Ex vivo magnetic resonance imaging of transplanted hepatocytes in a rat model of acute liver failure

The Initial Cardiac Tissue Response to Cryopreserved Allogeneic Adipose Tissue-Derived Mesenchymal Stromal Cells in Rats with Chronic Ischemic Cardiomyopathy

Mesenchymal stromal cells have proven capable of improving cardiac pump function in patients with chronic heart failure, yet little is known about their mode of action. The aim of the study was to investigate the short-term effect of cryopreserved allogeneic rat adipose tissue-derived stromal cells (ASC) on cardiac composition, cellular subpopulations, and gene transcription in a rat model of chronic ischemic cardiomyopathy (ICM). Myocardial infarction (MI) was induced by permanent ligation of the left anterior descending coronary artery. After 6 weeks, the rats were treated with ASCs, saline, or no injection, using echo-guided trans-thoracic intramyocardial injections. The cardiac tissue was subsequently collected for analysis of cellular subpopulations and gene transcription 3 and 7 days after treatment. At day 3, an upregulation of genes associated with angiogenesis were present in the ASC group. On day 7, increases in CCR2+ and CD38+ macrophages (p = 0.047 and p = 0.021), as well as in the CD4/CD8 lymphocyte ratio (p = 0.021), were found in the ASC group compared to the saline group. This was supported by an upregulation of genes associated with monocytes/macrophages. In conclusion, ASC treatment initiated an immune response involving monocytes/macrophages and T-cells and induced a gene expression pattern associated with angiogenesis and monocyte/macrophage differentiation.

Applications of Nanobiomaterials in the Therapy and Imaging of Acute Liver Failure

This review focuses on the therapeutic mechanisms, targeting strategies of various nanomaterials in acute liver failure, and recent advances of diverse nanomaterials for acute liver failure therapy, diagnosis, and imaging. This review provides an outlook on the applications of nanomaterials, especially on the new horizons in acute liver failure therapy, and inspires broader interests across various disciplines. Acute liver failure (ALF), a fatal clinical disease featured with overwhelming hepatocyte necrosis, is a grand challenge in global health. However, a satisfactory therapeutic option for curing ALF is still absent, other than liver transplantation. Nanobiomaterials are currently being developed for the diagnosis and treatment of ALF. The liver can sequester most of nanoparticles from blood circulation, which becomes an intrinsic superiority for nanobiomaterials targeting hepatic diseases. Nanobiomaterials can enhance the bioavailability of free drugs, thereby significantly improving the therapeutic effects in ALF. Nanobiomaterials can also increase the liver accumulation of therapeutic agents and enable more effective targeting of the liver or specific liver cells. In addition, stimuli-responsive, optical, or magnetic nanomaterials exhibit great potential in the therapeutical, diagnostic, and imaging applications in ALF. Therefore, therapeutic agents in combination with nanobiomaterials increase the specificity of ALF therapy, diminish adverse systemic effects, and offer a multifunctional theranostic platform. Nanobiomaterial holds excellent significance and prospects in ALF theranostics. In this review, we summarize the therapeutic mechanisms and targeting strategies of various nanobiomaterials in ALF. We highlight recent developments of diverse nanomedicines for ALF therapy, diagnosis, and imaging. Furthermore, the challenges and future perspectives in the theranostics of ALF are also discussed.

Dose-, treatment- and time-dependent toxicity of superparamagnetic iron oxide nanoparticles on primary rat hepatocytes

AIM

As a first study in literature, to investigate concentration-dependent (0-400 μg/ml) and exposure-dependent (single dosing vs cumulative dosing) effects of superparamagnetic iron oxide nanoparticles (d = 10 nm) on primary rat hepatocytes in a time-dependent manner.

MATERIALS & METHODS

Sandwich-cultured hepatocyte model was used to evaluate viability, hepatocyte specific functions and reactive oxygen species level.

RESULTS

In terms of all parameters, generally statistically more significant effects were observed in a concentration- and time-dependent manner. In terms of hepatocyte-specific functions, cumulative dosing caused significantly (p < 0.05) more deleterious effects at 48th hour.

CONCLUSION

A combination of various biomarkers should be employed for the evaluation of the effect of superparamagnetic iron oxide nanoparticles on liver, and each biomarker should be analyzed in a time- and exposure-dependent manner.

