Evaluation of miR-155 Expression in Cystic Fibrosis Patients

Background: Cystic Fibrosis (CF) is the most fatal genetic disorder among white populations. It is a multi-system disease with various symptoms, which causes many different complications. miRNAs are a class of endogenous small non-coding RNAs of 19-22 nt that regulate mRNAs post-transcriptionally. Different types of miRNAs, including miR-155, are expressed in CF lung epithelial cells. The elevated expression level of miR-155 contributes to the pro-inflammatory expression of IL-8 in CF lung epithelial cells. Therefore, miR-155 may play an important role in the activation of IL-8 in CF. Objectives: The present study aimed to investigate the relationship between miR-155 expression level and the clinical manifestations of CF patients. Methods: The participants of this cross-sectional study included 30 CF patients (according to sweat test and < F508 in the genetic study) with age ranging from 5 to 27 years (M = 17, F = 13) and 30 healthy individuals with age ranging from 8 to 28 (M = 17, F = 13). Using RNA purification Kit, microRNAs, we extracted microRNAs from serum samples, and cDNA was synthesized via the cDNA synthesis kit. Then, the levels of miR-155 were measured by real-time PCR, and the expression levels were compared in different groups of CF patients according to the Shwachman-Kulczycki scoring system. Results: The expression level of miR-155 was elevated in CF patients compared to healthy controls (Fold change: 1.41, P value = 0.056). Interestingly, the elevated level of miR-155 in severe and moderate patients (according to Shwachman-Kulczycki score) showed a significant difference compared to the other patients, where age and sex were not an influential factor. Conclusions: Serum expression levels of miR-155 are different in CF patients, along with the severity of the disease. By suppressing the expression of miR-155, more investigations might lead to the development of new treatment strategies for CF.