Efficient in vitro labeling of human neural precursor cells with superparamagnetic iron oxide particles: relevance for in vivo cell tracking

ADSCs labeled with SPIONs tracked in corpus cavernosum of rat and miniature pig by MR imaging and histological examination

Adipose tissue-derived stem cells (ADSCs) have been shown to improve erectile function in animal models of erectile dysfunction. However, few studies have been carried out using a reliable in vivo imaging method to trace transplanted cells in real time, which is necessary for systematic investigation of cell therapy. The study aims to explore the feasibility of non-invasively monitoring intracavernous injection of ADSCs in rat and miniature pig corpus cavernosum using in vivo magnetic resonance (MR) imaging. Thirty-six male Sprague Dawley rats (10 weeks old) and six healthy, sexually mature male miniature pigs (20 kg weight) were obtained. ADSCs were isolated from paratesticular fat of donor rats and cultured. Then ADSCs were labeled with superparamagnetic iron oxide nanoparticles (SPIONs), a type of MR imaging contrast agent, before transplantation into rats and pigs. After intracavernous injection, all rats and pigs underwent and were analyzed by MR imaging at the day of ADSC transplantation and follow-up at 1, 2 and 4 weeks after transplantation. In addition, penile histological examination was performed on all rats and pigs before (n = 6) and at 1 day (n = 6), 1 week (n = 6), 2 weeks (n = 6) or 4 weeks (n = 12) after ADSC transplantation. SPION-labeled ADSCs demonstrated a strong decreased signal intensity compared with distilled water, unlabeled ADSCs or agarose gel. SPION-labeled ADSCs showed a hypointense signal at all concentrations, and the greatest hypointense signal was observed at the concentration of 1 × 106. MR images of the corpus cavernosum showed a hypointense signal located at the injection site. T2*-weighted signal intensity increased over the course of 1 week after ADSCs transplantation, and demonstrated a similar MR signal with that before ADSCs transplantation. After SPION-labeled ADSC injection, T2*-weighted MR imaging clearly demonstrated a marked hypointense signal in pig corpus cavernosum. The T2*-weighted signal faded over time, similar to the MR imaging results in rats. Obvious acute inflammatory exudation was induced by intracavernous injection, and the T2*-weighted signal intensity of these exudation was higher than that of the injection site. The presence of iron was detected by Prussian blue staining, which demonstrated ADSC retention in rat corpus cavernosum. Lack of cellular infiltrations were demonstrated by H&E staining before and 4 weeks after transplantation, which indicated no negative immune response by rats. Prussian blue staining was positive for iron oxide nanoparticles at 2 weeks after transplantation. SPION-labeled ADSCs showed a clear hypointense signal on T2-weight MRI in vitro and in vivo. The MR signal intensity in the corpus cavernosum of the rats and miniature pigs faded and disappeared over time after ADSC transplantation. These findings suggested that MR imaging could trace transplanted ADSCs in the short term in the corpus cavernosum of animals.

Optimization of Multimodal Nanoparticles Internalization Process in Mesenchymal Stem Cells for Cell Therapy Studies

Considering there are several difficulties and limitations in labeling stem cells using multifunctional nanoparticles (MFNP), the purpose of this study was to determine the optimal conditions for labeling human bone marrow mesenchymal stem cells (hBM-MSC), aiming to monitor these cells in vivo. Thus, this study provides information on hBM-MSC direct labeling using multimodal nanoparticles in terms of concentration, magnetic field, and period of incubation while maintaining these cells’ viability and the homing ability for in vivo experiments. The cell labeling process was assessed using 10, 30, and 50 µg Fe/mL of MFNP, with periods of incubation ranging from 4 to 24 h, with or without a magnetic field, using optical microscopy, near-infrared fluorescence (NIRF), and inductively coupled plasma mass spectrometry (ICP-MS). After the determination of optimal labeling conditions, these cells were applied in vivo 24 h after stroke induction, intending to evaluate cell homing and improve NIRF signal detection. In the presence of a magnetic field and utilizing the maximal concentration of MFNP during cell labeling, the iron load assessed by NIRF and ICP-MS was four times higher than what was achieved before. In addition, considering cell viability higher than 98%, the recommended incubation time was 9 h, which corresponded to a 25.4 pg Fe/cell iron load (86% of the iron load internalized in 24 h). The optimization of cellular labeling for application in the in vivo study promoted an increase in the NIRF signal by 215% at 1 h and 201% at 7 h due to the use of a magnetized field during the cellular labeling process. In the case of BLI, the signal does not depend on cell labeling showing no significant differences between unlabeled or labeled cells (with or without a magnetic field). Therefore, the in vitro cellular optimized labeling process using magnetic fields resulted in a shorter period of incubation with efficient iron load internalization using higher MFNP concentration (50 μgFe/mL), leading to significant improvement in cell detection by NIRF technique without compromising cellular viability in the stroke model.

Transplantation of human embryonic stem cells alleviates motor dysfunction in AAV2-Htt171-82Q transfected rat model of Huntington's disease

BACKGROUND

Human embryonic stem cells (hESCs) transplantation had shown to provide a potential source of cells in neurodegenerative disease studies and lead to behavioral recovery in lentivirus transfected or, toxin-induced Huntington's disease (HD) rodent model. Here, we aimed to observe if transplantation of superparamagnetic iron oxide nanoparticle (SPION)-labeled hESCs could migrate in the neural degenerated area and improve motor dysfunction in an AAV2-Htt171-82Q transfected Huntington rat model.

METHODS

All animals were randomly allocated into three groups at first: HD group, sham group, and control group. After six weeks, the animals of the HD group and sham group were again divided into two subgroups depending on animals receiving either ipsilateral or contralateral hESCs transplantation. We performed cylinder test and stepping test every two weeks after AAV2-Htt171-82Q injection and hESCs transplantation. Stem cell tracking was performed once per two weeks using T2 and T2*-weighted images at 4.7 Tesla MRI. We also performed immunohistochemistry and immunofluorescence staining to detect the presence of hESCs markers, huntingtin protein aggregations, and iron in the striatum.

RESULTS

After hESCs transplantation, the Htt virus-injected rats exhibited significant behavioral improvement in behavioral tests. SPION labeled hESCs showed migration with hypointense signal in MRI. The cells were positive with βIII-tubulin, GABA, and DARPP32.

CONCLUSION

Collectively, our results suggested that hESCs transplantation can be a potential treatment for motor dysfunction of Huntington's disease.

In vivo Cell Tracking Using Non-invasive Imaging of Iron Oxide-Based Particles with Particular Relevance for Stem Cell-Based Treatments of Neurological and Cardiac Disease

Stem cell-based therapeutics is a rapidly developing field associated with a number of clinical challenges. One such challenge lies in the implementation of methods to track stem cells and stem cell-derived cells in experimental animal models and in the living patient. Here, we provide an overview of cell tracking in the context of cardiac and neurological disease, focusing on the use of iron oxide-based particles (IOPs) visualized in vivo using magnetic resonance imaging (MRI). We discuss the types of IOPs available for such tracking, their advantages and limitations, approaches for labeling cells with IOPs, biological interactions and effects of IOPs at the molecular and cellular levels, and MRI-based and associated approaches for in vivo and histological visualization. We conclude with reviews of the literature on IOP-based cell tracking in cardiac and neurological disease, covering both preclinical and clinical studies.

