Manganese cell labeling of murine hepatocytes using manganese(III)‐transferrin

Manganese(III)‐transferrin [Mn(III)–Tf] was investigated as a way to accomplish manganese‐labeling of murine hepatocytes for MRI contrast. It is postulated that Mn(III)–Tf can exploit the same transferrin‐receptor‐dependent and ‐independent metabolic pathways used by hepatocytes to transport the iron analog Fe(III)–Tf. More specifically, it was investigated whether manganese delivered by transferrin could give MRI contrast in hepatocytes. Comparison of the T₁ and T₂ relaxation times of Mn(III)–Tf and Fe(III)–Tf over the same concentration range showed that the r₁ relaxivities of the two metalloproteins are the same in vitro, with little contribution from paramagnetic enhancement. The degree of manganese cell labeling following incubation for 2–7 h in 31.5 µm Mn(III)–Tf was comparable to that of hepatocytes incubated in 500 µm Mn²⁺ for 1 h. The intrinsic manganese tissue relaxivity between Mn(III)–Tf‐labeled and Mn²⁺‐labeled cells was found to be the same, consistent with Mn(III) being released from transferrin and reduced to Mn²⁺. For both treatment regimens, manganese uptake by hepatocytes appeared to saturate in the first 1–2 h of the incubation period and may explain why the efficiency of hepatocyte cell labeling by the two methods appeared to be comparable in spite of the ～16‐fold difference in effective manganese concentration. Hepatocytes continuously released manganese, as detected by MRI, and this was the same for both Mn²⁺‐ and Mn(III)–Tf‐labeled cells. Manganese release may be the result of normal hepatocyte function, much in the same way that hepatocytes excrete manganese into the bile in vivo. This approach exploits a biological process—namely receptor binding, endocytosis and endosomal acidification—to initiate the release of an MRI contrast agent, potentially conferring more specificity to the labeling process. The ubiquitous expression of transferrin receptors by eukaryotic cells should make Mn(III)–Tf particularly useful for manganese labeling of a wide variety of cells both in culture and in vivo. Published in 2008 by John Wiley & Sons, Ltd.     

Real‐time high‐resolution magnetic resonance tracking of macrophage subpopulations in a murine inflammation model: a pilot study with a commercially available cryogenic probe

Macrophages present different polarization states exhibiting distinct functions in response to environmental stimuli. However, the dynamic of their migration to sites of inflammation is not fully elucidated. Here we propose a real‐time in vivo cell tracking approach, using high‐resolution (HR)‐MRI obtained with a commercially available cryogenic probe (Cryoprobe?), to monitor trafficking of differently polarized macrophages after systemic injection into mice. Murine bone marrow‐derived mononuclear cells were differentiated ex vivo into nonpolarized M0, pro‐inflammatory M1 and immunomodulator M2 macrophage subsets and labeled with citrate‐coated anionic iron oxide nanoparticles (AMNP). These cells were subsequently intravenously injected to mice bearing calf muscle inflammation. Whole body migration dynamics of macrophage subsets was monitored by MRI at 4.7 T with a volume transmission/reception radiofrequency coil and macrophage infiltration to the inflamed paw was monitored with the cryogenic probe, allowing 3D spatial resolution of 50 µm with a scan time of only 10 min. Capture of AMNP was rapid and efficient regardless of macrophage polarization, with the highest uptake in M2 macrophages. Flow cytometry confirmed that macrophages preserved their polarization hallmarks after labeling. Migration kinetics of labeled cells differed from that of free AMNP. A preferential homing of M2‐polarized macrophages to inflammation sites was observed. Our in vivo HR‐MRI protocol highlights the extent of macrophage infiltration to the inflammation site. Coupled to whole body imaging, HR‐MRI provides quantitative information on the time course of migration of ex vivo‐polarized intravenously injected macrophages. Copyright © 2012 John Wiley & Sons, Ltd.     

