Magnetic resonance imaging of superparamagnetic iron oxide-labeled macrophage infiltrates in acute-phase renal ischemia-reperfusion mouse model

Highly Sensitive Early Diagnosis of Kidney Damage Using Renal Clearable Zwitterion-Coated Ferrite Nanoprobe via Magnetic Resonance Imaging In Vivo

Iron oxide nanoprobes exhibit substantial potential in magnetic resonance imaging (MRI) of kidney diseases and can eliminate the nephrotoxicity of gadolinium-based contrast agents (GBCAs). Nevertheless, there is an extreme shortage of highly sensitive and renal clearable iron oxide nanoprobes suitable for early kidney damage detection through MRI. Herein, a renal clearable ultra-small ferrite nanoprobe (UMFNPs@ZDS) is proposed for highly sensitive early diagnosis of kidney damage via structural and functional MRI in vivo for the first time. The nanoprobe comprises a ferrite core coated with a zwitterionic layer, and possesses a high T1 relaxivity (12.52 mm-1s-1), a small hydrodynamic size (6.43 nm), remarkable water solubility, excellent biocompatibility, and impressive renal clearable ability. In a rat model of unilateral ureteral obstruction (UUO), the nanoprobe-based MRI can not only accurately visualize the locations of renal injury, but also provide comprehensive functional data including peak value, peak time, relative renal function (RRF), and clearance percentage via MRI. The findings prove the immense potential of ferrite nanoprobes as a superior alternative to GBCAs for the early diagnosis of kidney damage.

Nanotechnology-Assisted Cell Tracking

The usefulness of nanoparticles (NPs) in the diagnostic and/or therapeutic sector is derived from their aptitude for navigating intra- and extracellular barriers successfully and to be spatiotemporally targeted. In this context, the optimization of NP delivery platforms is technologically related to the exploitation of the mechanisms involved in the NP-cell interaction. This review provides a detailed overview of the available technologies focusing on cell-NP interaction/detection by describing their applications in the fields of cancer and regenerative medicine. Specifically, a literature survey has been performed to analyze the key nanocarrier-impacting elements, such as NP typology and functionalization, the ability to tune cell interaction mechanisms under in vitro and in vivo conditions by framing, and at the same time, the imaging devices supporting NP delivery assessment, and consideration of their specificity and sensitivity. Although the large amount of literature information on the designs and applications of cell membrane-coated NPs has reached the extent at which it could be considered a mature branch of nanomedicine ready to be translated to the clinic, the technology applied to the biomimetic functionalization strategy of the design of NPs for directing cell labelling and intracellular retention appears less advanced. These approaches, if properly scaled up, will present diverse biomedical applications and make a positive impact on human health.

Surface coating determines the inflammatory potential of magnetite nanoparticles in murine renal podocytes and mesangial cells

Primary renal podocytes are more susceptible to MNPs exposure than primary renal mesangial cells.

Current Perspective on In Vivo Molecular Imaging of Immune Cells

Contemporaneous development of improved immune cell-based therapies, and powerful imaging tools, has prompted growth in technologies for immune cell tracking in vivo. Over the past couple of decades, imaging tools such as magnetic resonance imaging (MRI) and optical imaging have successfully monitored the trafficking patterns of therapeutic immune cells and assisted the evaluation of the success or failure of immunotherapy. Recent advancements in imaging technology have made imaging an indispensable module of immune cell-based therapies. In this review, emerging applications of non-radiation imaging modalities for the tracking of a range of immune cells are discussed. Applications of MRI, NIR, and other imaging tools have demonstrated the potential of non-invasively surveying the fate of both phagocytic and non-phagocytic immune cells in vivo.

Visualization of Macrophage Recruitment to Inflammation Lesions using Highly Sensitive and Stable Radionuclide-Embedded Gold Nanoparticles as a Nuclear Bio-Imaging Platform

Reliable and sensitive imaging tools are required to track macrophage migration and provide a better understating of their biological roles in various diseases. Here, we demonstrate the possibility of radioactive iodide-embedded gold nanoparticles (RIe-AuNPs) as a cell tracker for nuclear medicine imaging. To demonstrate this utility, we monitored macrophage migration to carrageenan-induced sites of acute inflammation in living subjects and visualized the effects of anti-inflammatory agents on this process. Macrophage labeling with RIe-AuNPs did not alter their biological functions such as cell proliferation, phenotype marker expression, or phagocytic activity. In vivo imaging with positron-emission tomography revealed the migration of labeled macrophages to carrageenan-induced inflammation lesions 3 h after transfer, with highest recruitment at 6 h and a slight decline of radioactive signal at 24 h; these findings were highly consistent with the data of a bio-distribution study. Treatment with dexamethasone (an anti-inflammation drug) or GSK5182 (an ERRγ inverse agonist) hindered macrophage recruitment to the inflamed sites. Our findings suggest that a cell tracking strategy utilizing RIe-AuNPs will likely be highly useful in research related to macrophage-related disease and cell-based therapies.

