Use of indocyanine green for functional assessment of human hepatocytes for transplantation

In vitro characterization of 3D culture-based differentiation of human liver stem cells

Introduction: The lack of functional hepatocytes poses a significant challenge for drug safety testing and therapeutic applications due to the inability of mature hepatocytes to expand and their tendency to lose functionality in vitro. Previous studies have demonstrated the potential of Human Liver Stem Cells (HLSCs) to differentiate into hepatocyte-like cells within an in vitro rotary cell culture system, guided by a combination of growth factors and molecules known to regulate hepatocyte maturation. In this study, we employed a matrix multi-assay approach to comprehensively characterize HLSC differentiation. Methods: We evaluated the expression of hepatic markers using qRT-PCR, immunofluorescence, and Western blot analysis. Additionally, we measured urea and FVIII secretion into the supernatant and developed an updated indocyanine green in vitro assay to assess hepatocyte functionality. Results: Molecular analyses of differentiated HLSC aggregates revealed significant upregulation of hepatic genes, including CYP450, urea cycle enzymes, and uptake transporters exclusively expressed on the sinusoidal side of mature hepatocytes, evident as early as 1 day post-differentiation. Interestingly, HLSCs transiently upregulated stem cell markers during differentiation, followed by downregulation after 7 days. Furthermore, differentiated aggregates demonstrated the ability to release urea and FVIII into the supernatant as early as the first 24 h, with accumulation over time. Discussion: These findings suggest that a 3D rotation culture system may facilitate rapid hepatic differentiation of HLSCs. Despite the limitations of this rotary culture system, its unique advantages hold promise for characterizing HLSC GMP batches for clinical applications.

Dye labeling for optical imaging biases drug carriers' biodistribution and tumor uptake

Biodistribution analyses of nanocarriers are often performed with optical imaging. Though dye tags can interact with transporters, e.g., organic anion transporting polypeptides (OATPs), their influence on biodistribution was hardly studied. Therefore, this study compared tumor cell uptake and biodistribution (in A431 tumor-bearing mice) of four near-infrared fluorescent dyes (AF750, IRDye750, Cy7, DY-750) and dye-labeled poly(N-(2-hydroxypropyl)methacrylamide)-based nanocarriers (dye-pHPMAs). Tumor cell uptake of hydrophobic dyes (Cy7, DY-750) was higher than that of hydrophilic dyes (AF750, IRDye750), and was actively mediated but not related to OATPs. Free dyes' elimination depended on their hydrophobicity, and tumor uptake correlated with blood circulation times. Dye-pHPMAs circulated longer and accumulated stronger in tumors than free dyes. Dye labeling significantly influenced nanocarriers' tumor accumulation and biodistribution. Therefore, low-interference dyes and further exploration of dye tags are required to achieve the most unbiased results possible. In our assessment, AF750 and IRDye750 best qualified for labeling hydrophilic nanocarriers.

Lineage reprogramming of human adipose mesenchymal stem cells to immune modulatory i-Heps