The activin‐βA/BMP‐2 chimera AB204 is a strong stimulator of adipogenesis

Several of the bone morphogenetic proteins (BMPs) have been reported to induce white as well as brown adipogenesis. Here, we characterized the adipogenic potential of AB204, a recombinant chimeric protein of activin‐βA and BMP‐2, in in vitro, ex vivo and in vivo settings. BMP‐2 is generally known to promote adipogenesis. When compared with BMP‐2, which previously showed varying degrees of adipogenesis, AB204 displayed superior in vitro adipogenic differentiation of mouse 3 T3‐L1 pre‐adipocytes and human adipose‐derived stem cells (hASCs). Surprisingly, implantation of hASCs, preconditioned with AB204 for as short a time as 48 h, into the subcutaneous space of athymic nude mice effectively produced fat pads, but not with BMP‐2. When BMP‐2 and AB204 were injected intraperitoneally, AB204 promoted dramatic systemic adipogenesis of C57BL/6 mice on a high‐fat diet very effectively. The results implicate the novel clinical potential of AB204, including induction of fat tissue ex vivo or in vivo for tissue re‐engineering and regenerative medicinal purposes, more than any known natural protein ligand. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluating the effectiveness of transferrin receptor‐1 (TfR1) as a magnetic resonance reporter gene

Magnetic resonance (MR) reporter genes have the potential for tracking the biodistribution and fate of cells in vivo, thus allowing the safety, efficacy and mechanisms of action of cell‐based therapies to be comprehensively assessed. In this study, we evaluate the effectiveness of the iron importer transferrin receptor‐1 (TfR1) as an MR reporter gene in the model cell line CHO‐K1. Overexpression of the TfR1 transgene led to a reduction in the levels of endogenous TfR1 mRNA, but to a 60‐fold increase in total TfR1 protein levels. Although the mRNA levels of ferritin heavy chain‐1 (Fth1) did not change, Fth1 protein levels increased 13‐fold. The concentration of intracellular iron increased significantly, even when cells were cultured in medium that was not supplemented with iron and the amount of iron in the extracellular environment was thus at physiological levels. However, we found that, by supplementing the cell culture medium with ferric citrate, a comparable degree of iron uptake and MR contrast could be achieved in control cells that did not express the TfR1 transgene. Sufficient MR contrast to enable the cells to be detected in vivo following their administration into the midbrain of chick embryos was obtained irrespective of the reporter gene. We conclude that TfR1 is not an effective reporter and that, to track the biodistribution of cells with MR imaging in the short term, it is sufficient to simply culture cells in the presence of ferric citrate. Copyright © 2016 The Authors Contrast Media & Molecular Imaging Published by John Wiley & Sons Ltd.     

Ameloblasts serum‐free conditioned medium: bone morphogenic protein 4‐induced odontogenic differentiation of mouse induced pluripotent stem cells

Induced pluripotent stem (iPS) cells possess the ability of self‐renewal and can differentiate into cells of the three germ layers, both in vitro and in vivo. Here we report a new method to efficiently induce differentiation of mouse iPS cells into the odontogenic lineage. Using ameloblasts serum‐free conditioned medium (ASF–CM), we successfully generated ameloblast‐like cells from mouse iPS cells. Importantly, culturing mouse iPS cells in ASF–CM supplemented with BMP4 (ASF–BMP4) promoted odontogenic differentiation, which was evident by the upregulation of ameloblast‐specific as well as odontoblast‐specific genes. On the other hand, culturing mouse iPS cells in ASF–CM supplemented with noggin (ASF–noggin), an inhibitor of BMP4, abrogated this effect. These results suggest that mouse iPS cells can be induced by ASF–BMP4 to differentiate into ameloblast‐like and odontoblast‐like cells. The results of our study raise the possibility of using patient‐specific iPS cells for tooth regeneration in the future. Copyright © 2016 John Wiley & Sons, Ltd.     