Iron Oxide Nanoparticles as Theranostic Agents in Cancer Immunotherapy

Starting from the mid-1990s, several iron oxide nanoparticles (NPs) were developed as MRI contrast agents. Since their sizes fall in the tenths of a nanometer range, after i.v. injection these NPs are preferentially captured by the reticuloendothelial system of the liver. They have therefore been proposed as liver-specific contrast agents. Even though their unfavorable cost/benefit ratio has led to their withdrawal from the market, innovative applications have recently prompted a renewal of interest in these NPs. One important and innovative application is as diagnostic agents in cancer immunotherapy, thanks to their ability to track tumor-associated macrophages (TAMs) in vivo. It is worth noting that iron oxide NPs may also have a therapeutic role, given their ability to alter macrophage polarization. This review is devoted to the most recent advances in applications of iron oxide NPs in tumor diagnosis and therapy. The intrinsic therapeutic effect of these NPs on tumor growth, their capability to alter macrophage polarization and their diagnostic potential are examined. Innovative strategies for NP-based drug delivery in tumors (e.g., magnetic resonance targeting) will also be described. Finally, the review looks at their role as tracers for innovative, and very promising, imaging techniques (magnetic particle imaging-MPI).

Synthesis of SPIO Nanoparticles and the Subsequent Applications in Stem Cell Labeling for Parkinson's Disease

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the midbrain, and the stem cell transplantation method provides a promising strategy for the treatment. In these studies, tracking the biological behaviors of the transplanted cells in vivo is essential for a basic understanding of stem cell function and evaluation of clinical effectiveness. In the present study, we developed a novel ultrasmall superparamagnetic iron oxide nanoparticles coating with the polyacrylic acid (PAA) and methoxypolyethylene glycol amine (PEG) by thermal decomposition method and a two-step modification. The USPIO-PAA/PEG NPs have a uniform diameter of 10.07 ± 0.55 nm and proper absorption peak of the corresponding ligands, as showed by TEM and FTIR. MTT showed that the survival of cells incubated with USPIO-PAA/PEG NPs remained above 96%. The synthesized USPIO-PAA/PEG had a good relaxation rate of 84.65 s^-1 Mm^-1, indicating that they could be efficiently uptake and traced by MRI. Furthermore, the primary human adipose-derived stem cells (HADSCs) were characterized, labeled with USPIO-PAA/PEG and transplanted into the striatum of 6-hydroxydopamine (6-OHDA)-induced PD rat models. The labeled cells could be traced by MRI for up to 3 weeks after the transplantation surgery; moreover, transplantation with the labeled HADSCs significantly attenuated apomorphine-induced rotations in PD models and increased the number of the dopaminergic neurons in the substania nigra. Overall, the development of USPIO-PAA/PEG NPs provides a promising tool for in vivo tracing technique of cell therapy and identifies a novel strategy to track stem cells with therapeutic potential in PD.

Advanced clinical imaging for the evaluation of stem cell based therapies

Introduction: As stem cell treatments reach closer to the clinic, the need for appropriate noninvasive imaging for accurate disease diagnosis, treatment planning, follow-up, and early detection of complications, is constantly rising. Clinical radiology affords an extensive arsenal of advanced imaging techniques, to provide anatomical and functional information on the whole spectrum of stem cell treatments from diagnosis to follow-up.Areas covered: This manuscript aims at providing a critical review of major published studies on the utilization of advanced imaging for stem cell treatments. Uses of magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, and positron emission tomography (PET) are reviewed and interrogated for their applicability to stem cell imaging.Expert opinion: A wide spectrum of imaging methods have been utilized for the evaluation of stem cell therapies. The majority of published techniques are not clinically applicable, using methods exclusively applicable to animals or technology irrelevant to current clinical practice. Harmonization of preclinical methods with clinical reality is necessary for the timely translation of stem cell therapies to the clinic. Methods such as diffusion weighted MRI, hybrid imaging, and contrast-enhanced ultrasound hold great promise and should be routinely incorporated in the evaluation of patients receiving stem cell treatments.

Therapeutic application of exosomes in ischaemic stroke

Ischaemic stroke is a leading cause of long-term disability in the world, with limited effective treatments. Increasing evidence demonstrates that exosomes are involved in ischaemic pathology and exhibit restorative therapeutic effects by mediating cell–cell communication. The potential of exosome therapy for ischaemic stroke has been actively investigated in the past decade. In this review, we mainly discuss the current knowledge of therapeutic applications of exosomes from different cell types, different exosomal administration routes, and current advances of exosome tracking and targeting in ischaemic stroke. We also briefly summarised the pathology of ischaemic stroke, exosome biogenesis, exosome profile changes after stroke as well as registered clinical trials of exosome-based therapy.

Nanoparticles for Stem Cell Therapy Bioengineering in Glioma

Gliomas are a dismal disease associated with poor survival and high morbidity. Current standard treatments have reached a therapeutic plateau even after combining maximal safe resection, radiation, and chemotherapy. In this setting, stem cells (SCs) have risen as a promising therapeutic armamentarium, given their intrinsic tumor homing as well as their natural or bioengineered antitumor properties. The interplay between stem cells and other therapeutic approaches such as nanoparticles holds the potential to synergize the advantages from the combined therapeutic strategies. Nanoparticles represent a broad spectrum of synthetic and natural biomaterials that have been proven effective in expanding diagnostic and therapeutic efforts, either used alone or in combination with immune, genetic, or cellular therapies. Stem cells have been bioengineered using these biomaterials to enhance their natural properties as well as to act as their vehicle when anticancer nanoparticles need to be delivered into the tumor microenvironment in a very precise manner. Here, we describe the recent developments of this new paradigm in the treatment of malignant gliomas.

Intracellular Labeling with Extrinsic Probes: Delivery Strategies and Applications

Extrinsic probes have outstanding properties for intracellular labeling to visualize dynamic processes in and of living cells, both in vitro and in vivo. Since extrinsic probes are in many cases cell-impermeable, different biochemical, and physical approaches have been used to break the cell membrane barrier for direct delivery into the cytoplasm. In this Review, these intracellular delivery strategies are discussed, briefly explaining the mechanisms and how they are used for live-cell labeling applications. Methods that are discussed include three biochemical agents that are used for this purpose-purpose-different nanocarriers, cell penetrating peptides and the pore-foraming bacterial toxin streptolysin O. Most successful intracellular label delivery methods are, however, based on physical principles to permeabilize the membrane and include electroporation, laser-induced photoporation, micro- and nanoinjection, nanoneedles or nanostraws, microfluidics, and nanomachines. The strengths and weaknesses of each strategy are discussed with a systematic comparison provided. Finally, the extrinsic probes that are reported for intracellular labeling so-far are summarized, together with the delivery strategies that are used and their performance. This combined information should provide for a useful guide for choosing the most suitable delivery method for the desired probes.

MXD3 antisense oligonucleotide with superparamagnetic iron oxide nanoparticles: A new targeted approach for neuroblastoma

Neuroblastoma (NB) is the most common extracranial solid tumor in children. The outcomes for aggressive forms of NB remain poor. The aim of this study was to develop a new molecular-targeted therapy for NB using an antisense oligonucleotide (ASO) and superparamagnetic iron oxide (SPIO) nanoparticles (NPs), as a delivery vehicle, targeting the transcription regulator MAX dimerization protein 3 (MXD3). We previously discovered that MXD3 was highly expressed in high-risk NB, acting as an anti-apoptotic factor; therefore, it can be a good therapeutic target. In this study, we developed two ASO-NP complexes using electrostatic conjugation to polyethylenimine-coated SPIO NPs and chemical conjugation to amphiphilic polymers on amine-functionalized SPIO NPs. Both ASO-NP complexes demonstrated MXD3 knockdown, which resulted in apoptosis in NB cells. ASO chemically-conjugated NP complexes have the potential to be used in the clinic as they showed great efficacy with minimum NP-associated cytotoxicity.

