Growth and differentiation of prechondrogenic cells on bioactive self-assembled peptide nanofibers

Targeting FGFR3 signaling and drug repurposing for the treatment of SLC26A2-related chondrodysplasia in mouse model

Background

Mutations in Slc26a2 cause a spectrum of autosomal-recessive chondrodysplasia with a significant and negligible influence on the quality of life. It has been reported that Slc26a2 deficiency triggers the ATF6 branch of the UPR, which may, in turn, activate the negative regulator of the FGFR3 signaling pathway. However, the correlation between the deletion of Slc26a2 and the augmentation of downstream phosphorylation of FGFR3 has not been investigated in vivo.

Methods

First, we constructed Slc26a2 and Fgfr3 double knockout mouse lines and observed gross views of the born mice and histological staining of the tibial growth plates. The second approach was to construct tamoxifen-inducible Cre-ERT2 mouse models to replicate SLC26A2-related non-lethal dysplastic conditions. Pharmacological intervention was performed by administering the FGFR3 inhibitor NVP-BGJ398. The effect of NVP-BGJ398 on chondrocytes was assessed by Alcian blue staining, proliferation, apoptosis, and chondrocyte-specific markers and then verified by western blotting for variations in the downstream markers of FGFR3. The growth process was detected using X-rays, micro-CT examination, histomorphometry staining of growth plates, and immunofluorescence.

Results

Genetic ablation of Fgfr3 in embryonic Slc26a2-deficient chondrocytes slightly attenuated chondrodysplasia. Subsequently, in the constructed mild dysplasia model, we found that postnatal intervention with Fgfr3 gene in Slc26a2-deficient chondrocytes partially alleviated chondrodysplasia. In chondrocyte assays, NVP-BGJ398 suppressed the defective phenotype of Slc26a2-deficient chondrocytes and restored the phosphorylation downstream of FGFR3 in a concentration-dependent manner. In addition, in vivo experiments showed significant alleviation of impaired chondrocyte differentiation, and micro-CT analysis showed a clear improvement in trabecular bone microarchitectural parameters.

Conclusion

Our results suggested that inhibition of FGFR3 signaling pathway overactivation and NVP-BGJ398 has promising therapeutic implications for the development of SLC26A2-related skeletal diseases in humans.

The translational potential of this article

Our data provide genetic and pharmacological evidence that targeting FGFR3 signaling via NVP-BGJ398 could be a route for the treatment of SLC26A2-associated skeletal disorders, which promisingly advances translational applications and therapeutic development.

Designed peptide amphiphiles as scaffolds for tissue engineering

Peptide amphiphiles (PAs) are peptide-based molecules that contain a peptide sequence as a head group covalently conjugated to a hydrophobic segment, such as lipid tails. They can self-assemble into well-ordered supramolecular nanostructures such as micelles, vesicles, twisted ribbons and nanofibers. In addition, the diversity of natural amino acids gives the possibility to produce PAs with different sequences. These properties along with their biocompatibility, biodegradability and a high resemblance to native extracellular matrix (ECM) have resulted in PAs being considered as ideal scaffold materials for tissue engineering (TE) applications. This review introduces the 20 natural canonical amino acids as building blocks followed by highlighting the three categories of PAs: amphiphilic peptides, lipidated peptide amphiphiles and supramolecular peptide amphiphile conjugates, as well as their design rules that dictate the peptide self-assembly process. Furthermore, 3D bio-fabrication strategies of PAs hydrogels are discussed and the recent advances of PA-based scaffolds in TE with the emphasis on bone, cartilage and neural tissue regeneration both in vitro and in vivo are considered. Finally, future prospects and challenges are discussed.

