Stem cell therapy: from bench to bedside.

Several countries have increased efforts to develop medical countermeasures to protect against radiation toxicity due to acts of bioterrorism as well as cancer treatment. Both acute radiation injuries and delayed effects such as cutaneous effects and impaired wound repair depend, to some extent, on angiogenesis deficiency. Vascular damage influences levels of nutrients, oxygen available to skin tissue and epithelial cell viability. Consequently, the evolution of radiation lesions often becomes uncontrolled and surgery is the final option--amputation leading to a disability. Therefore, the development of strategies designed to promote healing of radiation injuries is a major therapeutic challenge. Adult mesenchymal stem cell therapy has been combined with surgery in some cases and not in others and successfully applied in patients with accidental radiation injuries. Although research in the field of radiation skin injury management has made substantial progress in the past 10 y, several strategies are still needed in order to enhance the beneficial effect of stem cell therapy and to counteract the deleterious effect of an irradiated tissue environment. This review summarises the current and evolving advances concerning basic and translational research based on stem cell therapy for the management of radiological burns.

Influence of depleted uranium on hepatic cholesterol metabolism in apolipoprotein E-deficient mice.

Depleted uranium (DU) is uranium with a lower content of the fissile isotope U-235 than natural uranium. It is a radioelement and a waste product from the enrichment process of natural uranium. Because of its very high density, it is used in the civil industry and for military purposes. DU exposure can affect many vital systems in the human body, because in addition to being weakly radioactive, uranium is a toxic metal. It should be emphasized that, to be exposed to radiation from DU, you have to eat, drink, or breathe it, or get it on your skin. This particular study is focusing on the health effects of DU for the cholesterol metabolism. Previous studies on the same issue have shown that the cholesterol metabolism was modulated at molecular level in the liver of laboratory rodents contaminated for nine months with DU. However, this modulation was not correlated with some effects at organs or body levels. It was therefore decided to use a "pathological model" such as hypercholesterolemic apolipoprotein E-deficient laboratory mice in order to try to clarify the situation. The purpose of the present study is to assess the effects of a chronic ingestion (during 3 months) of a low level DU-supplemented water (20 mg L(-1)) on the above mentioned mice in order to determine a possible contamination effect. Afterwards the cholesterol metabolism was studied in the liver especially focused on the gene expressions of cholesterol-catabolising enzymes (CYP7A1, CYP27A1 and CYP7B1), as well as those of associated nuclear receptors (LXRα, FXR, PPARα, and SREBP 2). In addition, mRNA levels of other enzymes of interest were measured (ACAT 2, as well as HMGCoA Reductase and HMGCoA Synthase). The gene expression study was completed with SRB1 and LDLr, apolipoproteins A1 and B and membrane transporters ABC A1, ABC G5. The major effect induced by a low level of DU contamination in apo-E deficient mice was a decrease in hepatic gene expression of the enzyme CYP7B1 (-23%) and nuclear receptors LXRα (-24%), RXR (-32%), HNF4α (-21%) when compared to unexposed ones. These modifications on cholesterol metabolism did not lead to increased disturbances that are specific for apolipoprotein E-deficient mice, suggesting that chronic DU exposure did not worsen the pathology in this experimental model. In conclusion, the results of this study indicate that even for a sensitive pathologic model the exposure to a low dose of DU has no relevant impact. The results confirm the results of our first study carried out on healthy laboratory rodents where a sub-chronic contamination with low dose DU did not affect in vivo the metabolism of cholesterol.

Numerical dosimetric reconstruction of a radiological accident in South America in April 2009.

A severe irradiation accident involving a victim occurred in April 2009 in South America. The victim has found a (192)Ir source fallen from a gammagraphy device and has put it in the left pocket of his pants. Very quickly, an erythema and a blister appeared on the left leg of the victim involving hospitalisation. Following the request of the IAEA assistance, the Ionizing Radiation Dosimetry Laboratory of IRSN was asked to perform a numerical dosimetric reconstruction. A personalised voxel phantom of the victim has been constructed thanks to the Simulation of External Source Accident with Medical images tool developed by the laboratory, and a calculation of the dose with the MCNPX computer code allowed to determine the boundary of the necrotic dose at 25 Gy. On the basis of these calculations, the physicians have performed exeresis of the necrotic region on the left leg on 4 May 2009. Associated with mesenchymal stem cell injection, the leg of the victim was healthy on December 2009.

