title: Validation of histologic changes induced by external irradiation in mandibular bone. An experimental animal model.
abstract: The present experimental study sought to determine the effect of high-dose irradiation on the rat mandible in order to establish an experimental model of radiogenic bone damage. The left mandibles of 20 adult Wistar rats were irradiated (single fraction 1500cGy, total dose 60Gy) by means of a hypofractionated stereotactic radiotherapy (hfSRT) over a period of 6 weeks. Follow-up was 6 weeks (group 1, n=10) and 12 weeks (group 2, n=10). The contralateral mandibles as well as 5 non-irradiated animals served as controls. Primary endpoints were fibrosis, loss of cell count, decreased immunohistochemical labelling for bone morphogenetic protein-2 (BMP-2) and osteocalcin as well as increased expression of transforming growth factor (TGF-beta). Cell loss, progressive fibrosis, and focal necrosis were detected in all irradiated sites. Quantitative measurement revealed 32.0+/-8.7% and 37.3+/-9.5% empty osteocyte lacunae for groups 1 and 2 resp., compared to 16.3+/-4.7% and 18.9+/-4.9% on the contralateral side and 7.9+/-1.7% for unirradiated controls (Mann-Whitney U test; p<.01). BMP-2 and osteocalcin labelling showed a marked decrease in irradiated and contralateral sides while TGF-beta was expressed strongly in irradiated sites only (for all p<.05). External hypofractionated irradiation with a total dose of 60Gy is feasible in rats and yields all histologic changes attributed to osteoradionecrosis (ORN) after a follow-up of 6 weeks. The irradiation protocol is suitable for an assessment of regenerative options in severe radiogenic bone damage. As a split mouth design entails major inaccuracies healthy animals have to be used as controls.
authors: Department of Oral and Maxillofacial Surgery, University of Erlangen-Nuremberg, Glueckstrasse 11, 91054 Erlangen, Germany. matthias.fenner@uk-erlangen.de
authors: Matthias
authors: M
authors: Fenner
authors: Jung
authors: J
authors: Park
authors: Norbert
authors: N
authors: Schulz
authors: Kerstin
authors: K
authors: Amann
authors: Gerhard G
authors: GG
authors: Grabenbauer
authors: Antje
authors: A
authors: Fahrig
authors: Juergen
authors: J
authors: Karg
authors: Joerg
authors: J
authors: Wiltfang
authors: Friedrich W
authors: FW
authors: Neukam
authors: Emeka
authors: E
authors: Nkenke
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D016022:Case-Control Studies; D004195:Disease Models, Animal; D019583:Dose Fractionation, Radiation; D007150:Immunohistochemistry; D008334:Mandible / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D010025:Osteoradionecrosis / Q000473:pathology*; D051381:Rats; D012015:Reference Standards; D018709:Statistics, Nonparametric
chemical_list: D055396:Bone Morphogenetic Protein 2