Sulfated GAG mimetic peptide nanofibers enhance chondrogenic differentiation of mesenchymal stem cells in 3D in vitro models

Articular cartilage, which is exposed to continuous repetitive compressive stress, has limited self-healing capacity in the case of trauma. Thus, it is crucial to develop new treatment options for the effective regeneration of the cartilage tissue. Current cellular therapy treatment options are microfracture and autologous chondrocyte implantation; however, these treatments induce the formation of fibrous cartilage, which degenerates over time, rather than functional hyaline cartilage tissue. Tissue engineering studies using biodegradable scaffolds and autologous cells are vital for developing an effective long-term treatment option. 3D scaffolds composed of glycosaminoglycan-like peptide nanofibers are synthetic, bioactive, biocompatible, and biodegradable and trigger cell-cell interactions that enhance chondrogenic differentiation of cells without using any growth factors. We showed differentiation of mesenchymal stem cells into chondrocytes in both 2D and 3D culture, which produce a functional cartilage extracellular matrix, employing bioactive cues integrated into the peptide nanofiber scaffold without adding exogenous growth factors.

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.

Extracellular Nucleotides Selectively Induce Migration of Chondrocytes and Expression of Type II Collagen

The migration of chondrocytes from healthy to injured tissues is one of the most important challenges during cartilage repair. Additionally, maintenance of the chondrogenic phenotype remains another limitation, especially during monolayer culture in vitro. Using both the differentiated and undifferentiated chondrogenic ATDC5 cell line, we showed that extracellular nucleotides are able to increase the migration rate of chondrocytes without affecting their chondrogenic phenotype. We checked the potency of natural nucleotides (ATP, ADP, UTP, and UDP) as well as their stable phosphorothioate analogs, containing a sulfur atom in the place of one nonbridging oxygen atom in a phosphate group. We also detected P2y1, P2y2, P2y4, P2y6, P2y12, P2y13, and P2y14 mRNA transcripts for nucleotide receptors, demonstrating that P2y1 and P2y13 are highly upregulated in differentiated ATDC5 cells. We showed that ADPβS, UDPβS, and ADP are the best stimulators of migration of differentiated chondrocytes. Additionally, ADP and ADPβS positively affected the expression of type II collagen, a structural component of the cartilage matrix.

Glutamic acid-based dendritic peptides for scaffold-free cartilage tissue engineering

Current treatment modalities for cartilage regeneration often result in the production of fibrous-type cartilage tissue at the defect site, which has inferior mechanical properties as compared to native hyaline cartilage. Further, effective treatments are not available at present, for preventing age-related as well as disease-related hypertrophic development of chondrocytes. In the present study, we designed and synthesized three sets of glutamic acid-based dendritic peptides, differing in degree of lipidation as well as branching. Each set constitutes of N-terminal protected as well as corresponding N-deprotected peptides. Altogether, six peptides [BE12, E12, BE3(12)4, E3(12)4, BE3OMe, E3OMe] were tested for their chondrogenesis enhancing potential in vitro, using rabbit adipose derived mesenchymal stem cells (ADMSCs). Immunohistochemical and gene expression studies as well as biochemical analyses revealed that the lipopeptides [E12 and BE3(12)4] are able to enhance chondrogenic differentiation of ADMSCs significantly (p < 0.001) as compared to control group (chondrogenic medium alone). Glycosaminoglycan content, and the chondrogenic marker genes like Aggrecan (Acan), Type II collagen (Col2a1), Hyaluronan synthase 2 (Has2), and SRY-box 9 (Sox9) expressions were found to be significantly increased in E12 and BE3(12)4 treated groups. Most importantly, the BE3(12)4 treated group showed significantly lower Type I collagen (Col1a2) and Type X collagen (Col10a1) transcript levels (p < 0.001), indicating its potential for hyaline cartilage formation and also to prevent hypertrophic development. Thus, the lipopeptides E12 and BE3(12)4 may be useful for preventing chondrocyte hypertrophy and realizing the hyaline nature of regenerated cartilage tissue in tissue engineering. STATEMENT OF SIGNIFICANCE: The current treatment modalities for degenerative cartilage diseases are unsatisfactory as the resultant regenerated cartilage is often fibrous in nature with inferior mechanical properties. Further, there is no proper treatment available for age-related development of chondrocyte hypertrophy at present. In this study we synthesized glutamic acid-based lipopeptides, which differ in the degree of lipidation as well as branching. We used a combinatorial approach of scaffold-free tissue engineering and dendritic lipopeptides to achieve hyaline-like cartilage tissue from adipose derived mesenchymal stem cells in vitro. Gene expression analysis revealed the down regulation of fibrous cartilage marker Col1a2 and hypertrophic marker Col10a1, suggesting that these lipopeptides may be useful for achieving mechanically superior hyaline cartilage regeneration in future.

