Generation of Human Fatty Livers Using Custom-Engineered Induced Pluripotent Stem Cells with Modifiable SIRT1 Metabolism

Comparison of Wild-Type and High-risk PNPLA3 variants in a Human Biomimetic Liver Microphysiology System for Metabolic Dysfunction-associated Steatotic Liver Disease Precision Therapy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a worldwide health epidemic with a global occurrence of approximately 30%. The pathogenesis of MASLD is a complex, multisystem disorder driven by multiple factors including genetics, lifestyle, and the environment. Patient heterogeneity presents challenges for developing MASLD therapeutics, creation of patient cohorts for clinical trials and optimization of therapeutic strategies for specific patient cohorts. Implementing pre-clinical experimental models for drug development creates a significant challenge as simple in vitro systems and animal models do not fully recapitulate critical steps in the pathogenesis and the complexity of MASLD progression. To address this, we implemented a precision medicine strategy that couples the use of our liver acinus microphysiology system (LAMPS) constructed with patient-derived primary cells. We investigated the MASLD-associated genetic variant PNPLA3 rs738409 (I148M variant) in primary hepatocytes, as it is associated with MASLD progression. We constructed LAMPS with genotyped wild type and variant PNPLA3 hepatocytes together with key non-parenchymal cells and quantified the reproducibility of the model. We altered media components to mimic blood chemistries, including insulin, glucose, free fatty acids, and immune activating molecules to reflect normal fasting (NF), early metabolic syndrome (EMS) and late metabolic syndrome (LMS) conditions. Finally, we investigated the response to treatment with resmetirom, an approved drug for metabolic syndrome-associated steatohepatitis (MASH), the progressive form of MASLD. This study using primary cells serves as a benchmark for studies using patient biomimetic twins constructed with patient iPSC-derived liver cells using a panel of reproducible metrics. We observed increased steatosis, immune activation, stellate cell activation and secretion of pro-fibrotic markers in the PNPLA3 GG variant compared to wild type CC LAMPS, consistent with the clinical characterization of this variant. We also observed greater resmetirom efficacy in PNPLA3 wild type CC LAMPS compared to the GG variant in multiple MASLD metrics including steatosis, stellate cell activation and the secretion of pro-fibrotic markers. In conclusion, our study demonstrates the capability of the LAMPS platform for the development of MASLD precision therapeutics, enrichment of patient cohorts for clinical trials, and optimization of therapeutic strategies for patient subgroups with different clinical traits and disease stages.

SIRT1: Harnessing multiple pathways to hinder NAFLD

Non-alcoholic fatty liver disease (NAFLD) encompasses hepatic steatosis, non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. It is the primary cause of chronic liver disorders, with a high prevalence but no approved treatment. Therefore, it is indispensable to find a trustworthy therapy for NAFLD. Recently, mounting evidence illustrates that Sirtuin 1 (SIRT1) is strongly associated with NAFLD. SIRT1 activation or overexpression attenuate NAFLD, while SIRT1 deficiency aggravates NAFLD. Besides, an array of therapeutic agents, including natural compounds, synthetic compounds, traditional Chinese medicine formula, and stem cell transplantation, alleviates NALFD via SIRT1 activation or upregulation. Mechanically, SIRT1 alleviates NAFLD by reestablishing autophagy, enhancing mitochondrial function, suppressing oxidative stress, and coordinating lipid metabolism, as well as reducing hepatocyte apoptosis and inflammation. In this review, we introduced the structure and function of SIRT1 briefly, and summarized the effect of SIRT1 on NAFLD and its mechanism, along with the application of SIRT1 agonists in treating NAFLD.

Organoid-guided precision hepatology for metabolic liver disease

Metabolic dysfunction-associated steatotic liver disease affects millions of people worldwide. Progress towards a definitive cure has been incremental and treatment is currently limited to lifestyle modification. Hepatocyte-specific lipid accumulation is the main trigger of lipotoxic events, driving inflammation and fibrosis. The underlying pathology is extraordinarily heterogenous, and the manifestations of steatohepatitis are markedly influenced by metabolic communications across non-hepatic organs. Synthetic human tissue models have emerged as powerful platforms to better capture the mechanistic diversity in disease progression, while preserving person-specific genetic traits. In this review, we will outline current research efforts focused on integrating multiple synthetic tissue models of key metabolic organs, with an emphasis on organoid-based systems. By combining functional genomics and population-scale en masse profiling methodologies, human tissues derived from patients can provide insights into personalised genetic, transcriptional, biochemical, and metabolic states. These collective efforts will advance our understanding of steatohepatitis and guide the development of rational solutions for mechanism-directed diagnostic and therapeutic investigation.

Regenerative human liver organoids (HLOs) in a pillar/perfusion plate for hepatotoxicity assays

Human liver organoids (HLOs) differentiated from embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and adult stem cells (ASCs) can recapitulate structure and function of human fetal liver tissues, thus, considered as a promising tissue model for liver diseases and predictive compound screening. Nonetheless, there are still several technical challenges to adopt HLOs in the drug discovery process, which include relatively long-term cell differentiation with multiple culture media (3 - 4 weeks) leading to batch-to-batch variation, short-term hepatic function after maturation (3 - 5 days), low assay throughput due to Matrigel dissociation and HLO transfer to a microtiter well plate, and insufficient maturity as compared to primary hepatocytes. To address these issues, expandable HLOs (Exp-HLOs) derived from human iPSCs were generated by optimizing differentiation protocols, which were rapidly printed on a 144-pillar plate with sidewalls and slits (144PillarPlate) and dynamically cultured for up to 20 days into differentiated HLOs (Diff-HLOs) in a 144-perfusion plate with perfusion wells and reservoirs (144PerfusionPlate) for in situ organoid culture and analysis. Dynamically cultured Diff-HLOs were generated robustly and reproducibly in the pillar/perfusion plate with higher maturity as compared to those in statically cultured HLOs by differentiating Exp-HLOs for 10 days. In addition, Diff-HLOs in the pillar/perfusion plate were tested with acetaminophen and troglitazone for 3 days to assess drug-induced liver injury (DILI) and then incubated in an expansion medium for 10 days to evaluate the recovery of the liver from DILI. The assessment of liver regeneration post injury is critical to understand the mechanism of recovery and determine the threshold drug concentration beyond which there will be a sharp decrease in the liver's regenerative capacity. We envision that bioprinted Diff-HLOs in the pillar/perfusion plate could be used for high-throughput screening (HTS) of hepatotoxic compounds due to short-term differentiation of passage-able Exp-HLOs necessary, stable hepatic function after maturation, high reproducibility, and high throughput with capability of in situ organoid culture, testing, staining, imaging, and analysis.

Microphysiological systems for human aging research

Recent advances in microphysiological systems (MPS), also known as organs-on-a-chip (OoC), enable the recapitulation of more complex organ and tissue functions on a smaller scale in vitro. MPS therefore provide the potential to better understand human diseases and physiology. To date, numerous MPS platforms have been developed for various tissues and organs, including the heart, liver, kidney, blood vessels, muscle, and adipose tissue. However, only a few studies have explored using MPS platforms to unravel the effects of aging on human physiology and the pathogenesis of age-related diseases. Age is one of the risk factors for many diseases, and enormous interest has been devoted to aging research. As such, a human MPS aging model could provide a more predictive tool to understand the molecular and cellular mechanisms underlying human aging and age-related diseases. These models can also be used to evaluate preclinical drugs for age-related diseases and translate them into clinical settings. Here, we provide a review on the application of MPS in aging research. First, we offer an overview of the molecular, cellular, and physiological changes with age in several tissues or organs. Next, we discuss previous aging models and the current state of MPS for studying human aging and age-related conditions. Lastly, we address the limitations of current MPS and present future directions on the potential of MPS platforms for human aging research.

