Radiation protocols determine acute graft-versus-host disease incidence after allogeneic bone marrow transplantation in murine models

Purpose:?Effects of radiation sources used for total body irradiation (TBI) on Graft-versus-Host Disease (GvHD) induction were examined.

Materials and methods:?In a T cell receptor (TCR) transgenic mouse model, single fraction TBI was performed with different radiation devices (⁶⁰Cobalt; ¹³⁷Cesium; 6 MV linear accelerator), dose rates (0.85; 1.5; 2.9; 5 Gy/min) and total doses before allogeneic bone marrow transplantation (BMT). Recipients were observed for 120 days. Different tissues were examined histologically.

Results:?Acute GvHD was induced by a dose rate of 0.85 Gy/min (⁶⁰Cobalt) and a total dose of 9 Gy and injection of 5×10⁵ lymph node cells plus 5×10⁶ bone marrow cells. Similar results were obtained using 6 MV linear accelerator- (linac-) photons with a dose rate of 1.5 Gy/min and 0.85 Gy/min, a total dose of 9.5 Gy and injection of same cell numbers. TBI with ¹³⁷Cesium (dose rate: 2.5 Gy/min) did not lead reproducibly to lethal acute GvHD.

Conclusions:?Experimental TBI in murine models may induce different immunological responses, depending on total energy, total single dose and dose rate. GvHD might also be induced by TBI with low dose rates.     

淡豆豉提取物对急性辐射损伤小鼠的保护作用研究

目的研究淡豆豉提取物对6Gy的^60Coγ辐射损伤小鼠的保护作用。方法6Gy的^60Coγ全身性照射小鼠造模,小鼠灌胃给予0．5％CMC—Na为溶媒配制的阳性对照药尼尔雌醇和淡豆豉提取物的混悬液28d,每天1次,照射前后分别连续灌胃给药14d;血细胞分析仪检测白细胞、红细胞、血小板等血液学指标,称取小鼠体质量,脾脏和胸腺质量;透射电子显微镜观察小鼠脾脏、胸腺、小肠和睾丸的超微结构。结果淡豆豉提取物能明显减轻^60Coγ射线引起的小鼠外周血白细胞、红细胞、血小板等指标的减少和体质量减轻,显著提高股骨骨髓有核细胞数,明显改善辐射受损的脾脏、胸腺、小肠和睾丸的超微结构和增加萎缩的胸腺、脾脏等指数。结论淡豆豉提取物对低剂量^60Coγ辐射损伤小鼠具有明显的保护作用。     

G-CSF和IL-6联合应用协同促进受照小鼠造血功能恢复的实验研究

目的 探讨G-CSF和IL-6联合应用协同促进受辐射小鼠造血功能恢复的作用及机理。方法 采用F800血细胞自动计数仪计数红细胞、白细胞、血小板和血红蛋白等指标。常规法进行骨髓集落培养、内源性脾结节计数。琼脂糖电泳方法检测骨髓细胞程序性死亡。结果 G-CSF和IL-6联合应用促进受辐射小鼠外周血细胞的恢复, 促进脾脏内源性脾结节的形成, 增加骨髓细胞含量和促进骨髓细胞GM-CFU的形成, 提高受辐射小鼠的生存率。结论 G-CSF和IL-6联合应用的效果优于单用的效果, 其促进辐射后机体造血功能恢复的机理是通过刺激骨髓残余造血干细胞的恢复, 该过程需要一段较长的时间, 而不是通过抑制照后即刻骨髓细胞的程序性死亡。     

低剂量照射对小鼠骨髓移植造血功能的影响

目的探讨低剂量照射促进小鼠骨髓移植后受体造血功能的重建。方法通过对小鼠体外骨髓细胞进行不同剂量的照射，用^3H-TdR掺入法确定产生最佳刺激增殖效应的照射剂量。在骨髓移植前，对供体小鼠骨髓细胞给予最佳刺激剂量的照射，然后将被照射的骨髓细胞输入受体小鼠内，最后动态监测受体小鼠的外周血细胞和骨髓单个核细胞数量。结果在离体情况下，经6和8cGy低剂量照射的小鼠骨髓细胞增殖能力明显增强。用低剂量照射的骨髓细胞进行骨髓移植后，受体小鼠骨髓单个核细胞数和外周血细胞计数普遍高于相应的对照组。结论低剂量照射可能促进小鼠骨髓移植后受体造血功能的重建。     

