Dynamic imaging of allogeneic mesenchymal stem cells trafficking to myocardial infarction

Concise Review: MSC-Derived Exosomes for Cell-Free Therapy

Mesenchymal stem cell transplantation is undergoing extensive evaluation as a cellular therapy in human clinical trials. Because MSCs are easily isolated and amenable to culture expansion in vitro there is a natural desire to test MSCs in many diverse clinical indications. This is exemplified by the rapidly expanding literature base that includes many in vivo animal models. More recently, MSC-derived extracellular vesicles (EVs), which include exosomes and microvesicles (MV), are being examined for their role in MSC-based cellular therapy. These vesicles are involved in cell-to-cell communication, cell signaling, and altering cell or tissue metabolism at short or long distances in the body. The exosomes and MVs can influence tissue responses to injury, infection, and disease. MSC-derived exosomes have a content that includes cytokines and growth factors, signaling lipids, mRNAs, and regulatory miRNAs. To the extent that MSC exosomes can be used for cell-free regenerative medicine, much will depend on the quality, reproducibility, and potency of their production, in the same manner that these parameters dictate the development of cell-based MSC therapies. However, the MSC exosome's contents are not static, but rather a product of the MSC tissue origin, its activities and the immediate intercellular neighbors of the MSCs. As such, the exosome content produced by MSCs appears to be altered when MSCs are cultured with tumor cells or in the in vivo tumor microenvironment. Therefore, careful attention to detail in producing MSC exosomes may provide a new therapeutic paradigm for cell-free MSC-based therapies with decreased risk. Stem Cells 2017;35:851-858.

Ultrasound-Mediated Mesenchymal Stem Cells Transfection as a Targeted Cancer Therapy Platform

Mesenchymal stem cells (MSCs) hold tremendous potential as a targeted cell-based delivery platform for inflammatory and cancer therapy. Genetic manipulation of MSCs, however, is challenging, and therefore, most studies using MSCs as therapeutic cell carriers have utilized viral vectors to transduce the cells. Here, we demonstrate, for the first time, an alternative approach for the efficient transfection of MSCs; therapeutic ultrasound (TUS). Using TUS with low intensities and moderate frequencies, MSCs were transfected with a pDNA encoding for PEX, a protein that inhibits tumor angiogenesis, and studied as a cell vehicle for in vivo tumor therapy. TUS application did not alter the MSCs' stemness or their homing capabilities, and the transfected MSCs transcribed biologically active PEX. Additionally, in a mouse model, 70% inhibition of prostate tumor growth was achieved following a single I.V. administration of MSCs that were TUS-transfected with pPEX. Further, the repeated I.V. administration of TUS-pPEX transfected-MSCs enhanced tumor inhibition up to 84%. Altogether, these results provide a proof of concept that TUS-transfected MSCs can be effectively used as a cell-based delivery approach for the prospective treatment of cancer.

Is Stem Cell Therapy Ready for Prime Time in Treatment of Inflammatory Bowel Diseases?

Autologous hematopoietic stem cell transplantation (HSCT) and mesenchymal stromal cell therapy have been proposed for patients with refractory Crohn's disease (CD) and fistulizing CD, respectively. Will these highly advanced techniques be available only for select patients, at specialized centers, or is further clinical development justified, with the aim of offering widespread, more definitive therapeutic options for often very difficult to treat disease? Patients with CD who are eligible for HSCT have typically been failed by most approved therapies, have undergone multiple surgeries, and have coped with years of disease activity and poor quality of life. The objective of HSCT is to immediately shut down the immune response and allow the transplanted stem cells to develop into self-tolerant lymphocytes. For patients with fistulizing CD, mesenchymal stromal cell therapy deposits MSCs locally, into fistulizing tracts, to down-regulate the local immune response and induce wound healing. Recent trials have produced promising results for HSCT and mesenchymal stromal cell therapy as alternatives to systemic therapies and antibiotics for patients with inflammatory bowel diseases, but are these immunotherapies ready for prime time?

Tracking stem cells with superparamagnetic iron oxide nanoparticles: perspectives and considerations

Superparamagnetic iron oxide nanoparticles (SPIONs) have been used for diagnoses in biomedical applications, due to their unique properties and their apparent safety for humans. In general, SPIONs do not seem to produce cell damage, although their long-term in vivo effects continue to be investigated. The possibility of efficiently labeling cells with these magnetic nanoparticles has stimulated their use to noninvasively track cells by magnetic resonance imaging after transplantation. SPIONs are attracting increasing attention and are one of the preferred methods for cell labeling and tracking in preclinical and clinical studies. For clinical protocol approval of magnetic-labeled cell tracking, it is essential to expand our knowledge of the time course of SPIONs after cell incorporation and transplantation. This review focuses on the recent advances in tracking SPION-labeled stem cells, analyzing the possibilities and limitations of their use, not only focusing on myocardial infarction but also discussing other models.

Organic Nanoparticles with Aggregation-Induced Emission for Bone Marrow Stromal Cell Tracking in a Rat PTI Model

Stem-cell based therapy is an emerging therapeutic approach for ischemic stroke treatment. Bone marrow stromal cells (BMSCs) are in common use as a cell source for stem cell therapy and show promising therapeutic outcomes for stroke treatment. One challenge is to develop a reliable tracking strategy to monitor the fate of BMSCs and assess their therapeutic effects in order to improve the success rate of such treatment. Herein, TPEEP, a fluorogen with aggregation-induced emission characteristics and near-infrared emission are designed and synthesized and further fabricated into organic nanoparticles (NPs). The obtained NPs show high fluorescence quantum yield, low cytotoxicity with good physical and photostability, which display excellent tracking performance of BMSCs in vitro and in vivo. Using a rat photothrombotic ischemia model as an example, the NP-labeled BMSCs are able to migrate to the stroke lesion site to yield bright red fluorescence. Immunofluorescence staining shows that the NP labeling does not affect the normal function of BMSCs, proving their good biocompatibility in vivo. These merits make TPEEP NP a potential cell tracker to evaluate the fate of BMSCs in cell therapy.

Gold Nanoparticles as a Potential Cellular Probe for Tracking of Stem Cells in Bone Regeneration Using Dual-Energy Computed Tomography

Transplant of bone marrow mesenchymal stem cells (BMSCs) has attracted considerable interest for bone regeneration. However, noninvasive and real-time tracking of location and concentration of the implanted BMSCs remains a big challenge. Herein we designed a novel approach involving the surface modification of gold nanoparticles (AuNPs) with silica layers and DNA Transfectin 3000 (TS) to improve biocompatibility and to enhance the uptake by BMSCs, hence rendering the ability of tracking BMSCs with dual-energy computer tomography (DECT). Results showed that the endocytosis of AuNPs@SiO₂-TS by BMSCs was as high as ∼255 pg/cell after one-day incubation and did not obviously decrease after 14 days. Meanwhile, the AuNPs@SiO₂-TS had no influence on the viability, cell cycle, and capabilities on osteogenic, chondrogenic, and adipogenic differentiation of BMSCs. Under a bone-defect rabbit model, the DECT images showed the migration of BMSCs toward a cortical bone defect without variation in volume. This study demonstrated that AuNPs@SiO₂-TS could be a potential cellular probe for noninvasive and real-time tracking of BMSCs in bone tissue repairs using clinical CT or DECT techniques. It provided a novel and intuitive methodology for observing and investigating the bone regeneration in clinic.

