Phototruncation cell tracking with near-infrared photoimmunotherapy using heptamethine cyanine dye to visualise migratory dynamics of immune cells.

BACKGROUND: Noninvasive in vivo cell tracking is valuable in understanding the mechanisms that enhance anti-cancer immunity. We have recently developed a new method called phototruncation-assisted cell tracking (PACT), that uses photoconvertible cell tracking technology to detect in vivo cell migration. This method has the advantages of not requiring genetic engineering of cells and employing tissue-penetrant near-infrared light. METHODS: We applied PACT to monitor the migration of immune cells between a tumour and its tumour-draining lymph node (TDLN) after near-infrared photoimmunotherapy (NIR-PIT). FINDINGS: PACT showed a significant increase in the migration of dendritic cells (DCs) and macrophages from the tumour to the TDLN immediately after NIR-PIT. This migration by NIR-PIT was abrogated by inhibiting the sphingosine-1-phosphate pathway or Gαi signaling. These results were corroborated by intranodal immune cell profiles at two days post-treatment; NIR-PIT significantly induced DC maturation and increased and activated the CD8+ T cell population in the TDLN. Furthermore, PACT revealed that NIR-PIT significantly enhanced the migration of CD8+ T cells from the TDLN to the tumour four days post-treatment, which was consistent with the immunohistochemical assessment of tumour-infiltrating lymphocytes and tumour regression. INTERPRETATION: Immune cells dramatically migrated between the tumour and TDLN following NIR-PIT, indicating its potential as an immune-stimulating therapy. Also, PACT is potentially applicable to a wide range of immunological research. FUNDING: This work was supported by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Centre for Cancer Research (grant number: ZIA BC011513 and ZIA BC011506).

Longitudinal Magnetic Resonance Imaging Tracking of Transplanted Neural Progenitor Cells in the Spinal Cord Utilizing the Bright-Ferritin Mechanism.

Human neural progenitor cells (hNPCs) hold promise for treating spinal cord injury. Studies to date have focused on improving their regenerative potential and therapeutic effect. Equally important is ensuring successful delivery and engraftment of hNPCs at the injury site. Unfortunately, no current imaging solution for cell tracking is compatible with long-term monitoring in vivo. The objective of this study was to apply a novel bright-ferritin magnetic resonance imaging (MRI) mechanism to track hNPC transplants longitudinally and on demand in the rat spinal cord. We genetically modified hNPCs to stably overexpress human ferritin. Ferritin-overexpressing (FT) hNPCs labeled with 0.2 mM manganese provided significant T1-induced bright contrast on in vitro MRI, with no adverse effect on cell viability, morphology, proliferation, and differentiation. In vivo, 2 M cells were injected into the cervical spinal cord of Rowett nude rats. MRI employed T1-weighted acquisitions and T1 mapping on a 3 T scanner. Conventional short-term cell tracking was performed using exogenous Mn labeling prior to cell transplantation, which displayed transient bright contrast on MRI 1 day after cell transplantation and disappeared after 1 week. In contrast, long-term cell tracking using bright-ferritin allowed on-demand signal recall upon Mn supplementation and precise visualization of the surviving hNPC graft. In fact, this new cell tracking technology identified 7 weeks post-transplantation as the timepoint by which substantial hNPC integration occurred. Spatial distribution of hNPCs on MRI matched that on histology. In summary, bright-ferritin provides the first demonstration of long-term, on-demand, high-resolution, and specific tracking of hNPCs in the rat spinal cord.

Dual Magnetic Particle Imaging and Akaluc Bioluminescence Imaging for Tracking Cancer Cell Metastasis.

