title: Assessing an improved protocol for plasma microRNA extraction.
abstract: The first step in biomarkers discovery is to identify the best protocols for their purification and analysis. This issue is critical when considering peripheral blood samples (plasma and serum) that are clinically interesting but meet several methodological problems, mainly complexity and low biomarker concentration. Analysis of small molecules, such as circulating microRNAs, should overcome these disadvantages. The present study describes an optimal RNA extraction method of microRNAs from human plasma samples. Different reagents and commercially available kits have been analyzed, identifying also the best pre-analytical conditions for plasma isolation. Between all of them, the column-based approaches were shown to be the most effective. In this context, miRNeasy Serum/Plasma Kit (from Qiagen) rendered more concentrated RNA, that was better suited for microarrays studies and did not require extra purification steps for sample concentration and purification than phenol based extraction methods. We also present evidences that the addition of low doses of an RNA carrier before starting the extraction process improves microRNA purification while an already published carrier dose can result in significant bias over microRNA profiles. Quality controls for best protocol selection were developed by spectrophotometry measurement of contaminants and microfluidics electrophoresis (Agilent 2100 Bioanalyzer) for RNA integrity. Selected donor and patient plasma samples and matched biopsies were tested by Affymetrix microarray technology to compare differentially expressed microRNAs. In summary, this study defines an optimized protocol for microRNA purification from human blood samples, increasing the performance of assays and shedding light over the best way to discover and use these biomarkers in clinical practice.
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain ; CIBEREHD, CIBER de enfermedades hepáticas y digestivas, Barcelona, Spain.
authors.forename: Inés
authors.initials: I
authors.lastname: Moret
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain ; Genomics Unit, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Dolors
authors.initials: D
authors.lastname: Sánchez-Izquierdo
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain ; CIBEREHD, CIBER de enfermedades hepáticas y digestivas, Barcelona, Spain ; Gastroenterology Unit, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Marisa
authors.initials: M
authors.lastname: Iborra
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain ; CIBEREHD, CIBER de enfermedades hepáticas y digestivas, Barcelona, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Tortosa
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Navarro-Puche
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain ; CIBEREHD, CIBER de enfermedades hepáticas y digestivas, Barcelona, Spain ; Gastroenterology Unit, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Nos
authors.affiliation: Genetics Department, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Cervera
authors.affiliation: Instituto de Investigación Sanitaria del Hospital La Fe, Valencia, Spain ; CIBEREHD, CIBER de enfermedades hepáticas y digestivas, Barcelona, Spain ; Gastroenterology Unit, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Beltrán
mesh_terms: D001671:Biochemistry / Q000379:methods*; D020869:Gene Expression Profiling; D006801:Humans; D035683:MicroRNAs / Q000097:blood* / Q000302:isolation & purification*; D036103:Nanotechnology; D020411:Oligonucleotide Array Sequence Analysis; D013053:Spectrophotometry
chemical_list: D035683:MicroRNAs