Human Induced Pluripotent Stem Cell based Hepatic-Modeling of Lipid metabolism associated TM6SF2 E167K variant

BACKGROUND AND AIMS

TM6SF2 rs58542926 (E167K) is associated with an increase in the prevalence of Metabolic Disfunction-Associated Steatotic Liver Disease (MASLD). Despite all the investigation related to the role of this variant in lipid metabolism, conflicting results in mouse studies underscore the importance of creating a human model for understanding the TM6SF2 mechanism. Therefore, the aim of this study is to generate a reliable human in vitro model that mimic the effects of the TM6SF2 E167K mutation and can be used for future mechanism studies.

APPROACH AND RESULTS

We performed gene editing on human-induced pluripotent stem cells (iPSC) derived from a healthy individual to obtain the cells carrying the TM6SF2 E167K mutation. After hepatic differentiation, a decrease in TM6SF2 protein expression was observed in the mutated-induced hepatocyte. An increase in intracellular lipid droplets and a decrease in the efflux of cholesterol and ApoB100 were also observed. Transcriptomics analysis showed up-regulation of genes related to the transport, flux, and oxidation of lipids, fatty acids, and cholesterol in TM6SF2 E167K cells. Additionally, signs of cellular stress were observed in the ER and mitochondria.

CONCLUSIONS

Our findings indicate that induced hepatocytes generated from iPSC carrying the TM6SF2 E167K recapitulate the effects observed in human hepatocytes from individuals with the TM6SF2 mutation. This study characterizes an in vitro model that can be used as a platform to help in the identification of potential clinical targets and therapies and to understand the mechanism by which the TM6SF2 E167K variant leads to vulnerability to MASLD.

Exploring the promising potential of induced pluripotent stem cells in cancer research and therapy

The advent of iPSCs has brought about a significant transformation in stem cell research, opening up promising avenues for advancing cancer treatment. The formation of cancer is a multifaceted process influenced by genetic, epigenetic, and environmental factors. iPSCs offer a distinctive platform for investigating the origin of cancer, paving the way for novel approaches to cancer treatment, drug testing, and tailored medical interventions. This review article will provide an overview of the science behind iPSCs, the current limitations and challenges in iPSC-based cancer therapy, the ethical and social implications, and the comparative analysis with other stem cell types for cancer treatment. The article will also discuss the applications of iPSCs in tumorigenesis, the future of iPSCs in tumorigenesis research, and highlight successful case studies utilizing iPSCs in tumorigenesis research. The conclusion will summarize the advancements made in iPSC-based tumorigenesis research and the importance of continued investment in iPSC research to unlock the full potential of these cells.

Engineered human hepatocyte organoids enable CRISPR-based target discovery and drug screening for steatosis

The lack of registered drugs for nonalcoholic fatty liver disease (NAFLD) is partly due to the paucity of human-relevant models for target discovery and compound screening. Here we use human fetal hepatocyte organoids to model the first stage of NAFLD, steatosis, representing three different triggers: free fatty acid loading, interindividual genetic variability (PNPLA3 I148M) and monogenic lipid disorders (APOB and MTTP mutations). Screening of drug candidates revealed compounds effective at resolving steatosis. Mechanistic evaluation of effective drugs uncovered repression of de novo lipogenesis as the convergent molecular pathway. We present FatTracer, a CRISPR screening platform to identify steatosis modulators and putative targets using APOB-/- and MTTP-/- organoids. From a screen targeting 35 genes implicated in lipid metabolism and/or NAFLD risk, FADS2 (fatty acid desaturase 2) emerged as an important determinant of hepatic steatosis. Enhancement of FADS2 expression increases polyunsaturated fatty acid abundancy which, in turn, reduces de novo lipogenesis. These organoid models facilitate study of steatosis etiology and drug targets.

Polymorphisms Associated With Metabolic Dysfunction-Associated Steatotic Liver Disease Influence the Progression of End-Stage Liver Disease

BACKGROUND AND AIMS

Chronic liver injury that results in cirrhosis and end-stage liver disease (ESLD) causes more than 1 million deaths annually worldwide. Although the impact of genetic factors on the severity of metabolic dysfunction-associated steatotic liver disease (MASLD) and alcohol-related liver disease (ALD) has been previously studied, their contribution to the development of ESLD remains largely unexplored.

METHODS

We genotyped 6 MASLD-associated polymorphisms in healthy (n = 123), metabolic dysfunction-associated steatohepatitis (MASH) (n = 145), MASLD-associated ESLD (n = 72), and ALD-associated ESLD (n = 57) cohorts and performed multinomial logistic regression to determine the combined contribution of genetic, demographic, and clinical factors to the progression of ESLD.

RESULTS

Distinct sets of factors are associated with the progression to ESLD. The PNPLA3 rs738409:G and TM6SF2 rs58542926:T alleles, body mass index (BMI), age, and female sex were positively associated with progression from a healthy state to MASH. The PNPLA3 rs738409:G allele, age, male sex, and having type 2 diabetes mellitus were positively associated, while BMI was negatively associated with progression from MASH to MASLD-associated ESLD. The PNPLA3 rs738409:G and GCKR rs780094:T alleles, age, and male sex were positively associated, while BMI was negatively associated with progression from a healthy state to ALD-associated ESLD. The findings indicate that the PNPLA3 rs738409:G allele increases susceptibility to ESLD regardless of etiology, the TM6SF2 rs58542926:T allele increases susceptibility to MASH, and the GCKR rs780094:T allele increases susceptibility to ALD-associated ESLD.

CONCLUSION

The PNPLA3, TM6SF2, and GCKR minor alleles influence the progression of MASLD-associated or ALD-associated ESLD. Genotyping for these variants in MASLD and ALD patients can enhance risk assessment, prompting early interventions to prevent ESLD.

Liver and Muscle Transcriptomes Differ in Mid-Lactation Cows Divergent in Feed Efficiency in the Presence or Absence of Supplemental Rumen-Protected Choline

Improving dairy cow feed efficiency is critical to the sustainability and profitability of dairy production, yet the underlying mechanisms that contribute to individual cow variation in feed efficiency are not fully understood. The objectives of this study were to (1) identify genes and associated pathways that are altered in cows with high- or low-residual feed intake (RFI) using RNA sequencing, and (2) determine if rumen-protected choline supplementation during mid-lactation would influence performance or feed efficiency. Mid-lactation (134 ± 20 days in milk) multiparous Holstein cows were randomly assigned to either supplementation of 0 g/d supplementation (CTL; n = 32) or 30 g/d of a rumen-protected choline product (RPC; 13.2 g choline ion; n = 32; Balchem Corp., New Hampton, NY, USA). Residual feed intake was determined as dry matter intake regressed on milk energy output, days in milk, body weight change, metabolic body weight, and dietary treatment. The 12 cows with the highest RFI (low feed efficient; LE) and 12 cows with the lowest RFI (high feed efficient; HE), balanced by dietary treatment, were selected for blood, liver, and muscle analysis. No differences in production or feed efficiency were detected with RPC supplementation, although albumin was greater and arachidonic acid tended to be greater in RPC cows. Concentrations of β-hydroxybutyrate were greater in HE cows. Between HE and LE, 268 and 315 differentially expressed genes in liver and muscle tissue, respectively, were identified through RNA sequencing. Pathway analysis indicated differences in cell cycling, oxidative stress, and immunity in liver and differences in glucose and fatty acid pathways in muscle. The current work indicates that unique differences in liver and muscle post-absorptive nutrient metabolism contribute to sources of variation in feed efficiency and that differences in amino acid and fatty acid oxidation, cell cycling, and immune function should be further examined.

