From homogeneous to fractal normal and tumorous microvascular networks in the brain

We studied normal and tumorous three-dimensional (3D) microvascular networks in primate and rat brain. Tissues were prepared following a new preparation technique intended for high-resolution synchrotron tomography of microvascular networks. The resulting 3D images with a spatial resolution of less than the minimum capillary diameter permit a complete description of the entire vascular network for volumes as large as tens of cubic millimeters. The structural properties of the vascular networks were investigated by several multiscale methods such as fractal and power- spectrum analysis. These investigations gave a new coherent picture of normal and pathological complex vascular structures. They showed that normal cortical vascular networks have scale- invariant fractal properties on a small scale from 1.4 lm up to 40 to 65 lm. Above this threshold, vascular networks can be considered as homogeneous. Tumor vascular networks show similar characteristics, but the validity range of the fractal regime extend to much larger spatial dimensions. These 3D results shed new light on previous two dimensional analyses giving for the first time a direct measurement of vascular modules associated with vessel-tissue surface exchange

Vascular network segmentation: an unsupervised approach

Micro-tomography produces high resolution images of biological structures such as vascular networks. In this paper, we present a new approach for segmenting vascular network into pathological and normal regions from considering their micro-vessel 3D structure only. We consider a partition of the volume obtained by a watershed algorithm based on the distance from the nearest vessel. Each territory is characterized by its volume and the local vascular density. The volume and density maps are first regularized by minimizing the total variation. Then, a new approach is proposed to segment the volume from the two previous restored images based on hypothesis testing. Results are presented on 3D micro-tomographic images of the brain micro-vascular network

High-Precision Radiosurgical Dose Delivery by Interlaced Microbeam Arrays of High-Flux Low-Energy Synchrotron X-Rays

Microbeam Radiation Therapy (MRT) is a preclinical form of radiosurgery dedicated to brain tumor treatment. It uses micrometer-wide synchrotron-generated X-ray beams on the basis of spatial beam fractionation. Due to the radioresistance of normal brain vasculature to MRT, a continuous blood supply can be maintained which would in part explain the surprising tolerance of normal tissues to very high radiation doses (hundreds of Gy). Based on this well described normal tissue sparing effect of microplanar beams, we developed a new irradiation geometry which allows the delivery of a high uniform dose deposition at a given brain target whereas surrounding normal tissues are irradiated by well tolerated parallel microbeams only. Normal rat brains were exposed to 4 focally interlaced arrays of 10 microplanar beams (52 µm wide, spaced 200 µm on-center, 50 to 350 keV in energy range), targeted from 4 different ports, with a peak entrance dose of 200Gy each, to deliver an homogenous dose to a target volume of 7 mm3 in the caudate nucleus. Magnetic resonance imaging follow-up of rats showed a highly localized increase in blood vessel permeability, starting 1 week after irradiation. Contrast agent diffusion was confined to the target volume and was still observed 1 month after irradiation, along with histopathological changes, including damaged blood vessels. No changes in vessel permeability were detected in the normal brain tissue surrounding the target. The interlacing radiation-induced reduction of spontaneous seizures of epileptic rats illustrated the potential pre-clinical applications of this new irradiation geometry. Finally, Monte Carlo simulations performed on a human-sized head phantom suggested that synchrotron photons can be used for human radiosurgical applications. Our data show that interlaced microbeam irradiation allows a high homogeneous dose deposition in a brain target and leads to a confined tissue necrosis while sparing surrounding tissues. The use of synchrotron-generated X-rays enables delivery of high doses for destruction of small focal regions in human brains, with sharper dose fall-offs than those described in any other conventional radiation therapy

AGuIX® from bench to bedside-Transfer of an ultrasmall theranostic gadolinium-based nanoparticle to clinical medicine

International audienceAGuIX® are sub-5 nm nanoparticles made of a polysiloxane matrix and gadolinium chelates. This nanoparticle has been recently accepted in clinical trials in association with radiotherapy. This review will summarize the principal preclinical results that have led to first in man administration. No evidence of toxicity has been observed during regulatory toxicity tests on two animal species (rodents and monkeys). Biodistributions on different animal models have shown passive uptake in tumours due to enhanced permeability and retention effect combined with renal elimination of the nanoparticles after intravenous administration. High radiosensitizing effect has been observed with different types of irradiations in vitro and in vivo on a large number of cancer types (brain, lung, melanoma, head and neck…). The review concludes with the second generation of AGuIX nanoparticles and the first preliminary results on human

