Thrombopoietin mimetic stimulates bone marrow vascular and stromal niches to mitigate acute radiation syndrome

BACKGROUND

Acute radiation syndrome (ARS) manifests after exposure to high doses of radiation in the instances of radiologic accidents or incidents. Facilitating regeneration of the bone marrow (BM), namely the hematopoietic stem and progenitor cells (HSPCs), is key in mitigating ARS and multi-organ failure. JNJ-26366821, a PEGylated thrombopoietin mimetic (TPOm) peptide, has been shown as an effective medical countermeasure (MCM) to treat hematopoietic-ARS (H-ARS) in mice. However, the activity of TPOm on regulating BM vascular and stromal niches to support HSPC regeneration has yet to be elucidated.

METHODS

C57BL/6J mice (9-14 weeks old) received sublethal or lethal total body irradiation (TBI), a model for H-ARS, by 137Cs or X-rays. At 24 h post-irradiation, mice were subcutaneously injected with a single dose of TPOm (0.3 mg/kg or 1.0 mg/kg) or PBS (vehicle). At homeostasis and on days 4, 7, 10, 14, 18, and 21 post-TBI with and without TPOm treatment, BM was harvested for histology, BM flow cytometry of HSPCs, endothelial (EC) and mesenchymal stromal cells (MSC), and whole-mount confocal microscopy. For survival, irradiated mice were monitored and weighed for 30 days. Lastly, BM triple negative cells (TNC; CD45-, TER-119-, CD31-) were sorted for single-cell RNA-sequencing to examine transcriptomics after TBI with or without TPOm treatment.

RESULTS

At homeostasis, TPOm expanded the number of circulating platelets and HSPCs, ECs, and MSCs in the BM. Following sublethal TBI, TPOm improved BM architecture and promoted recovery of HSPCs, ECs, and MSCs. Furthermore, TPOm elevated VEGF-C levels in normal and irradiated mice. Following lethal irradiation, mice improved body weight recovery and 30-day survival when treated with TPOm after 137Cs and X-ray exposure. Additionally, TPOm reduced vascular dilation and permeability. Finally, single-cell RNA-seq analysis indicated that TPOm increased the expression of collagens in MSCs to enhance their interaction with other progenitors in BM and upregulated the regeneration pathway in MSCs.

CONCLUSIONS

TPOm interacts with BM vascular and stromal niches to locally support hematopoietic reconstitution and systemically improve survival in mice after TBI. Therefore, this work warrants the development of TPOm as a potent radiation MCM for the treatment of ARS.

Histopathological studies of nonhuman primates exposed to supralethal doses of total- or partial-body radiation: influence of a medical countermeasure, gamma-tocotrienol

Despite remarkable scientific progress over the past six decades within the medical arts and in radiobiology in general, limited radiation medical countermeasures (MCMs) have been approved by the United States Food and Drug Administration for the acute radiation syndrome (ARS). Additional effort is needed to develop large animal models for improving the prediction of clinical safety and effectiveness of MCMs for acute and delayed effects of radiation in humans. Nonhuman primates (NHPs) are considered the animal models that reproduce the most appropriate representation of human disease and are considered the gold standard for drug development and regulatory approval. The clinical and histopathological effects of supralethal, total- or partial-body irradiations (12 Gy) of NHPs were assessed, along with possible protective actions of a promising radiation MCM, gamma-tocotrienol (GT3). Results show that these supralethal radiation exposures induce severe injuries that manifest both clinically as well as pathologically, as evidenced by the noted functionally crippling lesions within various major organ systems of experimental NHPs. The MCM, GT3, has limited radioprotective efficacy against such supralethal radiation doses.

Iron Deposition in the Bone Marrow and Spleen of Nonhuman Primates with Acute Radiation Syndrome

The risk of exposure to high levels of ionizing radiation from nuclear weapons or radiological accidents is an increasing world concern. Partial- or total-body exposure to high doses of radiation is potentially lethal through the induction of acute radiation syndrome (ARS). Hematopoietic cells are sensitive to radiation exposure; white blood cells primarily undergo apoptosis while red blood cells (RBCs) undergo hemolysis. Several laboratories demonstrated that the rapid hemolysis of RBCs results in the release of acellular iron into the blood. We recently demonstrated using a murine model of ARS after total-body irradiation (TBI) and the loss of RBCs, iron accumulated in the bone marrow and spleen, notably between 4-21 days postirradiation. Here, we investigated iron accumulation in the bone marrow and spleens from TBI nonhuman primates (NHPs) using histological stains. We observed trends in increased intracellular and extracellular brown pigmentation in the bone marrow after various doses of radiation, especially after 4-15 days postirradiation, but these differences did not reach significance. We observed a significant increase in Prussian blue-staining intracellular iron deposition in the spleen 13-15 days after 5.8-8.5 Gy of TBI. We observed trends of increased iron in the spleen after 30-60 days postirradiation, with varying doses of radiation, but these differences did not reach significance. The NHP model of ARS confirms our earlier findings in the murine model, showing iron deposition in the bone marrow and spleen after TBI.

Multi-omic Analysis of Non-human Primate Heart after Partial-body Radiation with Minimal Bone Marrow Sparing

ABSTRACT

High-dose radiation exposure results in hematopoietic and gastrointestinal acute radiation syndromes followed by delayed effects of acute radiation exposure, which encompasses multiple organs, including heart, kidney, and lung. Here we sought to further characterize the natural history of radiation-induced heart injury via determination of differential protein and metabolite expression in the heart. We quantitatively profiled the proteome and metabolome of left and right ventricle from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Global proteome profiling identified more than 2,200 unique proteins, with 220 and 286 in the left and right ventricles, respectively, showing significant responses across at least three time points compared to baseline levels. High-throughput targeted metabolomics analyzed a total of 229 metabolites and metabolite combinations, with 18 and 22 in the left and right ventricles, respectively, showing significant responses compared to baseline levels. Bioinformatic analysis performed on metabolomic and proteomic data revealed pathways related to inflammation, energy metabolism, and myocardial remodeling were dysregulated. Additionally, we observed dysregulation of the retinoid homeostasis pathway, including significant post-radiation decreases in retinoic acid, an active metabolite of vitamin A. Significant differences between left and right ventricles in the pathology of radiation-induced injury were identified. This multi-omic study characterizes the natural history and molecular mechanisms of radiation-induced heart injury in NHP exposed to PBI with minimal bone marrow sparing.

Development of a Model of the Acute and Delayed Effects of High Dose Radiation Exposure in Jackson Diversity Outbred Mice; Comparison to Inbred C57BL/6 Mice

Development of medical countermeasures against radiation relies on robust animal models for efficacy testing. Mouse models have advantages over larger species due to economics, ease of conducting aging studies, existence of historical databases, and research tools allowing for sophisticated mechanistic studies. However, the radiation dose-response relationship of inbred strains is inherently steep and sensitive to experimental variables, and inbred models have been criticized for lacking genetic diversity. Jackson Diversity Outbred (JDO) mice are the most genetically diverse strain available, developed by the Collaborative Cross Consortium using eight founder strains, and may represent a more accurate model of humans than inbred strains. Herein, models of the Hematopoietic-Acute Radiation Syndrome and the Delayed Effects of Acute Radiation Exposure were developed in JDO mice and compared to inbred C57BL/6. The dose response relationship curve in JDO mice mirrored the more shallow curves of primates and humans, characteristic of genetic diversity. JDO mice were more radioresistant than C57BL/6 and differed in sensitivity to antibiotic countermeasures. The model was validated with pegylated-G-CSF, which provided significantly enhanced 30-d survival and accelerated blood recovery. Long-term JDO survivors exhibited increased recovery of blood cells and functional bone marrow hematopoietic progenitors compared to C57BL/6. While JDO hematopoietic stem cells declined more in number, they maintained a greater degree of quiescence compared to C57BL/6, which is essential for maintaining function. These JDO radiation models offer many of the advantages of small animals with the genetic diversity of large animals, providing an attractive alternative to currently available radiation animal models.

