Browsing by Subject "Angiogenesis"

Now showing 1 - 15 of 15

Open Access
15-Lipoxygenase-1 re-expression in colorectal cancer alters endothelial cell features through enhanced expression of TSP-1 and ICAM-1
(Elsevier, 2017-11) Tunçer, S.; Keşküş, A. G.; Çolakoğlu, M.; Çimen, I.; Yener, C.; Konu, Ö.; Banerjee, S.
15-lipoxygenase-1 (15-LOX-1) oxygenates linoleic acid to 13(S)-hydroxyoctadecadienoic acid (HODE). The enzyme is widely suppressed in different cancers and its re-expression has tumor suppressive effects. 15-LOX-1 has been shown to inhibit neoangiogenesis in colorectal cancer (CRC); in the present study we confirm this phenomenon and describe the mechanistic basis. We show that re-expression of 15-LOX-1 in CRC cell lines resulted in decreased transcriptional activity of HIF1α and reduced the expression and secretion of VEGF in both normoxic and hypoxic conditions. Conditioned medium (CM) was obtained from CRC or prostate cancer cell lines re-expressing 15-LOX-1 (15-LOX-1CM). 15-LOX-1CM treated aortic rings from 6-week old C57BL/6 mice showed significantly less vessel sprouting and more organized structure of vascular network. Human umbilical vein endothelial cells (HUVECs) incubated with 15-LOX-1CM showed reduced motility, enhanced expression of intercellular cell adhesion molecule (ICAM-1) and reduced tube formation but no change in proliferation or cell-cycle distribution. HUVECs incubated with 13(S)-HODE partially phenocopied the effects of 15-LOX-1CM, i.e., showed reduced motility and enhanced expression of ICAM-1, but did not reduce tube formation, implying the importance of additional factors. Therefore, a Proteome Profiler Angiogenesis Array was carried out, which showed that Thrombospondin-1 (TSP-1), a matrix glycoprotein known to strongly inhibit neovascularization, was expressed significantly more in HUVECs incubated with 15-LOX-1CM. TSP-1 blockage in HUVECs reduced the expression of ICAM-1 and enhanced cell motility, thereby providing a mechanism for reduced angiogenesis. The anti-angiogenic effects of 15-LOX-1 through enhanced expressions of ICAM-1 and TSP-1 are novel findings and should be explored further to develop therapeutic options.
Open Access
Angiogenic heparin-mimetic peptide nanofiber gel improves regenerative healing of acute wounds
(American Chemical Society, 2017) Uzunalli, G.; Mammadov R.; Yesildal, F.; Alhan, D.; Ozturk, S.; Ozgurtas, T.; Güler, Mustafa O.; Tekinay, A. B.
Wound repair in adult mammals typically ends with the formation of a scar, which prevents full restoration of the function of the healthy tissue, although most of the wounded skin heals. Rapid and functional recovery of major wound injuries requires therapeutic approaches that can enhance the healing process via overcoming mechanical and biochemical problems. In this study, we showed that self-assembled heparin-mimetic peptide nanofiber gel was an effective bioactive wound dressing for the rapid and functional repair of full-thickness excisional wounds in the rat model. The bioactive gel-treated wounds exhibited increased angiogenesis (p < 0.05), re-epithelization (p < 0.05), skin appendage formation, and granulation tissue organization (p < 0.05) compared to sucrose-treated samples. Increased blood vessel numbers in the gel-treated wounds on day 7 suggest that angiogenesis played a key role in improvement of tissue healing in bioactive gel-treated wounds. Overall, the angiogenic heparin-mimetic peptide nanofiber gel is a promising platform for enhancing the scar-free recovery of acute wounds.
Open Access
Angiogenic peptide nanofibers improve wound healing in STZ-induced diabetic rats
(American Chemical Society, 2016-06) Senturk, B.; Mercan, S.; Delibasi, T.; Güler, Mustafa O.; Tekinay, A. B.