CD163-Macrophages Are Involved in Rhabdomyolysis-Induced Kidney Injury and May Be Detected by MRI with Targeted Gold-Coated Iron Oxide Nanoparticles

Macrophages play an important role in rhabdomyolysis-acute kidney injury (AKI), although the molecular mechanisms involved in macrophage differentiation are poorly understood. We analyzed the expression and regulation of CD163, a membrane receptor mainly expressed by anti-inflammatory M2 macrophages, in rhabdomyolysis-AKI and developed targeted probes for its specific detection in vivo by MRI. Intramuscular injection of glycerol in mice promoted an early inflammatory response, with elevated proportion of M1 macrophages, and partial differentiation towards a M2 phenotype in later stages, where increased CD163 expression was observed. Immunohistological studies confirmed the presence of CD163-macrophages in human rhabdomyolysis-AKI. In cultured macrophages, myoglobin upregulated CD163 expression via HO-1/IL-10 axis. Moreover, we developed gold-coated iron oxide nanoparticles vectorized with an anti-CD163 antibody that specifically targeted CD163 in kidneys from glycerol-injected mice, as determined by MRI studies, and confirmed by electron microscopy and immunological analysis. Our findings are the first to demonstrate that CD163 is present in both human and experimental rhabdomyolysis-induced AKI, suggesting an important role of this molecule in this pathological condition. Therefore, the use of probes targeting CD163-macrophages by MRI may provide important information about the cellular composition of renal lesion in rhabdomyolysis.

Noninvasive monitoring of mouse renal allograft rejection using micro-CT

Purpose

Acute renal graft rejection can only be definitively diagnosed by renal biopsy. However, biopsies carry a risk of renal transplant injury and loss. Micro-CT is widely used in preclinical studies of small animals. Here, we propose micro-CT could noninvasively monitor and evaluate renal location and function in a mouse kidney transplant model.

Methods

Orthotopic kidney transplantation was performed in a BALB/c -to- C57BL/6j or C57BL/6j-to- C57BL/6j mouse model. After optimizing imaging techniques, five mice were imaged with micro-CT and the findings were verified histologically.

Results

Micro-CT can monitor and evaluate renal location and function after orthotopic kidney transplantation. There were no mice deaths while renal transplants were failure.

Conclusion

We propose that graft micro-CT imaging is a new option that is noninvasive and specific, and can aid in early detection and follow-up of acute renal rejection. This method is potentially useful to improve posttransplant rejection monitoring.

C5b-9-targeted molecular MR imaging in rats with Heymann nephritis: a new approach in the evaluation of nephrotic syndrome

Membranous nephropathy (MN) is the major cause of adult nephrotic syndrome, which severely affects patients’ quality of life. Currently, percutaneous renal biopsy is required to definitively diagnose MN. However, this technique is invasive and may cause severe complications. Therefore, an urgent clinical need exists for dynamic noninvasive monitoring of the renal state. In-depth molecular imaging studies could assist in finding a solution. Membrane attack complex C5b-9 is the key factor in the development of MN, and this protein primarily deposits in the glomerulus. The present study bound polyclonal antibodies to C5b-9 with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles to obtain C5b-9-targeted magnetic resonance molecular imaging probes. The probes were injected intravenously into rats with Heymann nephritis, a classic disease model of MN. The signal intensity in the T2*-weighted imaging of kidneys in vivo using 7.0 Tesla magnetic resonance imaging decreased significantly 24 hours after injection compared to the untargeted and control groups. This signal change was consistent with the finding of nanoparticle deposits in pathological glomeruli. This study demonstrated a novel molecular imaging technique for the assessment of MN.

Clodronate-superparamagnetic iron oxide-containing liposomes attenuate renal injury in rats with severe acute pancreatitis

BACKGROUND AND OBJECTIVE

It has been shown that macrophages play an important role in the development of severe acute pancreatitis (SAP), and eventually lead to multiple organ failure (MOF). Clodronate-liposome selectively depleted macrophages. This study was to investigate the role of renal macrophage infiltration in acute renal injury in rats with SAP and to evaluate the potential of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) for diagnosis.

METHODS

Superparamagnetic Fe3O4 nanoparticles were prepared by chemical coprecipitation. SPIO-liposomes and SPIO-clodronate-liposomes were prepared by the thin film method. SAP models were prepared by injection of sodium taurocholate into the subcapsular space of rat pancreas. Sprague-Dawley rats were randomly divided into a control group, SAP plus SPIO-liposome (P) group, and SAP plus SPIO-clodronate-containing liposome (T) group. Kidney injury was evaluated by T2-weighted MRI scan. The levels of serum amylase (SAM), blood urea nitrogen (BUN), and serum creatinine (SCr) were measured by an automated enzymatic method. Serum tumor necrosis factor-α (TNF-α) was measured by enzyme-linked immunosorbent assay (ELISA). Pathological changes in the pancreas and kidney were observed using hematoxylin and eosin (H&E) staining, while cell apoptosis was detected with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. In addition, the macrophage markers (CD68) of the renal tissue were detected with immunohistochemistry.

