Differential Expression of STATs and Its Function in Osteogenesis of Mesenchymal Stem Cells

PURPOSE: To investigate the role of STAT5 during osteogenesis differentiation of human mesenchymal stem cells(hMSC). MATERIALS AND METHODS: To assess the expression pattern of STATs during osteogenic differentiation, we performed western blot analysis and RT-PCR. By RNA interference, we have performed effect of STAT5A and STAT5B in osteogenesis. As a result of Luciferase assay, the promoter activity of DLX5 was decreased by STAT5A. RESULTS: To assess the expression pattern of STATs during osteogenic differentiation, we have performed western blot and RT-PCR after 14 day differentiation period. STAT1, 2, 3 and 4 showed no change in expression level during differentiation, while STAT5A and STAT5B displayed steady increase compared to the control. When STAT5A was knock down, the level of osteogenesis was increased. The transcriptional activity of DLX5 was decreased about 70% by STAT5A. CONCLUSION: The expression of STAT5A and STAT5B increased during osteogenesis of hMSC. Also, we shown that STAT5A regulated the transcriptional activity of DLX5. These results indicate that STAT5A acts as a pivotal transcription factor in osteogenesis of hMSC.ope

골수유래 중간엽 줄기세포의 골분화기간 동안에 STAT5A와 STAT5B의 역할 기능 분석

Dept. of Medical Science/석사Human bone-marrow mesenchymal stromal cells (MSCs) can differentiate into a variety of cell types such as adipocyte, chondrocyte, myoblast, and osteoblast, depending on induction conditions. The each process of differentiation is carried out by interaction of various proteins and hormones. The feasibility of therapeutic applications of MSCs has been raised based on these potential differentiation characteristics, however, the precise mechanism of differentiation has not yet been determined. As a possible regulator of MSCs differentiation, STAT proteins have been reported. STAT is a family of proteins consisted of 7 different types. They form either a homodimer or a heterodimer, and are phosphorylated by receptors for various growth factors and cytokines. Phosphorylation of STAT induces translocation of STAT to nuclei, then, STAT regulates the expression of target genes. In particular, STAT5 has been reported to accelerate the differentiation of MSCs to adipocytes. However, there relationship between STAT and differentiation of MSCs into osteoblast has hardly been studied. In this study, a series of studies have been carried out to determine the mechanism how STAT5A affects the human bone-marrow MSCs differentiation into osteoblast. When MSCs were induced to differentiate into osteoblast, the expression of STAT5A and STAT5B proteins were increased compared to the control cells. Knocking-down the expression of STAT5A with specific siRNAs promoted the differentiating of MSCs into osteoblast. Expressions of Runx2 and DLX5 proteins and mRNAs, marker genes for osteoblast, were confirmed to be increased in MSCs transfected with STAT5A siRNAs. In contrast, over-expression of STAT5A during the differentiating process of MSCs into osteoblast, decreased Runx2 and DLX5 at protein and mRNA levels. The transcriptional activity of the DLX5 promoter was decreased by over-expression of STAT5A and increased by knocking-down of STAT5A with siRNAs. In summary, these data suggest that the induction of MSC differentiation into osteoblast is mediated by DLX5 which is regulated by STAT5A as a pivotal transcription factor in osteogenesis.ope