A Safe and Effective Magnetic Labeling Protocol for MRI-Based Tracking of Human Adult Neural Stem Cells

Magnetic resonance imaging (MRI) provides a unique tool for in vivo visualization and tracking of stem cells in the brain. This is of particular importance when assessing safety of experimental cell treatments in the preclinical or clinical setup. Yet, specific imaging requires an efficient and non-perturbing cellular magnetic labeling which precludes adverse effects of the tag, e.g., the impact of iron-oxide-nanoparticles on the critical differentiation and integration processes of the respective stem cell population investigated. In this study we investigated the effects of very small superparamagnetic iron oxide particle (VSOP) labeling on viability, stemness, and neuronal differentiation potential of primary human adult neural stem cells (haNSCs). Cytoplasmic VSOP incorporation massively reduced the transverse relaxation time T2, an important parameter determining MR contrast. Cells retained cytoplasmic label for at least a month, indicating stable incorporation, a necessity for long-term imaging. Using a clinical 3T MRI, 1 × 10³ haNSCs were visualized upon injection in a gel phantom, but detection limit was much lower (5 × 10⁴ cells) in layer phantoms and using an imaging protocol feasible in a clinical scenario. Transcriptional analysis and fluorescence immunocytochemistry did not reveal a detrimental impact of VSOP labeling on important parameters of cellular physiology with cellular viability, stemness and neuronal differentiation potential remaining unaffected. This represents a pivotal prerequisite with respect to clinical application of this method.

In Vivo MR Imaging of Dual MRI Reporter Genes and Deltex-1 Gene-modified Human Mesenchymal Stem Cells in the Treatment of Closed Penile Fracture

PURPOSE

The purpose of this study was to investigate the feasibility of dual magnetic resonance imaging (MRI) reporter genes, including ferritin heavy subunit (Fth) and transferrin receptor (TfR), which provide sufficient MRI contrast for in vivo MRI tracking, and the Deltex-1 (DTX1) gene, which promotes human mesenchymal stem cell (hMSC) differentiation to smooth muscle cells (SMCs), to treat closed penile fracture (CPF).

METHODS

Multi-gene co-expressing hMSCs were generated. The expression of mRNA and proteins was assessed, and the original biological properties of hMSCs were determined and compared. The intracellular uptake of iron was evaluated, and the ability to differentiate into SMCs was detected. Fifty rabbits with CPF were randomly transplanted with PBS, hMSCs, Fth-TfR-hMSCs, DTX1-hMSCs, and Fth-TfR-DTX1-hMSCs. In vivo MRI was performed to detect the distribution and migration of the grafted cells and healing progress of CPF, and the results were correlated with histology.

RESULTS

The mRNA and proteins of the multi-gene were highly expressed. The transgenes could not influence the original biological properties of hMSCs. The dual MRI reporter genes increased the iron accumulation capacity, and the DTX1 gene promoted hMSC differentiation into SMCs. The distribution and migration of the dual MRI reporter gene-modified hMSCs, and the healing state of CPF could be obviously detected by MRI and confirmed by histology.

CONCLUSION

The dual MRI reporter genes could provide sufficient MRI contrast, and the distribution and migration of MSCs could be detected in vivo. The DTX1 gene can promote MSC differentiation into SMCs for the treatment of CPF and effectively inhibit granulation tissue formation.

Neuroimaging and clinical trials with stem cells in amyotrophic lateral sclerosis: present and future perspectives

Amyotrophic lateral sclerosis is a rare neurodegenerative disease with a rapid fatal course. The absence of effective treatments has led to new lines of research, some of which are based on stem cells. Surgical injection into the spinal cord, the most common route of administration of stem cells, has proven safe in trials to test the safety of the procedure. Nevertheless, challenges remain, such as determining the best route of administration or the way of checking the survival of the cells and their interaction with the therapeutic target. To date, the mission of neuroimaging techniques has been to detect lesions and complications in the spine and spinal cord, but neuroimaging also has the potential to supplant histologic study in analyzing the relations between the implanted cells and the therapeutic target, and as biomarkers of the disease, by measuring morphological and functional changes after treatment. These developments would increase the role of radiologists in the clinical management of patients with amyotrophic lateral sclerosis.

MRI Tracking of iPS Cells-Induced Neural Stem Cells in Traumatic Brain Injury Rats

Induced pluripotent stem cells (iPS cells) are promising cell source for stem cell replacement strategy applied to brain injury caused by traumatic brain injury (TBI) or stroke. Neural stem cell (NSCs) derived from iPS cells could aid the reconstruction of brain tissue and the restoration of brain function. However, tracing the fate of iPS cells in the host brain is still a challenge. In our study, iPS cells were derived from skin fibroblasts using the four classic factors Oct4, Sox2, Myc, and Klf4. These iPS cells were then induced to differentiate into NSCs, which were incubated with superparamagnetic iron oxides (SPIOs) in vitro. Next, 30 TBI rat models were prepared and divided into three groups (n = 10). One week after brain injury, group A&B rats received implantation of NSCs (labeled with SPIOs), while group C rats received implantation of non-labeled NSCs. After cell implantation, all rats underwent T2*-weighted magnetic resonance imaging (MRI) scan at day 1, and 1 week to 4 weeks, to track the distribution of NSCs in rats' brains. One month after cell implantation, manganese-enhanced MRI (ME-MRI) scan was performed for all rats. In group B, diltiazem was infused during the ME-MRI scan period. We found that (1) iPS cells were successfully derived from skin fibroblasts using the four classic factors Oct4, Sox2, Myc, and Klf4, expressing typical antigens including SSEA4, Oct4, Sox2, and Nanog; (2) iPS cells were induced to differentiate into NSCs, which could express Nestin and differentiate into neural cells and glial cells; (3) NSCs were incubated with SPIOs overnight, and Prussian blue staining showed intracellular particles; (4) after cell implantation, T2*-weighted MRI scan showed these implanted NSCs could migrate to the injury area in chronological order; (5) the subsequent ME-MRI scan detected NSCs function, which could be blocked by diltiazem. In conclusion, using an in vivo MRI tracking technique to trace the fate of iPS cells-induced NSCs in host brain is feasible.

Superparamagnetic iron oxide nanoparticle targeting of adipose tissue-derived stem cells in diabetes-associated erectile dysfunction

Erectile dysfunction (ED) is a major complication of diabetes, and many diabetic men with ED are refractory to common ED therapies. Adipose tissue-derived stem cells (ADSCs) have been shown to improve erectile function in diabetic animal models. However, inadequate cell homing to damaged sites has limited their efficacy. Therefore, we explored the effect of ADSCs labeled with superparamagnetic iron oxide nanoparticles (SPIONs) on improving the erectile function of streptozotocin-induced diabetic rats with an external magnetic field. We found that SPIONs effectively incorporated into ADSCs and did not exert any negative effects on stem cell properties. Magnetic targeting of ADSCs contributed to long-term cell retention in the corpus cavernosum and improved the erectile function of diabetic rats compared with ADSC injection alone. In addition, the paracrine effect of ADSCs appeared to play the major role in functional and structural recovery. Accordingly, magnetic field-guided ADSC therapy is an effective approach for diabetes-associated ED therapy.