Icariin protects against radiation-induced mortality and damage in vitro and in vivo

Abstract

Purpose: The present study aimed to investigate the potential protective effects of icariin both in vivo and in vitro, an active flavonoid glucoside derived from medicinal herb Epimedium, and its possible mechanisms against radiation-induced injury.

Methods: Male C57BL/6 mice were exposed to lethal dose (7?Gy) or sub-lethal dose (4?Gy) of whole body radiation by X-ray at a dose rate of ～0.55?Gy/min, and icariin was given three times at 24?h and 30?min before and 24?h after the irradiation. After irradiation, hematological, biochemical, and histological evaluations were performed. We further determined the effect of icariin on radiation-induced cytotoxicity and changes in apoptosis-related protein expression.

Results: Icariin enhanced the 30-day survival rates (20 and 40?mg/kg) in a dose-dependent manner, and protected the radiosensitive organs such as intestine and testis from the radiation damages. Moreover, hematopoietic damage by radiation was significantly decreased in icariin-treated mice as demonstrated by the increases in number of peripheral blood cells, bone marrow cells (1.7-fold), and spleen colony forming units (1.7-fold). In addition, icariin decreased the radiation-induced oxidative stress by modulating endogenous antioxidant levels. Subsequent in vitro studies showed that icariin effectively increased cell viability (1.4-fold) and suppressed the expression of apoptosis-related proteins after irradiation.

Conclusion: These results suggest that icariin has significant protective effects against radiation-induced damages partly through its anti-oxidative and anti-apoptotic properties.     

Radiation and Haematopoiesis in Harwell Steel Mice

Summary

Haematological information on steel (Sl) mice is limited largely to Sl/Sld mice of Bar Harbor stock (WC.B6 F₁). Therefore, two Harwell alleles, SlgbH and Slcon, were investigated. In the steady state both heterozygotes were modestly anaemic, homozygous Slcon and compound Sl^con/Sl^gbH more so. On perturbation by X-irradiation Sl^con/Sl^gbH showed a decrease in median lethal dose (MLD)–6·5 Gy, Slcon/+ and Slcon/Slcon slightly less change (7.5 Gy) compared with +/+, 8 Gy. In recovery from sublethal doses single heterozygotes, double heterozygotes with Wv, and compounds showed no delay in restoration of the count of red blood corpuscles (RBC) such as that seen in typical W mice (e.g. Wv/+, W/Wv). Effects on Slcon/Slcon and Sl^con/Sl^gbH differ from those reported for Sl/Sld in that (1) they show normal growth of spleen colonies when used as lethally irradiated recipients of bone marrow, (2) they support growth of implanted bone marrow to form radiation chimaeras. When Harwell steel mice are donors of bone marrow to lethally irradiated +/+ mice the chimaeras ultimately are not anaemic; when lethally irradiated Harwell steel mice are recipients of +/+ marrow they remain macrocytically anaemic.

One deduces that, for normal development and production of normal RBC in the steady state, the erythron requires intrinsic factors determined by wild type alleles at the W locus and extrinsic factors determined by wild type alleles at the Sl locus. Mutant alleles at either locus may determine macrocytosis. Two mutant alleles at either locus are still more deleterious, often lethal. Whereas mutant W alleles may also influence the pluripotent haematopoietic stem cell (HSC) leading to reduced MLD on X-irradiation, a similarly reduced MLD for Sl mutants may represent an increased need for and consumption of products of the haematopoietic stem cells rather than truly increased radiosensitivity, since the D_o for spleen colony-forming units is the same for Sl^con/Sl^gbH as +/+ mice.     

