Browsing by Subject "Osteogenic differentiation"

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Open Access
Dentin phosphoprotein mimetic peptide nanofibers promote biomineralization
(WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim, 2019) Gülseren, Gülcihan; Tansik, Gülistan; Garifullin, Ruslan; Tekinay, Ayse B.; Güler, Mustafa O.
Dentin phosphoprotein (DPP) is a major component of the dentin matrix playing crucial role in hydroxyapatite deposition during bone mineralization, making it a prime candidate for the design of novel materials for bone and tooth regeneration. The bioactivity of DPP‐derived proteins is controlled by the phosphorylation and dephosphorylation of the serine residues. Here an enzyme‐responsive peptide nanofiber system inducing biomineralization is demonstrated. It closely emulates the structural and functional properties of DPP and facilitates apatite‐like mineral deposition. The DPP‐mimetic peptide molecules self‐assemble through dephosphorylation by alkaline phosphatase (ALP), an enzyme participating in tooth and bone matrix mineralization. Nanofiber network formation is also induced through addition of calcium ions. The gelation process following nanofiber formation produces a mineralized extracellular matrix like material, where scaffold properties and phosphate groups promote mineralization. It is demonstrated that the DPP‐mimetic peptide nanofiber networks can be used for apatite‐like mineral deposition for bone regeneration.
Open Access
Development of peptide based materials as a synthetic scaffold to mimic extracellular matrix
(2017-07) Sever, Melike
Biomaterials obtained through self-assembling process of peptide amphiphile (PA) molecules provide great potential to introduce new therapeutic approaches in regenerative medicine through mimicking the natural environments of different types of tissues. The ability of self-assembled PA nanofibers to mimic natural extracellular matrix (ECM) renders them attractive for regenerative medicine applications. The materials-cell interactions can be modulated through the surface modification of the materials such as introducing the bioactivity via short bioactive peptide sequences derived from natural ECM proteins, which regulate cell behavior through controlling of cellular activities such as proliferation and differentiation. Herein, I described my studies on the development of PA nanofibers in order to mimic natural ECM with differentiation and regeneration purposes. Heparan sulfate mimetic and laminin mimetic PA nanofibers were used as a potential therapeutic approach in Parkinson's disease (PD). These bioactive PA nanofibers were found to reduce the progressive cell loss in SH-SY5Y cells caused by 6-hydroxydopamine treatment in vitro, and improve neurochemical and behavioral consequences of Parkinsonism in rats and provide a promising new strategy for treatment of PD. These nanofibers also proved to be effective in enhancing the viability of Schwann cells and increase nerve growth factor (NGF) release from these cells in vitro. Since NGF has a crucial role in nerve injury repair and myelination in the regenerating nerve, the bioactive epitopes used in this study present also a promising approach as guidance cues for regenerating axons. Tenascin-C is another multifunctional ECM glycoprotein common in both nerve and bone tissue. By decorating peptide nanofibers with tenascin-C derived epitope and using in three-dimensional (3D) system, this tenascin-C mimetic 3D cell culture system was found to provide both the biochemical and physical aspects of the native environment of neural cells, thereby filling the gap between 2D cell culture models and in vivo environments and contributing to more tissue-like structure and more predictive approaches to organogenesis and tissue morphology. Within the scope of this thesis, tenascin-C mimetic nanofibers were also used for osteogenic differentiation of mesenchymal stem cells (MSCs). They were found to significantly enhance the attachment, proliferation, and osteogenic differentiation of MSCs even in the absence of any external bioactive factors and regardless of the suitable stiff mechanical properties normally required for osteogenic differentiation.
Open Access
A glycosaminoglycan mimetic peptide nanofiber gel as an osteoinductive scaffold
(Royal Society of Chemistry, 2016) Tansik, G.; Kilic, E.; Beter, M.; Demiralp, B.; K.Sendur, G.; Can, N.; Ozkan, H.; Ergul, E.; Güler, Mustafa O.; Tekinay, A. B.
Biomineralization of the extracellular matrix (ECM) plays a crucial role in bone formation. Functional and structural biomimetic native bone ECM components can therefore be used to change the fate of stem cells and induce bone regeneration and mineralization. Glycosaminoglycan (GAG) mimetic peptide nanofibers can interact with several growth factors. These nanostructures are capable of enhancing the osteogenic activity and mineral deposition of osteoblastic cells, which is indicative of their potential application in bone tissue regeneration. In this study, we investigated the potential of GAG-mimetic peptide nanofibers to promote the osteogenic differentiation of rat mesenchymal stem cells (rMSCs) in vitro and enhance the bone regeneration and biomineralization process in vivo in a rabbit tibial bone defect model. Alkaline phosphatase (ALP) activity and Alizarin red staining results suggested that osteogenic differentiation is enhanced when rMSCs are cultured on GAG-mimetic peptide nanofibers. Moreover, osteogenic marker genes were shown to be upregulated in the presence of the peptide nanofiber system. Histological and micro-computed tomography (Micro-CT) observations of regenerated bone defects in rabbit tibia bone also suggested that the injection of a GAG-mimetic nanofiber gel supports cortical bone deposition by enhancing the secretion of an inorganic mineral matrix. The volume of the repaired cortical bone was higher in GAG-PA gel injected animals. The overall results indicate that GAG-mimetic peptide nanofibers can be utilized effectively as a new bioactive platform for bone regeneration. © 2016 The Royal Society of Chemistry.
Open Access
Glycosaminoglycan-Mimetic Signals Direct the Osteo/Chondrogenic Differentiation of Mesenchymal Stem Cells in a Three-Dimensional Peptide Nanofiber Extracellular Matrix Mimetic Environment
(American Chemical Society, 2016-02) Arslan, E.; Güler, Mustafa O.; Tekinay, A. B.
