Abstract 16

Expression of growth factors in nude rat bone defects treated with gamma irradiated human bone grafts

JB Chen, Y. Yu, QJ Li, *D.A.F. Morgan and W.R. Walsh

Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Sydney
*Queensland Bone Bank, Holy Spirit Hospital, Brisbane

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. Gamma irradiation is a widely accepted secondary sterilization procedure. The effect of gamma irradiation on 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 of morselized human bone grafts in nude rat defect model. Evidence of osteoinductivity was found in the defects packed with zero or low dose treated grafts. This study focused on mechanism investigation by testing the expression and distribution of bone morphogenetic protein (BMP) 7, core binding factor a1 (CBFA1) and proliferating cell nuclear antigen (PCNA).

CBFA1 and BMP7 stained mainly the osteoblasts and some mesenchymal like cells lining around the intact cortex, the new bones adjacent to the host cortex bridged by the implanted grafts and in the loose connective tissue far from the host bone. A negative correlation of immunostaining of CBFA1 and BMP7 and gamma irradiation was presented by quantitative analysis. The low bone formation rate in the high dose gamma irradiation group (25 kGy) may due to the less expression of BMP7 and/or CBFA1.

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