Magnetic particle imaging (MPI) provides hotspot tracking and direct quantification of superparamagnetic iron oxide nanoparticle (SPIO)-labelled cells. Bioluminescence imaging (BLI) with the luciferase reporter gene Akaluc can provide complementary information on cell viability. Thus, we explored combining these technologies to provide a more holistic view of cancer cell fate in mice. Akaluc-expressing 4T1Br5 cells were labelled with the SPIO Synomag-D and injected into the mammary fat pads (MFP) of four nude mice. BLI was performed on days 0, 6 and 13, and MPI was performed on days 1, 8 and 14. Ex vivo histology and fluorescence microscopy of MFP and a potential metastatic site was conducted. The BLI signal in the MFP increased significantly from day 0 to day 13 (p < 0.05), mirroring tumor growth. The MPI signal significantly decreased from day 1 to day 14 (p < 0.05) due to SPIO dilution in proliferating cells. Both modalities detected secondary metastases; however, they were visualized in different anatomical regions. Akaluc BLI complemented MPI cell tracking, allowing for longitudinal measures of cell viability and sensitive detection of distant metastases at different locations. We predict this multimodal imaging approach will help to evaluate novel therapeutics and give a better understanding of metastatic mechanisms.

Intravital optical imaging for immune cell tracking after photoimmunotherapy with plasmonic gold nanostars.

Bladder cancer has been ranked as one of the most commonly occurring cancers in men and women with approximately half of the diagnoses being the late stage and/or metastatic diseases. We have developed a novel cancer treatment by combining gold nanostar-mediated photothermal therapy with checkpoint inhibitor immunotherapy to treat bladder cancer. Experiment results with a murine animal model demonstrated that our developed photoimmunotherapy therapy is more efficacious than any individual studied treatment. In addition, we used intravital optical imaging with a dorsal skinfold window chamber animal model to study immune responses and immune cell accumulation in a distant tumor following our photoimmunotherapy. The mice used have the CX3CR1-GFP receptor on monocytes, natural killer cells, and dendritic cells allowing us to dynamically track their presence by fluorescence imaging. Our proof-of-principle study results showed that the photoimmunotherapy triggered anti-cancer immune responses to generate anti-cancer immune cells which accumulate in metastatic tumors. Our study results illustrate that intravital optical imaging is an efficient and versatile tool to investigate immune responses and mechanisms of photoimmunotherapy in future studies.

Profil clinique, biologique et traitement des drépanocytaires régulièrement suivis au Centre Hospitalier Universitaire de Libreville / Clinical, biological and treatment profile of sickle cell patients regularly followed at Libreville University Hospital Center

Introduction: La mise en place depuis Septembre 2016 au Centre Hospitalier Universitaire (CHUL) d'une consultation d'hématologie dédiée aux adultes drépanocytaires a été l'occasion de mener cette étude dont le but principal était d'établir les profils clinique et paraclinique de l'adulte drépanocytaire régulièrement suivi.Patients et méthodes : Il s'agissait d'une étude rétrospective. La population d'étude était constituée de patients drépanocytaires homozygotes de 18 ans et plus, qui avaient effectués au moins trois consultations d'hématologie sur une année. Les informations recueillies, après étude du dossier médical et entretien téléphonique avec le patient, concernaient les données socio-démographiques, l'histoire de la drépanocytose, les antécédents, les complications de la maladie, les examens biologiques et radiologiques et le traitement.Résultats : Au total 88 patients répondaient aux critères d'inclusion sur les 233 drépanocytaires vus durant la période de l'étude. L'âge moyen était de 30,4 ± 7,8 ans. L'interrogatoire révélait que la crise vaso-occlusive (CVO) était la principale complication aiguë et la lithiase vésiculaire (36,3%) la première complication chronique. L'hémoglobine moyenne était de 7,8 g/dl et pour 49,3% des patients elle se situait entre 7 et 9 g/dl. Les leucocytes étaient augmentés dans 65,7%. L'échographie cardiaque réalisée chez 35 patients retrouvait 11,1% d'hypertension artérielle pulmonaire et 22,8% d'hypertrophie ventriculaire gauche. L'intensité de la crise douloureuse motivait une consultation au service des urgences du CHU dans 81,6% des cas dont plus de 62% déploraient un retard dans l'exécution de cette prise en charge bien qu'ils en aient été satisfaits dans 54,9% des cas.Conclusion : Les drépanocytaires adultes régulièrement suivis au CHUL sont peu nombreux. La transition entre le suivi pédiatrique et adulte doit se faire avec une transmission des informations du dossier médical sur l'histoire de la drépanocytose.

