Focused magnetic stem cell targeting to the retina using superparamagnetic iron oxide nanoparticles

Improving Stem Cell Delivery to the Trabecular Meshwork Using Magnetic Nanoparticles

Glaucoma is a major cause of blindness and is frequently associated with elevated intraocular pressure. The trabecular meshwork (TM), the tissue that primarily regulates intraocular pressure, is known to have reduced cellularity in glaucoma. Thus, stem cells, if properly delivered to the TM, may offer a novel therapeutic option for intraocular pressure control in glaucoma patients. For this purpose, targeted delivery of stem cells to the TM is desired. Here, we used magnetic nanoparticles (Prussian blue nanocubes [PBNCs]) to label mesenchymal stem cells and to magnetically steer them to the TM following injection into the eye's anterior chamber. PBNC-labeled stem cells showed increased delivery to the TM vs. unlabeled cells after only 15-minute exposure to a magnetic field. Further, PBNC-labeled mesenchymal stem cells could be delivered to the entire circumference of the TM, which was not possible without magnetic steering. PBNCs did not affect mesenchymal stem cell viability or multipotency. We conclude that this labeling approach allows for targeted, relatively high-efficiency delivery of stem cells to the TM in clinically translatable time-scales, which are necessary steps towards regenerative medicine therapies for control of ocular hypertension in glaucoma patients.

Improving the Subcutaneous Mouse Tumor Model by Effective Manipulation of Magnetic Nanoparticles-Treated Implanted Cancer Cells

Murine tumor models have played a fundamental role in the development of novel therapeutic interventions and are currently widely used in translational research. Specifically, strategies that aim at reducing inter-animal variability of tumor size in transplantable mouse tumor models are of particular importance. In our approach, we used magnetic nanoparticles to label and manipulate colon cancer cells for the improvement of the standard syngeneic subcutaneous mouse tumor model. Following subcutaneous injection on the scruff of the neck, magnetically-tagged implanted cancer cells were manipulated by applying an external magnetic field towards localized tumor formation. Our data provide evidence that this approach can facilitate the formation of localized tumors of similar shape, reducing thereby the tumor size's variability. For validating the proof-of-principle, a low-dose of 5-FU was administered in small animal groups as a representative anticancer therapy. Under these experimental conditions, the 5-FU-induced tumor growth inhibition was statistically significant only after the implementation of the proposed method. The presented approach is a promising strategy for studying accurately therapeutic interventions in subcutaneous experimental solid tumor models allowing for the detection of statistically significant differences between smaller experimental groups.

Protocol for MicroRNA Transfer into Adult Bone Marrow-derived Hematopoietic Stem Cells to Enable Cell Engineering Combined with Magnetic Targeting

While CD133⁺ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates after injection into injured tissues as well as the observed massive cell death rates lead to very restricted therapeutic effects. To overcome these limitations, we sought to establish a non-viral based protocol for suitable cell engineering prior to their administration. The modification of human CD133⁺ expressing SCs using microRNA (miR) loaded magnetic polyplexes was addressed with respect to uptake efficiency and safety as well as the targeting potential of the cells. Relying on our protocol, we can achieve high miR uptake rates of 80-90% while the CD133⁺ stem cell properties remain unaffected. Moreover, these modified cells offer the option of magnetic targeting. We describe here a safe and highly efficient procedure for the modification of CD133⁺ SCs. We expect this approach to provide a standard technology for optimization of therapeutic stem cell effects and for monitoring of the administered cell product via magnetic resonance imaging (MRI).

Ex vivo evaluation of intravitreal mesenchymal stromal cell viability using bioluminescence imaging

Background

Bone marrow-derived mesenchymal stromal cell (MSC) therapy is a promising treatment for several degenerative ocular diseases; however, no reproducible method of monitoring these cells into the eye has been established. The aim of this study was to describe successful bioluminescence imaging (BLI) to detect viable luciferase-expressing MSC in the eye.

Methods

Human donor MSC in culture were transduced with 50 μl luciferase lentiviral vector (three viral particles/cell) prior to intraocular injection. Twenty-one right eyes of 21 rabbits were evaluated through BLI after receiving 1 × 10⁶ luciferase-expressing MSC intravitreally. Contralateral eyes were injected with vehicle (phosphate-buffered saline (PBS)) and were used as controls. At seven different time points (1 h to 60 days), d-luciferin (40 mg/ml, 300 μl PBS) was injected in subsets of six enucleated eyes for evaluation of radiance decay through BLI analysis. CD90 and CD73 immunofluorescence was studied in selected eyes.

Results

Eyes injected with MSC showed high BLI radiance immediately after d-luciferin injection and progressive decay until 60 days. Mean BLI radiance measures from eyes with luciferase-expressing MSC were significantly higher than controls from 8 h to 30 days. At the thirtieth day, positive CD90- and CD73-expressing cells were observed only in the vitreous cavity of eyes injected with MSC.

Conclusions

Viable MSC were identified in the vitreous cavity 1 month after a single injection. Our results confirmed BLI as a useful and reliable method to detect MSC injected into the eye globe.

Design of Magnetically Labeled Cells (Mag-Cells) for in Vivo Control of Stem Cell Migration and Differentiation

Cell-based therapies are attractive for treating various degenerative disorders and cancer but delivering functional cells to the region of interest in vivo remains difficult. The problem is exacerbated in dense biological matrices such as solid tissues because these environments impose significant steric hindrances for cell movement. Here, we show that neural stem cells transfected with zinc-doped ferrite magnetic nanoparticles (ZnMNPs) can be pulled by an external magnet to migrate to the desired location in the brain. These magnetically labeled cells (Mag-Cells) can migrate because ZnMNPs generate sufficiently strong mechanical forces to overcome steric hindrances in the brain tissues. Once at the site of lesion, Mag-Cells show enhanced neuronal differentiation and greater secretion of neurotrophic factors than unlabeled control stem cells. Our study shows that ZnMNPs activate zinc-mediated Wnt signaling to facilitate neuronal differentiation. When implemented in a rodent brain stroke model, Mag-Cells led to significant recovery of locomotor performance in the impaired limbs of the animals. Our findings provide a simple magnetic method for controlling migration of stem cells with high therapeutic functions, offering a valuable tool for other cell-based therapies.

