Changes in expression of specific miRNAs and their target genes in repair of exercise-induced muscle injury in rats.

The effects of muscle-specific miRNAs in the repair of exercise-induced muscle injury were investigated by examining the changes in their expression and that of the target genes in rat skeletal muscle. Two-month-old agile male rats were randomly divided into exercise and static control groups, the former subdivided into 0-h, 6-h, 12-h, 1-day, 2-day, 3-day, 1-week, and 2-week groups based on time after exercise. Left gastrocnemii of rats were hematoxylin-eosin stained whereas the right gastrocnemii were used for expression analysis of muscle-specific miRNAs (miR-1 and miR-206) and their target genes, Cx43 and HDAC. Cellular swelling and increased cell volume and intercellular spaces were observed histologically in the 0-h group. Unlike the control group, cells continued to swell whereas intercellular spaces decreased slightly, in the 6-h, 12-h, 1-day, and 2-day groups. Cell swelling was most serious in the 3-day group. In the 1-week group, inflammatory cell infiltration decreased and in the 2-week group, repair was almost complete. The differences in miR-1 expression between the groups were neither obvious nor significant. miR-206 expression increased; however, it differed significantly from that in group C only in the 1-week group. Cx43 and HDAC4 mRNA expression first decreased and then increased compared to that in the control group; differences in HDAC4 mRNA expression were significant in the 1-week group. Compared to the control group, the differences in Cx43 protein levels were significant in the 0-h and 3-day groups. Thus, miR-206 and Cx43 are involved in the repair of exercise-induced muscle injury.
Competing Interests: The authors declare no conflict of interest.