Synthesis of a cell penetrating peptide modified superparamagnetic iron oxide and MRI detection of bladder cancer

Bladder cancer is the most common malignancy of the urinary tract for which the accurate measurement of minimal residual disease is critical to treatment and determining prognosis. Although cystoscope examination and voided urine cytology remain the current standard of care for detecting residual disease, these approaches are limited by mechanical trauma and lack sensitivity. To develop a new accurate noninvasive method, we developed a novel contrast agent where the surface of superparamagnetic iron oxide (SPIO) nanoparticles is functionalized with a bladder cancer-specific fluorescein isothiocyanate (FITC) labeled cell penetrating peptide (CPP)-polyarginine peptides (R11) for active targeting and imaging. The stable nanoparticles have an average hydrodynamic diameter of 51 nm, surface charge of -21 mV and MRI r₂ relaxivity 135 mM⁻¹s⁻¹. In vitro cell studies demonstrated that the R11-conjugated SPIO (SPIO-R11) nanoparticles were taken up by bladder cancer cells (T24) in a dose-dependent manner, which was higher than unconjugated SPIO. TEM showed that SPIO-R11 was mainly concentrated on cell vesicle and lysosome, not in cell nucleus, and no obvious damage was seen on cell ultrastructure. Moreover, uptake of the nanoparticles showed significantly more SPIO-R11 accumulation in bladder cancer cells than in immortalized bladder epithelial cells unlike control SPIO. Further, SPIO-R11 was compatible with immortalized bladder epithelial cells at all tested concentrations up to 200 μg/mL after 72 h incubation. Moreover, SPIO-R11 decreased the magnetic resonance T₂ relaxation time by 73% in tumors cells in vitro compared to 12% with SPIO. These results indicate great potential of SPIO-R11 as contrast agent to target bladder cancer for diagnostic and therapeutic applications.

Current Perspectives Regarding Stem Cell-Based Therapy for Liver Cirrhosis

Liver cirrhosis is a major cause of mortality and a common end of various progressive liver diseases. Since the effective treatment is currently limited to liver transplantation, stem cell-based therapy as an alternative has attracted interest due to promising results from preclinical and clinical studies. However, there is still much to be understood regarding the precise mechanisms of action. A number of stem cells from different origins have been employed for hepatic regeneration with different degrees of success. The present review presents a synopsis of stem cell research for the treatment of patients with liver cirrhosis according to the stem cell type. Clinical trials to date are summarized briefly. Finally, issues to be resolved and future perspectives are discussed with regard to clinical applications.

Stem cell tracking using effective self-assembled peptide-modified superparamagnetic nanoparticles

Peptide modified superparamagnetic iron oxide nanoparticles (SPIONs) have been developed as excellent magnetic resonance imaging (MRI) contrast agents for stem cell labeling and tracking due to their biocompatibility.

Preliminary Study of MR and Fluorescence Dual-mode Imaging: Combined Macrophage-Targeted and Superparamagnetic Polymeric Micelles

Purpose: To establish small-sized superparamagnetic polymeric micelles for magnetic resonance and fluorescent dual-modal imaging, we investigated the feasibility of MR imaging (MRI) and macrophage-targeted in vitro. Methods: A new class of superparamagnetic iron oxide nanoparticles (SPIONs) and Nile red-co-loaded mPEG-Lys3-CA4-NR/SPION polymeric micelles was synthesized to label Raw264.7 cells. The physical characteristics of the polymeric micelles were assessed, the T2 relaxation rate was calculated, and the effect of labeling on the cell viability and cytotoxicity was also determined in vitro. In addition, further evaluation of the application potential of the micelles was conducted via in vitro MRI. Results: The diameter of the mPEG-Lys3-CA4-NR/SPION polymeric micelles was 33.8 ± 5.8 nm on average. Compared with the hydrophilic SPIO, mPEG-Lys3-CA4-NR/SPION micelles increased transversely (r2), leading to a notably high r2 from 1.908 µg/mL-1S-1 up to 5.032 µg/mL-1S-1, making the mPEG-Lys3-CA4-NR/SPION micelles a highly sensitive MRI T2 contrast agent, as further demonstrated by in vitro MRI. The results of Confocal Laser Scanning Microscopy (CLSM) and Prussian blue staining of Raw264.7 after incubation with micelle-containing medium indicated that the cellular uptake efficiency is high. Conclusion: We successfully synthesized dual-modal MR and fluorescence imaging mPEG-Lys3-CA4-NR/SPION polymeric micelles with an ultra-small size and high MRI sensitivity, which were effectively and quickly uptaken into Raw 264.7 cells. mPEG-Lys3-CA4-NR/SPION polymeric micelles might become a new MR lymphography contrast agent, with high effectiveness and high MRI sensitivity.

Stem Cell Tracking Technologies for Neurological Regenerative Medicine Purposes

The growing field of stem cell therapy is moving toward clinical trials in a variety of applications, particularly for neurological diseases. However, this translation of cell therapies into humans has prompted a need to create innovative and breakthrough methods for stem cell tracing, to explore the migration routes and its reciprocity with microenvironment targets in the body, to monitor and track the outcome after stem cell transplantation therapy, and to track the distribution and cell viability of transplanted cells noninvasively and longitudinally. Recently, a larger number of cell tracking methods in vivo were developed and applied in animals and humans, including magnetic resonance imaging, nuclear medicine imaging, and optical imaging. This review has been intended to summarize the current use of those imaging tools in tracking stem cells, detailing their main features and drawbacks, including image resolution, tissue penetrating depth, and biosafety aspects. Finally, we address that multimodality imaging method will be a more potential tracking tool in the future clinical application.

Fabrication of Tissue-Engineered Bionic Urethra Using Cell Sheet Technology and Labeling By Ultrasmall Superparamagnetic Iron Oxide for Full-Thickness Urethral Reconstruction

Urethral strictures remain a reconstructive challenge, due to less than satisfactory outcomes and high incidence of stricture recurrence. An “ideal” urethral reconstruction should establish similar architecture and function as the original urethral wall. We fabricated a novel tissue-engineered bionic urethras using cell sheet technology and report their viability in a canine model. Small amounts of oral and adipose tissues were harvested, and adipose-derived stem cells, oral mucosal epithelial cells, and oral mucosal fibroblasts were isolated and used to prepare cell sheets. The cell sheets were hierarchically tubularized to form 3-layer tissue-engineered urethras and labeled by ultrasmall super-paramagnetic iron oxide (USPIO). The constructed tissue-engineered urethras were transplanted subcutaneously for 3 weeks to promote the revascularization and biomechanical strength of the implant. Then, 2 cm length of the tubularized penile urethra was replaced by tissue-engineered bionic urethra. At 3 months of urethral replacement, USPIO-labeled tissue-engineered bionic urethra can be effectively detected by MRI at the transplant site. Histologically, the retrieved bionic urethras still displayed 3 layers, including an epithelial layer, a fibrous layer, and a myoblast layer. Three weeks after subcutaneous transplantation, immunofluorescence analysis showed the density of blood vessels in bionic urethra was significantly increased following the initial establishment of the constructs and was further up-regulated at 3 months after urethral replacement and was close to normal level in urethral tissue. Our study is the first to experimentally demonstrate 3-layer tissue-engineered urethras can be established using cell sheet technology and can promote the regeneration of structural and functional urethras similar to normal urethra.

Choose your cell model wisely: The in vitro nanoneurotoxicity of differentially coated iron oxide nanoparticles for neural cell labeling

Currently, there is a large interest in the labeling of neural stem cells (NSCs) with iron oxide nanoparticles (IONPs) to allow MRI-guided detection after transplantation in regenerative medicine. For such biomedical applications, excluding nanotoxicity is key. Nanosafety is primarily evaluated in vitro where an immortalized or cancer cell line of murine origin is often applied, which is not necessarily an ideal cell model. Previous work revealed clear neurotoxic effects of PMA-coated IONPs in distinct cell types that could potentially be applied for nanosafety studies regarding neural cell labeling. Here, we aimed to assess if DMSA-coated IONPs could be regarded as a safer alternative for this purpose and how the cell model impacted our nanosafety optimization study. Hereto, we evaluated cytotoxicity, ROS production, calcium levels, mitochondrial homeostasis and cell morphology in six related neural cell types, namely neural stem cells, an immortalized cell line and a cancer cell line from human and murine origin. The cell lines mostly showed similar responses to both IONPs, which were frequently more pronounced for the PMA-IONPs. Of note, ROS and calcium levels showed opposite trends in the human and murine NSCs, indicating the importance of the species. Indeed, the human cell models were overall more sensitive than their murine counterpart. Despite the clear cell type-specific nanotoxicity profiles, our multiparametric approach revealed that the DMSA-IONPs outperformed the PMA-IONPs in terms of biocompatibility in each cell type. However, major cell type-dependent variations in the observed effects additionally warrant the use of relevant human cell models.

