Superparamagnetic iron oxide nanoparticle targeting of MSCs in vascular injury
2013; 34 (8): 1987-1994
Magnetic cell delivery for peripheral arterial disease: A theoretical framework
2011; 38 (7): 3932-3943
Vascular occlusion can result in fatal myocardial infarction, stroke or loss of limb in peripheral arterial disease. Interventional balloon angioplasty is a common first line procedure for vascular disease treatment, but long term success is limited by restenosis and neointimal hyperplasia. Cellular therapies have been proposed to mitigate these issues; however efficacy is low, in part due to poor cell retention. We show that magnetic targeting of mesenchymal stem cells gives rise to a 6-fold increase in cell retention following balloon angioplasty in a rabbit model using a clinically applicable permanent magnet. Cells labelled with superparamagnetic iron oxide nanoparticles exhibit no negative effects on cell viability, differentiation or secretion patterns. The increase in stem cell retention leads to a reduction in restenosis three weeks after cell delivery.
View details for DOI 10.1016/j.biomaterials.2012.11.040
View details for Web of Science ID 000315003500012
View details for PubMedID 23237516
Comparison of Segmentation Methods for MRI Measurement of Cardiac Function in Rats
JOURNAL OF MAGNETIC RESONANCE IMAGING
2010; 32 (4): 869-877
Our aim was to compare different magnet arrangements for magnetic cell delivery to human lower leg arteries and investigate the theoretical targeting efficiency under realistic flow conditions as a possible treatment after angioplasty. Additionally the potential of scaling down or translating the magnetic actuation device for preclinical studies was explored.Using finite element methods, the magnetic field distribution was calculated in 3D for the optimization of magnet arrangements. Computational fluid dynamics simulations were performed for the human posterior tibial artery with the geometry and boundary condition data derived from magnetic resonance imaging (MRI) studies. These simulations were used to trace the trajectories of cells for an optimized magnet arrangement. Additionally the behavior of cells close to the vessel wall was investigated using a fluid-structure interaction model.The optimal magnet for the lower leg arteries was a Halbach cylinder k3 variety (12 elements with 900 rotation steps for the magnetization orientation). With this magnet, numerical simulations predict a targeting efficiency of 6.25% could be achieved in the posterior tibial artery for cells containing 150 pg iron. Similar simulations, which were scaled down to rabbit dimensions while keeping the forces acting on a cell constant, lead to similar predicted targeting efficiencies. Fluid dynamic and fluid-structure interaction simulations predict that magnetically labeled cells within a 0.5% radii distance to the vessel wall would be attracted and remain at the wall under physiological flow conditions.First pass capture of magnetically labeled cells under pulsatile flow conditions in human lower leg arteries leads to low targeting efficiencies. However, this can be increased to almost 100% by stopping the blood flow for 5 min. A magnetic actuation device can be designed for animal models that generate magnetic forces achievable for cells in human leg arteries.
View details for DOI 10.1118/1.3593363
View details for Web of Science ID 000292521100005
View details for PubMedID 21858990
Targeted magnetic delivery and tracking of cells using a magnetic resonance imaging system
2010; 31 (20): 5366-5371
To establish the accuracy, intra- and inter-observer variabilities of four different segmentation methods for measuring cardiac functional parameters in healthy and infarcted rat hearts.Six Wistar rats were imaged before and after myocardial infarction using an electrocardiogram and respiratory-gated spoiled gradient echo sequence. Blinded and randomized datasets were analyzed by various semi-automatic and manual segmentation methods to compare their measurement bias and variability. In addition, the accuracy of these methods was assessed by comparison with reference measurements acquired from high-resolution three-dimensional (3D) datasets of a heart phantom.Relative inter- and intra-observer variability were found to be similar for all four methods. Semi-automatic segmentation methods reduced analysis time by up to 70%, while yielding similar measurement bias and variability compared with manual segmentation. Semi-automatic methods were found to underestimate the ejection fraction for healthy hearts compared with manual segmentation while overestimating them in infarcted hearts. However, semi-automatic segmentation of short axis slices agreed better with 3D reference scans of a heart phantom compared with manual segmentation.Semi-automatic segmentation methods are faster than manual segmentation, while offering a similar intra- and inter-observer variability. However, a potential bias has been observed between healthy and infarcted hearts for different methods, which should also be considered when selecting the most appropriate analysis technique.
