Browsing by Subject "Stem cells."

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Open Access
Characterization of chemosensitivity profiles of breast cancer cell lınes, with and without stem cell like features = Kök-hücre özelliği olan ve olmayan meme kanseri hücre hatlarının ilaç hassasiyet profillerinin tanımlanması
(2014) Akbar, Muhammad Waqas
Breast cancer is the second most common cause of death worldwide from cancer due to complications with its diagnosis and resistance to therapy. Recent studies have shown that breast tumors when compared with other solid tumors also contain a subpopulation termed as cancer stem cells (CSCs). CSCs are hard to kill due to their therapy resistant capacities. These unharmed cells then result into relapse of tumor after treatment. Some established breast cancer cell lines also behave in similar fashion to CSCs in overall manner thus termed as CSC like cell lines. This study primarily focuses on characterizing CSC like cell lines from non CSC like cell lines based upon their gene expression and prediction of drugs which can target these groups separately. In this study two databases, Cancer Cell Line Encyclopedia (CCLE) and Cancer Genome Project (CGP), were used which contain gene expression data and drugs cytotoxicity data for most of the established cancer cell lines. Breast cancer cell lines gene expression data was used to predict two gene lists which can separate breast cancer cell lines into CSC like and non CSC like cell lines by in silico analysis. These gene lists were named as Patentable and Non Patentable. Additionally four drugs were predicted which can target CSC like group (Midostaurin and Elesclomol) and non CSC like group (Panobinostat and Lapatinib) separately. Later these findings were validated in vitro. Non Patentable gene list could not be validated due to low concordance with microarray data. On the other hand, Patentable gene list was validated and was found concordant with microarray data. Out of four selected drugs, Panobinostat and Lapatinib showed increased toxicity to non CSC like cell lines while only Midostaurin showed toxicity to CSC like cell lines. To investigate further that cell lines were grown in 3D cell culture conditions, to increase their stem cell like properties (stemness). But only one cell line MDA-MB-157 which was found as CSC like, showed expected behavior. Additionally this cell line increased resistance to Lapatinib and Panobinostat and became more sensitive to Midostaurin. Correlation analysis showed some genes as potential biomarkers for selected drugs. In conclusion, in this study various genes are proposed to differentiate CSC like cell lines from non CSC like cell lines. And Midostaurin can be potential drug to treat CSC like cells while Lapatinib and Panobinostat showed increased activity against non CSC like cell lines.
Open Access
Genetic and epigenetic effect of estrogen on mesenchymal stem cell maintenance and differentiation
(2013) Bitirim, Ceylan Verda
Mesenchymal stem cells (MSCs) have the potential to differentiate into multiple cell types and immune privileged characteristics. These features make MSCs a hope in tissue engineering and cell based treatment applications. Tremendous amount of studies were carried out in order to produce an ideal biomaterial as a scaffold for cell transplantation. In recent studies, carbon nanotubes (CNT) were identified as a novel scaffold array due to their unique physical, chemical and electrical properties among the other biomaterials.The effect of estrogen hormone on the regulation of MSC maintenance, proliferation and differentiation was reported. However, its role in maintenance of MSCs on scaffold materials such as CNTs and the genetic and epigenetic regulation of MSC differentiation have not fully been elucidated. Therefore our aim was to examine the possible role of estrogen in the MSCs’ maintenance seeded on CNT surfaces and genetic and epigenetic regulation of the key transcription factors involved in adipogenic, osteogenic and chondrogenic differentiaton of MSCs. Our results revealed the enhanced effect of estrogen on the viability of MCSs which were seeded and incubated on multiwalled carbon nanotubes (MWCNT). In addition we demonstrated that passaging causes decrease of cell viability and the number of attached cells on CNT materials. We have also shown the effect of estrogen on the epigenetic and genetic regulation of MSC differentiation. Estrogen treatment decreased the expression of major adipogenic transcription factors; C/EBPα, FABP4, PPARγ, Adipsin and increased key osteogenic transcription factor RUNX2 in MSCs from both normal female and ovariectomized rats, suggesting inhibitory and stimulatory effect of estrogen on adipogenesis and osteogenesis respectively. We have also shown that the subcellular localization of PPARγ and ETS1 is changed in response to estrogen deficiency. Among modified histones, we found that H3K27me2, H3K27me3 and H3K36me2 protein levels were reduced after estrogen treatment both in female and ovariectomized animals. In addition, ChIP analysis showed that estrogen treatment caused an increase in H3K27me2, H3K27me3 and ERα levels at the promoters of C/EBPα, FABP4, PPARγ, Adipsin and RUNX2. Bisulfite sequencing analysis revealed that in the absence of estrogen, DNA hypermethylation was established in C/EBPα and PPARγ promoters whereas in ERα promoters CpG hypomethylation was observed after estrogen treatment. In conclusion, estrogen causes epigenetic and genetic changes in maintenace and differentiation of MSCs. Understanding the effect of estrogen on the genetic and epigenetic regulation of the major transcription factors may lead to clues for new treatment in chronic diseases such as obesity, osteoporosis and ostearthiritis.