STATEMENT OF SIGNIFICANCE

Inorganic nanoparticle (NP) optimization is chiefly performed in vitro. For the optimization of iron oxide (IO)NPs for neural stem cell labeling in the context of regenerative medicine human or rodent neural stem cells, immortalized or cancer cell lines are applied. However, the use of certain cell models can be questioned as they phenotypically differ from the target cell. The impact of the neural cell model on nanosafety remains relatively unexplored. Here we evaluated cell homeostasis upon exposure to PMA- and DMSA-coated IONPs. Of note, the DMSA-IONPs outperformed the PMA-IONPs in each cell type. However, distinct cell type-specific effects were witnessed, indicating that nanosafety should be evaluated in a human cell model that represents the target cell as closely as possible.

Labeling adipose derived stem cell sheet by ultrasmall super-paramagnetic Fe3O4 nanoparticles and magnetic resonance tracking in vivo

Cell sheet therapy has emerged as a potential therapeutic option for reparation and reconstruction of damaged tissues and organs. However, an effective means to assess the fate and distribution of transplanted cell sheets in a serial and noninvasive manner is still lacking. To investigate the feasibility of tracking Adipose derived stem cells (ADSCs) sheet in vivo using ultrasmall super-paramagnetic Fe₃O₄ nanoparticles (USPIO), canine ADSCs were cultured and incubated with USPIO and 0.75 μg/ml Poly-L-Lysine (PLL) for 12 h. Labeling efficiency, cell viability, apoptotic cell rate were assessed to screen the optimum concentrations of USPIO for best labeling ADSCs. The results showed ADSCs were labeled by USPIO at an iron dose of 50 μg/ml for a 12 h incubation time, which can most efficiently mark cells and did not impair the cell survival, self-renewal, and proliferation capacity. USPIO-labeled ADSCs sheets can be easily and clearly detected in vivo and have persisted for at least 12 weeks. Our experiment confirmed USPIO was feasible for in vivo labeling of the ADSCs sheets with the optimal concentration of 50 μg Fe/ml and the tracing time is no less than 12 weeks.

Stem cells for ALS: An overview of possible therapeutic approaches

Amyotrophic lateral sclerosis (ALS) is an unusual, fatal, neurodegenerative disorder leading to the loss of motor neurons. After diagnosis, the average lifespan ranges from 3 to 5 years, and death usually results from respiratory failure. Although the pathogenesis of ALS remains unclear, multiple factors are thought to contribute to the progression of ALS, such as network interactions between genes, environmental exposure, impaired molecular pathways and many others. The neuroprotective properties of neural stem cells (NSCs) and the paracrine signaling of mesenchymal stem cells (MSCs) have been examined in multiple pre-clinical trials of ALS with promising results. The data from these initial trials indicate a reduction in the rate of disease progression. The mechanism through which stem cells achieve this reduction is of major interest. Here, we review the to-date pre-clinical and clinical therapeutic approaches employing stem cells, and discuss the most promising ones.

Lymphoma cell isolation using multifunctional magnetic nanoparticles: antibody conjugation and characterization

The early detection of B-cell lymphoma cells using multifunctional magnetic nanoparticles has a wide impact on the diagnosis of lymphoma patients.

The effect of magnetic nanoparticles on neuronal differentiation of induced pluripotent stem cell-derived neural precursors

Introduction

Magnetic resonance (MR) imaging is suitable for noninvasive long-term tracking. We labeled human induced pluripotent stem cell-derived neural precursors (iPSC-NPs) with two types of iron-based nanoparticles, silica-coated cobalt zinc ferrite nanoparticles (CZF) and poly-l-lysine-coated iron oxide superparamagnetic nanoparticles (PLL-coated γ-Fe₂O₃) and studied their effect on proliferation and neuronal differentiation.

Materials and methods

We investigated the effect of these two contrast agents on neural precursor cell proliferation and differentiation capability. We further defined the intracellular localization and labeling efficiency and analyzed labeled cells by MR.

Results

Cell proliferation was not affected by PLL-coated γ-Fe₂O₃ but was slowed down in cells labeled with CZF. Labeling efficiency, iron content and relaxation rates measured by MR were lower in cells labeled with CZF when compared to PLL-coated γ-Fe₂O₃. Cytoplasmic localization of both types of nanoparticles was confirmed by transmission electron microscopy. Flow cytometry and immunocytochemical analysis of specific markers expressed during neuronal differentiation did not show any significant differences between unlabeled cells or cells labeled with both magnetic nanoparticles.

Conclusion

Our results show that cells labeled with PLL-coated γ-Fe₂O₃ are suitable for MR detection, did not affect the differentiation potential of iPSC-NPs and are suitable for in vivo cell therapies in experimental models of central nervous system disorders.

Nanoengineering neural stem cells on biomimetic substrates using magnetofection technology

Tissue engineering studies are witnessing a major paradigm shift to cell culture on biomimetic materials that replicate native tissue features from which the cells are derived. Few studies have been performed in this regard for neural cells, particularly in nanomedicine. For example, platforms such as magnetic nanoparticles (MNPs) have proven efficient as multifunctional tools for cell tracking and genetic engineering of neural transplant populations. However, as far as we are aware, all current studies have been conducted using neural cells propagated on non-neuromimetic substrates that fail to represent the mechano-elastic properties of brain and spinal cord microenvironments. Accordingly, it can be predicted that such data is of less translational and physiological relevance than that derived from cells grown in neuromimetic environments. Therefore, we have performed the first test of magnetofection technology (enhancing MNP delivery using applied magnetic fields with significant potential for therapeutic application) and its utility in genetically engineering neural stem cells (NSCs; a population of high clinical relevance) propagated in biomimetic hydrogels. We demonstrate magnetic field application safely enhances MNP mediated transfection of NSCs grown as 3D spheroid structures in collagen which more closely replicates the intrinsic mechanical and structural properties of neural tissue than routinely used hard substrates. Further, as it is well known that MNP uptake is mediated by endocytosis we also investigated NSC membrane activity grown on both soft and hard substrates. Using high resolution scanning electron microscopy we were able to prove that NSCs display lower levels of membrane activity on soft substrates compared to hard, a finding which could have particular impact on MNP mediated engineering strategies of cells propagated in physiologically relevant systems.

