In vivo tracking of superparamagnetic iron oxide nanoparticle–labeled mesenchymal stem cell tropism to malignant gliomas using magnetic resonance imaging

Active Hydrophilic Graphene Oxide Nanocomposites Delivery Mediated by Adipose-Derived Stem Cell for Elevated Photothermal Therapy of Breast Cancer

Purpose

Graphene oxide (GO) and its derivatives have recently been identified as promising candidates for early disease diagnosis and therapy. However, the physiological stability and precise launch requirements present limitations on further clinical practices. Adipose-derived stem cells (ADSCs) were employed as an unobstructed biological vehicle to address the validate this ADSC-based tumor-targeting system for highly efficient GO delivery combined with two-stage NIR radiation for superior tumor ablation.

Methods

GO was modified with poly-ethylene glycol (PEG) and folic acid (FA). Afterward, the GO nanocomposite was internalized into ADSCs. The GO-PEG-FA-laden ADSCs were injected into the tail veins of the tumor-bearing mice. Subsequently, first-stage NIR radiation was utilized to disrupt the ADSCs for GO-PEG-FA release. After this, the heat generated by secondary-stage NIR radiation destroy the malignant cells and shrink the tumor, and the cascade process could be recycled until complete tumor ablation if necessary.

Results

The GO-PEG-FA nanocomposite exhibited negligible cytotoxicity and could be internalized into ADSCs to target specific tumor sites after 32 days of intravenous injection. The nanocomposite was released from the ADSCs and taken up into cancer cells again with the assistance of FA after the first dose of near-infrared radiation. Then, the second radiation dose could directly strike the cancer cell for cancer ablation.

Conclusion

In summary, we reported a stem cell-based anticancer system that used GO-PEG-FA-laden ADSCs for breast cancer therapy through NIR treatment in mice potentially opens a new avenue not only to address precise drug targeting in tumor therapy, but also future clinical practice in diverse areas.

Mesenchymal Stem/Stromal Cells as a Vehicle for Cytokine Delivery: An Emerging Approach for Tumor Immunotherapy

Pro-inflammatory cytokines can effectively be used for tumor immunotherapy, affecting every step of the tumor immunity cycle. Thereby, they can restore antigen priming, improve the effector immune cell frequencies in the tumor microenvironment (TME), and eventually strengthen their cytolytic function. A renewed interest in the anticancer competencies of cytokines has resulted in a substantial promotion in the number of trials to address the safety and efficacy of cytokine-based therapeutic options. However, low response rate along with the high toxicity associated with high-dose cytokine for reaching desired therapeutic outcomes negatively affect their clinical utility. Recently, mesenchymal stem/stromal cells (MSCs) due to their pronounced tropism to tumors and also lower immunogenicity have become a promising vehicle for cytokine delivery for human malignancies. MSC-based delivery of the cytokine can lead to the more effective immune cell-induced antitumor response and provide sustained release of target cytokines, as widely evidenced in a myriad of xenograft models. In the current review, we offer a summary of the novel trends in cytokine immunotherapy using MSCs as a potent and encouraging carrier for antitumor cytokines, focusing on the last two decades' animal reports.

Recent advances in iron oxide nanoparticles for brain cancer theranostics: from in vitro to clinical applications

Introduction: Today, the development of multifunctional nanoplatforms is more seriously considered in the field of cancer theranostics.Areas covered: In this respect, nanoparticles provide several advantages over the routine, conventional diagnostic methods, and treatments. Due to the expedient properties of iron oxide nanoparticles, such as being readily modified, great payload potential, intrinsic magnetic qualification, considerable biocompatibility, and overwhelming response to targeting strategies, these nanoparticles can be considered good candidates for application as diagnostic contrast agents and drug/gene delivery vehicles, while also being incorporated into hyperthermia-based approaches. Interestingly, these agents are detectable with routine imaging modalities such as magnetic resonance imaging.Expert opinion: Therefore, combining the traditional diagnostics and therapies with nanotechnological approaches may leave a positive impact on the survival rate of patients with cancer. This review summarizes the application of magnetic iron oxide nanoparticles in both in vitro and in vivo models of brain tumors.

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.

Reversibility of hAT-MSCs phenotypic and metabolic changes after exposure to and withdrawal from HCC-conditioned medium through regulation of the ROS/MAPK/HIF-1α signaling pathway

Background

Mesenchymal stem cells (MSCs) play an important role in tumor progression; concomitantly, MSCs also undergo profound changes in the tumor microenvironment (TME). These changes can directly impact the application and efficacy of MSC-based anti-tumor therapy. However, few studies have focused on the regulation of MSC fate in TME, which will limit the progress of MSC-based anti-tumor therapy. Herein, we investigated the effects of conditioned medium from human hepatocellular carcinoma cells (HCC-CM) on the phenotype and glucose metabolism of human adipose tissue-derived MSCs (hAT-MSCs).

Methods

The passage 2 (P2) to passage 3 (P3) hAT-MSCs were exposed to conditioned medium from Hep3B, Huh7 and HCCLM3 cells for 4–8 weeks in vitro. Then, immunofluorescent, CCK-8 assay, EdU assay, Transwell assay, and flow cytometry were used to assess the alterations in cell phenotype in terms of cell morphology, secretory profiles, proliferation, migration, invasion, cell cycle, and apoptosis. In addition, glucose metabolism was evaluated by related kits. Next, the treated hAT-MSCs were subjected to withdrawal from HCC-CM for 2–4 weeks, and alterations in phenotype and glucose metabolism were reevaluated. Finally, the molecular mechanism was clarified by Western blotting.

Results

The results revealed that after exposure to HCC-CM, hAT-MSCs developed a stellate-shaped morphology. In association with cytoskeleton remodeling, hAT-MSCs showed enhanced capacities for migration and invasion, while cell proliferation was inhibited by regulating the cell cycle by downregulating cyclins and cyclin-dependent kinases and activating the mitochondrial apoptosis pathway. In terms of glucose metabolism, our results showed mitochondrial dysfunction and elevated glycolysis of hAT-MSCs. However, interestingly, when the treated hAT-MSCs were subjected to withdrawal from HCC-CM, the alterations in phenotype and glucose metabolism could be reversed, but secretory phenotype and tumor-promoting properties appear to be permanent. Further studies showed that these changes in hAT-MSCs may be regulated by the ROS/MAPK/HIF-1α signaling pathway.

Conclusion

Taken together, the effects of long-term HCC-CM treatment on phenotype and glucose metabolism in hAT-MSCs are modest and largely reversible after withdrawal, but HCC-CM endow hAT-MSCs with permanent secretory phenotype and tumor-promoting properties. This is the first report on the reversal of phenotype and glucose metabolism in tumor-associated MSCs (TA-MSCs), it is anticipated that new insights into TA-MSCs will lead to the development of novel strategies for MSC-based anti-tumor therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02010-0.