View details for DOI 10.1002/jmri.22305
View details for Web of Science ID 000282764800012
View details for PubMedID 20882617
Stem Cell Imaging: From Bench to Bedside
CELL STEM CELL
2014; 14 (4): 431-444
The success of cell therapies depends on the ability to deliver the cells to the site of injury. Targeted magnetic cell delivery is an emergent technique for localised cell transplantation therapy. The use of permanent magnets limits such a treatment to organs close to the body surface or an implanted magnetic source. A possible alternative method for magnetic cell delivery is magnetic resonance targeting (MRT), which uses magnetic field gradients inherent to all magnetic resonance imaging system, to steer ferromagnetic particles to their target region. In this study we have assessed the feasibility of such an approach for cell targeting, using a range of flow rates and different super paramagnetic iron oxide particles in a vascular bifurcation phantom. Using MRT we have demonstrated that 75% of labelled cells could be guided within the vascular bifurcation. Furthermore we have demonstrated the ability to image the labelled cells before and after magnetic targeting, which may enable interactive manipulation and assessment of the distribution of cellular therapy. This is the first demonstration of cellular MRT and these initial findings support the potential value of MRT for improved targeting of intravascular cell therapies.
View details for DOI 10.1016/j.biomaterials.2010.03.032
View details for Web of Science ID 000278571800009
View details for PubMedID 20382425
Costimulation-Adhesion Blockade is Superior to Cyclosporine A and Prednisone Immunosuppressive Therapy for Preventing Rejection of Differentiated Human Embryonic Stem Cells Following Transplantation.
2013; 31 (11): 2354-2363
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.
View details for DOI 10.1016/j.stem.2014.03.009
View details for Web of Science ID 000334766400008
View details for PubMedID 24702995
Mutation of the Diamond-Blackfan Anemia Gene Rps7 in Mouse Results in Morphological and Neuroanatomical Phenotypes
2013; 9 (1)
Rationale: Human embryonic stem cell (hESC) derivatives are attractive candidates for therapeutic use. The engraftment and survival of hESC derivatives as xenografts or allografts require effective immunosuppression to prevent immune cell infiltration and graft destruction. Objective: To test the hypothesis that a short-course, dual-agent regimen of two costimulation-adhesion blockade agents can induce better engraftment of hESC derivatives compared to current immunosuppressive agents. Methods and Results: We transduced hESCs with a double fusion reporter gene construct expressing firefly luciferase (Fluc) and enhanced green fluorescent protein, and differentiated these cells to endothelial cells (hESC-ECs). Reporter gene expression enabled longitudinal assessment of cell engraftment by bioluminescence imaging. Costimulation-adhesion therapy resulted in superior hESC-EC and mouse EC engraftment compared to cyclosporine therapy in a hind limb model. Costimulation-adhesion therapy also promoted robust hESC-EC and hESC-derived cardiomyocyte survival in an ischemic myocardial injury model. Improved hESC-EC engraftment had a cardioprotective effect after myocardial injury, as assessed by magnetic resonance imaging. Mechanistically, costimulation-adhesion therapy is associated with systemic and intragraft upregulation of T-cell immunoglobulin and mucin domain 3 (TIM3) and a reduced proinflammatory cytokine profile. Conclusions: Costimulation-adhesion therapy is a superior alternative to current clinical immunosuppressive strategies for preventing the post-transplant rejection of hESC derivatives. By extending the window for cellular engraftment, costimulation-adhesion therapy enhances functional preservation following ischemic injury. This regimen may function through a TIM3-dependent mechanism. Stem Cells 2013;31:2354-2363.
