Cannabinoid receptor type 2 is time-dependently expressed during skin wound healing in mice

Dynamic localization of CB2R and quantitative analysis of CB2R mRNA during skin wound healing in mice were performed. Co-localization of CB2R with F4/80 or alpha-SMA was detected by double-color immunofluorescence microscopy. A total of 110 male mice were divided into control, injury, and postmortem groups. Sixty-five mice were sacrificed, followed by sampling at 0.5 h-21 days post-injury. Five mice without incision were used as control. The other 40 mice that received incised wound were sacrificed at 5 days after injury. The samples were collected at 0 h-3 days postmortem. In the uninjured controls, CB2R immunoreactivity was detected in the epidermis, hair follicles, sebaceous glands, dermomuscular layer, and vascular smooth muscle. In the incision groups, polymorphonulcear cells, macrophages, and myofibroblasts showed positive staining for CB2R. Morphometrically, the average ratios of CB2R-positive cells were more than 50 % at 5 days post-wounding, whereas it was < 50 % at the other posttraumatic intervals. The average ratios of CB2R-positive macrophages maximized at 3 days post-wounding, and the average ratios of CB2R-positive myofibroblasts peaked at 5 days post-wounding. The relative quantity of CB2R mRNA expression maximized at posttraumatic 5 days in comparison with control as detected by real-time PCR, with an average ratio of > 4.10, which was also confirmed by Western blotting. There was no significant change for CB2R protein within 6 h postmortem and for mRNA within 3 h postmortem as compared with the control group. In conclusion, dynamic distribution and expression of CB2R suggest that CB2R is involved in modulating macrophages and myofibroblasts in response to inflammatory event and repair process in mouse skin wound healing, and CB2R is available as a marker for wound age determination.