Absence of sclerostin adversely affects B-cell survival.
ABSTRACT: Increased osteoblast activity in sclerostin-knockout (Sost(-/-)) mice results in generalized hyperostosis and bones with small bone marrow cavities resulting from hyperactive mineralizing osteoblast populations. Hematopoietic cell fate decisions are dependent on their local microenvironment, which contains osteoblast and stromal cell populations that support both hematopoietic stem cell quiescence and facilitate B-cell development. In this study, we investigated whether high bone mass environments affect B-cell development via the utilization of Sost(-/-) mice, a model of sclerosteosis. We found the bone marrow of Sost(-/-) mice to be specifically depleted of B cells because of elevated apoptosis at all B-cell developmental stages. In contrast, B-cell function in the spleen was normal. Sost expression analysis confirmed that Sost is primarily expressed in osteocytes and is not expressed in any hematopoietic lineage, which indicated that the B-cell defects in Sost(-/-) mice are non-cell autonomous, and this was confirmed by transplantation of wild-type (WT) bone marrow into lethally irradiated Sost(-/-) recipients. WT?Sost(-/-) chimeras displayed a reduction in B cells, whereas reciprocal Sost(-/-) ?WT chimeras did not, supporting the idea that the Sost(-/-) bone environment cannot fully support normal B-cell development. Expression of the pre-B-cell growth stimulating factor, Cxcl12, was significantly lower in bone marrow stromal cells of Sost(-/-) mice, whereas the Wnt target genes Lef-1 and Ccnd1 remained unchanged in B cells. Taken together, these results demonstrate a novel role for Sost in the regulation of bone marrow environments that support B cells.
Project description:Romosozumab, a humanized monoclonal antibody specific for sclerostin (SOST), has been approved for treatment of postmenopausal women with osteoporosis at a high risk for fracture. Previous work in sclerostin global knockout (<i>Sost</i><sup>-/-</sup>) mice indicated alterations in immune cell development in the bone marrow (BM), which could be a possible side effect in romosozumab-treated patients. Here, we examined the effects of short-term sclerostin depletion in the BM on hematopoiesis in young mice receiving sclerostin antibody (Scl-Ab) treatment for 6 weeks, and the effects of long-term <i>Sost</i> deficiency on wild-type (WT) long-term hematopoietic stem cells transplanted into older cohorts of <i>Sost</i><sup>-/-</sup> mice. Our analyses revealed an increased frequency of granulocytes in the BM of Scl-Ab-treated mice and WT→<i>Sost</i><sup>-/-</sup> chimeras, indicating myeloid-biased differentiation in <i>Sost</i>-deficient BM microenvironments. This myeloid bias extended to extramedullary hematopoiesis in the spleen and was correlated with an increase in inflammatory cytokines TNFα, IL-1α, and MCP-1 in <i>Sost</i><sup>-/-</sup> BM serum. Additionally, we observed alterations in erythrocyte differentiation in the BM and spleen of <i>Sost</i><sup>-/-</sup> mice. Taken together, our current study indicates novel roles for <i>Sost</i> in the regulation of myelopoiesis and control of inflammation in the BM.
