Gadolinium‐containing magnetic resonance image contrast agent promotes fibrocyte differentiation

Gadolinium‐containing magnetic resonance imaging (MRI) contrast agents such as Omniscan are associated with nephrogenic systemic fibrosis (NSF). To determine if Omniscan can affect the differentiation of monocytes into fibroblast‐like cells called fibrocytes that are found in the fibrotic lesions of NSF, peripheral blood mononuclear cells (PBMCs) from NSF patients, hemodialysis patients without NSF, and healthy, renally sufficient controls were exposed to Omniscan in a standardized in vitro fibrocyte differentiation protocol. When added to PBMCs, the gadolinium‐containing MRI contrast agent Omniscan generally had little effect on fibrocyte differentiation. However, 10^?8 to 10^?3 mg/mL Omniscan reduced the ability of the fibrocyte differentiation inhibitor serum amyloid P (SAP) to decrease fibrocyte differentiation in PBMCs from 15 of 17 healthy controls and one of three NSF patients. Omniscan reduced the ability of SAP to decrease fibrocyte differentiation from purified monocytes, indicating that the Omniscan effect does not require the presence of other cells (such as T cells) in the PBMCs. Omniscan also reduced the ability of a different fibrocyte differentiation inhibitor, interleukin‐12, to decrease fibrocyte differentiation. These data suggest that Omniscan interferes with the regulatory action of signals that inhibit the differentiation of monocytes to fibrocytes. J. Magn. Reson. Imaging 2009;30:1284–1288. © 2009 Wiley‐Liss, Inc.     

Magnetically labeled cells can be detected by MR imaging

To determine the feasibility of MR imaging of magnetically labeled cells, different cell lines were labeled with monocrystalline iron oxide (MION) particles. Phantoms containing MION labeled cells were then assembled and imaged by MR at 1.5 T using T1-weighted and T2-weighted pulse sequences. MION uptake ranged from 8.5 × 10⁴ to 2.9 × 10⁵ particles/cell for tumor cells (9L and LX1, respectively) to 1.5 × 10⁶ to 4.8 × 10⁸ particles/cell for “professional phagocytes” (J774 and peritoneal macrophages, respectively). On the T1-weighted images, cell-internalized MION appeared hyperintense relative to agar and similar to MION in aqueous solution. On T2-weighted images, signal intensity varied according to concentration of MION within cells. Cell-internalized MION caused similar MR signal changes of cells as did free MION; however, at a dose that was an order of magnitude lower, depending on the pulse sequence used. The detectability of MION within cells was approximately 2 ng Fe, which corresponded to 10⁵ tumor cells/well or 5 × 10³ macrophages/well. We conclude that a variety of cells can be efficiently labeled with MION by simple incubation. Intracellular labeling may be used for MR imaging of in vivo cell tracking.     

Capacity of human monocytes to phagocytose approved iron oxide MR contrast agents in vitro

To evaluate the capacity of human monocytes to phagocytose various approved iron oxide based magnetic resonance (MR) contrast agents and to optimize in vitro labeling of these cells. Human monocytes were incubated with two superparamagnetic iron oxide particles (SPIO) as well as two ultrasmall SPIO (USPIO) at varying iron oxide concentrations and incubation times. Iron uptake in monocytes was proven by histology, quantified by atomic emission absorption spectrometry and depicted with T2* weighted fast field echo (FFE) MR images at 1.5 T. Additionally, induction of apoptosis in iron oxide labeled monocytes was determined by YO-PRO-1 staining. Cellular iron uptake was significantly (P<0.01) higher after incubation with SPIO compared with USPIO. For SPIO, the iron oxide uptake was significantly (P<0.01) higher after incubation with the ionic Ferucarbotran as compared with the non-ionic Ferumoxides. Efficient cell labeling was achieved after incubation with Ferucarbotran at concentrations 500 g Fe/ml and incubation times 1 h, resulting in a maximal iron oxide uptake of up to 50 pg Fe/cell without impairment of cell viability. In vitro labeling of human monocytes for MR imaging is most effectively obtained with the approved SPIO Ferucarbotran. Potential subsequent in vivo cell tracking applications comprise, e.g. specific targeting of inflammatory processes.     

