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Streptococcus mutans differential gene expression in response to simulated microgravity

ABSTRACT: Astronauts have been previously shown to exhibit decreased salivary lysozyme and increased dental calculus and gingival inflammation in response to space flight, host factors that could contribute to oral diseases such as caries and periodontitis. However, the specific physiological response of caries-causing bacteria such as Streptococcus mutans to space flight and/or ground-based simulated microgravity has not been extensively investigated. In this study, High Aspect Ratio Vessel (HARV) S. mutans simulated microgravity and normal gravity cultures were assessed for changes in metabolite and transcriptome profiles, H2O2 resistance, and competence in sucrose-containing biofilm media. Stationary phase S. mutans simulated microgravity cultures displayed increased killing by H2O2 compared to normal gravity control cultures, but competence was not affected. RNA-seq analysis revealed that expression of 153 genes was up-regulated ≥ 2-fold and 94 genes down-regulated ≥ 2-fold during simulated microgravity HARV growth. These included a number of genes located on extrachromosomal elements, as well as genes involved in carbohydrate metabolism, translation, and stress responses. Collectively, these results suggest that growth under microgravity analog conditions promotes changes in S. mutans gene expression and physiology that may translate to an altered cariogenic potential of this organism during space flight missions.

ORGANISM(S): Streptococcus mutans

PROVIDER: GSE90166 | GEO | 2017/03/01

SECONDARY ACCESSION(S): PRJNA354617

REPOSITORIES: GEO

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Project description:Microgravity leads to a 10-15% loss of bone mass in astronauts during space flight. Osteoclast is the multinucleated bone resorbing cell. In this study, we used NASA developed ground based Rotary Wall Vessel Bioreactor (RWV), Rotary Cell Culture System (RCCS) to simulate microgravity (Î¼Xg) conditions and demonstrated a significant increase (2-fold) in osteoclastogenesis compared to ground based control (Xg) mouse bone marrow cultures. We further determined the gene expression profiling of RAW 264.7 osteoclast progenitor cells in microgravity by agilent microarray analysis. Gene expression pattern was functional group clustered by transcriptome analysis using gene ontology tree machine (GOTM) for cell proliferation/survival, differentiation and function. We confirm the microgravity modulated gene expression critical for osteoclast differentiation by real-time RT-PCR and Western blot analysis in murine bone marrow cultures. We identify transcription factors such as c-Jun, c-Fos, PU-1 critical for osteoclast differentiation is up-regulated in microgravity conditions. In addition, microgravity resulted in 2.3 and 2.0-fold increase in the level of cathepsin K and MMP-9 matrix metalloproteinase expression in preosteoclast cells involved in the bone resorption process respectively. We also demonstrate a significant increase in the expression levels of M-CSF receptor, c-Fms and PLCÎ³2 and S100A8 molecules that play an important role in Ca2+ signaling essential for osteoclast function. Further, microgravity stimulated preosteoclast cells showed elevated cytosolic Ca2+ levels compared to ground based control cells. Thus, microgravity regulated gene expression profiling in preosteoclast cells provide new insights in to molecular mechanisms and therapeutic targets of osteoclast differentiation/activation responsible for bone loss and fracture risk in astronauts during space flight mission. Microgravity associated with space flight is a challenge for normal bone homeostasis. Astronauts experience 10-15% bone loss during a space flight mission. We aimed to determine the effect of simulated microgravity on osteoclast preosteoclasts cells. RAW264.7 cells (1.5 x 106 /ml) were loaded in RCCS with DMEM containing 10% FBS for 24 h. The cells were stimulated with RANKL (80ng/ml) for 24 h to obtain preosteoclasts in parallel with ground based control cells. Total RNA was isolated using RNAzol reagent (Biotecx Labs, Houston, TX) from control (Xg) and microgravity (Î¼Xg) subjected cells and hybridized with Agilent whole mouse genome 4x44K array system. Slides were washed and scanned on an Agilent G2565 microarray scanner. Data obtained were analyzed with Agilent feature extraction and GeneSpring GX v7.3.1 software packages (Genus biosystem, Inc. Northbrook, IL, USA).

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Streptococcus mutans differential gene expression in response to simulated microgravity

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