Lack of Cellular Inflammation in a Non-human Primate Model of Radiation Nephropathy

Inflammation is commonly cited as a mechanism of delayed effects of acute radiation exposure (DEARE). Confirmation of its presence could provide significant insight to targeted use of treatments or mitigators of DEARE. We sought to quantify the presence of cellular inflammation in kidneys of non-human primates that developed acute and chronic kidney injury after a partial body irradiation exposure. We show herein that cellular inflammation is not found as a component of either acute or chronic kidney injury. Other mechanistic pathways of injury must be sought.

Immune Reconstitution and Thymic Involution in the Acute and Delayed Hematopoietic Radiation Syndromes

Lymphoid lineage recovery and involution after exposure to potentially lethal doses of ionizing radiation have not been well defined, especially the long-term effects in aged survivors and with regard to male/female differences. To examine these questions, male and female C57BL/6 mice were exposed to lethal radiation at 12 wk of age in a model of the Hematopoietic-Acute Radiation Syndrome, and bone marrow, thymus, spleen, and peripheral blood examined up to 24 mo of age for the lymphopoietic delayed effects of acute radiation exposure. Aged mice showed myeloid skewing and incomplete lymphocyte recovery in all lymphoid tissues. Spleen and peripheral blood both exhibited a monophasic recovery pattern, while thymus demonstrated a biphasic pattern. Naïve T cells in blood and spleen and all subsets of thymocytes were decreased in aged irradiated mice compared to age-matched non-irradiated controls. Of interest, irradiated males experienced significantly improved reconstitution of thymocyte subsets and peripheral blood elements compared to females. Bone marrow from aged irradiated survivors was significantly deficient in the primitive lymphoid-primed multipotent progenitors and common lymphoid progenitors, which were only 8-10% of levels in aged-matched non-irradiated controls. Taken together, these analyses define significant age- and sex-related deficiencies at all levels of lymphopoiesis throughout the lifespan of survivors of the Hematopoietic-Acute Radiation Syndrome and may provide a murine model suitable for assessing the efficacy of potential medical countermeasures and therapeutic strategies to alleviate the severe immune suppression that occurs after radiation exposure.

A Systematic Review of the Hematopoietic Acute Radiation Syndrome (H-ARS) in Canines and Non-human Primates: Acute Mixed Neutron/Gamma vs. Reference Quality Radiations

A systematic review of relevant studies that determined the dose response relationship (DRR) for the hematopoietic (H) acute radiation syndrome (ARS) in the canine relative to radiation quality of mixed neutron:gamma radiations, dose rate, and exposure uniformity relative to selected reference radiation exposure has not been performed. The datasets for rhesus macaques exposure to mixed neutron:gamma radiation are used herein as a species comparative reference to the canine database. The selection of data cohorts was made from the following sources: Ovid Medline (1957-present), PubMed (1954-present), AGRICOLA (1976-present), Web of Science (1954-present), and US HHS RePORT (2002-present). The total number of hits across all search sites was 3,077. Several referenced, unpublished, non-peer reviewed government reports were unavailable for review. Primary published studies using canines, beagles, and mongrels were evaluated to provide an informative and consistent review of mixed neutron:gamma radiation effects to establish the DRRs for the H-ARS. Secondary and tertiary studies provided additional information on the hematologic response or the effects on hematopoietic progenitor cells, radiation dosimetry, absorbed dose, and organ dose. The LD50/30 values varied with neutron quality, exposure aspect, and mixed neutron:gamma ratio. The reference radiation quality varied from 250 kVp or 1-2 MeV x radiation and Co gamma radiation. A summary of a published review of a data set describing the DRR in rhesus macaques for mixed neutron:gamma radiation exposure in the H-ARS is included for a comparative reference to the canine dataset. The available evidence provided a reliable and extensive database that characterized the DRR for the H-ARS in canines and young rhesus macaques exposed to mixed neutron:gamma radiations of variable energy relative to 250 kVp, 1-2 MeV x radiation and Co gamma, and uniform and non-uniform total-body irradiation without the benefit of medical management. The mixed neutron:gamma radiation showed an energy-dependent RBE of ~ 1.0 to 2.0 relative to reference radiation exposure within both species. A marginal database described the DRR for the gastrointestinal (GI)-ARS. Medical management showed benefit in both species relative to the mixed neutron:gamma as well as exposure to reference radiation. The DRR for the H-ARS was characterized by steep slopes and relative LD50/30 values that reflected the radiation quality, exposure aspect, and dose rate over a range in time from 1956-2012.

Radiation-induced tissue damage and response

Normal tissue responses to ionizing radiation have been a major subject for study since the discovery of X-rays at the end of the 19th century. Shortly thereafter, time-dose relationships were established for some normal tissue endpoints that led to investigations into how the size of dose per fraction and the quality of radiation affected outcome. The assessment of the radiosensitivity of bone marrow stem cells using colony-forming assays by Till and McCulloch prompted the establishment of in situ clonogenic assays for other tissues that added to the radiobiology toolbox. These clonogenic and functional endpoints enabled mathematical modeling to be performed that elucidated how tissue structure, and in particular turnover time, impacted clinically relevant fractionated radiation schedules. More recently, lineage tracing technology, advanced imaging and single cell sequencing have shed further light on the behavior of cells within stem, and other, cellular compartments, both in homeostasis and after radiation damage. The discovery of heterogeneity within the stem cell compartment and plasticity in response to injury have added new dimensions to the consideration of radiation-induced tissue damage. Clinically, radiobiology of the 20th century garnered wisdom relevant to photon treatments delivered to a fairly wide field at around 2 Gy per fraction, 5 days per week, for 5-7 weeks. Recently, the scope of radiobiology has been extended by advances in technology, imaging and computing, as well as by the use of charged particles. These allow radiation to be delivered more precisely to tumors while minimizing the amount of normal tissue receiving high doses. One result has been an increase in the use of schedules with higher doses per fraction given in a shorter time frame (hypofractionation). We are unable to cover these new technologies in detail in this review, just as we must omit low-dose stochastic effects, and many aspects of dose, dose rate and radiation quality. We argue that structural diversity and plasticity within tissue compartments provides a general context for discussion of most radiation responses, while acknowledging many omissions. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Deposition of Iron in the Bone Marrow of a Murine Model of Hematopoietic Acute Radiation Syndrome

Exposure to high-dose total body irradiation (TBI) can result in hematopoietic acute radiation syndrome (H-ARS), characterized by leukopenia, anemia, and coagulopathy. Death from H-ARS occurs from hematopoietic insufficiency and opportunistic infections. Following radiation exposure, red blood cells (RBCs) undergo hemolysis from radiation-induced hemoglobin denaturation, causing the release of iron. Free iron can have multiple detrimental biological effects, including suppression of hematopoiesis. We investigated the impact of radiation-induced iron release on the bone marrow following TBI and the potential impact of the ACE inhibitor captopril, which improves survival from H-ARS. C57BL/6J mice were exposed to 7.9 Gy, ⁶⁰Co irradiation, 0.6 Gy/min (LD_70-90/30). RBCs and reticulocytes were significantly reduced within 7 days of TBI, with the RBC nadir at 14-21 days. Iron accumulation in the bone marrow correlated with the time course of RBC hemolysis, with an ∼10-fold increase in bone marrow iron at 14-21 days post-irradiation, primarily within the cytoplasm of macrophages. Iron accumulation in the bone marrow was associated with increased expression of genes for iron binding and transport proteins, including transferrin, transferrin receptor 1, ferroportin, and integrin αMβ2. Expression of the gene encoding Nrf2, a transcription factor activated by oxidative stress, also increased at 21 days post-irradiation. Captopril did not alter iron accumulation in the bone marrow or expression of iron storage genes, but did suppress Nrf2 expression. Our study suggests that following TBI, iron is deposited in tissues not normally associated with iron storage, which may be a secondary mechanism of radiation-induced tissue injury.