Low expressions of angiogenic growth factors delay the healing of diabetic wounds by interfering with the process of blood vessel formation. Heparin mimetic peptide nanofibers can bind to and enhance production and activity of major angiogenic growth factors, including VEGF. In this study, we showed that heparin mimetic peptide nanofibers can serve as angiogenic scaffolds that allow slow release of growth factors and protect them from degradation, providing a new therapeutic way to accelerate healing of diabetic wounds. We treated wounds in STZ-induced diabetic rats with heparin mimetic peptide nanofibers and studied repair of full-thickness diabetic skin wounds. Wound recovery was quantified by analyses of re-epithelialization, granulation tissue formation and blood vessel density, as well as VEGF and inflammatory response measurements. Wound closure and granulation tissue formation were found to be significantly accelerated in heparin mimetic gel treated groups. In addition, blood vessel counts and the expressions of alpha smooth muscle actin and VEGF were significantly higher in bioactive gel treated animals. These results strongly suggest that angiogenic heparin mimetic nanofiber therapy can be used to support the impaired healing process in diabetic wounds.
Open Access
Aspartame induces angiogenesis in vitro and in vivo models
(SAGE Publications Ltd, 2015) Yesildal, F.; Aydin, F. N.; Deveci, S.; Tekin, S.; Aydin, I.; Mammadov R.; Fermanli, O.; Avcu, F.; Acikel, C. H.; Ozgurtas, T.
Angiogenesis is the process of generating new blood vessels from preexisting vessels and is considered essential in many pathological conditions. The purpose of the present study is to evaluate the effect of aspartame on angiogenesis in vivo chick chorioallantoic membrane (CAM) and wound-healing models as well as in vitro 2,3-bis-2H-tetrazolium-5-carboxanilide (XTT) and tube formation assays. In CAM assay, aspartame increased angiogenesis in a concentration-dependent manner. Compared with the control group, aspartame has significantly increased vessel proliferation (p < 0.001). In addition, in vivo rat model of skin wound-healing study showed that aspartame group had better healing than control group, and this was statistically significant at p < 0.05. There was a slight proliferative effect of aspartame on human umbilical vein endothelial cells on XTT assay in vitro, but it was not statistically significant; and there was no antiangiogenic effect of aspartame on tube formation assay in vitro. These results provide evidence that aspartame induces angiogenesis in vitro and in vivo; so regular use may have undesirable effect on susceptible cases. © The Author(s) 2015.
Open Access
Bioactive peptide nanofibers for tissue regeneration
(2016-01) Uzunallı, Gözde
Defects in the tissues or organs caused by trauma or diseases can have detrimental effects on all aspects of patients’ life quality. During the last three decades, considerable developments have been made in tissue engineering and regenerative medicine in order to find alternative treatment methods to recover tissue function after injury. These methods are based on the development of materials that are uniquely suited to the specific requirements of the tissue type and the repair process itself. Consequently, the implanted biomaterial must be compatible with biological systems and capable of delivering the signals necessary to facilitate tissue repair. In the present thesis, peptide amphiphile molecules were used to meet these requirements and develop next-generation biomaterials that are able to enhance the repair process while minimally affecting the integrity of surrounding tissues. Peptide amphiphiles are molecules that naturally self-assemble into nanofibrous hydrogel structures that closely emulate the composition of the extracellular matrix. As peptide amphiphiles contain amino acid sequences, bioactive signals can also be integrated into their structure to create a biocompatible environment and enhance the survival and proliferation of the resident cell population. In the scope of the present thesis, peptide amphiphile systems were utilized in three distinct applications. The first chapter covers the fundamentals of regenerative medicine and tissue engineering, the interactions between biomaterials and cells and extracellular materials, and the materials that are commonly used for these applications. The second chapter details the use of fibronectin- and laminin-derived peptide amphiphiles for the regeneration of corneal injuries. The third chapter investigates the ability of heparin-mimetic peptide hydrogels to facilitate the survival of pancreatic islets in vitro and demonstrates that islets transplanted in tandem with peptide gels trigger a local angiogenic response, decrease blood glucose levels and retain these functionalities even after 28 days of observation. The fourth chapter concerns the application of heparin-mimetic peptide amphiphile molecules for the recovery of acute wound injuries through the establishment of a well-ordered collagen matrix and the enhancement of the re-epithelialization process. Distinct peptide amphiphiles bearing bioactive signals conductive to tissue development were developed and utilized in all three studies, and the use of these materials has been demonstrated to serve as an adequate means of enhancing tissue repair.