Assessment of Cellular Uptake Efficiency According to Multiple Inhibitors of Fe3O4-Au Core-Shell Nanoparticles: Possibility to Control Specific Endocytosis in Colorectal Cancer Cells

Magnetite (Fe₃O₄)-gold (Au) core-shell nanoparticles (NPs) have unique magnetic and optical properties. When combined with biological moieties, these NPs can offer new strategies for biomedical applications, such as drug delivery and cancer targeting. Here, we present an effective method for the controllable cellular uptake of magnetic core-shell NP systems combined with biological moieties. Vimentin, which is the structural protein, has been biochemically confirmed to affect phagocytosis potently. In addition, vimentin affects exogenic materials internalization into cells even though under multiple inhibitions of biological moieties. In this study, we demonstrate the cellular internalization performance of Fe₃O₄-Au core-shell NPs with surface modification using a combination of biological moieties. The photofluorescence of vimentin-tagged NPs remained unaffected under multiple inhibition tests, indicating that the NPs were minimally influenced by nystatin, dynasore, cytochalasin D, and even the Muc1 antibody (Ab). Consequently, this result indicates that the Muc1 Ab can target specific molecules and can control specific endocytosis. Besides, we show the possibility of controlling specific endocytosis in colorectal cancer cells.

Cell-Based Nanoparticles Delivery Systems for Targeted Cancer Therapy: Lessons from Anti-Angiogenesis Treatments

The main strategy of cancer treatment has focused on attacking the tumor cells. Some cancers initially responsive to chemotherapy become treatment-resistant. Another strategy is to block the formation of tumor vessels. However, tumors also become resistant to anti-angiogenic treatments, mostly due to other cells and factors present in the tumor microenvironment, and hypoxia in the central part of the tumor. The need for new cancer therapies is significant. The use of nanoparticle-based therapy will improve therapeutic efficacy and targeting, while reducing toxicity. However, due to inefficient accumulation in tumor sites, clearance by reticuloendothelial organs and toxicity, internalization or conjugation of drug-loaded nanoparticles (NPs) into mesenchymal stem cells (MSCs) can increase efficacy by actively delivering them into the tumor microenvironment. Nanoengineering MSCs with drug-loaded NPs can increase the drug payload delivered to tumor sites due to the migratory and homing abilities of MSCs. However, MSCs have some disadvantages, and exosomes and membranes from different cell types can be used to transport drug-loaded NPs actively to tumors. This review gives an overview of different cancer approaches, with a focus on hypoxia and the emergence of NPs as drug-delivery systems and MSCs as cellular vehicles for targeted delivery due to their tumor-homing potential.

Seeing Better and Going Deeper in Cancer Nanotheranostics

Biomedical imaging modalities in clinical practice have revolutionized oncology for several decades. State-of-the-art biomedical techniques allow visualizing both normal physiological and pathological architectures of the human body. The use of nanoparticles (NP) as contrast agents enabled visualization of refined contrast images with superior resolution, which assists clinicians in more accurate diagnoses and in planning appropriate therapy. These desirable features are due to the ability of NPs to carry high payloads (contrast agents or drugs), increased in vivo half-life, and disease-specific accumulation. We review the various NP-based interventions for treatments of deep-seated tumors, involving "seeing better" to precisely visualize early diagnosis and "going deeper" to activate selective therapeutics in situ.

Mesenchymal stem cell-mediated delivery of therapeutic adenoviral vectors to prostate cancer

Background

There is an urgent need for targeted biological therapies for prostate cancer with greater efficacy and less toxicity, particularly for metastatic disease, where current therapies are not curative. Therapeutic adenoviral vectors or oncolytic adenoviruses offer the possibility of a competent, nontoxic therapeutic alternative for prostate cancer. However, free viral particles must be delivered locally, an approach that does not address metastatic disease, and they display poor tumor penetration. To fully exploit the potential of these vectors, we must develop methods that improve intratumoral dissemination and allow for systemic delivery. This study establishes a proof-of-principle rationale for a novel human mesenchymal stem (stromal) cell-based approach to improving vector delivery to tumors.

Methods/results

We have generated mesenchymal stem cell-derived packaging cells for adenoviruses (E1-modified mesenchymal stem cells) by modifying human mesenchymal stem cells with the adenovirus (type C) E1A/B genes needed for viral replication. Using cell-based assays, we have demonstrated that two adenoviral vectors, replication-defective adenovirus expressing p14 and p53 or conditionally replicating oncolytic adenovirus, packaged by E1A/B-modified mesenchymal stem cells, suppress the growth of prostate cancer cells in culture. Using subcutaneous xenograft models for human prostate cancer in mice, we have shown that E1A/B-modified mesenchymal stem cells display tumor tropism in tumor-bearing nude mice, that E1A/B-modified mesenchymal stem cells disseminate well within tumors, and that replication-defective adenovirus expressing p14 and p53 or conditionally replicating oncolytic adenovirus-loaded E1-modified mesenchymal stem cells suppresses tumor growth in mice.

Conclusion

The results show that this approach, if optimized, could circumvent the obstacles to efficient gene delivery encountered with current gene delivery approaches and provide an effective, nontoxic therapeutic alternative for metastatic disease.

Pre-clinical Models for Studying the Interaction Between Mesenchymal Stromal Cells and Cancer Cells and the Induction of Stemness

Mesenchymal stromal cells (MSC) have essential functions in building and supporting the tumour microenvironment, providing metastatic niches, and maintaining cancer hallmarks, and it is increasingly evident that the study of the role of MSC in cancer is crucial for paving the way to clinical opportunities for novel anti-cancer therapies. To date, the vast majority of preclinical models that have been used for studying the effect of reactive MSC on cancer growth, metastasis, and response to therapy has been mainly based on in vitro flat biology, including the co-culturing with cell compartmentalization or with cell-to-cell contact, and on in vivo cancer models with different routes of MSC inoculation. More complex in vitro 3D models based on spheroid structures that are formed by intermingled MSC and tumour cells are also capturing the interest in cancer research. These are innovative culture systems tailored on the specific tumour type and that can be combined with a synthetic extracellular matrix, or included in in silico technologies, to more properly mimic the in vivo biological, spatial, biochemical, and biophysical features of tumour tissues. In this review, we summarized the most popular and currently available preclinical models for evaluating the role of MSC in cancer and their specific suitability, for example, in assaying the MSC-driven induction of epithelial-to-mesenchymal transition or of stem-like traits in cancer cells. Finally, we enlightened the need to carefully consider those parameters that might unintentionally strongly affect the secretome in MSC-cancer interplay and introduce confounding variables for the interpretation of results.

Coatings on mammalian cells: interfacing cells with their environment

The research community is intent on harnessing increasingly complex biological building blocks. At present, cells represent a highly functional component for integration into higher order systems. In this review, we discuss the current application space for cellular coating technologies and emphasize the relationship between the target application and coating design. We also discuss how the cell and the coating interact in common analytical techniques, and where caution must be exercised in the interpretation of results. Finally, we look ahead at emerging application areas that are ideal for innovation in cellular coatings. In all, cellular coatings leverage the machinery unique to specific cell types, and the opportunities derived from these hybrid assemblies have yet to be fully realized.

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.