Development of brain organoid technology derived from iPSC for the neurodegenerative disease modelling: a glance through

Neurodegenerative diseases are adult-onset neurological conditions that are notoriously difficult to model for drug discovery and development because most models are unable to accurately recapitulate pathology in disease-relevant cells, making it extremely difficult to explore the potential mechanisms underlying neurodegenerative diseases. Therefore, alternative models of human or animal cells have been developed to bridge the gap and allow the impact of new therapeutic strategies to be anticipated more accurately by trying to mimic neuronal and glial cell interactions and many more mechanisms. In tandem with the emergence of human-induced pluripotent stem cells which were first generated in 2007, the accessibility to human-induced pluripotent stem cells (hiPSC) derived from patients can be differentiated into disease-relevant neurons, providing an unrivaled platform for in vitro modeling, drug testing, and therapeutic strategy development. The recent development of three-dimensional (3D) brain organoids derived from iPSCs as the best alternative models for the study of the pathological features of neurodegenerative diseases. This review highlights the overview of current iPSC-based disease modeling and recent advances in the development of iPSC models that incorporate neurodegenerative diseases. In addition, a summary of the existing brain organoid-based disease modeling of Alzheimer's disease was presented. We have also discussed the current methodologies of regional specific brain organoids modeled, its potential applications, emphasizing brain organoids as a promising platform for the modeling of patient-specific diseases, the development of personalized therapies, and contributing to the design of ongoing or future clinical trials on organoid technologies.

NAFLD and AATD Are Two Diseases with Unbalanced Lipid Metabolism: Similarities and Differences

Non-alcoholic fatty liver disease (NAFLD) is a type of steatosis commonly associated with obesity, dyslipidemia, hypertension, and diabetes. Other diseases such as inherited alpha-1 antitrypsin deficiency (AATD) have also been related to the development of liver steatosis. The primary reasons leading to hepatic lipid deposits can be genetic and epigenetic, and the outcomes range from benign steatosis to liver failure, as well as to extrahepatic diseases. Progressive hepatocellular damage and dysregulated systemic immune responses can affect extrahepatic organs, specifically the heart and lungs. In this review, we discuss the similarities and differences between the molecular pathways of NAFLD and AATD, and the putative value of hepatic organoids as novel models to investigate the physio pathological mechanisms of liver steatosis.

Modeling and therapeutic targeting of inflammation-induced hepatic insulin resistance using human iPSC-derived hepatocytes and macrophages

Hepatic insulin resistance is recognized as a driver of type 2 diabetes and fatty liver disease but specific therapies are lacking. Here we explore the potential of human induced pluripotent stem cells (iPSCs) for modeling hepatic insulin resistance in vitro, with a focus on resolving the controversy about the impact of inflammation in the absence of steatosis. For this, we establish the complex insulin signaling cascade and the multiple inter-dependent functions constituting hepatic glucose metabolism in iPSC-derived hepatocytes (iPSC-Heps). Co-culture of these insulin-sensitive iPSC-Heps with isogenic iPSC-derived pro-inflammatory macrophages induces glucose output by preventing insulin from inhibiting gluconeogenesis and glycogenolysis and activating glycolysis. Screening identifies TNFα and IL1β as the mediators of insulin resistance in iPSC-Heps. Neutralizing these cytokines together restores insulin sensitivity in iPSC-Heps more effectively than individual inhibition, reflecting specific effects on insulin signaling and glucose metabolism mediated by NF-κB or JNK. These results show that inflammation is sufficient to induce hepatic insulin resistance and establish a human iPSC-based in vitro model to mechanistically dissect and therapeutically target this metabolic disease driver.

The Values and Perspectives of Organoids in the Field of Metabolic Syndrome

Metabolic syndrome (MetS) has become a global health problem, and the prevalence of obesity at all stages of life makes MetS research increasingly important and urgent. However, as a comprehensive and complex disease, MetS has lacked more appropriate research models. The advent of organoids provides an opportunity to address this issue. However, it should be noted that organoids are still in their infancy. The main drawbacks are a lack of maturity, complexity, and the inability to standardize large-scale production. Could organoids therefore be a better choice for studying MetS than other models? How can these limitations be overcome? Here, we summarize the available data to present current progress on pancreatic and hepatobiliary organoids and to answer these open questions. Organoids are of human origin and contain a variety of human cell types necessary to mimic the disease characteristics of MetS in their development. Taken together with the discovery of hepatobiliary progenitors in situ, the dedifferentiation of beta cells in diabetes, and studies on hepatic macrophages, we suggest that promoting endogenous regeneration has the potential to prevent the development of end-stage liver and pancreatic lesions caused by MetS and outline the direction of future research in this field.

Gene and cell therapy approaches for familial hypercholesterolemia: An update

Familial hypercholesterolemia (FH) is a common autosomal codominant hereditary illness marked by the heightened risk of early atherosclerotic cardiovascular disease and high blood levels of low-density lipoprotein cholesterol (LDL-C). FH patients can have homozygous or heterozygous variants. This condition has been linked to variations in the genes for the LDL receptor (LDLR), apolipoprotein B, proprotein convertase subtilisin/Kexin 9 (PCSK9), and LDLR adaptor protein 1. Drugs such as statins, ezetimibe, and PCSK9 inhibitors are currently widely available, allowing for the theoretical normalization of plasma LDL-C levels mostly in patients with heterozygous FH. However, homozygous FH patients usually have a poor response to traditional lipid-lowering therapy and may have a poor prognosis at a young age. LDL apheresis and novel pharmacological therapies such as microsomal transfer protein inhibitors or anti-angiopoietin-like protein 3 monoclonal antibodies are extremely expensive and unavailable in most regions of the world. Therefore, the unmet need persists for these patients. In this review, we discuss the numerous gene delivery, gene editing, and stem cell manipulation techniques used in this study to correct FH-causing LDLR gene variations in vitro, ex vivo, and in vivo. Finally, we looked at a variety of studies that corrected genetic defects that caused FH using the ground-breaking clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing technology.