Human mesenchymal stromal cells undergo apoptosis and fragmentation after intravenous application in immune-competent mice

BACKGROUND AIMS

The biodistribution of human MSCs after systemic delivery is incompletely understood. We investigated the changes in cell size and cell surface markers of human MSCs after intravenous (IV) injection in immune competent mice.

METHODS

Male human MSCs were labeled with fluorescent vital dye PKH67 and tracked after IV administration in C57/BL6 mice. MSCs were tracked in blood and different murine tissues by human SRY gene quantitative polymerase chain reaction (qPCR) analysis, flow cytometry and fluorescence microscopy. Calibrated microbeads were used to track the size of transplanted MSCs.

RESULTS

The majority of injected MSCs were detected by qPCR in the lungs 5 min after transplantation, whereas <0.1% were detected in other tissues over 24 h. Flow cytometric and fluorescence microscopic analysis indicated that MSCs continuously decreased in size after transplantation and underwent fragmentation. The majority of PKH⁺ MSCs and their fragments were found in lungs and liver. PKH⁺ MSCs rapidly became positive for annexin V, propidium iodide and calreticulin, indicating loss of cell integrity. In addition, PKH⁺ fragments co-stained with antibodies against C3b, F4/80 and/or GR-1 indicating opsonization. Preincubation of MSCs in hyperosmolaric hydroxyethyl starch (HyperHAES) decreased MSCs size before transplantation, delayed the loss of viability markers and increased the frequency of traceable MSCs up to 24 h after transplantation.

CONCLUSIONS

PKH67 labeled MSCs are fragmented after IV injection in mice, acquire apoptotic and phagocytic cell markers and accumulate in the lungs and liver.

Tracking mesenchymal stem cells using magnetic resonance imaging

Recent translational studies in the fields of tissue regeneration and cell therapy have characterized mesenchymal stem cells (MSCs) as a potentially effective and accessible measure for treating ischemic cerebral and neurodegenerative disorders such as stroke, Parkinson's disease, and amyotrophic lateral sclerosis. Developing more efficient cell tracking techniques bear the potential to optimize MSC transplantation therapies by providing a more accurate picture of the fate and area of effect of implanted cells. Currently, determining the location of transplanted MSCs involves a histological approach, but magnetic resonance imaging (MRI) presents a noninvasive paradigm that permits repeat evaluations. To visualize MSCs using MRI, the implanted cells must be treated with an intracellular contrast agent. These are commonly paramagnetic compounds, many of which are based on superparamagnetic iron oxide (SPIO) nanoparticles. Recent research has set out characterize the effects of SPIO-uptake on the cellular activity of in vitro human MSCs and the resultant influence that respective SPIO concentration has on MRI sensitivity. As these studies reveal, SPIO-uptake has no effect on the cellular processes of proliferation and differentiation while producing high contrast MRI signals. Moreover, transplantation of SPIO-labeled MSCs in animal models encouragingly showed no loss in MRI contrast, suggesting that SPIO labeling may be an appealing regime for lasting MRI detection. This study is a review article. Referred literature in this study has been listed in the reference part. The datasets supporting the conclusions of this article are available online by searching the PubMed. Some original points in this article come from the laboratory practice in our research centers and the authors’ experiences.

Arrhythmogenesis: a Roadblock to Cardiac Stem Cell Therapy

OPINION STATEMENT

Despite significant advances in the treatment of ischemic heart disease (IHD), it remains the leading cause of mortality worldwide. Undoubtedly, methods for regenerating the injured human heart are urgently needed, and whilst exciting progress has been made from utilizing stem cell therapy for cardiac regeneration, several major challenges still remain. In particular, one major safety issue is the occurrence of potentially life-threatening ventricular arrhythmias after cell therapy. Several drivers may be responsible for this, ranging from the potential inherent arrhythmogenicity of delivered stem cells to that of the underlying IHD. Therefore, it is imperative to thoroughly assess the risk-to-benefit ratio of such treatments prior to the clinical application. As such, despite the considerable progress made in stem cell therapy over the past decades, many obstacles still lie ahead.

Human Mesenchymal Stromal Cells Improve Cardiac Perfusion in an Ovine Immunocompetent Animal Model

BACKGROUND

Mesenchymal stromal cells (MSCs) hold considerable promise in the treatment of ischemic heart disease. Most preclinical studies of MSCs for acute myocardial infarction (AMI) have been performed either in syngeneic animal models or with human cells in xenogeneic immunodeficient animals. A preferable pre-clinical model, however, would involve human MSCs in an immunocompetent animal.

METHODS

AMI was generated in adult sheep by inducing ischemia reperfusion of the second diagonal branch. Sheep (n = 10) were randomized to receive an intravenous injection of human MSCs (1 × 10(6) cells/kg) or phosphate buffered saline. Cardiac function and remodeling were evaluated with echocardiography. Perfusion scintigraphy was used to identify sustained myocardial ischemia. Interaction between human MSCs and ovine lymphocytes was assessed by a mixed lymphocyte response (MLR).

RESULTS

Sheep receiving human MSCs showed significant improvement in myocardial perfusion at 1 month compared with baseline measurements. There was no change in ventricular dimensions in either group after 1 month of AMI. No adverse events or symptoms were observed in the sheep receiving human MSCs. The MLR was negative.

CONCLUSION

The immunocompetent ovine AMI model demonstrates the clinical safety and efficacy of human MSCs. The human cells do not appear to be immunogenic, further suggesting that immunocompetent sheep may serve as a suitable pre-clinical large animal model for testing human MSCs.

Upconversion Nanoparticles for Bioimaging and Regenerative Medicine

Nanomaterials are proving useful for regenerative medicine in combination with stem cell therapy. Nanoparticles (NPs) can be administrated and targeted to desired tissues or organs and subsequently be used in non-invasive real-time visualization and tracking of cells by means of different imaging techniques, can act as therapeutic agent nanocarriers, and can also serve as scaffolds to guide the growth of new tissue. NPs can be of different chemical nature, such as gold, iron oxide, cadmium selenide, and carbon, and have the potential to be used in regenerative medicine. However, there are still many issues to be solved, such as toxicity, stability, and resident time. Upconversion NPs have relevant properties such as (i) low toxicity, (ii) capability to absorb light in an optical region where absorption in tissues is minimal and penetration is optimal (note they can also be designed to emit in the near-infrared region), and (iii) they can be used in multiplexing and multimodal imaging. An overview on the potentiality of upconversion materials in regenerative medicine is given.

Co-Registration of Bioluminescence Tomography, Computed Tomography, and Magnetic Resonance Imaging for Multimodal In Vivo Stem Cell Tracking

We present a practical approach for coregistration of bioluminescence tomography (BLT), computed tomography (CT), and magnetic resonance (MR) images. For this, we developed a customized animal shuttle composed of nonfluorescent, MR-compatible Delrin plastic that fits a commercially available MR surface coil. Mouse embryonic stem cells were transfected with the luciferase gene and labeled with superparamagnetic iron oxide nanoparticles. Cells were stereotaxically implanted in the mouse brain and imaged weekly for 4 weeks with bioluminescent imaging (IVIS Spectrum CT scanner) and magnetic resonance imaging (MRI; 11.7 T horizontal bore scanner). Without the use of software coregistration, in vitro phantom studies yielded root-mean-square errors of 7.6 × 10⁻³, 0.93 mm, and 0.78 mm along the medial–lateral (ML), dorsal–ventral (DV), and anterior–posterior (AP) axes, respectively. Rotation errors were negligible. Software coregistration by translation along the DV and AP axes resulted in consistent agreement between the CT and MR images, without the need for rotation or warping. In vivo coregistered BLT/MRI mouse brain data sets showed a single diffuse region of bioluminescent imaging photon signal and MRI hypointensity. Over time, the transplanted cells formed tumors as histopathologically validated. Disagreement between BLT and MRI tumor location was greatest along the DV axis (1.4 ± 0.2 mm) than along the ML (0.5 ± 0.3 mm) and the AP axes (0.6 mm) because of the uncertainty of the depth of origin of the BLT signal. Combining the high spatial anatomical information of MRI with the cell viability/proliferation data from BLT should facilitate preclinical evaluation of novel therapeutic candidate stem cells.