Pluripotent stem cell derived-hepatocytes depict fetal -hepatocyte characteristics/maturity and are immunogenic limiting their applications. Attempts have been made to derive hepatocytes from mesenchymal stem cells using developmental cocktails, epigenetic modulators and small molecules. However, achieving a stable terminally differentiated functional state had been a challenge. Inefficient hepatic differentiation could be due to lineage restrictions set during development. Hence a novel lineage reprogramming approach has been utilized to confer competence to adipose-mesenchymal stem cells (ADMSCs) to efficiently respond to hepatogenic cues and achieve a stable functional hepatic state. Lineage reprogramming involved co-transduction of ADMSCs with hepatic endoderm pioneer Transcription factor (TF)-FOXA2, HHEX-a homeobox gene and HNF4α-master TF indispensable for hepatic state maintenance. Lineage priming was evidenced by endogenous HFN4α promoter demethylation and robust responsiveness to minimal hepatic maturation cues. Induced hepatocytes (i-Heps) exhibited mesenchymal-to-epithelial transition and terminal hepatic signatures. Functional characterisation of i-Heps for hepatic drug detoxification systems, xenobiotic uptake/clearance, metabolic status and hepatotropic virus entry validated acquisition of stable hepatic state and junctional maturity Exhaustive analysis of MSC memory in i-Heps indicated loss of MSC-immunophenotype and terminal differentiation to osteogenic/adipogenic lineages. Importantly, i-Heps suppressed phytohemagglutinin-induced T-cell blasts, inhibited allogenic mixed-lymphocyte reactions (MLRs) and secreted immunomodulatory- indoleamine 2,3-dioxygenase in T-cell blast co-cultures akin to native ADMSCs. In a nutshell, the present study identifies a novel cocktail of TFs that reprogram ADMSCs to stable hepatic state. i-Heps exhibit adult hepatocyte functional maturity with robust immune-modulatory abilities rendering suitability for rigorous drug testing, hepatocyte-pathogen interaction studies and transplantation in allogenic settings.

In vitro culture at 39 °C during hepatic maturation of human ES cells facilitates hepatocyte-like cell functions

Hepatocyte-like cells derived from human pluripotent stem cells (hPSC-HLCs) offer an alternative to primary hepatocytes commonly used for drug screenings and toxicological tests. However, these cells do not have hepatic functions comparable to those of hepatocytes in vivo due to insufficient hepatic differentiation. Here we showed that the hepatic functions of hPSC-HLCs were facilitated by applying physiological liver temperatures during hepatic differentiation. We identified the optimal temperature by treating HLCs derived from H9 human embryonic stem cells (hESC-HLCs) at 39 °C; the 42 °C treatment caused significantly greater cell death than the 39 °C treatment. We confirmed the improvement of hepatic functions, such as albumin secretion, cytochrome P450 3A activity, and collagen production, without severe cell damage. In combination with existing hepatic differentiation protocols, the method proposed here may further improve hepatic functions for hPSCs and lead to the realization of drug discovery efforts and drug toxicological tests.

Cell therapy for factor V deficiency: An approach based on human decidua mesenchymal stem cells

Deficiency of factor V is a congenital autosomal recessive coagulopathy associated with mutations in the F5 gene that results in mild-to-severe bleeding episodes. Factor V is a component of the prothrombinase complex responsible for accelerating conversion of prothrombin to thrombin. At the present time there are no therapeutic factor V concentrates available. This study was designed to lay the preliminary foundations for future cell-based therapy for patients with severe factor V deficiency. The study showed that hepatospheres, which produce coagulation factors VIII, IX, and V, synthetize and store intracellular glycogen and express albumin levels up to 8 times higher than those of undifferentiated cells. Factor IX and factor V gene expression increased significantly in hepatospheres as compared to undifferentiated cells, whereas factor VIII gene expression remained constant. The factor V protein was detected in the hepatospheres´ secretome. Considering the enormous potential of mesenchymal stem cells as therapeutic agents, this study proposes a highly reproducible method to induce differentiation of mesenchymal stem cells from human placenta to factor V-producing hepatospheres. This strategy constitutes a preliminary step towards a curative treatment of factor V deficiency through advanced therapies such as cell therapy.

Preclinical Application of Reduced Manipulated Processing Strategy to Collect Transplantable Hepatocytes: A Pilot and Feasibility Study