Introduction: The establishment since September 2016 at the University Hospital Center (CHUL) of a hematology consultation dedicated to adults with sickle cell disease was an opportunity to conduct this study, the main purpose of which was to establish the clinical and paraclinical profiles of the adults with sickle cell disease regularly monitored. Patients and methods: This was a retrospective study. The study population consisted of homozygous sickle cell patients aged 18 and over, who had performed at least three hematology consultations over a year. The information collected, after studying the medical file and telephone interview with the patient, concerned socio-demographic data, history of sickle cell disease, history, complications of the disease, biological and radiological examinations and treatment. Results: A total of 88 patients met the inclusion criteria out of the 233 sickle cell patients seen during the study period. The mean age was 30.4 ± 7.8 years. The questioning revealed that vaso-occlusive crisis (VOC) was the main acute complication and cholelithiasis (36.3%) the first chronic complication. The average hemoglobin was 7.8 g/dl and for 49.3% of the patients it was between 7 and 9 g/dl. Leukocytes were increased in 65.7%. Cardiac ultrasound performed in 35 patients found 11.1% pulmonary arterial hypertension and 22.8% left ventricular hypertrophy. The intensity of the painful crisis motivated a consultation in the emergency department of the CHU in 81.6% of cases, of which more than 62% complained of a delay in the execution of this care although they were satisfied with it in 54 .9% of cases.Conclusion: Few adult sickle cell sufferers are regularly monitored at the CHUL. The transition between pediatric and adult follow-up must be made with a transmission of information from the medical file on the history of sickle cell disease

Micron-sized iron oxide particles for both MRI cell tracking and magnetic fluid hyperthermia treatment.

Iron oxide particles (IOP) are commonly used for Cellular Magnetic Resonance Imaging (MRI) and in combination with several treatments, like Magnetic Fluid Hyperthermia (MFH), due to the rise in temperature they provoke under an Alternating Magnetic Field (AMF). Micrometric IOP have a high sensitivity of detection. Nevertheless, little is known about their internalization processes or their potential heat power. Two micrometric commercial IOP (from Bangs Laboratories and Chemicell) were characterized by Transmission Electron Microscopy (TEM) and their endocytic pathways into glioma cells were analyzed. Their Specific Absorption Rate (SAR) and cytotoxicity were evaluated using a commercial AMF inductor. T2-weighted imaging was used to monitor tumor growth in vivo after MFH treatment in mice. The two micron-sized IOP had similar structures and r2 relaxivities (100 mM-1 s-1) but involved different endocytic pathways. Only ScreenMAG particles generated a significant rise in temperature following AMF (SAR = 113 W g-1 Fe). After 1 h of AMF exposure, 60% of ScreenMAG-labeled cells died. Translated to a glioma model, 89% of mice responded to the treatment with smaller tumor volume 42 days post-implantation. Micrometric particles were investigated from their characterization to their intracellular internalization pathways and applied in one in vivo cancer treatment, i.e. MFH.

Quantitative MRI cell tracking of immune cell recruitment to tumors and draining lymph nodes in response to anti-PD-1 and a DPX-based immunotherapy.

DPX is a unique T cell activating formulation that generates robust immune responses (both clinically and preclinically) which can be tailored to various cancers via the use of tumor-specific antigens and adjuvants. While DPX-based immunotherapies may act complementary with checkpoint inhibitors, combination therapy is not always easily predictable based on individual therapeutic responses. Optimizing these combinations can be improved by understanding the mechanism of action underlying the individual therapies. Magnetic Resonance Imaging (MRI) allows tracking of cells labeled with superparamagnetic iron oxide (SPIO), which can yield valuable information about the localization of crucial immune cell subsets. In this work, we evaluated the use of a multi-echo, single point MRI pulse sequence, TurboSPI, for tracking and quantifying cytotoxic T lymphocytes (CTLs) and myeloid lineage cells (MLCs). In a subcutaneous cervical cancer model (C3) we compared untreated mice to mice treated with either a single therapy (anti-PD-1 or DPX-R9F) or a combination of both therapies. We were able to detect, using TurboSPI, significant increases in CTL recruitment dynamics in response to combination therapy. We also observed differences in MLC recruitment to therapy-draining (DPX-R9F) lymph nodes in response to treatment with DPX-R9F (alone or in combination with anti-PD-1). We demonstrated that the therapies presented herein induced time-varying changes in cell recruitment. This work establishes that these quantitative molecular MRI techniques can be expanded to study a number of cancer and immunotherapy combinations to improve our understanding of longitudinal immunological changes and mechanisms of action.