[Radiation burn "innovating therapeutic approach"]. / Brûlure par irradiation « approche thérapeutique innovante ¼.

Radiation burn is a determinist effect of localized irradiation. The lesion is in good correlation with absorbed dose. Radiation burn is different from thermal burn. The evolution is spatiotemporal unpredictable with successive inflammatory waves and recurrence of necrosis. The conventional surgical treatment is rarely efficient because each surgical operative act seems to stimulate the inflammatory waves and fibro-necrosis process. The lesion can escape to this conventional surgical treatment. The new therapeutic approach combines surgery and cellular therapy with local administration of autologous mesenchymal stem cells. From 5 years, cell therapy have been an adjuvant treatment of surgery. This association is a therapeutic innovation, it's now the recommendation for conservative surgery of this very serious radiation burn.

Cholesterol 7alpha-hydroxylase (CYP7A1) activity is modified after chronic ingestion of depleted uranium in the rat.

Depleted uranium (DU) is a radioactive heavy metal derived from the nuclear energy production. Its wide use in civilian and military items increases the risk of its environmental dissemination, and thus the risk of internal contamination of populations living in such contaminated territories. Previous studies have shown that vitamin D and cerebral cholesterol metabolisms were affected following chronic ingestion of DU. Even more than the brain, the liver is a crucial organ in cholesterol homeostasis since it regulates cholesterol distribution and elimination at body level. The aim of this work was to assess the impact of a low-level chronic ingestion of DU on hepatic cholesterol metabolism. Rats were contaminated with DU in their drinking water at a concentration of 40mg/l for 9 months. The major effect induced by DU was a decrease of CYP7A1 specific activity (-60%) correlated with a matching decrease of its product 7alpha-hydroxycholesterol in the plasma. Hepatic gene expression of transporters ABC A1, ABC G5, ABC G8 and of nuclear receptor RXR was increased, whereas that of catabolism enzyme CYP7B1 was decreased. Thus, after a chronic ingestion of DU, rats experience a modulation of cholesterol catabolism but overcome it, since their cholesterolemia is preserved and no pathology is declared.

Mesenchymal stem cells improve small intestinal integrity through regulation of endogenous epithelial cell homeostasis.

Patients who undergo pelvic or abdominal radiotherapy may develop acute and/or chronic side effects resulting from gastrointestinal tract (GIT) alterations. In this study, we address the question of the regenerative capability of mesenchymal stem cells (MSC) after radiation-induced GIT injury. We also propose cellular targets of MSC therapy. We report that the infusion of human bone marrow-derived MSC (hMSC) provides a therapeutic benefit to NOD/SCID mice undergoing radiation-induced GIT failure. We observed that hMSC treatment brings about fast recovery of the small intestine (structure and function) in mice with reversible alterations and extends the life of mice with irreversible GIT disorders. The effects of hMSC are a consequence of their ability to improve the renewal capability of small intestinal epithelium. hMSC treatment favors the re-establishment of cellular homeostasis by both increasing endogenous proliferation processes (Ki67 immunostaining) and inhibiting apoptosis (TUNEL staining) of radiation-induced small intestinal epithelial cells. Our results suggest that MSC infusion may be used as a therapeutic treatment to limit radiation-induced GIT damage.

Molecular modifications of cholesterol metabolism in the liver and the brain after chronic contamination with cesium 137.