Study of the Effect of Route of Administration of Mesenchymal Stem Cells on Cisplatin-Induced Acute Kidney Injury in Sprague Dawley Rats

BACKGROUND AND OBJECTIVES

Mesenchymal stem cells (MSCs) have been shown to ameliorate cisplatin-induced acute kidney injury (AKI). The present study compares the efficacy of different routes of MSCs administration on kidney damage and regeneration after cisplatin-induced AKI.

METHODS

A single intraperitoneal injection of cisplatin (5 mg/kg) was used to induce AKI in 160 rats. MSCs (5×10⁶) were given by either intravenous, intra-arterial or kidney sub capsular injection one day after cisplatin injection. Suitable control groups were included. Rats were sacrificed at 4, 7, 11 and 30 days after cisplatin injection. Kidney function parameters, kidney tissue oxidative stress markers, and scoring for renal tissue injury, regeneration and chronicity were all determined.

RESULTS

MSCs by any routes were able to ameliorate kidney function deterioration and renal tissue damage induced by cisplatin. The overall results of the three routes were equal. Differences between the different routes in one parameter were transient and inconsistent with other parameters.

CONCLUSIONS

Changing the route of MSCs injection does not have a major influence on the outcome. Future evaluation should focus on differences between the routes of administration considering the long term safety.

Human amniotic fluid stem cells labeled with up-conversion nanoparticles for imaging-monitored repairing of acute lung injury

Human amniotic fluid stem (hAFS) cells have generated a great deal of excitement in cell-based therapies and regenerative medicine. Here, we examined the effect of hAFS cells labeled with dual-polymer-coated UCNP-PEG-PEI nanoparticles in a murine model of acute lung injury (ALI). We observed hAFS cells migration to the lung using highly sensitive in vivo upconversion luminescence (UCL) imaging. We demonstrated that hAFS cells remained viable and retained their ability to differentiate even after UCNP-PEG-PEI labeling. More importantly, hAFS cells displayed remarkable positive effects on ALI-damaged lung tissue repair compared with mouse bone marrow mesenchymal stem cells (mBMSCs), which include recovery of the integrity of alveolar-capillary membrane, attenuation of transepithelial leukocyte and neutrophil migration, and down-regulation of proinflammatory cytokine and chemokine expression. Our work highlights a promising role for imaging-guided hAFS cell-based therapy in ALI.

Extracellular Vesicles in Physiology, Pathology, and Therapy of the Immune and Central Nervous System, with Focus on Extracellular Vesicles Derived from Mesenchymal Stem Cells as Therapeutic Tools

Extracellular vesicles (EVs) are membrane-surrounded structures released by most cell types. They are characterized by a specific set of proteins, lipids and nucleic acids. EVs have been recognized as potent vehicles of intercellular communication to transmit biological signals between cells. In addition, pathophysiological roles of EVs in conditions like cancer, infectious diseases and neurodegenerative disorders are well established. In recent years focus has been shifted on therapeutic use of stem cell derived-EVs. Use of stem cell derived-EVs present distinct advantage over the whole stem cells as EVs do not replicate and after intravenous administration, they are less likely to trap inside the lungs. From the therapeutic perspective, the most promising cellular sources of EVs are mesenchymal stem cells (MSCs), which are easy to obtain and maintain. Therapeutic activity of MSCs has been shown in numerous animal models and the beneficial paracrine effect of MSCs may be mediated by EVs. The various components of MSC derived-EVs such as proteins, lipids, and RNA might play a specific therapeutic role. In this review, we characterize the role of EVs in immune and central nervous system (CNS); present evidences for defective signaling of these vesicles in neurodegeneration and therapeutic role of EVs in CNS.

Designing Biopolymer Microthreads for Tissue Engineering and Regenerative Medicine

Native tissue structures possess elaborate extracellular matrix (ECM) architectures that inspire the design of fibrous structures in the field of regenerative medicine. We review the literature with respect to the successes and failures, as well as the future promise of biopolymer microthreads as scaffolds to promote endogenous and exogenous tissue regeneration. Biomimetic microthread tissue constructs have been proposed for the functional regeneration of tendon, ligament, skeletal muscle, and ventricular myocardial tissues. To date, biopolymer microthreads have demonstrated promising results as materials to recapitulate the hierarchical structure of simple and complex tissues and well as biochemical signaling cues to direct cell-mediated tissue regeneration. Biopolymer microthreads have also demonstrated exciting potential as a platform technology for the targeted delivery of stem cells and therapeutic molecules. Future studies will focus on the design of microthread-based tissue analogs that strategically integrate growth factors and progenitor cells to temporally direct cell-mediated processes that promote enhanced functional tissue regeneration.

Labeling of mesenchymal stem cells for MRI with single-cell sensitivity

Sensitive cell detection by magnetic resonance imaging (MRI) is an important tool for the development of cell therapies. However, clinically approved contrast agents that allow single-cell detection are currently not available. Therefore, we compared very small iron oxide nanoparticles (VSOP) and new multicore carboxymethyl dextran-coated iron oxide nanoparticles (multicore particles, MCP) designed by our department for magnetic particle imaging (MPI) with discontinued Resovist^® regarding their suitability for detection of single mesenchymal stem cells (MSC) by MRI. We achieved an average intracellular nanoparticle (NP) load of >10 pg Fe per cell without the use of transfection agents. NP loading did not lead to significantly different results in proliferation, colony formation, and multilineage in vitro differentiation assays in comparison to controls. MRI allowed single-cell detection using VSOP, MCP, and Resovist^® in conjunction with high-resolution T2*-weighted imaging at 7 T with postprocessing of phase images in agarose cell phantoms and in vivo after delivery of 2,000 NP-labeled MSC into mouse brains via the left carotid artery. With optimized labeling conditions, a detection rate of ~45% was achieved; however, the experiments were limited by nonhomogeneous NP loading of the MSC population. Attempts should be made to achieve better cell separation for homogeneous NP loading and to thus improve NP-uptake-dependent biocompatibility studies and cell detection by MRI and future MPI. Additionally, using a 7 T MR imager equipped with a cryocoil resulted in approximately two times higher detection. In conclusion, we established labeling conditions for new high-relaxivity MCP, VSOP, and Resovist^® for improved MRI of MSC with single-cell sensitivity.

In Vivo Tracking of Cell Therapies for Cardiac Diseases with Nuclear Medicine

Even though heart diseases are amongst the main causes of mortality and morbidity in the world, existing treatments are limited in restoring cardiac lesions. Cell transplantations, originally developed for the treatment of hematologic ailments, are presently being explored in preclinical and clinical trials for cardiac diseases. Nonetheless, little is known about the possible efficacy and mechanisms for these therapies and they are the center of continuous investigation. In this scenario, noninvasive imaging techniques lead to greater comprehension of cell therapies. Radiopharmaceutical cell labeling, firstly developed to track leukocytes, has been used successfully to evaluate the migration of cell therapies for myocardial diseases. A substantial rise in the amount of reports employing this methodology has taken place in the previous years. We will review the diverse radiopharmaceuticals, imaging modalities, and results of experimental and clinical studies published until now. Also, we report on current limitations and potential advances of radiopharmaceutical labeling for cell therapies in cardiac diseases.