Background: The complex isolation and purification process of hepatocytes for transplantation is labor intensive and with great contamination risk. Here, as a pilot and feasibility study, we examined in vitro and in vivo hepatocyte isolation feasibility and cell function of Cell Saver^® Elite^®, an intraoperative blood-cell-recovery system. Methods: Rat and pig liver cells were collected using this system and then cultured in vitro, and their hepatocyte-specific enzymes were characterized. We then transplanted the hepatocytes in an established acute liver–injured (retrorsine+D-galactosamine-treated) rat model for engraftment. Recipient rats were sacrificed 1, 2, and 4 weeks after transplantation, followed by donor-cell identification and histological, serologic, and immunohistopathological examination. To demonstrate this Cell Saver^® strategy is workable in the first place, traditional (classical) strategy, in our study, behaved as certainty during the cell manufacturing process for monitoring quality assurance throughout the course, from the start of cell isolation to post-transplantation. Results: We noted that in situ collagenase perfusion was followed by filtration, centrifugation, and collection in the Cell Saver^® until the process ended. Most (>85%) isolated cells were hepatocytes (>80% viability) freshly demonstrating hepatocyte nuclear factor 4α and carbamoyl-phosphate synthase 1 (a key enzyme in the urea cycle), and proliferating through intercellular contact in culture, with expression of albumin and CYP3A4. After hepatocyte transplantation in dipeptidyl peptidase IV (−/−) rat liver, wild-type donor hepatocytes engrafted and repopulated progressively in 4 weeks with liver functional improvement. Proliferating donor hepatocyte–native biliary ductular cell interaction was identified. Post-transplantation global liver functional recovery after Cell Saver and traditional methods was comparable. Conclusions: Cell Saver^® requires reduced manual manipulation for isolating transplantable hepatocytes.

Evaluation of liver function using liver parenchyma, spleen and portal vein signal intensities during the hepatobiliary phase in Gd-EOB-D TPA-enhanced MRI

Background

Previous studies have used signal intensity (SI) to reflect liver function. However, few studies have evaluated liver function via the portal vein. Regarding the SI of the liver, spleen, and portal vein, no study has indicated which can best reflect liver function. Therefore, the aim of this study is to investigate whether these parameters can evaluate liver function in patients with cirrhosis and determine which is the best parameter.

Methods

120 patients with normal livers (n = 41) or Child–Pugh class A (n = 50), B (n = 21) or C (n = 8) disease who had undergone Gd-EOB-DTPA-enhanced MRI were retrospectively reviewed. Comparisons of the MRI data (liver parenchyma SI, portal vein SI, and spleen SI and liver-to-portal vein contrast ratio (LPC), liver-to-spleen contrast ratio (LSC), and portal vein-to-spleen contrast ratio (PSC)) in the 15-min hepatobiliary phase images were performed among the groups, and the correlations among the liver function parameters (total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, albumin, creatinine, platelet count, prothrombin time and international normalized ratio), liver function scores and MRI data were also quantitatively analysed.

Results

Significant differences were observed in the liver parenchyma SI, LPC and LSC among the groups. These values all decreased gradually from normal livers to Child–Pugh class C cirrhotic livers (P < 0.001). The portal vein SI constantly and slightly increased from normal livers to Child–Pugh class C cirrhotic livers, but no differences were found among the groups in the portal vein SI and PSC (P > 0.05). LPC showed a stronger correlation with the Child–Pugh score and MELD score than LSC and the liver parenchyma SI. The order of the AUCs of these parameters, from largest to smallest, was as follows: LPC, LSC, and liver parenchyma SI (P > 0.05).

Conclusion

The liver parenchyma SI, LSC and LPC may be used as alternative imaging biomarkers to assess liver function, while the portal vein SI and PSC do not reflect liver function. Furthermore, LPC values can more effectively distinguish severity among patients with cirrhosis than the liver parenchyma SI and LSC.

Optical and Optoacoustic Imaging Probes

Tissue has characteristic properties when it comes to light absorption and scattering. For optical (OI) and optoacoustic imaging (OAI) these properties can be utilised to visualise biological tissue characteristics, as, for example, the oxygenation state of haemoglobin alters the optical and optoacoustic properties of the molecule.

Generation of expandable human pluripotent stem cell-derived hepatocyte-like liver organoids

BACKGROUND & AIMS

The development of hepatic models capable of long-term expansion with competent liver functionality is technically challenging in a personalized setting. Stem cell-based organoid technologies can provide an alternative source of patient-derived primary hepatocytes. However, self-renewing and functionally competent human pluripotent stem cell (PSC)-derived hepatic organoids have not been developed.