Open Access
Role of environmental factors in mesenchymal stem cell biology
(2009) Gültekin, Sinan
Mesenchymal Stem Cells (MSCs) have the abilities of self-renewal and differentiation into fat, bone, cartilage, and muscle tissues. Besides intrinsic mechanisms that control the fate of the MSCs, extrinsic physiological factors also play role in this decision. Therefore, our aim is to explore the effects of possible environmental factors, involved in MSC maintenance by using rat MSCs as a model. We studied the effects of hypoxia and estrogen on growth regulation and cellular proliferation in MSCs. MSCs cells exhibited high colony number in hypoxic conditions and the expansion of MSCs was increased addition of the estrogen. In addition, estrogen prevents apoptosis, under hypoxic condition. The effects of estrogen on the expression levels of Notch genes (Notch1, Notch2, Notch3 and Notch4) were also investigated. In order to understand the possible mechanism of estrogen response, an experimental and in silico approach are used. The expression levels of Notch1 and Notch 3 were decreased treatment and the expression level of Notch 4 was increased upon estrogen treatment. In addition, bioinformatics analysis showed that, estrogen upregulates ERG family transcription factors, ELF family transcription factors, HOXL4 family transcription factors, KLF family transcription factors and transcription factor SOX3, which bind to Notch 1 transcriptional regulatory region, implying indirect effects of estrogen on Notch 1 expression. Twenty biomaterials were also investigated in order to assess whether they provide an appropriate environment for MSCs expansion. It was found that eight of the biomaterials out of twenty designated as, CA-1, CA-2, CA-3, CI-K, CI-A, CIII-1, CIII-2 and CIII-3, were appropriate candidates to expand MSCs. The combination polymers designated as HPMA/PEG provided appropriate conditions when prepared in the proportion of 1:0 (CA-1), 1:1 (CA-2) and 2:1 (CA-3). The appropriate proportion of polymers designated as HEMA/PEG/HPC was 2:1:1(CIII-1), 3:0:1 (CIII-2) and 1:1:0 (CIII-5).
Open Access
Role of estrogen on the maintenance and homing capacity of bone marrow derived rat mesenchymal stem cells
(2011) Ayaloğlu Bütün, Fatma
Mesenchymal Stem Cells (MSCs) can self renew and differentiate into different cell types like, adipocytes, osteoblasts, chondrocytes, neurons, hepatocytes and endothelial cells. Their ability to differentiate into wide variety of cell types, nonimmunogenic characteristics, along with homing capacity to injured tissue and the absence of any ethical issue related to their uses, make MSCs important in regenerative medicine and tissue engineering. Their ability to migrate to the site of injury raises the opportunity of these stem cells to be considered also as in vivo delivery agents. However, one major obstacle in using MSCs in cell based therapies is their limited numbers. Estrogen is known to have role in growth, proliferation and apoptosis. Therefore our aim was to study the possible role and mechanism of estrogen in their maintenance and their homing capacity. We used MSCs derived from female and ovariectomized female rat bone marrow in our research. Our results revealed that estrogen treatment increased the number of colonies and the number of cells constituting a colony. Estrogen decreased the differentiation capacity of MSCs to the adipogenic lineages as shown by reduced of Oil Red O staining Estrogen also affected MSCs’ homing capacity. Estrogen treatment resulted in the migration of increased number of DiI labeled MSCs to the site of injury after partial hepatectomy (PH) compared to that of untreated MSCs. Furthermore, estrogen treatment decreased the rate of apoptosis. Our data showed that estrogen regulates apoptosis through Bcl-2 family of genes in MSCs. This regulation was at the protein level but not at the transcript level. Estrogen addition increased the expression of anti-apoptotic members of the Bcl-2 family of proteins, Bcl-2 and Bcl-xL. The decrease in the apoptosis was not observed when Bcl-xL and Bcl-2 genes were knocked down. The silencing histone code H3K27me3 was also decreased in estrogen treated MSCs, suggesting an epigenetic regulation of MSCs upon estrogen treatment. Altogether our results show that estrogen increased the number of functional MSCs, decreased spontaneous apoptosis in these cells, and improved the homing capacity of rat bone marrow derived MSCs. Therefore, estrogen treatment of MSCs may offer new opportunities for the therapeutic actions of these cells.
Open Access
Small functional groups presented on peptide nanofibers for determining fate of rat mesenchymal stem cells
(2014) Yaşa, Öncay
Glycosaminoglycans (GAGs) are negatively-charged, unbranched polysaccharides that play important roles in various biological processes and are vital for the regeneration of damaged tissues. Like other natural extracellular matrix components, glycosaminoglycans and proteoglycans show considerable variation in local concentration and chemical composition depending on tissue type. They are found in various connective tissues, including bone, cartilage and fat, and display strong water-binding capacity due to their negative charges. Mechanical characters of GAGs are heavily influenced by the degree and pattern of sulfation, which may greatly alter their viscoelasticity and physiological functions. Variations in GAG sulfation patterns are created principally through extracellular matrix modeling. Due to their extracellular matrix-organizing abilities, glycosaminoglycans are promising biomacromolecules for the design of new bioactive materials for tissue engineering and tissue reconstruction applications. In this study, we functionalized peptide amphiphile molecules with carboxylate and sulfonate groups to develop nanofibrous networks displaying a range of chemical patterns, and evaluated the effect of the chemical groups over the differentiation fate of rat mesenchymal stem cells. We demonstrate that higher sulfonate-to-glucose ratios are associated with adipogenesis, while higher carboxylate-to-glucose ratios resulted in chondrogenic and osteogenic differentiation of the rat mesenchymal stem cells.