A Novel Mediation Strategy of DSS-Induced Colitis in Mice Based on an Iron-Enriched Probiotic and In Vivo Bioluminescence Tracing.

Iron deficiency (ID) caused by blood loss and/or reduced iron absorption is a serious problem influencing health in inflammatory bowel disease (IBD). However, traditional iron supplements may fail to meet no side effect demands for ID of IBD; thus, a new iron supplementation is highly desired to be developed. Herein, for the first time, probiotic Lactobacillus alimentarius NKU556 with an iron-enriching ability was screened from Chinese traditional fermented food then employed to intervene DSS-induced colitis with bioluminescence tracing in mice. As expected, oral administration with NKU556-Fe can remarkably enhance the expression of tight junction proteins and effectively reduce the pro-inflammatory cytokines as well as the oxidative stress on DSS-induced colitis in mice. Meanwhile, in comparison with the FeSO4 group, the intake of NKU556-Fe could suppress the expression of hepcidin derived from the liver and reduce the degradation of FPN1, thereby leading to the increase in the iron absorption of colitis in mice. According to the bioluminescence result, it was believed that the beneficial effects of oral administration with NKU556/NKU556-Fe on DSS-induced colitis in mice were hardly related to its metabolites but associated with its own function. These results concluded that the oral administration of NKU556-Fe could relieve colitis inflammation and increase iron absorption. In summary, current work not only proposed a novel mediation strategy for IBD but also offered some inspirations for future treatment of extraintestinal complications.

Noninvasive Tracking of Implanted Cells: Superparamagnetic Iron Oxide Nanoparticles as a Long-Term, Multimodal Imaging Label.

Superparamagnetic iron oxide (SPIO) nanoparticles can function as specific, long-term multimodal contrast agents for noninvasive imaging studies. Here we describe how to achieve high-resolution, long-term, serial images of single-label transplanted cells through two complementary imaging techniques: magnetic resonance imaging (MRI) and microcomputed tomography (µCT).

Dengue Virus-Polymersome Hybrid Nanovesicles for Advanced Drug Screening Using Real-Time Single Nanoparticle-Virus Tracking.

Dengue virus (DENV) is a major infectious viral pathogen that affects millions of individuals worldwide every year, causing a potentially fatal syndrome, while no commercial antiviral drugs are yet available. To develop an antiviral against dengue fever, it is necessary to understand the relationship between DENV and host cells, which could provide a basis for viral dynamics and identification of inhibitory drug targets. In this study, we designed DiD-loaded and BODIPY-ceramide-encapsulated DENV-polymersome hybrid nanovesicles (DENVSomes) prepared by an extrusion method, which trigger red fluorescence in the endosome and green in the Golgi. DENVSome monitors the dynamics of host cell-virus interaction and tracking in living cells with novel state-of-the-art imaging technologies that show images at high resolution. Also, DENVSome can be exploited to screen whether candidate antiviral drugs interact with DENVs. Consequently, we successfully demonstrated that DENVSome is an efficient tool for tracking and unraveling the mechanisms of replication and drug screening for antiviral drugs of DENV.

A Macro Lens-Based Optical System Design for Phototherapeutic Instrumentation.

Light emitting diode (LED) and ultrasound have been powerful treatment stimuli for tumor cell growth due to non-radiation effects. This research is the first preliminary study of tumor cell suppression using a macro-lens-supported 460-nm LED combined with high-frequency ultrasound. The cell density, when exposed to the LED combined with ultrasound, was gradually reduced after 30 min of induction for up to three consecutive days when 48-W DC, 20-cycle, and 50 Vp-p sinusoidal pulses were applied to the LEDs through a designed macro lens and to the ultrasound transducer, respectively. Using a developed macro lens, the non-directional light beam emitted from the LED could be localized to a certain spot, likewise with ultrasound, to avoid additional undesirable thermal effects on the small sized tumor cells. In the experimental results, compared to LED-only induction (14.49 ± 2.73%) and ultrasound-only induction (13.27 ± 2.33%), LED combined with ultrasound induction exhibited the lowest cell density (6.25 ± 1.25%). Therefore, our measurement data demonstrated that a macro-lens-supported 460-nm LED combined with an ultrasound transducer could possibly suppress early stage tumor cells effectively.

