Comparison of murine retroorbital plexus and facial vein blood collection to mitigate animal ethics issues

BACKGROUND: Blood collection is an important procedure used in animal experiments. Blood collection methods that reduce pain, injury, and stress in experimental animals are important with regard to animal ethics. Various comparative studies of blood collection methods have been reported; however, there are no comparative studies on serial blood collection considering animal ethics. To suggest simple methods that minimize pain during serial blood collection, we compared the retroorbital plexus (RP) and facial vein (FV) blood collection methods performed by both experienced and novice groups. The experienced and novice groups collected up to 0.4 mL of blood via the RP and FV methods every second day for 2 weeks. After blood collection, all mice were evaluated by corticosterone concentrations for stress, hematological, immunological, and histological analyses. RESULTS: We found that the FV methods reduced the collection time, pain, distress, tissue damage and lasting harms without anesthesia. Corticosterone concentrations in the peripheral blood were decreased in mice subjected FV methods compare with those subjected to RP methods. The proportion of granulocytes and monocytes, such as macrophages in the peripheral blood and spleen, was decreased in mice subjected to FV methods compared with that in mice subjected to RP methods in both experienced and novice groups. White blood cells were infiltrated in RP areas with severe tissue damage and inflammation. CONCLUSIONS: With respect to animal ethics, we suggest that the FV method, a simple and fast technique that can easily be performed by both experienced and novice researchers, is suitable for serial blood collection.