Characterizing the Natural History of Acute Radiation Syndrome of the Gastrointestinal Tract: Combining High Mass and Spatial Resolution Using MALDI-FTICR-MSI

The acute radiation syndrome of the gastrointestinal tract has been histologically characterized, but the molecular and functional mechanisms that lead to these cellular alterations remain enigmatic. Mass spectrometry imaging is the only technique that enables the simultaneous detection and cellular or regional localization of hundreds of biomolecules in a single experiment. This current study utilized matrix-assisted laser desorption/ionization mass spectrometry imaging for the molecular characterization of the first natural history study of gastrointestinal acute radiation syndrome in the nonhuman primate. Jejunum samples were collected at days 4, 8, 11, 15, and 21 following 12-Gy partial-body irradiation with 2.5% bone marrow sparing. Mass spectrometry imaging investigations identified alterations in lipid species that further understanding of the functional alterations that occur over time in the different cellular regions of the jejunum following exposure to high doses of irradiation. Alterations in phosphatidylinositol species informed on dysfunctional epithelial cell differentiation and maturation. Differences in glycosphingolipids of the villi epithelium that would influence the absorptive capacity and functional structure of the brush border membrane were detected. Dichotomous alterations in cardiolipins indicated altered structural and functional integrity of mitochondria. Phosphatidylglycerol species, known regulators of toll-like receptors, were detected and localized to regions in the lamina propria that contained distinct immune cell populations. These results provide molecular insight that can inform on injury mechanism in a nonhuman primate model of the acute radiation syndrome of the gastrointestinal tract. Findings may contribute to the identification of therapeutic targets and the development of new medical countermeasures.

Delayed Effects of Acute Radiation Exposure (Deare) in Juvenile and Old Rats: Mitigation by Lisinopril

Our goal is to develop lisinopril as a mitigator of delayed effects of acute radiation exposure in the National Institute of Allergy and Infectious Diseases program for radiation countermeasures. Published studies demonstrated mitigation of delayed effects of acute radiation exposure by lisinopril in adult rats. However, juvenile or old rats beyond their reproductive lifespans have never been tested. Since no preclinical models of delayed effects of acute radiation exposure were available in these special populations, appropriate rat models were developed to test lisinopril after irradiation. Juvenile (42-d-old, prepubertal) female and male WAG/RijCmcr (Wistar) rats were given 13-Gy partial-body irradiation with only part of one hind limb shielded. Lethality from lung injury between 39-58 d and radiation nephropathy between 106-114 d were recorded. All irradiated-only juvenile rats were morbid from delayed effects of acute radiation exposure by 114 d, while lisinopril (24 mg m d) started 7 d after irradiation and continued improved survival to 88% (p = 0.0015, n ≥ 8/group). Old rats (>483-d-old, reproductively senescent) were irradiated with 13-Gy partial-body irradiation keeping part of one leg shielded and additionally shielding the head in some animals. Irradiated old females developed lethal nephropathy, and all became morbid by 170 d after irradiation, though no rats displayed lethal radiation pneumonitis. Similar results were observed for irradiated geriatric males, though 33% of rats remained alive at 180 d after irradiation. Lisinopril mitigated radiation nephropathy in old rats of both sexes. Finally, comparison of delayed effects of acute radiation exposure between irradiated juvenile, adult, and old rats showed younger rats were more sensitive to delayed effects of acute radiation exposure with earlier manifestation of injuries to some organs.

Lifelong Residual bone Marrow Damage in Murine Survivors of the Hematopoietic Acute Radiation Syndrome (H-ARS): A Compilation of Studies Comprising the Indiana University Experience

Accurate analyses of the delayed effects of acute radiation exposure in survivors of the hematopoietic acute radiation syndrome are hampered by low numbers of mice for examination due to high lethality from the acute syndrome, increased morbidity and mortality in survivors, high cost of husbandry for long-term studies, biological variability, and inconsistencies of models from different laboratories complicating meta-analyses. To address this, a compilation of 38 similar hematopoietic acute radiation syndrome studies conducted over a 7-y period in the authors' laboratory, comprising more than 1,500 irradiated young adult C57BL/6 mice and almost 600 day-30 survivors, was assessed for hematopoietic delayed effects of acute radiation exposure at various times up to 30 mo of age. Significant loss of long-term repopulating potential of phenotypically defined primitive hematopoietic stem cells was documented in hematopoietic acute radiation syndrome survivors, as well as significant decreases in all hematopoietic lineages in peripheral blood, prominent myeloid skew, significantly decreased bone marrow cellularity, and numbers of lineage-negative Sca-1+ cKit+ CD150+ cells (KSL CD150+; the phenotype known to be enriched for hematopoietic stem cells), and increased cycling of KSL CD150+ cells. Studies interrogating the phenotype of bone marrow cells capable of initiation of suspension cultures and engraftment in competitive transplantation assays documented the phenotype of hematopoietic stem cells in hematopoietic acute radiation syndrome survivors to be the same as that in nonirradiated age-matched controls. This compilation study adds rigor and validity to our initial findings of persistent hematopoietic dysfunction in hematopoietic acute radiation syndrome survivors that arises at the level of the hematopoietic stem cell and which affects all classes of hematopoietic cells for the life of the survivor.

The Gastrointestinal Subsyndrome of the Acute Radiation Syndrome in Rhesus Macaques: A Systematic Review of the Lethal Dose-response Relationship With and Without Medical Management

Well-characterized animal models that mimic the human response to potentially lethal doses of radiation are required to assess the efficacy of medical countermeasures under the criteria of the US Food and Drug Administration's Animal Rule. Development of a model for the gastrointestinal acute radiation syndrome requires knowledge of the radiation dose-response relationship and time course of mortality and morbidity across the acute and prolonged gastrointestinal radiation syndrome. The nonhuman primate, rhesus macaque, is a relevant animal model that has been used to determine the efficacy of medical countermeasures to mitigate major signs of morbidity and mortality relative to the hematopoietic acute radiation syndrome, gastrointestinal acute radiation syndrome, and lung injury. It can be used to assess the natural history of gastrointestinal damage, concurrent multiple organ injury, and aspects of the mechanism of action for acute radiation exposure and treatment. A systematic review of relevant studies that determined the dose-response relationship for the gastrointestinal acute and prolonged radiation syndrome in the rhesus macaque relative to radiation dose, quality, dose rate, exposure uniformity, and use of medical management has never been performed.