Intérêt du rayonnement synchrotron dans la thérapie des tumeurs cérébrales (méthodologie et applications précliniques )

La Thérapie par MicroFaisceaux (MRT) et la Thérapie Stéréotaxique par Rayonnement Synchrotron (SSRT) sont des techniques innovantes de radiothérapie expérimentale développées actuellement à l'ESRF. L'utilisation de modèles tumoraux différents pour chaque technique limite leur comparaison. En MRT, sur rats porteurs de tumeur 9L, la médiane de survie des rats contrôle est doublée (de 20 jours à 40 jours) lors d'irradiation avec un espacement de 200 JLm entre les microfaisceaux voire triplée (67 jours) à 100 JLm d'espacement (mais provoquant alors d'importantes lésions du tissu sain). L'influence importante du collimateur multifentes, a également été démontrée. La combinaison de diverses drogues avec la technique de MRT a été testée. Des résultats prometteurs (médiane de survie de 40 jours et 30% de survivants à long terme) sont obtenus en injectant du gadolinium en intracérébral avant une irradiation MRT en faisceaux croisés à 460 Gy. De plus, l'irradiation MRT de tumeurs à stade plus précoce permet de quadruplé la médiane de survie (79 jours) et d'obtenir 30% de survivants à long terme. La mise en place d'un ciblage de la tumeur par imagerie avant l'irradiation et l'utilisation d'un collimateur adapté permettront d'améliorer encore ces résultats. Les différences entre les deux modèles tumoraux utilisés en MRT (modèle 9L) et en SSRT (modèle F98) étant importantes des expériences comparatives MRT/SSRT ont été réalisées sur ces deux modèles. Les résultats obtenus montrent une efficacité proche des 2 techniques sur le modèle F98 et une meilleure efficacité de la MRT sur le modèle 9L. Ces résultats pourront permettre d'orienter le type tumoral adapté à chaque technique.Microbeam Radiation Therapy (MRT) and Stereotactic Synchrotron Radiation Therapy (SSRT) are innovative techniques currently developed at the European Synchrotron Radiation Facility. These techniques led to promising, but rarely reproduced, results. The use of different tumoral models for each techniques limit comparisons. MRT experiments on rats bearing 9L tumors 14 days after implantation displayed a double median survival time (from 20 to 40 days) with a 200 JLm spacing irradiation, while a 100 JLm spacing irradiation tripled this median (67 days) but damaged normal tissue. The impact of the device dividing synchrotron beam into microbeams, named multislit collimator, was also demonstrated. Combination of drugs with MRT irradiation was tested. Promising results (median survival time: 40 days and 30 % oflong term survivors) were obtained with an intratumoral injection of gadolinium coupled with a crossfiring MRT irradiation at 460 Gy. Moreover, earlier MRT irradiation (tumor at DIO) quadrupled the median survival time (79 days) with 30% of long term survivors. A new imaging device to target the tumor before irradiation and an adapted collimator will increased the MRT results. As the differences existing between tumoral models used in MRT (9L models) and in SSRT (F98 models) are major, MRT/SSRT comparative experiments were realized on these two models. Results showed that the 2 techniques have the same efficacy on F98 model and that the MRT is more effective on 9L mode!. This can help to define adapted tumor type for these techniques.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Réponse transcriptomique des tissus cérébraux sains et tumoraux à la radiothérapie par microfaisceaux synchrotron