Biodistribution, migration and homing of systemically applied mesenchymal stem/stromal cells

Mesenchymal stem/stromal cells (MSCs) are increasingly used as an intravenously applied cellular therapeutic. They were found to be potent in situations such as tissue repair or severe inflammation. Still, data are lacking with regard to the biodistribution of MSCs, their cellular or molecular target structures, and the mechanisms by which MSCs reach these targets. This review discusses current hypotheses for how MSCs can reach tissue sites. Both preclinical and clinical studies using MSCs applied intravenously or intra-arterially are discussed in the context of our current understanding of how MSCs might work in physiological and pathological situations.

Cross effects of resveratrol and mesenchymal stem cells on liver regeneration and homing in partially hepatectomized rats

In this study, we examined the effect of preoperatively administered resveratrol (RV) and mesenchymal stem cells (MSCs) on regeneration of partially hepatectomized rat liver. We also evaluated the effect of RV on homing of MSCs. MSCs were isolated from bone marrow and cultured in vitro. Wistar albino rats were randomly divided into four groups. In groups, rats received (1) no treatment, (2) single dose RV, (3) MSCs and (4) RV plus MSCs before partial hepatectomy (PH). Injected MSCs were traced by labeling them with green fluorescent protein, and liver regeneration was determined by comparison of liver weight gain, histological examination and immunohistochemical staining with proliferating cell nuclear antigen (PCNA) for mitotic cells. The expression levels of tumor necrosis factor -alpha (TNF-α), interleukin-6 (IL-6) and hepatocyte growth factor (HGF) were also determined in the parafin sections of liver specimens with immunohistochemical staining. Administration of RV and MSCs separately or together enhanced liver regeneration despite decreasing the TNF-α and IL-6 expression. This positive contribution was probably due to direct raising effect on HGF for RV and HGF expression for MSCs that we demonstrated with immunohistochemical staining. Additionally, RV increased the homing of MSCs in liver probably related to life prolonging effect on MSCs. These results indicate that preoperative RV as well as MSCs application enhances liver regeneration after partial hepatectomy in rats. Paying attention to RV about the effect on liver regeneration and homing of MSCs might be the goal of further investigations.

Quantitative Magnetic Particle Imaging Monitors the Transplantation, Biodistribution, and Clearance of Stem Cells In Vivo

Stem cell therapies have enormous potential for treating many debilitating diseases, including heart failure, stroke and traumatic brain injury. For maximal efficacy, these therapies require targeted cell delivery to specific tissues followed by successful cell engraftment. However, targeted delivery remains an open challenge. As one example, it is common for intravenous deliveries of mesenchymal stem cells (MSCs) to become entrapped in lung microvasculature instead of the target tissue. Hence, a robust, quantitative imaging method would be essential for developing efficacious cell therapies. Here we show that Magnetic Particle Imaging (MPI), a novel technique that directly images iron-oxide nanoparticle-tagged cells, can longitudinally monitor and quantify MSC administration in vivo. MPI offers near-ideal image contrast, depth penetration, and robustness; these properties make MPI both ultra-sensitive and linearly quantitative. Here, we imaged, for the first time, the dynamic trafficking of intravenous MSC administrations using MPI. Our results indicate that labeled MSC injections are immediately entrapped in lung tissue and then clear to the liver within one day, whereas standard iron oxide particle (Resovist) injections are immediately taken up by liver and spleen. Longitudinal MPI-CT imaging also indicated a clearance half-life of MSC iron oxide labels in the liver at 4.6 days. Finally, our ex vivo MPI biodistribution measurements of iron in liver, spleen, heart, and lungs after injection showed excellent agreement (R² = 0.943) with measurements from induction coupled plasma spectrometry. These results demonstrate that MPI offers strong utility for noninvasively imaging and quantifying the systemic distribution of cell therapies and other therapeutic agents.

Upconversion Nanoparticles for Bioimaging and Regenerative Medicine

Nanomaterials are proving useful for regenerative medicine in combination with stem cell therapy. Nanoparticles (NPs) can be administrated and targeted to desired tissues or organs and subsequently be used in non-invasive real-time visualization and tracking of cells by means of different imaging techniques, can act as therapeutic agent nanocarriers, and can also serve as scaffolds to guide the growth of new tissue. NPs can be of different chemical nature, such as gold, iron oxide, cadmium selenide, and carbon, and have the potential to be used in regenerative medicine. However, there are still many issues to be solved, such as toxicity, stability, and resident time. Upconversion NPs have relevant properties such as (i) low toxicity, (ii) capability to absorb light in an optical region where absorption in tissues is minimal and penetration is optimal (note they can also be designed to emit in the near-infrared region), and (iii) they can be used in multiplexing and multimodal imaging. An overview on the potentiality of upconversion materials in regenerative medicine is given.

Dynamic In Vivo SPECT Imaging of Neural Stem Cells Functionalized with Radiolabeled Nanoparticles for Tracking of Glioblastoma

There is strong clinical interest in using neural stem cells (NSCs) as carriers for targeted delivery of therapeutics to glioblastoma. Multimodal dynamic in vivo imaging of NSC behaviors in the brain is necessary for developing such tailored therapies; however, such technology is lacking. Here we report a novel strategy for mesoporous silica nanoparticle (MSN)-facilitated NSC tracking in the brain via SPECT.

METHODS

(111)In was conjugated to MSNs, taking advantage of the large surface area of their unique porous feature. A series of nanomaterial characterization assays was performed to assess the modified MSN. Loading efficiency and viability of NSCs with (111)In-MSN complex were optimized. Radiolabeled NSCs were administered to glioma-bearing mice via either intracranial or systemic injection. SPECT imaging and bioluminescence imaging were performed daily up to 48 h after NSC injection. Histology and immunocytochemistry were used to confirm the findings.

RESULTS

(111)In-MSN complexes show minimal toxicity to NSCs and robust in vitro and in vivo stability. Phantom studies demonstrate feasibility of this platform for NSC imaging. Of significance, we discovered that decayed (111)In-MSN complexes exhibit strong fluorescent profiles in preloaded NSCs, allowing for ex vivo validation of the in vivo data. In vivo, SPECT visualizes actively migrating NSCs toward glioma xenografts in real time after both intracranial and systemic administrations. This is in agreement with bioluminescence live imaging, confocal microscopy, and histology.

CONCLUSION

These advancements warrant further development and integration of this technology with MRI for multimodal noninvasive tracking of therapeutic NSCs toward various brain malignancies.

Genetically engineered mesenchymal stem cell therapy using self-assembling supramolecular hydrogels

Stem cell therapy has attracted a great deal of attention for treating intractable diseases such as cancer, stroke, liver cirrhosis, and ischemia. Especially, mesenchymal stem cells (MSCs) have been widely investigated for therapeutic applications due to the advantageous characteristics of long life-span, facile isolation, rapid proliferation, prolonged transgene expression, hypo-immunogenicity, and tumor tropism. MSCs can exert their therapeutic effects by releasing stress-induced therapeutic molecules after their rapid migration to damaged tissues. Recently, to improve the therapeutic efficacy, genetically engineered MSCs have been developed for therapeutic transgene expression by viral gene transduction and non-viral gene transfection. In general, the number of therapeutic cells for injection should be more than several millions for effective cell therapy. Adequate carriers for the controlled delivery of MSCs can reduce the required cell numbers and extend the duration of therapeutic effect, which provide great benefits for chronic disease patients. In this review, we describe genetic engineering of MSCs, recent progress of self-assembling supramolecular hydrogels, and their applications to cell therapy for intractable diseases and tissue regeneration.