View details for DOI 10.1002/stem.1501
View details for PubMedID 24038578
Thymosin ß4-sulfoxide attenuates inflammatory cell infiltration and promotes cardiac wound healing.
2013; 4: 2081-?
The ribosome is an evolutionarily conserved organelle essential for cellular function. Ribosome construction requires assembly of approximately 80 different ribosomal proteins (RPs) and four different species of rRNA. As RPs co-assemble into one multi-subunit complex, mutation of the genes that encode RPs might be expected to give rise to phenocopies, in which the same phenotype is associated with loss-of-function of each individual gene. However, a more complex picture is emerging in which, in addition to a group of shared phenotypes, diverse RP gene-specific phenotypes are observed. Here we report the first two mouse mutations (Rps7(Mtu) and Rps7(Zma)) of ribosomal protein S7 (Rps7), a gene that has been implicated in Diamond-Blackfan anemia. Rps7 disruption results in decreased body size, abnormal skeletal morphology, mid-ventral white spotting, and eye malformations. These phenotypes are reported in other murine RP mutants and, as demonstrated for some other RP mutations, are ameliorated by Trp53 deficiency. Interestingly, Rps7 mutants have additional overt malformations of the developing central nervous system and deficits in working memory, phenotypes that are not reported in murine or human RP gene mutants. Conversely, Rps7 mouse mutants show no anemia or hyperpigmentation, phenotypes associated with mutation of human RPS7 and other murine RPs, respectively. We provide two novel RP mouse models and expand the repertoire of potential phenotypes that should be examined in RP mutants to further explore the concept of RP gene-specific phenotypes.
View details for DOI 10.1371/journal.pgen.1003094
View details for Web of Science ID 000314651500002
View details for PubMedID 23382688
Rapid magnetic cell delivery for large tubular bioengineered constructs
JOURNAL OF THE ROYAL SOCIETY INTERFACE
2012; 9 (76): 3008-3016
The downstream consequences of inflammation in the adult mammalian heart are formation of a non-functional scar, pathological remodelling and heart failure. In zebrafish, hydrogen peroxide released from a wound is the initial instructive chemotactic cue for the infiltration of inflammatory cells, however, the identity of a subsequent resolution signal(s), to attenuate chronic inflammation, remains unknown. Here we reveal that thymosin β4-sulfoxide lies downstream of hydrogen peroxide in the wounded fish and triggers depletion of inflammatory macrophages at the injury site. This function is conserved in the mouse and observed after cardiac injury, where it promotes wound healing and reduced scarring. In human T-cell/CD14+ monocyte co-cultures, thymosin β4-sulfoxide inhibits interferon-γ, and increases monocyte dispersal and cell death, likely by stimulating superoxide production. Thus, thymosin β4-sulfoxide is a putative target for therapeutic modulation of the immune response, resolution of fibrosis and cardiac repair.
View details for DOI 10.1038/ncomms3081
View details for PubMedID 23820300
Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons
2012; 484 (7394): 367-U102
Delivery of cells into tubular tissue constructs with large diameters poses significant spatial and temporal challenges. This study describes preliminary findings for a novel process for rapid and uniform seeding of cells onto the luminal surface of large tubular constructs. Fibroblasts, tagged with superparamagnetic iron oxide nanoparticles (SPION), were directed onto the luminal surface of tubular constructs by a magnetic field generated by a k4-type Halbach cylinder device. The spatial distribution of attached cells, as measured by the mean number of cells, was compared with a conventional, dynamic, rotational cell-delivery technique. Cell loading onto the constructs was measured by microscopy and magnetic resonance imaging. The different seeding techniques employed had a significant effect on the spatial distribution of the cells (p < 0.0001). The number of attached cells at defined positions within the same construct was significantly different for the dynamic rotation technique (p < 0.05). In contrast, no significant differences in the number of cells attached to the luminal surface were found between the defined positions on the construct loaded with the Halbach cylinder. The technique described overcomes limitations associated with existing cell-delivery techniques and is amenable to a variety of tubular organs where rapid loading and uniform distribution of cells for therapeutic applications are required.
