Bone microarchitecture and turnover in the irradiated human mandible

Abstract

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Osteocyte Apoptosis, Bone Marrow Adiposity, and Fibrosis in the Irradiated Human Mandible

“…The increased adipocytes (shown in this study) and the reduced presence of osteoblastic activity (demonstrated in a previous study 27 ) that is observed in irradiated human mandibles together with absent osteocytes (shown in this study) and osteoclasts (demonstrated in a previous study 27 ) lead to the hypothesis that irradiation disrupts bone homeostasis at different levels. Radiation causes early death of osteocytes, persistent suppression of osteoclastogenesis by lack of signaling from osteocytes and osteoblasts, as well as deprivation of osteoclast precursors, leading to persistence of fragile bone matrix void of osteocytes.…”

“… 2 , 25 , 26 In human irradiated mandibles, a significant reduction as well as an absence of osteoclasts is observed. 27 , 28 , 29 The bone samples in human studies were derived from resections of osteoradionecrotic lesions 28 , 29 and from trephine biopsies taken during implant surgery in irradiated bone, 27 which represents bone harvested months to years after radiation therapy and captures the “late stage” radiation injury. As osteocyte apoptosis is thought to recruit osteoclasts to areas in need of bone resorption, perhaps the early radiation-induced apoptotic osteocyte death induces an initial increased osteoclast recruitment.…”

“… 28 , 29 The persistent presence of empty lacunae in irradiated bone, even many years after irradiation, could in part be due to the absence of osteoclasts, which leads to the preservation of mineralized matrix that should have been resorbed. 27 …”

“…In a previous study, mandibular bone samples from irradiated patients and healthy edentulous patients were compared, and no significant difference in bone volume and bone mineral density was observed between the groups. 27 …”

Irradiation Induced Biochemical Changes in Human Mandibular Bone: A Raman Spectroscopic Study

“…The histological, microstructural, and vascular alterations in irradiated human mandibular bone have been previously described. 22,23 However, very few Raman spectroscopic studies 7,15 focusing on changes in the irradiated human mandibular bone are reported. Some studies have been performed on radiated animal bone tissues 8,12,13,18 but these data are difficult to compare with human bone as the dosage, type of radiation, and nature of bone tissue are different and the time interval of biopsy from irradiation is usually less.…”