Phenotypic characterization of P23H and S334ter rhodopsin transgenic rat models of inherited retinal degeneration

We produced 8 lines of transgenic (Tg) rats expressing one of two different rhodopsin mutations in albino Sprague-Dawley (SD) rats. Three lines were generated with a proline to histidine substitution at codon 23 (P23H), the most common autosomal dominant form of retinitis pigmentosa in the United States. Five lines were generated with a termination codon at position 334 (S334ter), resulting in a C-terminal truncated opsin protein lacking the last 15 amino acid residues and containing all of the phosphorylation sites involved in rhodopsin deactivation, as well as the terminal QVAPA residues important for rhodopsin deactivation and trafficking. The rates of photoreceptor (PR) degeneration in these models vary in proportion to the ratio of mutant to wild-type rhodopsin. The models have been widely studied, but many aspects of their phenotypes have not been described. Here we present a comprehensive study of the 8 Tg lines, including the time course of PR degeneration from the onset to one year of age, retinal structure by light and electron microscopy (EM), hemispheric asymmetry and gradients of rod and cone degeneration, rhodopsin content, gene dosage effect, rapid activation and invasion of the outer retina by presumptive microglia, rod outer segment disc shedding and phagocytosis by the retinal pigmented epithelium (RPE), and retinal function by the electroretinogram (ERG). The biphasic nature of PR cell death was noted, as was the lack of an injury-induced protective response in the rat models. EM analysis revealed the accumulation of submicron vesicular structures in the interphotoreceptor space during the peak period of PR outer segment degeneration in the S334ter lines. This is likely due to the elimination of the trafficking consensus domain as seen before as with other rhodopsin mutants lacking the C-terminal QVAPA. The 8 rhodopsin Tg lines have been, and will continue to be, extremely useful models for the experimental study of inherited retinal degenerations.

Hematite iron oxide nanoparticles: apoptosis of myoblast cancer cells and their arithmetical assessment

Hematite (α-Fe₂O₃) forms iron oxide nanoparticles (NPs) which are thermally stable and have various electrochemical and optochemical applications. Due to their wide applicability, the present work was designed to form the hematite phase of iron oxide (αFe₂O₃NPs) NPs prepared via a solution process. Their cytological performance was checked with C2C12 cells. The crystalline property of the NPs was examined with X-ray diffraction patterns (XRD) and it was found that the size of the particles formed ranged from 12 to 15 nm. Structural information was also identified via field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), which again confirmed that the size of each NP is about 12–15 nm. Surface topographical analysis was done via atomic force microscopy (AFM), which reveals that the size of the distance between two particles is in the range of 12 ± 3 nm. The C2C12 cells were cultured in a humidified environment with 5% CO₂ and were checked via a microscope. The αFe₂O₃NPs were used for cytotoxic evaluation against C2C12 cells. A MTT (3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was utilized to check the viability of cells in a dose-dependent (100 ng mL⁻¹, 500 ng mL⁻¹ or 1000 ng mL⁻¹) manner. The morphology of the cells under the influence of αFe₂O₃NPs for live and dead cells in a wet environment was confirmed via confocal laser scanning microscopy (CLSM). The apoptosis caused due to the αFe₂O₃NPs was evaluated in presence of caspases 3/7 with GAPDH genes, which confirmed the upregulation that is responsible in caspase 3/7 genes, with treatment of C2C12 at low (500 ng mL⁻¹) and high (1000 ng mL⁻¹) doses of αFe₂O₃NPs. Analytical studies were also performed to authenticate the obtained data for αFe₂O₃NPs using parameters such as precision, accuracy, linearity, limits of detection (LOD) and limit of quantitation (LOQ), quantitative recoveries and relative standard deviation (RSD). The analyses play a significant role in investigating the large effect of αFe₂O₃NPs on C2C12 cells.

Hematite (α-Fe₂O₃) forms iron oxide nanoparticles (NPs) which are thermally stable and have various electrochemical and optochemical applications.

Assessment of Safety and Functional Efficacy of Stem Cell-Based Therapeutic Approaches Using Retinal Degenerative Animal Models

Dysfunction and death of retinal pigment epithelium (RPE) and or photoreceptors can lead to irreversible vision loss. The eye represents an ideal microenvironment for stem cell-based therapy. It is considered an “immune privileged” site, and the number of cells needed for therapy is relatively low for the area of focused vision (macula). Further, surgical placement of stem cell-derived grafts (RPE, retinal progenitors, and photoreceptor precursors) into the vitreous cavity or subretinal space has been well established. For preclinical tests, assessments of stem cell-derived graft survival and functionality are conducted in animal models by various noninvasive approaches and imaging modalities. In vivo experiments conducted in animal models based on replacing photoreceptors and/or RPE cells have shown survival and functionality of the transplanted cells, rescue of the host retina, and improvement of visual function. Based on the positive results obtained from these animal experiments, human clinical trials are being initiated. Despite such progress in stem cell research, ethical, regulatory, safety, and technical difficulties still remain a challenge for the transformation of this technique into a standard clinical approach. In this review, the current status of preclinical safety and efficacy studies for retinal cell replacement therapies conducted in animal models will be discussed.

Magnetic targeting as a strategy to enhance therapeutic effects of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have been extensively investigated in the field of regenerative medicine. It is known that the success of MSC-based therapies depends primarily on effective cell delivery to the target site where they will secrete vesicles and soluble factors with immunomodulatory and potentially reparative properties. However, some lesions are located in sites that are difficult to access, such as the heart, spinal cord, and joints. Additionally, low MSC retention at target sites makes cell therapy short-lasting and, therefore, less effective. In this context, the magnetic targeting technique has emerged as a new strategy to aid delivery, increase retention, and enhance the effects of MSCs. This approach uses magnetic nanoparticles to magnetize MSCs and static magnetic fields to guide them in vivo, thus promoting more focused, effective, and lasting retention of MSCs at the target site. In the present review, we discuss the magnetic targeting technique, its principles, and the materials most commonly used; we also discuss its potential for MSC enhancement, and safety concerns that should be addressed before it can be applied in clinical practice.

Systemic administration of mesenchymal stem cells combined with parathyroid hormone therapy synergistically regenerates multiple rib fractures

Background

A devastating condition that leads to trauma-related morbidity, multiple rib fractures, remain a serious unmet clinical need. Systemic administration of mesenchymal stem cells (MSCs) has been shown to regenerate various tissues. We hypothesized that parathyroid hormone (PTH) therapy would enhance MSC homing and differentiation, ultimately leading to bone formation that would bridge rib fractures.

Methods

The combination of human MSCs (hMSCs) and a clinically relevant PTH dose was studied using immunosuppressed rats. Segmental defects were created in animals’ fifth and sixth ribs. The rats were divided into four groups: a negative control group, in which animals received vehicle alone; the PTH-only group, in which animals received daily subcutaneous injections of 4 μg/kg teriparatide, a pharmaceutical derivative of PTH; the hMSC-only group, in which each animal received five injections of 2 × 10⁶ hMSCs; and the hMSC + PTH group, in which animals received both treatments. Longitudinal in vivo monitoring of bone formation was performed biweekly using micro-computed tomography (μCT), followed by histological analysis.

