MAPK4 and pulmonary arterial hypertension: Reactome analysis of the microRNAs which were significant p ≤ 0.01 suggested Pre-NOTCH Transcription and Translation and Pre-NOTCH Expression and Processing pathways (p = 0.008) and MAPK6/MAPK4 signalling (p = 0.014) to be of possible importance in PAH-HPMEC.