1 3495 95 IDENTIFICATION OF MIRNAS POTENTIALLY INVOLVED IN BRONCHIOLITIS OBLITERANS SYNDROME: A COMPUTATIONAL STUDY. THE PATHOGENESIS OF BRONCHIOLITIS OBLITERANS SYNDROME (BOS), THE MAIN CLINICAL PHENOTYPE OF CHRONIC LUNG ALLOGRAFT DYSFUNCTION, IS POORLY UNDERSTOOD. RECENT STUDIES SUGGEST THAT EPIGENETIC REGULATION OF MICRORNAS MIGHT PLAY A ROLE IN ITS DEVELOPMENT. IN THIS PAPER WE PRESENT THE APPLICATION OF A COMPLEX COMPUTATIONAL PIPELINE TO PERFORM ENRICHMENT ANALYSIS OF MIRNAS IN PATHWAYS APPLIED TO THE STUDY OF BOS. THE ANALYSIS CONSIDERED THE FULL SET OF MIRNAS ANNOTATED IN MIRBASE (VERSION 21), AND APPLIED A SEQUENCE OF FILTERING APPROACHES AND STATISTICAL ANALYSES TO REDUCE THIS SET AND TO SCORE THE CANDIDATE MIRNAS ACCORDING TO THEIR POTENTIAL INVOLVEMENT IN BOS DEVELOPMENT. DYSREGULATION OF TWO OF THE SELECTED CANDIDATE MIRNAS-MIR-34A AND MIR-21 -WAS CLEARLY SHOWN IN IN-SITU HYBRIDIZATION (ISH) ON FIVE EXPLANTED HUMAN BOS LUNGS AND ON A RAT MODEL OF ACUTE AND CHRONIC LUNG REJECTION, THUS DEFINITELY IDENTIFYING MIR-34A AND MIR-21 AS PATHOGENIC FACTORS IN BOS AND CONFIRMING THE EFFECTIVENESS OF THE COMPUTATIONAL PIPELINE. 2016 2 4371 40 MIRNAS POTENTIALLY INVOLVED IN POST LUNG TRANSPLANT-OBLITERATIVE BRONCHIOLITIS: THE ROLE OF MIR-21-5P. EPIGENETIC CHANGES, INCLUDING MIRNAS DEREGULATION, HAVE BEEN SUGGESTED TO PLAY A SIGNIFICANT ROLE IN DEVELOPMENT OF OBLITERATIVE BRONCHIOLITIS (OB) IN TRANSPLANTED LUNGS. MANY STUDIES HAVE TRIED TO IDENTIFY IDEAL CANDIDATE MIRNAS AND THE DOWNSTREAM PATHWAYS IMPLICATED IN THE BRONCHIOLAR FIBRO-OBLITERATIVE PROCESS. SEVERAL CANDIDATE MIRNAS, PREVIOUSLY INDICATED AS POSSIBLY BEING ASSOCIATED WITH OB, WERE ANALYZED BY COMBINING THE QUANTITATIVE REAL TIME-POLYMERASE CHAIN REACTION (QRT-PCR) AND IN SITU HYBRIDIZATION (ISH) OF LUNG TISSUES OF OB AFFECTED PATIENTS. DISEASE AND OB-LESION-SPECIFIC EXPRESSION OF MIR-21-5P WAS CONFIRMED AND BY COMPUTATIONAL ANALYSIS WE WERE ABLE TO IDENTIFY THE NETWORK OF GENES MOST PROBABLY ASSOCIATED MIR-21-5P IN THE CONTEXT OF OB FIBROGENESIS. AMONG ALL POTENTIALLY ASSOCIATED GENES, STAT3 HAD A VERY HIGH PROBABILITY SCORE. IMMUNOHISTOCHEMISTRY SHOWED THAT STAT3/MIR-21-5P WERE CO-OVER EXPRESSED IN OB LESIONS, THUS, SUGGESTING MIR-21-5P COULD REGULATE STAT3 EXPRESSION. HOWEVER, MIR-21-5P INHIBITION IN CULTURES OF BRONCHIOLITIS OBLITERANS SYNDROME (BOS) DERIVED MYOFIBROBLASTS DID NOT SIGNIFICANTLY AFFECT STAT3 MRNA AND PROTEIN EXPRESSION LEVELS. THIS STUDY DEMONSTRATES THE SPECIFICITY OF MIR-21-5P OVER-EXPRESSION IN OB LESIONS AND CONTRIBUTES TO EXISTING KNOWLEDGE ON THE MIR-21-5P DOWNSTREAM PATHWAY. ACTIVATION OF STAT3 IS ASSOCIATED WITH MIR-21-5P UPREGULATION, HOWEVER, STAT-3 NETWORK ACTIVATION IS MOST LIKELY COMPLEX AND MIR-21-5P IS NOT THE SOLE REGULATOR OF STAT3. 2021 3 2331 28 EPIGENETIC REGULATION OF INFLAMMATION BY MICRORNAS IN POST-INFECTIOUS BRONCHIOLITIS OBLITERANS. OBJECTIVES: POST-INFECTIOUS BRONCHIOLITIS OBLITERANS (PIBO) IS A RARE, CHRONIC DISEASE INITIATED BY SEVERE INFECTION AND FOLLOWED BY PERPETUATING INFLAMMATION AND OBLITERATION OF THE SMALL AIRWAYS. MICRORNAS (MIRNAS) HAVE BEEN PROPOSED TO PLAY A CENTRAL ROLE AS EPIGENETIC REGULATORS, WHICH CONTROL RESOLUTION AND PREVENT THE UNCONTROLLED PROGRESS OF INFLAMMATION. THE AIM OF THIS STUDY WAS TO DEFINE BIOMARKERS ON THE LEVEL OF POST-TRANSCRIPTIONAL GENE REGULATION IN ORDER TO CHARACTERISE PIBO. METHODS: A TOTAL OF 39 PATIENTS WITH WELL-DEFINED PIBO AND 31 CONTROLS FROM TWO CENTRES, BARCELONA, SPAIN, AND FRANKFURT, GERMANY, WERE ANALYSED BY NEXT-GENERATION SEQUENCING (NGS). THE EVALUATION OF THE BIOLOGICAL TARGETS OF THE MIRNAS WAS PERFORMED BY PATHWAY ENRICHMENT ANALYSIS AND PROTEIN-PROTEIN INTERACTION NETWORK ANALYSIS RESPECTIVELY. RESULTS: PATIENTS WITH PIBO HAD SIGNIFICANTLY LOWER LUNG FUNCTION VALUES AND INCREASED AIRWAY INFLAMMATION IN INDUCED SPUTUM AS INDICATED BY TOTAL CELL COUNTS, NEUTROPHILS, IL-1BETA, IL-6, IL-8 AND TGF-BETA COMPARED TO CONTROLS.NEXT-GENERATION SEQUENCING ANALYSIS REVEALED A TOTAL OF 22 DYSREGULATED MIRNAS, WHICH PASSED SIGNIFICANCE THRESHOLD FOR PADJ