View details for DOI 10.1098/rsif.2012.0316
View details for Web of Science ID 000309269100023
View details for PubMedID 22696487
Imaging seizure-induced inflammation using an antibody targeted iron oxide contrast agent
2012; 60 (2): 1149-1155
Understanding the molecular and cellular mechanisms that mediate magnetosensation in vertebrates is a formidable scientific problem. One hypothesis is that magnetic information is transduced into neuronal impulses by using a magnetite-based magnetoreceptor. Previous studies claim to have identified a magnetic sense system in the pigeon, common to avian species, which consists of magnetite-containing trigeminal afferents located at six specific loci in the rostral subepidermis of the beak. These studies have been widely accepted in the field and heavily relied upon by both behavioural biologists and physicists. Here we show that clusters of iron-rich cells in the rostro-medial upper beak of the pigeon Columbia livia are macrophages, not magnetosensitive neurons. Our systematic characterization of the pigeon upper beak identified iron-rich cells in the stratum laxum of the subepidermis, the basal region of the respiratory epithelium and the apex of feather follicles. Using a three-dimensional blueprint of the pigeon beak created by magnetic resonance imaging and computed tomography, we mapped the location of iron-rich cells, revealing unexpected variation in their distribution and number--an observation that is inconsistent with a role in magnetic sensation. Ultrastructure analysis of these cells, which are not unique to the beak, showed that their subcellular architecture includes ferritin-like granules, siderosomes, haemosiderin and filopodia, characteristics of iron-rich macrophages. Our conclusion that these cells are macrophages and not magnetosensitive neurons is supported by immunohistological studies showing co-localization with the antigen-presenting molecule major histocompatibility complex class II. Our work necessitates a renewed search for the true magnetite-dependent magnetoreceptor in birds.
View details for DOI 10.1038/nature11046
View details for Web of Science ID 000302946500031
View details for PubMedID 22495303
A rat decellularized small bowel scaffold that preserves villus-crypt architecture for intestinal regeneration
2012; 33 (12): 3401-3410
Early inflammation following status epilepticus has been implicated in the development of epilepsy and the evolution of brain injury, yet its precise role remains unclear. The development of non-invasive imaging markers of inflammation would enable researchers to test this hypothesis in vivo and study its temporal progression in relation to epileptogenic insults. In this study we have investigated the potential of a targeted magnetic resonance imaging contrast agent--vascular cell adhesion molecule 1 antibody labelled iron oxide--to image the inflammatory process following status epilepticus in the rat lithium-pilocarpine model. Intravascular administration of the targeted contrast agent was performed at approximately 1 day following status epilepticus. The control group received diazepam prior to pilocarpine to prevent status epilepticus. Magnetic resonance imaging of rats was performed before and after contrast administration. Comparison with quantitative T? measurements was also performed. At the end of the study, brains were removed for ex vivo magnetic resonance imaging and histology. Marked focal hypointensities caused by contrast agent binding were observed on in vivo magnetic resonance images in the post status epilepticus group. In particular these occurred in the periventricular organs, the hippocampus and the cerebral cortex. Relatively little contrast agent binding was observed in the control group. T? relaxation times were not significantly increased for the hippocampus or the cerebral cortex in post status epilepticus animals. These results demonstrate the feasibility of in vivo imaging of seizure-induced inflammation in an animal model of epilepsy. The antibody targeted MRI contrast agent identified regions of acute inflammation following status epilepticus and may provide an early marker of brain injury. This technique could be used to determine the role of inflammation in models of epileptogenesis and to study the potential for anti-inflammatory therapeutic interventions.
