Browsing by Subject "Osterix"

Now showing 1 - 5 of 5
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    Aging aggravates intervertebral disc degeneration by regulating transcription factors toward chondrogenesis
    (Wiley, 2020-02) Silva, Matthew J.; Holguin, Nilsson; Anatomy and Cell Biology, School of Medicine
    Osterix is a critical transcription factor of mesenchymal stem cell fate, where its loss or loss of Wnt signaling diverts differentiation to a chondrocytic lineage. Intervertebral disc (IVD) degeneration activates the differentiation of prehypertrophic chondrocyte-like cells and inactivates Wnt signaling, but its interactive role with osterix is unclear. First, compared to young-adult (5 mo), mechanical compression of old (18 mo) IVD induced greater IVD degeneration. Aging (5 vs 12 mo) and/or compression reduced the transcription of osterix and notochordal marker T by 40-75%. Compression elevated the transcription of hypertrophic chondrocyte marker MMP13 and pre-osterix transcription factor RUNX2, but less so in 12 mo IVD. Next, using an Ai9/td reporter and immunohistochemical staining, annulus fibrosus and nucleus pulposus cells of young-adult IVD expressed osterix, but aging and compression reduced its expression. Lastly, in vivo LRP5-deficiency in osterix-expressing cells inactivated Wnt signaling in the nucleus pulposus by 95%, degenerated the IVD to levels similar to aging and compression, reduced the biomechanical properties by 45-70%, and reduced the transcription of osterix, notochordal markers and chondrocytic markers by 60-80%. Overall, these data indicate that age-related inactivation of Wnt signaling in osterix-expressing cells may limit regeneration by depleting the progenitors and attenuating the expansion of chondrocyte-like cells.
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    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.
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    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.
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    Juvenile Paget’s Disease From Heterozygous Mutation of SP7 Encoding Osterix (Specificity Protein 7, Transcription Factor Sp7)
    (Elsevier, 2020-08) Whyte, Michael P.; Campeau, Philippe M.; McAlister, William H.; Roodman, G. David; Kurihara, Nori; Nenninger, Angela; Duan, Shenghui; Gottesman, Gary S.; Bijanki, Vinieth N.; Sedighi, Homer; Veis, Deborah J.; Mumm, Steven; Medicine, School of Medicine
    Juvenile Paget's disease (JPD) became in 1974 the commonly used name for ultra-rare heritable occurrences of rapid bone remodeling throughout of the skeleton that present in infancy or early childhood as fractures and deformity hallmarked biochemically by marked elevation of serum alkaline phosphatase (ALP) activity (hyperphosphatasemia). Untreated, JPD can kill during childhood or young adult life. In 2002, we reported that homozygous deletion of the gene called tumor necrosis factor receptor superfamily, member 11B (TNFRSF11B) encoding osteoprotegerin (OPG) explained JPD in Navajos. Soon after, other bi-allelic loss-of-function TNFRSF11B defects were identified in JPD worldwide. OPG inhibits osteoclastogenesis and osteoclast activity by decoying receptor activator of nuclear factor κ-B (RANK) ligand (RANKL) away from its receptor RANK. Then, in 2014, we reported JPD in a Bolivian girl caused by a heterozygous activating duplication within TNFRSF11A encoding RANK. Herein, we identify mutation of a third gene underlying JPD. An infant girl began atraumatic fracturing of her lower extremity long-bones. Skull deformity and mild hearing loss followed. Our single investigation of the patient, when she was 15 years-of-age, showed generalized osteosclerosis and hyperostosis. DXA revealed a Z-score of +5.1 at her lumbar spine and T-score of +3.3 at her non-dominant wrist. Biochemical studies were consistent with positive mineral balance and several markers of bone turnover were elevated and included striking hyperphosphatasemia. Iliac crest histopathology was consistent with rapid skeletal remodeling. Measles virus transcripts, common in classic Paget's disease of bone, were not detected in circulating mononuclear cells. Then, reportedly, she responded to several months of alendronate therapy with less skeletal pain and correction of hyperphosphatasemia but had been lost to our follow-up. After we detected no defect in TNFRSF11A or B, trio exome sequencing revealed a de novo heterozygous missense mutation (c.926C>G; p.S309W) within SP7 encoding the osteoblast transcription factor osterix (specificity protein 7, transcription factor SP7). Thus, mutation of SP7 represents a third genetic cause of JPD.
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    The role of Stat3 in skeletal development
    (2017-06-30) Davidson, Rebecca; Li, Jiliang; Yokota, Hiroki; Marrs, Kathleen
    Many factors are present in the development of skeletal tissue. Some factors lead to an increase in bone mass while some lead to a decrease. One factor that is known to have an influence on skeletal development is Signal Transducer and Activator of Transcription 3 (Stat3). This knowledge arose because of a mutation in the Stat3 gene in humans causing a disease called Hyper-IgE Syndrome. This mutation leads to a variety of issues, including decreased bone mass. Because of this, our lab has sought to study Stat3 in its relation to bone. Many studies have already been conducted that discern how Stat3 influences skeletal biology by observing its role in osteoclasts, osteoblasts, and other bone cells. Its role is still unclear, and many studies have provided seemingly contradictory results in how it works on bone tissue. Our lab set up several different studies in order to further elucidate what role Stat3 plays in skeletal development by looking at its effects on osteoblasts and osteoclasts, the bone-forming and bone-destroying cells of the body, respectively. We conditionally knocked out Stat3 in the osteoblasts of mice and compared several different bone parameters to their wild type counterparts at 8 weeks of age. Differences were noted in bone phenotype, including decreased femur length, weight, bone mineral density, and bone mineral content in the cKO compared to their WT counterparts. While no significant difference in trabecular integrity was noted, several differences were observed in cortical bone. These differences indicate that Stat3 has a positive role in osteoblast differentiation, leading to an overall positive effect on bone mass. To observe the role of Stat3 in osteoclasts, in vitro experiments were set up in which pre-osteoclast RAW 264.7 cells were manipulated with Stat3 siRNA or a Stat3 overexpression construct and RANKL to induce differentiation. Using qPCR and western blot assays, it was determined that when Stat3 is knocked down, several important genes in osteoclastogenesis and osteoclast function are more highly expressed than in the control groups. When Stat3 is overexpressed, a similar pattern is observed where these same genes are downregulated in the presence of higher Stat3 levels. These results indicate that Stat3 has an overall inhibitory effect on osteoclastogenesis and osteoclast function, indicating it has a positive effect on bone mass. Future studies could be performed to further elucidate the effects of Stat3 on skeletal development. Isolating the osteoblasts from cKO and WT mice and performing qPCR and western blot assays could be useful in finding out how Stat3 is influencing these cells. Further studies could also be done on the RAW 264.7 cells to find where Stat3 is interacting with the RANKL pathway. A resorption assay could be done with these cells to better understand how function might be influenced by Stat3.