In vivo tracking of genetically engineered, anti-HER2/neu directed natural killer cells to HER2/neu positive mammary tumors with magnetic resonance imaging

The purpose of this study is to optimize labeling of the human natural killer (NK) cell line NK-92 with iron-oxide-based contrast agents and to monitor the in vivo distribution of genetically engineered NK-92 cells, which are directed against HER2/neu receptors, to HER2/neu positive mammary tumors with magnetic resonance (MR) imaging. Parental NK-92 cells and genetically modified HER2/neu specific NK-92-scFv(FRP5)-zeta cells, expressing a chimeric antigen receptor specific to the tumor-associated ErbB2 (HER2/neu) antigen, were labeled with ferumoxides and ferucarbotran using simple incubation, lipofection and electroporation techniques. Labeling efficiency was evaluated by MR imaging, Prussian blue stains and spectrometry. Subsequently, ferucarbotran-labeled NK-92-scFv(FRP5)-zeta (n=3) or parental NK-92 cells were intravenously injected into the tail vein of six mice with HER2/neu-positive NIH 3T3 mammary tumors, implanted in the mammary fat pad. The accumulation of the cells in the tumors was monitored by MR imaging before and 12 and 24 h after cell injection (p.i.). MR data were correlated with histopathology. Both the parental NK-92 and the genetically modified NK-92-scFv(FRP5)-zeta cells could be labeled with ferucarbotran and ferumoxides by lipofection and electroporation, but not by simple incubation. The intracellular cytoplasmatic iron-oxide uptake was significantly higher after labeling with ferucarbotran than ferumoxides (P<0.05). After intravenous injection of 5×10⁶ NK-92-scFv(FRP5)-zeta cells into tumor-bearing mice, MR showed a progressive signal decline in HER2/neu-positive mammary tumors at 12 and 24 h (p.i.). Conversely, injection of 5×10⁶ parental NK-92 control cells, not directed against HER2/neu receptors, did not cause significant signal intensity changes of the tumors. Histopathology confirmed an accumulation of the former, but not the latter cells in tumor tissue. The human natural killer cell line NK-92 can be efficiently labeled with clinically applicable iron-oxide contrast agents, and the accumulation of these labeled cells in murine tumors can be monitored in vivo with MR imaging. This MR cell tracking technique may be applied to monitor NK-cell based immunotherapies in patients in order to assess the presence and extent of NK-cell tumor accumulations and, thus, to determine therapy response early and non-invasively.     

Comparison of SPIO and USPIO for in vitro labeling of human monocytes: MR detection and cell function

PURPOSE: To label human monocytes with superparamagnetic iron oxide (SPIO) and compare labeling efficiency with that of ultrasmall SPIO (USPIO) and evaluate the effect of iron incorporation on cell viability, migratory capacity, and proinflammatory cytokine production. MATERIALS AND METHODS: The study was approved by the institutional ethics committee; informed consent was obtained from donors. Freshly isolated human monocytes were labeled with iron particles of two sizes, USPIOs of 30 nm and SPIOs of 150 nm, for 1.5 hours in culture medium containing 0.1, 0.5, 1.0, and 3.7 mg of iron per milliliter. Labeling efficiency was determined with relaxation time magnetic resonance (MR) imaging (4.7 T) and Prussian blue staining for presence of intracellular iron. Cell viability was monitored; migratory capacity of monocytes after labeling was evaluated by using an in vitro assay with monolayers of brain endothelial cells. Levels of proinflammatory cytokines, interleukin (IL) 1 and IL-6, were measured with enzyme-linked immunosorbent assay 24 hours after labeling. Data were analyzed with Student t test or two-way analysis of variance followed by a multiple-comparison procedure. RESULTS: R2 relaxation rates increased for cell samples incubated with SPIOs, whereas rates were not affected for samples incubated with highest concentration of USPIOs. Labeling monocytes with SPIOs (1.0 mg Fe/mL) resulted in an R2 of 13.1 sec(-1) +/- 0.8 (standard error of the mean) (7 sec(-1) +/- 0.2 for vehicle-treated cells, P < .05) and had no effect on cell viability. On the basis of T2 relaxation times, the in vitro MR detection limit of 58 labeled monocytes per 0.05 microL was calculated. Migration of labeled monocytes was not different from that of vehicle-treated cells. Intracellular iron had no effect on production of IL-1 and IL-6 24 hours after labeling. CONCLUSION: In vitro labeling of human monocytes is effective by using SPIOs, not USPIOs. Incubation with SPIOs (1.0 mg Fe/mL) results in efficient labeling detectable on MR images and does not affect cellular viability and activation markers such as cell migration and cytokine production.     