La radiothérapie par microfaisceaux (MRT) synchrotron est une méthode de radiothérapie alternative pour les tumeurs cérébrales, qui présente l'avantage unique de pouvoir déposer de très hautes doses d'irradiation (plusieurs 100aines de Gy) au niveau de la masse tumorale. En effet, le fractionnement spatial des rayons X en microfaisceaux parallèles de quelques dizaines de micromètres s'est montré efficace dans le traitement des tumeurs cérébrales du rongeur tout en préservant le tissu cérébral péritumoral. Pour autant, son mode d'action sur le plan biologique n'est qu'en partie connu. Si l'effet différentiel de cette irradiation sur les vaisseaux sains et tumoraux a pu être démontré ces dernières années, il ne peut expliquer à lui seul l'efficacité de la MRT. Dans ce travail, nous avons établi une description de la réponse transcriptomique précoce des tissus sains et tumoraux (gliosarcome 9L) à la MRT et les fonctions biologiques et voies de signalisation associées. Ces résultats constituent une base de données interrogeable à partir d'hypothèses précises. Cette base a ainsi permis d'identifier des transcrits impliqués dans la réponse de la tumeur à la MRT et dont l'inhibition n'interfèrerait pas avec la réparation des tissus sains : nous avons proposé 3 cibles potentielles qui permettraient d'augmenter l'index thérapeutique de la MRT. (i) L'inhibition radio-induite d'un groupe de 13 gènes (Plk1, Cdc20, Ccnb1, Pttg1, Bub1, Dlgap5, Cenpf, Kif20a, Traf4af1, Depdc1b, Mxd3, Cenpe et Cenpf), participerait au contrôle tumoral précoce après MRT par la perturbation de la division cellulaire et pourrait être amplifié pour prolonger l'inhibition de la croissance tumorale. (ii) La mise à profit de l'activation du promoteur de Clecsf6 au sein des tumeurs irradiées permettrait la surexpression locale, via les monocytes modifiés et infiltrés, de protéine d'intérêt thérapeutique. (iii) Areg (codant pour l'Amphiréguline) est surexprimé au sein du tissu tumoral après MRT et son implication connue dans la chimio/radiorésistance nous conduit à considérer que son inhibition pourrait être une stratégie de renforcement des effets de la MRT. Par ailleurs, nous avons montré que la MRT engendrait de meilleurs résultats sur le contrôle tumoral et la survie animale qu'une irradiation synchrotron en champ plein (avec une dose équivalente à la vallée MRT). Cependant, aucune différence transcriptomique ne pouvant soutenir cet effet n'a pu être mis en évidence.Synchrotron Microbeam Radiation Therapy (MRT) is a novel form of radiosurgery of brain tumors which allows high dose deposition (few hundreds of Gy) in pathologic tissues. The spatial fractionation of the incident beam into arrays of near-parallel microbeams has shown efficiency on brain tumors implanted in rodents while sparing normal tissues. The preferential effects observed on tumor vessels could not entirely explain the efficiency of MRT and other biological mechanisms might be involved in tumor control. In this work, we described the early whole transcriptomic responses of normal and tumoral (9L gliosarcoma) tissues to MRT and the associated biofunctions and pathways. This provides a questionable data base which can be used by the whole MRT community. This base allows to identify transcripts involved in tumor response to MRT and which inhibition would have no consequence in healthy tissue repair. We identified 3 relevant targets which might increase the therapeutic index of MRT. (i) The radio-induced inhibition of a cluster of 13 genes (Plk1, Cdc20, Ccnb1, Pttg1, Bub1, Dlgap5, Cenpf, Kif20a, Traf4af1, Depdc1b, Mxd3, Cenpe and Cenpf) may be involved in tumor control after MRT through the deregulation of cell division and could be amplified to continue the tumor growth inhibition. (ii) We might benefit from the activation of the Clecsf6 promoter in irradiated tumors by delivering, via modified and injected monocytes, some therapeutic proteins. (iii) Finally, Areg (encoding for Amphiregulin) is overexpressed in tumors after MRT and its involvement described in chimio/radioresistance enable to consider that its inhibition might help in tumor control after irradiation. We also showed that MRT induces a greater tumor control and survival rates compared with similar broad beam irradiations but no differences in transcriptomic responses have been highlighted.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Gadolinium-Based Nanoparticles and Radiation Therapy for Multiple Brain Melanoma Metastases and brain tumors: from bench to beside.

International audienceMore than half of all clinical cancer patients undergo radiation therapy. Besides the poor prognosis for multiple brain metastases and brain tumors, the delivery of curative radiation dose to induce tumor-kill is strongly restricted by the healthy proximal brain. We describe a nanoparticle which can act as MR contrast agent and radiosensitizer concomitantly, for the detection, monitoring and treatment of brain cancers

Mapping the zonal organization of tumor perfusion and permeability in a rat glioma model by using dynamic contrast-enhanced synchrotron radiation CT.