Hematological aftermath of the radiation accident in Istanbul

Purpose: The effects of radiation exposure are long-lasting. Long-term monitoring is imperative to diagnose late effects and improve our far-sightedness about possible events in the future. A radiation accident occurred in Istanbul in 1998 that resulted in mild to moderate acute radiation syndrome (ARS). In this study we aimed to investigate the changes in hematological parameters at the long-term follow-up of ARS patients.

Methods: Ten adults were hospitalized after exposure to a 60Co source. Seven were diagnosed as having ARS and had severe and symptomatic pancytopenia. All of the exposed people recovered following intensive treatment. Treatment was supportive with transfusion, granulocyte-colony stimulating factor, and anti- infective management covering antifungal agents. Patients were closely monitored. Nine years after the accident, the initial and follow-up complete blood count examinations and peripheral blood smears (PBS) were comparatively evaluated by an experienced hematologist. The hematological laboratory values of the patients on admission, after treatment, and nine years after the accident were documented and compared.

Results: Biodosimetric analysis revealed that whole-body doses ranged from 1–1.9 Gy. All subjects have shown complete recovery of the hematological laboratory values after treatment. All but one of the subjects showed complete blood cell recovery. The improvement of the blood cell count of the excepted patient stalled at a mildly reduced level and his bone marrow was still hypocellular nine years after the accident; however, no malignant changes were detected. Values at admission were significantly different compared with post treatment and present values of all patients. Post treatment and follow-up values were similar. One of the patients died of lung cancer. None of the patients developed hematological malignancy.

Conclusions: In this study, the recovery from ARS was complete after treatment. The small population, short follow-up period, and the relatively small doses resulted in no long-term adverse effects, as would be predicted.     

Engraftment of bone marrow-derived cells after nonlethal radiation in syngeneic C57BL/6 mice

Objective To study the characteristics of cell engraftment in mice at a lower dose under nonlethal radiated condition.Methods A syngeneic C57BL/6 mouse model,transplanted with 1 × 107 bone marrow cells...     

Induction of Cytogenetic Adaptive Response of Somatic and Germ Cells in Vivo and in Vitro by Low-dose X-irradiation

Summary

The cytogenetic adaptive response induced by low-level radiation was studied using human and rabbit lymphocytes in vitro and bone marrow cells and germ cells in vivo. The inductive dose of X-rays was 10 mGy for the in vitro studies at a dose rate of 10 mGy/min, and 2, 10, 50, 75 and 100 mGy for the in vivo studies at a dose rate of 50 mGy/min. The challenging dose was 1·5 Gy X-rays for the in vitro experiments and 0·65 or 0·75 Gy for the in vivo experiments at a dose rate of 0·44 Gy/min. The results reported here, in addition to those that have appeared in the literature, show the following characteristics documented for the first time: (1) 10 mGy could induce the adaptive response in human as well as rabbit lymphocytes irradiated not only in G₁, S and G₂ phases, but also in the G₀ state; (2) although the induced adaptive response could only last three cell cycles, it could be revived when the inductive dose was repeated after the third cell cycle; (3) the adaptive response could be induced by low-dose X-rays in somatic cells, both in vitro (lymphocytes) and in vivo (bone marrow cells), and also in germ cells (spermatocytes); (4) the magnitude of the adaptive response induced by whole-body irradiation was found to be dose-dependent–the lower the inductive dose the more the reduction of the frequency of chromatid aberrations following the challenging dose.     

