Time course analysis of large-scale gene expression in incised muscle using correspondence analysis

The time course of wound healing or the estimation of wound age is one of the most important research subjects in forensic pathology. In this study, we obtained microarray data of incision injury samples of mouse skeletal muscle at 3 different time points post-injury (6, 12, and 24 h). To visualize the time course fluctuation in gene expression on a plot, and to examine large-scale data using various analytical methods, correspondence analysis (CA) was carried out on microarray data that was converted to a matrix (data type is fold change (FC) values) consisting of data of each time point (columns) by each gene (rows) as variables. Genes were successfully clustered based on the magnitude relationship of FC values of 3 time series with a CA plot, which effectively visualizes the data of time course experiments. Pathogen-free 8-week-old male BALB/c mice were divided into 4 groups (control, 6, 12, and 24 h after injury: n=4 each). After nasal anesthesia of mice with isoflurane, the skin on the dorsal side of the left hind limb was shaved, and about a 1-cm incision was made on the skin using sterile straight stainless-steel scissors. Then, a 5 mm incision was made in the biceps femoris muscle, and then the skin incision was closed using a silk suture. At 6, 12, and 24 h after injury, a 3-mm thick injured muscle tissue sample (about 30 mg) with the injury in the center was excised. As a control sample, biceps femoris muscle was collected from an uninjured mouse that was euthanized without making the injury.