The roles of Wnt antagonists Dkk1 and sFRP4 during adipogenesis of human adipose tissue-derived mesenchymal stem cells.
OBJECTIVE
The canonical Wnt signalling pathway performs an important function in the control of adipogenesis. However, the mechanisms and mediators underlying these interactions have yet to be defined in detail. Thus, this study was performed in order to elucidate the roles of the Wnt family during adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hAMSCs).


METHODS
We assessed several members of the Frizzled (FZD) family, the receptors of Wnts, inhibitors including the secreted frizzled-related protein (sFRP) family and Dickkopfs (Dkks), and the downstream factor, beta-catenin. Expressional levels of adipogenic markers regulated by the small interfering RNA of Dkk1 (siDkk1) and sFRP4 (sisFRP4) were assessed using real-time quantitative PCR and Western blot analysis.


RESULTS
The mRNA level of Dkk1 was expressed abundantly in the early stages of adipogenesis and decreased rapidly during the late stages of adipogenesis. However, sFRP4 mRNA was up-regulated gradually during adipogenic differentiation in hAMSCs. Expression of FZD1, FZD7 and beta-catenin were reduced during adipogenic differentiation. Transfection of hAMSCs with siDkk1 or sisFRP4 partially inhibited differentiation of hAMSCs into adipocytes and restored levels of beta-catenin.


CONCLUSIONS
We determined that Dkk1 was up-regulated transiently in the early stages of adipogenesis, and that sFRP4 levels increased gradually during adipogeneis via inhibition of Wnt signalling. Collectively, these results show that Dkk1 and sFRP4 perform an important function in adipogenesis in hAMSCs.
Park
J-R
JR
Adult Stem Cell Research Center, College of Veterinary Medicine, Seoul National University, Seoul, South Korea, andLaboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, and BK21 Program for Veterinary Science, Seoul National University, Seoul, South Korea.
Jung
J-W
JW
Adult Stem Cell Research Center, College of Veterinary Medicine, Seoul National University, Seoul, South Korea, andLaboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, and BK21 Program for Veterinary Science, Seoul National University, Seoul, South Korea.
Lee
Y-S
YS
Adult Stem Cell Research Center, College of Veterinary Medicine, Seoul National University, Seoul, South Korea, andLaboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, and BK21 Program for Veterinary Science, Seoul National University, Seoul, South Korea.
Kang
K-S
KS
Adult Stem Cell Research Center, College of Veterinary Medicine, Seoul National University, Seoul, South Korea, andLaboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, and BK21 Program for Veterinary Science, Seoul National University, Seoul, South Korea.
D050156:Adipogenesis; D000273:Adipose Tissue / Q000166:cytology* / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051153:Wnt Proteins / Q000037:antagonists & inhibitors*; D000094742:Secreted Frizzled-Related Proteins
D036341:Intercellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D051153:Wnt Proteins; C501126:DKK1 protein, human; C118723:SFRP4 protein, human; D000094742:Secreted Frizzled-Related Proteins