Phase I/II 90Y-Zevalin (yttrium-90 ibritumomab tiuxetan, IDEC-Y2B8) radioimmunotherapy dosimetry results in relapsed or refractory non-Hodgkin’s lymphoma

Dosimetry studies in patients with non-Hodgkin’s lymphoma were performed to estimate the radiation absorbed dose to normal organs and bone marrow from ⁹⁰Y-Zevalin (yttrium-90 ibritumomab tiuxetan, IDEC-Y2B8) treatment in this phase I/II, multicenter trial. The trial was designed to determine the dose of Rituximab (chimeric anti-CD20, Rituxan, IDEC-C2B8, MabThera), the unlabeled antibody given prior to the radioconjugate to clear peripheral blood B cells and optimize distribution, and to determine the maximum tolerated dose of ⁹⁰Y-Zevalin [7.4, 11, or 15 MBq/kg (0.2, 0.3, or 0.4 mCi/kg)]. Patients received ¹¹¹In-Zevalin (indium-111 ibritumomab tiuxetan, IDEC-In2B8 ) on day 0 followed by a therapeutic dose of ⁹⁰Y-Zevalin on day 7. Both doses were preceded by an infusion of the chimeric, unlabeled antibody Rituximab. Following administration of ¹¹¹In-Zevalin, serial anterior/posterior whole-body scans were acquired. Major-organ radioactivity versus time estimates were calculated using regions of interest. Residence times were computed and entered into the MIRDOSE3 computer software program to calculate estimated radiation absorbed dose to each organ. Initial analyses of estimated radiation absorbed dose were completed at the clinical site. An additional, centralized dosimetry analysis was performed subsequently to provide a consistent analysis of data collected from the seven clinical sites. In all patients with dosimetry data (n =56), normal organ and red marrow radiation absorbed doses were estimated to be well under the protocol-defined upper limit of 20 Gy and 3 Gy, respectively. Median estimated radiation absorbed dose was 3.4 Gy to liver (range 1.2–7.8 Gy), 2.6 Gy to lungs (range 0.72–4.4 Gy), and 0.38 Gy to kidneys (range 0.07–0.61 Gy). Median estimated tumor radiation absorbed dose was 17 Gy (range 5.8–67 Gy). No correlation was noted between hematologic toxicity and the following variables: red marrow radiation absorbed dose, blood T _1/2, blood AUC, plasma T _1/2, and plasma AUC. It is concluded that ⁹⁰Y-Zevalin administered at nonmyeloablative maximum tolerated doses results in acceptable radiation absorbed doses to normal organs. The only toxicity of note is hematologic and is not correlated to red marrow radiation absorbed dose estimates or T _1/2, reflecting that hematologic toxicity is dependent on bone marrow reserve in this heavily pretreated population. Received 24 January and in revised form 20 March 2000     

Murine Haemopoietic Stem Cells with Long-term Engraftment and Marrow Repopulating Ability are More Resistant to Gamma-radiation than are Spleen Colony Forming Cells

The radiation sensitivity of various subsets in the haemopoietic stem cell hierarchy was defined using a limiting dilution type long-term bone marrow culture technique that was previously shown to allow quantification of cells with spleen colony-forming potential (day-12 CFU-S) and in vivo marrow repopulating ability (MRA). Primitive stem cells that generate new in vitro clonable colony-forming cells (CFU-C) in the irradiated marrow (MRA) and have long-term repopulation ability (LTRA) in vitro (cobblestone area forming cell, CAFC day-28) had D₀ values of 1·25 and 1·38 Gy, respectively. A lower D₀ was found for the less primitive CFU-S day-12, CAFC day-12 and cells with erythroid repopulating ability (0·91, 1·08 and 0·97 Gy, respectively). CFU-S day-7 were the most radiosensitive (D₀ equalling 0·79 Gy), while CFU-C and CAFC day-5 were relatively resistant to irradiation (D₀ 1·33 and 1·77 Gy). Split-dose irradiation with a 6 h interval gave dose sparing for stem cells with MRA and even more with in vitro LTRA, less for CFU-S day-12 and CAFC day-10 and none for CFU-S day-7. The cell survival data of the specified stem cell populations were compared with the ability of a fixed number of B6-Gpi-1^a donor bone marrow cells to provide for short- and long-term engraftment in single- and split-dose irradiated cognenic B6-Gpi-1^b mice. Serial blood glucose phosphate isomerase (Gpi) phenotyping showed less chimerism in the split as compared to the single radiation dose groups beyond 4 weeks after transplant. Radiation dose-response curves corresponding to stable chimerism at 12 weeks for single and fractionated doses revealed appreciable split-dose recovery (D₂–D₁) in the order of 2 Gy. This was comparable to D₂–D₁ estimates for MRA and late-developing CAFC (1·27 and 1·43 Gy, respectively), but differed from the poor dose recovery in cells corresponding to the committed CFU-S day-7/12 and CAFC day-10 population (0·14–0·33 Gy). These data are together consistent with differential radiosensitivity and repair in the haemopoietic stem cell hierarchy, and provide a cellular basis for explaining the dose-sparing effect of fractionated total-body irradiation conditioning on long-term host marrow repopulation.     