View details for DOI 10.1016/j.neuroimage.2012.01.048
View details for Web of Science ID 000303272300032
View details for PubMedID 22266177
Amniotic Fluid Stem Cells Are Cardioprotective Following Acute Myocardial Infarction
STEM CELLS AND DEVELOPMENT
2011; 20 (11): 1985-1994
Management of intestinal failure remains a clinical challenge and total parenteral nutrition, intestinal elongation and/or transplantation are partial solutions. In this study, using a detergent-enzymatic treatment (DET), we optimize in rats a new protocol that creates a natural intestinal scaffold, as a base for developing functional intestinal tissue. After 1 cycle of DET, histological examination and SEM and TEM analyses showed removal of cellular elements with preservation of the native architecture and connective tissue components. Maintenance of biomechanical, adhesion and angiogenic properties were also demonstrated strengthen the idea that matrices obtained using DET may represent a valid support for intestinal regeneration.
View details for DOI 10.1016/j.biomaterials.2012.01.012
View details for Web of Science ID 000301886300003
View details for PubMedID 22305104
De novo cardiomyocytes from within the activated adult heart after injury
2011; 474 (7353): 640-U117
In recent years, various types of stem cells have been characterized and their potential for cardiac regeneration has been investigated. We have previously described the isolation of broadly multipotent cells from amniotic fluid, defined as amniotic fluid stem (AFS) cells. The aim of this study was to investigate the therapeutic potential of human AFS cells (hAFS) in a model of acute myocardial infarction. Wistar rats underwent 30?min of ischemia by ligation of the left anterior descending coronary artery, followed by administration of hAFS cells and 2?h of reperfusion. Infarct size was assessed by 2,3,5-triphenyltetrazolium chloride staining and planimetry. hAFS cells were also analyzed by enzyme-linked immunosorbent assay to detect secretion of putative paracrine factors, such as the actin monomer-binding protein thymosin ?4 (T?4). The systemic injection of hAFS cells and their conditioned medium (hAFS-CM) was cardioprotective, improving myocardial cell survival and decreasing the infarct size from 53.9%±2.3% (control animals receiving phosphate-buffered saline injection) to 40.0%±3.0% (hAFS cells) and 39.7%±2.5% (hAFS-CM, P<0.01). In addition, hAFS cells were demonstrated to secrete T?4, previously shown to be both cardioprotective and proangiogenic. Our results suggest that AFS cells have therapeutic potential in the setting of acute myocardial infarction, which may be mediated through paracrine effectors such as T?4. Therefore, AFS cells might represent a novel source for cell therapy and cell transplantation strategies in repair following ischemic heart disease, with a possible paracrine mechanism of action and a potential molecular candidate for acute cardioprotection.
View details for DOI 10.1089/scd.2010.0424
View details for Web of Science ID 000296587400014
View details for PubMedID 21534857
In Vitro and In Vivo Cardiomyogenic Differentiation of Amniotic Fluid Stem Cells
STEM CELL REVIEWS AND REPORTS
2011; 7 (2): 364-380
A significant bottleneck in cardiovascular regenerative medicine is the identification of a viable source of stem/progenitor cells that could contribute new muscle after ischaemic heart disease and acute myocardial infarction. A therapeutic ideal--relative to cell transplantation--would be to stimulate a resident source, thus avoiding the caveats of limited graft survival, restricted homing to the site of injury and host immune rejection. Here we demonstrate in mice that the adult heart contains a resident stem or progenitor cell population, which has the potential to contribute bona fide terminally differentiated cardiomyocytes after myocardial infarction. We reveal a novel genetic label of the activated adult progenitors via re-expression of a key embryonic epicardial gene, Wilm's tumour 1 (Wt1), through priming by thymosin ?4, a peptide previously shown to restore vascular potential to adult epicardium-derived progenitor cells with injury. Cumulative evidence indicates an epicardial origin of the progenitor population, and embryonic reprogramming results in the mobilization of this population and concomitant differentiation to give rise to de novo cardiomyocytes. Cell transplantation confirmed a progenitor source and chromosome painting of labelled donor cells revealed transdifferentiation to a myocyte fate in the absence of cell fusion. Derived cardiomyocytes are shown here to structurally and functionally integrate with resident muscle; as such, stimulation of this adult progenitor pool represents a significant step towards resident-cell-based therapy in human ischaemic heart disease.