Project description:Innate memory phenotype (IMP) CD4+ T cells are non-conventional Î±Î² T cells exhibiting features of innate immune cells, characterized as CD44high and CD62Llow in periphery. It is recently reported by our group that bone marrow chimeric mice lacking thymic MHCI expression develop predominantly IMP CD8+ T cells, while those lacking hematopoietic MHCI develop predominantly naÃ¯ve CD8+ T cells. Here we perform hirarchical clustering analysis and found that CD4+ T cells share similar property: chimeras lacking thymic MHCII gave rise to predominantly CD4+ T cells that resemble IMP CD4+ T cells observed in WT mice, and vice versa, chimeras lacking hematopoietic MHCII had a majority of naÃ¯ve-like CD4+ T cells resembling naÃ¯veCD4+ T cells seen in WT mice. We used microarrays to compare the global programme of gene expression to determine whether the hematopoietic MHCII selected CD4+ T cells are IMP, and whether the thymic MHCII selected CD4+ T cells are naÃ¯ve CD4+ T cells as observed in WT mice. Through hierarchical clustering and analysis of global gene differential expression, we determined that hematopoietic MHCII dependent IMP CD4+ T cells generated from WT bone marrow transplanted into irradiated MHCII-/- recipients, resemble IMP CD4+ T cells in WT mice, while naÃ¯ve CD4+ T cells generated from MHCII-/- bone marrow transplanted into irradiated WT recipients, resemble naÃ¯ve CD4+ T cells in WT mice. Cell Sorting was performed using a Cytopeia Influx Cell Sorter. Chimeric IMP (CD45.1+TCRÎ²+CD4+CD44highCD62Llow) CD4+ T cells were sorted from splenocytes of CD45.1+WTâCD45.2+MHCII-/- chimeras (WM IMP CD4), and chimeric naÃ¯ve (CD45.2+TCRÎ²+CD4+CD44lowCD62Lhigh) CD4+ T cells were sorted from splenocytes of CD45.2+MHCII-/- â CD45.1+WT chimeras (MW naÃ¯ve CD4) respectively, 8 weeks post transplantation. WT IMP (TCRÎ²+CD4+CD44highCD62Llow) and naÃ¯ve (TCRÎ²+CD4+CD44lowCD62Lhigh) CD4+ T cells were sorted from splenocytes of 8-week old WT mice.
Project description:Inactivating mutations of the SOST (sclerostin) gene are associated with overgrowth and sclerosis of the skeleton. To determine mechanisms by which increased amounts of calcium and phosphorus are accreted to enable enhanced bone mineralization in the absence of sclerostin, we measured concentrations of calciotropic and phosphaturic hormones, and urine and serum calcium and inorganic phosphorus in mice in which the sclerostin (sost) gene was replaced by the ?-D-galactosidase (lacZ) gene in the germ line. Knockout (KO) (sost(-/-)) mice had increased bone mineral density and content, increased cortical and trabecular bone thickness, and greater net bone formation as a result of increased osteoblast and decreased osteoclast surfaces compared with wild-type (WT) mice. ?-Galactosidase activity was detected in osteocytes of sost KO mice but was undetectable in WT mice. Eight-week-old, male sost KO mice had increased serum 1?,25-dihydroxyvitamin D, decreased 24,25-dihydroxyvitamin D, decreased intact fibroblast growth factor 23, and elevated inorganic phosphorus concentrations compared with age-matched WT mice. 25-Hydroxyvitamin D 1?-hydroxylase cytochrome P450 (cyp27B1) mRNA was increased in kidneys of sost KO mice compared with WT mice. Treatment of cultured proximal tubule cells with mouse recombinant sclerostin decreased cyp27B1 mRNA transcripts. Urinary calcium and renal fractional excretion of calcium were decreased in sost KO mice compared with WT mice. Sost KO and WT mice had similar serum calcium and parathyroid hormone concentrations. The data show that sclerostin not only alters bone mineralization, but also influences mineral metabolism by altering concentrations of hormones that regulate mineral accretion.