Biological dose estimation for two severely exposed patients in a radiation accident in Shandong Jining,China, in 2004

Purpose:?To estimate the biological doses for two severely exposed subjects (A and B) in a radiation accident in Shandong Jining, China in 2004.

Materials and methods:?Conventional chromosome aberration analysis and cytokinesis-block micronuclei (CBMN) assay were performed in peripheral blood and bone marrow samples on two subjects after the accident. A new dose-effect curve and the nuclear division index (NDI) obtained from in vitro irradiation experiments using high dose of ⁶⁰Co γ-rays were used to estimate the exposed doses.

Results:?No metaphases or binucleated cells were observed in the peripheral blood cultures from either of the subjects. However, metaphases and binucleated cells were obtained from both subjects after bone marrow cultures. Both dicentric/ring and micronuclei yields were very high. The dose estimated for A and B were 20.0 Gy and 8.8 Gy, respectively, by dicentric/ring scoring, similar to the data by combination of the CBMN and NDI (CBMN?+?NDI) assay. The estimated doses by the two methods were in accordance with the clinical symptoms.

Conclusion:?The new curve, together with the CBMN?+?NDI assay, are reliable for estimating higher doses of irradiation. In future radiation accidents, the accuracy and significance of these methods can be further tested.     

Multiple blood-proteins approach for early-response exposure assessment using an in vivo murine radiation model

Purpose:?The aim was to evaluate the utility of multiple blood-protein biomarkers for early-response assessment of radiation exposure using a murine radiation model system.

Material and methods:?BALB/c male mice (8–10 weeks old) were exposed to whole-body ⁶⁰Co γ-rays (10 cGy min^?1) over a broad dose range (0–7 Gy). Blood protein biomarkers (i.e., Growth Arrest and DNA Damage Inducible Gene 45 or GADD45α, interleukin 6 or IL-6, and serum amyloid A or SAA) were measured by enzyme linked immunosorbent assay (ELISA) at 4, 24, 48, and 72 h after total-body irradiation (TBI).

Results:?Time- and dose-dependent increases in the protein targets were observed. The use of multiple protein targets was evaluated using multiple linear regression analysis to provide dose-response calibration curves for dose assessment. Multivariate discriminant analysis demonstrated enhanced dose-dependent separation of irradiated animals from control as the number of biomarkers increased.

Conclutions:?Results from this study represent a proof-of-concept for multiple blood-proteins biodosimetry approach. It was demonstrated for the first time that protein expression profile could be developed not only to assess radiation exposure in male BALB/c mice but also to distinguish the level of radiation exposure, ranging from 1–7 Gy.     

Microarray analysis of differentially expressed genes in mouse bone marrow tissues after ionizing radiation

Purpose: To identify differentially expressed genes in mouse bone marrow involved in radiation-induced injury.

Materials and methods: Microarray analysis was used to identify the differentially expressed genes and other techniques, e.g., polymerase chain reaction (PCR), western-blotting and antisense were also used to validate the results.