Cell tracking with gadophrin-2: a bifunctional contrast agent for MR imaging,optical imaging,and fluorescence microscopy

The purpose of this study was to assess the feasibility of use of gadophrin-2 to trace intravenously injected human hematopoietic cells in athymic mice, employing magnetic resonance (MR) imaging, optical imaging (OI), and fluorescence microscopy. Mononuclear peripheral blood cells from GCSF-primed patients were labeled with gadophrin-2 (Schering AG, Berlin, Germany), a paramagnetic and fluorescent metalloporphyrin, using established transfection techniques with cationic liposomes. The labeled cells were evaluated in vitro with electron microscopy and inductively coupled plasma atomic emission spectrometry. Then, 1×10⁶–3×10⁸ labeled cells were injected into 14 nude Balb/c mice and the in vivo cell distribution was evaluated with MR imaging and OI before and 4, 24, and 48 h after intravenous injection (p.i.). Five additional mice served as controls: three mice were untreated controls and two mice were investigated after injection of unlabeled cells. The contrast agent effect was determined quantitatively for MR imaging by calculating signal-to-noise-ratio (SNR) data. After completion of in vivo imaging studies, fluorescence microscopy of excised organs was performed. Intracellular cytoplasmatic uptake of gadophrin-2 was confirmed by electron microscopy. Spectrometry determined an uptake of 31.56 nmol Gd per 10⁶ cells. After intravenous injection, the distribution of gadophrin-2 labeled cells in nude mice could be visualized by MR, OI, and fluorescence microscopy. At 4 h p.i., the transplanted cells mainly distributed to lung, liver, and spleen, and 24 h p.i. they also distributed to the bone marrow. Fluorescence microscopy confirmed the distribution of gadophrin-2 labeled cells to these target organs. Gadophrin-2 is suited as a bifunctional contrast agent for MR imaging, OI, and fluorescence microscopy and may be used to combine the advantages of each individual imaging modality for in vivo tracking of intravenously injected hematopoietic cells.     

Cell labeling with the positive MR contrast agent Gadofluorine M

The purpose of this study was to label human monocytes with Gadofluorine M by simple incubation for subsequent cell depiction at 1.5 and 3 T. Gadofluorine M displays a high r(1) relaxivity and is spontaneously phagocytosed by macrophages. Human monocytes were incubated with Gadofluorine M-Cy at varying concentrations and incubation times and underwent MR imaging at 1.5 and 3 T at increasing time intervals after the labeling procedure. R1-relaxation rates and r1 relaxivities of the labeled cells and non-labeled controls were determined. Cellular contrast agent uptake was examined by fluorescence microscopy and quantified by ICP-AES. Efficient cell labeling was achieved after incubation of the cells with 25 mM Gd Gadofluorine M for 12 h, resulting in a maximal uptake of 0.3 fmol Gd/cell without impairment of cell viability. Fluorescence microscopy confirmed internalization of the fluorescent contrast agent by monocytes. The r1 relaxivity of the labeled cells was 137 mM(-1)s(-1) at 1.5 T and 80.46 mM(-1)s(-1) at 3 T. Imaging studies showed stable labeling for at least 7 days. Human monocytes can be effectively labeled for MR imaging with Gadofluorine M. Potential in vivo cell-tracking applications include targeting of inflammatory processes with Gadofluorine-labeled leukocytes or monitoring of stem cell therapies for the treatment of arthritis.     

Comparison of iron oxide labeling properties of hematopoietic progenitor cells from umbilical cord blood and from peripheral blood for subsequent in vivo tracking in a xenotransplant mouse model XXX

