Assessment and refinement of intra-bone marrow transplantation in mice

Intra-bone marrow transplantation (IBMT) may improve the seeding efficiency of transplanted hematopoietic stem cells compared to the routinely used intravenous injection. Current IBMT protocols are optimized for ease of use and to improve experimental results. However, there have been no investigations to assess the impact of IBMT on animal welfare. Here, we report the results of pain assessment after IBMT and the effects of refinements to the current standard procedure. IBMT was performed in either the tibia or the femur of a recipient mouse under general anesthesia. Impact was determined using clinical scoring of different parameters (lameness, grip capacity, body weight loss, footprint analysis), behavioural tests (burrowing, open-field), monitoring of stress hormones and post-mortem histology. The results revealed that IBMT definitely induces severe post-operative distress. Although IBMT in the tibia is technically easier, the degree of impairment and the distress observed were consistently higher than for transplantation in the femur. A refinement for IBMT in the tibia was achieved by using 30- instead of 26-gauge needles and by sparing the patellar tendon. Consequently, for IBMT, we recommend either using the femur, or if the tibia is required due to its better feasibility, using our refined protocol. Furthermore, IBMT should definitely be limited to one leg per animal.