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Non-invasive imaging reveals conditions that impact distribution and persistence of cells after in vivo administration
摘要： Background: Cell-based regenerative medicine therapies are now frequently tested in clinical trials. In many conditions, cell therapies are administered systemically, but there is little understanding of their fate, and adverse events are often under-reported. Currently, it is only possible to assess safety and fate of cell therapies in preclinical studies, specifically by monitoring animals longitudinally using multi-modal imaging approaches. Here, using a suite of in vivo imaging modalities to explore the fate of a range of human and murine cells, we investigate how route of administration, cell type and host immune status affect the fate of administered cells. Methods: We applied a unique imaging platform combining bioluminescence, optoacoustic and magnetic resonance imaging modalities to assess the safety of different human and murine cell types by following their biodistribution and persistence in mice following administration into the venous or arterial system. Results: Longitudinal imaging analyses (i) suggested that the intra-arterial route may be more hazardous than intravenous administration for certain cell types, (ii) revealed that the potential of a mouse mesenchymal stem/stromal cell (MSC) line to form tumours depended on administration route and mouse strain and (iii) indicated that clinically tested human umbilical cord (hUC)-derived MSCs can transiently and unexpectedly proliferate when administered intravenously to mice. Conclusions: In order to perform an adequate safety assessment of potential cell-based therapies, a thorough understanding of cell biodistribution and fate post administration is required. The non-invasive imaging platform used here can expose not only the general organ distribution of these therapies, but also a detailed view of their presence within different organs and, importantly, tumourigenic potential. Our observation that the hUC-MSCs but not the human bone marrow (hBM)-derived MSCs persisted for a period in some animals suggests that therapies with these cells should proceed with caution.
关键词： Safety,Mesenchymal stem/stromal cells,Preclinical models,Multi-modal imaging,Cell therapies,Cell tracking
更新于2025-09-11 14:15:04
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Influence of the crosstalk on the intensity of HAADF-STEM images of quaternary semiconductor materials
摘要： The influence of the neighbouring atomic-columns in determining the composition at atomic column scale of quaternary semiconductor compounds, using simulated HAADF-STEM images is evaluated. The InAlAsSb alloy, a promising material in the photovoltaic field, is considered. We find that the so called ‘crosstalk’ effect plays an important role for the aimed compositional determination. The intensity transfer is larger from neighbouring atomic columns with higher average Z, and towards atomic columns with smaller Z. Our results show that in order to obtain precise information on the column composition, the HAADF-STEM intensities of both columns need to be taken into account simultaneously.
关键词： Crosstalk effect,InAlAsSb,HAADF-STEM
更新于2025-09-10 09:29:36
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Differentiation of human olfactory mucosa mesenchymal stem cells into photoreceptor cells in vitro
摘要： ● AIM: To investigate whether the human olfactory mucosa mesenchymal stem cells (OM-MSCs) can differentiate into photoreceptor cells in vitro. ● METHODS: Through the olfactory mucosa adherent method, olfactory mucosa was isolated, cultured and identified in vitro among mesenchymal stem cells. The cell surface markers were analyzed by flow cytometry, induced to differentiate into retinal photoreceptor cells in vitro, and the expression of rhodopsin was observed and identified by Immunofluorescence and Western blot methods. ● RESULTS: OM-MSCs from human were spindle cell-based, and showing radial colony arrangement. OM-MSCs were negative for CD34, CD45 and CD105, but positive for CD73 and CD90. Following induction, a strong positive reaction was produced by photoreceptor specific marker rhodopsin in the cells. ● CONSLUSION: This novel finding demonstrates that OM-MSCs can be cultured and expanded in vitro. They possess biological characteristics of mesenchymal stem cells, and have the ability to be induced into retinal cells.