Results

Fluorescently-dyed hMSCs were counted using confocal microscopy imaging of histological samples harvested 8 weeks after surgery. PTH significantly augmented the number of hMSCs that homed to the fracture site. Immunofluorescence of osteogenic markers, osteocalcin and bone sialoprotein, showed that PTH induced cell differentiation in both exogenously administered cells and resident cells. μCT scans revealed a significant increase in bone volume only in the hMSC + PTH group, beginning by the 4^th week after surgery. Eight weeks after surgery, 35% of ribs in the hMSC + PTH group had complete bone bridging, whereas there was complete bridging in only 6.25% of ribs (one rib) in the PTH-only group and in none of the ribs in the other groups. Based on the μCT scans, biomechanical analysis using the micro-finite element method demonstrated that the healed ribs were stiffer than intact ribs in torsion, compression, and bending simulations, as expected when examining bone callus composed of woven bone.

Conclusions

Administration of both hMSCs and PTH worked synergistically in rib fracture healing, suggesting this approach may pave the way to treat multiple rib fractures as well as additional fractures in various anatomical sites.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0502-9) contains supplementary material, which is available to authorized users.

Magnet-Bead Based MicroRNA Delivery System to Modify CD133+ Stem Cells

Aim. CD133⁺ stem cells bear huge potential for regenerative medicine. However, low retention in the injured tissue and massive cell death reduce beneficial effects. In order to address these issues, we intended to develop a nonviral system for appropriate cell engineering. Materials and Methods. Modification of human CD133⁺ stem cells with magnetic polyplexes carrying microRNA was studied in terms of efficiency, safety, and targeting potential. Results. High microRNA uptake rates (~80-90%) were achieved without affecting CD133⁺ stem cell properties. Modified cells can be magnetically guided. Conclusion. We developed a safe and efficient protocol for CD133⁺ stem cell modification. Our work may become a basis to improve stem cell therapeutical effects as well as their monitoring with magnetic resonance imaging.

Magnetic Resonance Imaging of Human-Derived Amniotic Membrane Stem Cells Using PEGylated Superparamagnetic Iron Oxide Nanoparticles

OBJECTIVE

The label and detection of cells injected into target tissues is an area of focus for researchers. Iron oxide nanoparticles can be used to label cells as they have special characteristics. The purpose of this study is to examine the effects of iron oxide nanoparticles on human-derived amniotic membrane stem cell (hAMCs) survival and to investigate the magnetic properties of these nanoparticles with increased contrast in magnetic resonance imaging (MRI).

MATERIALS AND METHODS

In this experimental study, we initially isolated mesenchymal stem cells from amniotic membranes and analyzed them by flow cytometry. In addition, we synthesized superparamagnetic iron oxide nanoparticles (SPIONs) and characterized them by various methods. The SPIONs were incubated with hAMCs at concentrations of 25-800 μg/mL. The cytotoxicity of nanoparticles on hAMCs was measured by the MTT assay. Next, we evaluated the effectiveness of the magnetic nanoparticles as MRI contrast agents. Solutions of SPION were prepared in water at different iron concentrations for relaxivity measurements by a 1.5 Tesla clinical MRI instrument.

RESULTS

The isolated cells showed an adherent spindle shaped morphology. Polyethylene glycol (PEG)-coated SPIONs exhibited a spherical morphology. The average particle size was 20 nm and magnetic saturation was 60 emu/g. Data analysis showed no significant reduction in the percentage of viable cells (97.86 ± 0.41%) after 72 hours at the 125 μg/ml concentration compared with the control. The relaxometry results of this SPION showed a transverse relaxivity of 6.966 (μg/ml.s)(-1).

CONCLUSION

SPIONs coated with PEG used in this study at suitable concentrations had excellent labeling efficiency and biocompatibility for hAMCs.

Labeling mesenchymal cells with DMSA-coated gold and iron oxide nanoparticles: assessment of biocompatibility and potential applications

BACKGROUND

Nanoparticles' unique features have been highly explored in cellular therapies. However, nanoparticles can be cytotoxic. The cytotoxicity can be overcome by coating the nanoparticles with an appropriated surface modification. Nanoparticle coating influences biocompatibility between nanoparticles and cells and may affect some cell properties. Here, we evaluated the biocompatibility of gold and maghemite nanoparticles functionalized with 2,3-dimercaptosuccinic acid (DMSA), Au-DMSA and γ-Fe2O3-DMSA respectively, with human mesenchymal stem cells. Also, we tested these nanoparticles as tracers for mesenchymal stem cells in vivo tracking by computed tomography and as agents for mesenchymal stem cells magnetic targeting.

RESULTS

Significant cell death was not observed in MTT, Trypan Blue and light microscopy analyses. However, ultra-structural alterations as swollen and degenerated mitochondria, high amounts of myelin figures and structures similar to apoptotic bodies were detected in some mesenchymal stem cells. Au-DMSA and γ-Fe2O3-DMSA labeling did not affect mesenchymal stem cells adipogenesis and osteogenesis differentiation, proliferation rates or lymphocyte suppression capability. The uptake measurements indicated that both inorganic nanoparticles were well uptaken by mesenchymal stem cells. However, Au-DMSA could not be detected in microtomograph after being incorporated by mesenchymal stem cells. γ-Fe2O3-DMSA labeled cells were magnetically responsive in vitro and after infused in vivo in an experimental model of lung silicosis.

CONCLUSION

In terms of biocompatibility, the use of γ-Fe2O3-DMSA and Au-DMSA as tracers for mesenchymal stem cells was assured. However, Au-DMSA shown to be not suitable for visualization and tracking of these cells in vivo by standard computed microtomography. Otherwise, γ-Fe2O3-DMSA shows to be a promising agent for mesenchymal stem cells magnetic targeting.

Efficient and safe gene delivery to human corneal endothelium using magnetic nanoparticles

Aim: To develop a safe and efficient method for targeted, anti-apoptotic gene therapy of corneal endothelial cells (CECs). Materials & methods: Magnetofection (MF), a combination of lipofection with magnetic nanoparticles (MNPs; PEI-Mag2, SO-Mag5, PalD1-Mag1), was tested in human CECs and in explanted human corneas. Effects on cell viability and function were investigated. Immunocompatibility was assessed in human peripheral blood mononuclear cells. Results: Silica iron-oxide MNPs (SO-Mag5) combined with X-tremeGENE-HP achieved high transfection efficiency in human CECs and explanted human corneas, without altering cell viability or function. Magnetofection caused no immunomodulatory effects in human peripheral blood mononuclear cells. Magnetofection with anti-apoptotic P35 gene effectively blocked apoptosis in CECs. Conclusion: Magnetofection is a promising tool for gene therapy of corneal endothelial cells with potential for targeted on-site delivery.

Emerging translational research on magnetic nanoparticles for regenerative medicine

Regenerative medicine, which replaces or regenerates human cells, tissues or organs, to restore or establish normal function, is one of the fastest-evolving interdisciplinary fields in healthcare. Over 200 regenerative medicine products, including cell-based therapies, tissue-engineered biomaterials, scaffolds and implantable devices, have been used in clinical development for diseases such as diabetes and inflammatory and immune diseases. To facilitate the translation of regenerative medicine from research to clinic, nanotechnology, especially magnetic nanoparticles have attracted extensive attention due to their unique optical, electrical, and magnetic properties and specific dimensions. In this review paper, we intend to summarize current advances, challenges, and future opportunities of magnetic nanoparticles for regenerative medicine.

