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It suggests that the poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) scaffold can be used for cartilage tissue engineering, but PHBV is short of bioactivity that is required for cartilage regeneration. To fabricate a bioactive cartilage tissue engineering scaffold that promotes cartilage regeneration, quercetin (QUE) modified PHBV (PHBV-g-QUE) fibrous scaffolds were prepared by a two-step surface modification method. The PHBV-g-QUE fibrous scaffold facilitates the growth of chondrocytes and maintains chondrocytic phenotype resulting from the upregulation of SOX9, COL II, and ACAN. The PHBV-g-QUE fibrous scaffold inhibited apoptosis of chondrocyte and reduced oxidative stress of chondrocytes by regulating the transcription of related genes. Following PHBV-g-QUE fibrous scaffolds and PHBV fibrous scaffolds with adhered chondrocytes were implanted into nude mice for 4 weeks, it demonstrated that PHBV-g-QUE fibrous scaffolds significantly promoted cartilage regeneration compared with the PHBV fibrous scaffolds. Hence, it suggests that the PHBV-g-QUE fibrous scaffold can be potentially applied in the clinical treatment of cartilage defects in the future., (© 2021. The Author(s).)

Intervertebral disc (IVD) degeneration often leads to low back pain, which is one of the major causes of disability worldwide, affecting more than 80% of the population. Although available treatments for degenerated IVD decrease symptoms' progression, they fail to address the underlying causes and to restore native IVD properties. Poly(γ-glutamic acid) (γ-PGA) has recently been shown to support the production of chondrogenic matrix by mesenchymal stem/stromal cells. γ-PGA/chitosan (Ch) nanocomplexes (NCs) have been proposed for several biomedical applications, showing advantages compared with either polymer alone. Hence, this study explores the potential of γ-PGA and γ-PGA/Ch NCs for IVD regeneration. Nucleotomised bovine IVDs were cultured ex vivo upon injection of γ-PGA (pH 7.4) and γ-PGA/Ch NCs (pH 5.0 and pH 7.4). Tissue metabolic activity and nucleus pulposus DNA content were significantly reduced when NCs were injected in acidic-buffered solution (pH 5.0). However, at pH 7.4, both γ-PGA and NCs promoted sulphated glycosaminoglycan production and significant type II collagen synthesis, as determined at the protein level. This study is a first proof of concept that γ-PGA and γ-PGA/Ch NCs promote recovery of IVD native matrix, opening new perspectives on the development of alternative therapeutic approaches for IVD degeneration.

Collagen type-II is the dominant type of collagen in articular cartilage and chondroitin sulfate is one of the main components of cartilage extracellular matrix. Afibrillar and fibrillar type-II atelocollagen scaffolds with and without chondroitin sulfate were prepared using casting and freeze-drying methods. The scaffolds were characterised to highlight the effects of fibrillogenesis and chondroitin sulfate addition on viscosity, pore structure, porosity and mechanical properties. Microstructure analysis showed that fibrillogenesis increased the circularity of pores significantly in collagen-only scaffolds, whereas with it, no significant change was observed in chondroitin sulfate-containing scaffolds. Addition of chondroitin sulfate to afibrillar scaffolds increased the circularity of the pores and the proportion of pores between 50 and 300 μm suitable for chondrocytes growth. Fourier transform infrared spectroscopy explained the bonding between chondroitin sulfate and afibrillar collagen- confirmed with rheology results- which increased the compressive modulus 10-fold to 0.28 kPa. No bonding was observed in other scaffolds and consequently no significant changes in compressive modulus were detected.

The biocompatibility and biomimetic properties of chitosan make it attractive for tissue engineering but its use is limited by its cell adhesion properties. Our objectives were to produce and characterize chitosan and reacetylated-chitosan fibrous scaffolds coated with type II collagen and to evaluate the effect of these chemical modifications on mesenchymal stem cell (MSC) adhesion. Chitosan and reacetylated-chitosan scaffolds obtained by a wet spinning method were coated with type II collagen. Scaffolds were characterized prior to seeding with MSCs. The constructs were analyzed for cell binding kinetics, numbers, distribution and viability. Cell attachment and distribution were improved on chitosan coated with type II collagen. MSCs adhered less to reacetylated-chitosan and collagen coating did not improve MSCs attachment on those scaffolds. These findings are promising and encourage the evaluation of the differentiation of MSCs in collagen-coated chitosan scaffolds. However, the decreased cell adhesion on reacetylated chitosan scaffold seems difficult to overcome and will limit its use for tissue engineering.

Cartilage extracellular matrix (ECM) is composed primarily of type II collagen (COL II) and large, networks of proteoglycans (PGs) that contain glycosaminoglycans such as hyaluronic acid (HA) and chondroitin sulfate (CS). Since cartilage shows little tendency for self-repair, injuries are kept unhealed for years and can eventually lead to further degeneration. During the past decades, many investigations have pursued techniques to stimulate articular cartilage repair or regeneration. The current study assessed the effects of exogenous glycosaminoglycans (GAGs) including CS-A, CS-B, CS-C, heparan sulfate and HA, administration on human chondrocytes in terms of proliferation and matrix synthesis, while the cells were seeded and grown on the genipin-crosslinked collagen type II (COL II) scaffold. DNA content was measured by Hoechst dye intercalation, matrix deposition was evaluated by DMMB dye. Expression of collagen II and aggrecan mRNAs was assessed by RT-PCR, followed by gel electrophoresis. In a 28-day in vitro culture, administration of 5 microg/ml CS-A, 50 microg/ml CS-B, 50 microg/ml CS-C, 5 microg/ml HS, and 500 kDa HA led to significant increase in biosynthesis rate of PGs. Gene expression of aggrecan and collagen II were upregulated by CS-A, CS-C and HA. These results showed considerable relevance of GAGs to the issue of in vitro/ex vivo neo-cartilage synthesis for tissue engineering and regenerative medical applications.