关键词： mesenchymal stem cells,differentiation,human olfactory mucosa,retinal cells
更新于2025-09-10 09:29:36
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The MTF & DQE of Annular Dark Field STEM: Implications for Low-dose Imaging and Compressed Sensing
摘要： Annular dark-field imaging in the scanning transmission electron microscope (ADF-STEM) is a hugely useful incoherent imaging mode, yielding monotonically increasing mass / thickness contrast facilitating quantitative compositional mapping, atom-counting, structure-solving and even unstained biological-imaging. With increasing interest in beam-sensitive materials, many people would like to perform ultra-low-dose imaging or compressed-sensing (CS). Unfortunately, some CS implementations require complex blankers/mask/shutters and may require expensive instrument modification; fast-scanning on the other hand should in principle be available to everyone. Nearly all installed ADF detectors follow the same basic design comprising; a scintillator, light-pipe, PMT, amplifier and a digitiser outputting in arbitrary uncalibrated units. While the scintillator material itself may have an afterglow of only some tens of nanoseconds, the combined assembly has a decay constant of the order of 1.7-3μs which becomes significant in some cases. Scanning with dwell-times faster than this decay introduces issues such as increased background and loss of contrast, streaking in real-space and a diffuse noise band in Fourier-space. In spite of these problems, previous literature has shown that PMT based detectors are in fact sensitive to even single electron signals, unfortunately they are also highly inhomogeneous in their collection efficiency. One solution to this is to as whether we can form an image using these signals using a pulse read-out? Such an image would record the arriving electron as a single impact-event rather than a streak (perfect MTF), the results would be digital rather than analogue, and all electrons would be recorded with equal sensitivity (perfect DQE). The integer nature of the resulting image signal would also directly benefit quantitative contrast (fractional-beam) studies, statistical image analysis, and compressed-sensing / image-inpainting. In this presentation, we will present a new tool to generate realistic noise realisations from ADF image-simulations. This tool registers each electron of a finite dose passing through the sample, to the detector (incorporating afterglow), and onward to amplifiers with realistic thermal and electronic noise. This tool is verified against previous experimental observations of the behaviour of fast-scanned images, and is used to explore the modulation transfer function (MTF) of ADF-STEM for various dwell-times. We then propose, and demonstrate using both simulations and experiment, a new method for operating an ADF detector in a pulse read-out mode (which we call ADFpro) using dwell-times of 0.5μs and 0.2μs. The detector’s quantum efficiency is evaluated indirectly through the evaluation of image pixel-value histograms but also directly using ADF-detector sensitivity maps. The limitations of this approach will be presented, as well as the implications for ultra-low-dose imaging and for compressed-sensing / image-inpainting using such fully digital data.
关键词： ADF-STEM,MTF,DQE,compressed sensing,low-dose imaging
更新于2025-09-10 09:29:36
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Otx2 enhances transdifferentiation of Müller cells-derived retinal stem cells into photoreceptor-like cells
摘要： Retinal Müller glial cells have the potential of neurogenic retinal progenitor cells, and could reprogram into retinal‐specific cell types such as photoreceptor cells. How to promote the differentiation of Müller cells into photoreceptor cells represents a promising therapy strategy for retinal degeneration diseases. This study aimed to enhance the transdifferentiation of rat Müller cells‐derived retinal stem cells (MC‐RSCs) into photoreceptor‐like cells and explore the signalling mechanism. We dedifferentiated rat Müller cells into MC‐RSCs which were infected with Otx2 overexpression lentivirus or control. The positive rate of photoreceptor‐like cells among MC‐RSCs treated with Otx2 overexpression lentivirus was significantly higher compared to control. Furthermore, pre‐treatment with Crx siRNA, Nrl siRNA, or GSK‐3 inhibitor SB‐216763 reduced the positive rate of photoreceptor‐like cells among MC‐RSCs treated with Otx2 overexpression lentivirus. Finally, Otx2 induced photoreceptor precursor cells were injected into subretinal space of N‐methyl‐N‐nitrosourea induced rat model of retinal degeneration and partially recovered retinal degeneration in the rats. In conclusion, Otx2 enhances transdifferentiation of MC‐RSCs into photoreceptor‐like cells and this is associated with the inhibition of Wnt signalling. Otx2 is a potential target for gene therapy of retinal degenerative diseases.
