Browsing by Subject "Mesenchymal stem cells."

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Open Access
Contribution of mesenchymal stem cells in cell based therapies
(2010) Tokcaer Keskin, Zeynep
tem cell research evolved as a new hope and has gained tremendous interest in the last two decades to develop new strategies for many of debilitating diseases. Mesenchymal Stem Cells (MSCs) are multipotent cells capable of self-renewal and differentiating into multiple lineages such as osteocytes, adipocytes, chondrocytes, myoblasts, and hepatocytes. MSCs can migrate to the injured tissue and have immunomodulatory effects. Due to these features, MSCs have high therapeutic value in tissue engineering and regenerative medicine. In this thesis, our aim was to investigate the further contribution of the MSCs in different cellular therapies. We used two approaches to accomplish our aim. First, we investigated the possibility of obtaining functional cardiomyocytes from rat MSC within a shorter time period by determining the induction timing of cardiomyocyte differentiation of MSCs. Our data revealed that it is possible to get functional cardiomyocytes from in vitro MSC culture in a shorter time period than previously achieved. This reduction in time may provide emergency cases with access to cell-based therapies that may have previously been unavailable. In the second part of this thesis, we examined in vivo and in vitro effects of a telomerase antagonist, imetelstat (GRN163L) on MSCs. Telomerase activity is essential for the continued growth and survival of malignant cells, therefore inhibition of this activity presents an attractive target for anti-cancer therapy. MSCs also show telomerase activity in maintaining their self-renewal; therefore the effects of telomerase inhibitors on MSCs may be an issue of concern. Our results showed that inhibiting the telomerase activity does not interfere with the self-renewal and differentiation of MSCs under short term in vitro culture conditions.
Open Access
Contribution of toll-like receptors to mesenchymal stem cell differentiation and immunomodulation
(2010) Taş, İbrahim Fırat
characteristics along with several stem cell features such as lineage dependent differentiation and self-renewal capacity. MSCs are known to induce immunomodulatory activity and homing capacity to damaged tissue sites. Such diverse capabilities of MSCs make them distinct from adult stem cells and can be harnessed in several therapeutic applications. Toll-like receptors (TLR) can recognize conserved microbial byproducts and are mainly expressed by innate immune system cells as well as epithelial or endothelial cells. Recent findings suggest that in vitro generated MSCs express some of these pathogen recognition receptors. In our view, to broaden the breath of the therapeutic potential, TLR mediated activation of MSCs and demonstrate its impact on differentiation and immunomodulatory activity is critical. First, bone marrow-derived MSCs were generated and characterized via their surface marker expression by FACS (CD90, CD106 and CD45) at protein level and their message transcripts by RT-PCR (CD11b, CD29, CD34, CD45, CD71, CD73, CD90 and CD166). The most abundant marker was found to be CD90 over several passages. Following determination of TLR expression profile by RT-PCR, contribution of TLR ligands addition (TLR2, TLR3, TLR7 and TLR9) to MSCs during adipogenic or osteogenic differentiation was studied. TLR3 was found to be the most abundant type over several passages. The adipogenic differentiation of rMSCs was found to be facilitated in the presence of TLR2 TLR3 and TLR7 ligands. Additionally, changes in the adipogenic and osteogenic markers (LPL, PPAR-g for adipogenesis, and ALP, OC-1, RUNX for osteogenesis) were analyzed by RT-PCR. While adipogenic markers upregulated osteogenic markers were downregulated in response to TLR ligand treatment. The final part of this study was performed with mouse mesenchymal stem cells. In order to define the immunostimulatory/immunosuppressive potential of mouse MSCs, immunomodulatory character of MSCs were examined in the presence or absence of mouse spleen cells. Our data suggested that when mMSCs are primed with TLRL, a pro-inflammatory cascade as evidenced by increased IL-6 and IFN-γ secretion is initiated either alone or in co-culture with splenocytes. In conclusion, TLR priming of MSCs augments their differentiation primarily into adipogenesis, and mainly these cells are immunostimulatory.
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.