Ferumoxytol Labeling of Human Neural Progenitor Cells for Diagnostic Cellular Tracking in the Porcine Spinal Cord with Magnetic Resonance Imaging

We report on the diagnostic capability of magnetic resonance imaging (MRI)‐based tracking of ferumoxytol‐labeled human neural progenitor cells (hNPCs) transplanted into the porcine spinal cord. hNPCs prelabeled with two doses of ferumoxytol nanoparticles (hNPC‐F^Low and hNPC‐F^High) were injected into the ventral horn of the spinal cord in healthy minipigs. Ferumoxytol‐labeled grafts were tracked in vivo up to 105 days after transplantation with MRI. Injection accuracy was assessed in vivo at day 14 and was predictive of “on” or “off” target cell graft location assessed by histology. No difference in long‐term cell survival, assessed by quantitative stereology, was observed among hNPC‐F^Low, hNPC‐F^High, or control grafts. Histological iron colocalized with MRI signal and engrafted human nuclei. Furthermore, the ferumoxytol‐labeled cells retained nanoparticles and function in vivo. This approach represents an important leap forward toward facilitating translation of cell‐tracking technologies to clinical trials by providing a method of assessing transplantation accuracy, delivered dose, and potentially cell survival. Stem Cells Translational Medicine2017;6:139–150

Synthesis of tumor-targeted folate conjugated fluorescent magnetic albumin nanoparticles for enhanced intracellular dual-modal imaging into human brain tumor cells

Superparamagnetic iron oxide nanoparticles (SPIO NPs), utilized as carriers are attractive materials widely applied in biomedical fields, but target-specific SPIO NPs with lower toxicity and excellent biocompatibility are still lacking for intracellular visualization in human brain tumor diagnosis and therapy. Herein, bovine serum albumin (BSA) coated superparamagnetic iron oxide, i.e. γ-Fe2O3 nanoparticles (BSA-SPIO NPs), are synthesized. Tumor-specific ligand folic acid (FA) is then conjugated onto BSA-SPIO NPs to fabricate tumor-targeted NPs, FA-BSA-SPIO NPs as a contrast agent for MRI imaging. The FA-BSA-SPIO NPs are also labeled with fluorescein isothiocyanate (FITC) for intracellular visualization after cellular uptake and internalization by glioma U251 cells. The biological effects of the FA-BSA-SPIO NPs are investigated in human brain tumor U251 cells in detail. These results show that the prepared FA-BSA-SPIO NPs display undetectable cytotoxicity, excellent biocompatibility, and potent cellular uptake. Moreover, the study shows that the made FA-BSA-SPIO NPs are effectively internalized for MRI imaging and intracellular visualization after FITC labeling in the targeted U251 cells. Therefore, the present study demonstrates that the fabricated FITC-FA-BSA-SPIO NPs hold promising perspectives by providing a dual-modal imaging as non-toxic and target-specific vehicles in human brain tumor treatment in future.

Magnetic resonance imaging of ultrasmall superparamagnetic iron oxide-labeled exosomes from stem cells: a new method to obtain labeled exosomes

PURPOSE

Recent findings indicate that the beneficial effects of adipose stem cells (ASCs), reported in several neurodegenerative experimental models, could be due to their paracrine activity mediated by the release of exosomes. The aim of this study was the development and validation of an innovative exosome-labeling protocol that allows to visualize them with magnetic resonance imaging (MRI).

MATERIALS AND METHODS

At first, ASCs were labeled using ultrasmall superparamagnetic iron oxide nanoparticles (USPIO, 4-6 nm), and optimal parameters to label ASCs in terms of cell viability, labeling efficiency, iron content, and magnetic resonance (MR) image contrast were investigated. Exosomes were then isolated from labeled ASCs using a standard isolation protocol. The efficiency of exosome labeling was assessed by acquiring MR images in vitro and in vivo as well as by determining their iron content. Transmission electron microscopy images and histological analysis were performed to validate the results obtained.

RESULTS

By using optimized experimental parameters for ASC labeling (200 µg Fe/mL of USPIO and 72 hours of incubation), it was possible to label 100% of the cells, while their viability remained comparable to unlabeled cells; the detection limit of MR images was of 10(2) and 2.5×10(3) ASCs in vitro and in vivo, respectively. Exosomes isolated from previously labeled ASCs retain nanoparticles, as demonstrated by transmission electron microscopy images. The detection limit by MRI was 3 µg and 5 µg of exosomes in vitro and in vivo, respectively.

CONCLUSION

We report a new approach for labeling of exosomes by USPIO that allows detection by MRI while preserving their morphology and physiological characteristics.

SIRB, sans iron oxide rhodamine B, a novel cross-linked dextran nanoparticle, labels human neuroprogenitor and SH-SY5Y neuroblastoma cells and serves as a USPIO cell labeling control

This is the first report of the synthesis of a new nanoparticle, sans iron oxide rhodamine B (SIRB), an example of a new class of nanoparticles. SIRB is designed to provide all of the cell labeling properties of the ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle Molday ION Rhodamine B (MIRB) without containing the iron oxide core. MIRB was developed to label cells and allow them to be tracked by MRI or to be manipulated by magnetic gradients. SIRB possesses a similar size, charge and cross-linked dextran coating as MIRB. Of great interest is understanding the biological and physiological changes in cells after they are labeled with a USPIO. Whether these effects are due to the iron oxide buried within the nanoparticle or to the surface coating surrounding the iron oxide core has not been considered previously. MIRB and SIRB represent an ideal pairing of nanoparticles to identify nanoparticle anatomy responsible for post-labeling cytotoxicity. Here we report the effects of SIRB labeling on the SH-SY5Y neuroblastoma cell line and primary human neuroprogenitor cells (hNPCs). These effects are contrasted with the effects of labeling SH-SY5Y cells and hNPCs with MIRB. We find that SIRB labeling, like MIRB labeling, (i) occurs without the use of transfection reagents, (ii) is packaged within lysosomes distributed within cell cytoplasm, (iii) is retained within cells with no loss of label after cell storage, and (iv) does not alter cellular viability or proliferation, and (v) SIRB labeled hNPCs differentiate normally into neurons or astrocytes. Copyright © 2016 John Wiley & Sons, Ltd.

Intracoronary Transplantation of Mesenchymal Stem Cells with Overexpressed Integrin-Linked Kinase Improves Cardiac Function in Porcine Myocardial Infarction

The effect of mesenchymal stem cell (MSCs)-based therapy on treating acute myocardial infarction (MI) is limited due to poor engraftment and limited regenerative potential. Here we engineered MSCs with integrin-linked kinase (ILK), a pleiotropic protein critically regulating cell survival, proliferation, differentiation, and angiogenesis. We firstly combined ferumoxytol with poly-L-lysine (PLL), and found this combination promisingly enabled MRI visualization of MSCs in vitro and in vivo with good safety. We provided visually direct evidence that intracoronary ILK-MSCs had substantially enhanced homing capacity to infarct myocardium in porcine following cardiac catheterization induced MI. Intracoronary transplantation of allogeneic ILK-MSCs, but not vector-MSCs, significantly enhanced global left ventricular ejection fraction (LVEF) by 7.8% compared with baseline, by 10.3% compared with vehicles, and inhibited myocardial remodeling compared with vehicles at 15-day follow-up. Compared with vector-MSCs, ILK-MSCs significantly improved regional LV contractile function, reduced scar size, fibrosis, cell apoptosis, and increased regional myocardial perfusion and cell proliferation. This preclinical study indicates that ILK-engineered MSCs might promote the clinical translation of MSC-based therapy in post-MI patients, and provides evidence that ferumoxytol labeling of cells combined with PLL is feasible in in vivo cell tracking.