Open Access
Design and application of peptide nanofibers for modulating angiogenesis
(2016-06) Şentürk, Berna
Angiogenesis is important in many diseases, such as diabetic wound healing, cancer and corneal neovascularization. Angiogenesis can be induced or inhibited by complex biological systems. Mimicking the complexity in natural systems requires smart supramolecular architectures with predictable properties and functions. Peptides are particularly attractive as molecular building blocks in the bottom-up fabrication of supramolecular structures based on self-assembly and have potential in many important applications in the fields of tissue engineering and regenerative medicine. Peptide-based biomaterials for angiogenesis are currently an intensely investigated topic in pathology and pharmacology related studies. Peptide-based biomaterials can be utilized for the treatment of angiogenesis-deficient complications by mimicking natural glycosaminoglycans. Diabetic ulcerations are largely caused by the lack of vascularization during the wound healing process, and angiogenesis-promoting peptide nanofibers are highly promising for the treatment of these injuries. In addition to the induction of angiogenesis, peptide-based systems can also be used to prevent it in locations where it is detrimental to health. In particular, peptide amphiphiles with anti-angiogenic properties may enable the treatment severe eye diseases, including corneal neovascularization. This thesis describes nature-inspired combinatorial methods for designing peptide nanostructures that display angiogenic and anti-angiogenic functional moieties. The importance of multivalent peptide-constructs for high affinity binding and efficiency will be highlighted. Furthermore, in vitro and in vivo efficiency of angiogenesis related therapeutic agents is reported. Another type of products that will be discussed is black silicon surface that inspired also from nature, utilized for anti-bacterial and unique topographical characteristic.
Open Access
Diet-induced changes in mouse cells in vitro and in vivo zebrafish models of angiogenesis
(2024-01) Yıldız, Selvin
Cardiovascular disorders rank as the primary cause of global mortality. Being overweight or obese impacts the pathogenesis of cardiovascular disease, resulting in an imbalance in endothelial function, cell growth, and inflammatory activation. Disruption of these factors resulting from endothelial cell dysfunction serves as both an outcome and a catalyst for vascular disease processes. Endothelial cells (ECs) are a natural barrier between circulating blood and vessel components. They also play critical roles in multiple physiological and pathophysiological processes, such as angiogenesis, vascular permeability, and inflammation. Amelioration of endothelial dysfunction may be attained by weight loss; however, complementary in vitro and in vivo studies are needed to establish the effects of weight loss on endothelial function and angiogenesis. This study developed an in vitro model to understand better the diet-induced changes in angiogenesis for mouse endothelial cells. In addition, a novel in vivo model of diet-induced vascular changes and its potential reversal with a return to regular diet in a zebrafish model was also studied. In vitro studies showed that a serum from mice fed a high-fat diet (HFD) might lead to proliferation of endothelial cells, yet weight loss did not compensate for prior stress induced by HFD. In vivo, studies in adult zebrafish showed that egg yolk-based high-fat diet might affect cytological architecture in the adult fish liver. Switching to a normal diet could effectively reverse these changes. Moreover, a caudal fin inter-ray vascularization assay was developed and used to test whether vessel sprouting was affected by different diets. Overfeeding resulted in a higher number of vessels, yet future studies with higher sample sizes are needed. Similarly, the expressions of several angiogenesis-related genes, which were quantified using cDNAs from the whole larvae and adult caudal fin treated with different diets, showed significant changes in vcam in larvae and cdh5 in adult fin by diet. However, further experiments are needed due to high individual variability and low sample size. The findings herein show that in vitro mouse endothelial cells and zebrafish larvae and adults could be used as valuable models for studies involving reversal/weight loss of high fat or overfeeding dietary regimes. Furthermore, the caudal fin vascularization assay in Tg(fli1:eGFP) Casper fish could be a promising preclinical model for testing the effects of different diets on angiogenesis and endothelial dysfunction.
