Project description:The anaphylatoxin C5a is a potent mediator of innate immunity and promotes inflammation via its receptor C5aR1 upon complement system activation danger-associated molecular patterns. Both C5a and C5aR1 are thought to be contributing factors in inflammatory and infectious conditions of the bone. Bone fracture healing, for example, was significantly improved when applying a C5aR1-antagonist in a rodent model of severe systemic inflammation and osteoblasts were found to be target cells for C5a in this setting. Interestingly, osteoblasts up-regulate C5aR1 during osteogenic differentiation and after bone injury. Further, C5a induces inflammatory cytokines, such as IL-6, and the osteoclastogenic mediator RANKL in osteoblasts. However, the molecular mechanisms underlying C5a-C5aR1 signaling axis in osteoblasts remain unclear, and further targets of C5a are still elusive. Using microarray analysis, we analyzed intracellular events following C5aR1 activation in osteoblasts and defined up- or down-regulated genes and their belonging biological pathways.
Project description:Influence of complement anaphylatoxin C5a on neutrophil gene expression Trauma causes an early activation of the complement system, which leads to excessive generation of the anaphylatoxin C5a. Furthermoren, alterations in neutrophil function are often associated with infectious complication after trauma. Studies have shown that C5a is a main contributor to neutrophil dysfunction. However, the pathophysiological mechanisms still remain elusive. Aim of the study was to evaluate whether C5a can induce changes in expression profiles. We identified distinct classes of up-regulated genes during this process.
Project description:We report high-throughput profiling of gene expression from murine primary macrophages. We profile mRNA in control and endotoxin stimulated macrophages, and examine the effect of AHR ligand (SGA360) under inflammatory status. This study provides a framework for understanding transcriptional changes caused by SGA360 during activated inflammatory signaling .
Project description:MIcroRNA expression profiling of primary murine splenic dendritic cells (Flt3L expanded) comparing untreated cells to cells infected with Influenza A or stimulated with polyI:C in vitro.
Project description:Mucolipidosis type II (MLII) is a severe inherited multisystemic disorder caused by mutations in the GNPTAB gene. Skeletal abnormalities are a predominant feature of MLII. Here we investigate the gene expression in a knock-in mouse model for mucolipidosis type II, generated by the insertion of a cytosine in the murine Gnptab gene (c.3082insC) that is homologous to a homozygous mutation in an MLII patient. Since osteoblasts are critically involved in regulating bone development and remodeling, a genome-wide expression analysis was performed with RNA isolated from primary cultures of osteoblasts originating from MLII knock-in mice (KI) compared to RNA from wild-type (WT) osteoblasts to identify dysregulated genes involved in pathogenic mechanisms. Primary osteoblasts were isolated from calvaria of 5-day-old wild-type (WT) and MLII knock-in littermates (KI). RNA was extracted at day 10 of differentiation induced by ascorbic acid and beta-glycerophosphate and hybridization on Affymetrix microarrays. We used preparations of RNA from two individual primary cultures of osteoblasts for every genotype (WT_OB_I, WT_OB_II, KI_OB_I, KI_OB_II) and compared WT vs KI samples.
Project description:That phosphate homeostasis is tightly linked to skeletal mineralization is probably best underscored by the fact that the phosphaturic hormone FGF23 is primarily expressed by terminally differentiated osteoblasts/osteocytes, and that increased circulating FGF23 levels are causative for different types of hypophosphatemic rickets. In contrast, FGF23-inactivation results in hyperphosphatemia, and unexpectedly this phenotype is associated with severe osteomalacia in Fgf23-deficient mice. In this context it is interesting that different types of bone cells have been shown to respond to extracellular phosphate, thereby raising the concept that phosphate can act as a signaling molecule. To identify phosphate-responsive genes in primary murine osteoblasts we performed genome-wide expression analysis with cells maintained in medium containing either 1 mM or 4 mM sodium phosphate for 6 hours. As confirmed by qRT-PCR, this analysis revealed that several known osteoblast differentiation markers (Bglap, Ibsp or Phex) were unaffected by raising extracellular phosphate levels. In contrast, we found that the expression of Enpp1 and Ank, two genes encoding inhibitors of matrix mineralization, was induced by extracellular phosphate, while the expression of Sost and Dkk1, two genes encoding inhibitors of bone formation, was negatively regulated. The ability of osteoblasts to respond to extracellular phosphate was dependent on their differentiation state, and shRNA-dependent repression of the phosphate transporter Slc20a1 in MC3T3-E1 cells partially abolished their molecular response to phosphate. Taken together, our results provide further evidence for a role of extracellular phosphate as a signaling molecule and raise the possibility that severe hyperphosphatemia can negatively affect skeletal mineralization.
Project description:A microRNA array was performed using human primary osteoblasts (hOB) obtained from trabecular bone of postmenopausal women after knee replacement due to osteoarthritis in order to determine the miRNAs expressed in these osteoblastic cells.