Notch 1 Impairs Osteoblastic Cell Differentiation

• Published in: Endocrinology (Philadelphia) 2003-12, Vol.144 (12), p.5631-5639
• Main Authors: Sciaudone, Maria, Gazzerro, Elisabetta, Priest, Leah, Delany, Anne M, Canalis, Ernesto
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Adipocytes; Adipocytes - cytology; Adipogenesis; Alkaline phosphatase; Animals; Apoptosis; Biological and medical sciences; Bone Marrow Cells - cytology; Bone morphogenetic protein 2; Bone morphogenetic proteins; CCAAT/enhancer-binding protein; Cell differentiation; Cell Differentiation - physiology; Cell proliferation; Cell surface receptors; Collagen (type I); Cortisol; Differentiation (biology); Enhancer-of-split protein; Expression vectors; FosB protein; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression - physiology; Hormones; Mice; Nodules; Notch protein; Osteoblastogenesis; Osteoblasts; Osteoblasts - cytology; Osteoblasts - physiology; Osteocalcin; Peroxisome proliferator-activated receptors; Phenotype; Phenotypes; Proteins; Receptor, Notch1; Receptors; Receptors, Cell Surface - genetics; Receptors, Cell Surface - metabolism; Retroviridae - genetics; Signal Transduction - physiology; Skull - cytology; Stromal Cells - cytology; Transcription Factors; Vertebrates: endocrinology; Wnt protein; β-Catenin
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2003-0463

Notch receptors are single pass transmembrane receptors activated by membrane-bound ligands with a role in cell proliferation and differentiation. As Notch 1 and 2 mRNAs are expressed by osteoblasts and induced by cortisol, we postulated that Notch could regulate osteoblastogenesis. We investigated the effects of retroviral vectors directing the constitutive expression of the Notch 1 intracellular domain (NotchIC) in murine ST-2 stromal and in MC3T3 cells. NotchIC overexpression was documented by increased Notch 1 transcripts and activity of the Notch-dependent Hairy Enhancer of Split promoter. In the presence of bone morphogenetic protein-2 (BMP-2), ST-2 cells differentiated toward osteoblasts forming mineralized nodules, and Notch 1 opposed this effect and decreased the expression of osteocalcin, type I collagen, and alkaline phosphatase transcripts and Δ2Δ FosB protein. Further, NotchIC decreased Wnt/β-catenin signaling. As cells differentiated in the presence of BMP-2, they underwent apoptosis, and Notch opposed this event. In the presence of cortisol, NotchIC induced the formation of mature adipocytes and enhanced the effect of cortisol on adipsin, peroxisome proliferator-activated receptor-γ2 and CCAAT enhancer binding protein α and δ mRNA levels. NotchIC also opposed MC3T3 cell differentiation and the expression of a mature osteoblastic phenotype. In conclusion, NotchIC impairs osteoblast differentiation and enhances adipogenesis in stromal cell cultures.