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Acute Appendicitis: Transcript Profiling of blood identifies promising biomarkers and potential underlying processes

ABSTRACT: Background: The diagnosis of acute appendicitis can be surprisingly difficult without computed tomography, which carries significant radiation exposure. Genome-wide expression profiling was applied to whole blood RNA of acute appendicitis patients versus patients with other abdominal disorders, in order to identify biomarkers of appendicitis. From a large cohort of emergency patients, a discovery set of patients with surgically confirmed appendicitis, or abdominal pain from other causes, was identified. RNA from whole blood was profiled by microarrays, and RNA levels were filtered by a combined fold-change (>2) and p value (<0.05). A separate set of patients, including patients with respiratory infections, was used to validate a partial least squares discriminant (PLSD) prediction model. Results: Transcript profiling identified 37 differentially expressed genes (DEG) in appendicitis versus abdominal pain patients. The DEG list contained 3 major ontologies: infection-related, inflammation-related, and ribosomal processing. Appendicitis patients had lower level of neutrophil defensin mRNA (DEFA1,3), but higher levels of alkaline phosphatase (ALPL) and interleukin-8 receptor-ß (IL8RB), which was confirmed in a larger cohort of 60 patients using droplet digital PCR (ddPCR). Conclusions: Patients with acute appendicitis have detectable changes in the mRNA expression levels of factors related to neutrophil inate defense systems. The low defensin mRNA levels suggest that appendicitis patient's immune cells are not directly activated by pathogens, but are primed by diffusible factors in the microenvironment of the infection. The detected biomarkers are consistent with prior evidence that biofilm-forming bacteria in the appendix may be an important factor in appendicitis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE83091 | GEO | 2016/06/08

SECONDARY ACCESSION(S): PRJNA324717

REPOSITORIES: GEO

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Project description:Abstract BACKGROUND: Gene expression profiling (GEP) in cells obtained from peripheral blood has demonstrated to be a very useful approach for biomarker discovery and for studying molecular pathogenesis of prevalent diseases. While there is limited literature availble on gene expression markers associated to Chronic Obstructive Pulmonary Disease (COPD), the transcriptomic picture associated to critical respiratory illness in this disease is not known to the present moment. RESULTS: By using Agilent microarray chips, we have profiled gene expression signatures in whole blood of 28 COPD patients hospitalized with distinct degree of respiratory compromise.12 of them needed of admission to the ICU, while 16 were admitted to the Respiratory Medicine Service. GeneSpring GX 11.0 software was used for performing statistical comparison of transcript levels between ICU and non ICU patients. Ingenuity pathway analysis 8.5 (IPA) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were employed to select, annotate and visualize genes by function and pathway (gene ontology). T-test evidenced 1501 genes differentially expressed between ICU and non ICU patients. IPA and KEGG analysis of the most representative biological functions revealed that ICU patients showed increased levels of neutrohil gene transcripts, being [cathepsin G (CTSG)], [elastase, neutrophil expressed (ELANE)], [proteinase 3 (PRTN3)], [myeloperoxidase (MPO)], [cathepsin D (CTSD)], [defensin, alpha 3, neutrophil-specific (DEFA3)], azurocidin 1 (AZU1)], [bactericidal/permeability-increasing protein (BPI)] the most representative ones. Proteins codified by these genes form part of the azurophilic granules of neutrophils and are involved in both antimicrobial defence and tissue damage. This ?neutrophil signature? was paralleled by necessity of advanced respiratory and vital support, and presence of bacterial infection. CONCLUSION: study of transcriptomic signatures in blood suggests a central role of neutrophil proteases in COPD patients with critical respiratory illness. Measurement / modulation of the expression of these genes could represent an option for clinical monitoring and treatment of severe COPD exacerbations. Keywords: COPD, critical, expression, gene, microarray, neutrophil, proteases.

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Acute Appendicitis: Transcript Profiling of blood identifies promising biomarkers and potential underlying processes

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