Project description:Osteoblasts play an increasingly recognized role in supporting hematopoietic development and recently have been implicated in the regulation of B lymphopoiesis. Here we demonstrate that the heterotrimeric G protein alpha subunit G(s)alpha is required in cells of the osteoblast lineage for normal postnatal B lymphocyte production. Deletion of G(s)alpha early in the osteoblast lineage results in a 59% decrease in the percentage of B cell precursors in the bone marrow. Analysis of peripheral blood from mutant mice revealed a 67% decrease in the number of circulating B lymphocytes by 10 days of age. Strikingly, other mature hematopoietic lineages are not decreased significantly. Mice lacking G(s)alpha in cells of the osteoblast lineage exhibit a reduction in pro-B and pre-B cells. Furthermore, interleukin (IL)-7 expression is attenuated in G(s)alpha-deficient osteoblasts, and exogenous IL-7 is able to restore B cell precursor populations in the bone marrow of mutant mice. Finally, the defect in B lymphopoiesis can be rescued by transplantation into a WT microenvironment. These findings confirm that osteoblasts are an important component of the B lymphocyte niche and demonstrate in vivo that G(s)alpha-dependent signaling pathways in cells of the osteoblast lineage extrinsically regulate bone marrow B lymphopoiesis, at least partially in an IL-7-dependent manner.
Project description:Dynamic interaction between prostate cancer and the bone microenvironment is a major contributor to metastasis of prostate cancer to bone. In this study, we utilized an in vitro co-culture model of PC3 prostate cancer cells and osteoblasts followed by microarray based gene expression profiling to identify previously unrecognized prostate cancer-bone microenvironment interactions. Factors secreted by PC3 cells resulted in the up-regulation of many genes in osteoblasts associated with bone metabolism and cancer metastasis, including Mmp13, Il-6 and Tgfb2, and down-regulation of Wnt inhibitor Sost. To determine whether altered Sost expression in the bone microenvironment has an effect on prostate cancer metastasis, we co-cultured PC3 cells with Sost knockout (Sost(KO)) osteoblasts and wildtype (WT) osteoblasts and identified several genes differentially regulated between PC3-Sost(KO) osteoblast co-cultures and PC3-WT osteoblast co-cultures. Co-culturing PC3 cells with WT osteoblasts up-regulated cancer-associated long noncoding RNA (lncRNA) MALAT1 in PC3 cells. MALAT1 expression was further enhanced when PC3 cells were co-cultured with Sost(KO) osteoblasts and treatment with recombinant Sost down-regulated MALAT1 expression in these cells. Our results suggest that reduced Sost expression in the tumor microenvironment may promote bone metastasis by up-regulating MALAT1 in prostate cancer.
Project description:Fanconi anemia is a complex heterogeneous genetic disorder with a high incidence of bone marrow failure, clonal evolution to acute myeloid leukemia and mesenchymal-derived congenital anomalies. Increasing evidence in Fanconi anemia and other genetic disorders points towards an interdependence of skeletal and hematopoietic development, yet the impact of the marrow microenvironment in the pathogenesis of the bone marrow failure in Fanconi anemia remains unclear. Here we demonstrated that mice with double knockout of both <i>Fancc</i> and <i>Fancg</i> genes had decreased bone formation at least partially due to impaired osteoblast differentiation from mesenchymal stem/progenitor cells. Mesenchymal stem/progenitor cells from the double knockout mice showed impaired hematopoietic supportive activity. Mesenchymal stem/progenitor cells of patients with Fanconi anemia exhibited similar cellular deficits, including increased senescence, reduced proliferation, impaired osteoblast differentiation and defective hematopoietic stem/progenitor cell supportive activity. Collectively, these studies provide unique insights into the physiological significance of mesenchymal stem/progenitor cells in supporting the marrow microenvironment, which is potentially of broad relevance in hematopoietic stem cell transplantation.
Project description:Bone marrow adipose tissue (MAT) is negatively associated with bone mass. Since osteoblasts and adipocytes are derived from the same precursor cells, adipocyte differentiation may occur at the expense of osteoblast differentiation. We used MAT-deficient KitW/W-v (MAT-) mice to determine if absence of MAT reduced bone loss in hindlimb-unloaded (HU) mice. Male MAT- and wild-type (WT) mice were randomly assigned to a baseline, control or HU group (n?=?10 mice/group) within each genotype and HU groups unloaded for 2 weeks. Femurs were evaluated using micro-computed tomography, histomorphometry and targeted gene profiling. MAT- mice had a greater reduction in bone volume fraction after HU than did WT mice. HU MAT- mice had elevated cancellous bone formation and resorption compared to other treatment groups as well as a unique profile of differentially expressed genes. Adoptive transfer of WT bone marrow-derived hematopoietic stem cells reconstituted c-kit but not MAT in KitW/W-v mice. The MAT- WT???KitW/W-v mice lost cancellous bone following 2 weeks of HU. In summary, results from this study suggest that MAT deficiency was not protective, and was associated with exaggerated disuse-induced cancellous bone loss.