Systematic Intracellular Biocompatibility Assessments of Superparamagnetic Iron Oxide Nanoparticles in Human Umbilical Cord Mesenchyme Stem Cells in Testifying Its Reusability for Inner Cell Tracking by MRI.

Until now, there is no effective method for tracking transplanted stem cells in human. Ruicun (RC) is a new ultra-small SPIONs agent that has been approved by China Food and Drug Administration for iron supplementation but not as a stem cell tracer in clinic. In this study, we demonstrated magnetic resonance imaging-based tracking of RC-labeled human umbilical cord derived mesenchymal stem cells (MSCs) transplanted to locally injured site of rat spinal cords. We then comprehensively evaluated the safety and quality of the RC-labeled MSCs under good manufacturing practicecompliant conditions, to investigate the feasibility of SPIONs for inner tracking in stem cell-based therapy (SCT). Our results showed that RC labeling at appropriate dose (200 µg/mL) did not have evident impacts on characteristics of MSCs in vitro, demonstrating safety, non-carcinogenesis, and non-tissue inflammation in vivo. The systematic assessments of intracellular biocompatibility indicated that the RC labeled MSCs met with mandatory requirements and standards for law-regulation systems regarding SCT, facilitating translation of cell-tracking technologies to clinical trials.

MagA expression attenuates iron export activity in undifferentiated multipotent P19 cells.

Magnetic resonance imaging (MRI) is a non-invasive imaging modality used in longitudinal cell tracking. Previous studies suggest that MagA, a putative iron transport protein from magnetotactic bacteria, is a useful gene-based magnetic resonance contrast agent. Hemagglutinin-tagged MagA was stably expressed in undifferentiated embryonic mouse teratocarcinoma, multipotent P19 cells to provide a suitable model for tracking these cells during differentiation. Western blot and immunocytochemistry confirmed the expression and membrane localization of MagA in P19 cells. Surprisingly, elemental iron analysis using inductively-coupled plasma mass spectrometry revealed significant iron uptake in both parental and MagA-expressing P19 cells, cultured in the presence of iron-supplemented medium. Withdrawal of this extracellular iron supplement revealed unexpected iron export activity in P19 cells, which MagA expression attenuated. The influence of iron supplementation on parental and MagA-expressing cells was not reflected by longitudinal relaxation rates. Measurement of transverse relaxation rates (R2* and R2) reflected changes in total cellular iron content but did not clearly distinguish MagA-expressing cells from the parental cell type, despite significant differences in the uptake and retention of total cellular iron. Unlike other cell types, the reversible component R2' (R2* ‒ R2) provided only a moderately strong correlation to amount of cellular iron, normalized to amount of protein. This is the first report to characterize MagA expression in a previously unrecognized iron exporting cell type. The interplay between contrast gene expression and systemic iron metabolism substantiates the potential for diverting cellular iron toward the formation of a novel iron compartment, however rudimentary when using a single magnetotactic bacterial gene expression system like magA. Since relatively few mammalian cells export iron, the P19 cell line provides a tractable model of ferroportin activity, suitable for magnetic resonance analysis of key iron-handling activities and their influence on gene-based MRI contrast.

Manganese oxide-carbon quantum dots nano-composites for fluorescence/magnetic resonance (T1) dual mode bioimaging, long term cell tracking, and ROS scavenging.

Multimodal long-term imaging probes with capability of extracting complementary information are highly important in biomedical engineering for disease diagnosis and monitoring of therapeutics distribution. However, most of the theranostics probes used are transient and have inherent problem of toxicity mostly related to generation of free radicals. In current study, a simple microwave assisted synthesis of multimodal imaging nanoprobe (T1 contrast in MR/fluorescence) is reported via doping carbon quantum dots into manganese oxide nanoparticles. The nanostructures were characterized by US-Vis spectroscopy, fluorescence spectroscopy, FTIR, Raman spectroscopy, TEM, XRD, AFM and XPS. The average particle size was observed to be around 20-40 nm with a height of 7-9 nm and approximate quantum yield of 0.23. The nanostructures were useful for bio imaging and cell tracking via fluorescence microscopy up to 12 generations with nominal cytotoxicity. The material was capable of scavenging free radicals from cellular microenvironment and downregulate gene expression of free radical scavenging enzymes. The material has significant relaxivity (r1) value of 3.98 mM-1.sec-1 at 1.5 T. It was also observed to create significant contrast with high circulation time (30 min) and renal clearance property. The histological analysis of kidney and liver sections were observed to have no significant toxicity from the nanostructure.

