Analysis of Salivary Micro-RNAs and Allergen Profile in Patients with Asthma

Rationale: Salivary microRNAs (miRNAs) have untapped potential as non-invasive biomarkers to diagnose and phenotype asthma.  We previously demonstrated that miRNAs are differentially expressed in the saliva of asthmatics compared to non-asthmatics.  We sought to determine whether these could be used as a tool to characterize phenotypic differences in asthmatics.

Methods: After IRB approval, saliva was collected from asthmatics (n=26) and miRNAs were isolated by guanidium hydrochloride/phenol-chloroform extraction, reversed transcribed using a poly-A, 3’adapter system, and analyzed by quantitative real-time PCR.  An unsupervised cluster analysis of miRNA expression was performed, using a panel previously found to be dysregulated in saliva of asthmatics (miRs-200b, -146a, -92b, -330-5p, -200c, and Let7a).  Two-tailed, unpaired T test (p<0.05 considered significant) was used to measure differences between clusters.

Results: Two clusters of asthmatics were identified (group A, n=12 subjects; group B, n=14 subjects). Statistical differences were discovered between these groups for age (36.6±14.8  in Group A vs 51.8±13.6 in Group B, p=0.012), FEV1% predicted (92.3±13.6 in Group A vs and 67.5±24.1 in Group B, P=0.004), and total number of aeroallergen sensitivities (mean number of positive aeroallergen tests was 10.7±6.5  in Group A,  and 5.21±4.0 in Group B, p=0.015).  Eosinophil count was not statistically different (340±284 in Group A vs 378±251 in Group B, P=0.7609).

Conclusions: Group A was associated with lower saliva miRNA concentrations and contained subjects that were younger, had better lung function, and were more allergic.  Salivary miRNAs may have utility in phenotypic analysis of asthmatics and require further study.