The poor prognosis of patients with aggressive and invasive cancers combined with toxic effects and short half-life of currently available treatments necessitate development of more effective tumor selective therapies. Mesenchymal stem cells (MSCs) are emerging as novel cell-based delivery agents; however, a thorough investigation addressing their therapeutic potential and fate in different cancer models is lacking. In this study, we explored the engineering potential, fate, and therapeutic efficacy of human MSCs in a highly malignant and invasive model of glioblastoma. We show that engineered MSC retain their ''stem-like'' properties, survive longer in mice with gliomas than in the normal brain, and migrate extensively toward gliomas. We also show that MSCs are resistant to the cytokine tumor necrosis factor apoptosis ligand (TRAIL) and, when engineered to express secreted recombinant TRAIL, induce caspase-mediated apoptosis in established glioma cell lines as well as CD133-positive primary glioma cells in vitro. Using highly malignant and invasive human glioma models and employing real-time imaging with correlative neuropathology, we demonstrate that MSC-delivered recombinant TRAIL has profound anti-tumor effects in vivo. This study demonstrates the efficacy of diagnostic and therapeutic MSC in preclinical glioma models and forms the basis for developing stem cell-based therapies for different cancers.gliomas ͉ in vivo imaging ͉ TRAIL

Radioluminescence microscopy is a new method for imaging radionuclide uptake by single live cells with a fluorescence microscope. Here, we report a particle-counting scheme that improves spatial resolution by overcoming the b-range limit. Methods: Short frames (10 ms21 s) were acquired using a high-gain camera coupled to a microscope to capture individual ionization tracks. Optical reconstruction of the b-ionization track (ORBIT) was performed to localize individual b decays, which were aggregated into a composite image. The new approach was evaluated by imaging the uptake of 18 F-FDG in nonconfluent breast cancer cells. Results: After image reconstruction, ORBIT resulted in better definition of individual cells. This effect was particularly noticeable in small clusters (2-4 cells), which occur naturally even for nonconfluent cell cultures. The annihilation and Bremsstrahlung photon background signal was markedly lower. Single-cell measurements of 18 F-FDG uptake that were computed from ORBIT images more closely matched the uptake of the fluorescent glucose analog (Pearson correlation coefficient, 0.54 vs. 0.44, respectively). Conclusion: ORBIT can image the uptake of a radiotracer in living cells with spatial resolution better than the b range. In principle, ORBIT may also allow for greater quantitative accuracy because the decay rate is measured more directly, with no dependency on the b-particle energy.Key Words: radionuclide imaging instrumentation; single-cell analysis; microscopy; autoradiography Nucl Med 2013; 54:1841 54: -1846 54: DOI: 10.2967 Aut oradiography is a well-established method for high-resolution imaging of radionuclide probes in tissues. Film and emulsion methods have the highest spatial resolution but poor sensitivity, dynamic range, and quantitative accuracy and require tedious sample preparation (1,2). Other autoradiography methods (e.g., storage phosphor (3), solid-state detection (4,5), gaseous detectors (6), and thin phosphor (7)) have higher sensitivity and dynamic range but spatial resolution worse than 50 mm. Only a few methods have demonstrated the ability to visualize the uptake of radionuclide probes with single-cell resolution. One of these methods uses a bsensitive avalanche photodiode to measure radionuclide uptake in small groups of cells, cultured in 16 microfluidic chambers (8). An experiment showed that the avalanche photodiode could measure signal from a single cell in the chamber. Another device, the MicroImager, achieved 15-mm spatial resolution for 35 S, which was used to detect in situ hybridization in single neurons (9). A third device, the radioluminescence microscope, was developed to visualize radionuclide uptake in live cells during fluorescence microscopy (10). Radioluminescence microscopy can be used to measure fluorescent and radionuclide signals emanating from a collection of living cells, in a relatively short time. Here we propose a new particlecounting scheme for radioluminescence microscopy with higher spatial resolution and, in principle, quantitative ...

The primary aim of this study was to assess the potential of in vivo photoacoustic tomography for direct functional measurement of ovarian tumor response to antiangiogenic therapy. Methods In vivo studies were performed with institutional animal care and use committee approval. We used an orthotopic mouse model of ovarian cancer treated with trebananib (n = 9) or vehicle (n = 9). Tumor-bearing mice were randomized into trebananib or vehicle groups at day 10 and dosed on days 12, 15, and 18 after implantation. Photoacoustic tomography and blood draws were performed at day 10 and then 24 h after each drug dose. Tumors were excised for histopathology after the final studies on day 19. Data analysis to test for statistical significance was performed blinded. Results Blockade of angiopoietin signaling using trebananib resulted in reduced total hemoglobin–weighted photoacoustic signal (n = 9, P = 0.01) and increased oxyhemoglobin-weighted photoacoustic signal (n = 9, P < 0.01). The latter observation indicated normalization of the residual tumor vessels, which was also implied by low levels of angiopoietin 1 in serum biomarker profiling (0.76 ± 0.12 ng/mL). These noninvasive measures reflected a 30% reduction in micro-vessel density and increased vessel maturation in ex vivo sections. Conclusion Photoacoustic tomography is able to evaluate both vessel regression and normalization in response to trebananib. Non-invasive imaging data were supported by modulation of serum markers in vitro and ex vivo histopathology.

One of the major challenges in regenerative medicine is the ability to recreate the stem cell niche, which is defined by its signaling molecules, the creation of cytokine gradients, and the modulation of matrix stiffness. A wide range of scaffolds has been developed in order to recapitulate the stem cell niche, among them hydrogels. This paper reports the development of a new silk-alginate based hydrogel with a focus on stem cell culture. This biocomposite allows to fine tune its elasticity during cell culture, addressing the importance of mechanotransduction during stem cell differentiation. The silk-alginate scaffold promotes adherence of mouse embryonic stem cells and cell survival upon transplantation. In addition, it has tunable stiffness as function of the silk-alginte ratio and the concentration of crosslinker - a characteristic that is very hard to accomplish in current hydrogels. The hydrogel and the presented results represents key steps on the way of creating artificial stem cell niche, opening up new paths in regenerative medicine.