Twenty years after Chernobyl accident, the daily ingestion of foodstuff grown on contaminated grounds remains the main source for internal exposure to ionizing radiations, and primarily to cesium 137 ((137)Cs). Though the effects of a long-term internal contamination with radionuclides are poorly documented, several non-cancerous pathologies have been described in this population. However, lipid metabolism was never investigated after chronic internal contamination although disturbances were observed in externally-exposed people. In this regard, we assessed the effects of a chronic ingestion of (137)Cs on hepatic and cerebral cholesterol metabolism. To mimic a chronically-exposed population, rats were given (137)Cs-supplemented water at a post-accidental dose (150 Bq/rat/day) during 9 months. The plasma profile, and brain and liver cholesterol concentrations were unchanged. A decrease of ACAT 2, Apo E, and LXRmRNA levels was recorded in the liver. In the brain, a decrease of CYP27A1 and ACAT 1 gene expression was observed. These results clearly show that cholesterol metabolism is not disrupted by a chronic ingestion of (137)Cs, although several molecular alterations are observed. This work would be interestingly completed by studying the influence of (137)Cs in models likely more sensitive to contaminants, such as the fetus or individuals susceptible to a lipidic disease.

Cell therapy based on adipose tissue-derived stromal cells promotes physiological and pathological wound healing.

OBJECTIVE: We hypothesized that adipose tissue may contain progenitors cells with cutaneous and angiogenic potential. METHODS AND RESULTS: Adipose tissue-derived stroma cells (ADSCs) were administrated to skin punched wounds of both nonirradiated and irradiated mice (20 Gy, locally). At day 14, ADSCs promoted dermal wound healing and enhanced wound closure, viscolesticity, and collagen tissue secretion in both irradiated and nonirradiated mice. Interestingly, GFP-positive ADSCs incorporated in dermal and epidermal tissue in vivo and expressed epidermal markers K5 and K14. Cultured ADSCs in keratinocyte medium have been shown to differentiate into K5- and K14-positive cells and produced high levels of KGF. At Day 7, ADSCs also improved skin blood perfusion assessed by laser Doppler imaging, capillary density, and VEGF plasma levels in both irradiated and nonirradiated animals. GFP-positive ADSCs incorporated into capillary structures in vivo and expressed the endothelial cell marker CD31. Finally, in situ interphase fluorescence hybridization showed that a small number of ADSCs have the potential to fuse with endogenous keratinocytes. CONCLUSIONS: ADSCs participate in dermal wound healing in physiological and pathological conditions by their ability to promote reepithelialization and angiogenesis. Hence, adipose lineage cells represent a new cell source for therapeutic dermal wound healing.

[Uranium: properties and biological effects after internal contamination]. / Uranium: propriétés et effets biologiques après contamination interne.

Uranium is a radionuclide present in the environment since the origin of the Earth. In addition to natural uranium, recent deposits from industrial or military activities are acknowledged. Uranium's toxicity is due to a combination of its chemical (heavy metal) and radiological properties (emission of ionizing radiations). Acute toxicity induces an important weight loss and signs of renal and cerebral impairment. Alterations of bone growth, modifications of the reproductive system and carcinogenic effects are also often seen. On the contrary, the biological effects of a chronic exposure to low doses are unwell known. However, results from different recent studies suggest that a chronic contamination with low levels of uranium induces subtle but significant levels. Indeed, an internal contamination of rats for several weeks leads to detection of uranium in many cerebral structures, in association with an alteration of short-term memory and an increase of anxiety level. Biological effects of uranium on the metabolisms of xenobiotics, steroid hormones and vitamin D were described in the liver, testis and kidneys. These recent scientific data suggest that uranium could participate to increase of health risks linked to environmental pollution.

Different pattern of brain pro-/anti-oxidant activity between depleted and enriched uranium in chronically exposed rats.