Mesenchymal stem cells in preclinical cancer cytotherapy: a systematic review

Mesenchymal stem cells (MSC) comprise a heterogeneous population of rapidly proliferating cells that can be isolated from adult (e.g., bone marrow, adipose tissue) as well as fetal (e.g., umbilical cord) tissues (termed bone marrow (BM)-, adipose tissue (AT)-, and umbilical cord (UC)-MSC, respectively) and are capable of differentiation into a wide range of non-hematopoietic cell types. An additional, unique attribute of MSC is their ability to home to tumor sites and to interact with the local supportive microenvironment which rapidly conceptualized into MSC-based experimental cancer cytotherapy at the turn of the century. Towards this purpose, both naïve (unmodified) and genetically modified MSC (GM-MSC; used as delivery vehicles for the controlled expression and release of antitumorigenic molecules) have been employed using well-established in vitro and in vivo cancer models, albeit with variable success. The first approach is hampered by contradictory findings regarding the effects of naïve MSC of different origins on tumor growth and metastasis, largely attributed to inherent biological heterogeneity of MSC as well as experimental discrepancies. In the second case, although the anti-cancer effect of GM-MSC is markedly improved over that of naïve cells, it is yet apparent that some protocols are more efficient against some types of cancer than others. Regardless, in order to maximize therapeutic consistency and efficacy, a deeper understanding of the complex interaction between MSC and the tumor microenvironment is required, as well as examination of the role of key experimental parameters in shaping the final cytotherapy outcome. This systematic review represents, to the best of our knowledge, the first thorough evaluation of the impact of experimental anti-cancer therapies based on MSC of human origin (with special focus on human BM-/AT-/UC-MSC). Importantly, we dissect the commonalities and differences as well as address the shortcomings of work accumulated over the last two decades and discuss how this information can serve as a guide map for optimal experimental design implementation ultimately aiding the effective transition into clinical trials.

Tropism of mesenchymal stem cell toward CD133+ stem cell of glioblastoma in vitro and promote tumor proliferation in vivo

Background

Previous studies have demonstrated remarkable tropism of mesenchymal stem cells (MSCs) toward malignant gliomas, making these cells a potential vehicle for delivery of therapeutic agents to disseminated glioblastoma (GBM) cells. However, the potential contribution of MSCs to tumor progression is a matter of concern. It has been suggested that CD133⁺ GBM stem cells secrete a variety of chemokines, including monocytes chemoattractant protein-1 (MCP-1/CCL2) and stromal cell-derived factor-1(SDF-1/CXCL12), which could act in this tropism. However, the role in the modulation of this tropism of the subpopulation of CD133⁺ cells, which initiate GBM and the mechanisms underlying the tropism of MSCs to CD133⁺ GBM cells and their effects on tumor development, remains poorly defined.

Methods/results

We found that isolated and cultured MSCs (human umbilical cord blood MSCs) express CCR2 and CXCR4, the respective receptors for MCP-1/CCL2 and SDF-1/CXCL12, and demonstrated, in vitro, that MCP-1/CCL2 and SDF-1/CXC12, secreted by CD133⁺ GBM cells from primary cell cultures, induce the migration of MSCs. In addition, we confirmed that after in vivo GBM tumor establishment, by stereotaxic implantation of the CD133⁺ GBM cells labeled with Qdots (705 nm), MSCs labeled with multimodal iron oxide nanoparticles (MION) conjugated to rhodamine-B (Rh-B) (MION-Rh), infused by caudal vein, were able to cross the blood-brain barrier of the animal and migrate to the tumor region. Evaluation GBM tumors histology showed that groups that received MSC demonstrated tumor development, glial invasiveness, and detection of a high number of cycling cells.

Conclusions

Therefore, in this study, we validated the chemotactic effect of MCP-1/CCL2 and SDF-1/CXCL12 in mediating the migration of MSCs toward CD133⁺ GBM cells. However, we observed that, after infiltrating the tumor, MSCs promote tumor growth in vivo probably by release of exosomes. Thus, the use of these cells as a therapeutic carrier strategy to target GBM cells must be approached with caution.

Prussian Blue Nanoparticle-Labeled Mesenchymal Stem Cells: Evaluation of Cell Viability, Proliferation, Migration, Differentiation, Cytoskeleton, and Protein Expression In Vitro

Mesenchymal stem cells (MSCs) have been used for the treatment of various human diseases. To better understand the mechanism of this action and the fate of these cells, magnetic resonance imaging (MRI) has been used for the tracking of transplanted stem cells. Prussian blue nanoparticles (PBNPs) have been demonstrated to have the ability of labeling cells to visualize them as an effective MRI contrast agent. In this study, we aimed to investigate the efficiency and biological effects of labeled MSCs using PBNPs. We first synthesized and characterized the PBNPs. Then, iCELLigence real-time cell analysis system revealed that PBNPs did not significantly alter cell viability, proliferation, and migration activity in PBNP-labeled MSCs. Oil Red O staining and Alizarin Red staining revealed that labeled MSCs also have a normal differentiation capacity. Phalloidin staining showed no negative effect of PBNPs on the cytoskeleton. Western blot analysis indicated that PBNPs also did not change the expression of β-catenin and vimentin of MSCs. In vitro MRI, the pellets of the MSCs incubated with PBNPs showed a clear MRI signal darkening effect. In conclusion, PBNPs can be effectively used for the labeling of MSCs and will not influence the biological characteristics of MSCs.

Imaging Gliomas with Nanoparticle-Labeled Stem Cells

Objective:

Gliomas are the most common neoplasm of the central nervous system (CNS); however, traditional imaging techniques do not show the boundaries of tumors well. Some researchers have found a new therapeutic mode to combine nanoparticles, which are nanosized particles with various properties for specific therapeutic purposes, and stem cells for tracing gliomas. This review provides an introduction of the basic understanding and clinical applications of the combination of stem cells and nanoparticles as a contrast agent for glioma imaging.

Data Sources:

Studies published in English up to and including 2017 were extracted from the PubMed database with the selected key words of “stem cell,” “glioma,” “nanoparticles,” “MRI,” “nuclear imaging,” and “Fluorescence imaging.”

Study Selection:

The selection of studies focused on both preclinical studies and basic studies of tracking glioma with nanoparticle-labeled stem cells.

Results:

Studies have demonstrated successful labeling of stem cells with multiple types of nanoparticles. These labeled stem cells efficiently migrated to gliomas of varies models and produced signals sensitively captured by different imaging modalities.

Conclusion:

The use of nanoparticle-labeled stem cells is a promising imaging platform for the tracking and treatment of gliomas.

Image-Guided Resection of Glioblastoma and Intracranial Implantation of Therapeutic Stem Cell-seeded Scaffolds

Glioblastoma (GBM), the most common and aggressive primary brain cancer, carries a life expectancy of 12-15 months. The short life expectancy is due in part to the inability of the current treatment, consisting of surgical resection followed by radiation and chemotherapy, to eliminate invasive tumor foci. Treatment of these foci may be improved with tumoricidal human mesenchymal stem cells (MSCs). MSCs exhibit potent tumor tropism and can be engineered to express therapeutic proteins that kill tumor cells. Advancements in preclinical models indicate that surgical resection induces premature MSC loss and reduces therapeutic efficacy. Efficacy of MSC treatment can be improved by seeding MSCs on a biodegradable poly(lactic acid) (PLA) scaffold. MSC delivery into the surgical resection cavity on a PLA scaffold restores cell retention, persistence, and tumor killing. To study the effects of MSC-seeded PLA implantation on GBM, an accurate preclinical model is needed. Here we provide a preclinical surgical protocol for image-guided tumor resection of GBM in immune-deficient mice followed by MSC-seeded scaffold implantation. MSCs are engineered with lentiviral constructs to constitutively express and secrete therapeutic TNFα-related apoptosis-inducing ligand (TRAIL) as well as green fluorescent protein (GFP) to allow fluorescent tracking. Similarly, the U87 tumor cells are engineered to express mCherry and firefly luciferase, providing dual fluorescent/luminescent tracking. While currently used for investigating stem cell mediated delivery of therapeutics, this protocol could be modified to investigate the impact of surgical resection on other GBM interventions.

