Preservation of immunoexpression of type I collagen, BSP and BMP4 in the dentin-pulp complex of head and neck cancer patients after radiotherapy

Abstract This study tested the hypothesis that head and neck radiotherapy (HNRT) impacts the immunoexpression of type I collagen, bone sialoprotein (BSP) and bone morphogenetic protein 4 (BMP4), thereby leading to micromorphological changes in the dentin-pulp complex (DPC), and promoting the onset and progression of radiation caries (RC). Twenty-two demineralized sections of carious teeth (a group of 11 irradiated teeth and a control group of 11 non-irradiated teeth) extracted from 19 head and neck cancer patients were analyzed by conventional optical microscopy and immunohistochemistry to investigate the micromorphology (cellular layer hierarchy, blood vessels, odontoblasts, fibroblasts, extracellular matrix, calcification, necrosis, reactionary dentin formation, and chronic inflammation), and the patterns of staining/immunolocalization of type I collagen, BSP and BMP4 in the dental pulp of irradiated and control samples. No significant differences attributable to the direct impact of radiotherapy were detected in DPC micromorphology between the groups. In addition, the patterns of immunohistochemical staining and immunolocalization of the proteins studied did not differ between the irradiated and the control samples for type I collagen, BSP or BMP4. This study rejected the hypothesis that HNRT directly damages dentition by changing the organic components and the microstructure of the DPC, ultimately leading to RC.

摘要 本研究验证了如下假说：头颈部放射治疗（Head and Neck Radiotherapy, HNRT）会影响I型胶原、骨唾液蛋白（Bone Sialoprotein, BSP）及骨形态发生蛋白4（Bone Morphogenetic Protein 4, BMP4）的免疫表达，进而引发牙本质牙髓复合体（Dentin-Pulp Complex, DPC）的微观形态改变，并促进放射性龋（Radiation Caries, RC）的发生与进展。本研究纳入19名头颈部癌症患者拔除的龋坏牙齿脱矿切片共22份，其中放射照射组11份、非照射对照组11份，通过常规光学显微镜术与免疫组织化学法，分析照射组与对照组牙髓组织的微观形态（包括细胞层层级、血管、成牙本质细胞、成纤维细胞、细胞外基质、钙化、坏死、反应性牙本质形成及慢性炎症），以及I型胶原、BSP与BMP4的染色模式与免疫定位特征。结果显示，两组间牙本质牙髓复合体的微观形态未出现可归因于放射治疗直接影响的显著差异；此外，针对I型胶原、BSP及BMP4，照射组与对照组的免疫组织化学染色模式及免疫定位特征均无明显差异。本研究推翻了“头颈部放射治疗通过改变牙本质牙髓复合体的有机成分与微观结构直接损伤牙列，最终引发放射性龋”这一假说。