MR imaging tracking of inflammation-activatable engineered neutrophils for targeted therapy of surgically treated glioma.

Cell-based drug delivery systems have shown promising capability for tumor-targeted therapy owing to the intrinsic tumor-homing and drug-carrying property of some living cells. However, imaging tracking of their migration and bio-effects is urgently needed for clinical application, especially for glioma. Here, we report the inflammation-activatable engineered neutrophils by internalizing doxorubicin-loaded magnetic mesoporous silica nanoparticles (ND-MMSNs) which can provide the potential for magnetic resonance (MR) imaging tracking of the drug-loaded cells to actively target inflamed brain tumor after surgical resection of primary tumor. The phagocytized D-MMSNs possess high drug loading efficiency and do not affect the host neutrophils' viability, thus remarkably improving intratumoral drug concentration and delaying relapse of surgically treated glioma. Our study offers a new strategy in targeted cancer theranostics through combining the merits of living cells and nanoparticle carriers.

Single-Molecular Near-Infrared-II Theranostic Systems: Ultrastable Aggregation-Induced Emission Nanoparticles for Long-Term Tracing and Efficient Photothermal Therapy.

Second near-infrared (NIR-II, 1000-1700 nm) fluorescence bioimaging has attracted tremendous scientific interest and already been used in many biomedical studies. However, reports on organic NIR-II fluorescent probes for in vivo photoinduced imaging and simultaneous therapy, as well as the long-term tracing of specific biological objects, are still very rare. Herein we designed a single-molecular and NIR-II-emissive theranostic system by encapsulating a kind of aggregation-induced emission luminogen (AIEgen, named BPN-BBTD) with amphiphilic polymer. The ultra-stable BPN-BBTD nanoparticles were employed for the NIR-II fluorescence imaging and photothermal therapy of bladder tumors in vivo. The 785 nm excitation triggered photothermal therapy could completely eradicate the subcutaneous tumor and inhibit the growth of orthotopic tumors. Furthermore, BPN-BBTD nanoparticles were capable of monitoring subcutaneous and orthotopic tumors for a long time (32 days). Single-molecular and NIR-II-emitted aggregation-induced emission nanoparticles hold potential for the diagnosis, precise treatment, and metastasis monitoring of tumors in the future.

Tracking Cell Transplants in Femoral Osteonecrosis with Magnetic Resonance Imaging: A Proof-of-Concept Study in Patients.

PURPOSE: Osteonecrosis is a devastating complication of high-dose corticosteroid therapy in patients with cancer. Core decompression for prevention of bone collapse has been recently combined with the delivery of autologous concentrated bone marrow aspirates. The purpose of our study was to develop an imaging test for the detection of transplanted bone marrow cells in osteonecrosis lesions. EXPERIMENTAL DESIGN: In a prospective proof-of-concept clinical trial (NCT02893293), we performed serial MRI studies of nine hip joints of 7 patients with osteonecrosis before and after core decompression. Twenty-four to 48 hours prior to the surgery, we injected ferumoxytol nanoparticles intravenously to label cells in normal bone marrow with iron oxides. During the surgery, iron-labeled bone marrow cells were aspirated from the iliac crest, concentrated, and then injected into the decompression track. Following surgery, patients received follow-up MRI up to 6 months after bone marrow cell transplantation. RESULTS: Iron-labeled cells could be detected in the access canal by a dark (negative) signal on T2-weighted MR images. T2* relaxation times of iron-labeled cell transplants were significantly lower compared with unlabeled cell transplants of control patients who were not injected with ferumoxytol (P = 0.02). Clinical outcomes of patients who received ferumoxytol-labeled or unlabeled cell transplants were not significantly different (P = 1), suggesting that the added ferumoxytol administration did not negatively affect bone repair. CONCLUSIONS: This immediately clinically applicable imaging test could become a powerful new tool to monitor the effect of therapeutic cells on bone repair outcomes after corticosteroid-induced osteonecrosis.