Uranium is not only a heavy metal but also an alpha particle emitter. The main toxicity of uranium is expected to be due to chemiotoxicity rather than to radiotoxicity. Some studies have demonstrated that uranium induced some neurological disturbances, but without clear explanations. A possible mechanism of this neurotoxicity could be the oxidative stress induced by reactive oxygen species imbalance. The aim of the present study was to determine whether a chronic ingestion of uranium induced anti-oxidative defence mechanisms in the brain of rats. Rats received depleted (DU) or 4% enriched (EU) uranyl nitrate in the drinking water at 2mg(-1)kg(-1)day(-1) for 9 months. Cerebral cortex analyses were made by measuring mRNA and protein levels and enzymatic activities. Lipid peroxidation, an oxidative stress marker, was significantly enhanced after EU exposure, but not after DU. The gene expression or activity of the main antioxidant enzymes, i.e. superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), increased significantly after chronic exposure to DU. On the contrary, oral EU administration induced a decrease of these antioxidant enzymes. The NO-ergic pathway was almost not perturbed by DU or EU exposure. Finally, DU exposure increased significantly the transporters (Divalent-Metal-Transporter1; DMT1), the storage molecule (ferritin) and the ferroxidase enzyme (ceruloplasmin), but not EU. These results illustrate that oxidative stress plays a key role in the mechanism of uranium neurotoxicity. They showed that chronic exposure to DU, but not EU, seems to induce an increase of several antioxidant agents in order to counteract the oxidative stress. Finally, these results demonstrate the importance of the double toxicity, chemical and radiological, of uranium.

Lessons from recent accidents in radiation therapy in France.

Many accidents in radiotherapy have been reported in France over the last years. This is due to the recent legal obligation to declare to the national safety authorities any significant incident relative to the use of ionising radiation including medical applications. The causes and consequences of the most serious events in radiotherapy are presented in this paper. Lessons can be learned from possible technical dysfunctions, from human errors or organisational weaknesses as to how such events can be prevented. The technical aspects are addressed here: in particular, dosimetric issues.

Enriched uranium affects the expression of vitamin D receptor and retinoid X receptor in rat kidney.

An increasing awareness of the radiological impact of the nuclear power industry and other nuclear technologies is observed nowadays on general population. This led to renew interest to assess the health impact of the use of enriched uranium (EU). The aim of this work was to investigate in vivo the effects of a chronic exposure to EU on vitamin D(3) metabolism, a hormone essential in mineral and bone homeostasis. Rats were exposed to EU in their drinking water for 9 months at a concentration of 40 mg l(-1) (1mg/rat day). The contamination did not change vitamin D plasma level. Vitamin D receptor (vdr) and retinoid X receptor alpha (rxralpha), encoding nuclear receptors involved in the biological activities of vitamin D, showed a lower expression in kidney, while their protein levels were paradoxically increased. Gene expression of vitamin D target genes, epithelial Ca(2+) channel 1 (ecac1) and Calbindin-D28k (cabp-d28k), involved in renal calcium transport were decreased. Among the vitamin D target organs examined, these molecular modifications occurred exclusively in the kidney, which confirms that this organ is highly sensitive to uranium exposure. In conclusion, this study showed that a chronic exposure to EU affects both mRNA and protein expressions of renal nuclear receptors involved in vitamin D metabolism, without any modification of the circulating vitamin D.

New biological indicators to evaluate and monitor radiation-induced damage: an accident case report.

The aim of this work was to use several new biological indicators to evaluate damage to the main physiological systems in a victim exposed accidentally to ionizing radiation. Blood samples were used for biological dosimetry and for measurement of the plasma concentrations of several molecules: Flt3 ligand to assess the hematopoietic system, citrulline as an indicator of the digestive tract, and several oxysterols as lipid metabolism and vascular markers. The cytogenetic evaluation estimated the dose to the victim to be between 4.2 and 4.8 Gy, depending on the methodology used. Monitoring the Flt3 ligand demonstrated the severity of bone marrow aplasia. In contrast, the citrulline concentration showed the absence of gastrointestinal damage. Variations in oxysterol concentrations suggested radiation-induced damage to the liver and the cardiovascular system. These results were correlated with those from classic biochemical markers, which demonstrated severe damage to the hematopoietic system and suggested the appearance of subclinical damage to the liver and cardiovascular system. These results demonstrate for the first time the importance of a multiparameter biological approach in the evaluation of radiation damage after accidental irradiation.

New approach to radiation burn treatment by dosimetry-guided surgery combined with autologous mesenchymal stem cell therapy.

