Immunohistochemistry Evaluation of Bone Formation of Gamma Irradiated Bone Graft Innude Rat

Introduction Banked allogeneic bone grafts have been used widely in clinic for the repair of bone defects. Massive allografts are thought to function through an osteoconductive pathways, demineralized bone was reported to be osteoinductive. Morselized allograft which has been used to fill bony defects in revision arthroplasty to fulfill a mechanical role, as well as to provide a scaffold for new bone formation has yet to be elucidated the potentiality of osteoinductive function. Infections and disease transmissions due to the usage of allograft tissues have motivated careful procurement and sterilization processing in bone graft banking. Secondary sterilization is required to limit disease transmission and contamination. Gamma irradiation is a widely accepted secondary sterilization procedure. A dose of 20 kGray or higher has been reported to alter the mechanical properties of bone. The effect of gamma irradiation on in vivo biological properties of morselized allograft bone has not been well reported. Our previously study found a negative dose-dependent effect of gamma irradiation on bone formation and remodeling of morselized human bone grafts in nude rat defect model [1]. A statistically significant decrease in new bone formation was found in the defect packed with the morselized grafts treated with 25 kGray gamma irradiation when compared with the 0 and 15 kGray groups. Evidence of osteoinductivity was found only in the defects packed with zero or low dose treated grafts. This study focused on the mechanism investigation by testing the expression and distribution of bone morphogenetic protein (BMP) 7 which is a growth factor produced mainly by osteoblast , core binding factor α1 (CBFA1) which is a transcription factor governing osteoblast differentiation, and proliferating cell nuclear antigen (PCNA) which is a cell proliferating marker.