Open Access
Electrostatic effects on the self-assembly mechanism of peptide amphiphiles
(2010) Toksöz, Sıla
Self-assembling peptide amphiphiles, synthesized through solid phase peptide synthesis – a bottom-up approach, have been used with various tissue engineering purposes. Peptide amphiphile molecules self-assemble into nanofibers, which form three dimensional networks mimicking the extracellular matrix. Electrostatic interactions affect the formation of nanofibers. The effect of charged groups on the peptides on nanofiber formation were studied in this work. Neutralization of the charged groups by pH change, electrolyte addition or addition of oppositely charged biomacromolecules triggered the aggregation of the peptides. To understand the controlled formation of the gels composed of peptide nanofibers better can help the researchers develop bioactive collagen mimetic nanofibers for tissue engineering studies and use them in angiogenesis. Results obtained by Fourier Transform Infrared Spectroscopy (FT-IR), Circular Dichroism (CD), Rheology, pH titration, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM); as well as the potential of using the peptide amphiphile molecules to promote angiogenesis, are described.
Open Access
Heparin mimetic peptide nanofiber gel promotes regeneration of full thickness burn injury
(Elsevier Ltd, 2017) Yergoz, F.; Hastar, N.; Cimenci, C. E.; Ozkan, A. D.; Güler, Mustafa O.; Tekinay, A. B.; Tekinay, T.; Güler, Mustafa O.
Burn injuries are one of the most common types of trauma worldwide, and their unique physiology requires the development of specialized therapeutic materials for their treatment. Here, we report the use of synthetic, functional and biodegradable peptide nanofiber gels for the improved healing of burn wounds to alleviate the progressive loss of tissue function at the post-burn wound site. These bioactive nanofiber gels form scaffolds that recapitulate the structure and function of the native extracellular matrix through signaling peptide epitopes, which can trigger angiogenesis through their affinity to basic growth factors. In this study, the angiogenesis-promoting properties of the bioactive scaffolds were utilized for the treatment of a thermal burn model. Following the excision of necrotic tissue, bioactive gels and control solutions were applied topically onto the wound area. The wound healing process was evaluated at 7, 14 and 21 days following injury through histological observations, immunostaining and marker RNA/protein analysis. Bioactive peptide nanofiber-treated burn wounds formed well-organized and collagen-rich granulation tissue layers, produced a greater density of newly formed blood vessels, and exhibited increased re-epithelialization and skin appendage development with minimal crust formation, while non-bioactive peptide nanofibers and the commercial wound dressing 3M™ Tegaderm™ did not exhibit significant efficiency over sucrose controls. Overall, the heparin-mimetic peptide nanofiber gels increased the rate of repair of burn injuries and can be used as an effective means of facilitating wound healing.
Open Access
HER2 and proliferation of wound-induced breast carcinoma
(The Lancet Publishing, 2003-11-01) Tez, M.; Göçmen, E.; Özçelik, T.
Open Access
Identification of novel neutralizing single-chain antibodies against vascular endothelial growth factor receptor 2
(2011) Erdag, B.; Koray Balcioglu, B.; Ozdemir Bahadir, A.; Serhatli, M.; Kacar O.; Bahar, A.; Seker, U.O.S.; Akgun, E.; Ozkan, A.; Kilic, T.; Tamerler, C.; Baysal, K.
