Background. We aimed to explore (i) the short-term retention of intramedullary implanted mesenchymal stem cells BMSCs and (ii) their impact on the bone blood flow and metabolism in a rat model of hindlimb irradiation. Methods. Three months after 30 Gy irradiation, fourteen animals were referred into 2 groups: a sham-operated group (n = 6) and a treated group (n = 8) in which 111In-labelled BMSCs (2 × 106 cells) were injected in irradiated tibias. Bone blood flow and metabolism were assessed by serial 99mTc-HDP scintigraphy and 1-wk cell retention by recordings of 99mTc/111In activities. Results. The amount of intramedullary implanted BMSCs was of 70% at 2 H, 40% at 48 H, and 38% at 168 H. Bone blood flow and bone metabolism were significantly increased during the first week after cell transplantation, but these effects were found to reduce at 2-mo followup. Conclusion. Short-term cell retention produced concomitant enhancement in irradiated bone blood flow and metabolism.

Abstract. radiotherapy is successfully used to treat neoplastic lesions, but may adversely affect normal tissues within the irradiated volume. however, additional clinical and para-clinical data are required for a comprehensive understanding of the pathogenesis of this damage. We assessed a rat model using clinical records and medical imaging to gain a better understanding of irradiation-induced tissue damage. the hindlimbs of the rats in this model were irradiated with a single dose of 30 or 50 Gy. Sequential analysis was based on observation records of stage and planar scintigraphy. additional radiography, radiohistology and histology studies were performed to detect histological alterations. all animals developed acute and late effects, with an increased severity after a dose of 50 Gy. the bone uptake of 99m Tc-HDP was significantly decreased in a dose-and time-dependent manner. Histologically, significant tissue damage was observed. after the 50 Gy irradiation, the animals developed lesions characteristic of osteoradionecrosis (Orn). radiographic and histological studies provided evidence of lytic bone lesions. Our rat model developed tissue damage characteristic of radiation injury after a single 30 Gy irradiation and tissue degeneration similar to that which occurs during human Orn after a 50 Gy irradiation. the development of this animal model is an essential step in exploring the pathogenesis of irradiation-induced tissue damage, and may be used to test the efficacy of new treatments. Introductionradiotherapy is successfully used to treat regional neoplastic lesions, but may have an adverse effect on normal tissues. irradiated tissue abnormalities include the impairment of vascularization (1-3) due to the high vulnerability of small vascular endothelial cells, impairment of cell homeostasis with cellular apoptosis (3-6), and the accumulation of fibrosis (5,7). Bone tissue is very vulnerable to irradiation (8,9) and undergoes impaired healing, infection, atrophy, pathological fractures and bone tissue necrosis, termed osteoradionecrosis (Orn), within the irradiated region. these iatrogenic delayed complications occur in various anatomic sites, including the pelvis, sternum, vertebrae, clavicle, femoral head and, in particular, the mandible. the most devastating radiotherapyinduced complications of the head and the neck occur in the mandible, and in some cases require surgical resection (10). the reported incidence of Orn following conventional radiotherapy (rt) to the mandible ranges between 0.9 and 35% (11), with an increased risk at doses exceeding 60 Gy (12).due to the increased use of radiation therapy alone or in combination with chemotherapy in the treatment of head and neck malignancies (13,14), it is likely that the number of radio-induced complications will rise (14-16).despite increased interest in the clinical development of ORN along with a new proposed definition and classification (17), most animal model studies on Orn date from the 1960-70s (18-20). Since then, imaging techniques have evolv...

No abstract