Fe2O3 nanoparticles suppress Kv1.3 channels via affecting the redox activity of Kvβ2 subunit in Jurkat T cells

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising nanomaterials in medical practice due to their special magnetic characteristics and nanoscale size. However, their potential impacts on immune cells are not well documented. This study aims to investigate the effects of Fe2O3 nanoparticles (Fe2O3-NPs) on the electrophysiology of Kv1.3 channels in Jurkat T cells. Using the whole-cell patch-clamp technique, we demonstrate that incubation of Jurkat cells with Fe2O3-NPs dose- and time-dependently decreased the current density and shifted the steady-state inactivation curve and the recovery curve of Kv1.3 channels to a rightward direction. Fe2O3-NPs increased the NADP level but decreased the NADPH level of Jurkat cells. Direct induction of NADPH into the cytosole of Jurkat cells via the pipette abolished the rightward shift of the inactivation curve. In addition, transmission electron microscopy showed that Fe2O3-NPs could be endocytosed by Jurkat cells with relatively low speed and capacity. Fe2O3-NPs did not significantly affect the viability of Jurkat cells, but suppressed the expressions of certain cytokines (TNFα, IFNγ and IL-2) and interferon responsive genes (IRF-1 and PIM-1), and the time courses of Fe2O3-NPs endocytosis and effects on the expressions of cytokines and interferon responsive genes were compatible. We conclude that Fe2O3-NPs can be endocytosed by Jurkat cells and act intracellularly. Fe2O3-NPs decrease the current density and delay the inactivation and recovery kinetics of Kv1.3 channels in Jurkat cells by oxidizing NADPH and therefore disrupting the redox activity of the Kvβ2 auxiliary subunit, and as a result, lead to changes of the Kv1.3 channel function. These results suggest that iron oxide nanoparticles may affect T cell function by disturbing the activity of Kv1.3 channels. Further, the suppressing effects of Fe2O3-NPs on the expressions of certain inflammatory cytokines and interferon responsive genes suggest that iron oxide nanoparticles may exert modulatory effects on T cell immune activities and anti-inflammation effects.

Mesenchymal stem cell therapy for cirrhosis: Present and future perspectives

Cirrhosis occurs as a result of various chronic liver injuries, which may be caused by viral infections, alcohol abuse and the administration of drugs and chemicals. Recently, bone marrow cells (BMCs), hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) have been used for developing treatments for cirrhosis. Clinical trials have investigated the therapeutic potential of BMCs, HSCs and MSCs for the treatment of cirrhosis based on their potential to differentiate into hepatocytes. Although the therapeutic mechanisms of BMC, HSC and MSC treatments are still not fully characterized, the evidence thus far has indicated that the potential therapeutic mechanisms of MSCs are clearer than those of BMCs or HSCs with respect to liver regenerative medicine. MSCs suppress inflammatory responses, reduce hepatocyte apoptosis, increase hepatocyte regeneration, reverse liver fibrosis and enhance liver functionality. This paper summarizes the clinical studies that have used BMCs, HSCs and MSCs in patients with liver failure or cirrhosis. We also present the potential therapeutic mechanisms of BMCs, HSCs and MSCs for the improvement of liver function.

Mesenchymal stem cell therapy for liver fibrosis

Currently, the most effective treatment for end-stage liver fibrosis is liver transplantation; however, transplantation is limited by a shortage of donor organs, surgical complications, immunological rejection, and high medical costs. Recently, mesenchymal stem cell (MSC) therapy has been suggested as an effective alternate approach for the treatment of hepatic diseases. MSCs have the potential to differentiate into hepatocytes, and therapeutic value exists in their immune-modulatory properties and secretion of trophic factors, such as growth factors and cytokines. In addition, MSCs can suppress inflammatory responses, reduce hepatocyte apoptosis, increase hepatocyte regeneration, regress liver fibrosis and enhance liver functionality. Despite these advantages, issues remain; MSCs also have fibrogenic potential and the capacity to promote tumor cell growth and oncogenicity. This paper summarizes the properties of MSCs for regenerative medicine and their therapeutic mechanisms and clinical application in the treatment of liver fibrosis. We also present several outstanding risks, including their fibrogenic potential and their capacity to promote pre-existing tumor cell growth and oncogenicity.

Novel bimodal iron oxide particles for efficient tracking of human neural stem cells in vivo

AIMS

We validated novel bimodal iron oxide particles as substitute of ferumoxides for efficient labeling of human neural stem cells (NSCs). The dextrane-coated FeraTrack Direct (FTD)-Vio particles have additional far-red fluorophores for microscopic cell analysis.

METHODS

MR relaxometry, spectrophotometric iron determination and microscopy are used for characterization in vitro and in vivo.

RESULTS

Efficient uptake is not transfection agent-dependent. FTD-Vio594 labeling had no influence on viability, proliferation, migration and differentiation capacity. It allows MRI-based tracking of engrafted NSCs in mouse brain up to 11 days, complemented by bioluminescence imaging of firefly luciferase expressed by the engrafted cells.

CONCLUSION

Our results highlight the FTD-Vio594 particles as safe and sensitive substitute of ferumoxides for longitudinal tracking of NSCs in preclinical studies.

In Vivo Tracking of Human Neural Progenitor Cells in the Rat Brain Using Magnetic Resonance Imaging Is Not Enhanced by Ferritin Expression

Rapid growth in the field of stem cell research has generated a lot of interest in their therapeutic use, especially in the treatment of neurodegenerative diseases. Specifically, human neural progenitor cells (hNPCs), unique in their capability to differentiate into cells of the neural lineage, have been widely investigated due to their ability to survive, thrive, and migrate toward injured tissues. Still, one of the major roadblocks for clinical applicability arises from the inability to monitor these cells following transplantation. Molecular imaging techniques, such as magnetic resonance imaging (MRI), have been explored to assess hNPC transplant location, migration, and survival. Here we investigated whether inducing hNPCs to overexpress ferritin (hNPCs(Fer)), an iron storage protein, is sufficient to track these cells long term in the rat striatum using MRI. We found that increased hypointensity on MRI images could establish hNPC(Fer) location. Unexpectedly, however, wild-type hNPC transplants were detected in a similar manner, which is likely due to increased iron accumulation following transplantation-induced damage. Hence, we labeled hNPCs with superparamagnetic iron oxide (SPIO) nanoparticles to further increase iron content in an attempt to enhance cell contrast in MRI. SPIO-labeling of hNPCs (hNPCs-SPIO) achieved increased hypointensity, with significantly greater area of decreased T2* compared to hNPC(Fer) (p < 0.0001) and all other controls used. However, none of the techniques could be used to determine graft rejection in vivo, which is imperative for understanding cell behavior following transplantation. We conclude that in order for cell survival to be monitored in preclinical and clinical settings, another molecular imaging technique must be employed, including perhaps multimodal imaging, which would utilize MRI along with another imaging modality.

Superparamagnetic iron oxide nanoparticles for in vivo molecular and cellular imaging

In the last decade, the biomedical applications of nanoparticles (NPs) (e.g. cell tracking, biosensing, magnetic resonance imaging (MRI), targeted drug delivery, and tissue engineering) have been increasingly developed. Among the various NP types, superparamagnetic iron oxide NPs (SPIONs) have attracted considerable attention for early detection of diseases due to their specific physicochemical properties and their molecular imaging capabilities. A comprehensive review is presented on the recent advances in the development of in vitro and in vivo SPION applications for molecular imaging, along with opportunities and challenges.

Biological characteristics of adipose tissue-derived stem cells labeled with amine-surface-modified superparamagnetic iron oxide nanoparticles

Cell labeling and tracking are becoming increasingly important areas within the field of stem cell transplantation. The ability to track the migration and distribution of implanted cells is critical to understanding the beneficial effects and mechanisms of stem cell therapy. The present study investigated the effects of amine-surface-modified superparamagnetic iron oxide (SPIO) nanoparticles on the biological properties of human adipose tissue-derived stem cells (hADSCs). Monodisperse hydrophobic magnetite (Fe3 O4 ) nanoparticles were prepared using silicon and surface-modified with amine coating. Cell viability, proliferation, differentiation potential, and surface marker expression were evaluated. The magnetic particles (10-18 nm) displayed high labeling efficiency and stability in hADSCs. SPIO-labeled cells produced a hypointense signal and were effectively visualized by MRI for up to 21 days. The results of MTT proliferation assays and flow cytometry analysis demonstrated that SPIOs were biocompatible, viz. the labeling process did not cause cell death or apoptosis and had no side effects on cell proliferation. In vivo experiments showed that the magnetic particles did not affect liver and kidney function. The successful and stable labeling of hADSCs combined with efficient magnetic tropism demonstrates that SPIOs are promising candidates for hADSC tracking in hADSC-based cell therapy applications.