The therapeutic management of severe radiation burns remains a challenging issue. Conventional surgical treatment (excision and skin autograft or rotation flap) often fails to prevent unpredictable and uncontrolled extension of the radiation necrotic process. We report here an innovative therapeutic strategy applied to the victim of a radiation accident (December 15, 2005) with an iridium gammagraphy radioactive source (192Ir, 3.3 TBq). The approach combined numerical dosimetry-guided surgery with cellular therapy using mesenchymal stem cells. A very severe buttock radiation burn (2000 Gy at the center of the skin surface lesion) of a 27-year-old Chilean victim was widely excised (10 cm in diameter) using a physical and anatomical dose reconstruction in order to better define the limit of the surgical excision in apparently healthy tissues. A secondary extension of the radiation necrosis led to a new excision of fibronecrotic tissues associated with a local cellular therapy using autologous expanded mesenchymal stem cells as a source of trophic factors to promote tissue regeneration. Bone marrow-derived mesenchymal stem cells were expanded according to a clinical-grade technique using closed culture devices and serum-free medium enriched in human platelet lysate. The clinical evolution (radiation pain and healing progression) was favorable and no recurrence of radiation inflammatory waves was observed during the 11 month patient's follow-up. This novel multidisciplinary therapeutic approach combining physical techniques, surgical procedures and cellular therapy with adult stem cells may be of clinical relevance for improving the medical management of severe localized irradiations. It may open new prospects in the field of radiotherapy complications.

Effects of chronic 137Cs ingestion on barrier properties of jejunal epithelium in rats.

Environmental contamination by 137Cs is of particular public health interest because of the various sources of fallout originating from nuclear weapons, radiological source disruptions, and the Chernobyl disaster. This dispersion may lead to a chronic ecosystem contamination and subsequent ingestion of contaminated foodstuffs. The aim of this study was to thus determine the impact of a chronic ingestion of low-dose 137Cs on small intestine functions in rats. The animals received 150 Bq per day in drinking water over 3 mo. At these environmental doses, 137Cs contamination did not modify the crypt and villus architecture. In addition, epithelial integrity was maintained following the chronic ingestion of 137Cs, as demonstrated by histological analyses (no breakdown of the surface mucosa) and electrical transepithelial parameters (no change in potential difference and tissue conductance). Furthermore, cesium contamination seemed to induce contradictory effects on the apoptosis pathway, with an increase in the gene expression of Fas/FasL and a decrease in the apoptotic cell number present in intestinal mucosa. No marked inflammation was observed following chronic ingestion of 137Cs, as indicated by neutrophil infiltration and gene expression of cytokines and chemokines. Results indicated no imbalance in the Th1/Th2 response induced by cesium at low doses. Finally, evaluation of the functionality of the jejunal epithelium in rats contaminated chronically with 137Cs did not demonstrate changes in the maximal response to carbachol, nor in the cholinergic sensitivity of rat jejunal epithelium. In conclusion, this study shows that chronic ingestion of 137Cs over 3 mo at postaccidental doses exerts few biological effects on the epithelium of rat jejunum with regard to morphology, inflammation status, apoptosis/proliferation processes, and secretory functions.

Comparison of the effects of enriched uranium and 137-cesium on the behaviour of rats after chronic exposure.

PURPOSE: A radionuclide that accumulates in the central nervous system is likely to exert both a chemical and a radiological effect. The present study aimed at assessing the behavioral effect of two radionuclides previously shown to accumulate in the central nervous system after chronic exposure--uranium and cesium. MATERIALS AND METHODS: Rats were exposed for 9 months to drinking water contaminated with either enriched uranium at a dosage of 40 mg U x l(-1) or 137-cesium at a dosage of 6500 Bq x l(-1), which correspond to the highest concentrations measured in some wells in the south of Finland (uranium) or in the milk in Belarus in the year following the Chernobyl accident (137-cesium). RESULTS: At this level of exposure, 137-cesium had no effect on the locomotor activity measured in an open-field, on immobility time in a forced swimming test, on spontaneous alternation in a Y-maze and on novel object exploration in an object recognition test. Enriched uranium exposure specifically reduced the spontaneous alternation measured in the Y-maze after 3 and 9 months exposure although it did not affect the other parameters. CONCLUSION: Enriched uranium exposure altered the spatial working memory capacities and this effect was correlated with previously described accumulation of uranium in the hippocampus which is one of the cerebral areas involved in this memory system.