The native liver as inspiration to create superior in vitro hepatic models

Drug induced liver injury (DILI) is one of the major reasons of drug withdrawal during the different phases of drug development. The later in the drug development a drug is discovered to be toxic, the higher the economical as well as the ethical impact will be. In vitro models for early detection of drug liver toxicity are under constant development, however to date a superior model of the liver is still lacking. Ideally, a highly reliable model should be established to maintain the different hepatic cell functionalities to the greatest extent possible, during a period of time long enough to allow for tracking of the toxicity of compounds. In the case of DILI, toxicity can appear even after months of exposure. To reach this goal, an in vitro model should be developed that mimics the in vivo liver environment, function and response to external stimuli. The different approaches for the development of liver models currently used in the field of tissue engineering will be described in this review. Combining different technologies, leading to optimal materials, cells and 3D-constructs will ultimately lead to an ideal superior model that fully recapitulates the liver.

Engineered Platforms for Maturing Pluripotent Stem Cell-Derived Liver Cells for Disease Modeling

Several liver diseases (eg, hepatitis B/C viruses, alcoholic/nonalcoholic fatty liver, malaria, monogenic diseases, and drug-induced liver injury) significantly impact global mortality and morbidity. Species-specific differences in liver functions limit the use of animals to fully elucidate/predict human outcomes; therefore, in vitro human liver models are used for basic and translational research to complement animal studies. However, primary human liver cells are in short supply and display donor-to-donor variability in viability/quality. In contrast, human hepatocyte-like cells (HLCs) differentiated from induced pluripotent stem cells and embryonic stem cells are a near infinite cell resource that retains the patient/donor's genetic background; however, conventional protocols yield immature phenotypes. HLC maturation can be significantly improved using advanced techniques, such as protein micropatterning to precisely control cell-cell interactions, controlled sized spheroids, organoids with multiple cell types and layers, 3-dimensional bioprinting to spatially control cell populations, microfluidic devices for automated nutrient exchange and to induce liver zonation via soluble factor gradients, and synthetic biology to genetically modify the HLCs to accelerate and enhance maturation. Here, we present design features and characterization for representative advanced HLC maturation platforms and then discuss HLC use for modeling various liver diseases. Lastly, we discuss desirable advances to move this field forward. We anticipate that with continued advances in this space, pluripotent stem cell-derived liver models will provide human-relevant data much earlier in preclinical drug development and reduce animal usage, help elucidate liver disease mechanisms for the discovery of efficacious and safe therapeutics, and be useful as cell-based therapies for patients suffering from end-stage liver failure.

Emerging role of aging in the progression of NAFLD to HCC

With the aging of global population, the incidence of nonalcoholic fatty liver disease (NAFLD) has surged in recent decades. NAFLD is a multifactorial disease that follows a progressive course, ranging from simple fatty liver, nonalcoholic steatohepatitis (NASH) to liver cirrhosis and hepatocellular carcinoma (HCC). It is well established that aging induces pathological changes in liver and potentiates the occurrence and progression of NAFLD, HCC and other age-related liver diseases. Studies of senescent cells also indicate a pivotal engagement in the development of NAFLD via diverse mechanisms. Moreover, nicotinamide adenine dinucleotide (NAD⁺), silence information regulator protein family (sirtuins), and mechanistic target of rapamycin (mTOR) are three vital and broadly studied targets involved in aging process and NAFLD. Nevertheless, the crucial role of these aging-associated factors in aging-related NAFLD remains underestimated. Here, we reviewed the current research on the roles of aging, cellular senescence and three aging-related factors in the evolution of NAFLD to HCC, aiming at inspiring promising therapeutic targets for aging-related NAFLD and its progression.

IL-6/STAT3 axis dictates the PNPLA3-mediated susceptibility to non-alcoholic fatty liver disease

BACKGROUND & AIMS

A number of genetic polymorphisms have been associated with susceptibility to or protection against non-alcoholic fatty liver disease (NAFLD), but the underlying mechanisms remain unknown. Here, we focused on the rs738409 C>G single nucleotide polymorphism (SNP), which produces the I148M variant of patatin-like phospholipase domain-containing protein 3 (PNPLA3) and is strongly associated with NAFLD.

METHODS

To enable mechanistic dissection, we developed a human pluripotent stem cell (hPSC)-derived multicellular liver culture by incorporating hPSC-derived hepatocytes, hepatic stellate cells, and macrophages. We first applied this liver culture to model NAFLD by utilising a lipotoxic milieu reflecting the circulating levels of disease risk factors in affected individuals. We then created an isogenic pair of liver cultures differing only at rs738049 and compared NAFLD phenotype development.

RESULTS

Our hPSC-derived liver culture recapitulated many key characteristics of NAFLD development and progression including lipid accumulation and oxidative stress, inflammatory response, and stellate cell activation. Under the lipotoxic conditions, the I148M variant caused the enhanced development of NAFLD phenotypes. These differences were associated with elevated IL-6/signal transducer and activator of transcription 3 (STAT3) activity in liver cultures, consistent with transcriptomic data of liver biopsies from individuals carrying the rs738409 SNP. Dampening IL-6/STAT3 activity alleviated the I148M-mediated susceptibility to NAFLD, whereas boosting it in wild-type liver cultures enhanced NAFLD development. Finally, we attributed this elevated IL-6/STAT3 activity in liver cultures carrying the rs738409 SNP to increased NF-κB activity.

CONCLUSIONS

Our study thus reveals a potential causal link between elevated IL-6/STAT3 activity and 148M-mediated susceptibility to NAFLD.

IMPACT AND IMPLICATIONS

An increasing number of genetic variants manifest in non-alcoholic fatty liver disease (NAFLD) development and progression; however, the underlying mechanisms remain elusive. To study these variants in human-relevant systems, we developed an induced pluripotent stem cell-derived multicellular liver culture and focused on a common genetic variant (i.e. rs738409 in PNPLA3). Our findings not only provide mechanistic insight, but also a potential therapeutic strategy for NAFLD driven by this genetic variant in PNPLA3. Our liver culture is therefore a useful platform for exploring genetic variants in NAFLD development.

Biofabrication of synthetic human liver tissue with advanced programmable functions

Advances in cellular engineering, as well as gene, and cell therapy, may be used to produce human tissues with programmable genetically enhanced functions designed to model and/or treat specific diseases. Fabrication of synthetic human liver tissue with these programmable functions has not been described. By generating human iPSCs with target gene expression controlled by a guide RNA-directed CRISPR-Cas9 synergistic-activation-mediator, we produced synthetic human liver tissues with programmable functions. Such iPSCs were guide-RNA-treated to enhance expression of the clinically relevant CYP3A4 and UGT1A1 genes, and after hepatocyte-directed differentiation, cells demonstrated enhanced functions compared to those found in primary human hepatocytes. We then generated human liver tissue with these synthetic human iPSC-derived hepatocytes (iHeps) and other non-parenchymal cells demonstrating advanced programmable functions. Fabrication of synthetic human liver tissue with modifiable functional genetic programs may be a useful tool for drug discovery, investigating biology, and potentially creating bioengineered organs with specialized functions.

Bioengineering Liver Organoids for Diseases Modelling and Transplantation

Organoids as three-dimension (3D) cellular organizations partially mimic the physiological functions and micro-architecture of native tissues and organs, holding great potential for clinical applications. Advances in the identification of essential factors including physical cues and biochemical signals for controlling organoid development have contributed to the success of growing liver organoids from liver tissue and stem/progenitor cells. However, to recapitulate the physiological properties and the architecture of a native liver, one has to generate liver organoids that contain all the major liver cell types in correct proportions and relative 3D locations as found in a native liver. Recent advances in stem-cell-, biomaterial- and engineering-based approaches have been incorporated into conventional organoid culture methods to facilitate the development of a more sophisticated liver organoid culture resembling a near to native mini-liver in a dish. However, a comprehensive review on the recent advancement in the bioengineering liver organoid is still lacking. Here, we review the current liver organoid systems, focusing on the construction of the liver organoid system with various cell sources, the roles of growth factors for engineering liver organoids, as well as the recent advances in the bioengineering liver organoid disease models and their biomedical applications.