A novel glucosamine derivative with low cytotoxicity enhances chondrogenic differentiation of ATDC5

Glucosamine (GlcN) is a component of native cartilage extracellular matrix and useful in cartilage repair, but it was limited by toxicity in high concentrations. With the aim of altering bioactive properties of GlcN to reduce the toxicity and to facilitate chondrogenesis for hyaline cartilage formation, we introduced an amino-group modification with double bond into GlcN to produce N-acryloyl-glucosamine (AGA). The cell ATDC5 was chosen to evaluate its cytotoxicity and chondrogenesis capability. Cell proliferation and cytotoxicity assay showed that AGA had significantly reduced the cytotoxicity compared to GlcN, and promoted ATDC5 proliferation. Alcian blue staining and biochemical analysis indicated that AGA enhanced extracellular matrix deposition. Both the mRNA and protein levels of articular cartilage markers, like Collagen II and Aggrecan were up-regulated, as shown by quantitative real-time PCR and immunofluorescence staining. Moreover, the level of fibrocartilage marker Collagen I and hypertrophic marker Collagen Χ weren't significantly changed. Overall, these results demonstrated that the AGA achieved the functional double-bond, reduction in toxicity and enhancement in chondrogenesis could be more potential in cartilage repair.

Presentation of functional groups on self-assembled supramolecular peptide nanofibers mimicking glycosaminoglycans for directed mesenchymal stem cell differentiation

Organizational complexity and functional diversity of the extracellular matrix regulate cellular behaviors.

Effects of cholic acid modified glucosamine on chondrogenic differentiation

Glucosamine hydrochloride is a widely used drug for the treatment of osteoarthritis and can be easily modified by other molecules because of its alterable functional groups.

Basal Lamina Mimetic Nanofibrous Peptide Networks for Skeletal Myogenesis

Extracellular matrix (ECM) is crucial for the coordination and regulation of cell adhesion, recruitment, differentiation and death. Therefore, equilibrium between cell-cell and cell-matrix interactions and matrix-associated signals are important for the normal functioning of cells, as well as for regeneration. In this work, we describe importance of adhesive signals for myoblast cells' growth and differentiation by generating a novel ECM mimetic peptide nanofiber scaffold system. We show that not only structure but also composition of bioactive signals are important for cell adhesion, growth and differentiation by mimicking the compositional and structural properties of native skeletal muscle basal lamina. We conjugated laminin-derived integrin binding peptide sequence, "IKVAV", and fibronectin-derived well known adhesive sequence, "RGD", into peptide nanostructures to provide adhesive and myogenic cues on a nanofibrous morphology. The myogenic and adhesive signals exhibited a synergistic effect on model myoblasts, C2C12 cells. Our results showed that self-assembled peptide nanofibers presenting laminin derived epitopes support adhesion, growth and proliferation of the cells and significantly promote the expression of skeletal muscle-specific marker genes. The functional peptide nanofibers used in this study present a biocompatible and biodegradable microenvironment, which is capable of supporting the growth and differentiation of C2C12 myoblasts into myotubes.

Self-Assembly and Collagen-Stimulating Activity of a Peptide Amphiphile Incorporating a Peptide Sequence from Lumican

The self-assembly and bioactivity of a peptide amphiphile (PA) incorporating a 13-residue sequence derived from the last 13 amino acids of the C-terminus of lumican, C16-YEALRVANEVTLN, attached to a hexadecyl (C16) lipid chain have been examined. Lumican is a proteoglycan found in many types of tissue and is involved in collagen fibril organization. A critical aggregation concentration (cac) for the PA was determined through pyrene fluorescence measurements. The structure of the aggregates was imaged using electron microscopy, and twisted and curved nanotapes were observed. In situ small-angle X-ray scattering and fiber X-ray diffraction reveal that these tapes contain interdigitated bilayers of the PA molecules. FTIR and circular dichroism spectroscopy and fiber X-ray diffraction indicate that the lumican sequence in the PA adopts a β-sheet secondary structure. Cell assays using human dermal fibroblasts show that below the cac the PA displays good biocompatibility and also stimulates collagen production over a period of 3 weeks, exceeding a 2-fold enhancement for several concentrations. Thus, this PA has promise in future biological applications, in particular, in tissue engineering.