Magnetic resonance and photoacoustic imaging of brain tumor mediated by mesenchymal stem cell labeled with multifunctional nanoparticle introduced via carotid artery injection

OBJECTIVE

To evaluate the feasibility of visualizing bone marrow-derived human mesenchymal stem cells (MSCs) labeled with a gold-coated magnetic resonance (MR)-active multifunctional nanoparticle and injected via the carotid artery for assessing the extent of MSC homing in glioma-bearing mice.

MATERIALS AND METHODS

Nanoparticles containing superparamagnetic iron oxide coated with gold (SPIO@Au) with a diameter of ∼82 nm and maximum absorbance in the near infrared region were synthesized. Bone marrow-derived MSCs conjugated with green fluorescent protein (GFP) were successfully labeled with SPIO@Au at 4 μg ml^-1 and injected via the internal carotid artery in six mice bearing orthotopic U87 tumors. Unlabeled MSCs were used as a control. The ability of SPIO@Au-loaded MSCs to be imaged using MR and photoacoustic (PA) imaging at t = 0 h, 2 h, 24 h, and 72 h was assessed using a 7 T Bruker Biospec experimental MR scanner and a Vevo LAZR PA imaging system with a 5 ns laser as the excitation source. Histological analysis of the brain tissue was performed 72 h after MSC injection using GFP fluorescence, Prussian blue staining, and hematoxylin-and-eosin staining.

RESULTS

MSCs labeled with SPIO@Au at 4 μg ml^-1 did not exhibit cell death or any adverse effects on differentiation or migration. The PA signal in tumors injected with SPIO@Au-loaded MSCs was clearly more enhanced post-injection, as compared with the tumors injected with unlabeled MSCs at t = 72 h. Using the same mice, T2-weighted MR imaging results taken before injection and at t = 2 h, 24 h, and 72 h were consistent with the PA imaging results, showing significant hypointensity of the tumor in the presence of SPIO@Au-loaded MSCs. Histological analysis also showed co-localization of GFP fluorescence and iron, thereby confirming that SPIO@Au-labeled MSCs continue to carry their nanoparticle payloads even at 72 h after injection.

CONCLUSIONS

Our results demonstrated the feasibility of tracking carotid artery-injected SPIO@Au-labeled MSCs in vivo via MR and PA imaging.

In vivo tracking of the tropism of mesenchymal stem cells to malignant gliomas using reporter gene-based MR imaging

Mesenchymal stem cells (MSCs) have emerged as a promising cellular vehicle for gene therapy of malignant gliomas due to their property of tumor tropism. However, MSCs may show bidirectional and divergent effects on tumor growth. Therefore, a robust surveillance system with a capacity for noninvasive monitoring of the homing, distribution and fate of stem cells in vivo is highly desired for developing stem cell-based gene therapies for tumors. In this study, we used ferritin gene-based magnetic resonance imaging (MRI) to track the tumor tropism of MSCs in a rat orthotopic xenograft model of malignant glioma. MSCs were transduced with lentiviral vectors expressing ferritin heavy chain (FTH) and enhanced green fluorescent protein (eGFP). Intra-arterial, intravenous and intertumoral injections of these FTH transgenic MSCs (FTH-MSCs) were performed in rats bearing intracranial orthotopic C6 gliomas. The FTH-MSCs were detected as hypointense signals on T2- and T2*-weighted images on a 3.0 T clinical MRI. After intra-arterial injection, 17% of FTH-MSCs migrated toward the tumor and gradually diffused throughout the orthotopic glioma. This dynamic process could be tracked in vivo by MRI up to 10 days of follow-up, as confirmed by histology. Moreover, the tumor tropism of MSCs showed no appreciable impact on the progression of the tumor. These results suggest that FTH reporter gene-based MRI can be used to reliably track the tropism and fate of MSCs after their systemic transplantation in orthotopic gliomas. This real-time in vivo tracking system will facilitate the future development of stem cell-based therapies for malignant gliomas.

In vivo monitoring of magnetically labeled mesenchymal stem cells homing to rabbit hepatic VX2 tumors using magnetic resonance imaging

Although mesenchymal stem cells (MSCs) have been demonstrated to possess a tumor‑homing feature, their tropism to liver tumors has not been delineated in a visible manner. The aim of the present study was to evaluate the tumor‑homing capacity of MSCs and to investigate the spatial and temporal distributions of MSCs in liver tumors using magnetic resonance imaging (MRI). MSCs were colabeled with superparamagnetic iron oxide (SPIO) particles and 4',6‑diamidino‑2‑phenylindole (DAPI), and then transplanted into rabbits with VX2 liver tumors through intravenous injections. The rabbits were subjected to MRI before and at 3, 7 and 14 days after cell transplantation using a clinical 1.5‑T MRI system. Immediately after the MRI examination, histological analyses were performed using fluorescence and Prussian blue staining. At 3 days after injection with labeled MSCs, heterogeneous hypointensity was detected on the MRI images of the tumor. At 7 days after transplantation, the tumor exhibited anisointense MRI signal, whereas a hypointense ring was detected at the border of the tumor. At 14 days after transplantation, the MRI signal recovered the hyperintensity. As demonstrated in the histological analyses, the distribution of the iron particles visualized with Prussian blue staining was consistent with the DAPI‑stained bright fluorescent nuclei, and the particles corresponded to the hypointense region on the MR images. Thus, systemically administered MSCs could localize to liver tumors with high specificity and possessed a migration feature with active tumor growth. These results demonstrated that the targeting and distribution of the magnetically labeled stem cells in the tumor could be tracked for 7 days in vivo using a clinical 1.5‑T MRI scanner.

Impact of mesenchymal stem cells' secretome on glioblastoma pathophysiology

Background

Glioblastoma (GBM) is a highly aggressive primary brain cancer, for which curative therapies are not available. An emerging therapeutic approach suggested to have potential to target malignant gliomas has been based on the use of multipotent mesenchymal stem cells (MSCs), either unmodified or engineered to deliver anticancer therapeutic agents, as these cells present an intrinsic capacity to migrate towards malignant tumors. Nevertheless, it is still controversial whether this innate tropism of MSCs towards the tumor area is associated with cancer promotion or suppression. Considering that one of the major mechanisms by which MSCs interact with and modulate tumor cells is via secreted factors, we studied how the secretome of MSCs modulates critical hallmark features of GBM cells.

Methods

The effect of conditioned media (CM) from human umbilical cord perivascular cells (HUCPVCs, a MSC population present in the Wharton’s jelly of the umbilical cord) on GBM cell viability, migration, proliferation and sensitivity to temozolomide treatment of U251 and SNB-19 GBM cells was evaluated. The in vivo chicken chorioallantoic membrane (CAM) assay was used to evaluate the effect of HUCPVCs CM on tumor growth and angiogenesis. The secretome of HUCPVCs was characterized by proteomic analyses.

Results

We found that both tested GBM cell lines exposed to HUCPVCs CM presented significantly higher cellular viability, proliferation and migration. In contrast, resistance of GBM cells to temozolomide chemotherapy was not significantly affected by HUCPVCs CM. In the in vivo CAM assay, CM from HUCPVCs promoted U251 and SNB-19 tumor cells growth. Proteomic analysis to characterize the secretome of HUCPVCs identified several proteins involved in promotion of cell survival, proliferation and migration, revealing novel putative molecular mediators for the effects observed in GBM cells exposed to HUCPVCs CM.