From a Single Cell to a Whole Human Liver: Disease Modeling and Transplantation

Although the underlying cause may vary across countries and demographic groups, liver disease is a major cause of morbidity and mortality globally. Orthotopic liver transplantation is the only definitive treatment for liver failure but is limited by the lack of donor livers. The development of drugs that prevent the progression of liver disease and the generation of alternative liver constructs for transplantation could help alleviate the burden of liver disease. Bioengineered livers containing human induced pluripotent stem cell (iPSC)-derived liver cells are being utilized to study liver disease and to identify and test potential therapeutics. Moreover, bioengineered livers containing pig hepatocytes and endothelial cells have been shown to function and survive after transplantation into pig models of liver failure, providing preclinical evidence toward future clinical applications. Finally, bioengineered livers containing human iPSC-derived liver cells have been shown to function and survive after transplantation in rodents but require considerable optimization and testing prior to clinical use. In conclusion, bioengineered livers have emerged as a suitable tool for modeling liver diseases and as a promising alternative graft for clinical transplantation. The integration of novel technologies and techniques for the assembly and analysis of bioengineered livers will undoubtedly expand future applications in basic research and clinical transplantation.

Organoids in gastrointestinal diseases: from experimental models to clinical translation

We are entering an era of medicine where increasingly sophisticated data will be obtained from patients to determine proper diagnosis, predict outcomes and direct therapies. We predict that the most valuable data will be produced by systems that are highly dynamic in both time and space. Three-dimensional (3D) organoids are poised to be such a highly valuable system for a variety of gastrointestinal (GI) diseases. In the lab, organoids have emerged as powerful systems to model molecular and cellular processes orchestrating natural and pathophysiological human tissue formation in remarkable detail. Preclinical studies have impressively demonstrated that these organs-in-a-dish can be used to model immunological, neoplastic, metabolic or infectious GI disorders by taking advantage of patient-derived material. Technological breakthroughs now allow to study cellular communication and molecular mechanisms of interorgan cross-talk in health and disease including communication along for example, the gut-brain axis or gut-liver axis. Despite considerable success in culturing classical 3D organoids from various parts of the GI tract, some challenges remain to develop these systems to best help patients. Novel platforms such as organ-on-a-chip, engineered biomimetic systems including engineered organoids, micromanufacturing, bioprinting and enhanced rigour and reproducibility will open improved avenues for tissue engineering, as well as regenerative and personalised medicine. This review will highlight some of the established methods and also some exciting novel perspectives on organoids in the fields of gastroenterology. At present, this field is poised to move forward and impact many currently intractable GI diseases in the form of novel diagnostics and therapeutics.

Stem Cell Therapies for Chronic Liver Diseases: Progress and Challenges

Chronic liver diseases have become a significant health issue worldwide and urgently require the development of novel therapeutic approaches, in addition to liver transplantation. Recent clinical and preclinical studies have shown that cell-based therapeutic strategies may contribute to the improvement of chronic liver diseases and offer new therapeutic options to restore liver function through their roles in tissue impairment and immunomodulation. In this review, we summarize the current progress and analyze the challenges for different types of cell therapies used in the treatment of chronic liver diseases currently explored in clinical trials and preclinical studies in animal models. We also discuss some critical issues regarding the use of mesenchymal stem cells (MSCs, the most extensive cell source of stem cells), including therapeutic dosage, transfusion routine, and pharmacokinetics/pharmacodynamics (PK/PD) of transfused MSCs.

Dual-specificity Tyrosine Phosphorylation-regulated Kinase Inhibitor ID-8 Promotes Human Somatic Cell Reprogramming by Activating PDK4 Expression

BACKGROUND

Human induced pluripotent stem cells (hiPSCs) hold great potentials in disease modeling, drug screening and cell therapy. However, efficiency and costs of hiPSCs preparation still need to be improved.

METHODS

We screened the compounds that target signaling pathways, epigenetic modifications or metabolic-process regulation to replace the growth factors. After small molecule treatment, TRA-1-60, which is a cell surface antigen expressed by human embryonic stem cells (hESCs), staining was performed to quantify the efficiency of somatic cell reprogramming. Next, small molecule cocktail-induced ESCs or iPSCs were examined with pluripotent markers expression. Finally, Genome-wide gene expression profile was analyzed by RNA-seq to illustrate the mechanism of human somatic cell reprogramming.

RESULT

Here, we found that a dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) inhibitor ID-8 robustly enhanced human somatic cell reprogramming by upregulation of pyruvate dehydrogenase kinase 4 (PDK4) and activation of glycolysis. Furthermore, we identified a novel growth-factor-free hiPSC generation system using small molecules ID-8 (I) and TGFβ signal pathway agonist Kartogenin (K). Importantly, we developed IK medium combined with low-dose bFGF to support the long-term expansion of human pluripotent stem cells. IK-iPSCs showed pluripotency and normal karyotype.

CONCLUSIONS

Our studies may provide a novel growth-factor-free culture system to facilitate the generation of hiPSCs for multiple applications in regenerative medicine. In Brief Xu et at. found that a dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) inhibitor ID-8 robustly enhanced human somatic cell reprogramming by upregulation of PDK4 and activation of glycolysis. Furthermore, we established a novel growth-factor-free hiPSC generation system using small molecules ID-8/Kartogenin (IK). IK medium combined with Low-dose bFGF (IKB medium) supported the long-term expansion of human pluripotent stem cells. Highlights ID-8 Enhanced Reprogramming of Human Fibroblasts and Astrocytes Establishment of the Growth-factor-free Reprogramming System Using Small Molecule Compounds IK IKB Medium Maintained the Long-term Expansion of Human Pluripotent Stem Cells ID-8 Promoted Human Somatic Cell Reprogramming by Activating PDK4 Expression.

Transmembrane channel activity in human hepatocytes and cholangiocytes derived from induced pluripotent stem cells

The initial creation of human-induced pluripotent stem cells (iPSCs) set the foundation for the future of regenerative medicine. Human iPSCs can be differentiated into a variety of cell types in order to study normal and pathological molecular mechanisms. Currently, there are well-defined protocols for the differentiation, characterization, and establishment of functionality in human iPSC-derived hepatocytes (iHep) and iPSC-derived cholangiocytes (iCho). Electrophysiological study on chloride ion efflux channel activity in iHep and iCho cells has not been previously reported. We generated iHep and iCho cells and characterized them based on hepatocyte-specific and cholangiocyte-specific markers. The relevant transmembrane channels were selected: cystic fibrosis transmembrane conductance regulator, leucine rich repeat-containing 8 subunit A, and transmembrane member 16 subunit A. To measure the activity in these channels, we used whole-cell patch-clamp techniques with a standard intracellular and extracellular solution. Our iHep and iCho cells demonstrated definitive activity in the selected transmembrane channels, and this approach may become an important tool for investigating human liver biology of cholestatic diseases.

