Genetic and epigenetic effect of estrogen on mesenchymal stem cell maintenance and differentiation

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.