Intracarotid Infusion of Mesenchymal Stem Cells in an Animal Model of Parkinson's Disease, Focusing on Cell Distribution and Neuroprotective and Behavioral Effects

Mesenchymal stem cells (MSCs) have been proposed as a potential therapeutic tool for Parkinson's disease (PD) and systemic administration of these cells has been tested in preclinical and clinical studies. However, no information on survival and actual capacity of MSCs to reach the brain has been provided. In this study, we evaluated homing of intraarterially infused rat MSCs (rMSCs) in the brain of rats bearing a 6-hydroxydopamine (6-OHDA)-induced lesion of the nigrostriatal tract, to establish whether the toxin-induced damage is sufficient to grant MSC passage across the blood-brain barrier (BBB) or if a transient BBB disruption is necessary. The rMSC distribution in peripheral organs and the effects of cell infusion on neurodegenerative process and motor deficits were also investigated. rMSCs were infused 14 days after 6-OHDA injection. A hyperosmolar solution of mannitol was used to transiently permeabilize the BBB. Behavioral impairment was assessed by adjusting step test and response to apomorphine. Animals were sacrificed 7 and 28 days after cell infusion. Our work shows that appreciable delivery of rMSCs to the brain of 6-OHDA-lesioned animals can be obtained only after mannitol pretreatment. A notable percentage of infused cells accumulated in peripheral organs. Infusion of rMSCs did not modify the progression of 6-OHDA-induced damage or the motor impairment at the stepping test, but induced progressive normalization of the pathological response (contralateral turning) to apomorphine administration. These findings suggest that many aspects should be further investigated before considering any translation of MSC systemic administration into the clinical setting for PD treatment.

SIGNIFICANCE

This study demonstrates that mesenchymal stem cells infused through the carotid artery do not efficiently cross the blood-brain barrier in rats with a Parkinson's disease-like degeneration of nigrostriatal neurons, unless a permeabilizing agent (e.g., mannitol) is used. The infusion did not reduce the neuronal damage and associated motor impairment, but abolished the motor abnormalities these animals typically show when challenged with a dopaminergic agonist. Therefore, although arterially infused mesenchymal stem cells did not show neurorestorative effects in this study's Parkinson's disease model, they appeared to normalize the pathological responsiveness of striatal neurons to dopaminergic stimulation. This capability should be further explored in future studies.

Translational applications of molecular imaging in cardiovascular disease and stem cell therapy

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity worldwide. Molecular imaging techniques provide valuable information at cellular and molecular level, as opposed to anatomical and structural layers acquired from traditional imaging modalities. More specifically, molecular imaging employs imaging probes which interact with specific molecular targets and therefore makes it possible to visualize biological processes in vivo. Molecular imaging technology is now progressing towards preclinical and clinical application that gives an integral and comprehensive guidance for the investigation of cardiovascular disease. In addition, cardiac stem cell therapy holds great promise for clinical translation. Undoubtedly, combining stem cell therapy with molecular imaging technology will bring a broad prospect for the study and treatment of cardiac disease. This review will focus on the progresses of molecular imaging strategies in cardiovascular disease and cardiac stem cell therapy. Furthermore, the perspective on the future role of molecular imaging in clinical translation and potential strategies in defining safety and efficacy of cardiac stem cell therapies will be discussed.

Antigen-Loaded Upconversion Nanoparticles for Dendritic Cell Stimulation, Tracking, and Vaccination in Dendritic Cell-Based Immunotherapy

A dendritic cell (DC) vaccine, which is based on efficient antigen delivery into DCs and migration of antigen-pulsed DCs to draining lymph nodes after vaccination, is an effective strategy in initiating CD8(+) T cell immunity for immunotherapy. Herein, antigen-loaded upconversion nanoparticles (UCNPs) are used to label and stimulate DCs, which could be precisely tracked after being injected into animals and induce an antigen-specific immune response. It is discovered that a model antigen, ovalbumin (OVA), could be adsorbed on the surface of dual-polymer-coated UCNPs via electrostatic interaction, forming nanoparticle-antigen complexes, which are efficiently engulfed by DCs and induce DC maturation and cytokine release. Highly sensitive in vivo upconversion luminescence (UCL) imaging of nanoparticle-labeled DCs is successfully carried out, observing the homing of DCs to draining lymph nodes after injection. In addition, strong antigen-specific immune responses including enhanced T cell proliferation, interferon gamma (IFN-γ) production, and cytotoxic T lymphocyte (CTL)-mediated responses are induced by a nanoparticle-pulsed DC vaccine, which is promising for DC-based immunotherapy potentially against cancer.

Intravenous administration of atorvastatin-pretreated mesenchymal stem cells improves cardiac performance after acute myocardial infarction: role of CXCR4

BACKGROUND

The interaction between stromal cell-derived factor 1 (SDF-1) and its receptor CXC chemokine receptor 4 (CXCR4) plays an important role in mesenchymal stem cells (MSCs) migration and engraftment. Statins can increase the survival of MSCs. However, whether statins could enhance MSCs migration and engraftment is still unknown. Therefore, we designed the study to investigate whether atorvastatin (ATV) could enhance CXCR4 expression of MSCs and promote them homing toward the injured myocardium.

METHODS AND RESULTS

Expression of CXCR4 was evaluated by flow cytometry and real time PCR. A transwell system was used to assess MSCs migration ability. Recruitment of systematically delivered MSCs to the infarcted heart was evaluated in Sprague-Dawley rats with acute myocardial infarction (AMI). ATV pretreatment enhanced the expression of CXCR4 and stimulated MSCs migration in vitro. However, the effect was largely abolished by CXCR4 neutralizing antibody. In AMI models, we found much more ATV-pretreated MSCs homing toward the infarcted myocardium than non-treated cells and this was accompanied by improved cardiac performance.

CONCLUSIONS

ATV increases the migration ability of MSCs and improves cardiac performance due to up-regulated expression of CXCR4. These results suggest that ATV pretreatment of donor MSCs is an effective way to promote cell therapeutic potential for AMI.

In vivo tracking of human placenta derived mesenchymal stem cells in nude mice via ¹⁴C-TdR labeling

BACKGROUND

In order to shed light on the regenerative mechanism of mesenchymal stem cells (MSCs) in vivo, the bio-distribution profile of implanted cells using a stable and long-term tracking method is needed. We herein investigated the bio-distribution of human placental deciduas basalis derived MSCs (termed as PDB-MSCs) in nude mice after intravenous injection by carbon radioisotope labeling thymidine ((14)C-TdR), which is able to incorporate into new DNA strands during cell replication.

RESULTS

The proliferation rate and radioactive emission of human PDB-MSCs after labeled with different concentrations of (14)C-TdR were measured. PDB-MSCs labeled with 1 μCi possessed high radioactivity, and the biological characteristics (i.e. morphology, colony forming ability, differentiation capabilities, karyotype and cell cycle) showed no significant changes after labeling. Thus, 1 μCi was the optimal concentration in this experimental design. In nude mice, 1 × 10(6) (14)C-TdR-labeled PDB-MSCs were injected intravenously and the organs were collected at days 1, 2, 3, 5, 30 and 180 after injection, respectively. Radiolabeled PDB-MSCs were found mainly in the lung, liver, spleen, stomach and left femur of the recipient nude mice at the whole observation period.