Ultrasound‐responsive gene‐activated matrices for osteogenic gene therapy using matrix‐assisted sonoporation

Gene‐activated matrix (GAM)‐based therapeutics for tissue regeneration are limited by efficacy, the lack of spatiotemporal control and availability of target cells, all of which impact negatively on their translation to the clinic. Here, an advanced ultrasound‐responsive GAM is described containing target cells that facilitates matrix‐assisted sonoporation (MAS) to induce osteogenic differentiation. Ultrasound‐responsive GAMs consisting of fibrin/collagen hybrid‐matrices containing microbubbles, bone morphogenetic protein BMP2/7 coexpression plasmids together with C2C12 cells were treated with ultrasound either in vitro or following parenteral intramuscular implantation in vivo. Using direct measurement for alkaline phosphatase activity, von Kossa staining and immunohistochemical analysis for osteocalcin expression, MAS‐stimulated osteogenic differentiation was confirmed in the GAMs in vitro 7 days after treatment with ultrasound. At day 30 post‐treatment with ultrasound, ectopic osteogenic differentiation was confirmed in vivo using X‐ray microcomputed tomography and histological analysis. Osteogenic differentiation was indicated by the presence of ectopic bone structures in all animals treated with MAS. In addition, bone volumes in this group were statistically greater than those in the control groups. This novel approach of incorporating a MAS capability into GAMs could be exploited to facilitate ex vivo gene transfer with subsequent surgical implantation or alternatively provide a minimally invasive means of stimulating in situ transgene delivery for osteoinductive gene‐based therapies. Copyright © 2017 John Wiley & Sons, Ltd.     

Kidney volume quantification using contrast‐enhanced in vivo X‐ray micro‐CT in mice

The present study sought to establish a standard in vivo imaging procedure for mouse kidney anatomy evaluation using contrast‐enhanced high‐resolution X‐ray microtomography (micro‐CT). Micro‐CT estimation of kidney volume was compared with ex vivo measurement by micro‐CT and water displacement. Control values were obtained in four strains (BALB/c, C3H/HeN, 129/Sv and C57BL/6J) of healthy male and female mice aged 22 ± 2 weeks. An excellent correlation was found between in vivo and ex vivo kidney volumes (n = 26 mice; 52 kidneys; r = 0.96). In vivo measurement systematically overestimated ex vivo kidney volume by 28 ± 4%, while there was no significant difference between the ex vivo micro‐CT value and the true kidney volume on water displacement (2.3 ± 2.1%). In vivo kidney volume also correlated strongly with kidney weight and in vivo kidney length (n = 52 mice; 104 kidneys; r = 0.84, r = 0.92 respectively). Differences between strains were observed for kidney volume when comparing either kidney volume or kidney weight to body weight. In conclusion, this study demonstrated that contrast‐enhanced micro‐CT enables accurate in vivo measurement of kidney volume, length and thickness in mice. Reference parameters are reported for four strains. The technique provides a useful follow‐up research tool for mouse phenotyping and renal disease studies. Copyright © 2008 John Wiley & Sons, Ltd.     

Detection of vascular cell adhesion molecule‐1 expression with USPIO‐enhanced molecular MRI in a mouse model of cerebral ischemia

Vascular damage plays a critical role after stroke, leading notably to edema, hemorrhages and stroke recurrence. Tools to characterize the vascular lesion are thus a real medical need. In this context, the specific nanoparticular contrast agent P03011, an USPIO (ultrasmall superparamagnetic iron oxide) conjugated to a peptide that targets VCAM‐1 (vascular cell adhesion molecule‐1), was developed to detect this major component of the vascular inflammatory response. This study aimed to make the proof of concept of the capacity of this targeted USPIO to detect VCAM‐1 with MRI after cerebral ischemia in mouse. The time course of VCAM‐1 expression was first examined by immunohistochemistry in our model of cerebral ischemia–reperfusion. Secondly, P03011 or nontargeted USPIO P03007 were injected 5 h after ischemia (100 µmol iron kg^?1; i.v.) and in vivo and ex vivo MRI were performed 24 h after ischemia onset. Double labeling immunofluorescence was then performed on brain slices in order to detect both USPIO and VCAM‐1. VCAM‐1 expression was significantly up‐regulated 24 h after ischemia in our model. In animals receiving P03011, both in vivo and ex vivo MRI performed 24 h after ischemia onset showed hypointense foci which could correspond to iron particles. Histological analysis showed a co‐localization of the targeted USPIO and VCAM‐1. This study demonstrates that VCAM‐1 detection is possible with the USPIO P03011 in a model of cerebral ischemia. This kind of contrast agent could be an interesting clinical tool to characterize ischemic lesions in terms of vascular damage. Copyright © 2012 John Wiley & Sons, Ltd.     