Project description:Innate memory phenotype (IMP) CD8+ T cells are non-conventional αβ T cells exhibiting features of innate immune cells, and are significantly increased in the absence of non-receptor tyrosine kinase ITK. Their developmental path and function are not clear, particularly whether they can contribute to antigen specific responses. We found that WT bone marrow gives rise to IMP CD8+ T cells in irradiated MHCI-/- recipients, resembling those in Itk-/- mice determined by expression of surface markers. However, CD8+ T cells share similar expression of memory markers. We used microarrays to compare the global programme of gene expression to determine whether the CD8+ T cells selected by hematopoietic MHCI are IMP CD8+ T cells as observed in the absence of ITK, or the result of homeostatic expansion of T cell contamination in the donor bone marrow. Through analysis of global gene expression correlation and differential expression, we determined that hematopoietic MHCI dependent IMP CD8+ T cells generated in irradiated MHCI-/- recipients, resemble those in Itk-/- mice, but distinct from CD8+ T cells derived via homeostatic proliferation. Cell sorting was performed using a FACSAria Cell Sorter (BD Biosciences, San Diego, CA). IMP CD8+ T cells (TCRβ+CD8α+CD44hi) were sorted from splenocytes of WT→MHCI-/- chimeras 8 weeks post transplantation and 8-week old Itk-/- mice. To generate HP cells, naïve CD8+ T cells (TCRβ+CD8α+CD44lo) were sorted and injected into Rag1-/- recipients (0.5 million /mouse, retro-orbital injection), followed by sorting of TCRβ+CD8α+ splenocytes 8 weeks post adoptive transfer. We sought to compare cells with the same gender and age, thus all donors were female, and ages (absolute age for Itk null and age post transfer for chimeras and HP model) were 8 weeks.
Project description:Bone-forming osteoblasts play critical roles in supporting bone marrow hematopoiesis. Pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced PSCs (iPSC), are capable of differentiating into osteoblasts. To determine the capacity of stem cells needed to rescue aberrant skeletal development and bone marrow hematopoiesis in vivo, we used a skeletal complementation model. Mice deficient in Runx2, a master transcription factor for osteoblastogenesis, fail to form a mineralized skeleton and bone marrow. Wild-type (WT) green fluorescent protein (GFP)+ ESCs and yellow fluorescent protein (YFP)+ iPSCs were introduced into Runx2-null blastocyst-stage embryos. We assessed GFP/YFP+ cell contribution by whole-mount fluorescence and histological analysis and found that the proportion of PSCs in the resulting chimeric embryos is directly correlated with the degree of mineralization in the skull. Moreover, PSC contribution to long bones successfully restored bone marrow hematopoiesis. We validated this finding in a separate model with diphtheria toxin A-mediated ablation of hypertrophic chondrocytes and osteoblasts. Remarkably, chimeric embryos harboring as little as 37.5% WT PSCs revealed grossly normal skeletal morphology, suggesting a near-complete rescue of skeletogenesis. In summary, we demonstrate that fractional contribution of PSCs in vivo is sufficient to complement and reconstitute an osteoblast-deficient skeleton and hematopoietic marrow. Further investigation using genetically modified PSCs with conditional loss of gene function in osteoblasts will enable us to address the specific roles of signaling mediators to regulate bone formation and hematopoietic niches in vivo. Stem Cells 2017;35:2150-2159.