Dimethylglycine Sodium Salt Alleviates Intrauterine Growth Restriction-Induced Low Growth Performance, Redox Status Imbalance, and Hepatic Mitochondrial Dysfunction in Suckling Piglets

This study aimed to investigate the mechanism of redox status imbalance and hepatic mitochondrial dysfunction induced by intrauterine growth restriction (IUGR) and relieve this condition through dimethylglycine sodium salt (DMG-Na) supplementation during the suckling period. Thirty normal birth weight (NBW) and 30 IUGR newborns were selected from 20 sows. Briefly, 1 NBW and 1 IUGR newborn were obtained from each litter of 10 sows, and 10 NBW and 10 IUGR newborns were obtained. Additionally, 2 NBW and 2 IUGR newborns were obtained from each litter of another 10 sows, and 20 NBW newborns were allocated to the N [basic milk diets (BMDs)] and ND (BMDs+0.1% DMG-Na) groups. Furthermore, 20 IUGR newborns were assigned to the I (BMDs) and ID (BMDs+0.1% DMG-Na) groups. The results revealed that the growth performance, serum and hepatic redox status, and hepatic gene and protein expression levels were lower (P < 0.05) in the I group compared to the N group. Additionally, supplementation with DMG-Na (ND and ID groups) improved (P < 0.05) these parameters compared to the non-supplemented groups (N and I groups). In conclusion, the activity of Nrf2/SIRT1/PGC1α was inhibited in IUGR newborns, and this led to their hepatic dysfunctions. Supplementation with DMG-Na activated Nrf2/SIRT1/PGC1α in IUGR newborns, thereby improving their performance.

A Quantitative Systems Pharmacology Platform Reveals NAFLD Pathophysiological States and Targeting Strategies

Non-alcoholic fatty liver disease (NAFLD) has a high global prevalence with a heterogeneous and complex pathophysiology that presents barriers to traditional targeted therapeutic approaches. We describe an integrated quantitative systems pharmacology (QSP) platform that comprehensively and unbiasedly defines disease states, in contrast to just individual genes or pathways, that promote NAFLD progression. The QSP platform can be used to predict drugs that normalize these disease states and experimentally test predictions in a human liver acinus microphysiology system (LAMPS) that recapitulates key aspects of NAFLD. Analysis of a 182 patient-derived hepatic RNA-sequencing dataset generated 12 gene signatures mirroring these states. Screening against the LINCS L1000 database led to the identification of drugs predicted to revert these signatures and corresponding disease states. A proof-of-concept study in LAMPS demonstrated mitigation of steatosis, inflammation, and fibrosis, especially with drug combinations. Mechanistically, several structurally diverse drugs were predicted to interact with a subnetwork of nuclear receptors, including pregnane X receptor (PXR; NR1I2), that has evolved to respond to both xenobiotic and endogenous ligands and is intrinsic to NAFLD-associated transcription dysregulation. In conjunction with iPSC-derived cells, this platform has the potential for developing personalized NAFLD therapeutic strategies, informing disease mechanisms, and defining optimal cohorts of patients for clinical trials.

Interaction effect between NAFLD severity and high carbohydrate diet on gut microbiome alteration and hepatic de novo lipogenesis

Nonalcoholic fatty liver disease (NAFLD) is associated with high carbohydrate (HC) intake. We investigated whether the relationship between carbohydrate intake and NAFLD is mediated by interactions between gut microbial modulation, impaired insulin response, and hepatic de novo lipogenesis (DNL). Stool samples were collected from 204 Korean subjects with biopsy-proven NAFLD (n = 129) and without NAFLD (n = 75). The gut microbiome profiles were analyzed using 16S rRNA amplicon sequencing. Study subjects were grouped by the NAFLD activity score (NAS) and percentage energy intake from dietary carbohydrate. Hepatic DNL-related transcripts were also analyzed (n = 90). Data from the Korean healthy twin cohort (n = 682), a large sample of individuals without NAFLD, were used for comparison and validation. A HC diet rather than a low carbohydrate diet was associated with the altered gut microbiome diversity according to the NAS. Unlike individuals from the twin cohort without NAFLD, the abundances of Enterobacteriaceae and Ruminococcaceae were significantly different among the NAS subgroups in NAFLD subjects who consumed an HC diet. The addition of these two microbial families, along with Veillonellaceae, significantly improved the diagnostic performance of the predictive model, which was based on the body mass index, age, and sex to predict nonalcoholic steatohepatitis in the HC group. In the HC group, two crucial regulators of DNL (SIRT1 and SREBF2) were differentially expressed among the NAS subgroups. In particular, kernel causality analysis revealed a causal effect of the abundance of Enterobacteriaceae on SREBF2 upregulation and of the surrogate markers of insulin resistance on NAFLD activity in the HC group. Consuming an HC diet is associated with alteration in the gut microbiome, impaired glucose homeostasis, and upregulation of hepatic DNL genes, altogether contributing to NAFLD pathogenesis.

Expression and mechanism of microRNA 195 in diabetic retinopathy

We aimed to explore the role of microRNA 195 (miR-195) in diabetic retinopathy (DR). From January 2019 to July 2020, 50 patients with DR undergoing vitrectomy and 40 patients with idiopathic macular holes undergoing vitrectomy were selected as the observation group (OG) and control group (CG), respectively. The mRNA and protein expression levels of miR-195, SIRT1, BAX, and BCL-2 were detected in the retinal tissues obtained from the two groups during surgery. In addition, human retinal endothelial cells and human dermal microvascular endothelial cells were cultured in a high-glucose environment to detect the targeted relationship between miR-195 and SIRT1; determine the mRNA and protein expression levels of SIRT1, BAX, and BCL-2 after miR-195 knockdown; and assess the levels of cell proliferation and apoptosis. In OG, the mRNA and protein expression levels of miR-195 and BAX were high, whereas those of BCL-2 and SIRT1 were low. Moreover, we detected a targeted relationship between miR-195 and SIRT1. Conversely, miR-195 knockdown led to the downregulation of the mRNA and protein expression levels of BAX and the upregulation of the mRNA and protein expression levels of SIRT1 and BCL-2 as well as improvement in cell growth and a decrease in the apoptosis rate. miR-195 is overexpressed in DR, and its targeted relationship with SIRT1 inhibits the growth of cells in the retina and accelerates apoptosis.

Responsiveness of PNPLA3 and lipid-related transcription factors is dependent upon fatty acid profile in primary bovine hepatocytes

Knockdown of patatin-like phospholipase domain-containing protein 3 (PNPLA3) increased triglycerides (TG) in primary bovine hepatocytes, suggesting that PNPLA3 plays a causal role in hepatic TG clearing. In vivo, PNPLA3 abundance across the periparturient period is inversely related to hepatic TG accumulation and circulating fatty acid (FA) concentrations. The purpose of this research was to determine if PNPLA3, as well as other lipases, transcription factors, or FA-mediated genes, are regulated by FA mimicking liver lipid accumulation (ACCUM) and liver lipid clearing (RECOV) or singular FA physiologically found in dairy cows at 0.5 mM of circulating RECOV (iRECOV). Abundance of PNPLA3 tended to decrease with ACCUM and increased quadratically with RECOV (P ≤ 0.10), differing from PNPLA3 expression, but consistent with previous in vivo research. Adipose TG lipase abundance, but not other lipase abundances, was quadratically responsive to both ACCUM and RECOV (P ≤ 0.005). Abundance of PNPLA3 and SREBP1c and expression of LXRA responded similarly to iRECOV, with C18:0 tending to decrease abundance (P ≤ 0.07). Results indicate that bovine PNPLA3 is translationally regulated by FA and although a LXRA-SREBP1c pathway mediation is possible, the mechanism warrants further investigation.