CLINICAL TRIAGE OF RADIATION CASUALTIES-THE HEMATOLOGICAL MODULE OF THE BUNDESWEHR INSTITUTE OF RADIOBIOLOGY

Novel treatment regimens for therapy of the acute radiation syndrome (ARS) were developed over the last years. Their application relies on an early and high-throughput diagnosis. Based on the database SEARCH a new scientific triage tool (called H-module) was developed for early prediction of the later developing ARS. Based on peripheral blood cell counts measured within the first three days after a radiation exposure a prediction of the H-ARS severity (as well as therapeutic recommendations) can be performed with this tool. The H-module was tested within two table top exercises. Contributors were either radiation experts or radiobiology students and the required patient data were generated from real case histories. The H-module proved to be an easy to train and easy to use precise and promising new tool to assist and guide the treating physician in a large-scale radiation scenario. An introduction into this new tool and other diagnostic tools will be provided in the context of a NATO-teaching class in October/November 2019 in Paris.

System for Scoring Severity of Acute Radiation Syndrome Response in Rhesus Macaques (Macaca mulatta)

We developed a clinical assessment tool for use in an NHP radiation model to 1) quantify severity responses for subsyndromes of the acute radiation syndrome (ARS; that is, hematopoietic and others) and 2) identify animals that required enhanced monitoring. Our assessment tool was based primarily on the MEdical TREatment ProtocOLs for Radiation Accident Victims (METREPOL) scoring system but was adapted for NHP to include additional indices (for example, behaviors) for use in NHP studies involving limited medical intervention. Male (n = 16) and female (n = 12) rhesus macaques (Macaca mulatta; 5 groups: sham and 1.0, 3.5, 6.5, and 8.5 Gy; n = 6 per group) received sham- or bilateral 60Co γ-irradiation at approximately 0.6 Gy/mn. Clinical signs of ARS and blood analysis were obtained before and serially for clinical assessment during the period of 6 h to 60 d after sham or 60Co irradiation. Minimal supportive care (that is, supplemental nutrition, subcutaneous fluid, loperamide, acetaminophen, and topical antibiotic ointment) was prescribed based on clinical observations. Results from clinical signs and assays for assessment of relevant organ systems in individual animals were stratified into ARS severity scores of normal (0), mild (1), moderate (2), and severe (3 or 4). Individual NHP were scored for maximal subsyndrome ARS severity in multiple organ systems by using the proposed ARS scoring system to obtain an overall ARS response category. One NHP died unexpectedly. The multiple-parameter ARS severity scoring tool aided in the identification of animals in the high-dose (6.5 and 8.5 Gy) groups that required enhanced monitoring.

ACUTE MYELOID LEUKEMIA, PROSTATE AND SKIN CANCER IN ACUTE RADIATION SYNDROME SURVIVOR AFTER THE 1986 CHERNOBYL NUCLEAR ACCIDENT: CASE REPORT

The development of hemoblastosis is often associated with the influence of various genotoxic unfavorable factors, in particular, with the effect of ionizing radiation. This article presents a case report of acute myeloid leukemia (AML) in a patient who was involved in the 1986 accident at the Chernobyl Nuclear Power Plant and suffered an acute radiation syndrome of degree II severity. Based on clinical and cytogenetic dosimetry, the average absorbed radiation dose to the whole body was estimated to be 4.3 Gy. During long-term clinical follow-up (27 years), moderate transient instability of hematological parameters was observed: lymphocytosis, leukopenia and thrombocytopenia, which was associated with chronic viral hepatitis C. Further cytogenetic investigations demonstrated a very high frequency of translocations, up to 50 times background values, that persisted over 3 decades. In 2014, the patient was diagnosed and operated on for prostate cancer and received a course of radiotherapy (total fractionated local dose of 35 Gy) in May 2015. From December 2015 through April 2016, the patient experienced general weakness and developed progressive cytopenia. A diagnosis of AML, resulting from a myelodysplastic syndrome, was confirmed by abnormal complex clones detected in 38% of metaphases by the mFISH-method, along with other chromosomal rearrangements. The patient underwent several chemotherapy treatments for AML but eventually died of bilateral pneumonia in March 2017.

Selective Insulin-like Growth Factor Resistance Associated with Heart Hemorrhages and Poor Prognosis in a Novel Preclinical Model of the Hematopoietic Acute Radiation Syndrome

Although bone marrow aplasia has been considered for the past decades as the major contributor of radiation-induced blood disorders, cytopenias alone are insufficient to explain differences in the prevalence of bleeding. In this study, the minipig was used as a novel preclinical model of hematopoietic acute radiation syndrome to assess if factors other than platelet counts correlated with bleeding and survival. We sought to determine whether radiation affected the insulin-like growth factor-1 (IGF-1) pathway, a growth hormone with cardiovascular and radioprotective features. Gottingen and Sinclair minipigs were exposed to ionizing radiation at hematopoietic doses. The smaller Gottingen minipig strain was more sensitive to radiation; differences in IGF-1 levels were minimal, suggesting that increased sensitivity could depend on weak response to the hormone. Radiation caused IGF-1 selective resistance by inhibiting the anti-inflammatory anti-oxidative stress IRS/PI3K/Akt but not the pro-inflammatory MAPK kinase pathway, shifting IGF-1 signaling towards a pro-oxidant, pro-inflammatory environment. Selective IGF-1 resistance associated with hemorrhages in the heart, poor prognosis, increase in C-reactive protein and NADPH oxidase 2, uncoupling of endothelial nitric oxide synthase, inhibition of nitric oxide (NO) synthesis and imbalance between the vasodilator NO and the vasoconstrictor endothelin-1 molecules. Selective IGF-1 resistance is a novel mechanism of radiation injury, associated with a vicious cycle amplifying reactive oxygen species-induced damage, inflammation and endothelial dysfunction. In the presence of thrombocytopenia, selective inhibition of IGF-1 cardioprotective function may contribute to the development of hemostatic disorders. This finding may be particularly relevant for individuals with low IGF-1 activity, such as the elderly or those with cardiometabolic dysfunctions.

Successful Teaching of Radiobiology Students in the Medical Management of Acute Radiation Effects From Real Case Histories Using Clinical Signs and Symptoms and Taking Advantage of Recently Developed Software Tools

In 2015, the Bundeswehr Institute of Radiobiology organized a North Atlantic Treaty Organization exercise to examine the significance of clinical signs and symptoms for the prediction of late-occurring acute radiation syndrome. Cases were generated using either the Medical Treatment Protocols for Radiation Accident Victims (METREPOL, n = 167) system or using real-case descriptions extracted from a database system for evaluation and archiving of radiation accidents based on case histories (SEARCH, n = 24). The cases ranged from unexposed [response category 0 (RC 0, n = 89)] to mild (RC 1, n = 45), moderate (RC 2, n = 19), severe (RC 3, n = 20), and lethal (RC 4, n = 18) acute radiation syndrome. During the previous exercise, expert teams successfully predicted hematological acute radiation syndrome severity, determined whether hospitalization was required, and gave treatment recommendations, taking advantage of different software tools developed by the North Atlantic Treaty Organization teams. The authors provided the same data set to radiobiology students who were introduced to the medical management of acute effects after radiation exposure and the software tools during a class lasting 15 h. Corresponding to the previous results, difficulties in the discrimination between RC 0/RC 1 and RC 3/RC 4, as well as a systematic underestimation of RC 1 and RC 2, were observed. Nevertheless, after merging reported response categories into clinically relevant groups (RC 0-1, RC 2-3, and RC 3-4), it was found that the majority of cases (95.2% ± 2.2 standard deviations) were correctly identified and that 94.7% (±2.6 standard deviations) developing acute radiation syndrome and z96.4% (±1.6 standard deviations) requiring hospitalization were identified correctly. Two out of three student teams also provided a dose estimate. These results are comparable to the best-performing team of the 2015 North Atlantic Treaty Organization exercise (response category: 92.5%; acute radiation syndrome: 95.8%; hospitalization: 96.3%).

