Bystander effect induced changes in apoptosis related proteins and terminal differentiation in in vitro murine bladder cultures

Purpose: Radiation-induced bystander effects are now an established phenomenon seen in numerous cell and tissue culture models. The aim of this investigation was to examine the bystander signal and response in a multicellular primary tissue culture system in vitro. Methods and materials: Murine bladder samples were explanted and directly exposed to gamma radiation, or treated with irradiated tissue conditioned medium (ITCM) generated from the directly irradiated cultures. Results: Results indicated that there was a strong bystander signal produced by the tissue that caused both dose-dependent and -independent changes in the ITCM treated tissue. Significantly increased B-cell lymphoma 2 (Bcl2) expression was noted after treatment with 0.5Gy and 5Gy ITCM (approximately 80%), while dose-dependent changes were observed in c-myelocytomatosis (cMyc) (39.48% at 0.5 Gy ITCM, 81.28% at 5 Gy ITCM) and the terminal differentiation marker uroplakin III (17.88% at 0.5 Gy). Nuclear fragmentation was also significantly increased at both doses of ITCM. Conclusion: These data suggest that the bystander signal produced in a multicellular environment induces complex changes in the ITCM-treated culture, and that these changes are reflective of a coordinated response to maintain integrity throughout the tissue.