Genetic and epigenetic effect of estrogen on mesenchymal stem cell maintenance and differentiation
Author
Bitirim, Ceylan Verda
Advisor
Yuluğ, Işık G.
Date
2013Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
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.