Combined Therapy of Pegylated G-CSF and Alxn4100TPO Improves Survival and Mitigates Acute Radiation Syndrome after Whole-Body Ionizing Irradiation Alone and Followed by Wound Trauma

Exposure to ionizing radiation alone or combined with traumatic tissue injury is a crucial life-threatening factor in nuclear and radiological incidents. Radiation injuries occur at the molecular, cellular, tissue and systemic levels; their mechanisms, however, remain largely unclear. Exposure to radiation combined with skin wounding, bacterial infection or burns results in greater mortality than radiation exposure alone in dogs, pigs, rats, guinea pigs and mice. In the current study we observed that B6D2F1/J female mice exposed to 60Co gamma-photon radiation followed by 15% total-body-surface-area skin wounds experienced an increment of 25% higher mortality over a 30-day observation period compared to those subjected to radiation alone. Radiation exposure delayed wound healing by approximately 14 days. On day 30 post-injury, bone marrow and ileum in animals from both groups (radiation alone or combined injury) still displayed low cellularity and structural damage. White blood cell counts, e.g., neutrophils, lymphocytes, monocytes, eosinophils, basophils and platelets, still remained very low in surviving irradiated alone animals, whereas only the lymphocyte count was low in surviving combined injury animals. Likewise, in surviving animals from radiation alone and combined injury groups, the RBCs, hemoglobin, hematocrit and platelets remained low. We observed, that animals treated with both pegylated G-CSF (a cytokine for neutrophil maturation and mobilization) and Alxn4100TPO (a thrombopoietin receptor agonist) at 4 h postirradiation, a 95% survival (vehicle: 60%) over the 30-day period, along with mitigated body-weight loss and significantly reduced acute radiation syndrome. In animals that received combined treatment of radiation and injury that received pegylated G-CSF and Alxn4100TPO, survival was increased from 35% to 55%, but did not accelerate wound healing. Hematopoiesis and ileum showed significant improvement in animals from both groups (irradiation alone and combined injury) when treated with pegylated G-CSF and Alxn4100TPO. Treatment with pegylated G-CSF alone increased survival after irradiation alone and combined injury by 33% and 15%, respectively, and further delayed wound healing, but increased WBC, RBC and platelet counts after irradiation alone, and only RBCs and platelets after combined injury. Treatment with Alxn4100TPO alone increased survival after both irradiation alone and combined injury by 4 and 23%, respectively, and delayed wound healing after combined injury, but increased RBCs, hemoglobin concentrations, hematocrit values and platelets after irradiation alone and only platelets after combined injury. Taken together, the results suggest that combined treatment with pegylated G-CSF and Alxn4100TPO is effective for mitigating effects of both radiation alone and in combination with injury.

Linking Doses with Clinical Scores of Hematopoietic Acute Radiation Syndrome

In radiation accidents, determining the radiation dose the victim received is a key step for medical decision making and patient prognosis. To reconstruct and evaluate the absorbed dose, researchers have developed many physical devices and biological techniques during the last decades. However, using the physical parameter "absorbed dose" alone is not sufficient to predict the clinical development of the various organs injured in an individual patient. In operational situations for radiation accidents, medical responders need more urgently to classify the severity of the radiation injury based on the signs and symptoms of the patient. In this work, the author uses a unified hematopoietic model to describe dose-dependent dynamics of granulocytes, lymphocytes, and platelets, and the corresponding clinical grading of hematopoietic acute radiation syndrome. This approach not only visualizes the time course of the patient's probable outcome in the form of graphs but also indirectly gives information of the remaining stem and progenitor cells, which are responsible for the autologous recovery of the hematopoietic system. Because critical information on the patient's clinical evolution can be provided within a short time after exposure and only peripheral cell counts are required for the simulation, these modeling tools will be useful to assess radiation exposure and injury in human-involved radiation accident/incident scenarios.

Establishment of Early Endpoints in Mouse Total-Body Irradiation Model

Acute radiation sickness (ARS) following exposure to ionizing irradiation is characterized by radiation-induced multiorgan dysfunction/failure that refers to progressive dysfunction of two or more organ systems, the etiological agent being radiation damage to cells and tissues over time. Radiation sensitivity data on humans and animals has made it possible to describe the signs associated with ARS. A mouse model of total-body irradiation (TBI) has previously been developed that represents the likely scenario of exposure in the human population. Herein, we present the Mouse Intervention Scoring System (MISS) developed at the Veterinary Sciences Department (VSD) of the Armed Forces Radiobiology Research Institute (AFRRI) to identify moribund mice and decrease the numbers of mice found dead, which is therefore a more humane refinement to death as the endpoint. Survival rates were compared to changes in body weights and temperatures in the mouse (CD2F1 male) TBI model (6–14 Gy, ⁶⁰Co γ-rays at 0.6 Gy min^-1), which informed improvements to the Scoring System. Individual tracking of animals via implanted microchips allowed for assessment of criteria based on individuals rather than by group averages. From a total of 132 mice (92 irradiated), 51 mice were euthanized versus only four mice that were found dead (7% of non-survivors). In this case, all four mice were found dead after overnight periods between observations. Weight loss alone was indicative of imminent succumbing to radiation injury, however mice did not always become moribund within 24 hours while having weight loss >30%. Only one survivor had a weight loss of greater than 30%. Temperature significantly dropped only 2–4 days before death/euthanasia in 10 and 14 Gy animals. The score system demonstrates a significant refinement as compared to using subjective assessment of morbidity or death as the endpoint for these survival studies.

Progenitor Cell Mobilization by Gamma-tocotrienol: A Promising Radiation Countermeasure

This article reviews studies of progenitor mobilization with gamma-tocotrienol (GT3), a tocol under advanced development as a radiation countermeasure for acute radiation syndrome (ARS). GT3 protects mice against high doses of ionizing radiation and induces high levels of granulocyte colony-stimulating factor (G-CSF). GT3-induced G-CSF in conjunction with AMD3100 (a chemokine receptor antagonist clinically used to improve the yield of mobilized progenitors) mobilizes progenitors; these mobilized progenitors mitigate injury when infused to mice exposed to acute, high-dose ionizing radiation. The administration of a G-CSF antibody to GT3-injected donor mice abrogated the radiomitigative efficacy of blood or peripheral blood mononuclear cells (PBMC) in irradiated recipient mice. The efficacy of GT3-injected donor mice blood or PBMC was comparable to a recently published article involving blood or mononuclear cells obtained from mice injected with G-CSF. The injected progenitors were found to localize in various tissues of irradiated hosts. The authors demonstrate the efficacy of a bridging therapy in a preclinical animal model that allows the lymphohematopoietic system of severely immunocompromised mice to recover. This suggests that GT3 is a highly effective agent for radioprotection and mobilizing progenitors with significant therapeutic potential. Therefore, GT3 may be considered for further translational development and ultimately for use in humans.