[18F]‐FBEM,a tracer targeting cell‐surface protein thiols for cell trafficking imaging

We used [¹⁸F]‐4‐fluorobenzamido‐N‐ethylamino‐maleimide ([¹⁸F]‐FBEM) to radiolabel cells ex vivo for in vivo positron emission tomography (PET) in order to assess cell trafficking in mice. In contrast to commonly used imaging agents, [¹⁸F]‐FBEM forms a covalent bond with thiol groups present on the cells surface. The stability of the probe in aqueous medium was tested at different pH values and cross‐experiment showed that thiol‐labeling efficiency was retained (at least) up to pH 9. The labeling procedure did not affect significantly the cell viability. To illustrate the procedure, PET images of living mice injected intravenously with labeled T lymphocytes were obtained. They showed the expected cell homing in the spleen that was absent in mice injected with free label. Copyright © 2013 John Wiley & Sons, Ltd.     

Mesenchymal stem cell labeling and in vitro MR characterization at 1.5 T of new SPIO contrast agent: Molday ION Rhodamine‐B™

In vivo detection of transplanted stem cells is requisite for improving stem cell‐based treatments by developing a thorough understanding of their therapeutic mechanisms. MRI tracking of magnetically labeled cells is non‐invasive and is suitable for longitudinal studies. Molday ION Rhodamine‐B? (MIRB) is a new superparamagnetic iron oxide (SPIO) contrast agent specifically formulated for cell labeling and is readily internalized by non‐phagocytic cells. This investigation characterizes mesenchymal stem cell (MSC) labeling and MR imaging properties of this new SPIO agent. Effects of MIRB on MSC viability and differentiation as well as cellular loading properties were assessed for MSC labeled with MIRB at concentrations from 5 to 100 µg Fe/ml. Labeled MSC were evaluated, in vitro, on a clinical 1.5 T MRI. Optimal scanning sequences and imaging parameters were determined based on contrast‐to‐noise ratio and contrast modulation. Relaxation rates (1/T₂*) for gradient‐echo sequences were approximated and an idealized limit of detection was established. MIRB labeling did not affect MSC viability or the ability to differentiate into either bone or fat. Labeling efficiency was found to be approximately 95% for labeling concentrations at or above 20 µg Fe/ml. Average MIRB per MSC ranged from 0.7 pg Fe for labeling MIRB concentration of 5 µg Fe/ml and asymptotically approached a value of 20–25 pg Fe/MSC as labeling concentration increased to 100 µg Fe/ml. MRI analysis of MIRB MSC revealed long echo time, gradient echo sequences to provide the most sensitivity. Limit of detection for gradient echo sequences was determined to be less than 1000 MSC, with approximately 15 pg Fe/MSC (labeled at 20µg Fe/ml). These investigations have laid the groundwork and established feasibility for the use of this contrast agent for in vivo MRI detection of MSC. Properties evaluated in this study will be used as a reference for tracking labeled MSC for in vivo studies. Copyright © 2010 John Wiley & Sons, Ltd.     

Epidermal‐like architecture obtained from equine keratinocytes in three‐dimensional cultures

Despite the high prevalence of skin conditions in the horse, there is a dearth of literature on the culture and biology of equine skin cells, and this is partially attributable to the lack of suitable in vitro skin models. The objective of this study was to develop a three‐dimensional (3D) culture system that would support the proliferation and differentiation of equine keratinocytes, similar to that observed in natural epidermis. Cell monolayers were obtained from explants of equine skin and serially passaged as highly pure keratinocyte populations (> 95% of cells), based on their expression of cytokeratins, including CK‐5 and CK‐14, which are associated in vivo with proliferating keratinocyte populations. Explant‐derived keratinocytes were seeded into Alvetex? 3D tissue scaffolds for 30 days under conditions that promote cell differentiation. Ultrastructural, immunohistochemical and biochemical analyses revealed that keratinocytes within scaffolds were able to proliferate and attain tissue polarity, including differentiation into basal and suprabasal layers. The basal layer contained distinct cuboidal cells with large nuclei and stained for proliferative markers such as CK‐5 and CK‐14. In contrast, the suprabasal layers consisted of cells with distinct polyhedral morphology, abundant cytoplasmic processes and desmosomes indicative of stratum spinosum and distinct flattened cornified cells that expressed involucrin, a marker of terminal differentiation. Thus, keratinocytes derived from primary equine skin explants were able to attain epidermal‐like architecture in culture. This novel system could provide a very useful tool for modelling skin diseases, drug testing/toxicity studies and, potentially, equine regenerative medicine. Copyright © 2016 John Wiley & Sons, Ltd.     

