Transplanted BMSCs participated in osseointegration after implantation. (A) Immunohistochemical staining demonstrated that, 7 days after surgery, luciferase, BSP, and GFP activity could be detected in the newly formed bone area. Three wks after surgery, expressions of luciferase, BSP, and GFP were much weaker. (B) The percentage of luciferase-positive cells relative to GFP-positive cells, which demonstrated the amount of transplanted BMSCs undergoing osteogenic differentiation, decreased from 88.9% at day 7 to 26% at day 21 after implantation. The percentage of BSP-positive cells also decreased from 78.6% at 7 days post-operatively to 24.3% at 21 days post-operatively. Data are presented as means ± SE (n = 7). *p < 0.05, 1w vs. 3w; **p < 0.05, luciferase (%)/GFP (%) vs. BSP (%). (C) GFP-positive cells (total transplanted BMSCs) constituted 62.5% of the cell population at day 7 post-operatively. This percentage decreased slightly thereafter to 59.4%. Data are presented as means ± SE (n = 7). *p < 0.05, 1w vs. 3w.