Contribution of INTRAMUSCULAR Autologous Adipose Tissue-Derived Stem Cell Injections to Treat Cutaneous Radiation Syndrome: Preliminary Results

Cutaneous radiation syndrome caused by high dose located irradiation is characterized by delayed symptoms, incomplete wound healing, and poor revascularization. Subcutaneous adipose tissue derived stromal/stem cells have been shown to improve skin repair in a minipig model of cutaneous radiation syndrome despite a subcutaneous defect being a consequence of radio-induced muscular fibrosis. Based on the pro-myogenic potential of stromal/stem cells, a new protocol combining subcutaneous and intramuscular injections was evaluated in a preliminary study. Six female minipigs were locally irradiated at the dose of 50 Gy using a Co source (0.6 Gy min) and randomly divided into two groups. Three animals received the vehicle (phosphate-buffer-saline solution) and three animals received three injections of 75 × 10 adipose tissue derived stromal/stem cells each time (day 25, 46, and 66 post-irradiation). Pigs were euthanized on day 76 post-irradiation before development of clinical skin symptoms. All minipigs exhibited a homogeneous skin evolution. Macroscopic observation of irradiated muscles showed prominent fibrosis and necrosis areas in controls as opposed to adipose tissue-derived stromal/stem cells injected animals. Moreover, muscle biopsy analysis highlighted a recruitment of myofibroblasts (Immune Reactive Score: p < 0.01), an interleukin 10 secretion and a muscle regeneration pathway activation after intramuscular injections of adipose tissue-derived stromal/stem cells (western-blot: respectively, 200-fold change difference and twofold higher in treated animals). Globally, these preliminary data suggest that intramuscular injections of adipose tissue-derived stromal/stem cells improve muscle regeneration in the cutaneous-radiation syndrome. Further work is ongoing to evaluate this therapeutic strategy on a larger animal number with a longer clinical follow-up.

In Vivo Nanodetoxication for Acute Uranium Exposure

Accidental exposure to uranium is a matter of concern, as U(VI) is nephrotoxic in both human and animal models, and its toxicity is associated to chemical toxicity instead of radioactivity. We synthesized different PAMAM G4 and G5 derivatives in order to prove their interaction with uranium and their effect on the viability of red blood cells in vitro. Furthermore, we prove the effectiveness of the selected dendrimers in an animal model of acute uranium intoxication. The dendrimer PAMAM G4-Lys-Fmoc-Cbz demonstrated the ability to chelate the uranyl ion in vivo, improving the biochemical and histopathologic features caused by acute intoxication with uranium.

Gastrointestinal acute radiation syndrome in Göttingen minipigs (Sus scrofa domestica)

In the absence of supportive care, exposing Göttingen minipigs to γ-radiation doses of less than 2 Gy achieves lethality due to hematopoietic acute radiation syndrome. Doses of 2 to 5 Gy are associated with an accelerated hematopoietic syndrome, characterized by villus blunting and fusion, the beginning of sepsis, and a mild transient reduction in plasma citrulline concentration. We exposed male Göttingen minipigs (age, 5 mo; weight, 9 to 11 kg) to γ-radiation doses of 5 to 12 Gy (total body; (60)Co, 0.6 Gy/min) to test whether these animals exhibit classic gastrointestinal acute radiation syndrome (GI-ARS). After exposure, the minipigs were monitored for 10 d by using clinical signs, CBC counts, and parameters associated with the development of the gastrointestinal syndrome. Göttingen minipigs exposed to γ radiation of 5 to 12 Gy demonstrate a dose-dependent occurrence of all parameters classically associated with acute GI-ARS. These results suggest that Göttingen minipigs may be a suitable model for studying GI-ARS after total body irradiation, but the use of supportive care to extend survival beyond 10 d is recommended. This study is the first step toward determining the feasibility of using Göttingen minipigs in testing the efficacy of candidate drugs for the treatment of GI-ARS after total body irradiation.

Protective effect and the therapeutic index of indralin in juvenile rhesus monkeys

The radioprotective effect of indralin in rhesus monkeys was examined over 60 d following gamma irradiation. Male and female rhesus macaques (Macaca mulatta) 2-3-years-old and weighing 2.1-3.5 kg were used. Animals were exposed to total-body gamma irradiation from (60)Co at a dose of 6.8 Gy (lethal dose, 100% lethality over 30 days). Indralin (40-120 mg kg(-1)) was administered intramuscularly 5 min prior to radiation exposure. Indralin taken at a dose of 120 mg kg(-1) protected five out of six monkeys (compared with the radiation control group, in which all 10 animals died). The average effective dose of indralin in the monkeys exposed to gamma irradiation for 30 min was equal to 77.3 (63.3-94.3) mg kg(-1), and the maximum tolerated dose of indralin administered to monkeys was 800 mg kg(-1). Indralin reduced radiation-induced injuries in macaques, thus resulting in a less severe course of acute radiation syndrome. Delayed and less pronounced manifestation of the haemorrhagic syndrome of the disease, and milder forms of both leukopenia and anaemia were also noted. The therapeutic index for indralin, expressed as the ratio of the maximum tolerated dose to the average effective dose, was equal to 10. Therefore, indralin has a significant radioprotective effect against radiation and has a high therapeutic index in rhesus monkeys.

Granulocyte colony-stimulating factor in the treatment of acute radiation syndrome: a concise review

This article concisely summarizes data on the action of one of the principal and best known growth factors, the granulocyte colony-stimulating factor (G-CSF), in a mammalian organism exposed to radiation doses inducing acute radiation syndrome. Highlighted are the topics of its real or anticipated use in radiation accident victims, the timing of its administration, the possibilities of combining G-CSF with other drugs, the ability of other agents to stimulate endogenous G-CSF production, as well as of the capability of this growth factor to ameliorate not only the bone marrow radiation syndrome but also the gastrointestinal radiation syndrome. G-CSF is one of the pivotal drugs in the treatment of radiation accident victims and its employment in this indication can be expected to remain or even grow in the future.

Simvastatin attenuates radiation-induced tissue damage in mice

The aim of this study was to investigate the protective effect of simvastatin against radiation-induced tissue injury in mice. Mice were radiated with 4 Gy or 8 Gy after 20 mg/kg/d simvastatin treatment over 2 weeks. Morphological changes were observed in the jejunum and bone marrow, and apoptotic cells were determined in both tissues. Peripheral blood cells were counted, and the superoxide dismutase (SOD) activity and the malondialdehyde (MDA) level in tissues of both thymus and spleen were measured. Compared with the radiation-only group, 20 mg/kg/d simvastatin administration significantly increased the mean villi height and decreased apoptotic cells in jejunum tissue, and stimulated regeneration and reduced apoptotic cells in bone marrow. Peripheral blood cell analysis revealed that simvastatin treatment induced a larger number of red blood cells and increased the hemoglobin level present after 4 Gy of radiation. Interestingly, it was also found that the number of peripheral endothelial progenitor cells was markedly increased following simvastatin administration. Antioxidant determination for tissues displayed that simvastatin therapy increased the SOD activity after both 4 and 8 Gy of radiation, but only decreased the MDA level after 4 Gy. Simvastatin ameliorated radiation-induced tissue damage in mice. The radioprotective effect of simvastatin was possibly related to inhibition of apoptosis and improvement of oxygen-carrying and antioxidant activities.