Carbohydrate‐deficient transferrin determined in blood microsamples from healthy newborns by using capillary zone electrophoresis

Objective. There is a paucity of studies on quantitative determination of carbohydrate‐deficient transferrin (CDT) in newborns. The aim of our study was therefore to determine CDT concentrations in newborns by using capillary zone electrophoresis (CZE). Material and methods. Capillary blood was collected from the heels of 28 at‐term healthy newborns, simultaneously with the Guthrie card screening. Forty‐seven adults were examined as controls. CZE separations were performed with a P/ACE MDQ capillary electropherograph in uncoated fused‐silica capillaries using a commercial reagent kit. After iron saturation, the samples were loaded by application of 0.5?psi for 15?s, and separated under 28kV with UV detection. All relevant transferrin (Tf) glycoforms were separated within 7?min. CDT quantification (%CDT) was carried out by calculating the percentage ratio between the sum of the peak areas of CDT‐related glycoforms and the sum of peak areas of all Tf glycoforms. Results. In most cases, good separations of Tf glycoforms were obtained. In the newborns the %CDT was 0.51 versus 0.66 in adults (difference not statistically significant). Trisialo‐Tf concentration was significantly lower in newborns (3.20) than in adults (4.11). Furthermore, pentasialo‐Tf appeared to be lower in newborns (7.30) than in adults (14.00), but because complete separation of the peaks of tetrasialo‐ and pentasialo‐Tf was not always possible, this finding could not be confirmed statistically. Conclusions. CZE showed definite advantages in terms of volume of blood to be collected, simplicity and standardization of analysis and, because of the direct detection of the separated zones, accuracy of quantification. The present study provides the basic information in the search for glycosylation defects in newborns.     

Functionalized single‐walled carbon nanotubes containing traces of iron as new negative MRI contrast agents for in vivo imaging

Single‐walled carbon nanotubes (SWCNTs) containing traces of iron oxide were functionalized by noncovalent lipid‐PEG or covalent carboxylic acid function to supply new efficient MRI contrast agents for in vitro and in vivo applications. Longitudinal (r₁) and transversal (r₂) water proton relaxivities were measured at 300 MHz, showing a stronger T₂ feature as an MRI contrast agent (r₂/r₁ = 190 for CO₂H functionalisation). The r₂ relaxivity was demonstrated to be correlated to the presence of iron oxide in the SWNT‐carboxylic function COOH, in comparison to iron‐free ones. Biodistribution studies on mice after a systemic injection showed a negative MRI contrast in liver, suggesting the presence of the nanotubes in this organ until 48 h after i.v. injection. The presence of carbon nanotubes in liver was confirmed after ex vivo carbon extraction. Finally, cytotoxicity studies showed no apparent effect owing to the presence of the carbon nanotubes. The functionalized carbon nanotubes were well tolerated by the animals at the dose of 10 µg g^?1 body weight. Copyright © 2012 John Wiley & Sons, Ltd.     

Adipose‐ and bone marrow‐derived mesenchymal stem cells display different osteogenic differentiation patterns in 3D bioactive glass‐based scaffolds

