Inflammatory cells dynamics control neovascularization and tissue healing after localized radiation induced injury in mice

Local overexposure to ionizing radiation leads to chronic inflammation, vascular damage and cachexia. Here we investigate the kinetics of inflammatory cells from day (D)1 to D180 after mouse hindlimb irradiation and analyze the role of monocyte (Mo) subsets in tissue revascularization. At D1, we find that Mo and T cells are mobilized from spleen and bone marrow to the blood. New vessel formation during early phase, as demonstrated by ~1.4- and 2-fold increased angiographic score and capillary density, respectively, correlates with an increase of circulating T cells, and Mo^hi and type 1-like macrophages in irradiated muscle. At D90 vascular rarefaction and cachexia are observed, associated with decreased numbers of circulating Mo^lo and Type 2-like macrophages in irradiated tissue. Moreover, CCR2- and CX3CR1-deficency negatively influences neovascularization. However adoptive transfer of Mo^hi enhances vessel growth. Our data demonstrate the radiation-induced dynamic inflammatory waves and the major role of inflammatory cells in neovascularization.

Urinary Metabolomics for the Prediction of Radiation-Induced Cardiac Dysfunction

Survivors of acute radiation exposures are likely to experience delayed effects that manifest as injury in late-responding organs such as the heart. Noninvasive indicators of radiation-induced cardiac dysfunction are important in the prediction and diagnosis of this disease. In this study, we aimed to identify urinary metabolites indicative of radiation-induced cardiac damage by analyzing previously collected urine samples from a published study. The samples were collected from male and female wild-type (C57BL/6N) and transgenic mice constitutively expressing Activated Protein C (APCHi), a circulating protein with potential cardiac protective properties, that were exposed to 9.5 Gy of γ-rays. We utilized LC-MS-based metabolomics and lipidomics for the analysis of urine samples collected at 24 h, 1 week, 1 month, 3 months, and 6 months post-irradiation. Radiation caused perturbations in the TCA cycle, glycosphingolipid metabolism, fatty acid oxidation, purine catabolism, and amino acid metabolites, which were more prominent in wild-type (WT) mice compared to APCHi mice, suggesting a differential response between the two genotypes. After combining genotypes and sexes, we identified a multi-analyte urinary panel at early post-irradiation time points that predicted heart dysfunction using a logistic regression model with a discovery validation study design. These studies demonstrate the utility of a molecular phenotyping approach to develop a urinary biomarker panel predictive of delayed effects of ionizing radiation. It is important to note that no live mice were used or assessed in this study; instead, we focused solely on analyzing previously collected urine samples.

Mesenchymal stromal cells in the regeneration of radiation-induced organ sequelae: will they make the difference?

Mesenchymal stromal cells (MSCs) are a stem cell product with good safety that demonstrate significant clinical efficacy in the treatment of different pathologies, including radiation diseases (e.g. radiological burns, pelvic radiation disease). While the first results for some first human applications for the treatment of radiation disease suggest benefit, larger trials with clinically important endpoints are needed before definitive conclusions can be drawn. However, the supply and cost of MSCs remain the two main limitations for this innovative therapeutic product. Exosomes (EXOs), a stem cell product associated with MSC therapy, have shown promising efficacy and safety in humans. MSC-EXO therapeutics represent a promising next-generation approach for treating radiation diseases involving a primary (major) inflammatory component. Provided that conditions for MSC-EXO production and bio-banking are agreed in the near future, the transition to industrial production of MSC-EXOs will be possible, and this is required to initiate well-controlled clinical trials for approval by the European Medicines Agency (EMA) and US Food and Drug Administration (FDA).

The METREPOL criteria-are they still relevant?

The medical management of radiation accidents manual on the acute radiation syndrome proposed a successful strategic approach to diagnosing and treating acute radiation syndrome: the response category concept. Based on clinical and laboratory parameters, this approach aimed to assess damage to critical organ systems as a function of time, categorising different therapeutical approaches. After 20 years of its publication, the following paper attempts to provide a broad overview of this important document and tries to respond if proposed criteria are still relevant for the medical management of radiation-induced injuries. In addition, a critical analysis of its limitations and perspectives is proposed.