RATIONALE AND OBJECTIVES: To compare and optimize ferumoxides labeling of human hematopoietic progenitor cells from umbilical cord blood and from peripheral blood for subsequent in vivo tracking with a clinical 1.5 T MR scanner. MATERIALS AND METHODS: Human hematopoietic progenitor cells, derived from umbilical cord blood or peripheral blood, were labeled with Ferumoxides by simple incubation or lipofection. Cellular iron uptake was quantified with spectrometry. Then, 3 x 10(7)-labeled cells were injected into the tail vein of 12 female nude Balb/c mice. The mice underwent magnetic resonance imaging before and 24 hours after injection. Precontrast and postcontrast signal intensities of liver, spleen, and bone marrow were measured and tested for significant differences with the t-test. Immunostains served as a histopathologic standard of reference. RESULTS: After labeling by simple incubation, only umbilical cord blood cells, but not peripheral blood cells, showed a significant iron uptake and could be tracked in vivo with magnetic resonance imaging. Using lipofection, both cell types could be tracked in vivo. A significant decline in signal intensity was observed in liver, spleen, and bone marrow at 24 hours after injection of efficiently labeled ferumoxides cells (P < .05). Histopathology proved the distribution of iron oxide-labeled cells to these organs. CONCLUSION: Hematopoietic progenitor cells from umbilical cord blood can be labeled by simple incubation with an Food and Drug Administration-approved magnetic resonance contrast agent with sufficient efficiency to provide an in vivo cell tracking at 1.5 T. Progenitor cells from peripheral blood need to be labeled with adjunctive transfection techniques to be depicted in vivo at 1.5 T.     

Non-invasive tracking of human haemopoietic CD34+ stem cells in vivo in immunodeficient mice by using magnetic resonance imaging

Objective

To assess migration of CD34⁺ human stem cells to the bone marrow of athymic mice by using magnetic resonance (MR) imaging and Resovist, a contrast agent containing superparamagnetic iron oxide (SPIO) particles.

Methods

All animal and human procedures were approved by our institution’s ethics committee, and women had given consent to donate umbilical cord blood (UCB). Balb/c-AnN Foxn1^nu/Crl mice received intravenous injection of 1?×?10⁶ (n?=?3), 5?×?10⁶ (n?=?3) or 1?×?10⁷ (n?=?3) human Resovist-labelled CD34⁺ cells; control mice received Resovist (n?=?3). MR imaging was performed before, 2 and 24 h after transplantation. Signal intensities of liver, muscle and bone marrow were measured and analysed by ANOVA and post hoc Student’s t tests. MR imaging data were verified by histological and immunological detection of both human cell surface markers and carboxydextran-coating of the contrast agent.

Results

CD34⁺ cells were efficiently labelled by Resovist without impairment of functionality. Twenty-four hours after administration of labelled cells, MR imaging revealed a significant signal decline in the bone marrow, and histological and immunological analyses confirmed the presence of transplanted human CD34⁺ cells.

Conclusion

Intravenously administered Resovist-labelled CD34⁺ cells home to bone marrow of mice. Homing can be tracked in vivo by using clinical 1.5-T MR imaging technology.     

四物汤对模式生物斑马鱼血液系统与辐射损伤的影响

目的 使用斑马鱼观察中药复方四物汤对辐射损伤血液系统的干预作用,明确斑马鱼是否可应用于中药对血液系统调控的研究。方法 72只体重在0.14~0.20 g的4月龄成年雄性斑马鱼（Danio rerio）用于全部实验,首先取36只斑马鱼用于照射后血液发育动力学的变化观察,另外36只斑马鱼用于四物汤对照射后血液系统的干预作用研究。采用⁶⁰Co γ射线照射,辐射剂量20 Gy,吸收剂量率97.33 cGy/min。在照射后血液发育动力学观察中,9只未照射作为0 d对照,余27只斑马鱼分别于照射后第7、14和30天麻醉,收集外周血细胞和肾髓中细胞,采用流式细胞仪分析细胞的绝对数量。依据照射后外周血和肾髓中细胞的动态变化情况判断血液发育动力学特征,藉此实施四物汤的药效观察。四物汤对照射损伤干预实验周期7 d,36只斑马鱼采用随机数表法分为未照射组、单纯照射组、药物2 000组和药物5 000组,每组9只。两个药物组的斑马鱼按上述条件20 Gy照射后第2天分别置于稀释了2 000倍和5 000倍的四物汤水中饲养,第7天收集各组斑马鱼的外周血和肾髓中细胞,比较判断四物汤对斑马鱼辐射损伤血液系统的干预作用。结果 照射后斑马鱼血液发育动态变化明显,血液系统消融作用在第7天最明显,与未照射比较,斑马鱼的外周血细胞和肾髓总细胞数量分别下降26%和52%,差异均有统计学意义（t=4.535,28.987,P<0.05）,肾髓中髓系单核细胞、淋巴细胞和红细胞数分别下降46%、79%和33%,差异均有统计学意义（t=18.457、66.900、9.872,P<0.05）,前体细胞下降49%,但差异无统计学意义（P>0.05）。照射后第14天肾髓中各种细胞数均呈现上升,第30天恢复至照射前水平以上。斑马鱼照射后第2天开始连续6 d给予四物汤,药物5 000组与单纯照射组比较,肾髓细胞总数、髓系单核细胞、前体细胞和红细胞分别增加了57%、125%、81%和35%,差异均有统计学意义（t=12.128、21.594、15.473、4.594,P<0.05）,淋巴细胞增加了59%,而外周血红细胞数量两组比较差异无统计学意义（P>0.05）;药物2 000组各参数均与单纯照射组比较差异无统计学意义（P>0.05）。结论 照射后斑马鱼血液系统发育呈现明显的先抑后扬的动态变化,一定浓度的四物汤对斑马鱼造血系统照射损伤有明显的干预作用,可为中药血液系统调控方面的研究提供参考。     

