In parathyroid hormone-related protein 1-84 ] knockin mice, expression of the polycomb protein Bmi-1 is reduced and potentially can mediate the phenotypic alterations observed. We have therefore now examined the skeletal phenotype of Bmi-1 À/À mice in vivo and also assessed the function of bone marrow mesenchymal stem cells (BM-MSCs) from Bmi-1 À/À mice ex vivo in culture.Neonatal Bmi-1 À/À mice exhibited skeletal growth retardation, with reduced chondrocyte proliferation and increased apoptosis.Osteoblast numbers; gene expression of alkaline phosphatase, type I collagen, and osteocalcin; the mineral apposition rate; trabecular bone volume; and bone mineral density all were reduced significantly; however, the number of bone marrow adipocytes and Ppar-g expression were increased. These changes were consistent with the skeletal phenotype observed in the PTHrP(1-84) knockin mouse. The efficiency of colony-forming unit fibroblast (CFU-F) formation in bone marrow cultures was decreased, and the percentage of alkaline phosphatase-positive CFU-F and Runx2 expression were reduced. In contrast, adipocyte formation and Ppar-g expression in cultures were increased, and expression of the polycomb protein sirtuin (Sirt1) was reduced. Reduced proliferation and increased apoptosis of BM-MSCs were associated with upregulation of senescence-associated tumor-suppressor genes, including p16, p19, and p27. Analysis of the skeletal phenotype in Bmi-1 À/À mice suggests that Bmi-1 functions downstream of PTHrP. Furthermore, our studies indicate that Bmi-1 maintains self-renewal of BM-MSCs by inhibiting the expression of p27, p16, and p19 and alters the cell fate of BM-MSCs by enhancing osteoblast differentiation and inhibiting adipocyte differentiation at least in part by stimulating Sirt1 expression. Bmi-1 therefore plays a critical role in promoting osteogenesis. ß
Type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) are both characterized by chronic low-grade inflammation. The role of Th17 and its related cytokines in T2DM and CAD is unclear. Here we investigated the serum levels of five Th17-related cytokines (IL-17, IL-22, MIP-3α, IL-9, and IL-27) in T2DM, CAD, and T2DM-CAD comorbidity patients. IL-22 was found to be elevated in all three conditions. Elevated serum IL-22 was independently associated with the incidence of T2DM and CAD. Conversely, IL-22 was found to protect endothelial cells from glucose- and lysophosphatidylcholine- (LPC-) induced injury, and IL-22R1 expression on endothelial cells was increased upon treatment with high glucose and LPC. Blocking of IL-22R1 with IL-22R1 antibody diminished the protective role of IL-22. Our results suggest that IL-22 functions as a double-edged sword in T2DM and CAD and that IL-22 may be used in the treatment of chronic inflammatory diseases such as T2DM and CAD.
SUMMARYTo determine whether the calcium-sensing receptor (CaR) participates in tooth formation and dental alveolar bone development in mandibles in vivo, we examined these processes, as well as mineralization, in 2-week-old CaR-knockout (CaR -/-) mice. We also attempted to rescue the phenotype of CaR -/-mice by genetic means, in mice doubly homozygous for CaR and 25-hydroxyvitamin D 1a-hydroxylase [1a(OH)ase] or parathyroid hormone (Pth). In CaR -/-mice, which exhibited hypercalcemia, hypophosphatemia and increased serum PTH, the volumes of teeth and of dental alveolar bone were decreased dramatically, whereas the ratio of the area of predentin to total dentin and the number and surface of osteoblasts in dental alveolar bone were increased significantly, as compared with wild-type littermates. The normocalcemia present in CaR -/-
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