Cutaneous and local radiation injuries

The threat of a large-scale radiological or nuclear (R/N) incident looms in the present-day climate, as noted most recently in an editorial in Scientific American (March 2021). These large-scale incidents are infrequent but affect large numbers of people. Smaller-scale R/N incidents occur more often, affecting smaller numbers of people. There is more awareness of acute radiation syndrome (ARS) in the medical community; however, ionising radiation-induced injuries to the skin are much less understood. This article will provide an overview of radiation-induced injuries to the skin, deeper tissues, and organs. The history and nomenclature; types and causes of injuries; pathophysiology; evaluation and diagnosis; current medical management; and current research of the evaluation and management are presented. Cutaneous radiation injuries (CRI) or local radiation injuries (LRI) may lead to cutaneous radiation syndrome, a sub-syndrome of ARS. These injuries may occur from exposure to radioactive particles suspended in the environment (air, soil, water) after a nuclear detonation or an improvised nuclear detonation (IND), a nuclear power plant incident, or an encounter with a radioactive dispersal or exposure device. These incidents may also result in a radiation-combined injury; a chemical, thermal, or traumatic injury, with radiation exposure. Skin injuries from medical diagnostic and therapeutic imaging, medical misadministration of nuclear medicine or radiotherapy, occupational exposures (including research) to radioactive sources are more common but are not the focus of this manuscript. Diagnosis and evaluation of injuries are based on the scenario, clinical picture, and dosimetry, and may be assisted through advanced imaging techniques. Research-based multidisciplinary therapies, both in the laboratory and clinical trial environments, hold promise for future medical management. Great progress is being made in recognising the extent of injuries, understanding their pathophysiology, as well as diagnosis and management; however, research gaps still exist.

Muscle regeneration after high-dose radiation exposure: therapeutic potential of Hedgehog pathway modulation?

Purpose: Intentional or accidental exposure of relatively large as well as localized areas of the skin to ionizing radiation can lead to severe damage of many of its cellular components and cutaneous radiation syndrome. Patients can be treated with an invasive surgical procedure coupled with autologous cell therapy. However, this approach remains perfectible, especially for muscle repair. Indeed, a severe underlying muscle defect persists, in particular because of the damage to the satellite cells which ensure muscle regeneration. To overcome these shortcomings, a solution could be to develop new therapeutic strategies based on pharmacological treatments to improve post-irradiation muscle regeneration. In this study, we focus on the Hedgehog signaling pathway as a target, due to its involvement in myogenesis.Materials and methods: To evaluate the benefit of the pro-myogenic Hedgehog signaling pathway modulation, recombinant Sonic Hedgehog (rShh; agonist) or Cyclopamine (antagonist) were used in a stable cell line of mouse C2C12 myoblasts exposed to radiation (X-rays; 5 Gy). Our in vitro studies were carried out under either proliferation or differentiation conditions. Proliferation, migration, survival (apoptosis) and expression of myogenic genes/proteins were evaluated.Results: A high dose of radiation was shown to exert a serious negative impact in our in vitro model of mouse muscle progenitors after irradiation in proliferation or differentiation conditions. Interestingly, Hh pathway stimulation by rShh promotes the proliferation of myoblasts and their survival while its blockade by Cyclopamine significantly increases cell differentiation toward mature myotubes.Conclusion: These data suggest that, after irradiation, the sequence of activation and inhibition of the Hh pathway could allow rescue and proliferation of satellite cells, followed by their differentiation to regenerate new fibers. On the basis of these encouraging in vitro results, the second phase of our study will involve the in vivo validation of this treatment in a new murine model of ultra-localized muscle irradiation.

Basic concepts of radiation emergency medicine

Nuclear and radiological accidents are not frequent but may lead to major consequences in the population. For the health systems, the need to handle a large number of victims will probably remain as an exception. However, a high number of affected victims can be expected in some terrorist scenarios. In addition, medical accidents in radiotherapy, fluoroscopy and diagnostic radiology have increased the number of patients with severe radiation injuries considerably, especially in developed countries. Given the increased use of ionising radiation for industrial and medical purposes and new technological applications emerging, the number of accidents may increase in the future. Consequently, the early identification and adequate management of these emergencies is a priority, as well as the need for medical preparedness, requiring knowledge about various emergency scenarios and planning appropriate responses to them before they occur. Unfortunately, medical professionals have a substantial knowledge gap in identifying and treating injured persons affected by ionising radiation. As managing radiation accidents is a very challenging process, exercises must be carried out to organise a well-trained multidisciplinary group of professionals to manage any radiation accident properly. Efforts on a continuously updated guidance system should be developed. In addition, new approaches to foster sustainable interdisciplinary and international cooperative networks on radiation injuries are necessary. Lessons learned from past nuclear and radiological emergencies have significantly contributed to strengthening scientific knowledge and increasing the available medical information on the effects of ionising radiation in the human body. In this context, radiation emergency medicine has emerged as a discipline that contributes to the diagnosis, treatment, medical follow-up and prognosis of persons affected by radiation injuries in a nuclear or a radiological emergency. In this paper, we review some relevant concepts related to the medical preparedness and multidisciplinary response required to attend to persons affected by these emergencies.