Biodistribution and Clearance of Stable Superparamagnetic Maghemite Iron Oxide Nanoparticles in Mice Following Intraperitoneal Administration

Nanomedicine is an emerging field with great potential in disease theranostics. We generated sterically stabilized superparamagnetic iron oxide nanoparticles (s-SPIONs) with average core diameters of 10 and 25 nm and determined the in vivo biodistribution and clearance profiles. Healthy nude mice underwent an intraperitoneal injection of these s-SPIONs at a dose of 90 mg Fe/kg body weight. Tissue iron biodistribution was monitored by atomic absorption spectroscopy and Prussian blue staining. Histopathological examination was performed to assess tissue toxicity. The 10 nm s-SPIONs resulted in higher tissue-iron levels, whereas the 25 nm s-SPIONs peaked earlier and cleared faster. Increased iron levels were detected in all organs and body fluids tested except for the brain, with notable increases in the liver, spleen, and the omentum. The tissue-iron returned to control or near control levels within 7 days post-injection, except in the omentum, which had the largest and most variable accumulation of s-SPIONs. No obvious tissue changes were noted although an influx of macrophages was observed in several tissues suggesting their involvement in s-SPION sequestration and clearance. These results demonstrate that the s-SPIONs do not degrade or aggregate in vivo and intraperitoneal administration is well tolerated, with a broad and transient biodistribution. In an ovarian tumor model, s-SPIONs were shown to accumulate in the tumors, highlighting their potential use as a chemotherapy delivery agent.

Real-time MRI for precise and predictable intra-arterial stem cell delivery to the central nervous system

Stem cell therapy for neurological disorders reached a pivotal point when the efficacy of several cell types was demonstrated in small animal models. Translation of stem cell therapy is contingent upon overcoming the challenge of effective cell delivery to the human brain, which has a volume ∼1000 times larger than that of the mouse. Intra-arterial injection can achieve a broad, global, but also on-demand spatially targeted biodistribution; however, its utility has been limited by unpredictable cell destination and homing as dictated by the vascular territory, as well as by safety concerns. We show here that high-speed MRI can be used to visualize the intravascular distribution of a superparamagnetic iron oxide contrast agent and can thus be used to accurately predict the distribution of intra-arterial administered stem cells. Moreover, high-speed MRI enables the real-time visualization of cell homing, providing the opportunity for immediate intervention in the case of undesired biodistribution.

Hepatocyte Transplantation in Special Populations: Clinical Use in Children

Orthotopic liver transplantation remains the only proven cure for end-stage liver failure. Despite significant advances in the field, the clinical demand for donor organs far outweighs the supply. Hepatocyte transplantation has been proposed as an alternative approach to whole liver transplant in select diseases. Several international centers have reported experimental trials of human hepatocyte transplantation in acute liver failure and liver-based metabolic disorders. This chapter provides an introduction to hepatocyte transplantation from both a technical and clinical perspective. We will also focus on the special needs of pediatric patients, since historically the majority of clinical hepatocyte transplants have involved infants and children.

MR tracking of SPIO-labeled mesenchymal stem cells in rats with liver fibrosis could not monitor the cells accurately

Our previous study showed that in vivo magnetic resonance (MR) imaging is effective in tracking superparamagnetic iron oxide (SPIO)-labeled bone marrow mesenchymal stem cells (BMSCs) in rats with liver fibrosis. SPIO-labeling-induced signal reduction on MR images was completely reversed within 15 days after transplantation. It is still unclear whether the signal changes in MR imaging could reflect the number of transplanted cells in the liver. In the present study, BMSCs of male rats were doubly labeled with enhanced green fluorescent protein (EGFP) and SPIO and injected intravascularly into female rats with liver fibrosis. At different time points after injection, MR imaging was performed. The distribution of SPIO particles and EGFP-positive cells was determined by Prussian blue staining and EGFP immunohistochemistry, respectively. The distribution of transplanted BMSCs in various organs was assessed by detection of the SRY gene using real-time quantitative PCR. At 15 days post transplantation, the numbers of transplanted cells were significantly decreased in the lung, kidney, spleen and muscle, but not liver and heart, in comparison with those at 7 days after transplantation. EGFP staining-positive cells were observed in the liver intralobular parenchyma, while Prussian blue staining was negative at 42 days after transplantation. Taken together, SPIO particles and EGFP-labeled BMSCs show a different tissue distribution pattern in rats with liver fibrosis after a long-term period of monitoring. SPIO-based MR imaging may not be suitable for long-term tracking of transplanted BMSCs in vivo.