Results: DNA microarray analysis demonstrated that the mRNA of 34 genes increased and 69 genes decreased in mouse bone marrow cells (BMC) from C57BL mice 6h after a whole body dose of 6.5 Gy. These differentially expressed genes were involved in a number of processes including DNA replication/repair, proliferation/apoptosis, cell cycle control and RNA processing. In these experiments, a decline of the mammalian homolog Sir2a (an acronym for the silent mating type information regulation 2 homolog [SIRT1]) mRNA accompanied by an increase of P53 protein acetylation was observed in irradiated BMC. To determine whether the reduced SIRT1 is related to the higher acetylation status of P53 after irradiation, we designed and synthesized antisense oligonucleotides (AS) targeting human SIRT1 mRNA. Notably, AS transfection increased tumor protein 53 (P53) protein acetylation and bax-luciferase activity in human bone marrow stromal cell line (HS-5) after radiation. Furthermore, the AS transfer stimulated cell apoptosis in post-irradiation HS-5 cells.

Conclusion: Ionizing radiation (IR) affects the expression of a series of genes including genes involved in G1/S transition and the P53 pathway. Among those, reduction of SIRT1 was seen to be involved in transactivation of P53.     

Parallel comparison of pre-conditioning and post-conditioning effects in human cancers and keratinocytes upon acute gamma irradiation

Abstract

Purpose: To determine and compare the effects of pre-conditioning and post-conditioning towards gamma radiation responses in human cancer cells and keratinocytes.

Material and methods: The clonogenic survival of glioblastoma cells (T98G), keratinocytes (HaCaT), and colorectal carcinoma cells (HCT116 p53^+/+ and p53^?/?) was assessed following gamma ray exposure from a Cs-137 source. The priming dose preceded the challenge dose in pre-conditioning whereas the priming dose followed the challenge dose in post-conditioning. The priming dose was either 5 mGy or 0.1?Gy. The challenge dose was 0.5–5?Gy.

Results: In both pre- and post-conditioning where the priming dose was 0.1?Gy and the challenge dose was 4?Gy, RAR developed in T98G but not in HaCaT cells. In HCT116 p53^+/+, pre-conditioning had either no effect or a radiosensitizing effect and whereas post-conditioning induced either radiosensitizing or radioadaptive effect. The different observed outcomes were dependent on dose, the time interval between the priming and challenge dose, and the time before the first irradiation. Post-conditioning effects could occur with a priming dose as low as 5 mGy in HCT116 p53^+/+ cells. When HCT116 cells had no p53 protein expression, the radiosensitizing or radioadaptive response by the conditioning effect was abolished.

Conclusions: The results suggest that radiation conditioning responses are complex and depend on at least the following factors: the magnitude of priming/challenge dose, the time interval between priming and challenge dose, p53 status, cell seeding time prior to the first radiation treatment. This work is the first parallel comparison demonstrating the potential outcomes of pre- and post-conditioning in different human cell types using environmentally and medically relevant radiation doses.     

Attenuation of radiation-induced gastrointestinal damage by epidermal growth factor and bone marrow transplantation in mice

Purpose: We examined the effect of epidermal growth factor (EGF) and bone marrow transplantation (BMT) on gastrointestinal damage after high-dose irradiation of mice.

Material and methods: C57Black/6 mice were used. Two survival experiments were performed (12 and 13 Gy; ⁶⁰Co, 0.59–0.57 Gy/min). To evaluate BMT and EGF action, five groups were established – 0 Gy, 13 Gy, 13 Gy + EGF (at 2 mg/kg, first dose 24 h after irradiation and then every 48 h), 13 Gy + BMT (5 × 10⁶ cells from green fluorescent protein [GFP] syngenic mice, 4 h after irradiation), and 13 Gy + BMT + EGF. Survival data, blood cell counts, gastrointestine and liver parameters and GFP positive cell migration were measured.

Results: BMT and EGF (three doses, at 2 mg/kg, administered 1, 3 and 5 days after irradiation) significantly increased survival (13 Gy). In blood, progressive cytopenia was observed with BMT, EGF or their combination having no improving effect early after irradiation. In gastrointestinal system, BMT, EGF and their combination attenuated radiation-induced atrophy and increased regeneration during first week after irradiation with the combination being most effective. Signs of systemic inflammatory reaction were observed 30 days after irradiation.