View details for DOI 10.1038/nature10188
View details for Web of Science ID 000292204300039
View details for PubMedID 21654746
Magnetically assisted delivery of cells using a magnetic resonance imaging system
JOURNAL OF PHYSICS D-APPLIED PHYSICS
2011; 44 (5)
Cardiovascular magnetic resonance imaging in experimental models.
The open cardiovascular medicine journal
2010; 4: 278-292
Cell therapy has developed as a complementary treatment for myocardial regeneration. While both autologous and allogeneic uses have been advocated, the ideal candidate has not been identified yet. Amniotic fluid-derived stem (AFS) cells are potentially a promising resource for cell therapy and tissue engineering of myocardial injuries. However, no information is available regarding their use in an allogeneic context. c-kit-sorted, GFP-positive rat AFS (GFP-rAFS) cells and neonatal rat cardiomyocytes (rCMs) were characterized by cytocentrifugation and flow cytometry for the expression of mesenchymal, embryonic and cell lineage-specific antigens. The activation of the myocardial gene program in GFP-rAFS cells was induced by co-culture with rCMs. The stem cell differentiation was evaluated using immunofluorescence, RT-PCR and single cell electrophysiology. The in vivo potential of Endorem-labeled GFP-rAFS cells for myocardial repair was studied by transplantation in the heart of animals with ischemia/reperfusion injury (I/R), monitored by magnetic resonance imaging (MRI). Three weeks after injection a small number of GFP-rAFS cells acquired an endothelial or smooth muscle phenotype and to a lesser extent CMs. Despite the low GFP-rAFS cells count in the heart, there was still an improvement of ejection fraction as measured by MRI. rAFS cells have the in vitro propensity to acquire a cardiomyogenic phenotype and to preserve cardiac function, even if their potential may be limited by poor survival in an allogeneic setting.
View details for DOI 10.1007/s12015-010-9200-z
View details for Web of Science ID 000289297600013
View details for PubMedID 21120638
Cardiovascular magnetic resonance (CMR) imaging is the modality of choice for clinical studies of the heart and vasculature, offering detailed images of both structure and function with high temporal resolution.Small animals are increasingly used for genetic and translational research, in conjunction with models of common pathologies such as myocardial infarction. In all cases, effective methods for characterising a wide range of functional and anatomical parameters are crucial for robust studies.CMR is the gold-standard for the non-invasive examination of these models, although physiological differences, such as rapid heart rate, make this a greater challenge than conventional clinical imaging. However, with the help of specialised magnetic resonance (MR) systems, novel gating strategies and optimised pulse sequences, high-quality images can be obtained in these animals despite their small size. In this review, we provide an overview of the principal CMR techniques for small animals for example cine, angiography and perfusion imaging, which can provide measures such as ejection fraction, vessel anatomy and local blood flow, respectively. In combination with MR contrast agents, regional dysfunction in the heart can also be identified and assessed. We also discuss optimal methods for analysing CMR data, particularly the use of semi-automated tools for parameter measurement to reduce analysis time. Finally, we describe current and emerging methods for imaging the developing heart, aiding characterisation of congenital cardiovascular defects. Advanced small animal CMR now offers an unparalleled range of cardiovascular assessments. Employing these methods should allow new insights into the structural, functional and molecular basis of the cardiovascular system.
View details for DOI 10.2174/1874192401004010278
View details for PubMedID 21331311