Hematopoietic Recovery using Multi-Cytokine Therapy in 8 Patients Presenting Radiation-Induced Myelosuppression after Radiological Accidents

Treatment of accidental radiation-induced myelosuppression is primarily based on supportive care and requires specific treatment based on hematopoietic growth factors injection or hematopoietic cell transplantation for the most severe cases. The cytokines used consisted of pegylated erythropoietin (darbepoetin alfa) 500 IU once per week, pegylated G-CSF (pegfilgrastim) 6 mg × 2 once, stem cell factor 20 μg.kg-1 for five days, and romiplostim (TPO analog) 10 μg.kg-1 once per week, with different combinations depending on the accidents. As the stem cell factor did not have regulatory approval for clinical use in France, the French regulatory authorities (ANSM, formerly, AFSSAPS) approved their compassionate use as an investigational drug "on a case-by-case basis". According to the evolution and clinical characteristics, each patient's treatment was adopted on an individual basis. Daily blood count allows initiating G-CSF and SCF delivery when granulocyte <1,000/mm3, TPO delivery when platelets <50,000/mm3, and EPO when Hb<80 g/L. The length of each treatment was based on blood cell recovery criteria. The concept of "stimulation strategy" is linked to each patient's residual hematopoiesis, which varies among them, depending on the radiation exposure's characteristics and heterogeneity. This paper reports the medical management of 8 overexposed patients to ionizing radiation. The recovery of bone marrow function after myelosuppression was accelerated using growth factors, optimized by multiple-line combinations. Particularly in the event of prolonged exposure to ionizing radiation in dose ranges inducing severe myelosuppression (in the order of 5 to 8 Gy), with no indication of hematopoietic stem cell transplantation.

Scientific research and product development in the United States to address injuries from a radiation public health emergency

The USA has experienced one large-scale nuclear incident in its history. Lessons learned during the Three-Mile Island nuclear accident provided government planners with insight into property damage resulting from a low-level release of radiation, and an awareness concerning how to prepare for future occurrences. However, if there is an incident resulting from detonation of an improvised nuclear device or state-sponsored device/weapon, resulting casualties and the need for medical treatment could overwhelm the nation's public health system. After the Cold War ended, government investments in radiation preparedness declined; however, the attacks on 9/11 led to re-establishment of research programs to plan for the possibility of a nuclear incident. Funding began in earnest in 2004, to address unmet research needs for radiation biomarkers, devices and products to triage and treat potentially large numbers of injured civilians. There are many biodosimetry approaches and medical countermeasures (MCMs) under study and in advanced development, including those to address radiation-induced injuries to organ systems including bone marrow, the gastrointestinal (GI) tract, lungs, skin, vasculature and kidneys. Biomarkers of interest in determining level of radiation exposure and susceptibility of injury include cytogenetic changes, 'omics' technologies and other approaches. Four drugs have been approved by the US Food and Drug Administration (FDA) for the treatment of acute radiation syndrome (ARS), with other licensures being sought; however, there are still no cleared devices to identify radiation-exposed individuals in need of treatment. Although many breakthroughs have been made in the efforts to expand availability of medical products, there is still work to be done.

Successful Rescue of the Victim Exposed to a Super High Dose of Iridium-192 during the Nanjing Radiological Accident in 2014

Here we report on the interventions taken to treat a patient exposed to high-dose radiation and provide a protocol for treating such patients in the future. The patient, Mr. Wang, was a 58-year-old male janitor who was accidentally exposed to a ¹⁹²Ir source with an activity of 966.4 GBq or 26.1 Ci. The dose estimated to the lower right limb was 4,100 Gy, whereas the whole-body effective dose was 1.51 Gy. The diagnosis was made according to the results of the patient dose estimation and clinical manifestations. Systemic treatment included stimulating bone marrow hematopoietic cells, enhancing immunity, anti-infection and vitamin supplements. The treatment of radiation-induced skin lesions consisted of several debridements, two skin-flap transplantations and application of mesenchymal stem cells (MSCs). Skin-flap transplantations and MSCs play important roles in the recovery of skin wound. A combination of antibiotics and antimycotic was useful in reducing inflammation. The application of vacuum sealing drainage was effective in removing necrotic tissue and bacteria, ameliorating ischemia and hypoxia of wound tissue, providing a fresh wound bed for wound healing and improving skin or flap graft survival rates. The victim survived the accident without amputation, and function of his highly exposed right leg was partially recovered. These results demonstrate the importance of collaboration among members of a multidisciplinary team in the treatment of this patient.