RESULTS

The pathological changes in the pancreas and kidneys of rats in the T group were milder than those in the P group. The MRI signal intensity of the kidneys in the P and T groups was significantly lower than that in the control group. There were significant changes in the two experimental groups (P<0.01). The levels of SAM, Bun, SCr, and TNF-α in rats in the P group were higher than those in the control group (P<0.01) and in the T group (P<0.01). The apoptosis of the kidney in the T group was higher than that in the P group at 2 and 6 h (P<0.01).

CONCLUSIONS

Clodronate-containing liposomes protected against renal injury in SAP rats, and SPIO can be used as a tracer for MRI examination to detect renal injury in SAP rats. SPIO-aided MRI provided an efficient non-invasive way to monitor the migration of macrophages after renal injury in rats with SAP.

Multimodal cell tracking of a spontaneous metastasis model: comparison between MRI, electron paramagnetic resonance and bioluminescence

MRI cell tracking is a promising technique for tracking various cell types in living animals. Usually, cells are incubated with iron oxides so that the particles are taken up before the cells are injected in vivo. In the present study, we aimed to monitor migration of luciferase-expressing mouse renal cancer cells (RENCA-luc) after intrarenal or intrasplenic injection. These cells were labelled using Molday Ion Rhodamine B (MIRB) fluorescent superparamagnetic iron oxide particles. Their fate after injection was first assessed using ex vivo X-band electron paramagnetic resonance (EPR) spectroscopy. This biodistribution study showed that RENCA-luc cells quickly colonized the lungs and the liver after intrarenal and intrasplenic injection, respectively. Bioluminescence imaging (BLI) studies confirmed that this cell line preferentially metastasized to these organs. Early tracking of labelled RENCA-luc cells in the liver using high-field MRI (11.7 T) was not feasible because of a lack of sensitivity. MRI of MIRB-labelled RENCA-luc cells after injection in the left kidney was then performed. T2 - and T2 *-weighted images showed that the labelled cells induced hypointense signals at the injection site. Nevertheless, the hypointense regions tended to disappear after several days, mainly owing to dilution of the MIRB iron oxides with cell proliferation. In conclusion, EPR is well adapted to ex vivo analysis of tissues after cell tracking experiments and allows short-term monitoring of metastasizing cells. MRI is a suitable tool for checking labelled cells at their injection site, but dilution of the iron oxides owing to cell division remains a major limitation. BLI remains the most suitable technique for long-term monitoring of metastatic cells.

Preferential macrophage recruitment and polarization in LPS-induced animal model for COPD: noninvasive tracking using MRI

Noninvasive imaging of macrophages activity has raised increasing interest for diagnosis of chronic obstructive respiratory diseases (COPD), which make them attractive vehicles to deliver contrast agents for diagnostic or drugs for therapeutic purposes. This study was designed to monitor and evaluate the migration of differently polarized M1 and M2 iron labeled macrophage subsets to the lung of a LPS-induced COPD animal model and to assess their polarization state once they have reached the inflammatory sites in the lung after intravenous injection. Ex vivo polarized bone marrow derived M1 or M2 macrophages were first efficiently and safely labeled with amine-modified PEGylated dextran-coated SPIO nanoparticles and without altering their polarization profile. Their biodistribution in abdominal organs and their homing to the site of inflammation in the lung was tracked for the first time using a free-breathing non-invasive MR imaging protocol on a 4.7T magnet after their intravenous administration. This imaging protocol was optimized to allow both detection of iron labeled macrophages and visualization of inflammation in the lung. M1 and M2 macrophages were successfully detected in the lung starting from 2 hours post injection with no variation in their migration profile. Quantification of cytokines release, analysis of surface membrane expression using flow cytometry and immunohistochemistry investigations confirmed the successful recruitment of injected iron labeled macrophages in the lung of COPD mice and revealed that even with a continuum switch in the polarization profile of M1 and M2 macrophages during the time course of inflammation a balanced number of macrophage subsets predominate.

Nanosized contrast agents to noninvasively detect kidney inflammation by magnetic resonance imaging

Several molecular imaging methods have been developed that use nanosized contrast agents to detect markers of inflammation within tissues. Kidney inflammation contributes to disease progression in a wide range of autoimmune and inflammatory diseases, and a biopsy is currently the only method of definitively diagnosing active kidney inflammation. However, the development of new molecular imaging methods that use contrast agents capable of detecting particular immune cells or protein biomarkers will allow clinicians to evaluate inflammation throughout the kidneys and to assess a patient's response to immunomodulatory drugs. These imaging tools will improve our ability to validate new therapies and to optimize the treatment of individual patients with existing therapies. This review describes the clinical need for new methods of monitoring kidney inflammation and recent advances in the development of nanosized contrast agents for the detection of inflammatory markers of kidney disease.