Abstract: Objective To investigate the relationship between the expression of secreted frizzled-related protein 5 （SFRP5） mRNA and the time interval after skeletal muscle injury in rats by real-time PCR. Methods A total of ninety SD rats were randomly divided into the contusion groups at different times including 4 h, 8 h, 12 h, 16 h, 20 h, 24 h, 28 h, 32 h, 36 h, 40 h, 44 h, 48 h after contusion, incision groups at different times including 4h and 8h after incision and the control group. The samples were taken from the contused zone at different time points. The total RNA was isolated from the samples and reversely transcribed to analyze the expression levels of SFRP5 mRNA. Results Compared to the control group, the expression of SFRP5 mRNA in contusion groups were down-regulated within 48 h after contusion and reached the lowest level at 20 h, and the expression of SFRP5 mRNA gradually increased from 20 h to 48 h after contusion. The expression of SFRP5 mRNA in the incised groups were significantly lower than that of the contusion groups at 4 h after injury. At the time of 8 h, the expression levels between the contusion and incision groups showed no statistically significant difference. Conclusion It is suggested that SFRP5 mRNA analysis may show regular expression and can be a marker for estimation of skeletal muscle injury age.

Key words: forensic pathology, wounds and injuries, polymerase chain reaction, skeletal muscle, RNA, messenger, secreted frizzled-related protein 5, rats