Iron oxide nanoparticles for neuronal cell applications: uptake study and magnetic manipulations

Background

The ability to direct and manipulate neuronal cells has important potential in therapeutics and neural network studies. An emerging approach for remotely guiding cells is by incorporating magnetic nanoparticles (MNPs) into cells and transferring the cells into magnetic sensitive units. Recent developments offer exciting possibilities of magnetic manipulations of MNPs-loaded cells by external magnetic fields. In the present study, we evaluated and characterized uptake properties for optimal loading of cells by MNPs. We examined the interactions between MNPs of different cores and coatings, with primary neurons and neuron-like cells.

Results

We found that uncoated-maghemite iron oxide nanoparticles maximally interact and penetrate into cells with no cytotoxic effect. We observed that the cellular uptake of the MNPs depends on the time of incubation and the concentration of nanoparticles in the medium. The morphology patterns of the neuronal cells were not affected by MNPs uptake and neurons remained electrically active. We theoretically modeled magnetic fluxes and demonstrated experimentally the response of MNP-loaded cells to the magnetic fields affecting cell motility. Furthermore, we successfully directed neurite growth orientation along regeneration.

Conclusions

Applying mechanical forces via magnetic mediators is a useful approach for biomedical applications. We have examined several types of MNPs and studied the uptake behavior optimized for magnetic neuronal manipulations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-016-0190-0) contains supplementary material, which is available to authorized users.

Autonomous magnetic labelling of functional mesenchymal stem cells for improved traceability and spatial control in cell therapy applications

Mesenchymal stem cells (MSCs) represent a valuable resource for regenerative medicine treatments for orthopaedic repair and beyond. Following developments in isolation, expansion and differentiation protocols, efforts to promote clinical translation of emerging cellular strategies now seek to improve cell delivery and targeting. This study shows efficient live MSC labelling using silica‐coated magnetic particles (MPs), which enables 3D tracking and guidance of stem cells. A procedure developed for the efficient and unassisted particle uptake was shown to support MSC viability and integrity, while surface marker expression and MSC differentiation capability were also maintained. In vitro, MSCs showed a progressive decrease in labelling over increasing culture time, which appeared to be linked to the dilution effect of cell division, rather than to particle release, and did not lead to detectable secondary particle uptake. Labelled MSC populations demonstrated magnetic responsiveness in vitro through directed migration in culture and, when seeded onto a scaffold, supporting MP‐based approaches to cell targeting. The potential of these silica‐coated MPs for MRI cell tracking of MSC populations was validated in 2D and in a cartilage repair model following cell delivery. These results highlight silica‐coated magnetic particles as a simple, safe and effective resource to enhance MSC targeting for therapeutic applications and improve patient outcomes. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.

Remote Magnetic Orientation of 3D Collagen Hydrogels for Directed Neuronal Regeneration

Hydrogel matrices are valuable platforms for neuronal tissue engineering. Orienting gel fibers to achieve a directed scaffold is important for effective functional neuronal regeneration. However, current methods are limited and require treatment of gels prior to implantation, ex-vivo, without taking into consideration the pathology in the injured site. We have developed a method to control gel orientation dynamically and remotely in situ. We have mixed into collagen hydrogels magnetic nanoparticles then applied an external magnetic field. During the gelation period the magnetic particles aggregated into magnetic particle strings, leading to the alignment of the collagen fibers. We have shown that neurons within the 3D magnetically induced gels exhibited normal electrical activity and viability. Importantly, neurons formed elongated cooriented morphology, relying on the particle strings and fibers as supportive cues for growth. The ability to inject the mixed gel directly into the injured site as a solution then to control scaffold orientation remotely opens future possibilities for therapeutic engineered scaffolds.

Endocytotic potential governs magnetic particle loading in dividing neural cells: studying modes of particle inheritance

AIM

To achieve high and sustained magnetic particle loading in a proliferative and endocytotically active neural transplant population (astrocytes) through tailored magnetite content in polymeric iron oxide particles.

MATERIALS & METHODS

MPs of varying magnetite content were applied to primary-derived rat cortical astrocytes ± static/oscillating magnetic fields to assess labeling efficiency and safety.

RESULTS

Higher magnetite content particles display high but safe accumulation in astrocytes, with longer-term label retention versus lower/no magnetite content particles. Magnetic fields enhanced loading extent. Dynamic live cell imaging of dividing labeled astrocytes demonstrated that particle distribution into daughter cells is predominantly 'asymmetric'.

CONCLUSION

These findings could inform protocols to achieve efficient MP loading into neural transplant cells, with significant implications for post-transplantation tracking/localization.

Extrinsic and Intrinsic Mechanisms by Which Mesenchymal Stem Cells Suppress the Immune System

Mesenchymal stem cells (MSCs) are a group of fibroblast-like multipotent mesenchymal stromal cells that have the ability to differentiate into osteoblasts, adipocytes, and chondrocytes. Recent studies have demonstrated that MSCs possess a unique ability to exert suppressive and regulatory effects on both adaptive and innate immunity in an autologous and allogeneic manner. A vital step in stem cell transplantation is overcoming the potential graft-versus-host disease, which is a limiting factor to transplantation success. Given that MSCs attain powerful differentiation capabilities and also present immunosuppressive properties, which enable them to survive host immune rejection, MSCs are of great interest. Due to their ability to differentiate into different cell types and to suppress and modulate the immune system, MSCs are being developed for treating a plethora of diseases, including immune disorders. Moreover, in recent years, MSCs have been genetically engineered to treat and sometimes even cure some diseases, and the use of MSCs for cell therapy presents new perspectives for overcoming tissue rejection. In this review, we discuss the potential extrinsic and intrinsic mechanisms that underlie MSCs' unique ability to modulate inflammation, and both innate and adaptive immunity.

Bone Marrow-Derived Cells as a Therapeutic Approach to Optic Nerve Diseases

Following optic nerve injury associated with acute or progressive diseases, retinal ganglion cells (RGCs) of adult mammals degenerate and undergo apoptosis. These diseases have limited therapeutic options, due to the low inherent capacity of RGCs to regenerate and due to the inhibitory milieu of the central nervous system. Among the numerous treatment approaches investigated to stimulate neuronal survival and axonal extension, cell transplantation emerges as a promising option. This review focuses on cell therapies with bone marrow mononuclear cells and bone marrow-derived mesenchymal stem cells, which have shown positive therapeutic effects in animal models of optic neuropathies. Different aspects of available preclinical studies are analyzed, including cell distribution, potential doses, routes of administration, and mechanisms of action. Finally, published and ongoing clinical trials are summarized.