[Recombinant thrombopoietin antiradiation therapeutic effectiveness evaluation on dogs according to hemopoiesis and survival criteria]

Recombinant human thrombopoietin (rh TPO) has been investigated as a means of acute radiation disease urgent treatment in the experiments on 24 mongrel dogs. The animals were exposed to total acute gamma-irradiation at the doses of 3.5 Gy (exceeding LD50/45 under our conditions) and 3 Gy. All the dogs including control ones received antibiotics Ampicillin and Gentamicin twice a day during the acute period from the 7th to the 21st day. TPO was injected one time s/c or i/v at the doses of5 or 10 mkg/kg 1.5-2 h after exposure. TPO at a dose of 5 mkg/kg was ineffective. TPO at a dose of 10 mkg/kg had a positive effect on the kinetics of blood forming units, especially platelets (nadir, restoration rate) in terms of the 45-day survival. As a result, in TPO groups, nadir averaged at both exposure doses on leucocytes (1.3-1.4) x 10(9)/l vs (0.70-0.75) x 10(9)/l in control groups and on thrombocytes (102-112) x 10(9)/l vs (44-33) x 10(9)/l in control ones. Despite the low number of animals in experimental groups, the results permit to regard rhTPO as a worth-while urgent therapeutic means for the acute radiation damage treatment and preventing thrombopenia.

Survival efficacy of the PEGylated G-CSFs Maxy-G34 and neulasta in a mouse model of lethal H-ARS, and residual bone marrow damage in treated survivors

In an effort to expand the worldwide pool of available medical countermeasures (MCM) against radiation, the PEGylated G-CSF (PEG-G-CSF) molecules Neulasta and Maxy-G34, a novel PEG-G-CSF designed for increased half-life and enhanced activity compared to Neulasta, were examined in a murine model of the Hematopoietic Syndrome of the Acute Radiation Syndrome (H-ARS), along with the lead MCM for licensure and stockpiling, G-CSF. Both PEG-G-CSFs were shown to retain significant survival efficacy when administered as a single dose 24 h post-exposure, compared to the 16 daily doses of G-CSF required for survival efficacy. Furthermore, 0.1 mg kg of either PEG-G-CSF affected survival of lethally-irradiated mice that was similar to a 10-fold higher dose. The one dose/low dose administration schedules are attractive attributes of radiation MCM given the logistical challenges of medical care in a mass casualty event. Maxy-G34-treated mice that survived H-ARS were examined for residual bone marrow damage (RBMD) up to 9 mo post-exposure. Despite differences in Sca-1 expression and cell cycle position in some hematopoietic progenitor phenotypes, Maxy-G34-treated mice exhibited the same degree of hematopoietic stem cell (HSC) insufficiency as vehicle-treated H-ARS survivors in competitive transplantation assays of 150 purified Sca-1+cKit+lin-CD150+cells. These data suggest that Maxy-G34, at the dose, schedule, and time frame examined, did not mitigate RBMD but significantly increased survival from H-ARS at one-tenth the dose previously tested, providing strong support for advanced development of Maxy-G34, as well as Neulasta, as MCM against radiation.

Infusion of Trx-1-overexpressing hucMSC prolongs the survival of acutely irradiated NOD/SCID mice by decreasing excessive inflammatory injury

A protective reagent for ARI should have the ability to repair injured tissue caused by radiation and prevent continuous damage from secondary risk factors. Trx-1 was explored as a candidate therapy for ARI, as it scavenges reactive oxygen species, regulates cell growth and differentiation, participates in immune reactions, and inhibits apoptosis by acting inside and/or outside cells. Trx-1 can also decrease excessive inflammation in ARI by regulating the creation of inflamed media, by inhibiting the activation of complement, and by reducing the chemotaxis, adhesion, and migration of inflammatory cells. As effectively and stably expressing exogenous genes in the long term and regulating immune inflammation and tissue repair, MSC are a good choice for Trx-1 gene therapy. In this study, Trx-1-overexpressing hucMSC-Trx-1 were obtained by adenoviral vector-mediated infection. We first measured the redox capacity of hucMSC-Trx-1 with an antioxidant capacity (T-AOC) assay, a hydrogen peroxide (H2O2) content determination assay in vivo, a H2O2-induced oxidation hemolysis assay, and a lipid peroxidation assay in vitro. Then, we measured survival time, the protection of the hematopoietic system, and the regulation of inflammation in important organs in three treatment groups of NOD/SCID mice (treated with hucMSC-Trx-1, with hucMSC, and with saline) that were exposed to 4.5 Gy (60)Co-γ-ray radiation. The hucMSC-Trx-1 group achieved superior antioxidation results, protecting bone marrow hematopoietic stem cells (Lin(-)CD117(+): hucMSC-Trx-1 vs. hucMSC, P<0.05; hucMSC-Trx-1 vs. NS, P<0.01), promoting the formation of red blood cells and hemoglobin (hucMSC-Trx-1 vs. hucMSC or NS, P<0.05), reducing inflammation and damage in important organs (Bone marrow and lung: hucMSC-Trx-1 vs. NS, P<0.01; hucMSC-Trx-1 vs. hucMSC, P<0.05. Liver and intestine: hucMSC-Trx-1 vs. NS, P<0.05; hucMSC-Trx-1 vs. hucMSC, P<0.05), and prolonging survival (hucMSC-Trx-1 vs. hucMSC or NS, P<0.01). Therefore, hucMSC-Trx-1 combines the merits of gene and cell therapy as a multifunctional radioprotector for ARI.

Radioprotective properties of tocopherol succinate against ionizing radiation in mice

Threats of nuclear and other radiologic exposures have been increasing but no countermeasure for acute radiation syndrome has been approved by regulatory authorities. In prior publications we have demonstrated the efficacy of tocopherol succinate (TS) as a promising radiation countermeasure with the potential to protect against lethal doses of ionizing radiation exposure. The aim of this study was to gain further insight regarding how TS protects mice against a lethal dose of radiation. CD2F1 mice were injected subcutaneously with 400 mg/kg of TS, and 24 h later exposed to (60)Co γ-radiation. Intestinal tissues or spleen/thymus were harvested after irradiation and analyzed for CD68-positive inflammatory cells and apoptotic cells by immunostaining of jejunal cross-sections. Comet assay was used to analyze DNA damage in various tissues. Phospho-histone H3(pH3) and the proliferating cell nuclear antigen (PCNA) were used as mitotic markers for immunostaining jejunal cross-sections. We observed that injecting TS significantly decreased the number of CD68-positive cells, DNA damage and apoptotic cells (BAX, caspase 3 and cleaved poly(ADP-ribose) polymerase-positive cells) as judged by various apoptotic pathway markers. TS treatment also increased proliferating cells in irradiated mice. Results of this study further support our contention that TS protects mice against lethal doses of ionizing radiation by inhibiting radiation-induced apoptosis and DNA damage while enhancing cell proliferation.

