ceramic nanofibre network for spontaneous neural differentiation of stem cells

A challenge in regenerative medicine is governed by the need to have control over the fate of stem cells that is regulated by the physical and chemical microenvironment in vitro and in vivo. The differentiation of the stem cells into specific lineages is commonly guided by use of specific culture media. For the first time, we demonstrate that human mesenchymal stem cells are capable of turning spontaneously towards neurogenic lineage when seeded on graphene-augmented, highly anisotropic ceramic nanofibres without special differentiation media, contrary to commonly thought requirement of 'soft' substrates for the same purpose. Furthermore, pro-inflammatory gene expression is simultaneously suppressed, and expression of factors promoting focal adhesion and monocytes taxis is upregulated. This opens new possibilities of using local topo-mechanical cues of the 'graphenized' scaffold surfaces to guide stem cell proliferation and differentiation, which can be used in studies of neurological diseases and cell therapy.

Evaluation of in vitro chondrocytic differentiation: A stem cell research initiative at the King Abdulaziz University, Kingdom of Saudi Arabia

Mesenchymal stem cells (MSCs) from various sources have been used in cartilage differentiation with variable success. Therefore, it is of interest to evaluate the in vitro differentiation potential of the hWJSCs derived from the human umbilical cords into chondrocytes at the stem cell research facility at the King Abdulaziz University. hWJSCs are an attractive choice for tissue engineering and regenerative medical applications including cartilage regeneration. We evaluated the hWJSCs using classical histological and cartilage related gene expression studies. Some of the known parameters were re-examined for consistency at the current laboratory conditions. Early passages (P1-P4) showed short fibroblastic morphology and high expression of MSC related surface markers namely CD29 (99.9%), CD44 (97.8%), CD73 (99.6%), CD90 (95.1%) and CD105 (98.9%). MTT assay showed time dependent increase in hWJSCs proliferation by 61.06% and 206.31% at 48h and 72h respectively. Toluidine blue histology showed that hWJSCs were successfully differentiated into chondrocytes in chondrocytic differentiation medium for 21 days. Differentiated hWJSCs also showed significantly increased expression of collagen type II, aggrecan and SOX9 compared to the undifferentiated control. It should be noted that the determination of the average cell yield, the population doubling time and histological staining wtih alcian blue and/or safronin O is required in future studies for improved evaluation of differentiation. Painless derivation, abundance of stem cells that are hypo-immunogenic and safety issues makes this method advantages to MSCs derived from other sources.

Silk fibroin-Pellethane® cardiovascular patches: Effect of silk fibroin concentration on vascular remodeling in rat model

Life-threatening cardiovascular anomalies require surgery for structural repair with cardiovascular patches. The biomaterial patch, derived from Bombyx mori silk fibroin (SF), is used as an alternative material due to its excellent tissue affinity and biocompatibility. However, SF lacks the elastomeric characteristics required for a cardiovascular patch. In order to overcome this shortcoming, we combined the thermoplastic polyurethane, Pellethane® (PU) with SF to develop an elastic biocompatible patch. Therefore, the purpose of this study was to investigate the feasibility of the blended SF/PU patch in a vascular model. Additionally, we focused on the effects of different SF concentrations in the SF/PU patch on its biological and physical properties. Three patches of different compositions (SF, SF7PU3 and SF4PU6) were created using an electrospinning method. Each patch type (n = 18) was implanted into rat abdominal aorta and histopathology was assessed at 1, 3, and 6 months post-implantation. The results showed that with increasing SF content the tensile strength and elasticity decreased. Histological evaluation revealed that inflammation gradually decreased in the SF7PU3 and SF patches throughout the study period. At 6 months post-implantation, the SF7PU3 patch demonstrated progressive remodeling, including significantly higher tissue infiltration, elastogenesis and endothelialization compared with SF4PU6. In conclusion, an increase of SF concentration in the SF/PU patch had effects on vascular remodeling and physical properties. Moreover, our blended patch might be an attractive alternative material that could induce the growth of a neo-artery composed of tissue present in native artery.

Current State of Cartilage Tissue Engineering using Nanofibrous Scaffolds and Stem Cells

Cartilage is an avascular, aneural, and alymphatic connective tissue with a limited capacity caused by low mitotic activity of its resident cells, chondrocytes. Natural repair of full thickness cartilage defects usually leads to the formation of fibrocartilage with lower function and mechanical force compared with the original hyaline cartilage and further deterioration can occur. Tissue engineering and regenerative medicine is a promising strategy to repair bone and articular cartilage defects and rehabilitate joint functions by focusing on the optimal combination of cells, material scaffolds, and signaling molecules. The unique physical and topographical properties of nanofibrous structures allow them to mimic the extracellular matrix of native cartilage, making an appropriate resemblance to induce cartilage tissue regeneration and reconstruction. To improve simulation of native cartilage, the incorporation of nanofibrous scaffolds with suitable corresponsive cells could be effective. In this review article, an attempt was made to present the current state of cartilage tissue engineering using nanofibrous scaffolds and stem cells as high proliferative immune privilege cells with chondrogenic differentiation ability. The comprehensive information was retrieved by search of relevant subject headings in Medline/Pubmed and Elsevier databases.

Chondrogenic Potential of Peripheral Blood Derived Mesenchymal Stem Cells Seeded on Demineralized Cancellous Bone Scaffolds

As a cell source with large quantity and easy access, peripheral blood mesenchymal stem cells (PBMSCs) were isolated and seeded in porcine demineralized cancellous bone (DCB) scaffolds, cultured in chondrogenic medium and evaluated for in vitro chondrogenesis. Bone marrow MSCs (BMMSCs) and articular cartilage chondrocytes (ACCs) underwent the same process as controls. The morphology, viability and proliferation of PBMSCs in DCB scaffolds were similar to those of BMMSCs and ACCs. PBMSCs and BMMSCs showed similar chondrogenesis potential with consistent production of COL 2 and SOX 9 protein and increased COL 2 and AGC mRNA expressions at week 3 but the COL 2 protein production was still less than that of ACCs. Minimal increase of hypertrophic markers was found in all groups. Relatively higher ALP and lower COL 10 mRNA expressions were found in both MSCs groups at week 3 than that in ACCs, whereas no significant difference of COL 1 and SOX 9 mRNA and MMP 13 protein was found among all groups. To conclude, PBMSCs shared similar proliferation and chondrogenic potential with BMMSCs in DCB scaffolds and could be an alternative to BMMSCs for cartilage tissue engineering. Further optimization of chondrogenesis system is needed regardless of the promising results.

Elastomers in vascular tissue engineering

Elastomers are popular in vascular engineering applications, as they offer the ability to design implants that match the compliance of native tissue. By mimicking the natural tissue environment, elastic materials are able to integrate within the body to promote repair and avoid the adverse physiological responses seen in rigid alternatives that often disrupt tissue function. The design of elastomers has continued to evolve, moving from a focus on long term implants to temporary resorbable implants that support tissue regeneration. This has been achieved through designing chemistries and processing methodologies that control material behavior and bioactivity, while maintaining biocompatibility in vivo. Here we review the latest developments in synthetic and natural elastomers and their application in cardiovascular treatments.