Cell Labeling and Targeting with Superparamagnetic Iron Oxide Nanoparticles

Targeted delivery of cells and therapeutic agents would benefit a wide range of biomedical applications by concentrating the therapeutic effect at the target site while minimizing deleterious effects to off-target sites. Magnetic cell targeting is an efficient, safe, and straightforward delivery technique. Superparamagnetic iron oxide nanoparticles (SPION) are biodegradable, biocompatible, and can be endocytosed into cells to render them responsive to magnetic fields. The synthesis process involves creating magnetite (Fe3O4) nanoparticles followed by high-speed emulsification to form a poly(lactic-co-glycolic acid) (PLGA) coating. The PLGA-magnetite SPIONs are approximately 120 nm in diameter including the approximately 10 nm diameter magnetite core. When placed in culture medium, SPIONs are naturally endocytosed by cells and stored as small clusters within cytoplasmic endosomes. These particles impart sufficient magnetic mass to the cells to allow for targeting within magnetic fields. Numerous cell sorting and targeting applications are enabled by rendering various cell types responsive to magnetic fields. SPIONs have a variety of other biomedical applications as well including use as a medical imaging contrast agent, targeted drug or gene delivery, diagnostic assays, and generation of local hyperthermia for tumor therapy or tissue soldering.

Cell-Based Therapy in TBI: Magnetic Retention of Neural Stem Cells In Vivo

Stem cell therapy is under active investigation for traumatic brain injury (TBI). Noninvasive stem cell delivery is the preferred method, but retention of stem cells at the site of injury in TBI has proven challenging and impacts effectiveness. To investigate the effects of applying a magnetic field on cell homing and retention, we delivered human neuroprogenitor cells (hNPCs) labeled with a superparamagnetic nanoparticle into post-TBI animals in the presence of a static magnetic field. We have previously devised a method of loading hNPCs with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles Molday ION Rhodamine B (MIRB™). Labeling of hNPCs (MIRB-hNPCs) does not affect hNPC viability, proliferation, or differentiation. The 0.6 tesla (T) permanent magnet was placed ∼4 mm above the injured parietal cortex prior to intracarotid injection of 4 × 10(4) MIRB-hNPCs. Fluorescence imaging, Perls' Prussian blue histochemistry, immunocytochemistry with SC121, a human-specific antibody, and T2-weighted magnetic resonance imaging ex vivo revealed there was increased homing and retention of MIRB-hNPCs in the injured cortex as compared to the control group in which MIRB-hNPCs were injected in the absence of a static magnetic field. Fluoro-Jade C staining and immunolabeling with specific markers confirmed the viability status of MIRB-hNPCs posttransplantation. These results show that increased homing and retention of MIRB-hNPCs post-TBI by applying a static magnetic field is a promising technique to deliver cells into the CNS for treatment of neurological injuries and neurodegenerative diseases.

Advanced cell therapies: targeting, tracking and actuation of cells with magnetic particles

Regenerative medicine would greatly benefit from a new platform technology that enabled measurable, controllable and targeting of stem cells to a site of disease or injury in the body. Superparamagnetic iron-oxide nanoparticles offer attractive possibilities in biomedicine and can be incorporated into cells, affording a safe and reliable means of tagging. This review describes three current and emerging methods to enhance regenerative medicine using magnetic particles to guide therapeutic cells to a target organ; track the cells using MRI and assess their spatial localization with high precision and influence the behavior of the cell using magnetic actuation. This approach is complementary to the systemic injection of cell therapies, thus expanding the horizon of stem cell therapeutics.

Nanotechnology in bone tissue engineering

Nanotechnology represents a major frontier with potential to significantly advance the field of bone tissue engineering. Current limitations in regenerative strategies include impaired cellular proliferation and differentiation, insufficient mechanical strength of scaffolds, and inadequate production of extrinsic factors necessary for efficient osteogenesis. Here we review several major areas of research in nanotechnology with potential implications in bone regeneration: 1) nanoparticle-based methods for delivery of bioactive molecules, growth factors, and genetic material, 2) nanoparticle-mediated cell labeling and targeting, and 3) nano-based scaffold construction and modification to enhance physicochemical interactions, biocompatibility, mechanical stability, and cellular attachment/survival. As these technologies continue to evolve, ultimate translation to the clinical environment may allow for improved therapeutic outcomes in patients with large bone deficits and osteodegenerative diseases.

FROM THE CLINICAL EDITOR

Traditionally, the reconstruction of bony defects has relied on the use of bone grafts. With advances in nanotechnology, there has been significant development of synthetic biomaterials. In this article, the authors provided a comprehensive review on current research in nanoparticle-based therapies for bone tissue engineering, which should be useful reading for clinicians as well as researchers in this field.

Magnetically Targeted Stem Cell Delivery for Regenerative Medicine

Stem cells play a special role in the body as agents of self-renewal and auto-reparation for tissues and organs. Stem cell therapies represent a promising alternative strategy to regenerate damaged tissue when natural repairing and conventional pharmacological intervention fail to do so. A fundamental impediment for the evolution of stem cell therapies has been the difficulty of effectively targeting administered stem cells to the disease foci. Biocompatible magnetically responsive nanoparticles are being utilized for the targeted delivery of stem cells in order to enhance their retention in the desired treatment site. This noninvasive treatment-localization strategy has shown promising results and has the potential to mitigate the problem of poor long-term stem cell engraftment in a number of organ systems post-delivery. In addition, these same nanoparticles can be used to track and monitor the cells in vivo, using magnetic resonance imaging. In the present review we underline the principles of magnetic targeting for stem cell delivery, with a look at the logic behind magnetic nanoparticle systems, their manufacturing and design variants, and their applications in various pathological models.

Nanocarriers for treatment of ocular neovascularization in the back of the eye: new vehicles for ophthalmic drug delivery

Pathologic neovascularization of the retina is a major cause of substantial and irreversible loss of vision. Drugs are difficult to deliver to the lesions in the back of the eye and this is a major obstacle for the therapeutics. Current pharmacological approach involves an intravitreal injection of anti-VEGF agents to prevent aberrant growth of blood vessels, but it has limitations including therapeutic efficacy and side-effects associated with systemic exposure and invasive surgery. Nanotechnology provides novel opportunities to overcome the limitations of conventional delivery system to reach the back of the eye through fabrication of nanostructures capable of encapsulating and delivering small molecules. This review article introduces various forms of nanocarrier that can be adopted by ocular drug delivery systems to improve current therapy. The application of nanotechnology in medicine brings new hope for ocular drug delivery in the back of the eye to manage the major causes of blindness associated with ocular neovascularization.