Bioactive supramolecular peptide nanofibers for regenerative medicine

Recent advances in understanding of cell-matrix interactions and the role of the extracellular matrix (ECM) in regulation of cellular behavior have created new perspectives for regenerative medicine. Supramolecular peptide nanofiber systems have been used as synthetic scaffolds in regenerative medicine applications due to their tailorable properties and ability to mimic ECM proteins. Through designed bioactive epitopes, peptide nanofiber systems provide biomolecular recognition sites that can trigger specific interactions with cell surface receptors. The present Review covers structural and biochemical properties of the self-assembled peptide nanofibers for tissue regeneration, and highlights studies that investigate the ability of ECM mimetic peptides to alter cellular behavior including cell adhesion, proliferation, and/or differentiation.

Regenerative nanomedicine: current perspectives and future directions

Nanotechnology has considerably accelerated the growth of regenerative medicine in recent years. Application of nanotechnology in regenerative medicine has revolutionized the designing of grafts and scaffolds which has resulted in new grafts/scaffold systems having significantly enhanced cellular and tissue regenerative properties. Since the cell–cell and cell-matrix interaction in biological systems takes place at the nanoscale level, the application of nanotechnology gives an edge in modifying the cellular function and/or matrix function in a more desired way to mimic the native tissue/organ. In this review, we focus on the nanotechnology-based recent advances and trends in regenerative medicine and discussed under individual organ systems including bone, cartilage, nerve, skin, teeth, myocardium, liver and eye. Recent studies that are related to the design of various types of nanostructured scaffolds and incorporation of nanomaterials into the matrices are reported. We have also documented reports where these materials and matrices have been compared for their better biocompatibility and efficacy in supporting the damaged tissue. In addition to the recent developments, future directions and possible challenges in translating the findings from bench to bedside are outlined.

Designer functionalised self-assembling peptide nanofibre scaffolds for cartilage tissue engineering

Owing to the limited regenerative capacity of cartilage tissue, cartilage repair remains a challenge in clinical treatment. Tissue engineering has emerged as a promising and important approach to repair cartilage defects. It is well known that material scaffolds are regarded as a fundamental element of tissue engineering. Novel biomaterial scaffolds formed by self-assembling peptides consist of nanofibre networks highly resembling natural extracellular matrices, and their fabrication is based on the principle of molecular self-assembly. Indeed, peptide nanofibre scaffolds have obtained much progress in repairing various damaged tissues (e.g. cartilage, bone, nerve, heart and blood vessel). This review outlines the rational design of peptide nanofibre scaffolds and their potential in cartilage tissue engineering.

Glycosaminoglycan mimetic peptide nanofibers promote mineralization by osteogenic cells

Bone tissue regeneration is accomplished by concerted regulation of protein-based extracellular matrix components, glycosaminoglycans (GAGs) and inductive growth factors. GAGs constitute a significant portion of the extracellular matrix and have a significant impact on regulating cellular behavior, either directly or through encapsulation and presentation of growth factors to the cells. In this study we utilized a supramolecular peptide nanofiber system that can emulate both the nanofibrous architecture of collagenous extracellular matrix and the major chemical composition found on GAGs. GAGs and collagen mimetic peptide nanofibers were designed and synthesized with sulfonate and carboxylate groups on the peptide scaffold. The GAG mimetic peptide nanofibers interact with bone morphogenetic protein-2 (BMP-2), which is a critical growth factor for osteogenic activity. The GAG mimicking ability of the peptide nanofibers and their interaction with BMP-2 promoted osteogenic activity and mineralization by osteoblastic cells. Alkaline phosphatase activity, Alizarin red staining and energy dispersive X-ray analysis spectroscopy indicated the efficacy of the peptide nanofibers in inducing mineralization. The multifunctional and bioactive microenvironment presented here provides osteoblastic cells with osteogenic stimuli similar to those observed in native bone tissue.