Time-dependent expression of SNAT2 mRNA in the contused skeletal muscle of rats: a possible marker for wound age estimation.

To estimate the age of skeletal muscle contusion, the expression of SNAT2 mRNA in contused skeletal muscle of rats was detected by real-time polymerase chain reaction (PCR). In total, 78 Sprague-Dawley male rats were divided into control and contusion groups. At 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, and 48 h (n = 6) after contusion, the rats were sacrificed with a lethal dose of pentobarbital. Another 24 rats received contusion injuries at 6, 12, 18, and 24 h (n = 6) after death. Total RNA was isolated from muscle specimens using the TRIzol reagent and reverse-transcribed into first-strand cDNA. Sequence-specific primers and TaqMan fluorogenic probes for SNAT2 mRNA and RPL13 mRNA were designed using the AlleleID 6 software, and the expression levels of SNAT2 mRNA were determined by real-time PCR. At 4, 16, 20, and 24 h after contusion, expression levels of SNAT2 mRNA normalized to RPL13 mRNA increased by 2.07 (P < 0.05), 2.53 (P < 0.05), 2.68 (P < 0.05), and 2.06 fold (P < 0.05) respectively, versus that in the control group. However, there was no significant change in the expression level of SNAT2 mRNA from 24 to 48 h (P > 0.05) after contusion, when normalized to RPL13 mRNA. There was no change in the expression level of SNAT2 mRNA between the normal skeletal muscle from the left limb of the same injured rat and the control. Also, no degradation of SNAT2 mRNA was detected in the postmortem samples (P > 0.05). This result suggests that the determination of SNAT2 mRNA levels by real-time PCR may be useful for estimating wound age.