Optimization of the magnetic labeling of human neural stem cells and MRI visualization in the hemiparkinsonian rat brain

BACKGROUND

Magnetic resonance imaging is the ideal modality for non-invasive in vivo cell tracking allowing for longitudinal studies over time. Cells labeled with superparamagnetic iron oxide nanoparticles have been shown to induce sufficient contrast for in vivo magnetic resonance imaging enabling the in vivo analysis of the final location of the transplanted cells. For magnetic nanoparticles to be useful, a high internalization efficiency of the particles is required without compromising cell function, as well as validation of the magnetic nanoparticles behaviour inside the cells.

RESULTS

In this work, we report the development, optimization and validation of an efficient procedure to label human neural stem cells with commercial nanoparticles in the absence of transfection agents. Magnetic nanoparticles used here do not affect cell viability, cell morphology, cell differentiation or cell cycle dynamics. Moreover, human neural stem cells progeny labeled with magnetic nanoparticles are easily and non-invasively detected long time after transplantation in a rat model of Parkinson's disease (up to 5 months post-grafting) by magnetic resonance imaging.

CONCLUSIONS

These findings support the use of commercial MNPs to track cells for short- and mid-term periods after transplantation for studies of brain cell replacement therapy. Nevertheless, long-term MR images should be interpreted with caution due to the possibility that some MNPs may be expelled from the transplanted cells and internalized by host microglial cells.

Noninvasive MRI and multilineage differentiation capability of ferritin-transduced human mesenchymal stem cells

Molecular imaging can be a breakthrough tool for the investigation of the behavior and ultimate feasibility of transplanted human mesenchymal stem cells (hMSCs) inside the body, and for the development of guidelines and recommendations based on the treatment and evaluation of stem cell therapy for patients. The goals of this study were to evaluate the multilineage differentiation ability of hMSCs expressing an MRI reporter, human ferritin heavy chain (FTH) and to investigate the feasibility of using FTH-based MRI to provide noninvasive imaging of transplanted hMSCs. The transduction of FTH and green fluorescence protein (GFP) did not influence the expression of the mesenchymal stem cell surface markers (CD29+/CD105+/CD34-/CD45-) or the self-renewal marker genes [octamer-binding transcription factor 4 (OCT-4) and SRY (sex determining region Y)-box 2 (Sox-2)], cell viability, migration ability and the release of cytokines [interleukin-5 (IL-5), IL-10, IL-12p70, tumor necrosis factor-α (TNF-α)]. FTH-hMSCs retained the capacity to differentiate into adipogenic, chondrogenic, osteogenic and neurogenic lineages. The transduction of FTH led to a significant enhancement in cellular iron storage capacity and caused hypointensity and a significant increase in R2 * values of FTH-hMSC-collected phantoms and FTH-hMSC-transplanted sites of the brain, as shown by in vitro and in vivo MRI performed at 9.4 T, compared with control hMSCs. This study revealed no differences in biological characteristics between hMSCs and FTH-hMSCs and, therefore, these cells could be used for noninvasive monitoring with MRI during stem cell therapy for brain injury. Our study suggests the use of FTH for in vivo long-term tracking and ultimate fate of hMSCs without alteration of their characteristics and multidifferentiation potential.

Cryopreservation of embryonic stem cell-derived multicellular neural aggregates labeled with micron-sized particles of iron oxide for magnetic resonance imaging

Magnetic resonance imaging (MRI) provides an effective approach to track labeled pluripotent stem cell (PSC)-derived neural progenitor cells (NPCs) for neurological disorder treatments after cell labeling with a contrast agent, such as an iron oxide derivative. Cryopreservation of pre-labeled neural cells, especially in three-dimensional (3D) structure, can provide a uniform cell population and preserve the stem cell niche for the subsequent applications. In this study, the effects of cryopreservation on PSC-derived multicellular NPC aggregates labeled with micron-sized particles of iron oxide (MPIO) were investigated. These NPC aggregates were labeled prior to cryopreservation because labeling thawed cells can be limited by inefficient intracellular uptake, variations in labeling efficiency, and increased culture time before use, minimizing their translation to clinical settings. The results indicated that intracellular MPIO incorporation was retained after cryopreservation (70-80% labeling efficiency), and MPIO labeling had little adverse effects on cell recovery, proliferation, cytotoxicity and neural lineage commitment post-cryopreservation. MRI analysis showed comparable detectability for the MPIO-labeled cells before and after cryopreservation indicated by T2 and T2* relaxation rates. Cryopreserving MPIO-labeled 3D multicellular NPC aggregates can be applied in in vivo cell tracking studies and lead to more rapid translation from preservation to clinical implementation.

Deploying clinical grade magnetic nanoparticles with magnetic fields to magnetolabel neural stem cells in adherent versus suspension cultures

This is the first demonstration that oscillating magnetic fields safely promote the uptake of a clinical-grade magnetic nanoparticle (Lumirem/Ferumoxsil) into neural stem cells for non-invasive cell tracking capabilities.

Highly Efficient Labeling of Human Lung Cancer Cells Using Cationic Poly-l-lysine-Assisted Magnetic Iron Oxide Nanoparticles

Cell labeling with magnetic iron oxide nanoparticles (IONPs) is increasingly a routine approach in the cell-based cancer treatment. However, cell labeling with magnetic IONPs and their leading effects on the biological properties of human lung carcinoma cells remain scarcely reported. Therefore, in the present study the magnetic γ-Fe₂O₃ nanoparticles (MNPs) were firstly synthesized and surface-modified with cationic poly-l-lysine (PLL) to construct the PLL-MNPs, which were then used to magnetically label human A549 lung cancer cells. Cell viability and proliferation were evaluated with propidium iodide/fluorescein diacetate double staining and standard 3-(4,5-dimethylthiazol-2-diphenyl-tetrazolium) bromide assay, and the cytoskeleton was immunocytochemically stained. The cell cycle of the PLL-MNP-labeled A549 lung cancer cells was analyzed using flow cytometry. Apoptotic cells were fluorescently analyzed with nuclear-specific staining after the PLL-MNP labeling. The results showed that the constructed PLL-MNPs efficiently magnetically labeled A549 lung cancer cells and that, at low concentrations, labeling did not affect cellular viability, proliferation capability, cell cycle, and apoptosis. Furthermore, the cytoskeleton in the treated cells was detected intact in comparison with the untreated counterparts. However, the results also showed that at high concentration (400 µg mL^-1), the PLL-MNPs would slightly impair cell viability, proliferation, cell cycle, and apoptosis and disrupt the cytoskeleton in the treated A549 lung cancer cells. Therefore, the present results indicated that the PLL-MNPs at adequate concentrations can be efficiently used for labeling A549 lung cancer cells and could be considered as a feasible approach for magnetic targeted anti-cancer drug/gene delivery, targeted diagnosis, and therapy in lung cancer treatment.

Concise review: Stem cell therapies for amyotrophic lateral sclerosis: recent advances and prospects for the future

Amyotrophic lateral sclerosis (ALS) is a lethal disease involving the loss of motor neurons. Although the mechanisms responsible for motor neuron degeneration in ALS remain elusive, the development of stem cell-based therapies for the treatment of ALS has gained widespread support. Here, we review the types of stem cells being considered for therapeutic applications in ALS, and emphasize recent preclinical advances that provide supportive rationale for clinical translation. We also discuss early trials from around the world translating cellular therapies to ALS patients, and offer important considerations for future clinical trial design. Although clinical translation is still in its infancy, and additional insight into the mechanisms underlying therapeutic efficacy and the establishment of long-term safety are required, these studies represent an important first step toward the development of effective cellular therapies for the treatment of ALS.