Background: Kawasaki disease (KD) is a childhood systemic vasculitis that exhibits a specific preference for the coronary arteries. The aetiology remains unknown and there are no especially diagnostic tests. microRNAs (miRNAs) are 18 to 23 nucleotides non-coding RNAs that are negative regulator of gene expression and play a crucial role in the regulatory network of the genome. Recently, circulating miRNAs have been found presentation in human plasma and displayed some characteristics of the ideal biomarker. However, few researches explored differentially expressed miRNAs in the plasma of KD patients. Our study is to identify circulating miRNAs in KD plasma which can serve as potential biomarkers of KD diagnosis.
Materials and methods: The total of five pairs of acute KD and normal plasma samples were analyzed using ABI miRNAs TLDA Assay chip. Differentially expression of miR-125a-5p in plasma were confirmed by quantitative real-time PCR (qRT-PCR) in independent cohort (acute KD = 30, convalescent KD = 30 and healthy control = 32). After bioinformatics prediction, miR-125a-5p vector and inhibitor were transfected into HUVECs respectively, to observe MKK7 expression as a potential target gene. Flow cytometry was used to analyze apoptosis. The mRNA and protein levels of desired genes including MKK7, Caspase-3, Bax and Bcl2 were detected by qRT-PCR and western blotting.
Results: Eighteen miRNAs were differentially expressed in acute KD's plasma compared with healthy control. miR-125a-5p was significantly increased in plasma of KD patients (p = 0.000), but no variation between acute and convalescent KD (p = 0.357). Moreover, the results from the gain and loss functions of miR-125a-5p in HUVECs have shown that miR-125a-5p remarkably suppressed MKK7 expression, as a novel target gene. Importantly, miR-125a-5p also induced apoptosis in HUVECs through inhibition MKK7 levels to regulate Bax/Bcl2 pathway resulting to activate Caspase-3.
Conclusion: Our study indicated that the circulating miR-125a-5p levels in KD's plasma have remarkably evaluated compared with healthy individuals. miR-125a-5p might play a role in the development of KD by regulating target gene MKK7 to induce apoptosis in vascular endothelial cells. Therefore, our findings have suggested that detected miR-125a-5p levels in plasma could be used as a potential biomarker in early KD diagnosis.