Conclusions

These findings provide novel insights to better understand the interplay between GBM cells and MSCs, raising awareness to potential safety issues regarding the use of MSCs as stem-cell based therapies for GBM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1303-8) contains supplementary material, which is available to authorized users.

Potential New Therapies for Pediatric Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an extensively invasive malignancy with infiltration into other regions of the brainstem. Although large numbers of specific targeted therapies have been tested, no significant progress has been made in treating these high-grade gliomas. Therefore, the identification of new therapeutic approaches is of great importance for the development of more effective treatments. This article reviews the conventional therapies and new potential therapeutic approaches for DIPG, including epigenetic therapy, immunotherapy, and the combination of stem cells with nanoparticle delivery systems.

Characterization of the Tumor Microenvironment and Tumor-Stroma Interaction by Non-invasive Preclinical Imaging

Tumors are often characterized by hypoxia, vascular abnormalities, low extracellular pH, increased interstitial fluid pressure, altered choline-phospholipid metabolism, and aerobic glycolysis (Warburg effect). The impact of these tumor characteristics has been investigated extensively in the context of tumor development, progression, and treatment response, resulting in a number of non-invasive imaging biomarkers. More recent evidence suggests that cancer cells undergo metabolic reprograming, beyond aerobic glycolysis, in the course of tumor development and progression. The resulting altered metabolic content in tumors has the ability to affect cell signaling and block cellular differentiation. Additional emerging evidence reveals that the interaction between tumor and stroma cells can alter tumor metabolism (leading to metabolic reprograming) as well as tumor growth and vascular features. This review will summarize previous and current preclinical, non-invasive, multimodal imaging efforts to characterize the tumor microenvironment, including its stromal components and understand tumor-stroma interaction in cancer development, progression, and treatment response.

Molecular Imaging of Brain Tumors Using Liposomal Contrast Agents and Nanoparticles

The first generation of cross-sectional brain imaging using computed tomography (CT), ultrasonography, and eventually MR imaging focused on determining structural or anatomic changes associated with brain disorders. The current state-of-the-art imaging, functional imaging, uses techniques such as CT and MR perfusion that allow determination of physiologic parameters in vivo. In parallel, tissue-based genomic, transcriptomic, and proteomic profiling of brain tumors has created several novel and exciting possibilities for molecular targeting of brain tumors. The next generation of imaging translates these molecular in vitro techniques to in vivo, noninvasive, targeted reconstruction of tumors and their microenvironments.

Practical Issues with the Use of Stem Cells for Cancer Gene Therapy

Stem cell-based drug delivery for cancer therapy has steadily gained momentum in the past decade as several studies have reported stem cells' inherent tropism towards tumors. Since this science is still in its early stages and there are many factors that could significantly impact tumor tropism of stem cells, some contradictory results have been observed. This review starts by examining a number of proof-of-concept studies that demonstrate the potential application of stem cells in cancer therapy. Studies that illustrate stem cells' tumor tropism and discuss the technical difficulties that could impact the therapeutic outcome are also highlighted. The discussion also emphasizes stem cell imaging/tracking, as it plays a crucial role in performing reliable dose-response studies and evaluating the therapeutic outcome of treatment protocols. In each section, the pros and cons associated with each method are highlighted, limitations are underlined, and potential solutions are discussed. The overall intention is to familiarize the reader with important practical issues related to stem cell cancer tropism and in vivo tracking, underline the shortcomings, and emphasize critical factors that need to be considered for effective translation of this science into the clinic.

Application of iron oxide nanoparticles in glioma imaging and therapy: from bench to bedside

Gliomas are the most common primary brain tumors and have a very dismal prognosis. However, recent advancements in nanomedicine and nanotechnology provide opportunities for personalized treatment regimens to improve the poor prognosis of patients suffering from glioma. This comprehensive review starts with an outline of the current status facing glioma. It then provides an overview of the state-of-the-art applications of iron oxide nanoparticles (IONPs) to glioma diagnostics and therapeutics, including MR contrast enhancement, drug delivery, cell labeling and tracking, magnetic hyperthermia treatment and magnetic particle imaging. It also addresses current challenges associated with the biological barriers and IONP design with an emphasis on recent advances and innovative approaches for glioma targeting strategies. Opportunities for future development are highlighted.

CD44 promotes the migration of bone marrow-derived mesenchymal stem cells toward glioma

Previous in vivo and in vitro studies have shown that human mesenchymal stem cells (MSCs) exhibit tropism for gliomas. However, the mechanism underlying this directed migration remains unclear. The aim of the present study was to investigate the possible mechanism underlying platelet-derived growth factor-BB (PDGF-BB)-induced chemotactic migration of bone marrow-derived MSCs (BMSCs) toward glioma. Rat glioma C6 cell-conditioned medium was utilized to evaluate the chemotactic response of BMSCs toward glioma using an in vitro migration assay. Recombinant rat PDGF-BB was added to C6 cell-conditioned medium to assess its effect on the tropism of BMSCs. The effect of PDGF-BB on the expression levels of cluster of differentiation (CD)44 in BMSCs was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence assays. The results revealed that chemotactic migration was induced in BMSCs by rat glioma C6 cell-conditioned medium, which was enhanced by PDGF-BB treatment in a dose-dependent manner. Furthermore, RT-PCR and immunofluorescence assays showed that CD44 expression was upregulated in BMSCs following treatment with 40 ng/ml PDGF-BB for 12 h. Additionally, 3-h pretreatment with the anti-CD44 neutralizing antibody OX-50 was observed to attenuate the tropism of BMSCs toward glioma in the presence or absence of PDGF-BB. The results of the present study indicate that CD44 mediates the tropism of BMSCs toward glioma, and PDGF-BB promotes the migration of BMSCs toward glioma via the upregulation of CD44 expression in BMSCs. These findings suggest CD44 inhibition may be a potential therapeutic target for the treatment of glioma.

Controlled Payload Release by Magnetic Field Triggered Neural Stem Cell Destruction for Malignant Glioma Treatment

Stem cells have recently garnered attention as drug and particle carriers to sites of tumors, due to their natural ability to track to the site of interest. Specifically, neural stem cells (NSCs) have demonstrated to be a promising candidate for delivering therapeutics to malignant glioma, a primary brain tumor that is not curable by current treatments, and inevitably fatal. In this article, we demonstrate that NSCs are able to internalize 2 μm magnetic discs (SD), without affecting the health of the cells. The SD can then be remotely triggered in an applied 1 T rotating magnetic field to deliver a payload. Furthermore, we use this NSC-SD delivery system to deliver the SD themselves as a therapeutic agent to mechanically destroy glioma cells. NSCs were incubated with the SD overnight before treatment with a 1T rotating magnetic field to trigger the SD release. The potential timed release effects of the magnetic particles were tested with migration assays, confocal microscopy and immunohistochemistry for apoptosis. After the magnetic field triggered SD release, glioma cells were added and allowed to internalize the particles. Once internalized, another dose of the magnetic field treatment was administered to trigger mechanically induced apoptotic cell death of the glioma cells by the rotating SD. We are able to determine that NSC-SD and magnetic field treatment can achieve over 50% glioma cell death when loaded at 50 SD/cell, making this a promising therapeutic for the treatment of glioma.

Antitumoral Effect of Mural Cells Assessed With High-Resolution MRI and Fluorescence Microscopy

OBJECTIVE

The purpose of this study was to detect labeled mural cells in vivo and study their therapeutic effect on tumor growth and on functional changes in the vascular network by use of MRI and fibered confocal fluorescence microscopy (FCFM).

