Browsing by Subject "Laminin"
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Item Open Access A hybrid nanofiber matrix to control the survival and maturation of brain neurons(Elsevier BV, 2012) Sur, S.; Pashuck, E. T.; Güler, Mustafa O.; Ito, M.; Stupp, S. I.; Launey, T.Scaffold design plays a crucial role in developing graft-based regenerative strategies, especially when intended to be used in a highly ordered nerve tissue. Here we describe a hybrid matrix approach, which combines the structural properties of collagen (type I) with the epitope-presenting ability of peptide amphiphile (PA) nanofibers. Self-assembly of PA and collagen molecules results in a nanofibrous scaffold with homogeneous fiber diameter of 20-30 nm, where the number of laminin epitopes IKVAV and YIGSR can be varied by changing the PA concentrations over a broad range of 0.125-2 mg/ml. Granule cells (GC) and Purkinje cells (PC), two major neuronal subtypes of cerebellar cortex, demonstrate distinct response to this change of epitope concentration. On IKVAV hybrid constructs, GC density increases three-fold compared with the control collagen substrate at a PA concentration of ≥0.25 mg/ml, while PC density reaches a maximum (five-fold vs. control) at 0.25 mg/ml of PA and rapidly decreases at higher PA concentrations. In addition, adjustment of the epitope number allowed us to achieve fine control over PC dendrite and axon growth. Due to the ability to modulate neuron survival and maturation by easy manipulation of epitope density, our design offers a versatile test bed to study the extracellular matrix (ECM) contribution in neuron development and the design of optimal neuronal scaffold biomaterials. © 2011 Elsevier Ltd.Item Open Access Investigation of spontaneous differentiation of neural stem cells on synthetic scaffolds(Bilkent University, 2017-08) Uyan, İdilDespite the increasing incidents of brain injuries and neurodegenerative diseases, a definitive clinical therapy for these conditions has not been found yet. Nervous system injuries result in loss of neural cells, causing loss of function in the neural circuitry. As mature neurons do not divide, it is not possible to tolerate the loss of neurons by the production of new ones. In the central nervous system, even though neural stem cells are present, their number and regenerative capacity are very low. In addition, inhibitory molecules are released at the degeneration site which hinders reconnection of the remaining cells. As the damage is due to the loss of neurons, cell therapy is considered as a promising option. Neural stem cells are capable of differentiating into the three major cell types in the central nervous system: neurons, astrocytes, and oligodendrocytes. However, due to low rate of survival of the transplanted cells, there is still a need for a cell vehicle system to promote their survival, adhesion, migration, and differentiation. On the other hand, use of biological molecules such as growth factors or extracellular matrix proteins as vehicle systems should be minimized due to the immunological risks. Nanotechnological approaches serve as a great opportunity to mimic the native environment of the cells. Peptide amphiphiles (PAs) are self-assembling molecules that provide precise control over their secondary structure and the amino acid sequence, which can mimic proteins and show hydrogel properties. In this thesis, self-assembling PA scaffolds that mimic laminin, heparan sulfate and cadherin, which are key players in nervous system regeneration, have been investigated as cell delivery vehicles. Neurospheres are great models for studying the behavior of neural stem cells within a heterogeneous 3-dimensional cell population. Migration and differentiation behavior of neurospheres were investigated on laminin (LN), heparan sulfate (GAG), and cadherin-mimetic (HAV) PA nanofiber scaffolds. The results indicated that LN and GAG mimicking PA scaffolds cooperatively enhanced the migration of neurospheres, whereas cadherin mimetic PA scaffolds were individually sufficient to promote their migration. Also, a fine neural network was observed to be established on HAV-PA. These scaffolds hold high potential to be used as cell delivery vehicles.Item Open Access Investigation of the effects of bioactive peptide nanofibers on acute muscle injury regeneration(Bilkent University, 2016-10) Eren Çimenci, ÇağlaSkeletal muscle constitutes a large part of the human body. It is a hierarchically organized heterogeneous tissue and is composed of muscle fiber bundles, muscle fibers, myofibrils and myofilaments. Since muscle cells are terminally differentiated, they have limited capacity to renew themselves. Only new cells can fuse with muscle fibers and increase the size and volume of skeletal muscle. Myosatellite cells or satellite cells are small, mononuclear progenitor cells with virtually no cytoplasm. They are located in between the sarcolemma and basement membrane of terminally-differentiated muscle fibers. Satellite cells are precursors to skeletal muscle cells, and are able to give rise to satellite cells or differentiated skeletal muscle cells. They are normally found in silent state in adult muscle, but act as a reserve cell population that is able to proliferate in response to injury and give rise to regenerated muscle and to more satellite cells. Formation of the new muscular tissue is called myogenesis. During this event, satellite cells differentiate into myoblasts, and then myoblasts fuse with each other in order to form myofibers. There are many genes that regulate the myogenesis process and each of them is activated in a different step of myogenesis. Increased or decreased levels of gene expression determine the differentiation capacity. Peptide nanofibers are supramolecular structures formed via self-assembly and they are promising molecules in regenerative medicine and tissue engineering. Peptide-based molecules for tissue regeneration is a widely studied area and currently used in the treatment-investigation of many different tissues such as bone, cartilage, skin and nerve. Since laminin is one of the most abundant proteins found in the basal membrane of the skeletal muscle; in this thesis, we designed and synthesized a laminin-mimetic bioactive (LM/E-PA) molecule functionalized with bioactive groups for mimicking laminin