Human vascular endothelial growth factor (VEGF) and its receptor (VEGFR-2/kinase domain receptor [KDR]) play a crucial role in angiogenesis, which makes the VEGFR-2 signaling pathway a major target for therapeutic applications. In this study, a single-chain antibody phage display library was constructed from spleen cells of mice immunized with recombinant human soluble extracellular VEGFR-2/KDR consisting of all seven extracellular domains (sKDR D1-7) to obtain antibodies that block VEGF binding to VEGFR-2. Two specific single-chain antibodies (KDR1.3 and KDR2.6) that recognized human VEGFR-2 were selected; diversity analysis of the clones was performed by BstNI fingerprinting and nucleotide sequencing. The single-chain variable fragments (scFvs) were expressed in soluble form and specificity of interactions between affinity purified scFvs and VEGFR-2 was confirmed by ELISA. Binding of the recombinant antibodies for VEGFR-2 receptors was investigated by surface plasmon resonance spectroscopy. In vitro cell culture assays showed that KDR1.3 and KDR2.6 scFvs significantly suppressed the mitogenic response of human umbilical vein endothelial cells to recombinant human VEGF 165 in a dose-dependent manner, and reduced VEGF-dependent cell proliferation by 60% and 40%, respectively. In vivo analysis of these recombinant antibodies in a rat cornea angiogenesis model revealed that both antibodies suppressed the development of new corneal vessels (p < 0.05). Overall, in vitro and in vivo results disclose strong interactions of KDR1.3 and KDR2.6 scFvs with VEGFR-2. These findings indicate that KDR1.3 and KDR2.6 scFvs are promising antiangiogenic therapeutic agents. © 2011 International Union of Biochemistry and Molecular Biology, Inc.
Open Access
Improving pancreatic islet in vitro functionality and transplantation efficiency by using heparin mimetic peptide nanofiber gels
(Elsevier, 2015) Uzunalli, Gözde; Tumtas, Yasin; Delibasi, T.; Yasa, Oncay; Mercan, S.; Güler, Mustafa O.; Tekinay, Ayse B.
Pancreatic islet transplantation is a promising treatment for type 1 diabetes. However, viability and functionality of the islets after transplantation are limited due to loss of integrity and destruction of blood vessel networks. Thus, it is important to provide a proper mechanically and biologically supportive environment for enhancing both in vitro islet culture and transplantation efficiency. Here, we demonstrate that heparin mimetic peptide amphiphile (HM-PA) nanofibrous network is a promising platform for these purposes. The islets cultured with peptide nanofiber gel containing growth factors exhibited a similar glucose stimulation index as that of the freshly isolated islets even after 7 days. After transplantation of islets to STZ-induced diabetic rats, 28 day-long monitoring displayed that islets that were transplanted in HM-PA nanofiber gels maintained better blood glucose levels at normal levels compared to the only islet transplantation group. In addition, intraperitoneal glucose tolerance test revealed that animals that were transplanted with islets within peptide gels showed a similar pattern with the healthy control group. Histological assessment showed that islets transplanted within peptide nanofiber gels demonstrated better islet integrity due to increased blood vessel density. This work demonstrates that using the HM-PA nanofiber gel platform enhances the islets function and islet transplantation efficiency both in vitro and in vivo.
Open Access
Inhibition of VEGF mediated corneal neovascularization by anti-angiogenic peptide nanofibers
(Elsevier, 2016-11) Senturk, B.; Cubuk, M. O.; Ozmen, M. C.; Aydin B.; Güler, Mustafa O.; Tekinay, A. B.
Atypical angiogenesis is one of the major symptoms of severe eye diseases, including corneal neovascularization, and the complex nature of abnormal vascularization requires targeted methods with high biocompatibility. The targeting of VEGF is the most common approach for preventing angiogenesis, and the LPPR peptide sequence is known to strongly inhibit VEGF activity by binding to the VEGF receptor neuropilin-1. Here, the LPPR epitope is presented on a peptide amphiphile nanofiber system to benefit from multivalency and increase the anti-angiogenic function of the epitope. Peptide amphiphile nanofibers are especially useful for ocular delivery applications due to their ability to remain on the site of interest for extended periods of time, facilitating the long-term presentation of bioactive sequences. Consequently, the LPPR sequence was integrated into a self-assembled peptide amphiphile network to increase its efficiency in the prevention of neovascularization. Anti-angiogenic effects of the peptide nanofibers were investigated by using both in vitro and in vivo models. LPPR-PA nanofibers inhibited endothelial cell proliferation, tube formation, and migration to a greater extent than the soluble LPPR peptide in vitro. In addition, the LPPR-PA nanofiber system led to the prevention of vascular maturation and the regression of angiogenesis in a suture-induced corneal angiogenesis model. These results show that the anti-angiogenic activity exhibited by LPPR peptide nanofibers may be utilized as a promising approach for the treatment of corneal angiogenesis.