MATERIALS AND METHODS

Twenty-eight mice were allocated to the following three groups 7 days after injection of TC1 tumor cells (C157 black 6): control, no injection (n = 7); sham, injection of phosphate-buffered saline solution (n = 10); and treated, injection of human mural cells (n = 11). Tumor growth was measured with calipers. Labeled mural cells were tracked with high-resolution MRI and FCFM. Microvessel density was assessed with MRI and FCFM, and the findings were compared with the histologic results.

RESULTS

Tumor growth was significantly slowed in the treated group starting on day 10 (p = 0.001). Round signal-intensity voids were observed in the center of six of seven tumors treated with magnetically labeled mural cells. Positive staining for iron was observed in histologic sections of two of five of these tumors. Microvessel density measured with FCFM was greater in the treated mice (p = 0.03). Flow cytometry revealed viable human mural cells only in treated tumors.

CONCLUSION

In this study, imaging techniques such as high-resolution MRI and FCFM showed the therapeutic effect of mural cell injection on tumor growth and microvessel function.

Nanomaterial applications in multiple sclerosis inflamed brain

In the last years scientific progress in nanomaterials, where size and shape make the difference, has increased their utilization in medicine with the development of a promising new translational science: nanomedicine. Due to their surface and core biophysical properties, nanomaterials hold the promise for medical applications in central nervous system (CNS) diseases: inflammatory, degenerative and tumors. The present review is focused on nanomaterials at the neuro-immune interface, evaluating two aspects: the possible CNS inflammatory response induced by nanomaterials and the developments of nanomaterials to improve treatment and diagnosis of neuroinflammatory diseases, with a focus on multiple sclerosis (MS). Indeed, nanomedicine allows projecting new ways of drug delivery and novel techniques for CNS imaging. Despite the wide field of application in neurological diseases of nanomaterials, our topic here is to review the more recent development of nanomaterials that cross blood brain barrier (BBB) and reach specific target during CNS inflammatory diseases, a crucial strategy for CNS early diagnosis and drug delivery, indeed the main challenges of nanomedicine.

Neurobehavioral burden of multiple sclerosis with nanotheranostics

Multiple sclerosis (MS) is a chronic demyelinating neurological disorder affecting people worldwide; women are affected more than men. MS results in serious neurological deficits along with behavioral compromise, the mechanisms of which still remain unclear. Behavioral disturbances such as depression, anxiety, cognitive impairment, psychosis, euphoria, sleep disturbances, and fatigue affect the quality of life in MS patients. Among these, depression and psychosis are more common than any other neurological disorders. In addition, depression is associated with other comorbidities. Although anxiety is often misdiagnosed in MS patients, it can induce suicidal ideation if it coexists with depression. An interrelation between sleep abnormalities and fatigue is also reported among MS patients. In addition, therapeutics for MS is always a challenge because of the presence of the blood-brain barrier, adding to the lack of detailed understanding of the disease pathology. In this review, we tried to summarize various behavioral pathologies and their association with MS, followed by its conventional treatment and nanotheranostics.

Multifunctional nanoparticles for brain tumor imaging and therapy

Brain tumors are a diverse group of neoplasms that often carry a poor prognosis for patients. Despite tremendous efforts to develop diagnostic tools and therapeutic avenues, the treatment of brain tumors remains a formidable challenge in the field of neuro-oncology. Physiological barriers including the blood-brain barrier result in insufficient accumulation of therapeutic agents at the site of a tumor, preventing adequate destruction of malignant cells. Furthermore, there is a need for improvements in brain tumor imaging to allow for better characterization and delineation of tumors, visualization of malignant tissue during surgery, and tracking of response to chemotherapy and radiotherapy. Multifunctional nanoparticles offer the potential to improve upon many of these issues and may lead to breakthroughs in brain tumor management. In this review, we discuss the diagnostic and therapeutic applications of nanoparticles for brain tumors with an emphasis on innovative approaches in tumor targeting, tumor imaging, and therapeutic agent delivery. Clinically feasible nanoparticle administration strategies for brain tumor patients are also examined. Furthermore, we address the barriers towards clinical implementation of multifunctional nanoparticles in the context of brain tumor management.

Drug-loaded nanoparticle systems and adult stem cells: a potential marriage for the treatment of malignant glioma?

Despite all recent advances in malignant glioma research, only modest progress has been achieved in improving patient prognosis and quality of life. Such a clinical scenario underscores the importance of investing in new therapeutic approaches that, when combined with conventional therapies, are able to effectively eradicate glioma infiltration and target distant tumor foci. Nanoparticle-loaded delivery systems have recently arisen as an exciting alternative to improve targeted anti-glioma drug delivery. As drug carriers, they are able to efficiently protect the therapeutic agent and allow for sustained drug release. In addition, their surface can be easily manipulated with the addition of special ligands, which are responsible for enhancing tumor-specific nanoparticle permeability. However, their inefficient intratumoral distribution and failure to target disseminated tumor burden still pose a big challenge for their implementation as a therapeutic option in the clinical setting. Stem cell-based delivery of drug-loaded nanoparticles offers an interesting option to overcome such issues. Their ability to incorporate nanoparticles and migrate throughout interstitial barriers, together with their inherent tumor-tropic properties and synergistic anti-tumor effects make these stem cell carriers a good fit for such combined therapy. In this review, we will describe the main nanoparticle delivery systems that are presently available in preclinical and clinical studies. We will discuss their mechanisms of targeting, current delivery methods, attractive features and pitfalls. We will also debate the potential applications of stem cell carriers loaded with therapeutic nanoparticles in anticancer therapy and why such an attractive combined approach has not yet reached clinical trials.

Therapeutic nanomedicine for brain cancer

Malignant brain cancer treatment is limited by a number of barriers, including the blood-brain barrier, transport within the brain interstitium, difficulties in delivering therapeutics specifically to tumor cells, the highly invasive quality of gliomas and drug resistance. As a result, the prognosis for patients with high-grade gliomas is poor and has improved little in recent years. Nanomedicine approaches have been developed in the laboratory, with some technologies being translated to the clinic, in order to address these needs. This review discusses the obstacles to effective treatment that are currently faced in the field, as well as various nanomedicine techniques that have been used or are being explored to overcome them, with a focus on liposomal and polymeric nanoparticles.

Multifunctional superparamagnetic iron oxide nanoparticles: design, synthesis and biomedical photonic applications

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown great promise in biomedical applications. In this review, we summarize the recent advances in the design and fabrication of core-shell and hetero-structured SPIONs and further outline some exciting developments and progresses of these multifunctional SPIONs for diagnosis, multimodality imaging, therapy, and biophotonics.