19F MRI detection of acute allograft rejection with in vivo perfluorocarbon labeling of immune cells

Current diagnosis of organ rejection following transplantation relies on tissue biopsy, which is not ideal due to sampling limitations and risks associated with the invasive procedure.We have previously shown that cellular magnetic resonance imaging (MRI) of iron‐oxide labeled immune‐cell infiltration can provide a noninvasive measure of rejection status by detecting areas of hypointensity on T‐weighted images. In this study, we tested the feasibility of using a fluorine‐based cellular tracer agent to detect macrophage accumulation in rodent models of acute allograft rejection by fluorine‐19 (¹⁹F) MRI and magnetic resonance spectroscopy. This study used two rat models of acute rejection, including abdominal heterotopic cardiac transplant and orthotopic kidney transplant models. Following in vivo labeling of monocytes and macrophages with a commercially available agent containing perfluoro‐15‐crown‐5‐ether, we observed ¹⁹F‐signal intensity in the organs experiencing rejection by ¹⁹F MRI, and conventional ¹H MRI was used for anatomical context. Immunofluorescense and histology confirmed macrophage labeling. These results are consistent with our previous studies and show the complementary nature of the two cellular imaging techniques. With no background signal, ¹⁹F MRI/magnetic resonance spectroscopy can provide unambiguous detection of fluorine labeled cells, and may be a useful technique for detecting and quantifying rejection grade in patients. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Magnetic nanoparticles for imaging dendritic cells

We report the development of superparamagnetic iron oxide (SPIOs) nanoparticles and investigate the migration of SPIO‐labeled dendritic cells (DCs) in a syngeneic mouse model using magnetic resonance (MR) imaging. The size of the dextran‐coated SPIO is roughly 30 nm, and the DCs are capable of independent uptake of these particles, although not at levels comparable to particle uptake in the presence of a transfecting reagent. On average, with the assistance of polylysine, the particles were efficiently delivered inside DCs within one hour of incubation. The SPIO particles occupy approximately 0.35% of cell surface and are equivalent to 34.6 pg of iron per cell. In vivo imaging demonstrated that the labeled cells migrated from the injection site in the footpad to the corresponding popliteal lymph node. The homing of labeled cells in the lymph nodes resulted in a signal drop of up to 79%. Furthermore, labeling DCs with SPIO particles did not compromise cell function, we demonstrated that SPIO‐enhanced MR imaging can be used to track the migration of DCs effectively in vivo. Magn Reson Med 63:1383–1390, 2010. © 2010 Wiley‐Liss, Inc.     

Dextran-magnetite particles: contrast-enhanced MRI of blood-brain barrier disruption in a rat model.

Dextran-magnetite particles (DMP) were studied for their use as a MR contrast agent to visualize lesions with a blood-brain barrier (bbb) disruption. A freezing injury to the rat cerebral cortex was used as a model of bbb disruption. The biodistribution of iv-injected DMP was studied using atomic absorption spectrophotometry, electron microscopy, and MRI. One hour after injection, focal accumulation of the particles in capillary endothelial cells could be demonstrated in the freezing lesion. Despite the observation that the relaxivity of DMP in vivo appears to be less well pronounced than that in vitro, the MR imaging studies show that DMP can be used to visualize bbb disruption with adequate contrast.     