Magnetic cell labeling of primary and stem cell-derived pig hepatocytes for MRI-based cell tracking of hepatocyte transplantation

Pig hepatocytes are an important investigational tool for optimizing hepatocyte transplantation schemes in both allogeneic and xenogeneic transplant scenarios. MRI can be used to serially monitor the transplanted cells, but only if the hepatocytes can be labeled with a magnetic particle. In this work, we describe culture conditions for magnetic cell labeling of cells from two different pig hepatocyte cell sources; primary pig hepatocytes (ppHEP) and stem cell-derived hepatocytes (PICM-19FF). The magnetic particle is a micron-sized iron oxide particle (MPIO) that has been extensively studied for magnetic cell labeling for MRI-based cell tracking. ppHEP could endocytose MPIO with labeling percentages as high as 70%, achieving iron content as high as ~55 pg/cell, with >75% viability. PICM-19FF had labeling >97%, achieving iron content ~38 pg/cell, with viability >99%. Extensive morphological and functional assays indicated that magnetic cell labeling was benign to the cells. The results encourage the use of MRI-based cell tracking for the development and clinical use of hepatocyte transplantation methodologies. Further, these results generally highlight the importance of functional cell assays in the evaluation of contrast agent biocompatibility.

Hepatocyte transplantation attenuates the course of acute liver failure induced by thioacetamide in Lewis rats

Acute liver failure (ALF) is a clinical syndrome resulting from widespread damage of hepatocytes, with extremely high mortality rate. Urgent orthotopic liver transplantation was shown to be the most effective therapy for ALF but this treatment option is limited by scarcity of donor organs. Therefore, hepatocyte transplantation (Tx) has emerged as a new therapeutical measure for ALF, however, the first clinical applications proved unsatisfactory. Apparently, extensive preclinical studies are needed. Our aim was to examine if hepatocytes isolated from transgenic "firefly luciferase" Lewis rats into the recipient liver would attenuate the course of thioacetamide (TAA)-induced ALF in Lewis rats. Untreated Lewis rats after TAA administration showed a profound decrease in survival rate; no animal survived 54 h. The rats showed marked increases in plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, in plasma level of bilirubin and ammonia (NH(3)), and in a significant decrease in plasma albumin. Hepatocyte Tx attenuated the course of TAA-induced ALF Lewis rats which was reflected by improved survival rate and reduced degree of liver injury showing as lowering of elevated plasma ALT, AST, NH(3) and bilirubin levels and increasing plasma albumin. In addition, bioluminescence imaging analyses have shown that in the TAA-damaged livers the transplanted hepatocyte were fully viable throughout the experiment. In conclusion, the results show that hepatocyte Tx into the liver can attenuate the course of TAA-induced ALF in Lewis rats. This information should be considered in attempts to develop new therapeutic approaches to the treatment of ALF.

Alginate microencapsulated hepatocytes optimised for transplantation in acute liver failure

Background and Aim

Intraperitoneal transplantation of alginate-microencapsulated human hepatocytes is an attractive option for the management of acute liver failure (ALF) providing short-term support to allow native liver regeneration. The main aim of this study was to establish an optimised protocol for production of alginate-encapsulated human hepatocytes and evaluate their suitability for clinical use.

Methods

Human hepatocyte microbeads (HMBs) were prepared using sterile GMP grade materials. We determined physical stability, cell viability, and hepatocyte metabolic function of HMBs using different polymerisation times and cell densities. The immune activation of peripheral blood mononuclear cells (PBMCs) after co-culture with HMBs was studied. Rats with ALF induced by galactosamine were transplanted intraperitoneally with rat hepatocyte microbeads (RMBs) produced using a similar optimised protocol. Survival rate and biochemical profiles were determined. Retrieved microbeads were evaluated for morphology and functionality.

Results

The optimised HMBs were of uniform size (583.5±3.3 µm) and mechanically stable using 15 min polymerisation time compared to 10 min and 20 min (p<0.001). 3D confocal microscopy images demonstrated that hepatocytes with similar cell viability were evenly distributed within HMBs. Cell density of 3.5×10⁶ cells/ml provided the highest viability. HMBs incubated in human ascitic fluid showed better cell viability and function than controls. There was no significant activation of PBMCs co-cultured with empty or hepatocyte microbeads, compared to PBMCs alone. Intraperitoneal transplantation of RMBs was safe and significantly improved the severity of liver damage compared to control groups (empty microbeads and medium alone; p<0.01). Retrieved RMBs were intact and free of immune cell adherence and contained viable hepatocytes with preserved function.

Conclusion

An optimised protocol to produce GMP grade alginate-encapsulated human hepatocytes has been established. Transplantation of microbeads provided effective metabolic function in ALF. These high quality HMBs should be suitable for use in clinical transplantation.