METHODS

We developed a novel method to efficiently and reproducibly generate functionally mature human hepatic organoids derived from PSCs, including human embryonic stem cells and induced PSCs. The maturity of the organoids was validated by a detailed transcriptome analysis and functional performance assays. The organoids were applied to screening platforms for the prediction of toxicity and the evaluation of drugs that target hepatic steatosis through real-time monitoring of cellular bioenergetics and high-content analyses.

RESULTS

Our organoids were morphologically indistinguishable from adult liver tissue-derived epithelial organoids and exhibited self-renewal. With further maturation, their molecular features approximated those of liver tissue, although these features were lacking in 2D differentiated hepatocytes. Our organoids preserved mature liver properties, including serum protein production, drug metabolism and detoxifying functions, active mitochondrial bioenergetics, and regenerative and inflammatory responses. The organoids exhibited significant toxic responses to clinically relevant concentrations of drugs that had been withdrawn from the market due to hepatotoxicity and recapitulated human disease phenotypes such as hepatic steatosis.

CONCLUSIONS

Our organoids exhibit self-renewal (expandable and further able to differentiate) while maintaining their mature hepatic characteristics over long-term culture. These organoids may provide a versatile and valuable platform for physiologically and pathologically relevant hepatic models in the context of personalized medicine.

LAY SUMMARY

A functionally mature, human cell-based liver model exhibiting human responses in toxicity prediction and drug evaluation is urgently needed for pre-clinical drug development. Here, we develop a novel human pluripotent stem cell-derived hepatocyte-like liver organoid that is critically advanced in terms of its generation method, functional performance, and application technologies. Our organoids can contribute to the better understanding of liver development and regeneration, and provide insights for metabolic studies and disease modeling, as well as toxicity assessments and drug screening for personalized medicine.

Biodistribution and toxicological evaluation of micron- and nano-sized erythrocyte-derived optical particles in healthy Swiss Webster mice

Particle-based systems provide a capability for the delivery of imaging and/or therapeutic payloads. We have engineered constructs derived from erythrocytes, and doped with the FDA-approved near infrared dye, indocyanine green (ICG). We refer to these optical particles as NIR erythrocyte-mimicking transducers (NETs). A particular feature of NETs is that their diameters can be tuned from micron- to nano-scale. Herein, we investigated the effects of micron- (≈2.6 μm diameter), and nano- (≈145 nm diameter) sized NETs on their biodistribution, and evaluated their acute toxicity in healthy Swiss Webster mice. Following tail vein injection of free ICG and NETs, animals were euthanized at various time points up to 48 hours. Fluorescence analysis of blood showed that nearly 11% of the injected amount of nano-sized NETs (nNETs) remained in blood at 48 hours post-injection as compared to ≈5% for micron-sized NETs (μNETs). Similarly, at this time point, higher levels of nNETs were present in various organs including the lungs, liver, and spleen. Histological analyses of various organs, extracted at 24 hours post-injection of NETs, did not show pathological alterations. Serum biochemistry profiles, in general, did not show elevated levels of the various analyzed biomarkers associated with liver and kidney functions. Values of various hematological profiles remained within the normal ranges following the administration of μNETs and nNETs. Results of this study suggest that erythrocyte-derived particles can potentially provide a non-toxic platform for delivery of ICG.

Biomimetic 3D-printed neurovascular phantoms for near-infrared fluorescence imaging

Emerging three-dimensional (3D) printing technology enables the fabrication of optically realistic and morphologically complex tissue-simulating phantoms for the development and evaluation of novel optical imaging products. In this study, we assess the potential to print image-defined neurovascular phantoms with patent channels for contrast-enhanced near-infrared fluorescence (NIRF) imaging. An anatomical map defined from clinical magnetic resonance imaging (MRI) was segmented and processed into files suitable for printing a forebrain vessel network in rectangular and curved-surface biomimetic phantoms. Methods for effectively cleaning samples with complex vasculature were determined. A final set of phantoms were imaged with a custom NIRF system at 785 nm excitation using two NIRF contrast agents. In addition to demonstrating the strong potential of 3D printing for creating highly realistic, patient-specific biophotonic phantoms, our work provides insight into optimal methods for accomplishing this goal and elucidates current limitations of this approach.

