MSX2 promotes osteogenesis and suppresses adipogenic differentiation of multipotent mesenchymal progenitors.
In the aorta, diabetes activates an osteogenic program that includes expression of bone morphogenetic protein-2 (BMP2) and the osteoblast homeoprotein Msx2. To evaluate BMP2-Msx2 signaling in vascular calcification, we studied primary aortic myofibroblasts. These cells express vascular smooth muscle cell (VSMC) markers, respond to BMP2 by up-regulating Msx2, and undergo osteogenic differentiation with BMP2 treatment or transduction with a virus encoding Msx2. The osteoblast factor osterix (Osx) is up-regulated 10-fold by Msx2, but Runx2 mRNA is unchanged; the early osteoblast marker alkaline phosphatase increases 50-fold with mineralized nodule formation enhanced 30-fold. Adipocyte markers are concomitantly suppressed. To better understand Msx2 actions on osteogenesis versus adipogenesis, mechanistic studies were extended to C3H10T1/2 mesenchymal cells. Msx2 enhances osteogenic differentiation in synergy with BMP2. Osteogenic actions depend upon intrinsic Msx2 DNA binding; the gain-of-function variant Msx2(P148H) directs enhanced mineralization, whereas the binding-deficient variant Msx2(T147A) is inactive. Adipogenesis (lipid accumulation, Pparg expression) is inhibited by Msx2. By contrast, suppression of adipogenesis does not require Msx2 DNA binding; inhibition occurs in part via protein-protein interactions with C/EBPalpha that control Pparg transcription. Thus, Msx2 regulates osteogenic versus adipogenic differentiation of aortic myofibroblasts. Myofibroblasts capable of both fates can be diverted to the osteogenic lineage by BMP2-Msx2 signaling and contribute to vascular calcification.
Cheng
Su-Li
SL
Department of Medicine, Washington University School of Medicine, Division of Bone and Mineral Diseases, St. Louis, Missouri 63110, USA.
Shao
Jian-Su
JS
Charlton-Kachigian
Nichole
N
Loewy
Arleen P
AP
Towler
Dwight A
DA
D017667:Adipocytes / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000473:pathology; D002454:Cell Differentiation; D002460:Cell Line; D019070:Cell Lineage; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D018398:Homeodomain Proteins; D008156:Luciferases / Q000378:metabolism; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013234:Stem Cells; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C084119:MSX2 protein; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D004247:DNA; D008156:Luciferases; D000469:Alkaline Phosphatase