Bioluminescence imaging of luciferase-expressing bone marrow stromal cells. (a) Representative bioluminescence imaging (BLI) for a control group that received biphasic calcium phosphate (BCP) alone on their left dorsal side and subcutaneous (SC) injections of bone marrow stromal cells (BMSCs) on their right dorsal side, and the experimental group that received subcutis implantations of BCP + BMSCs. (b) The BLI signal, expressed as counts per minute (cpm), decreased after transplantation, while BCP dampened the BLI signal. (c) When the number of remaining cells compared with the number of initially transplanted cells was expressed at each time point, SC implantation of BCP + BMSCs was significantly higher from day 8 onwards compared with the SC injections group (aP <0.01). Approximately 1.5% of the initial number of transplanted cells in the SC BCP + BMSCs group remained at day 37.