Gamma irradiation of human bone allografts alters medullary lipids and releases toxic compounds for osteoblast-like cells

The uncertainties about the transmission of prion proteins from xenogenic g rafts prepared from bovine bone has led to the reconsideration of allogenic bone as a grafting material. Allografting is a complementary technique to autografting nowadays when large bone volumes are necessary. Several prepar ation techniques have been proposed. Fresh-frozen, freeze-dried and gamma i rradiation are the most common. However, a large amount of lipids is presen t in the medullary spaces (near 70% in weight for a human femoral head). Th ey are known to strongly influence the biocompatibility of the bone graft. The exact changes of lipids upon the sterilization and storage processes ar e poorly known. The aims of the present study were to appreciate the effect s of gamma irradiation on medullary lipids and to identify the cytotoxicity of gamma-irradiated bank bone with/without lipid on cultures of osteoblast -like cells. Bone cores from 8 femoral heads retrieved during prosthesis su rgery for arthritis were prepared with a drilling trephine. Cores were eith er sterilized by gamma radiations (25000 gray) or kept frozen until lipid e xtraction and lipofuschine-like dosage by Folch's method and fluorometric s tudy. Peroxidated lipids appeared 2 to 3-fold higher in the gamma-irradiate d cores than in frozen ones; Slices were prepared from bone cores and were transferred on confluent osteoblast-like cell layers (Saos-2). The raw slic es (containing lipids) did not induce cell death. On the other hand, cell d eath was dramatically increased around the gamma-irradiated slices. Defatte d slices which had been sterilized by gamma radiations or UV did not induce cell death. Defatting procedures should be added when preparing bone allog rafts in human bone banks. (C) 2000 Elsevier Science Ltd. All rights reserv ed.