5-AED enhances survival of irradiated mice in a G-CSF-dependent manner, stimulates innate immune cell function, reduces radiation-induced DNA damage and induces genes that modulate cell cycle progression and apoptosis

The steroid androst-5-ene-3ß,17ß-diol (5-androstenediol, 5-AED) elevates circulating granulocytes and platelets in animals and humans, and enhances survival during the acute radiation syndrome (ARS) in mice and non-human primates. 5-AED promotes survival of irradiated human hematopoietic progenitors in vitro through induction of Nuclear Factor-κB (NFκB)-dependent Granulocyte Colony-Stimulating Factor (G-CSF) expression, and causes elevations of circulating G-CSF and interleukin-6 (IL-6). However, the in vivo cellular and molecular effects of 5-AED are not well understood. The aim of this study was to investigate the mechanisms of action of 5-AED administered subcutaneously (s.c.) to mice 24 h before total body γ- or X-irradiation (TBI). We used neutralizing antibodies, flow cytometric functional assays of circulating innate immune cells, analysis of expression of genes related to cell cycle progression, DNA repair and apoptosis, and assessment of DNA strand breaks with halo-comet assays. Neutralization experiments indicated endogenous G-CSF but not IL-6 was involved in survival enhancement by 5-AED. In keeping with known effects of G-CSF on the innate immune system, s.c. 5-AED stimulated phagocytosis in circulating granulocytes and oxidative burst in monocytes. 5-AED induced expression of both bax and bcl-2 in irradiated animals. Cdkn1a and ddb1, but not gadd45a expression, were upregulated by 5-AED in irradiated mice. S.c. 5-AED administration caused decreased DNA strand breaks in splenocytes from irradiated mice. Our results suggest 5-AED survival enhancement is G-CSF-dependent, and that it stimulates innate immune cell function and reduces radiation-induced DNA damage via induction of genes that modulate cell cycle progression and apoptosis.

Evidence of delayed gastrointestinal syndrome in high-dose irradiated mice

The acute effects of irradiation on the gastrointestinal (GI) system are well documented, but the longer-term effects are less well known. Increased incidence of adenocarcinoma has been noted, but apart from descriptions of fibrosis, the development of other pathologies specific to survivors of acute radiation is poorly understood. Samples were taken from C57BL/6 mice irradiated with partial-body irradiation where the thorax, head, and forelimbs were shielded (i.e., sparing 40% of the bone marrow). Tissue from age-matched controls was also collected. There were clear pathological changes in the intestine associated with DEARE (Delayed Effects of Acute Radiation Exposure) at doses greater than 12 Gy, with a dose-related increase in observed pathologies. Mice maintained on the synthetic antibiotic ciprofloxacin during the acute phase (days 4 to 20), however, had a lower or delayed incidence of symptoms. After 20 d, mice developed structures similar to early adenomas. Abnormally high levels of apoptotic and mitotic cells were present in some crypts, along with the early adenomas, suggesting tissue regeneration and areas of deregulated cell turnover. Over time, there was inhibited crypt cell proliferation in animals with advanced symptoms, a blunting of the crypts and villi, and an enlargement of villus girth, with an increasingly acellular and fibrotic extracellular matrix (a characteristic that has been demonstrated previously in aging mice). Together these changes may lead to a reduced functional surface area and less motile intestine. These observations are similar to those seen in geriatric animals, suggesting a premature aging of the GI tract.

[The current potential of forensic medical expertise of a local radiation injury]

The present review concerns radiation injury, a most challenging problem facing modern forensic medical expertise. It is shown that its successful solution requires the combined application of all currently available relevant methods including radio- and biodosimetry, forensic histological examination, etc.

[Peculiarities of organization and performance of forensic medical expertise of the corpses of persons died of acute radiation injury]

This paper is concerned with the topical problems of forensic medical diagnostics of acute radiation injury. The general and specific problems pertaining to the organization and performance of forensic medical expertise of the corpses of persons deceased by reason of acute radiation sickness are considered. The special emphasis is laid on the selection of autopsy materials and their referring to specialized laboratories for the additional investigation. The methods of anti-radiation protection of the medical personnel are considered.

Assessment of risks and dose thresholds for some effects of acute exposure

Findings from the analyses of the dose-response relationship are reviewed with regard to different effects of acute radiation exposure. The analyses have been performed based on the dosimetry and clinical data for the nuclear workers acutely exposed to gamma rays or gamma rays and neutrons as a result of radiation accidents at the Mayak Production Association (Russia). The statistically significant risk curves for morbidity and mortality from acute radiation syndrome (ARS), as well as risks of the onset of vomiting at the prodromal phase and agranulocytosis, have been obtained. The Weibull model appropriately describes the corresponding risk curves. Estimates of the dose thresholds have been obtained for ARS morbidity (∼0.7 Gy) and mortality (∼6-7 Gy), vomiting at the prodromal phase (∼1.5 Gy), and agranulocytosis (∼3.5 Gy). The statistically significant power dependence between the onset of vomiting at the prodromal phase and the onset of agranulocytosis, as well as the dose dependence for the onset of agranulocytosis, has been revealed.

Radiation rescue: mesenchymal stromal cells protect from lethal irradiation

BACKGROUND

Successful treatment of acute radiation syndromes relies on immediate supportive care. In patients with limited hematopoietic recovery potential, hematopoietic stem cell (HSC) transplantation is the only curative treatment option. Because of time consuming donor search and uncertain outcome we propose MSC treatment as an alternative treatment for severely radiation-affected individuals.

METHODS AND FINDINGS

Mouse mesenchymal stromal cells (mMSCs) were expanded from bone marrow, retrovirally labeled with eGFP (bulk cultures) and cloned. Bulk and five selected clonal mMSCs populations were characterized in vitro for their multilineage differentiation potential and phenotype showing no contamination with hematopoietic cells. Lethally irradiated recipients were i.v. transplanted with bulk or clonal mMSCs. We found a long-term survival of recipients with fast hematopoietic recovery after the transplantation of MSCs exclusively without support by HSCs. Quantitative PCR based chimerism analysis detected eGFP-positive donor cells in peripheral blood immediately after injection and in lungs within 24 hours. However, no donor cells in any investigated tissue remained long-term. Despite the rapidly disappearing donor cells, microarray and quantitative RT-PCR gene expression analysis in the bone marrow of MSC-transplanted animals displayed enhanced regenerative features characterized by (i) decreased proinflammatory, ECM formation and adhesion properties and (ii) boosted anti-inflammation, detoxification, cell cycle and anti-oxidative stress control as compared to HSC-transplanted animals.

CONCLUSIONS

Our data revealed that systemically administered MSCs provoke a protective mechanism counteracting the inflammatory events and also supporting detoxification and stress management after radiation exposure. Further our results suggest that MSCs, their release of trophic factors and their HSC-niche modulating activity rescue endogenous hematopoiesis thereby serving as fast and effective first-line treatment to combat radiation-induced hematopoietic failure.

[Study of frequency of TCR-mutant T-helper lymphocytes and level of immunocompetent cells with mFasL apoptosis marker under conditions of ionizing radiation]

Were investigated the parameters of apoptosis of immune cells, the cell subpopulation composition and frequency of TCR-mutant lymphocytes in the peripheral blood of persons exposed to radiation. Increased number of peripheral mFasL-positive mononuclear cells and the accumulation of TCR-mutant T lymphocytes in a wide range of doses were found in the patients. It is doubtless that the effect of ionizing radiation is accompanied by a simulation of Fas-ligand expression on the surface of peripheral mononuclear cells and modification of the activating signal to apoptosis through the molecule CD4, CD8, CD3. The results can be caused by proapoptotic effect of radiation.

[A pathologist's radiological culture]

The authors analyze 8 papers on human radiation pathology, published in the journal "Arkhiv Patologii", which assess the quality of radiological information given in them. It turns out that pathologists have accumulated important facts on some types of pathology (thyroid cancer, diseases of different organs), but their dependence on the action of radiation requires more valid evidence. The absence of radiation doses in most papers reduces the validity of the conclusions of the articles. All possible internal and external causes of the found changes, and not just ionizing radiations should be considered while interpreting results.