Intracellular labeling of T-cells with superparamagnetic contrast agents

Isolated rat T-cells have been labeled intracellularly, using endocytosis uptake of two superparamagnetic contrast agents, AquaMagl00 and BMS180549, which are both iron-oxide particles coated with dextran. No deterioration of cell proliferation response to mitogen stimulation was observed alter labeling with either superparamagnetic contrast agent. AquaMag100 particles show aggregation and co-precipitation in culture media for T-cells. BMS180549 particles not only produce no observable aggregation or co-precipitation, but also have a higher efficiency for labeling T-cells than AquaPlag100. The efficiency of cell labeling was determined by measuring the decrease in the spin-spin relaxation time of the water proton in cell samples containing 1 × 10⁷ labeled T-cells/milliliter of 2% w/w gelatin. After optimization of the labeling procedures, a shortening of the spin-spin relaxation time by a factor of approximately 7 to 10 has been demonstrated. Under the present experimental conditions, the up-regulation of low density lipoprotein receptor does not increase the labeling efficiency by endocytosis. Our results suggest that intracellular labeling of specific cell types can be achieved with good efficiency and the labeled cells can be detected by magnetic resonance imaging in rat testicles in vivo.     

<Superscript>18</Superscript>F-FDG PET/CT findings of sinonasal inverted papilloma with or without coexistent malignancy: comparison with MR imaging findings in eight patients

Introduction  Sinonasal inverted papilloma (IP) is known for high rate of associated malignancy. The purpose of this study was to identify ¹⁸F-FDG PET/CT findings of sinonasal IPs. We also tried to compare the PET/CT findings with the MR imaging findings. Methods  We retrospectively reviewed PET/CT and MR images of eight patients with sinonasal IP with (n = 6) or without (n = 2) coexistent squamous cell carcinoma (SCC). Particular attention was paid to correlate the PET/CT findings with the MR imaging findings in terms of area distribution of standard uptake values (SUVs) and a convoluted cerebriform pattern (CCP). Results  In two benign IPs, the maximum SUVs measured 8.2 and 7.8, respectively (mean, 8.0). In both tumors, MR images demonstrated a diffuse CCP. In six IPs with coexistent SCC, the maximum SUVs ranged from 13.3 to 31.9 (mean ± SD, 20.2 ± 6.6). In these tumors, MR images demonstrated a diffuse CCP in two, a partial CCP in three, and no CCP in one. A wide discrepancy was noted between MR imaging and PET/CT in terms of area distribution of a CCP and SUVs. Conclusion  In sinonasal lesions with MR imaging features of IP, ¹⁸F-FDG PET/CT demonstrating avid FDG uptake does not necessarily imply the presence of coexistent malignancy. In our small series, although IPs containing foci of SCC had consistently higher SUVs than IPs without SCC, the limited literature on this subject suggests that PET cannot be used reliably to make the distinction.     

Hemophilic pseudotumor: spectrum of MR findings

 Objective. To determine the MR imaging appearance of hemophilic pseudotumor (HP) and its clinical implications. Design and patients. Five hemophilic patients (aged 35–77 years) with 12 HPs in various anatomic locations were included in this study. The MR images were retrospectively evaluated for the appearance of the lesions and accompanying abnormalities, as well as their clinical implications. Results and conclusion. MR images of all five patients (12 lesions) showed well-defined masses containing blood clots in various stages of organization surrounded by a fibrous capsule in subcutaneous fat or in intramuscular, interfascial, subperiosteal, and intraosseous locations. Intramuscular HP frequently had mural nodules. This is an almost unique appearance that is somewhat unexpected. MR imaging allowed determination of number, size, and extent of the lesions, evidence of neurovascular involvement, and accompanying musculoskeletal alterations. It is concluded that MR imaging not only is a sensitive and accurate method for detecting and diagnosing HP and providing useful information for therapeutic decision making, but can also be used to assess results of treatment by allowing evaluation of the evolution of blood products, the size of lesions in regions difficult to access by physical examination, and recurrent bleeding within a chronic lesion.     

Efficient in vitro labeling rabbit neural stem cell with paramagnetic Gd-DTPA and fluorescent substance

Objectives

The aim of this study is to label rabbit neural stem cells (NSCs) by using standard contrast agents (Gd-DTPA) in combination with PKH26 and in vitro track them with MR imaging.

Materials and methods

NSCs from prenatal brains of rabbits were cultured and propagated. Intracellular uptake of Gd-DTPA was achieved by using a non-liposomal lipid transfection reagent (Effectene) as the transfection agent. After labeling with Gd-DTPA, cells were incubated with cellular membrane fluorescent dye PKH26. The labeling effectiveness and the longevity of Gd-DTPA maintenance were measured on a 1.5 T MR scanner. The influence of labeling on the cellular biological behaviors was assessed by cellular viability, proliferation and differentiation assessment.