CONCLUSIONS

This work provided solid evidence that (14)C-TdR labeling did not alter the biological characteristics of human placental MSCs, and that this labeling method has potential to decrease the signal from non-infused or dead cells for cell tracking. Therefore, this labeling technique can be utilized to quantify the infused cells after long-term follow-up in pre-clinical studies.

Intra-arterial Administration of Placenta-Derived Decidual Stromal Cells to the Superior Mesenteric Artery in the Rabbit: Distribution of Cells, Feasibility, and Safety

Selective administration of mesenchymal stromal cells to the mesenteric arteries is a potential technique to overcome pulmonary trapping and increase the density of transplanted cells in extensive mural inflammation of the intestine, such as in inflammatory bowel disease and graft-versus-host disease. We injected 5 × 10(6) (111)In-oxine-labeled human decidual stromal cells (DSCs) to the rabbit superior mesenteric artery (SMA) using clinical routine catheters guided by an angiographical system under sterile conditions. We used longitudinal single-photon emission tomography at 6 h and at 1, 2, and 5 days to assess trafficking and distribution of DSCs. We used digital subtraction angiography, computed tomography, and hematoxylin and eosin stainings to determine biodistribution of cells and to assess safety end points. We found that selective injection of human DSCs to the rabbit SMA does not result in acute embolic complications. Furthermore, we found that IV administration resulted in extensive retention of the radiolabeled DSCs in the lungs, corroborating previous studies on pulmonary trapping. In sharp contrast, selective injections to the SMA resulted in uptake distributed in the intestine supplied by the SMA and in the liver, indicating that this approach could significantly increase the fraction of injected DSCs reaching the target tissue.

Ultrasound-Targeted Microbubble Destruction Improves the Migration and Homing of Mesenchymal Stem Cells after Myocardial Infarction by Upregulating SDF-1/CXCR4: A Pilot Study

Mesenchymal stem cell (MSC) therapy shows considerable promise for the treatment of myocardial infarction (MI). However, the inefficient migration and homing of MSCs after systemic infusion have limited their therapeutic applications. Ultrasound-targeted microbubble destruction (UTMD) has proven to be promising to improve the homing of MSCs to the ischemic myocardium, but the concrete mechanism remains unclear. We hypothesize that UTMD promotes MSC homing by upregulating SDF-1/CXCR4, and this study was aimed at exploring this potential mechanism. We analyzed SDF-1/CXCR4 expression after UTMD treatment in vitro and in vivo and counted the number of homing MSCs in MI areas. The in vitro results demonstrated that UTMD not only led to elevated secretion of SDF-1 but also resulted in an increased proportion of MSCs that expressed surface CXCR4. The in vivo findings show an increase in the number of homing MSCs and higher expression of SDF-1/CXCR4 in the UTMD combined with MSCs infusion group compared to other groups. In conclusion, UTMD can increase SDF-1 expression in the ischemic myocardium and upregulate the expression of surface CXCR4 on MSCs, which provides a molecular mechanism for the homing of MSCs assisted by UTMD via SDF-1/CXCR4 axis.

Tracking fusion of human mesenchymal stem cells after transplantation to the heart

Evidence suggests that transplanted mesenchymal stem cells (MSCs) can aid recovery of damaged myocardium caused by myocardial infarction. One possible mechanism for MSC-mediated recovery is reprogramming after cell fusion between transplanted MSCs and recipient cardiac cells. We used a Cre/LoxP-based luciferase reporter system coupled to biophotonic imaging to detect fusion of transplanted human pluripotent stem cell-derived MSCs to cells of organs of living mice. Human MSCs, with transient expression of a viral fusogen, were delivered to the murine heart via a collagen patch. At 2 days and 1 week later, living mice were probed for bioluminescence indicative of cell fusion. Cell fusion was detected at the site of delivery (heart) and in distal tissues (i.e., stomach, small intestine, liver). Fusion was confirmed at the cellular scale via fluorescence in situ hybridization for human-specific and mouse-specific centromeres. Human cells in organs distal to the heart were typically located near the vasculature, suggesting MSCs and perhaps MSC fusion products have the ability to migrate via the circulatory system to distal organs and engraft with local cells. The present study reveals previously unknown migratory patterns of delivered human MSCs and associated fusion products in the healthy murine heart. The study also sets the stage for follow-on studies to determine the functional effects of cell fusion in a model of myocardial damage or disease.

SIGNIFICANCE

Mesenchymal stem cells (MSCs) are transplanted to the heart, cartilage, and other tissues to recover lost function or at least limit overactive immune responses. Analysis of tissues after MSC transplantation shows evidence of fusion between MSCs and the cells of the recipient. To date, the biologic implications of cell fusion remain unclear. A newly developed in vivo tracking system was used to identify MSC fusion products in living mice. The migratory patterns of fusion products were determined both in the target organ (i.e., the heart) and in distal organs. This study shows, for the first time, evidence of fusion products at sites distal from the target organ and data to suggest that migration occurs via the vasculature. These results will inform and improve future, MSC-based therapeutics.

Combination of single-photon emission computed tomography and magnetic resonance imaging to track 111in-oxine-labeled human mesenchymal stem cells in neuroblastoma-bearing mice

Homing is an inherent, complex, multistep process performed by cells such as human bone marrow mesenchymal stem cells (hMSCs) to travel from a distant location to inflamed or damaged tissue and tumors. This ability of hMSCs has been exploited as a tumor-targeting strategy in cell-based cancer therapy. The purpose of this study was to investigate the applicability of 111In-oxine for tracking hMSCs in vivo by combining single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI). 111In-labeled hMSCs (106 cells) were infused intraperitoneally in neuroblastoma-bearing mice, whereas a control group received a dose of free 111In-oxine. SPECT and MRI studies were performed 24 and 48 hours afterwards. Initially, the images showed similar activity in the abdomen in both controls and hMSC-injected animals. In general, abdominal activity decreases at 48 hours. hMSC-injected animals showed increased uptake in the tumor area at 48 hours, whereas the control group showed a low level of activity at 24 hours, which decreased at 48 hours. In conclusion, tracking 111In-labeled hMSCs combining SPECT and MRI is feasible and may be transferable to clinical research. The multimodal combination is essential to ensure appropriate interpretation of the images.

Suspension-Expansion of Bone Marrow Results in Small Mesenchymal Stem Cells Exhibiting Increased Transpulmonary Passage Following Intravenous Administration

Mesenchymal stem cells (MSCs) have been extensively explored in a variety of regenerative medicine applications. The relatively large size of MSCs expanded in tissue culture flasks leads to retention in the microcirculation of the lungs following intravenous delivery, reducing their capacity to reach target sites. We explored whether the expansion of whole marrow in suspension cultures would yield smaller MSCs with increased capacity to traverse the pulmonary microcirculation compared with traditional monolayer cultures. We tested this hypothesis using rat marrow in a suspension bioreactor culture with fibronectin-coated microcarriers, leading to sustained expansion of both the microbead-adherent cells, as well as of a nonadherent cell fraction. Magnetic depletion of CD45(+) cells from the bioreactor cultures after 5 weeks led to a highly enriched CD73(+)/CD90(+)/CD105(+) MSC population. The bioreactor-grown MSCs were significantly smaller than parallel monolayer MSCs (15.1 ± 0.9 μm vs. 18.5 ± 2.3 μm diameter, p<0.05). When fluorescently labeled bioreactor-grown MSCs were intravenously injected into rats, the peak cell concentration in the arterial circulation was an order of magnitude higher than similarly delivered monolayer-grown MSCs (94.8 ± 29.6 vs. 8.2 ± 5.6/10(6) nucleated blood cells, respectively, p<0.05). At 24 h after intravenous injection of the LacZ-labeled bioreactor-grown MSCs, there was a significant threefold decrease in the LacZ-labeled MSCs trapped in the lungs, with a significant increase in the cells reaching the spleen and liver in comparison to their monolayer MSC counterparts. Bioreactor-grown whole marrow cell cultures yielded smaller MSCs with increased capacity to traverse the pulmonary microcirculation compared with traditionally expanded monolayer MSCs. This may significantly improve the capacity and efficiency of these cells to home to injury sites downstream of the lungs.