Open Access
Mechanistic pathways of malignancy in breast cancer stem cells
(Frontiers Media S.A., 2020-04-30) Yousefnia, S.; Forootan, F. S.; Forootan, S. S.; Esfahani, M. H. N.; Güre, Ali Osmay
Breast cancer stem cells (BCSCs) are the minor population of breast cancer (BC) cells that exhibit several phenotypes such as migration, invasion, self-renewal, and chemotherapy as well as radiotherapy resistance. Recently, BCSCs have been more considerable due to their capacity for recurrence of tumors after treatment. Recognition of signaling pathways and molecular mechanisms involved in stemness phenotypes of BCSCs could be effective for discovering novel treatment strategies to target BCSCs. This review introduces BCSC markers, their roles in stemness phenotypes, and the dysregulated signaling pathways involved in BCSCs such as mitogen-activated protein (MAP) kinase, PI3K/Akt/nuclear factor kappa B (NFκB), TGF-β, hedgehog (Hh), Notch, Wnt/β-catenin, and Hippo pathway. In addition, this review presents recently discovered molecular mechanisms implicated in chemotherapy and radiotherapy resistance, migration, metastasis, and angiogenesis of BCSCs. Finally, we reviewed the role of microRNAs (miRNAs) in BCSCs as well as several other therapeutic strategies such as herbal medicine, biological agents, anti-inflammatory drugs, monoclonal antibodies, nanoparticles, and microRNAs, which have been more considerable in the last decades.
Open Access
Three dimensional glycosaminoglycan mimetic peptide amphiphile hydrogels for regenerative medicine applications
(2015-05) Tümtaş, Yasin
Defects and impairments of tissues or organs affect millions of people, resulting in considerable losses in workforce and life quality. The treatment of major tissue injuries requires the development of advanced medical techniques that enhance the natural repair processes of the human body. Novel biomaterials can modulate the repair of organs and tissues by providing a suitable environment for the recruitment, proliferation and differentiation of stem and progenitor cells, allowing the recovery of degenerated or otherwise nonfunctional tissues. Peptide amphiphiles (PAs) serve as model biomaterials due to their capacity for self-assembly, which allows peptide monomers to form complex networks that approximate the structure and function of the natural extracellular matrix. Peptide networks can be further modified by the attachment of various epitopes and functional groups, allowing these materials to present bioactive signals to surrounding cells. Glycosaminoglycans (GAGs) are negatively charged, unbranched polysaccharides that constitute a substantial part of the ECM in various tissues and play an important role in maintaining tissue integrity. Therefore, mimicking GAGs presents a suitable means for modulating cell behavior and especially lineage commitment in stem cells. In this work, I describe the design and synthesis of several bioactive, three dimensional (3D) GAG-mimetic peptide amphiphile hydrogels for in vitro stem cell differentiation and in vivo pancreatic islet transplantation. In Chapter 1, I detail the extracellular environment of tissues and the importance of GAGs in maintaining cell and tissue function. In Chapter 2, I describe the in vitro experiments involving the effects of sulfonation and the presence of glucose units on the differentiation of mesenchymal stem cells. In Chapter 3, I utilize a heparin-mimetic PA to increase the survival of pancreatic islets transplanted into the rat omentum, and demonstrate that increased angiogenesis results in enhanced survival. Lastly, in Chapter 4, I summarize my results and describe the course of future experiments for the artificial regeneration of tissues through peptide amphiphile networks.