关键词： Müller cells,photoreceptor cells,stem cells,Wnt signalling,Otx2
更新于2025-09-10 09:29:36
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Two-Photon Polymerization as a Tool for Studying 3D Printed Topography-Induced Stem Cell Fate
摘要： Geometric topographies are known to influence cellular differentiation toward specific phenotypes, but to date the range of features and type of substrates that can be easily fabricated to study these interactions is somewhat limited. In this study, an emerging technology, two-photon polymerization, is used to print topological patterns with varying feature-size and thereby study their effect on cellular differentiation. This technique offers rapid manufacturing of topographical surfaces with good feature resolution for shapes smaller than 3 μm. Human-induced pluripotent stem cells, when attached to these substrates or a non-patterned control for 1 week, express an array of genetic markers that suggest their differentiation toward a heterogeneous population of multipotent progenitors from all three germ layers. Compared to the topographically smooth control, small features (1.6 μm) encourage differentiation toward ectoderm while large features (8 μm) inhibit self-renewal. This study demonstrates the potential of using two-photon polymerization to study and control stem cell fate as a function of substrate interactions. The ability to tailor and strategically design biomaterials in this way can enable more precise and efficient generation or maintenance of desired phenotypes in vitro and in vivo.
关键词： induced pluripotent stem cells,differentiation,substrate topography,3D printing,two-photon polymerization
更新于2025-09-10 09:29:36
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European Microscopy Congress 2016: Proceedings || Exciton and Plasmon Mapping at the Nanoscale
摘要： Excitons and plasmonic interactions, which are effectively responsible for the transfer of energy within devices such as solar cells, LEDs and semiconductor circuits, have been understood in theory for decades. However, the photophysical behaviour within materials has always been rather difficult to understand and be directly observed. Surface structure, localised thickness variations and presence of edges are bound to influence the macroscopic properties of the materials. Understanding the local surface structure and chemistry of these materials at the nanoscale is crucial in order to reach the full potential of the materials for real-life applications. Hence, there is a need to fully characterise the physical and chemical properties from the bottom up i.e. at the level of individual atoms and to map the optoelectronic properties where they happen. Due to recent technical improvements we can now access parts of the low loss electron energy-loss (LL EEL) spectra which had previously been inaccessible. This opens up new possibilities to study nanomaterials not only at unprecedented energy but also – contrary to bulk optical techniques – with a spatial resolution at the nanoscale, as described by Zhou, Dellby [1]. Although some significant progress has been made recently in unravelling the physical origins of the LL EEL features as shown by Tizei, Lin [2], significant gaps in our understanding of the signals and their origins remain. In the study presented here, we used for the first time a combination of experimental monochromated LL STEM EEL spectroscopy and theoretical calculations using time-dependent density functional theory (TDDFT) as well as the Bethe-Salpeter equation (BSE) to study the optical properties of MoS2 at the nanoscale with the aim to understand the origins of the peaks and regional variations of the complete LL EEL spectrum. We report that we identified and resolved as well as mapped mid-bandgap excitonic signals at ~1.88eV and at ~2.08eV on MoS2 flakes using monochromated LL EELS (figure 1) and confirmed their origin by BSE calculations; we also identified and mapped several plasmonic peaks (figure 1) using LL EELS combined with TD DFT. Furthermore, we observed great spatial variations in the LL EELS signal when comparing the edge to inner regions of a flake, i.e. with increasing number of layers, and we show how these can be largely attributed to beam geometry effects. The effects of the experimental set-up on the low loss EELS signal will be discussed.
