Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Recent advances in human islet transplantation are hampered by significant graft loss shortly after transplantation and inability to follow islet fate directly. Both issues were addressed by utilizing a dual-purpose therapy/imaging small interfering RNA (siRNA)-nanoparticle probe targeting apoptotic-related gene caspase-3. We expect that treatment with the probe would result in significantly better survival of transplanted islets, which could be monitored by in vivo magnetic resonance imaging (MRI).
We synthesized a probe consisting of therapeutic (siRNA to human caspase-3) and imaging (magnetic iron oxide nanoparticles, MN) moieties. In vitro testing of the probe included serum starvation of the islets followed by treatment with the probe. Caspase-3 gene silencing and protein expression were determined by RT-PCR and Western blot, respectively. In vivo studies included serial MRI of NOD-SCID mice transplanted with MN-small interfering (si)Caspase-3-labeled human islets under the left kidney capsule and MN-treated islets under the right kidney capsule.
Treatment with MN-siCaspase-3 probe resulted in decrease of mRNA and protein expression in serum-starved islets compared with controls. In vivo MRI showed that there were significant differences in the relative volume change between MN-siCaspase-3-treated grafts and MN-labeled grafts. Histology revealed decreased caspase-3 expression and cell apoptosis in MN-siCaspase-3-treated grafts compared with the control side.
Our data show the feasibility of combining siRNA therapy and in vivo monitoring of transplanted islets in mice. We observed a protective effect of MN-siCaspase-3 in treated islets both in vitro and in vivo. This study could potentially aid in increasing the success of clinical islet transplantation.
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"Furthermore, these particles have average size of 10–100 nm and they are being used in clinical applications. Biodegradable nature of them makes these particles adaptable for applications related with cancer (Wang et al. 2011a, b; Yang et al. 2011; Gaihre et al. 2011; Taratula et al. 2011). Magnetic carriers are given their magnetic responsiveness to a magnetic field by incorporating materials such as magnetite, iron, nickel, cobalt, neodymium– iron–boron, or samarium–cobalt (Hafeli 2004). "
[Show abstract][Hide abstract]ABSTRACT: Herein, we investigated the biological uptake, distribution, and radiopharmaceutical potential of a novel molecule based on 2-hydroxyethyl methacrylate (HEMA) and anilinephtalein (APH) in the metabolism of Albino Wistar rats. In order to achieve this, we synthesized APH using organic synthesis methods and copolymerized APH with HEMA using a common polymerization method, surfactant-free emulsion polymerization. In the presence of Fe3O4 particles, we obtained a new generation magnetic-nano-scale polymer, magnetic-poly(HEMA–APH). This new molecule was chemically identified and approved by several characterization methods using Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, electron spin resonance, atomic force microscope, and Zeta particle-size analysis. To evaluate the biological activity in live metabolism and anti-cancer potential of mag-poly(HEMA–APH), molecule was radioiodinated by a widely used labeling technique, iodogen method, with a gamma diffuser radionuclide, 131I. Thin-layer radiochromatography experiments demonstrated that 131I binded to nanopolymer with the labeling yield of 90 %. Lipophilicity and stability experiments were conducted to determine the condition of cold and labeled mag-poly(HEMA–APH) in rat blood and lipid medium. Results demonstrated that radioiodinated molecule stayed as an intact complex in rat metabolism for 24 h and experimental lipophilicity was determined as 0.12 ± 0.02. In vivo results obtained by imaging and biological distribution experiments indicated that mag-poly(HEMA–APH) labeled with 131I [131I-mag-poly(HEMA–APH)] highly incorporated into tissues of the uterus, the ovarian, the prostate, and the lungs in rat metabolism. Based on these results, it may be evaluated that novel mag-poly(HEMA–APH) molecule labeled with 131I is a compound which has a significant potential for being used as an anti-cancer agent. Certain results can only be obtained whether this molecule is applied to adenocarcinoma cell models and tumor-bearing animals.
Full-text · Article · Oct 2013 · Journal of Nanoparticle Research
"The synthesized probe consisted of magnetic dextran-coated iron oxide MNs labeled with Cy5.5 near-infrared optical dye and conjugated to siRNA at the dextran surface. First, we synthesized Cy5.5-labeled MNs, as previously reported (27). Briefly, a solution of monoactivated Cy5.5 succinimide ester (Amersham Biosciences, Piscataway, NJ) in 20 mmol/L sodium citrate and 0.15 mol/L NaCl was reacted with previously dialyzed immunopure, aminoderivatized dextran-coated iron oxide (pH 8.5) with constant agitation for 12 h at room temperature. "
[Show abstract][Hide abstract]ABSTRACT: Islet transplantation has recently emerged as an acceptable clinical modality for restoring normoglycemia in patients with type 1 diabetes mellitus (T1DM). The long-term survival and function of islet grafts is compromised by immune rejection-related factors. Downregulation of factors that mediate immune rejection using RNA interference holds promise for improving islet graft resistance to damaging factors after transplantation. Here, we used a dual-purpose therapy/imaging small interfering (si)RNA magnetic nanoparticle (MN) probe that targets β-2 microglobulin (B2M), a key component of the major histocompatibility class I complex (MHC I). In addition to serving as a siRNA carrier, this MN-siB2M probe enables monitoring of graft persistence noninvasively using magnetic resonance imaging (MRI). Human islets labeled with these MNs before transplantation into B2M (null) NOD/scid mice showed significantly improved preservation of graft volume starting at 2 weeks, as determined by longitudinal MRI in an adoptive transfer model (P < 0.05). Furthermore, animals transplanted with MN-siB2M-labeled islets demonstrated a significant delay of up to 23.8 ± 4.8 days in diabetes onset after the adoptive transfer of T cells relative to 6.5 ± 4.5 days in controls. This study demonstrated that our approach could protect pancreatic islet grafts from immune rejection and could potentially be applied to allotransplantation and prevention of the autoimmune recurrence of T1DM in islet transplantation or endogenous islets.
"A more recent study by our group used a dual-purpose therapy/imaging nanoparticle probe to target the apoptotic-related gene caspase-3. We demonstrated that our “two-in-one” MN-siCaspase-3 imaging probe could silence the apoptotic-related gene, providing significant protection to the grafts from early loss after transplantation, and at the same time served as an MRI label to assess the in vivo post-transplant fate of the grafts noninvasively (Figure 3) [24, 91]. The results of our study are in line with those of another recently published study showing that the use of fluorinated alginate microcapsules increased the insulin secretion rate of human islets and at the same time allowed detection by MRI and CT imaging . "
[Show abstract][Hide abstract]ABSTRACT: Replacement of insulin production by pancreatic islet transplantation has great potential as a therapy for type 1 diabetes mellitus. At present, the lack of an effective approach to islet grafts assessment limits the success of this treatment. The development of molecular imaging techniques has the potential to fulfill the goal of real-time noninvasive monitoring of the functional status and viability of the islet grafts. We review the application of a variety of imaging modalities for detecting endogenous and transplanted beta-cell mass. The review also explores the various molecular imaging strategies for assessing islet delivery, the metabolic effects on the islet grafts as well as detection of immunorejection. Here, we highlight the use of combined imaging and therapeutic interventions in islet transplantation and the in vivo monitoring of stem cells differentiation into insulin-producing cells.
Full-text · Article · Oct 2011 · Journal of Transplantation