Functionalized iron oxide nanoparticles for controlling the movement of immune cells

Immunotherapy is currently being investigated for the treatment of many diseases, including cancer. The ability to control the location of immune cells during or following activation would represent a powerful new technique for this field. Targeted magnetic delivery is emerging as a technique for controlling cell movement and localization. Here we show that this technique can be extended to microglia, the primary phagocytic immune cells in the central nervous system. The magnetized microglia were generated by loading the cells with iron oxide nanoparticles functionalized with CpG oligonucleotides, serving as a proof of principle that nanoparticles can be used to both deliver an immunostimulatory cargo to cells and to control the movement of the cells. The nanoparticle-oligonucleotide conjugates are efficiently internalized, non-toxic, and immunostimulatory. We demonstrate that the in vitro migration of the adherent, loaded microglia can be controlled by an external magnetic field and that magnetically-induced migration is non-cytotoxic. In order to capture video of this magnetically-induced migration of loaded cells, a novel 3D-printed "cell box" was designed to facilitate our imaging application. Analysis of cell movement velocities clearly demonstrate increased cell velocities toward the magnet. These studies represent the initial step towards our final goal of using nanoparticles to both activate immune cells and to control their trafficking within the diseased brain.

An effective strategy of magnetic stem cell delivery for spinal cord injury therapy

Spinal cord injury (SCI) is a condition that results in significant mortality and morbidity. Treatment of SCI utilizing stem cell transplantation represents a promising therapy. However, current conventional treatments are limited by inefficient delivery strategies of cells into the injured tissue. In this study, we designed a magnetic system and used it to accumulate stem cells labelled with superparamagnetic iron oxide nanoparticles (SPION) at a specific site of a SCI lesion. The loading of stem cells with engineered SPIONs that guarantees sufficient attractive magnetic forces was achieved. Further, the magnetic system allowed rapid guidance of the SPION-labelled cells precisely to the lesion location. Histological analysis of cell distribution throughout the cerebrospinal channel showed a good correlation with the calculated distribution of magnetic forces exerted onto the transplanted cells. The results suggest that focused targeting and fast delivery of stem cells can be achieved using the proposed non-invasive magnetic system. With future implementation the proposed targeting and delivery strategy bears advantages for the treatment of disease requiring fast stem cell transplantation.

Imaging of nanoparticle-labeled stem cells using magnetomotive optical coherence tomography, laser speckle reflectometry, and light microscopy

Cell transplantation and stem cell therapy are promising approaches for regenerative medicine and are of interest to researchers and clinicians worldwide. However, currently, no imaging technique that allows three-dimensional in vivo inspection of therapeutically administered cells in host tissues is available. Therefore, we investigate magnetomotive optical coherence tomography (MM-OCT) of cells labeled with magnetic particles as a potential noninvasive cell tracking method. We develop magnetomotive imaging of mesenchymal stem cells for future cell therapy monitoring. Cells were labeled with fluorescent iron oxide nanoparticles, embedded in tissue-mimicking agar scaffolds, and imaged using a microscope setup with an integrated MM-OCT probe. Magnetic particle-induced motion in response to a pulsed magnetic field of 0.2 T was successfully detected by OCT speckle variance analysis, and cross-sectional and volumetric OCT scans with highlighted labeled cells were obtained. In parallel, fluorescence microscopy and laser speckle reflectometry were applied as two-dimensional reference modalities to image particle distribution and magnetically induced motion inside the sample, respectively. All three optical imaging modalities were in good agreement with each other. Thus, magnetomotive imaging using iron oxide nanoparticles as cellular contrast agents is a potential technique for enhanced visualization of selected cells in OCT.

Dynamic inversion enables external magnets to concentrate ferromagnetic rods to a central target

The ability to use magnets external to the body to focus therapy to deep tissue targets has remained an elusive goal in magnetic drug targeting. Researchers have hitherto been able to manipulate magnetic nanotherapeutics in vivo with nearby magnets but have remained unable to focus these therapies to targets deep within the body using magnets external to the body. One of the factors that has made focusing of therapy to central targets between magnets challenging is Samuel Earnshaw's theorem as applied to Maxwell's equations. These mathematical formulations imply that external static magnets cannot create a stable potential energy well between them. We posited that fast magnetic pulses could act on ferromagnetic rods before they could realign with the magnetic field. Mathematically, this is equivalent to reversing the sign of the potential energy term in Earnshaw's theorem, thus enabling a quasi-static stable trap between magnets. With in vitro experiments, we demonstrated that quick, shaped magnetic pulses can be successfully used to create inward pointing magnetic forces that, on average, enable external magnets to concentrate ferromagnetic rods to a central location.

Distribution of mesenchymal stem cells and effects on neuronal survival and axon regeneration after optic nerve crush and cell therapy

Bone marrow-derived cells have been used in different animal models of neurological diseases. We investigated the therapeutic potential of mesenchymal stem cells (MSC) injected into the vitreous body in a model of optic nerve injury. Adult (3–5 months old) Lister Hooded rats underwent unilateral optic nerve crush followed by injection of MSC or the vehicle into the vitreous body. Before they were injected, MSC were labeled with a fluorescent dye or with superparamagnetic iron oxide nanoparticles, which allowed us to track the cells in vivo by magnetic resonance imaging. Sixteen and 28 days after injury, the survival of retinal ganglion cells was evaluated by assessing the number of Tuj1- or Brn3a-positive cells in flat-mounted retinas, and optic nerve regeneration was investigated after anterograde labeling of the optic axons with cholera toxin B conjugated to Alexa 488. Transplanted MSC remained in the vitreous body and were found in the eye for several weeks. Cell therapy significantly increased the number of Tuj1- and Brn3a-positive cells in the retina and the number of axons distal to the crush site at 16 and 28 days after optic nerve crush, although the RGC number decreased over time. MSC therapy was associated with an increase in the FGF-2 expression in the retinal ganglion cells layer, suggesting a beneficial outcome mediated by trophic factors. Interleukin-1β expression was also increased by MSC transplantation. In summary, MSC protected RGC and stimulated axon regeneration after optic nerve crush. The long period when the transplanted cells remained in the eye may account for the effect observed. However, further studies are needed to overcome eventually undesirable consequences of MSC transplantation and to potentiate the beneficial ones in order to sustain the neuroprotective effect overtime.

Magnetic nanoparticles for oligodendrocyte precursor cell transplantation therapies: progress and challenges

Oligodendrocyte precursor cells (OPCs) have shown high promise as a transplant population to promote regeneration in the central nervous system, specifically, for the production of myelin - the protective sheath around nerve fibers. While clinical trials for these cells have commenced in some areas, there are currently key barriers to the translation of neural cell therapies. These include the ability to (a) image transplant populations in vivo; (b) genetically engineer transplant cells to augment their repair potential; and (c) safely target cells to sites of pathology. Here, we review the evidence that magnetic nanoparticles (MNPs) are a 'multifunctional nanoplatform' that can aid in safely addressing these translational challenges in neural cell/OPC therapy: by facilitating real-time and post-mortem assessment of transplant cell biodistribution, and biomolecule delivery to transplant cells, as well as non-invasive 'magnetic cell targeting' to injury sites by application of high gradient fields. We identify key issues relating to the standardization and reporting of physicochemical and biological data in the field; we consider that it will be essential to systematically address these issues in order to fully evaluate the utility of the MNP platform for neural cell transplantation, and to develop efficacious neurocompatible particles for translational applications.

