Browsing by Subject "Runx2"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Biopsy proven medullary sponge kidney: clinical findings, histopathology, and role of osteogenesis in stone and plaque formation
    (John Wiley & Sons, Inc., 2015-05) Evan, Andrew P.; Worcester, Elaine M.; Williams, James C., Jr.; Sommer, Andre J.; Lingeman, James E.; Phillips, Carrie L.; Coe, Fredric L.; Department of Anatomy & Cell Biology, IU School of Medicine
    Medullary sponge kidney (MSK) is associated with recurrent stone formation, but the clinical phenotype is unclear because patients with other disorders may be incorrectly labeled MSK. We studied 12 patients with histologic findings pathognomonic of MSK. All patients had an endoscopically recognizable pattern of papillary malformation, which may be segmental or diffuse. Affected papillae are enlarged and billowy, due to markedly enlarged inner medullary collecting ducts (IMCD), which contain small, mobile ductal stones. Patients had frequent dilation of Bellini ducts, with occasional mineral plugs. Stones may form over white (Randall's) plaque, but most renal pelvic stones are not attached, and have a similar morphology as ductal stones, which are a mixture of calcium oxalate and apatite. Patients had no abnormalities of urinary acidification or acid excretion; the most frequent metabolic abnormality was idiopathic hypercalciuria. Although both Runx2 and Osterix are expressed in papillae of MSK patients, no mineral deposition was seen at the sites of gene expression, arguing against a role of these genes in this process. Similar studies in idiopathic calcium stone formers showed no expression of these genes at sites of Randall's plaque. The most likely mechanism for stone formation in MSK appears to be crystallization due to urinary stasis in dilated IMCD with subsequent passage of ductal stones into the renal pelvis where they may serve as nuclei for stone formation.
  • Thumbnail Image
    Item
    Decreased JMJD3 expression in mesenchymal stem cells contributes to longterm suppression of osteoblast differentiation in multiple myeloma
    (2018-06) Zhao, Wei; Roodman, G. David; Broxmeyer, Hal E.; Yoder, Mervin C.; Clapp, D. Wade; Guise, Theresa
    Multiple myeloma (MM) is the most frequent cancer to involve the skeleton, with over 80% of myeloma patients developing lytic bone disease (MMBD). Importantly, MM-associated bone lesions rarely heal even when patients are in complete remission. Bone marrow stromal cells (BMSCs) isolated from MM patients have a distinct genetic profile and an impaired osteoblast (OB) differentiation capacity when compared to BMSCs from healthy donors. Utilizing an in vivo model of MMBD and patient samples, we showed that BMSCs from tumor-bearing bones failed to differentiate into OBs weeks after removal of MM cells. Both Runx2 and Osterix, the master transcription factors for OB differentiation, remained suppressed in these BMSCs. However, the molecular mechanisms for MM-induced long-term OB suppression are poorly understood. We characterized both Runx2 and Osterix promoters in murine pre-osteoblast MC4 cells by chromatin immunoprecipitation (ChIP). The transcriptional start sites (TSSs) of Runx2 and Osterix in untreated MC4 cells were co-occupied by transcriptionally active histone 3 lysine 4 tri-methylation (H3K4me3) and transcriptionally repressive histone 3 lysine 27 tri-methylation (H3K27me3), termed the “bivalent domain”. These bivalent domains became transcriptionally silent with increasing H3K27me3 levels when MC4 cells were co-cultured with MM cells or treated with TNF-α, an inflammatory cytokine increased in MM bone marrow microenvironment. The increasing H3K27me3 levels induced by MM cells or TNF-α were associated with the downregulation of the H3K27 demethylase JMJD3 in MC4 cells and murine BMSCs. Knockdown of JMJD3 in MC4 cells was sufficient to inhibit OB differentiation. Further, ectopic overexpression of JMJD3 in MC4 cells partially rescued the suppression of osteoblast differentiation induced by TNFa. We also found that pre-incubation of MC4 cells with the NF-kB inhibitor quinazoline (QNZ) before TNF-a treatment prevented the downregulation of JMJD3. In agreement with our in vitro findings, BMSCs from MM patients had persistently decreased JMJD3 expression compared to healthy BMSCs. Our findings together demonstrate that decreased JMJD3 expression in BMSCs contributes to the long-term OB suppression in MMBD by remodeling histone landscapes at the Runx2 and Osterix TSSs. Thus, developing strategies to restore JMJD3 expression in BMSCs should increase bone formation and possibly decrease tumor burden in MM.
  • Thumbnail Image
    Item
    EZH2 or HDAC1 Inhibition Reverses Multiple Myeloma-Induced Epigenetic Suppression of Osteoblast Differentiation
    (American Association for Cancer Research, 2017-04) Adamik, Juraj; Jin, Shunqian; Sun, Quanhong; Zhang, Peng; Weiss, Kurt R.; Anderson, Judith L.; Silbermann, Rebecca; Roodman, G. David; Galson, Deborah L.; Medicine, School of Medicine
    In multiple myeloma, osteolytic lesions rarely heal because of persistent suppressed osteoblast differentiation resulting in a high fracture risk. Herein, chromatin immunoprecipitation analyses reveal that multiple myeloma cells induce repressive epigenetic histone changes at the Runx2 locus that prevent osteoblast differentiation. The most pronounced multiple myeloma-induced changes were at the Runx2-P1 promoter, converting it from a poised bivalent state to a repressed state. Previously, it was observed that multiple myeloma induces the transcription repressor GFI1 in osteoblast precursors, which correlates with decreased Runx2 expression, thus prompting detailed characterization of the multiple myeloma and TNFα-dependent GFI1 response element within the Runx2-P1 promoter. Further analyses reveal that multiple myeloma-induced GFI1 binding to Runx2 in osteoblast precursors and recruitment of the histone modifiers HDAC1, LSD1, and EZH2 is required to establish and maintain Runx2 repression in osteogenic conditions. These GFI1-mediated repressive chromatin changes persist even after removal of multiple myeloma. Ectopic GFI1 is sufficient to bind to Runx2, recruit HDAC1 and EZH2, increase H3K27me3 on the gene, and prevent osteogenic induction of endogenous Runx2 expression. Gfi1 knockdown in MC4 cells blocked multiple myeloma-induced recruitment of HDAC1 and EZH2 to Runx2, acquisition of repressive chromatin architecture, and suppression of osteoblast differentiation. Importantly, inhibition of EZH2 or HDAC1 activity in pre-osteoblasts after multiple myeloma exposure in vitro or in osteoblast precursors from patients with multiple myeloma reversed the repressive chromatin architecture at Runx2 and rescued osteoblast differentiation.Implications: This study suggests that therapeutically targeting EZH2 or HDAC1 activity may reverse the profound multiple myeloma-induced osteoblast suppression and allow repair of the lytic lesions.