关键词： STEM,2D materials,MoS2,TEM,spectroscopy,Low loss EELS
更新于2025-09-10 09:29:36
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Adipogenic differentiation of murine bone marrow mesenchymal stem cells induced by visible light via photo- induced biomodulation
摘要： Background: Bone marrow mesenchymal stem cells (BM-MSCs) are undifferentiated cells that can proliferate and differentiate into specialized cells for tissue self-repair. Low-level laser (LLL) can induce biomodulatory effects such as cellular proliferation, differentiation, and migration. We investigated the biomodulatory effects of the photoactive compound chloroaluminum phthalocyanine nanoemulsion (AlClPc/NE) on the adipogenic differentiation of BM-MSCs, when combined with LLL (AlClPc/NE-LLL). Methods: The BM-MSCs used in this work were isolated from green fluorescent protein-positive (GFP+) C57BL6 mice. Cells were first treated with AlClPc/NE, a well-designed photoactive nano-drug and were then subjected to in vitro expansion, morphological and immunophenotypic characterization, and cellular cytotoxicity analysis. Subsequently, BM-MSCs were induced to differentiate into adipocytes by photo-induced biomodulation with AlClPc/NE-LLL. Results: Our results showed that the isolated cell population was consistent with murine BM-MSCs. The cellular cytotoxicity analysis revealed that the optimal nanoemulsion dose to induce BM-MSC biomodulation was 5.0 μmol/L. Twenty-four hours following treatment with AlClPc/NE, BM-MSC were subjected to visible light irradiation of 20 mJ/cm2 at 670 nm. Six days after photo-induced biomodulation, cells maintained high GFP expression level, and expressed detectable mRNA levels of adipogenic genes (lipoprotein lipase and PPARγ); formation of lipid vacuoles was observed, and the cells did not show any tumorigenic potential in vivo. Conclusions: Our results indicated that photo-induced biomodulation via visible light using AlClPc/NE and LLL can induce adipogenic differentiation of murine BM-MSCs. Therefore, cell therapy with BM-MSCs and photo-induced biomodulation may contribute to the development of new therapeutic strategies that are faster and more effective than traditional methods to trigger MSC differentiation.
关键词： photo induced biomodulation,adipogenic differentiation,chloroaluminum phthalocyanine (AlClPc),low level laser (LLL),Bone marrow-mesenchymal stem cells (BM-MSC)
更新于2025-09-10 09:29:36
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The 3D imaging of mesenchymal stem cells on porous scaffolds using high-contrasted x-ray computed nanotomography
摘要： This study presents an X-ray computed nanotomography (nano-CT) based, high-resolution imaging technique. Thanks to a voxel resolution of 540 nm, this novel technique is suitable for observing the 3D morphology of soft biopolymeric scaffolds seeded with stem cells. A sample of highly porous collagen scaffold seeded with contrasted mesenchymal stem cells (MSC) was investigated by using lab-based nano-CT. The whole volume of the sample was analysed without its destruction. To evaluate the potential of nano-CT, a comparison measurement was done using a standard microscopy technique. Scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) established an extension and local accumulation of the contrasting agent – heavy metallic osmium tetroxide. The presented imaging technique is novel as it will help to understand better the behaviour of cells while interacting with three-dimensional biomaterials. This is crucial for both experimental and clinical tissue engineering applications in order to limit the risk of uncontrolled cell growth, and potentially tumour formation.
关键词： SEM/EDX,X-ray computed nanotomography,mesenchymal stem cells,tissue engineering,Biopolymeric scaffold
更新于2025-09-10 09:29:36
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Indocyanine Green labeling for optical and photoacoustic imaging of Mesenchymal Stem Cells after in vivo transplantation
摘要： The transplantation of Mesenchymal Stem Cells (MSCs) holds great promise for the treatment of a plethora of human diseases, but new non-invasive procedures are needed to monitor the cell fate in vivo. Already largely used in medical diagnostics, the fluorescent dye Indocyanine Green (ICG) is an established dye to track limited numbers of cells by optical imaging, but it can be visualized also by Photoacoustic Imaging (PAI), which provides a higher spatial resolution than pure near infrared fluorescence imaging (NIRF). Because of its successful use in clinical and preclinical examinations, we chose ICG as PAI cell labeling agent. Optimal incubation conditions were defined for an efficient and clinically translatable MSC labeling protocol, such that no cytotoxicity or alterations of the phenotypic profile were observed, and a consistent intracellular uptake of the molecule was achieved. Suspensions of ICG-labeled cells were both optically and optoacoustically detected in vitro, revealing a certain variability in the photoacoustic spectra acquired by varying the excitation wavelength from 680 to 970 nm. Intramuscular engraftments of ICG-labeled MSCs were clearly visualized by both PAI and NIRF over few days after transplantation in the hindlimb of healthy mice, suggesting that the proposed technique retains a considerable potential in the field of transplantation-focused research and therapy.
关键词： Indocyanine Green,Near Infrared Fluorescence Imaging,Photoacoustic Imaging,Cell tracking,Stem Cells
更新于2025-09-10 09:29:36