Magnetic nanoparticles for oligodendrocyte precursor cell transplantation therapies: progress and challenges

Oligodendrocyte precursor cells (OPCs) have shown high promise as a transplant population to promote regeneration in the central nervous system, specifically, for the production of myelin – the protective sheath around nerve fibers. While clinical trials for these cells have commenced in some areas, there are currently key barriers to the translation of neural cell therapies. These include the ability to (a) image transplant populations in vivo; (b) genetically engineer transplant cells to augment their repair potential; and (c) safely target cells to sites of pathology. Here, we review the evidence that magnetic nanoparticles (MNPs) are a ‘multifunctional nanoplatform’ that can aid in safely addressing these translational challenges in neural cell/OPC therapy: by facilitating real-time and post-mortem assessment of transplant cell biodistribution, and biomolecule delivery to transplant cells, as well as non-invasive ‘magnetic cell targeting’ to injury sites by application of high gradient fields. We identify key issues relating to the standardization and reporting of physicochemical and biological data in the field; we consider that it will be essential to systematically address these issues in order to fully evaluate the utility of the MNP platform for neural cell transplantation, and to develop efficacious neurocompatible particles for translational applications.

Stem cell therapy for glaucoma: science or snake oil?

In recent years there has been substantial progress in developing stem cell treatments for glaucoma. As a downstream approach that targets the underlying susceptibility of retinal ganglion and trabecular meshwork cells, stem cell therapy has the potential to both replace lost, and protect damaged, cells by secreting neurotrophic factors. A variety of sources, including embryonic cells, adult cells derived from the central nervous system, and induced pluripotent stem cells show promise as therapeutic approaches. Even though safety concerns and ethical controversies have limited clinical implementation, some institutions have already commercialized stem cell therapy and are using direct-to-consumer advertising to attract patients with glaucoma. We review the progress of stem cell therapy and its current commercial availability.

Micropatterned polymeric nanosheets for local delivery of an engineered epithelial monolayer

Like a carpet for cells, micropatterned polymeric nanosheets are developed toward local cell delivery. The nanosheets direct morphogenesis of retinal pigment epithelial (RPE) cells and allow for the injection of an engineered RPE monolayer through syringe needles without the loss of cell viability. Such an ultrathin carrier has the promise of a minimally invasive delivery of cells into narrow tissue spaces.

Synthesis of brightly PEGylated luminescent magnetic upconversion nanophosphors for deep tissue and dual MRI imaging

A method is developed to fabricate monodispersed biocompatible Yb/Er or Yb/Tm doped β-NaGdF4 upconversion phosphors using polyelectrolytes to prevent irreversible particle aggregation during conversion of the precursor, Gd2 O(CO3 )2.H2 O:Yb/Er or Yb/Tm, to β-NaGdF4 :Yb/Er or Yb/Tm. The polyelectrolyte on the outer surface of nanophosphors also provided an amine tag for PEGylation. This method is also employed to fabricate PEGylated magnetic upconversion phosphors with Fe3 O4 as the core and β-NaGdF4 as a shell. These magnetic upconversion nanophosphors have relatively high saturation magnetization (7.0 emu g(-1) ) and magnetic susceptibility (1.7 × 10(-2) emu g(-1) Oe(-1) ), providing them with large magnetophoretic mobilities. The magnetic properties for separation and controlled release in flow, their optical properties for cell labeling, deep tissue imaging, and their T1 - and T2 -weighted magnetic resonance imaging (MRI) relaxivities are studied. The magnetic upconversion phosphors display both strong magnetophoresis, dual MRI imaging (r1 = 2.9 mM(-1) s(-1) , r2 = 204 mM(-1) s(-1) ), and bright luminescence under 1 cm chicken breast tissue.

Long-term effects of magnetically targeted ferumoxide-labeled human neural stem cells in focal cerebral ischemia

The long-term effect of magnetically targeted neural stem cells in a rat focal cerebral ischemia model was investigated. In middle cerebral artery occlusion (MCAO) stroke model rats, ferumoxide-labeled human neural stem cells (hNSCs) were injected into the tail vein. MCAO rats were divided into three groups: ischemia only (IO), ischemia with NSC injection (IC), and ischemia with NSC injection and the use of magnet targeting (IM). Four weeks after MCAO and 3 weeks posttransplantation, a greater number of hNSCs were found in ischemic lesion sites in IM rat brain compared with IO and IC animals. In addition, differentiation of hNSCs into neurons or astrocytes and angiogenesis were markedly increased. In IM rats, infarct volume was considerably reduced, and function was significantly improved. The present study indicates that long-term use of magnetic fields may be a useful way to improve the efficacy of targeted migration of stem cells and functional deficits in stem cell-based therapy for ischemic brain injury.

Noninvasive pulsed focused ultrasound allows spatiotemporal control of targeted homing for multiple stem cell types in murine skeletal muscle and the magnitude of cell homing can be increased through repeated applications

Stem cells are promising therapeutics for cardiovascular diseases, and i.v. injection is the most desirable route of administration clinically. Subsequent homing of exogenous stem cells to pathological loci is frequently required for therapeutic efficacy and is mediated by chemoattractants (cell adhesion molecules, cytokines, and growth factors). Homing processes are inefficient and depend on short-lived pathological inflammation that limits the window of opportunity for cell injections. Noninvasive pulsed focused ultrasound (pFUS), which emphasizes mechanical ultrasound-tissue interactions, can be precisely targeted in the body and is a promising approach to target and maximize stem cell delivery by stimulating chemoattractant expression in pFUS-treated tissue prior to cell infusions. We demonstrate that pFUS is nondestructive to murine skeletal muscle tissue (no necrosis, hemorrhage, or muscle stem cell activation) and initiates a largely M2-type macrophage response. We also demonstrate that local upregulation of chemoattractants in pFUS-treated skeletal muscle leads to enhance homing, permeability, and retention of human mesenchymal stem cells (MSC) and human endothelial precursor cells (EPC). Furthermore, the magnitude of MSC or EPC homing was increased when pFUS treatments and cell infusions were repeated daily. This study demonstrates that pFUS defines transient "molecular zip codes" of elevated chemoattractants in targeted muscle tissue, which effectively provides spatiotemporal control and tunability of the homing process for multiple stem cell types. pFUS is a clinically translatable modality that may ultimately improve homing efficiency and flexibility of cell therapies for cardiovascular diseases.

ARPE-19 cell uptake of small and ultrasmall superparamagnetic iron oxide

PURPOSE

To investigate the cytotoxicity, cellular intake and magnetic field interaction of three superparamagnetic iron oxide (SPIO) and one ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles on ARPE-19 cells.

