Armed Forces Radiobiology Research Institute, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20889.
Radiat Res. 2024 Jan 1;201(1):19-34. doi: 10.1667/RADE-23-00068.1.
The goal of this study was to establish a model of partial-body irradiation (PBI) sparing 2.5% of the bone marrow (BM2.5-PBI) that accurately recapitulates radiological/nuclear exposure scenarios. Here we have reported a model which produces gastrointestinal (GI) damage utilizing a clinical linear accelerator (LINAC) with precise dosimetry, which can be used to develop medical countermeasures (MCM) for GI acute radiation syndrome (ARS) under the FDA animal rule. The PBI model (1 hind leg spared) was developed in male and female C57BL/6 mice that received radiation doses ranging from 12-17 Gy with no supportive care. GI pathophysiology was assessed by crypt cell loss and correlated with peak lethality between days 4 and 10 after PBI. The radiation dose resulting in 50% mortality in 30 days (LD50/30) was determined by probit analysis. Differential blood cell counts in peripheral blood, colony forming units (CFU) in bone marrow, and sternal megakaryocytes were analyzed between days 1-30, to assess the extent of hematopoietic ARS (H-ARS) injury. Radiation-induced GI damage was also assessed by measuring: 1. bacterial load (16S rRNA) by RT-PCR on days 4 and 7 after PBI in liver, spleen and jejunum, 2. liposaccharide binding protein (LBP) levels in liver, and 3. fluorescein isothiocyanate (FITC)-dextran, E-selectin, sP-selectin, VEGF, FGF-2, MMP-9, citrulline, and serum amyloid A (SAA) levels in serum. The LD50/30 of male mice was 14.3 Gy (95% confidence interval 14.1-14.7 Gy) and of female mice was 14.5 Gy (95% confidence interval 14.3-14.7 Gy). Secondary endpoints included loss of viable crypts, higher bacterial loads in spleen and liver, higher LBP in liver, increased FITC-dextran and SAA levels, and decreased levels of citrulline and endothelial biomarkers in serum. The BM2.5-PBI model, developed for the first time with precise dosimetry, showed acute radiation-induced GI damage that is correlated with lethality, as well as a response to various markers of inflammation and vascular damage. Sex-specific differences were observed with respect to radiation dose response. Currently, no MCM is available as a mitigator for GI-ARS. This BM2.5-PBI mouse model can be regarded as the first high-throughput PBI model with precise dosimetry for developing MCMs for GI-ARS under the FDA animal rule.
本研究的目的是建立一种部分身体照射（PBI）模型，该模型可保留 2.5%的骨髓（BM2.5-PBI），准确再现放射性/核辐射暴露情况。在这里，我们报告了一种模型，该模型利用精确的剂量学使用临床直线加速器（LINAC）产生胃肠道（GI）损伤，可用于根据 FDA 动物规则开发 GI 急性辐射综合征（ARS）的医疗对策（MCM）。在未接受支持性护理的情况下，雄性和雌性 C57BL/6 小鼠接受了 12-17 Gy 的辐射剂量，建立了 PBI 模型（1 条后腿保留）。通过隐窝细胞丢失评估 GI 病理生理学，并与 PBI 后第 4 天至第 10 天的峰值致死率相关联。通过概率分析确定导致 30 天内 50%死亡率（LD50/30）的辐射剂量。在第 1 天至第 30 天之间分析外周血中的差异血细胞计数、骨髓中的集落形成单位（CFU）和胸骨巨核细胞，以评估造血 ARS（H-ARS）损伤的程度。还通过以下方法评估辐射诱导的 GI 损伤：1. 在 PBI 后第 4 天和第 7 天通过 RT-PCR 测量肝脏、脾脏和空肠中的 16S rRNA 细菌负荷，2. 测量肝脏中的脂多糖结合蛋白（LBP）水平，3. 测量血清中的荧光素异硫氰酸酯（FITC）-葡聚糖、E-选择素、sP-选择素、VEGF、FGF-2、MMP-9、瓜氨酸和血清淀粉样蛋白 A（SAA）水平。雄性小鼠的 LD50/30 为 14.3 Gy（95%置信区间为 14.1-14.7 Gy），雌性小鼠的 LD50/30 为 14.5 Gy（95%置信区间为 14.3-14.7 Gy）。次要终点包括有活力的隐窝丢失、脾脏和肝脏中的细菌负荷增加、肝脏中的 LBP 增加、血清中的 FITC-葡聚糖和 SAA 水平升高以及内皮生物标志物瓜氨酸和血清中的水平降低。首次使用精确剂量学开发的 BM2.5-PBI 模型显示出与致死率相关的急性辐射诱导的 GI 损伤，以及对各种炎症和血管损伤标志物的反应。观察到与辐射剂量反应有关的性别特异性差异。目前，尚无作为 GI-ARS 缓解剂的 MCM。这种 BM2.5-PBI 小鼠模型可被视为根据 FDA 动物规则开发 GI-ARS 的第一个具有精确剂量学的高通量 PBI 模型。
