Classification of various muscular tissues using miRNA profiling.

MicroRNAs (miRNAs) are endogenous small RNAs of 18-23 nucleotides that regulate gene expression. Recently, plasma miRNAs have been investigated as biomarkers for various diseases. In the present study, we explored whether miRNA expression profiling of various muscle cells may be useful for the diagnosis of various diseases involving muscle necrosis. miRNA expression profiling was assessed by miRNA array and real-time reverse-transcriptase polymerase chain reaction by using a reverse primer of a stem loop structure. Profiling of various muscle cells of mouse, including cardiac muscles, skeletal muscles, and vascular and visceral smooth muscles, indicated that profiling of miR-1, miR-133a, miR-133b, miR-145, miR-206, miR-208a, miR-208b, and miR499 were adequate to discriminate muscle cells. miR-145 was remarkably highly expressed in smooth muscles. miR-208a and miR-499 were highly expressed in cardiomyocytes. miR-133a was highly expressed in fast-twitch skeletal muscles. miR-206 and miR-208b were expressed in the slow-twitch skeletal muscles, and they can likely discriminate fast- and slow-twitch types of skeletal muscle cells. We observed that brown fat adipose cells had an miRNA expression profile very similar to those of skeletal muscle cells in the mouse. Plasma concentrations of miR-133a and miR-145 were extremely useful in diagnosing skeletal muscle necrosis in a mouse model of Duchenne muscular dystrophy and colon smooth muscle necrosis in a rat ischemic colitis model, respectively. In the present study, we investigated the miRNA expression profiles of various muscular tissues. Our results suggest that expression profiling would be useful for the diagnosis of various diseases such as muscular necrosis.