Magnetic resonance imaging tracking of ferumoxytol-labeled human neural stem cells: studies leading to clinical use

Numerous stem cell-based therapies are currently under clinical investigation, including the use of neural stem cells (NSCs) as delivery vehicles to target therapeutic agents to invasive brain tumors. The ability to monitor the time course, migration, and distribution of stem cells following transplantation into patients would provide critical information for optimizing treatment regimens. No effective cell-tracking methodology has yet garnered clinical acceptance. A highly promising noninvasive method for monitoring NSCs and potentially other cell types in vivo involves preloading them with ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) to enable cell tracking using magnetic resonance imaging (MRI). We report here the preclinical studies that led to U.S. Food and Drug Administration approval for first-in-human investigational use of ferumoxytol to label NSCs prior to transplantation into brain tumor patients, followed by surveillance serial MRI. A combination of heparin, protamine sulfate, and ferumoxytol (HPF) was used to label the NSCs. HPF labeling did not affect cell viability, growth kinetics, or tumor tropism in vitro, and it enabled MRI visualization of NSC distribution within orthotopic glioma xenografts. MRI revealed dynamic in vivo NSC distribution at multiple time points following intracerebral or intravenous injection into glioma-bearing mice that correlated with histological analysis. Preclinical safety/toxicity studies of intracerebrally administered HPF-labeled NSCs in mice were also performed, and they showed no significant clinical or behavioral changes, no neuronal or systemic toxicities, and no abnormal accumulation of iron in the liver or spleen. These studies support the clinical use of ferumoxytol labeling of cells for post-transplant MRI visualization and tracking.

Intranasal delivery of mesenchymal stem cells significantly extends survival of irradiated mice with experimental brain tumors

Treatment options of glioblastoma multiforme are limited due to the blood-brain barrier (BBB). In this study, we investigated the utility of intranasal (IN) delivery as a means of transporting stem cell-based antiglioma therapeutics. We hypothesized that mesenchymal stem cells (MSCs) delivered via nasal application could impart therapeutic efficacy when expressing TNF-related apoptosis-inducing ligand (TRAIL) in a model of human glioma. ¹¹¹In-oxine, histology and magnetic resonance imaging (MRI) were utilized to track MSCs within the brain and associated tumor. We demonstrate that MSCs can penetrate the brain from nasal cavity and infiltrate intracranial glioma xenografts in a mouse model. Furthermore, irradiation of tumor-bearing mice tripled the penetration of (¹¹¹In)-oxine-labeled MSCs in the brain with a fivefold increase in cerebellum. Significant increase in CXCL12 expression was observed in irradiated xenograft tissue, implicating a CXCL12-dependent mechanism of MSCs migration towards irradiated glioma xenografts. Finally, MSCs expressing TRAIL improved the median survival of irradiated mice bearing intracranial U87 glioma xenografts in comparison with nonirradiated and irradiated control mice. Cumulatively, our data suggest that IN delivery of stem cell-based therapeutics is a feasible and highly efficacious treatment modality, allowing for repeated application of modified stem cells to target malignant glioma.

Specific chemotaxis of magnetically labeled mesenchymal stem cells: implications for MRI of glioma

PURPOSE

Glioblastoma multiforme (GBM) is a lethal disease marked by infiltration of cancerous cells into the surrounding normal brain. The dire outcome of GBM patients stems in part from the limitations of current neuroimaging methods. Notably, early cancer detection methodologies are lacking, without the ability to identify aggressive, metastatic tumor cells. We propose a novel approach for tumor detection using magnetic resonance imaging (MRI) based on imaging specific tumor tropism of mesenchymal stem cells (MSCs) labeled with micron-sized iron oxide particles (MPIOs).

PROCEDURES

MPIO labeled and unlabeled MSCs were compared for viability, multi-lineage differentiation, and migration, where both chemotactic and chemokinetic movement were assessed in the presence of serum-free medium, serum-containing medium, and glioma-conditioned medium. MRI was performed on agarose samples, consisting of MPIO-labeled single MSCs, to confirm the capability to detect single cells.

RESULTS

We determined that MPIO-labeled MSCs exhibit specific and significant chemotactic migration towards glioma-conditioned medium in vitro. Confocal fluorescence microscopy confirmed that MPIOs are internalized and do not impact important cell processes of MSCs. Lastly, MPIO-labeled MSCs appear as single distinct, dark spots on T(2)*-weighted MRI, supporting the robustness of this contrast agent for cell tracking.

CONCLUSIONS

This is the first study to show that MPIO-labeled MSCs exhibit specific tropism toward tumor-secreted factors in vitro. The potential for detecting single MPIO-labeled MSCs provides rationale for in vivo extension of this methodology to visualize GBM in animal models.

Mesenchymal stem cells overexpressing PEDF decrease the angiogenesis of gliomas

The present study is an exploration of a novel strategy to target a therapeutic gene to brain tumour tissues. In the present study, we evaluated the feasibility of using hMSCs (human mesenchymal stem cells) to deliver PEDF (pigment epithelium-derived factor), a potent inhibitor of tumour angiogenesis, in a model of intracranial gliomas. To assess its potential of tracking gliomas, MSCs (mesenchymal stem cells) were injected into the cerebral hemisphere and it showed that MSCs infiltrated into the vessel beds and scattered throughout the tumour. In vitro migration assay showed that the VEGF (vascular endothelial growth factor) enhanced MSC migration. In contrast, the migratory activity of MSCs was significantly inhibited with the presence of PEDF. Systematic delivery of AAV (adeno-associated virus)–PEDF to established glioma xenografts resulted in increased apoptosis of gliomas. In addition, MSC–PEDF treatment prolonged the survival of mice bearing U87 gliomas. Taken together, these data validate that MSCs–PEDF can migrate and deliver PEDF to target glioma cells, which may be a novel and promising therapeutic approach for refractory brain tumour.

Intrahippocampal transplantation of mesenchymal stromal cells promotes neuroplasticity

BACKGROUND AIMS

Multipotent mesenchymal stromal cells (MSC) secrete soluble factors that stimulate the surrounding microenvironment. Such paracrine effects might underlie the potential benefits of many stem cell therapies. We tested the hypothesis that MSC are able to enhance intrinsic cellular plasticity in the adult rat hippocampus.

METHODS

Rat bone marrow-derived MSC were labeled with very small superparamagnetic iron oxide particles (VSOP), which allowed for non-invasive graft localization by magnetic resonance imaging (MRI). Moreover, MSC were transduced with lentiviral vectors to express the green fluorescent protein (GFP). The effects of bilateral MSC transplantation on hippocampal cellular plasticity were assessed using the thymidine analogs 5-bromo-2'-deoxyuridine (BrdU) and 5-iodo-2'-deoxyuridine (IdU). Behavioral testing was performed to examine the consequences of intrahippocampal MSC transplantation on locomotion, learning and memory, and anxiety-like and depression-like behavior.

RESULTS

We found that intrahippocampal transplantation of MSC resulted in enhanced neurogenesis despite short-term graft survival. In contrast, systemic administration of the selective serotonin re-uptake inhibitor citalopram increased cell survival but did not affect cell proliferation. Intrahippocampal transplantation of MSC did not impair behavioral functions in rats, but only citalopram exerted anti-depressant effects.

CONCLUSIONS

This is the first study to examine the effects of intrahippocampal transplantation of allogeneic MSC on hippocampal structural plasticity and behavioral functions in rats combined with non-invasive cell tracking by MRI. We found that iron oxide nanoparticles can be used to detect transplanted MSC in the brain. Although graft survival was short, intrahippocampal transplantation of MSC resulted in long-term changes in hippocampal plasticity. Our results suggest that MSC can be used to stimulate adult neurogenesis.