Results

The labeling efficiency of Gd-DTPA was up to 90%. The signal intensity on T1-weighted imaging and T1 values of labeled cells were significantly higher than those of unlabeled cells (P < 0.05). The minimal number of detectable cells for T1-weighted imaging was 5 × 10³. Cellular uptake of Gd-DTPA was maintained until 15 days after initially labeling. There was no significant difference in the cellular viability and proliferation between the labeled and unlabeled NSCs (P > 0.05). Normal glial and neuronal differentiation remained in labeled NSCs like unlabeled NSCs.

Conclusion

Highly efficient labeling NSCs with Gd-DTPA could be achieved by using Effectene. This method of labeling NSCs allows for tracking cells with MR imaging, and without alterations of cellular biological behaviors.     

Instant MR labeling of stem cells using magnetoelectroporation.

For cellular MR imaging, conventional approaches to intracellular magnetic labeling of nonphagocytic cells rely on the use of secondary compounds such as transfection agents and prolonged incubation of cells. Magnetoelectroporation (MEP) was investigated as an alternative method to achieve instant (<1 s) endosomal labeling with the FDA-approved formulation Feridex, without the need for adjunct agents or initiating cell cultures. While MEP was harmful at higher voltages or pulse durations, the procedure could be properly calibrated using a pulse of 130 V and 17 ms. Labeling was demonstrated for stem cells from mice, rats, and humans; the uptake of iron was in the picogram range and comparable to values obtained using transfection agents. MEP-labeled stem cells exhibited an unaltered viability, proliferation, and mitochondrial metabolic rate. Labeled mesenchymal stem cells (MSCs) and neural stem cells (NSCs) differentiated into adipogenic, osteogenic, and neural lineages in an identical fashion as unlabeled cells, while containing Feridex particles as demonstrated by double immunofluorescent staining. MEP-labeled NSCs proliferated normally following intrastriatal transplantation and could be readily detected by MR imaging in vivo. As MEP circumvents the use of secondary agents, obviating the need for clinical approval, MEP labeling may be ideally suitable for bedside implementation.     

The effects of 2.35-T MR imaging on natural killer cell cytotoxicity with and without interleukin-2

The effects of magnetic resonance (MR) imaging on the natural killer (NK) cell cytotoxicity of human peripheral blood mononuclear cells (PBMC) were studied. The possibility that prior exposure of PBMC to MR imaging might alter the effectiveness of interleukin-2 (IL-2) in enhancing NK cell cytotoxicity was also investigated. PBMC from 10 healthy subjects were used as effector cells, and target cells were three different types of cancer cells: K-562, OV-2774, and Clone-A. MR imaging exposure of effector cells was performed in a 2.35-T static magnetic field for 50 minutes. The chromium-51-release assay was used to determine NK cell cytotoxicity. NK cell cytotoxicity was greater against K-562 target cells than against Clone-A target cells, but in neither case was cytotoxicity affected by prior exposure of PBMC to MR imaging. Treatment of PBMC with IL-2 for 2-6 days enhanced NK cell cytotoxicity, and this enhancement was not altered by prior MR imaging exposure of PBMC.     

Quantification of tissue plasma volume in the rat by contrast-enhanced magnetic resonance imaging

Magnetic resonance imaging enhanced with a macromolecular contrast medium (MMCM), albumin-Gd-DTPA, was used to estimate the plasma volume in vivo in the myocardium, lung, liver, and skeletal muscle of 10 normal rats. The plasma volumes of the same tissues in a parallel group of six rats were estimated in vitro by a conventional radioisotopic technique (¹¹¹In-transferrin). Plasma volumes of myocardium, lung, liver, and skeletal muscle estimated by the MR technique (μl plas. ia cc-¹ of tissue) were 101,109,163, and 11.0, respectively, while plasma volumes measured by the In-transferrin radioisotope technique (mg plasma g-¹ of tissue) were 78.6, 215,143, and 11-2, respectively. Assuming a ratio of densities of aerated lung to blood of 0.45 and of other tissues to blood of 1.0, correlation between the methods was excellent (R² = 0.99) indicating that MR imaging enhanced with MMCM permits reliable in vivo estimation of tissue plasma volume in the rat.