METHODS

Two FDA-approved SPIO nanoparticles (Endorem and Lumirem), one commercial SPIO(FluidMag-L) and one FDA-approved USPIO (Feraheme) were tested. Nanoparticle suspensions were diluted and prepared in high- (1000 Fe-ug/ml) and low- (100 Fe-ug/ml) dose suspensions. ARPE-19 cells were incubated in four 24-well plates and the medium changed every other day until cells attained 80% confluence. Nanoparticle cytotoxicity was evaluated using the XTT cytotoxicity assay. Cellular attraction was tested after digestion of the cells in collagenase A (1 mg/ml) overnight. A 3500 Gauss neodymium magnet was used to attract cells to the well walls. ARPE-19 cell ultrastructure was evaluated by transmission electron microscopy (TEM) to determine the specific locations of nanoparticles within the cell membranes.

RESULTS

Cytotoxicity assessment by the XTT assay revealed that ARPE-19 cells that were exposed to either concentration of Endorem, FLuidMag-L, Feraheme non-conjugated with protamine and heparin or Lumirem demonstrated no statistically significant toxicity. Cells exposed to Feraheme when conjugated with protamine and heparin presented severe toxicity in both concentrations. When a magnetic field was applied, all nanoparticle-containing samples, except Feraheme non-conjugated form, were promptly attracted. TEM and prussian blue staining examination revealed that Feraheme alone was not initially capable of cellular uptake. This issue was solved by conjugating Feraheme with protamine and heparin (although cytotoxicity was found on those samples). Endorem, FLuidMag-L, Feraheme conjugated form were found within the cytoplasm of ARPE-19 cells.

CONCLUSIONS

Ferahame when conjugated with protamine and heparin was cytotoxic at the higher and lower doses, as revealed by the XTT assay. Endorem and FluidMag-L were not toxic at the studied concentrations. Feraheme non-conjugated solutions and Lumirem solutions provided were harmless but were not internalized by ARPE-19 cells. All the studied nanoparticles were attracted to the magnetic field except Feraheme in the non-conjugated form.

Influence of Iron Oxide Nanoparticles on Innate and Genetically Modified Secretion Profiles of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have well-established paracrine effects that are proving to be therapeutically useful. This potential is based on the ability of MSCs to secrete a range of neuroprotective and anti-inflammatory molecules. Previous work in our laboratory has demonstrated that intravenous injection of MSCs, treated with superparamagnetic iron oxide nanoparticle fluidMAG-D resulted in enhanced levels of glial-derived neurotrophic factor, ciliary neurotrophic factor, hepatocyte growth factor and interleukin-10 in the dystrophic rat retina. In this present study we investigated whether the concentration of fluidMAG-D in cell culture media affects the secretion of these four molecules in vitro. In addition, we assessed the effect of fluidMAG-D concentration on retinoschisin secretion from genetically modified MSCs. ELISA-assayed secretion of these molecules was measured using escalating concentrations of fluidMAG-D which resulted in MSC iron loads of 0, 7, 120, or 274 pg iron oxide per cell respectively. Our results demonstrated glial-derived neurotrophic factor and hepatocyte growth factor secretion was significantly decreased but only at the 96 hour's time-point whereas no statistically significant effect was seen with ciliary neurotrophic factor secretion. Whereas no effect was observed on culture media concentrations of retinoschisin with increasing iron oxide load, a statistically significant increase in cell lysate retinoschisin concentration (p = 0.01) was observed suggesting that increasing fluidMAG-D concentration did increase retinoschisin production but this did not lead to greater secretion. We hypothesize that higher concentrations of iron-oxide nanoparticle fluidMAG-D have an effect on the innate ability of MSCs to secrete therapeutically useful molecules and also on secretion from genetically modified cells. Further work is required to verify these in vitro finding using in vivo model systems.

The application of super paramagnetic iron oxide-labeled mesenchymal stem cells in cell-based therapy

Mesenchymal stem cell (MSC)-based therapy has great potential for tissue regeneration. However, being able to monitor the in vivo behavior of implanted MSCs and understand the fate of these cells is necessary for further development of successful therapies and requires an effective, non-invasive and non-toxic technique for cell tracking. Super paramagnetic iron oxide (SPIO) is an idea label and tracer of MSCs. MRI can be used to follow SPIO-labeled MSCs and has been proposed as a gold standard for monitoring the in vivo biodistribution and migration of implanted SPIO-labeled MSCs. This review discusses the biological effects of SPIO labeling on MSCs and the therapeutic applications of local or systemic delivery of these labeled cells.

Superparamagnetic iron oxide nanoparticle-based delivery systems for biotherapeutics

INTRODUCTION

Superparamagnetic iron oxide nanoparticle (SPION)-based carrier systems have many advantages over other nanoparticle-based systems. They are biocompatible, biodegradable, facilely tunable and superparamagnetic and thus controllable by an external magnetic field. These attributes enable their broad biomedical applications. In particular, magnetically driven carriers are drawing considerable interest as an emerging therapeutic delivery system because of their superior delivery efficiency.

AREAS COVERED

This article reviews the recent advances in use of SPION-based carrier systems to improve the delivery efficiency and target specificity of biotherapeutics. The authors examine various formulations of SPION-based delivery systems, including SPION micelles, clusters, hydrogels, liposomes and micro/nanospheres, as well as their specific applications in delivery of biotherapeutics.

EXPERT OPINION

Recently, biotherapeutics including therapeutic cells, proteins and genes have been studied as alternative treatments to various diseases. Despite the advantages of high target specificity and low adverse effects, clinical translation of biotherapeutics has been hindered by the poor stability and low delivery efficiency compared with chemical drugs. Accordingly, biotherapeutic delivery systems that can overcome these limitations are actively pursued. SPION-based materials can be ideal candidates for developing such delivery systems because of their excellent biocompatibility and superparamagnetism that enables long-term accumulation/retention at target sites by utilization of a suitable magnet. In addition, synthesis technologies for production of finely tuned, homogeneous SPIONs have been well developed, which may promise their rapid clinical translation.

Personalized nanomedicine advancements for stem cell tracking

Recent technological developments in biomedicine have facilitated the generation of data on the anatomical, physiological and molecular level for individual patients and thus introduces opportunity for therapy to be personalized in an unprecedented fashion. Generation of patient-specific stem cells exemplifies the efforts toward this new approach. Cell-based therapy is a highly promising treatment paradigm; however, due to the lack of consistent and unbiased data about the fate of stem cells in vivo, interpretation of therapeutic effects remains challenging hampering the progress in this field. The advent of nanotechnology with a wide palette of inorganic and organic nanostructures has expanded the arsenal of methods for tracking transplanted stem cells. The diversity of nanomaterials has revolutionized personalized nanomedicine and enables individualized tailoring of stem cell labeling materials for the specific needs of each patient. The successful implementation of stem cell tracking will likely be a significant driving force that will contribute to the further development of nanotheranostics. The purpose of this review is to emphasize the role of cell tracking using currently available nanoparticles.