Parental exposure to enriched uranium induced delayed hyperactivity in rat offspring.

Several recent reports suggest that chronic exposure to uranium could induce behavioural effects in adult rats. As the immature brains are known to be more susceptible to toxic effects, rats were observed in an open field, in a Y-maze and in an elevated plus-maze at 2, 5 and 9 months old after exposure to enriched uranium (40 mg l-1) during gestation and lactation. The rats exposed to enriched uranium showed a significant decrease in alternation in the Y-maze at 2 months old which reflects a slight decrease in the spatial working memory capacities as previously described in adult rats. However, the main result was a delayed hyperactivity in the rats exposed to enriched uranium, which appeared to a slight extent at 5 months old and was more evident at 9 months old. Although this effect could not be directly explained by some uranium accumulation in the target organs, this experiment showed that early exposure to enriched uranium can induce a very late effect on the rat behaviour and that such studies should not be restricted to the effects observed on young rats.

In vivo effects of chronic contamination with depleted uranium on vitamin D3 metabolism in rat.

The extensive use of depleted uranium (DU) in today's society results in the increase of the number of human population exposed to this radionuclide. The aim of this work was to investigate in vivo the effects of a chronic exposure to DU on vitamin D(3) metabolism, a hormone essential in mineral and bone homeostasis. The experiments were carried out in rats after a chronic contamination for 9 months by DU through drinking water at 40 mg/L (1 mg/rat/day). This dose corresponds to the double of highest concentration found naturally in Finland. In DU-exposed rats, the active vitamin D (1,25(OH)(2)D(3)) plasma level was significantly decreased. In kidney, a decreased gene expression was observed for cyp24a1, as well as for vdr and rxralpha, the principal regulators of CYP24A1. Similarly, mRNA levels of vitamin D target genes ecac1, cabp-d28k and ncx-1, involved in renal calcium transport were decreased in kidney. In the brain lower levels of messengers were observed for cyp27a1 as well as for lxrbeta, involved in its regulation. In conclusion, this study showed for the first time that DU affects both the vitamin D active form (1,25(OH)(2)D(3)) level and the vitamin D receptor expression, and consequently could modulate the expression of cyp24a1 and vitamin D target genes involved in calcium homeostasis.

Effect of acetaminophen administration to rats chronically exposed to depleted uranium.

The extensive use of depleted uranium (DU) in both civilian and military applications results in the increase of the number of human beings exposed to this compound. We previously found that DU chronic exposure induces the expression of CYP enzymes involved in the metabolism of xenobiotics (drugs). In order to evaluate the consequences of these changes on the metabolism of a drug, rats chronically exposed to DU (40mg/l) were treated by acetaminophen (APAP, 400mg/kg) at the end of the 9-month contamination. Acetaminophen is considered as a safe drug within the therapeutic range but in the case of overdose or in sensitive animals, hepatotoxicity and nephrotoxicity could occur. In the present work, plasma concentration of APAP was higher in the DU group compared to the non-contaminated group. In addition, administration of APAP to the DU-exposed rats increased plasma ALT (p<0.01) and AST (p<0.05) more rapidly than in the control group. Nevertheless, no histological alteration of the liver was observed but renal injury characterized by incomplete proximal tubular cell necrosis was higher for the DU-exposed rats. Moreover, in the kidney, CYP2E1 gene expression, an important CYP responsible for APAP bioactivation and toxicity, is increased (p<0.01) in the DU-exposed group compared to the control group. In the liver, CYP's activities were decreased between control and DU-exposed rats. These results could explain the worse elimination of APAP in the plasma and confirm our hypothesis of a modification of the drug metabolism following a DU chronic contamination.