CRISPR Correction of a Homozygous Low-Density Lipoprotein Receptor Mutation in Familial Hypercholesterolemia Induced Pluripotent Stem Cells

Familial hypercholesterolemia (FH) is a hereditary disease primarily due to mutations in the low‐density lipoprotein receptor (LDLR) that lead to elevated cholesterol and premature development of cardiovascular disease. Homozygous FH patients (HoFH) with two dysfunctional LDLR alleles are not as successfully treated with standard hypercholesterol therapies, and more aggressive therapeutic approaches to control cholesterol levels must be considered. Liver transplant can resolve HoFH, and hepatocyte transplantation has shown promising results in animals and humans. However, demand for donated livers and high‐quality hepatocytes overwhelm the supply. Human pluripotent stem cells can differentiate to hepatocyte‐like cells (HLCs) with the potential for experimental and clinical use. To be of future clinical use as autologous cells, LDLR genetic mutations in derived FH‐HLCs need to be corrected. Genome editing technology clustered‐regularly‐interspaced‐short‐palindromic‐repeats/CRISPR‐associated 9 (CRISPR/Cas9) can repair pathologic genetic mutations in human induced pluripotent stem cells. Conclusion: We used CRISPR/Cas9 genome editing to permanently correct a 3‐base pair homozygous deletion in LDLR exon 4 of patient‐derived HoFH induced pluripotent stem cells. The genetic correction restored LDLR‐mediated endocytosis in FH‐HLCs and demonstrates the proof‐of‐principle that CRISPR‐mediated genetic modification can be successfully used to normalize HoFH cholesterol metabolism deficiency at the cellular level. (Hepatology Communications 2017;1:886–898)

Noninvasive Assessment of Elimination and Retention using CT-FMT and Kinetic Whole-body Modeling

Fluorescence-mediated tomography (FMT) is a quantitative three-dimensional imaging technique for preclinical research applications. The combination with micro-computed tomography (µCT) enables improved reconstruction and analysis. The aim of this study is to assess the potential of µCT-FMT and kinetic modeling to determine elimination and retention of typical model drugs and drug delivery systems.

We selected four fluorescent probes with different but well-known biodistribution and elimination routes: Indocyanine green (ICG), hydroxyapatite-binding OsteoSense (OS), biodegradable nanogels (NG) and microbubbles (MB). µCT-FMT scans were performed in twenty BALB/c nude mice (5 per group) at 0.25, 2, 4, 8, 24, 48 and 72 h after intravenous injection. Longitudinal organ curves were determined using interactive organ segmentation software and a pharmacokinetic whole-body model was implemented and applied to compute physiological parameters describing elimination and retention.

ICG demonstrated high initial hepatic uptake which decreased rapidly while intestinal accumulation appeared for around 8 hours which is in line with the known direct uptake by hepatocytes followed by hepatobiliary elimination. Complete clearance from the body was observed at 48 h. NG showed similar but slower hepatobiliary elimination because these nanoparticles require degradation before elimination can take place. OS was strongly located in the bones in addition to high signal in the bladder at 0.25 h indicating fast renal excretion. MB showed longest retention in liver and spleen and low signal in the kidneys likely caused by renal elimination or retention of fragments. Furthermore, probe retention was found in liver (MB, NG and OS), spleen (MB) and kidneys (MB and NG) at 72 h which was confirmed by ex vivo data. The kinetic model enabled robust extraction of physiological parameters from the organ curves.

In summary, µCT-FMT and kinetic modeling enable differentiation of hepatobiliary and renal elimination routes and allow for the noninvasive assessment of retention sites in relevant organs including liver, kidney, bone and spleen.