Improving human mesenchymal stem cell-derived hepatic cell energy metabolism by manipulating glucose homeostasis and glucocorticoid signaling

INTRODUCTION

The development of reliable hepatic in vitro models may provide insights into disease mechanisms, linking hepatocyte dysmetabolism and related pathologies. However, several of the existing models depend on using high concentrations of hepatocyte differentiation-promoting compounds, namely glucose, insulin, and dexamethasone, which is among the reasons that have hampered their use for modeling metabolism-related diseases. This work focused on modulating glucose homeostasis and glucocorticoid concentration to improve the suitability of a mesenchymal stem-cell (MSC)-derived hepatocyte-like cell (HLC) human model for studying hepatic insulin action and disease modeling.

METHODS

We have investigated the role of insulin, glucose and dexamethasone on mitochondrial function, insulin signaling and carbohydrate metabolism, namely AKT phosphorylation, glycogen storage ability, glycolysis and gluconeogenesis, as well as fatty acid oxidation and bile acid metabolism gene expression in HLCs. In addition, we evaluated cell morphological features, albumin and urea production, the presence of hepatic-specific markers, biotransformation ability and mitochondrial function.

RESULTS

Using glucose, insulin and dexamethasone levels close to physiological concentrations improved insulin responsiveness in HLCs, as demonstrated by AKT phosphorylation, upregulation of glycolysis and downregulation of Irs2 and gluconeogenesis and fatty acid oxidation pathways. Ammonia detoxification, EROD and UGT activities and sensitivity to paracetamol cytotoxicity were also enhanced under more physiologically relevant conditions.

CONCLUSION

HLCs kept under reduced concentrations of glucose, insulin and dexamethasone presented an improved hepatic phenotype and insulin sensitivity demonstrating superior potential as an in vitro platform for modeling energy metabolism-related disorders, namely for the investigation of the insulin signaling pathway.

Induced Pluripotent Stem Cells for the Treatment of Liver Diseases: Novel Concepts

Millions of people worldwide with incurable liver disease die because of inadequate treatment options and limited availability of donor organs for liver transplantation. Regenerative medicine as an innovative approach to repairing and replacing cells, tissues, and organs is undergoing a major revolution due to the unprecedented need for organs for patients around the world. Induced pluripotent stem cells (iPSCs) have been widely studied in the field of liver regeneration and are considered to be the most promising candidate therapies. This review will conclude the current state of efforts to derive human iPSCs for potential use in the modeling and treatment of liver disease.

Cell Models and Omics Techniques for the Study of Nonalcoholic Fatty Liver Disease: Focusing on Stem Cell-Derived Cell Models

Nonalcoholic fatty liver disease (NAFLD) is now the leading cause of chronic liver disease in western countries. The molecular mechanisms leading to NAFLD are only partially understood, and effective therapeutic interventions are clearly needed. Therefore, preclinical research is required to improve knowledge about NAFLD physiopathology and to identify new therapeutic targets. Primary human hepatocytes, human hepatic cell lines, and human stem cell-derived hepatocyte-like cells exhibit different hepatic phenotypes and have been widely used for studying NAFLD pathogenesis. In this paper, apart from employing the different in vitro cell models for the in vitro assessment of NAFLD, we also reviewed other approaches (metabolomics, transcriptomics, and high-content screening). We aimed to summarize the characteristics of different cell types and methods and to discuss their major advantages and disadvantages for NAFLD modeling.

Modeling nonalcoholic fatty liver disease on a liver lobule chip with dual blood supply

Nonalcoholic fatty liver disease (NAFLD) has emerged as a public health concern. To date, the mechanism of NAFLD progression remains unclear, and pharmacological treatment options are scarce. Traditional animal NAFLD models are limited in helping address these problems due to interspecies differences. Liver chips are promising for modeling NAFLD. However, pre-existing liver chips cannot reproduce complex physicochemical microenvironments of the liver effectively; thus, NAFLD modeling based on these chips is incomplete. Herein, we develop a biomimetic liver lobule chip (LC) and then establish a more accurate on-chip NAFLD model. The self-developed LC achieves dual blood supply through the designed hepatic portal vein and hepatic artery and the microtissue cultured on the LC forms multiple structures similar to in vivo liver. Based on the LC, NAFLD is modeled. Steatosis is successfully induced and more importantly, changing lipid zonation in a liver lobule with the progression of NAFLD is demonstrated for the first time on a microfluidic chip. In addition, the application of the induced NAFLD model has been preliminarily demonstrated in the prevention and reversibility of promising drugs. This study provides a promising platform to understand NAFLD progression and identify drugs for treating NAFLD. STATEMENT OF SIGNIFICANCE: Liver chips are promising for modeling nonalcoholic fatty liver disease. However, on-chip replicating liver physicochemical microenvironments is still a challenge. Herein, we developed a liver lobule chip with dual blood supply, achieving self-organized liver microtissue that is similar to in vivo tissue. Based on the chip, we successfully modeled NAFLD under physiologically differentiated nutrient supplies. For the first time, the changing lipid zonation in a single liver lobule with the early-stage progression of NAFLD was demonstrated on a liver chip. This study provides a promising platform for modeling liver-related diseases.

Human Pluripotent Stem Cell-Derived Hepatocyte-Like Cells and Organoids for Liver Disease and Therapy

Liver disease is a global health issue that has caused an economic burden worldwide. Organ transplantation is the only effective therapy for end-stage liver disease; however, it has been hampered by a shortage of donors. Human pluripotent stem cells (hPSCs) have been widely used for studying liver biology and pathology as well as facilitating the development of alternative therapies. hPSCs can differentiate into multiple types of cells, which enables the generation of various models that can be applied to investigate and recapitulate a range of biological activities in vitro. Here, we summarize the recent development of hPSC-derived hepatocytes and their applications in disease modeling, cell therapy, and drug discovery. We also discuss the advantages and limitations of these applications and critical challenges for further development.

CRISPR-Cas9-mediated reactivation of the uricase pseudogene in human cells prevents acute hyperuricemia

The utility of CRISPR-Cas9 to repair or reverse diseased states that arise from recent genetic mutations in the human genome is now widely appreciated. The use of CRISPR to "design" the outcomes of biology is challenged by both specialized ethicists and the general public. Less of a focus, however, is the ability of CRISPR to provide metabolic supplements or prophylactic molecules that improve long-term human health by overwriting ancient evolutionary events. Here, we use CRISPR to genomically integrate a functional uricase gene that encodes an enzymatically active protein into the human genome. These uricase-producing cells are able to reduce or even eliminate high concentrations of exogenous uric acid despite the enzyme being localized to peroxisomes. Our evolutionary engineered cells represent the first instance of the primate ape lineage expressing a functional uricase encoded in the genome within the last 20 million years. We anticipate that human cells expressing uricase will help prevent hyperuricemia (including gout) as well as hypertension and will help protect against fatty liver disease in the future.

