Changes in extracellular activin A:follistatin ratio during differentiation of a mesenchymal progenitor cell line, ROB-C26 into osteoblasts and adipocytes.
We investigated the effects of BMP-2 and dexamethasone (Dex) on follistatin (FS) and activin A expressions in a mesenchymal progenitor cell line, ROB-C26 (C26). C26 cells stimulated to differentiate into osteoblastic cells by blocking myogenic differentiation after BMP-2 treatment and into adipocytes with Dex treatment. Alkaline phosphatase (ALP) mRNA expression and its activity in the confluent C26 cells were dose- and time-dependently stimulated by BMP-2, but inhibited by Dex. The stimulatory effect on FS and activin A mRNA expressions by BMP-2 and Dex were dose-dependent. Cycloheximide pre-treatment indicated that FS and activin A expressions appear to be the direct target of BMP-2 and Dex signaling. BMP-2 time-dependently increased FS and activin A levels. Dex also increased FS level, but induced a time-dependent biphasic effect on activin A level, a decrease (2-6 h) followed by an increase (12-72 h). The data of the ratio of activin A concentration in the culture media to that of FS (activin A:FS ratio) measured by ELISA showed that BMP-2-induced osteoblastic differentiation involved an activin-dominant microenvironment, whereas Dex-induced adipocyte differentiation involved a FS-dominant microenvironment. Excess FS suppressed the stimulatory ALP activity of BMP-2, whereas activin A prevented not only Dex-induced inhibitory ALP activity, but also adipogenesis via suppression of the adipocyte transcriptional factor cascade. These results indicate that BMP-2-induced activin-dominant microenvironment may be critical for osteoblastic differentiation by restricting the antagonistic effects of FS on BMP activity, while Dex-induced FS-dominant microenvironment may be critical for adipocyte differentiation by restricting the inhibitory action of activin A on adipocyte differentiation.
Kawabata
Niki
N
Department of Oral and Maxillofacial Surgery Nihon University School of Dentistry, Tokyo 101-8310, Japan.
Kamiya
Naoko
N
Suzuki
Naoto
N
Matsumoto
Mitsuhiko
M
Takagi
Minoru
M
D028341:Activins / Q000096:biosynthesis*; D017667:Adipocytes / Q000166:cytology*; D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000378:metabolism*; D038681:Follistatin / Q000096:biosynthesis*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D019485:Bone Morphogenetic Proteins; D038681:Follistatin; D012333:RNA, Messenger; C422405:activin A; D028341:Activins; D003907:Dexamethasone