Niche-dependent regulations of metabolic balance in high-fat diet-induced diabetic mice by mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have great potential to maintain glucose homeostasis and metabolic balance. Here, we demonstrate that in mice continuously fed with high-fat diet (HFD) that developed non-insulin-dependent diabetes, two episodes of systemic MSC transplantations effectively improve glucose tolerance and blood glucose homeostasis and reduce body weight through targeting pancreas and insulin-sensitive tissues and organs via site-specific mechanisms. MSCs support pancreatic islet growth by direct differentiation into insulin-producing cells and by mitigating the cytotoxicity of interleukin 1 (IL-1) and tumor necrosis factor-α (TNF-α) in the pancreas. Localization of MSCs in the liver and skeletal muscles in diabetic animals is also enhanced and therefore improves glucose tolerance, although long-term engraftment is not observed. MSCs prevent HFD-induced fatty liver development and restore glycogen storage in hepatocytes. Increased expression of IL-1 receptor antagonist and Glut4 in skeletal muscles after MSC transplantation results in better blood glucose homeostasis. Intriguingly, systemic MSC transplantation does not alter adipocyte number, but it decreases HFD-induced cell infiltration in adipose tissues and reduces serum levels of adipokines, including leptin and TNF-α. Taken together, systemic MSC transplantation ameliorates HFD-induced obesity and restores metabolic balance through multisystemic regulations that are niche dependent. Such findings have supported systemic transplantation of MSCs to correct metabolic imbalance.

Concise review: workshop review: understanding and assessing the risks of stem cell-based therapies

The field of stem cell therapeutics is moving ever closer to widespread application in the clinic. However, despite the undoubted potential held by these therapies, the balance between risk and benefit remains difficult to predict. As in any new field, a lack of previous application in man and gaps in the underlying science mean that regulators and investigators continue to look for a balance between minimizing potential risk and ensuring therapies are not needlessly kept from patients. Here, we attempt to identify the important safety issues, assessing the current advances in scientific knowledge and how they may translate to clinical therapeutic strategies in the identification and management of these risks. We also investigate the tools and techniques currently available to researchers during preclinical and clinical development of stem cell products, their utility and limitations, and how these tools may be strategically used in the development of these therapies. We conclude that ensuring safety through cutting-edge science and robust assays, coupled with regular and open discussions between regulators and academic/industrial investigators, is likely to prove the most fruitful route to ensuring the safest possible development of new products.

MRI/SPECT/Fluorescent Tri-Modal Probe for Evaluating the Homing and Therapeutic Efficacy of Transplanted Mesenchymal Stem Cells in a Rat Ischemic Stroke Model

Quantitatively tracking engraftment of intracerebrally or intravenously transplanted stem cells and evaluating their concomitant therapeutic efficacy for stroke has been a challenge in the field of stem cell therapy. In this study, first, an MRI/SPECT/fluorescent tri-modal probe (¹²⁵I-fSiO4@SPIOs) is synthesized for quantitatively tracking mesenchymal stem cells (MSCs) transplanted intracerebrally or intravenously into stroke rats, and then the therapeutic efficacy of MSCs delivered by both routes and the possible mechanism of the therapy are evaluated. It is demonstrated that ⁽¹²⁵⁾I-fSiO4@SPIOs have high efficiency for labeling MSCs without affecting their viability, differentiation, and proliferation capacity, and found that 35% of intracerebrally injected MSCs migrate along the corpus callosum to the lesion area, while 90% of intravenously injected MSCs remain trapped in the lung at 14 days after MSC transplantation. However, neurobehavioral outcomes are significantly improved in both transplantation groups, which are accompanied by increases of vascular endothelial growth factor, basic fibroblast growth factor, and tissue inhibitor of metalloproteinases-3 in blood, lung, and brain tissue (p < 0.05). The study demonstrates that ¹²⁵I-fSiO4@SPIOs are robust probe for long-term tracking of MSCs in the treatment of ischemic brain and MSCs delivered via both routes improve neurobehavioral outcomes in ischemic rats.

Safety and biodistribution study of bone marrow-derived mesenchymal stromal cells and mononuclear cells and the impact of the administration route in an intact porcine model

BACKGROUND AIMS

Bone marrow mononuclear cells (BM-MNCs) and bone marrow-derived mesenchymal stem stromal cells (BM-MSCs) could have therapeutic potential for numerous conditions, including ischemia-related injury. Cells transplanted intravascularly may become entrapped in the lungs, which potentially decreases their therapeutic effect and increases the risk for embolism.

METHODS

Twelve pigs were divided into groups of 3 and received (99m)Tc- hydroxymethyl-propylene-amine-oxime-labeled autologous BM-MNCs or allogeneic BM-MSCs by either intravenous (IV) or intra-arterial (IA) transplantation. A whole body scan and single photon emission computed tomography/computed tomography (SPECT/CT) were performed 8 h later, and tissue biopsies were collected for gamma counting. A helical CT scan was also performed on 4 pigs to detect possible pulmonary embolism, 2 after IV BM-MSC injection and 2 after saline injection.

RESULTS

The transplantation route had a greater impact on the biodistribution of the BM-MSCs than the BM-MNCs. The BM-MNCs accumulated in the spleen and bones, irrespective of the administration route. The BM-MSCs had relatively higher uptake in the kidneys. The IA transplantation decreased the deposition of BM-MSCs in the lungs and increased uptake in other organs, especially in the liver. Lung atelectases were frequent due to mechanical ventilation and attracted transplanted cells. CT did not reveal any pulmonary embolism.

CONCLUSIONS

Both administration routes were found to be safe, but iatrogenic atelectasis might be an issue when cells accumulate in the lungs. The IA administration is effective in avoiding pulmonary entrapment of BM-MSCs. The cell type and administration method both have a major impact on the acute homing.

Superparamagnetic iron oxide promotes osteogenic differentiation of rat adipose-derived stem cells

Adult adipose tissue-derived stem cells (ADSCs) were found to hold great promise for use in bone tissue repair and regeneration. The present study aims to improve the osteogenesis of ADSCs by Superparamagnetic Iron Oxide (SPIO), which is widely used in tissue imaging. In this study, adipose-derived stem cells were harvested from 4-week-old male Sprague-Dawley (SD) rats. The proliferation rates of ADSCs labeling with or without SPIO were assessed by using trypan blue assay. The osteogenic capability was examined by employing the ALP activity detection kit. The mineralization of cells was determined by staining with Alizarin red S. Flow cytometry analysis was used to examine the cell apoptosis treated with or without SPIO. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis was utilized to detect the Runx2, Opn, Ocn and ALP genes in the cells. The results indicated that SPIO could promote rat ADSCs proliferation and reduce rat ADSCs apoptosis. Also, SPIO could significantly enhance the ALP and alizarin red staining of ADSCs in -SPIO group and +SPIO group (P < 0.01). Furthermore, we also found that the expression of Runx2, Opn, Ocn and ALP was significantly increased after SPIO treatment compared to the un-treated cells (P < 0.01). In conclusion, SPIO could promote the osteogenic differentiation of rat adipose-derived stem cells, which would also become a great potential therapeutic tool in bone tissue engineering.