Multimodal gadolinium oxysulfide nanoparticles: a versatile contrast agent for mesenchymal stem cell labeling.

Despite a clear development of innovative therapies based on stem cell manipulation, the availability of new tools to better understand and follow stem cell behavior and improve their biomedical applications is not adequate. Indeed, an ideal tracking device must have good ability to label stem cells as well as complete neutrality relative to their biology. Furthermore, preclinical studies imply in vitro and in vivo approaches that often require several kinds of labeling and/or detection procedures. Consequently, the multimodality concept presented in this work may present a solution to this problem as it has the potential to combine complementary imaging techniques. Spherical europium-doped gadolinium oxysulfide (Gd2O2S:Eu3+) nanoparticles are presented as a candidate as they are detectable by (1) magnetic resonance (MRI), (2) X-ray and (3) photoluminescence imaging. Whole body in vivo distribution, elimination and toxicity evaluation revealed a high tolerance of nanoparticles with a long-lasting MRI signal and slow hepatobiliary and renal clearance. In vitro labeling of a wide variety of cells unveils the nanoparticle potential for efficient and universal cell tracking. Emphasis on mesenchymal stromal cells (MSCs) leads to the definition of optimal conditions for labeling and tracking in the context of cell therapy: concentrations below 50 µg mL-1 and diameters between 170 and 300 nm. Viability, proliferation, migration and differentiation towards mesodermal lineages are preserved under these conditions, and cell labeling appears to be persistent and without any leakage. Ex vivo detection of as few as five thousand Gd2O2S:Eu3+-labeled MSCs by MRI combined with in vitro examination with fluorescence microscopy highlights the feasibility of cell tracking in cell therapy using this new nanoplatform.

The effect of hyperthermia on the DNA damage response induced by γ-rays, as determined through in situ cell tracking.

Hyperthermia (HT) acts as a cancer treatment by direct cell killing, radiosensitization, and promotion of tumor reoxygenation. The sensor proteins of the DNA damage response (DDR) are the direct targets of HT. However, the spatiotemporal properties of sensor proteins under HT are still unclear. Therefore, investigating the impact of HT on sensor proteins is of great importance. In the present study, the human fibrosarcoma cell line HT1080 stably transfected with 53BP1-GFP [the DDR protein 53BP1 fused to green fluorescent protein (GFP)] was used to investigate the real-time cellular response to DNA double-strand breaks (DSBs) induced by γ-rays. Using live-cell imaging combined with HT treatment, the spatiotemporal properties of the 53BP1 protein were directly monitored and quantitatively studied. We found that HT could delay and decrease the formation of 53BP1 ionizing radiation-induced foci (IRIF). Moreover, through the in situ tracking of individual IRIF, it was found that HT resulted in more unrepaired IRIF over the period of observation compared with IR alone. Additionally, the unrepaired IRIF had a larger area, higher intensity, and slower repair rate. Indeed, almost every cell treated with HT had unrepaired IRIF, and the majority of these IRIF increased in area individually, while the rest increased in area by the merging of adjacent IRIF. In summary, our study demonstrated that HT could perturb the primary event in the DDR induced by IR, and this may have important implications for cancer treatment and heat radiosensitization.

Multimodality reporter gene imaging: Construction strategies and application.

Molecular imaging has played an important role in the noninvasive exploration of multiple biological processes. Reporter gene imaging is a key part of molecular imaging. By combining with a reporter probe, a reporter protein can induce the accumulation of specific signals that are detectable by an imaging device to provide indirect information of reporter gene expression in living subjects. There are many types of reporter genes and each corresponding imaging technique has its own advantages and drawbacks. Fused reporter genes or single reporter genes with products detectable by multiple imaging modalities can compensate for the disadvantages and potentiate the advantages of each modality. Reporter gene multimodality imaging could be applied to trace implanted cells, monitor gene therapy, assess endogenous molecular events, screen drugs, etc. Although several types of multimodality imaging apparatus and multimodality reporter genes are available, more sophisticated detectors and multimodality reporter gene systems are needed.