Osteoradionecrosis of the jaw (ORNJ) is an infrequent yet potentially devastating complication of head and neck radiation therapy. Low-intensity pulsed ultrasound (LIPUS) has been widely accepted as a promising method for the successful management of ORNJ, but the mechanism remains unclear. In this study, the effects of LIPUS on cytoskeletal reorganization, cell viability, and osteogenic differentiation capacity of rat mandible-derived bone marrow mesenchymal stem cells (M-BMMSCs) induced by radiation were determined by immunofluorescence staining, CCK-8 cell proliferation assay, quantification of alkaline phosphatase (ALP) activity, alizarin red staining, and real-time RT-PCR, respectively. Moreover, the involvement of the RhoA/ROCK signaling pathway underlying this process was investigated via western blot analysis. We found that radiation induced significant damage to the cytoskeleton, cell viability, and osteogenic differentiation capacity of M-BMMSCs and downregulated their expression of RhoA, ROCK, and vinculin while increasing FAK expression. LIPUS treatment effectively rescued the disordered cytoskeleton and redistributed vinculin. Furthermore, the cell viability and osteogenic differentiation capacity were also significantly recovered. More importantly, it could reverse the aberrant expression of the key molecules induced by radiation. Inhibition of RhoA/ROCK signaling remarkably aggravated the inhibitory effect of radiation and attenuated the therapeutic effect of LIPUS. In the light of these findings, the RhoA/ROCK signaling pathway might be a promising target for modifying the therapeutic effect of LIPUS on osteoradionecrosis.

中文翻译：

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低强度脉冲超声调节大鼠下颌骨髓间充质干细胞的RhoA / ROCK信号，以恢复其辐射损伤的细胞骨架和细胞生物学功能。

颌骨骨放射性坏死（ORNJ）是头颈部放射治疗的一种罕见但可能具有破坏性的并发症。低强度脉冲超声（LIPUS）已被广泛接受为成功治疗ORNJ的有前途的方法，但机制尚不清楚。在这项研究中，通过免疫荧光染色，CCK-8细胞增殖试验确定了LIPUS对辐射诱导的大鼠下颌骨来源的骨髓间充质干细胞（M-BMMSC）的细胞骨架重组，细胞活力和成骨分化能力的影响，定量碱性磷酸酶（ALP）活性，茜素红染色和实时RT-PCR。此外，通过蛋白质印迹分析研究了该过程背后的RhoA / ROCK信号通路的参与。我们发现辐射诱导M-BMMSCs的细胞骨架，细胞活力和成骨分化能力受到明显损害，并在增加FAK表达的同时下调了它们的RhoA，ROCK和纽蛋白表达。LIPUS治疗有效地拯救了紊乱的细胞骨架并重新分配了纽蛋白。此外，细胞活力和成骨分化能力也被显着恢复。更重要的是，它可以逆转辐射诱导的关键分子的异常表达。RhoA / ROCK信号的抑制作用显着加重了放射线的抑制作用，并减弱了LIPUS的治疗作用。根据这些发现，RhoA / ROCK信号通路可能是修饰LIPUS对骨放射性坏死的治疗效果的有希望的目标。