ObjectiveTo study microRNA (miRNA) involved in the regulation of sinus cell differentiation by comparing sinus node, atrial myocardium, and ventricular myocardium specific miRNA expression profile differences in Kunming mice. MethodsA total of 180 Kunming mice, aged 60-90 days and weighing 35-45 g, were selected without gender differences after the method of anatomical localization for sinus node had been confirmed by preliminary experiments in another 10 Kunming mice. All the sinus node, atrial myocardium, and ventricular myocardium tissue from 180 mice were dissected and frozen by liquid nitrogen. The structure of tissue was observed by HE staining. Total RNA were extracted and quality-controlled before hybridize with miRNA chip. The chips with miRNA were used to screen specific miRNAs; and correlation analysis of gene function was done. ResultsThe area of mice sinus node located at juncture of the superior vena cava and the right atrium junction with crista as its longitudinal axis, ranged 2.0 mm×1.5 mm×1.0 mm. HE staining showed the sinus cells were less, with no stripes, lightly stained cytoplasm, large and round nucleus, and there were much fibrous connective tissue around cells with a visible sinus node artery. The miRNA microarray results showed that compared with atrial myocardium and ventricular myocardium, there were 39 differentially expressed miRNAs in sinus node, including 12 up-regulated miRNAs and 27 down-regulated miRNAs. Based on the regulatory networks of differential miRNA and target gene, the regulatory miRNA was obtained. ConclusionThe differentially expressed miRNA in mice sinus node possibly may be involved in the regulation of sinus cell differentiation.