To construct a novel scaffold for nucleus pulposus (NP) tissue engineering, The porous type II collagen (CII)/hyaluronate (HyA)-chondroitin-6-sulfate (6-CS) scaffold was prepared using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) cross-linking system. The physico-chemical properties and biocompatibility of CII/HyA-CS scaffolds were evaluated. The results suggested CII/HyA-CS scaffolds have a highly porous structure (porosity: 94.8 +/- 1.5%), high water-binding capacity (79.2 +/- 2.8%) and significantly improved mechanical stability by EDC/NHS crosslinking (denaturation temperature: 74.6 +/- 1.8 and 58.1 +/- 2.6 degrees C, respectively, for the crosslinked scaffolds and the non-crosslinked; collagenase degradation rate: 39.5 +/- 3.4 and 63.5 +/- 2.0%, respectively, for the crosslinked scaffolds and the non-crosslinked). The CII/HyA-CS scaffolds also showed satisfactory cytocompatibility and histocompatibility as well as low immunogenicity. These results indicate CII/HyA-CS scaffolds may be an alternative material for NP tissue engineering due to the similarity of its composition and physico-chemical properties to those of the extracellular matrices (ECM) of native NP.

Collagen has been used as a coating material for titanium-based implants for bone contact and as a component of scaffolds for bone tissue engineering. In general collagen type I has been used, however very little attention has been focussed on collagen type II. Collagen-based coatings and scaffolds have been enhanced by the incorporation of the glycosaminoglycan chondroitin sulphate (CS), however the proteglycan biglycan, which is found in bone and contains glycosaminoglycan chains consisting of CS, has not been used as a biomaterial component. The study had the following aims: firstly, five different collagen II preparations were compared with regard to their ability to bind CS and biglycan and the changes in fibril morphology thereby induced. Secondly, the effects of biglycan on the adhesion of primary rat osteoblasts (rO) as well as the proliferation of rO, primary human osteoblasts (hO) and the osteoblast-like cell line 7F2 were studied by culturing the cells on surfaces coated with collagen II fibrils containing biglycan. Fibrils of the collagen II preparation which bound the most biglycan were used to coat titanium surfaces. Bare titanium, titanium coated with collagen II fibrils and titanium coated with collagen II fibrils containing biglycan were compared. It was found that different collagen II preparations showed different affinities for CS and biglycan. In four of the five preparations tested, biglycan reduced fibril diameter, however the ability of a preparation to bind more biglycan did not appear to lead to a greater reduction in fibril diameter. Fibrils containing biglycan promoted the formation of focal adhesions by rO and significantly enhanced the proliferation of hO but not of rO or 7F2 cells. These results should encourage further investigation of biglycan as a component of collagen-based scaffolds and/or coatings.

Three-dimensional biodegradable porous type II collagen scaffolds are interesting materials for cartilage tissue engineering. This study reports the preparation of porous type II collagen-chondroitin sulfate (CS) scaffold using variable concentrations of 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The physico-chemical properties and ultrastructural morphology of the collagen scaffolds were determined. Then, isolated chondrocytes were cultured in porous type II collagen scaffolds either in the presence and/or absence of covalently attached CS up to 14 days. Cell proliferation, the total amount of proteoglycans and type II collagen retained in the scaffold and chondrocytes morphology were evaluated. The results suggest that EDC-crosslinking improves the mechanical stability of collagen-CS scaffolds with increasing EDC concentration. Cell proliferation and the total amount of proteoglycans and type II collagen retained in the scaffolds were higher in type II collagen-CS scaffolds. Histological analysis showed the formation of a denser cartilaginous layer at the scaffold periphery. Scanning electron microscopy (SEM) revealed chondrocytes distributed the porous surface of both scaffolds maintained their spherical morphology. The results of the present study also indicate that type II collagen-CS scaffolds have potential for use in tissue engineering.

Collagen II is the majority of extracellular matrix components in articular cartilage, which with the major functions of preventing expansion of the tissue and distributing the load of body weight. To obtain man-made ECM, the reconstitution of collagen could be conducted in the presence of negatively charged polysaccharide, such as alginate. Alginate is an anionic polysaccharide capable of eversible gelated in calcium ion solution to prepare different shapes of biomaterials. Its well-known biocompatibility makes it an ideal material in biomedical applications. Thus, the aim of this study was to evaluate the effects of alginate on the fibrillogenesis of type II collagen. The preliminary results revealed that inclusion of alginate into soluble type II collagen solution could inhibit the development of turbidity of collagen solution, and the apparent rate constants in lag and growth phases decreased during collagen formation period, both rate constants decreased to about one-third of the original constants, respectively. From TEM observations, the collagen fibrils were significantly thicker in 0.05% and 0.1% alginate as compared with pure collagen solution. Furthermore, the D-periods of collagen fibers kept unchanged significantly under all reconstituted conditions, which meant the packing of collagen monomer was probably not affected by adding these amounts of alginate.