Crucial role of IL1beta and C3a in the in vitro-response of multipotent mesenchymal stromal cells to inflammatory mediators of polytrauma

Multipotent mesenchymal stromal cells (MSC) exert immune-modulatory effects and support tissue regeneration in various local trauma models. In case of a polytrauma, high amounts of danger-associated molecular patterns are released, leading to a systemic increase of inflammatory mediators. The influence of such a complex inflammatory microenvironment on human MSC is mainly unknown so far. Therefore, we investigated the effects of a defined serum-free polytrauma “cocktail” containing ILͳbeta, IL6, IL8 and the anaphylatoxins C3a and C5a, in concentrations corresponding to those measured in the blood of polytrauma patients, on human MSC in vitro. The polytrauma cocktail induced directed migration of MSC with C3a representing its major soluble chemoattractive agent. Furthermore, the polytrauma cocktail and IL1beta upregulated the expression of MMP1 indicating a potential role of IL1beta to enhance MSC migration in the tissue context. COX2, PTGES and TSG6 were also found to be upregulated upon stimulation with the polytrauma cocktail or IL1beta, but not through other single factors of the polytrauma cocktail in pathophysiologically relevant concentrations. An RNA expression array of 84 inflammation-related genes revealed that both the polytrauma cocktail and IL1beta induced C3, CSF1, TLR3 and various chemokines without major qualitative or quantitative differences. These results indicate that IL1beta is a crucial mediator of the polytrauma cocktail in terms of immune-modulation and MMP1 expression. Thus, upon encountering the primary sterile, inflammatory milieu of a polytrauma, endogenous or systemically transfused MSC might be able to migrate to sites of injury, secrete TSG6 and PGE2 and to influence macrophage biology as observed in local trauma models.

Stem cell imaging: from bench to bedside

Although cellular therapies hold great promise for the treatment of human disease, results from several initial clinical trials have not shown a level of efficacy required for their use as a first line therapy. Here we discuss how in vivo molecular imaging has helped identify barriers to clinical translation and potential strategies that may contribute to successful transplantation and improved outcomes, with a focus on cardiovascular and neurological diseases. We conclude with a perspective on the future role of molecular imaging in defining safety and efficacy for clinical implementation of stem cell therapies.

Improved dopamine transporter binding activity after bone marrow mesenchymal stem cell transplantation in a rat model of Parkinson's disease: small animal positron emission tomography study with F-18 FP-CIT

OBJECTIVES

We evaluated the effects of bone marrow-derived mesenchymal stem cells (BMSCs) in a model of Parkinson's disease (PD) using serial F-18 fluoropropylcarbomethoxyiodophenylnortropane (FP-CIT) PET.

METHODS

Hemiparkinsonian rats were treated with intravenously injected BMSCs, and animals without stem cell therapy were used as the controls. Serial FP-CIT PET was performed after therapy. The ratio of FP-CIT uptake in the lesion side to uptake in the normal side was measured. The changes in FP-CIT uptake were also analyzed using SPM. Behavioural and histological changes were observed using the rotational test and tyrosine hydroxylase (TH)-reactive cells.

RESULTS

FP-CIT uptake ratio was significantly different in the BMSCs treated group (n = 28) at each time point. In contrast, there was no difference in the ratio in control rats (n = 25) at any time point. SPM analysis also revealed that dopamine transporter binding activity was enhanced in the right basal ganglia area in only the BMSC therapy group. In addition, rats that received BMSC therapy also exhibited significantly improved rotational behaviour and preservation of TH-positive neurons compared to controls.

CONCLUSIONS

The therapeutic effect of intravenously injected BMSCs in a rat model of PD was confirmed by dopamine transporter PET imaging, rotational functional studies, and histopathological evaluation.

KEY POINTS

• Mesenchymal stem cells were intravenously injected to treat the PD rats • Dopamine transporter binding activity was improved after stem cell therapy • Stem cell therapy induced functional recovery and preservation of dopaminergic neurons • The effect of stem cells was confirmed by FP-CIT PET.

PhiC31/PiggyBac modified stromal stem cells: effect of interferon γ and/or tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) on murine melanoma

Background

TRAIL and IFNγ are promising anti-cancer cytokines and it has been shown that IFNγ may sensitize cancer cells to TRAIL. Adipose derived mesenchymal stem cells (ADSCs) are attractive vehicles for delivering anti-cancer agents. In this study, we evaluated the therapeutic potential of PhiC31 (φC31) recombinase and/or piggyBac transposase (pBt) modified ADSCs expressing either TRAIL, IFNγ, or co-expressing TRAIL/IFNγ in mouse models of melanoma.

Methods

The expression and bioactivity of mouse IFNγ and TRAIL in φC31 and pBt modified cells were confirmed. We examined the effects of modified ADSCs on signal intensity of red fluorescence protein expressed by melanoma cells in subcutaneous tumors or established lung metastases and on survival (6 mice per group). We also conducted a flow cytometric analysis of systemic CD4⁺CD25⁺FOXP3⁺ T regulatory cells (Tregs) and histological analysis of melanoma tumors. Data were analyzed by Student t test, ANOVA, and log-rank tests. All statistical tests were two-sided.

Results

We demonstrated non-viral DNA-integrating vectors can be used for stable transgene expression. IFNγ inhibited melanoma cell growth in vitro probably via IFNγ-induced JAK/STAT1 signaling pathway activation. Murine TRAIL induced apoptosis in the human cell lines CAOV-4 and Ej-138, while MCF7 and B16F10 cells appeared to be insensitive to TRAIL. Treatment of melanoma cells with IFNγ did not influence their response to TRAIL. In contrast, results from in vivo studies showed that IFNγ-expressing ADSCs, engrafted into tumor stroma, inhibited tumor growth and angiogenesis, prevented systemic increase of Tregs, increased PD-L1 expression and CD8+ infiltration (but not interleukin-2+ cells), and prolonged the survival of mice (68 days, 95% confidence interval [CI] =52 to 86 days compared to 36 days, 95% CI =29 to 39 days for control, P < .001).

Conclusions

For the first time, we employed DNA integrating vectors for safe and stable modification of MSCs. Our data indicate potential of non-virally modified IFNγ-expressing ADSCs for treatment of melanoma through direct effects of IFNγ. This study may have a significant role in the management of cancer in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-255) contains supplementary material, which is available to authorized users.

In vivo imaging of transplanted stem cells in the central nervous system

In vivo imaging is increasingly being utilized in studies investigating stem cell-based treatments for neurological disorders. Direct labeling is used in preclinical and clinical studies to track the fate of transplanted cells. To further determine cell viability, experimental studies are able to take advantage of reporter gene technologies. Structural and functional brain imaging can also be used alongside cell imaging as biomarkers of treatment efficacy. Furthermore, it is possible that new imaging techniques could be used to monitor functional integration of stem cell-derived cells with the host nervous system. In this review, we examine recent developments in these areas and identify promising directions for future research at the interface of stem cell therapies and neuroimaging.