Fluorescent magnetic nanoparticle-labeled mesenchymal stem cells for targeted imaging and hyperthermia therapy of in vivo gastric cancer

How to find early gastric cancer cells in vivo is a great challenge for the diagnosis and therapy of gastric cancer. This study is aimed at investigating the feasibility of using fluorescent magnetic nanoparticle (FMNP)-labeled mesenchymal stem cells (MSCs) to realize targeted imaging and hyperthermia therapy of in vivo gastric cancer. The primary cultured mouse marrow MSCs were labeled with amino-modified FMNPs then intravenously injected into mouse model with subcutaneous gastric tumor, and then, the in vivo distribution of FMNP-labeled MSCs was observed by using fluorescence imaging system and magnetic resonance imaging system. After FMNP-labeled MSCs arrived in local tumor tissues, subcutaneous tumor tissues in nude mice were treated under external alternating magnetic field. The possible mechanism of MSCs targeting gastric cancer was investigated by using a micro-multiwell chemotaxis chamber assay. Results show that MSCs were labeled with FMNPs efficiently and kept stable fluorescent signal and magnetic properties within 14 days, FMNP-labeled MSCs could target and image in vivo gastric cancer cells after being intravenously injected for 14 days, FMNP-labeled MSCs could significantly inhibit the growth of in vivo gastric cancer because of hyperthermia effects, and CCL19/CCR7 and CXCL12/CXCR4 axis loops may play key roles in the targeting of MSCs to in vivo gastric cancer. In conclusion, FMNP-labeled MSCs could target in vivo gastric cancer cells and have great potential in applications such as imaging, diagnosis, and hyperthermia therapy of early gastric cancer in the near future.

Nanotechnology applications for glioblastoma

Glioblastoma remains one of the most difficult cancers to treat and represents the most common primary malignancy of the brain. Although conventional treatments have found modest success in reducing the initial tumor burden, infiltrating cancer cells beyond the main mass are responsible for tumor recurrence and ultimate patient demise. Targeting residual infiltrating cancer cells requires the development of new treatment strategies. The emerging field of cancer nanotechnology holds promise in the use of multifunctional nanoparticles for imaging and targeted therapy of glioblastoma. This article examines the current state of nanotechnology in the treatment of glioblastoma and directions of further study.

Neural stem cell-mediated CE/CPT-11 enzyme/prodrug therapy in transgenic mouse model of intracerebellar medulloblastoma

Medulloblastoma is a heterogeneous diffuse neoplasm that can be highly disseminated, and is the most common malignant childhood brain tumor. Although multimodal treatments have improved survival rates for patients with medulloblastoma, these tumors are associated with high morbidity and mortality. New treatment strategies are urgently needed to improve cure rates and, importantly, to spare normal brain tissue from neurotoxicity and patients from life-long cognitive and functional deficits associated with current therapies. In numerous preclinical brain tumor models, neural stem cells (NSCs) have shown great promise as delivery vehicles for therapeutic genes. Here, we have used an established, genetically modified human NSC line (HB1.F3.CD) to deliver carboxylesterase (CE) to cerebellar tumor foci and locally activate the prodrug CPT-11 (Irinotecan) to the potent topoisomerase I inhibitor SN-38. HB1.F3.CD NSC tumor tropism, intratumoral distribution and therapeutic efficacy were investigated in clinically relevant experimental models. Magnetic resonance imaging was used for in vivo tracking of iron nanoparticle-labeled NSCs, and to assess the therapeutic efficacy of CE-expressing HB1.F3.CD cells. As compared to controls, a significant decrease in tumor growth rate was seen in mice that received both NSCs and CPT-11 as their treatment regimen. Thus, this study provides proof-of-concept for NSC-mediated CE/CPT-11 treatment of medulloblastoma, and serves as a foundation for further studies toward potential clinical application.

Magnetic nanoparticles: an emerging technology for malignant brain tumor imaging and therapy

Magnetic nanoparticles (MNPs) represent a promising nanomaterial for the targeted therapy and imaging of malignant brain tumors. Conjugation of peptides or antibodies to the surface of MNPs allows direct targeting of the tumor cell surface and potential disruption of active signaling pathways present in tumor cells. Delivery of nanoparticles to malignant brain tumors represents a formidable challenge due to the presence of the blood-brain barrier and infiltrating cancer cells in the normal brain. Newer strategies permit better delivery of MNPs systemically and by direct convection-enhanced delivery to the brain. Completion of a human clinical trial involving direct injection of MNPs into recurrent malignant brain tumors for thermotherapy has established their feasibility, safety and efficacy in patients. Future translational studies are in progress to understand the promising impact of MNPs in the treatment of malignant brain tumors.

Cancer nanotheranostics: improving imaging and therapy by targeted delivery across biological barriers

Cancer nanotheranostics aims to combine imaging and therapy of cancer through use of nanotechnology. The ability to engineer nanomaterials to interact with cancer cells at the molecular level can significantly improve the effectiveness and specificity of therapy to cancers that are currently difficult to treat. In particular, metastatic cancers, drug-resistant cancers, and cancer stem cells impose the greatest therapeutic challenge for targeted therapy. Targeted therapy can be achieved with appropriately designed drug delivery vehicles such as nanoparticles, adult stem cells, or T cells in immunotherapy. In this article, we first review the different types of nanotheranostic particles and their use in imaging, followed by the biological barriers they must bypass to reach the target cancer cells, including the blood, liver, kidneys, spleen, and particularly the blood-brain barrier. We then review how nanotheranostics can be used to improve targeted delivery and treatment of cancer cells. Finally, we discuss development of nanoparticles to overcome current limitations in cancer therapy.

Therapeutic effect of neural stem cells expressing TRAIL and bortezomib in mice with glioma xenografts

Treatment of glioblastoma remains a challenge in neuro-oncology. We investigated if treatment with neural stem cells engineered to express membrane-bound TRAIL (NSCs-mTRAIL) alone or in combination with proteasome inhibitors is a feasible therapeutic approach for experimental glioma. Glioma cells showed resistance to soluble TRAIL and proteasome inhibitors alone, but responded well to their combined treatment. In co-culture with NSCs-mTRAIL, glioma cells appeared to be more prone to apoptosis than to treatment with soluble TRAIL, which was enhanced by proteasome inhibitor bortezomib. In vivo, the survival of animals bearing intracranial glial xenografts was significantly improved by NSCs-mTRAIL. The addition of bortezomib further enhanced the efficacy of NSCs-TRAIL treated group in one of examined tumor models. These data demonstrate that therapy with NSCs-mTRAIL is a potent cell based approach for treatment of glioma. Such an approach warrants further search for therapeutics capable of increasing sensitivity of glioma cells to mTRAIL in vivo.

Ferritin enhances SPIO tracking of C6 rat glioma cells by MRI

PURPOSE

To investigate the effect of ferritin protein overexpression on superparamagnetic iron oxide (SPIO) particle labeling of C6 rat glioma cells, and track the labeled cells in vivo using magnetic resonance imaging (MRI).

MATERIALS AND METHODS

A plasmid of H-chain of murine ferritin gene was constructed and transfected into C6 cells. The parental and the transfected C6 cells labeled with SPIO were bilaterally inoculated subcutaneously into nude mice. The mice were imaged by multiple T2-weighted MR scans after C6 cell inoculation. The mice were killed 2 weeks later, and the concentration of iron in the tumor tissue was measured by inductively coupled plasma.

RESULTS

The iron concentration in xenografts derived from SPIO-labeled C6 cells that were transfected with ferritin plasmid was significantly higher than that in xenografts from parental C6 cells that were labeled with SPIO but not transfected (p = 0.034, N = 5). Ferritin-transfected C6 cells showed an improved T(2) contrast in vivo compared with parental cells labeled with SPIO but not transfected.

CONCLUSION

Coordinating ferritin with SPIO can lead to a longer MRI cellular tracking period.