International audiencePURPOSE: To depict and analyze in vivo the tumor zone organization of C6 gliomas depicted on quantitative parametric maps obtained with dynamic contrast material-enhanced synchrotron radiation computed tomography (CT) in a tightly controlled data-processing protocol. MATERIALS AND METHODS: Animal use was compliant with official French guidelines and was assessed by the local Internal Evaluation Committee for Animal Welfare and Rights. Fifteen Wistar rats with orthotopically implanted gliomas were studied at monochromatic synchrotron radiation CT after receiving a bolus injection of contrast material. The iodine concentration maps were analyzed by using a compartmental model selected from among a package of models. Choice of model and assessment of the relevance of the model were guided by quality criteria. Tissue blood flow (F(T)), tissue blood volume fraction (V(T)), permeability-surface area product (PS), artery-to-tissue delay (D(A-T)), and vascular mean transit time (MTT) maps were obtained. Parametric map findings were compared with histologic findings. Local regions of interest were selected in the contralateral hemisphere and in several tumor structures to characterize the tumor microvasculature. Differences in parameter values between regions were assessed with the Wilcoxon method. RESULTS: Whole-tumor parameters were expressed as means +/- standard errors of the mean: Mean F(T), V(T), PS, and D(A-T) values and MTT were 61.4 mL/min/100 mL +/- 15.3, 2.4% +/- 0.4, 0.37 mL/min/100 mL +/- 0.11, 0.24 second +/- 0.06; and 3.9 seconds +/- 0.83, respectively. MTT and mean PS were significantly lower (P < .01) in the normal contralateral tissue: 1.10 seconds +/- 0.06 and < or = 10(-5) mL/min/100 mL, respectively. Tumor regions were characterized by significantly different (P < .05) F(T) and V(T) pairs: 108 mL/min/100 mL and 3.66%, respectively, at the periphery; 45.9 mL/min/100 mL and 1.91%, respectively, in the intermediate zone; 5.1 mL/min/100 mL and 0.42%, respectively, in the center; and 210 mL/min/100 mL and 6.82%, respectively, in the maximal value region. CONCLUSION: Fine mapping of the glioma microcirculation is feasible with dynamic contrast-enhanced synchrotron radiation CT performed with well-controlled analytic protocols. Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2501071929/DC1

Gadolinium-Based Nanoparticles AGuIX and Radiation Therapy for Multiple Brain Melanoma Metastases and Brain Tumors: From Bench to Bedside

National audienceMore than half of all clinical cancer patients undergo radiation therapy. Besides the poor prognosis for multiple brain metastases and brain tumors, the delivery of curative radiation dose to eradicate tumor is strongly restricted by the healthy proximal brain. We describe a nanoparticle which can act as MR contrast agent and radiosensitizer concomitantly, for the detection, monitoring and treatment of brain cancers.Biodistribution, toxicity and pharmacokinetic studies were carried out in rodents and cynomolgus monkeys to demonstrate the safety of the nanoparticles after intravenous injection. The MR imaging properties of the nanoparticles were used to monitor their tumor accumulation in rodent bearing brain tumors. In vitro and in vivo efficacy of the nanoparticles was evaluated in rodent bearing brain tumors.The regulatory toxicity investigations demonstrated the absence of any ante- or post-mortem finding in rodent and nonhuman primates after repeated administration of nanoparticles; thus, the no-observed-effect level (NOEL) was determined and a human equivalent dose of 120 mg/kg was defined. In rodents, MR imaging indicated the renal elimination of the nanoparticles and their passive accumulation in the tumor region for several hours. The combination of nanoparticles and irradiation created significant dose enhancement in vitro, and improved the survival of rodent bearing aggressive brain tumor.The therapeutic efficacy of AGuIX has been demonstrated in aggressive pathologies, i.e. multiple brain metastases and brain tumors. In addition, the nanoparticles possess natural T1-MRI contrast agent properties, conferring a dual-property for image-guided radiation therapy. The data in rodents and nonhuman primates clearly demonstrates and justifies their clinical translational potential. The upcoming first-in-man clinical trial will investigated both imaging and radiation therapy improvement for advanced precision medicine

Extraction et caractérisation de régions saines et pathologiques à partir de micro-tomographie RX du système vasculaire cérébral

National audienceIn this paper, we consider X-ray micro-tomography representing the brain vascular network. We define the local vascular territories as the regions obtained after a watershed algorithm applied on the distance map. The obtained graph is then regularized by a Markov random field approach. The optimization is performed using a graph cut algorithm. We show that the resulting segmentation exhibits three classes corresponding to normal tissue, tumour and an intermediate region