Recent efforts in bioactive scaffold development focus strongly on the elucidation of complex cellular responses through the use of synthetic systems. Designing synthetic extracellular matrix (ECM) materials must be based on understanding of cellular behaviors upon interaction with natural and artificial scaffolds. Hence, due to their ability to mimic both the biochemical and mechanical properties of the native tissue environment, supramolecular assemblies of bioactive peptide nanostructures are especially promising for development of bioactive ECM-mimetic scaffolds. In this study, we used glycosaminoglycan (GAG) mimetic peptide nanofiber gel as a three-dimensional (3D) platform to investigate how cell lineage commitment is altered by external factors. We observed that amount of fetal bovine serum (FBS) presented in the cell media had synergistic effects on the ability of GAG-mimetic nanofiber gel to mediate the differentiation of mesenchymal stem cells into osteogenic and chondrogenic lineages. In particular, lower FBS concentration in the culture medium was observed to enhance osteogenic differentiation while higher amount FBS promotes chondrogenic differentiation in tandem with the effects of the GAG-mimetic 3D peptide nanofiber network, even in the absence of externally administered growth factors. We therefore demonstrate that mesenchymal stem cell differentiation can be specifically controlled by the combined influence of growth medium components and a 3D peptide nanofiber environment.
Open Access
Mineralized peptide nanofiber gels for enhanced osteogenic differentiation
(Wiley, 2018) Eren, E. D.; Tansik, G.; Tekinay, A. B.; Güler, Mustafa O.
Mineral deposition is observed in both bacterial and eukaryotic organisms through a broad range of mechanisms. Both organic and inorganic components play crucial roles in the formation of mineralized tissues, and acidic proteins are particularly important in this context owing to their ability to stimulate nucleation of minerals. Here, we present negatively-charged self-assembling peptide amphiphile molecules as a template to nucleate calcium phosphate mineralization in a bioactive scaffold environment. Acidic peptide molecules were shown to induce formation of hydroxyapatite like calcium phosphate mineralization, which was characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, X-ray diffractometry, oscillatory rheology and atomic force microscopy. The osteoblast-like cells were found to reveal enhanced osteogenic differentiation on pre-mineralized peptide nanofiber networks, suggesting that mineral deposition can be used as a means of enhancing the bioactivity of peptide-based scaffold systems.
Open Access
Nanomechanical characterization of osteogenic differentiation of mesenchymal stem cells on bioactive peptide nanofiber hydrogels
(Wiley-VCH Verlag, 2017-08) Topal, A. E.; Tansik, G.; Ozkan A.D.; Güler, Mustafa O.; Dana, A.; Tekinay, A. B.
Stem cell differentiation is known to be influenced by the mechanical properties of the surrounding extracellular matrix (ECM); however, little is known about the mechanical phenotypes of differentiating stem cells within the ECM. Here, this study uses osteoinductive, ECM-mimetic peptide nanofibers to investigate the changes in the mechanical properties of rat mesenchymal stem cells (rMSCs) during osteogenic differentiation. In addition, octafluorocyclobutane (C4F8)-coated atomic force microscopy (AFM) cantilevers are developed to minimize tip–sample adhesion during the nanomechanical characterization of rMSCs, and osteogenic differentiation is monitored through molecular analysis in conjunction with AFM measurements. rMSCs cultured on osteoinductive peptide nanofibers differentiate at substantially higher rates, form osteogenic cell clusters, deposit calcium to the surrounding matrix, and strikingly increase their Young's moduli throughout the osteogenic differentiation process compared to controls. These results show that the elasticity profiles of differentiating rMSCs may change significantly depending on environmental factors and especially the degree of biomineralization, and that the natural elasticity responses of cells cultured on scaffolds may be considerably different from those observed on non-bioactive surfaces. This is important for the identification of cell elasticity as a biophysical marker of osteogenic differentiation of MSCs, and indicates that biomineralization might have a predominant role on cell mechanics.
Open Access
Synthesis and characterization of nanosized calcium phosphates by flame spray pyrolysis, and their effect on osteogenic differentiation of stem cells
(Springer, 2015) Ataol, S.; Tezcaner, A.; Duygulu, O.; Keskin, D.; Machin, N. E.
The present study evaluates the synthesis of biocompatible osteoconductive and osteoinductive nano calcium phosphate (CaP) particles by industrially applied, aerosol-derived flame spray pyrolysis method for biomedical field. Calcium phosphate nanoparticles were produced in a range of calcium-to-phosphorus ratio, (1.20–2.19) in order to analyze the morphology and crystallinity changes, and to test the bioactivity of particles. The characterization results confirmed that nanometer-sized, spherical calcium phosphate particles were produced. The average primary particle size was determined as 23 nm by counting more than 500 particles in TEM pictures. XRD patterns, HRTEM, SAED, and SEM analyses revealed the amorphous nature of the as-prepared nano calcium phosphate particles at low Ca/P ratios. Increases in the specific surface area and crystallinity were observed with the increasing Ca/P ratio. TGA–DTA analysis showed that the thermally stable crystal phases formed after 700 °C. Cell culture studies were conducted with urine-derived stem cells that possess the characteristics of mesenchymal stem cells. Synthesized amorphous nanoparticles did not have cytotoxic effect at 5–50 μg/ml concentration range. Cells treated with the as-prepared nanoparticles had higher alkaline phosphatase (ALP) enzyme activity than control cells, indicating osteogenic differentiation of cells. A slight decrease in ALP activity of cells treated with two highest Ca:P ratios at 50 μg/ml concentration was observed at day 7. The findings suggest that calcium phosphate nanoparticles produced in this work have a potential to be used as biomaterials in biomedical applications. © 2015, Springer Science+Business Media Dordrecht.