Identification of altered salivary microRNAs in Cavalier King Charles Spaniels affected by mitral valve disease at different ACVIM stages

Myxomatous mitral valve disease (MMVD) in Cavalier King Charles Spaniels (CKCSs) can be diagnosed at a young age. Early and sensitive biomarkers related to the disease are currently lacking. MicroRNAs (miRNAs) are involved in the onset and progression of canine MMVD. This study aimed to profile the salivary miRNAs associated with MMVD severity in CKCSs and to identify their target genes. This was a pilot prospective, cross-sectional study. Saliva was collected from twenty-five CKCSs belonging to the American College of Veterinary Internal Medicine (ACVIM) stages A (n. 6), B1 (n. 13), and B2 (n. 6), and salivary miRNAs' expression was profiled by Next Generation Sequencing. MiRNAs' target genes were identified using bioinformatic tools. Results showed that 25 miRNAs were differentially expressed (DE) in the ACVIM A versus B1 group; 35 DE-miRNAs were identified in the ACVIM B2 versus B1 group; 4 miRNAs were up-regulated in ACVIM stage B1 patients compared to both ACVIM stages A and B2. The identified miRNAs impacted genes related to cell survival and functions. Results demonstrated that miRNAs can be extracted and quantified from canine saliva, and that their profile changes following disease progression. Validation studies are necessary to investigate their diagnostic value. Overall design: Saliva was collected from twenty-five CKCSs belonging to the American College of Veterinary Internal Medicine (ACVIM) stages A (n. 6), B1 (n. 13), and B2 (n. 6), and salivary miRNAs' expression was profiled by Next Generation Sequencing.