Mesenchymal stem cells can be isolated from a variety of different sources, each having their own peculiar merits and drawbacks. Although a number of studies have been conducted comparing these stem cells for their osteo‐differentiation ability, these are mostly done in culture plastics. We have selected stem cells from either adipose tissue (ADSCs) or bone marrow (BMSCs) and studied their differentiation ability in highly porous three‐dimensional (3D) 45S5 Bioglass®‐based scaffolds. Equal numbers of cells were seeded onto 5 × 5 × 4 mm³ scaffolds and cultured in vitro, with or without osteo‐induction medium. After 2 and 4 weeks, the cell–scaffold constructs were analysed for cell number, cell spreading, viability, alkaline phosphatase activity and osteogenic gene expression. The scaffolds with ADSCs displayed osteo‐differentiation even without osteo‐induction medium; however, with osteo‐induction medium osteogenic differentiation was further increased. In contrast, the scaffolds with BMSCs showed no osteo‐differentiation without osteo‐induction medium; after application of osteo‐induction medium, osteo‐differentiation was confirmed, although lower than in scaffolds with ADSCs. In general, stem cells in 3D bioactive glass scaffolds differentiated better than cells in culture plastics with respect to their ALP content and osteogenic gene expression. In summary, 45S5 Bioglass‐based scaffolds seeded with ADSCs are well‐suited for possible bone tissue‐engineering applications. Induction of osteogenic differentiation appears unnecessary prior to implantation in this specific setting. Copyright © 2013 John Wiley & Sons, Ltd.     

Mesenchymal stem cell expression of SDF‐1β synergizes with BMP‐2 to augment cell‐mediated healing of critical‐sized mouse calvarial defects

Bone has the potential for spontaneous healing. This process, however, often fails in patients with comorbidities. Tissue engineering combining functional cells, biomaterials and osteoinductive cues may provide alternative treatment strategies. We have recently demonstrated that stromal cell‐derived factor‐1β (SDF‐1β) works in concert with bone morphogenetic protein‐2 (BMP‐2) to potentiate osteogenic differentiation of bone marrow‐derived mesenchymal stem/stromal cells (BMSCs). Here, we test the hypothesis that SDF‐1β overexpressed in Tet‐Off‐SDF‐1β BMSCs, delivered on acellular dermal matrix (ADM), synergistically augments BMP‐2‐induced healing of critical‐sized mouse calvarial defects. BMSC therapies alone showed limited bone healing, which was increased with co‐delivery of BMP‐2. This was further enhanced in Tet‐Off‐SDF‐1β BMSCs + BMP‐2. Only limited BMSC retention on ADM constructs was observed after 4 weeks in vivo, which was increased with BMP‐2 co‐delivery. In vitro cell proliferation studies showed that supplementing BMP‐2 to Tet‐Off BMSCs significantly increased the cell number during the first 24 h. Consequently, the increased cell numbers decreased the detectable BMP‐2 levels in the medium, but increased cell‐associated BMP‐2. The data suggest that SDF‐1β provides synergistic effects supporting BMP‐2‐induced, BMSC‐mediated bone formation and appears suitable for optimization of bone augmentation in combination therapy protocols. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterization of biomaterial‐free cell sheets cultured from human oral mucosal epithelial cells

The purpose of this study was to report the characteristics of biomaterial‐free sheets cultured from human oral mucosal epithelial cells without fibrin support, in vitro and after transplantation to limbal‐deficient models. Human oral mucosal epithelial cells and limbal epithelial cells were cultured for 2 weeks, and the colony‐forming efficiency (CFE) rates were compared. Markers of stem cells (p63), cell proliferation (Ki‐67) and epithelial differentiation (cytokeratin; K1, K3, K4, K13) were observed in colonies and in biomaterial‐free sheets. Biomaterial‐free sheets which had been detached with 1% dispase or biomaterial‐free sheets generated by fibrin support were transplanted to 12 limbal‐deficient rabbit models. In vitro cell viability, in vivo stability and cytokeratin characteristics of biomaterial‐free sheets were compared with those of sheets formed by fibrin‐coated culture 1 week after transplantation. Mean CFE rate was significantly higher in human oral mucosal epithelial cells (44.8%) than in human limbal epithelial cells(17.7%). K3 and K4 were well expressed in both colonies and sheets. Biomaterial‐free sheets had two to six layers of stratified cells and showed an average of 79.8% viable cells in the sheets after detachment. Cytokeratin expressions of biomaterial‐free sheets were comparable to those of sheets cultured by fibrin support, in limbal‐deficient models. Both p63 and Ki‐67 were well expressed in colonies, isolated sheets and sheets transplanted to limbal‐deficient models. Our results suggest that biomaterial‐free sheets cultured from human oral mucosal epithelial cells without fibrin support can be an alternative option for cell therapy in use for the treatment of limbal‐deficient diseases. Copyright © 2014 John Wiley & Sons, Ltd.