activities and capable of accelerating satellite cell activation. Our research group had previously shown that LM/E-PA containing nanofibers can support muscle differentiation in vitro. In this thesis, the clinical relevance was demonstrated further by assessing laminin-mimetic bioactive scaffold in acute muscle injury in an in vivo rat model. Our findings revealed that this scaffold system significantly promotes satellite cell activation in skeletal muscle and accelerates regeneration following acute muscle injury. In addition, our findings show that the regeneration capacity of the skeletal muscle was increased and consequently regeneration time was reduced. This study is one of the first examples of molecular level and tissue level regeneration of skeletal muscle by using bioactive peptide nanofibers following acute muscle injury, and shows that laminin mimetic nanofiber system is a promising material for development of new therapeutic curatives for acute skeletal muscle injuries.Item Open Access Laminin mimetic peptide nanofibers regenerate acute muscle defect(Acta Materialia Inc, 2017) Cimenci, C. E.; Uzunalli, G.; Uysal, O.; Yergoz, F.; Umay, E. K.; Güler, Mustafa O.; Tekinay, A. B.Skeletal muscle cells are terminally differentiated and require the activation of muscle progenitor (satellite) cells for their regeneration. There is a clinical need for faster and more efficient treatment methods for acute muscle injuries, and the stimulation of satellite cell proliferation is promising in this context. In this study, we designed and synthesized a laminin-mimetic bioactive peptide (LM/E-PA) system that is capable of accelerating satellite cell activation by emulating the structure and function of laminin, a major protein of the basal membrane of the skeletal muscle. The LM/E-PA nanofibers enhance myogenic differentiation in vitro and the clinical relevance of the laminin-mimetic bioactive scaffold system was demonstrated further by assessing its effect on the regeneration of acute muscle injury in a rat model. Laminin mimetic peptide nanofibers significantly promoted satellite cell activation in skeletal muscle and accelerated myofibrillar regeneration following acute muscle injury. In addition, the LM/E-PA scaffold treatment significantly reduced the time required for the structural and functional repair of skeletal muscle. This study represents one of the first examples of molecular- and tissue-level regeneration of skeletal muscle facilitated by bioactive peptide nanofibers following acute muscle injury. Significance Statement Sports, heavy lifting and other strength-intensive tasks are ubiquitous in modern life and likely to cause acute skeletal muscle injury. Speeding up regeneration of skeletal muscle injuries would not only shorten the duration of recovery for the patient, but also support the general health and functionality of the repaired muscle tissue. In this work, we designed and synthesized a laminin-mimetic nanosystem to enhance muscle regeneration. We tested its activity in a rat tibialis anterior muscle by injecting the bioactive nanosystem. The evaluation of the regeneration and differentiation capacity of skeletal muscle suggested that the laminin-mimetic nanosystem enhances skeletal muscle regeneration and provides a suitable platform that is highly promising for the regeneration of acute muscle injuries. This work demonstrates for the first time that laminin-mimetic self-assembled peptide nanosystems facilitate myogenic differentiation in vivo without the need for additional treatment.Item Open Access Neuroactive peptide nanofibers for regeneration of spinal cord after injury(Wiley-VCH Verlag GmbH & Co. KGaA, 2020-10-11) Sever-Bahçekapılı, Melike; Yılmaz, Canelif; Demirel, A.; Kilinc, M. C.; Dogan, I.; Caglar, Y. S.; Guler, M. O.; Tekinay, Ayşe BegümThe highly complex nature of spinal cord injuries (SCIs) requires design of novel biomaterials that can stimulate cellular regeneration and functional recovery. Promising SCI treatments use biomaterial scaffolds, which provide bioactive cues to the cells in order to trigger neural regeneration in the spinal cord. In this work, the use of peptide nanofibers is demonstrated, presenting protein binding and cellular adhesion epitopes in a rat model of SCI. The self-assembling peptide molecules are designed to form nanofibers, which display heparan sulfate mimetic and laminin mimetic epitopes to the cells in the spinal cord. These neuroactive nanofibers are found to support adhesion and viability of dorsal root ganglion neurons as well as neurite outgrowth in vitro and enhance tissue integrity after 6 weeks of injury in vivo. Treatment with the peptide nanofiber scaffolds also show significant behavioral improvement. These results demonstrate that it is possible to facilitate regeneration especially in the white matter of the spinal cord, which is usually damaged during the accidents using bioactive 3D nanostructures displaying high densities of laminin and heparan sulfate-mimetic epitopes on their surfaces.Item Open Access Three-Dimensional Laminin Mimetic Peptide Nanofiber Gels for In Vitro Neural Differentiation(Wiley-VCH Verlag, 2017) Gunay, Gokhan; Sever, Melike; Tekinay, Ayse B.; Güler, Mustafa O.The extracellular matrix (ECM) provides biochemical signals and structural support for cells, and its functional imitation is a fundamental aspect of biomaterial design for regenerative medicine applications. The stimulation of neural differentiation by a laminin protein-derived epitope in two-dimensional (2D) and three-dimensional (3D) environments is investigated. The 3D gel system is found to be superior to its 2D counterpart for the induction of neural differentiation, even in the absence of a crucial biological inducer in nerve growth factor (NGF). In addition, cells cultured in 3D gels exhibits a spherical morphology that is consistent with their form under in vivo conditions. Overall, the present study underlines the impact of bioactivity, dimension, and NGF addition, as well as the cooperative effects thereof, on the neural differentiation of PC-12 cells. These results underline the significance of 3D culture systems in the development of scaffolds that closely replicate in vivo environments for the formation of cellular organoid models in vitro. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim