ABSTRACT
BACKGROUND: Various cell therapy products have been approved by clinical trials worldwide, and cell therapies such as stem cell therapy and adoptive immunotherapy have attracted much attention. Real-time observation and imaging in vivo can visualize the distribution of cells, track cell movement, monitor cell viability, and observe the cell migration and growth. Many imaging technologies can visualize cells in vivo, such as ultrasound, optics, MRI and nuclear imaging, and these methods need to correspond to different labeling and detection strategies. Each strategy has its own advantages and disadvantages. OBJECTIVE: To review the principle and development of different tracking methods, and their application in animals and humans. METHODS: PubMed, Google Scholar, Web of Science and CNKI databases were searched with the keywords of “cell tracking, in vivo cell tracking, PET imaging, MRI, optical imaging.” The articles published in the past 5-10 years were preferred. The contents of the articles mainly describe the principle of different tracking methods, and their application in animal models and patients. RESULTS AND CONCLUSION: In the past 20 years, cell tracking has developed into a multifarious discipline, not only establishing a variety of robust methods in animal models, but also proving the feasibility of clinical transformation in some human studies. The development of the non-invasive detection methods, such as PET and MRI, and new contrast agents provides strong support for the application of cell therapy in clinical and scientific researches.
ABSTRACT
PURPOSE: To determine the optimal combination of commercially available superparamagnetic iron oxide (SPIO) nanoparticles with transfection agents (TA). MATERIALS AND METHODS: Protamine sulfate (Pro) and poly-L-lysin (PLL) were incubated with ferumoxide and ferucarbotran in human mesenchymal stem cells at various concentrations, and cellular viability were evaluated. Cellular iron uptake was qualitatively and quantitatively evaluated. Cell visibility was assessed via MR imaging and the T2-relaxation time was calculated. RESULTS: The cellular viabilities with ferucarbotran were more significantly decreased than those with ferumoxide (p < 0.05). Iron uptake with ferumoxide was significantly higher than that for those with with ferucarbotran. The T2-relaxation time was observed to be shorter with ferumoxide in comparison to those with ferucarbotran (p < 0.05). Ferumoxide at a concentration of 25 microg/ml in combination with either Pro or PLL at a concentration of 3.0 microg/ml did not adversely impact cell viability, maximized iron uptake, and exhibited a lower T2-relaxation time in comparison to other combinations. CONCLUSION: Stem cells with ferumoxide exhibited a higher cellular viability and iron uptake in comparison to ferucarbotran- treated stem cells. A 25 microg/ml of ferumoxide with a 3.0 microg/ml of TA is sufficient to label mesenchymal stem cells.
Subject(s)
Humans , Cell Survival , Contrast Media , Dextrans , Ferric Compounds , Iron , Magnetite Nanoparticles , Mesenchymal Stem Cells , Nanoparticles , Protamines , Stem Cells , TransfectionABSTRACT
Neural stem cells were labeled with superparamagnetic iron oxide (SPIO) and tracked by MRI in vitro and in vivo after implantation. Rat neural stem cells were labeled with SPIO combined with PLL by the means of receptor-mediated endocytosis. Prussian blue staining and electron microscopy were conducted to identify the iron particles in these neural stem cells. SPIO-labeled cells were tracked by 4.7T MRI in vivo and in vitro after implantation. The subjects were divided into 5 groups, including 5× 105 labeled cells cultured for one day after labeling, 5 × 105 same phase unlabeled cells, cell culture medium with 25 μg Fe/mL SPIO, cell culture medium without SPIO and distilled water. MRI scanning sequences included T1WI, T2WI and T2*WI. R2 and R2* of labeled cells were calculated. The results showed: (1) Neural stem cells could be labeled with SPIO and labeling efficiency was 100%. Prussian blue staining showed numerous blue-stained iron particles in the cytoplasm; (2) The average percentage change of signal intensity of labeled cells on T1WI in 4.7T MRI was 24.06%, T2WI 50.66% and T2*WI 53.70% respectively; (3) T2 of labeled cells and unlabeled cells in 4.7T MRI was 516 ms and 77 ms respectively, R2 was 1.94 s-1 and 12.98 s-1 respectively, and T2* was 109 ms and 22.9 ms, R2* was 9.17 s-1 and 43.67 s-1 respectively; (4) Remarkable low signal area on T2WI and T2*WI could exist for nearly 7 weeks and then disappeared gradually in the left brain transplanted with labeled cells, however no signal change in the right brain implanted with unlabeled cells. It was concluded that neural stem cells could be labeled effectively with SPIO. R2 and R2* of labeled cells were increased obviously. MRI can be used to track labeled cells in vitro and in vivo.
ABSTRACT
Cationic colloidal gold (CCG) nanoparticles were used for labeling on the anioinic sites of living cells under two-photon fluorescence (TPF) microscope,and for delivering macromolecules into the target cells when irradiated by focused femtosecond laser pulses. 15 nm CCG nanoparticles which were made by conjugation with poly-L-Lysine,were attached on the anionic sites,especially on the membrane,of CHO-K1 cells because of their strong positive charge at physiological pH. Target cells labeled with cationic gold nanoparticles were imaged under TPF microscope,and lifetime images of the same targets were taken by time correlated single photon counting (TCSPC) technique in order to verify the fluorescence of the marker and the luminescence of the gold particles. The results shown that CCG nanoparticles first accumulated on the negatively charged sites of the membrane,then entered via endocytic pathway and attached anionic sites in plasma. A macromolecular 10 ku fluorescein isothiocyanate dextran (FITC-D) was added into the sample and the focused femtosecond laser of TPL microscope was employed to scan the target cells layer by layer. Typical laser power level used in biological imaging is about 3～5 mW. Here the laser power of scanning was below 5 mW in order to prevent photochemical damage of the fs-pulses alone and to localize effects to the nanoparticles on a nano-scale. After scanning the target cells under stack mode,macromolecular fluoresceins surrounding the cells was observed to cross the membrane and to diffuse in the cytoplasma. Comparing with the images before scanning,the two-photon fluorescence and fluorescence lifetime images revealed the delivery of FITC-D into target cells. Photothermal effects,which may be responsible for the permeabilisation,are highly localized in nanoscale and are not expected to cause damage exceeding the cell membrane. After extensive of laser scanning also cell death occurred. The ratio of the uptake of FITC-D and cellular death under different conditions were measured by flow cytometer. The results shown: with the increased scanning times or ratio of particles to cells,transfer efficiency increased first and decreased afterwards,but the ratio of cellular death went up all along.