Conclusions: Our data indicate that BMT together with EGF is a promising strategy in the treatment of high-dose whole-body irradiation damage.     

G—CSF和IL—6联合应用协同促进受照小鼠造血功能恢？…

目的 探讨Ｇ－ＣＳＦ和ＩＬ－６联合应用协同促进受辐射小鼠血血功能恢复的作用及机理。方法 采用Ｆ８００血细胞自动计数仪计数红细胞、白细胞、血小板和血红蛋白等指标。常规法进行骨髓集落培养,内生脾结节计数,琼脂糖电泳方法检测骨髓细胞程序性死亡。结果 Ｇ－ＣＳＦ和ＩＬ－６联合应用促进受辐射小鼠外周血细胞的恢复,促进脾脏内源性脾结节的形成,增加骨髓细胞含量和促进骨细胞ＧＭ－ＣＳＦ的形成,提高受辐射小鼠的生存     

Differential response to acute low dose radiation in primary and immortalized endothelial cells

Abstract

Purpose: The low dose radiation response of primary human umbilical vein endothelial cells (HUVEC) and its immortalized derivative, the EA.hy926 cell line, was evaluated and compared.

Material and methods: DNA damage and repair, cell cycle progression, apoptosis and cellular morphology in HUVEC and EA.hy926 were evaluated after exposure to low (0.05–0.5 Gy) and high doses (2 and 5 Gy) of acute X-rays.

Results: Subtle, but significant increases in DNA double-strand breaks (DSB) were observed in HUVEC and EA.hy926 30 min after low dose irradiation (0.05 Gy). Compared to high dose irradiation (2 Gy), relatively more DSB/Gy were formed after low dose irradiation. Also, we observed a dose-dependent increase in apoptotic cells, down to 0.5 Gy in HUVEC and 0.1 Gy in EA.hy926 cells. Furthermore, radiation induced significantly more apoptosis in EA.hy926 compared to HUVEC.

Conclusions: We demonstrated for the first time that acute low doses of X-rays induce DNA damage and apoptosis in endothelial cells. Our results point to a non-linear dose-response relationship for DSB formation in endothelial cells. Furthermore, the observed difference in radiation-induced apoptosis points to a higher radiosensitivity of EA.hy926 compared to HUVEC, which should be taken into account when using these cells as models for studying the endothelium radiation response.     

Biodosimetry using radiation-induced micronuclei in skin fibroblasts

Purpose:?We assessed micronuclei in dermal fibroblasts as a local biodosimeter for estimating accidental in vivo radiation exposure.

Materials and methods:?Male and female C3H/HeJ and C57Bl6 mice of four age groups (～11, 36, 60 and 99 weeks) received a single whole body dose of gamma radiation (0–10 Gy) and radiation-induced micronuclei per 1,000 binucleated cells were assessed in skin fibroblasts in their first division after isolation from biopsies taken on days 1 and 7 post irradiation. The method of generalized estimating equations was used for statistical analyses.

Results:?Total micronuclei were increased on day 1 in a dose-dependent manner in the range of 1–10 Gy, with no significant attenuation of response between day 1 and day 7 and no significant effect of gender. Between-strain differences were observed with C3H/HeJ mice showing lower background micronuclei and a slightly steeper dose response. Age affected only the background micronuclei (moderate increase with age). The model demonstrated that the assay yields ‘unbiased’ prediction of the dose between 0 and 7 Gy. Within this dose range, the predicted dose was found to be accurate within ±1.5–2 Gy. When the specificity is set to 95%, the assay can distinguish between unexposed and 2 Gy exposed mice with a sensitivity of around 60%. The sensitivity approached 100% when discriminating between unexposed mice and mice receiving doses equal to or greater than 4 Gy. The percentage of binucleated cells with micronuclei was shown to be useful as a simpler and slightly faster substitute for the total micronuclei count.

Conclusion:?Micronuclei in dermal fibroblasts isolated up to 1 week after irradiation can be a useful biodosimeter for local dose after accidental radiation exposure.