Low-dose nicotine reduces the homing ability of murine BMSCs during fracture healing

Wound and fracture healing are affected by exposure to nicotine and other compounds in cigarettes. This study examined the effects of exposure to low-dose nicotine at sub-toxic concentrations on the proliferation, differentiation and migration of bone marrow stem cells (BMSCs) in vitro and their homing to fracture site in C57BL/6 mice. BMSCs were investigated in cells treated with or without nicotine (1 mu M to 1 mM). Different concentrations of nicotine exhibited varied effects on BMSCs growth regulation and bone differentiation. CCK8 test significantly increased at a high nicotine concentration of 1 mM while calcium nodule staining with Alizarin red decreased at the same concentration. In vitro scratch test, Transwell tests and in vivo BMSCs homing tests showed negative effects on BMSCs migration at 10 mu M to 1 mM nicotine test. Real-time PCR analysis revealed the down-regulation of SDF-1, CXCR4 and CXCR7, which were members of the potent chemotactic signaling system. Western blot analysis indicated the down-regulated expression levels of periostin expressed by nicotine-treated osteoblasts (1 mu M to 100 mu M). Micro CT results showed that nicotine delayed the fracture healing in mice. Our data suggest that exposure to low-dose nicotine concentrations may affect bone formation by inhibiting the migration and homing of BMSCs, which may be an important risk factor for bone healing delay in smoking patients.