Emerging liver organoid platforms and technologies

Building human organs in a dish has been a long term goal of researchers in pursue of physiologically relevant models of human disease and for replacement of worn out and diseased organs. The liver has been an organ of interest for its central role in regulating body homeostasis as well as drug metabolism. An accurate liver replica should contain the multiple cell types found in the organ and these cells should be spatially organized to resemble tissue structures. More importantly, the in vitro model should recapitulate cellular and tissue level functions. Progress in cell culture techniques and bioengineering approaches have greatly accelerated the development of advance 3-dimensional (3D) cellular models commonly referred to as liver organoids. These 3D models described range from single to multiple cell type containing cultures with diverse applications from establishing patient-specific liver cells to modeling of chronic liver diseases and regenerative therapy. Each organoid platform is advantageous for specific applications and presents its own limitations. This review aims to provide a comprehensive summary of major liver organoid platforms and technologies developed for diverse applications.

Is HSD17B13 Genetic Variant a Protector for Liver Dysfunction? Future Perspective as a Potential Therapeutic Target

As diet and lifestyle have changed, fatty liver disease (FLD) has become more and more prevalent. Many genetic risk factors, such as variants of PNPLA3, TM6SF2, GCKR, and MBOAT7, have previously been uncovered via genome wide association studies (GWAS) to be associated with FLD. In 2018, a genetic variant (rs72613567, T > TA) of hydroxysteroid 17-β dehydrogenase family 13 (HSD17B13) was first associated with a lower risk of developing alcoholic liver disease and non-alcoholic fatty liver disease (NAFLD) in minor allele carriers. Other HSD17B13 variants were also later linked with either lower inflammation scores among NAFLD patients or protection against NAFLD (rs6834314, A > G and rs9992651, G > A) respectively. HSD17B13 is a lipid droplet-associated protein, but its function is still ambiguous. Compared to the other genetic variants that increase risk for FLD, HSD17B13 variants serve a protective role, making this gene a potential therapeutic target. However, the mechanism by which these variants reduce the risk of developing FLD is still unclear. Because studies in cell lines and mouse models have produced conflicting results, human liver tissue modeling using induced pluripotent stem cells may be the best way to move forward and solve this mystery.

Quantifying the progression of non-alcoholic fatty liver disease in human biomimetic liver microphysiology systems with fluorescent protein biosensors

Metabolic syndrome is a complex disease that involves multiple organ systems including a critical role for the liver. Non-alcoholic fatty liver disease (NAFLD) is a key component of the metabolic syndrome and fatty liver is linked to a range of metabolic dysfunctions that occur in approximately 25% of the population. A panel of experts recently agreed that the acronym, NAFLD, did not properly characterize this heterogeneous disease given the associated metabolic abnormalities such as type 2 diabetes mellitus (T2D), obesity, and hypertension. Therefore, metabolic dysfunction-associated fatty liver disease (MAFLD) has been proposed as the new term to cover the heterogeneity identified in the NAFLD patient population. Although many rodent models of NAFLD/NASH have been developed, they do not recapitulate the full disease spectrum in patients. Therefore, a platform has evolved initially focused on human biomimetic liver microphysiology systems that integrates fluorescent protein biosensors along with other key metrics, the microphysiology systems database, and quantitative systems pharmacology. Quantitative systems pharmacology is being applied to investigate the mechanisms of NAFLD/MAFLD progression to select molecular targets for fluorescent protein biosensors, to integrate computational and experimental methods to predict drugs for repurposing, and to facilitate novel drug development. Fluorescent protein biosensors are critical components of the platform since they enable monitoring of the pathophysiology of disease progression by defining and quantifying the temporal and spatial dynamics of protein functions in the biosensor cells, and serve as minimally invasive biomarkers of the physiological state of the microphysiology system experimental disease models. Here, we summarize the progress in developing human microphysiology system disease models of NAFLD/MAFLD from several laboratories, developing fluorescent protein biosensors to monitor and to measure NAFLD/MAFLD disease progression and implementation of quantitative systems pharmacology with the goal of repurposing drugs and guiding the creation of novel therapeutics.

Assembly and Function of a Bioengineered Human Liver for Transplantation Generated Solely from Induced Pluripotent Stem Cells

The availability of an autologous transplantable auxiliary liver would dramatically affect the treatment of liver disease. Assembly and function in vivo of a bioengineered human liver derived from induced pluripotent stem cells (iPSCs) has not been previously described. By improving methods for liver decellularization, recellularization, and differentiation of different liver cellular lineages of human iPSCs in an organ-like environment, we generated functional engineered human mini livers and performed transplantation in a rat model. Whereas previous studies recellularized liver scaffolds largely with rodent hepatocytes, we repopulated not only the parenchyma with human iPSC-hepatocytes but also the vascular system with human iPS-endothelial cells, and the bile duct network with human iPSC-biliary epithelial cells. The regenerated human iPSC-derived mini liver containing multiple cell types was tested in vivo and remained functional for 4 days after auxiliary liver transplantation in immunocompromised, engineered (IL2rg^-/-) rats.

Therapeutic effect of oxyberberine on obese non-alcoholic fatty liver disease rats

BACKGROUND

Berberine (BBR) has been widely used to treat non-alcoholic fatty liver disease (NAFLD). The metabolites of BBR were believed to contribute significantly to its pharmacological effects. Oxyberberine (OBB), a gut microbiota-mediated oxidative metabolite of BBR, has been firstly identified in our recent work.

PURPOSE

Here, we aimed to comparatively investigate the anti-NAFLD properties of OBB and BBR.

METHODS

The anti-NAFLD effect was evaluated in high-fat diet-induced obese NAFLD rats with biochemical/ELISA tests and histological staining. The related gene and protein expressions were detected by qRT-PCR and Western blotting respectively. Molecular docking and dynamic simulation were also performed to provide further insight.

RESULTS

Results indicated OBB remarkably and dose-dependently attenuated the clinical manifestations of NAFLD, which (100 mg/kg) achieved similar therapeutic effect to metformin (300 mg/kg) and was superior to BBR of the same dose. OBB significantly inhibited aberrant phosphorylation of IRS-1 and up-regulated the downstream protein expression and phosphorylation (PI3K, p-Akt/Akt and p-GSK-3β/GSK-3β) to improve hepatic insulin signal transduction. Meanwhile, OBB treatment remarkably alleviated inflammation via down-regulating the mRNA expression of MCP-1, Cd68, Nos2, Cd11c, while enhancing Arg1 mRNA expression in white adipose tissue. Moreover, OBB exhibited closer affinity with AMPK in silicon and superior hyperphosphorylation of AMPK in vivo, leading to increased ACC mRNA expression in liver and UCP-1 protein expression in adipose tissue.

CONCLUSION

Taken together, compared with BBR, OBB was more capable of maintaining lipid homeostasis between liver and WAT via attenuating hepatic insulin pathway and adipocyte inflammation, which was associated with its property of superior AMPK activator.

Synthetic human livers for modeling metabolic diseases

PURPOSE OF REVIEW

In this review, we will explore recent advances in human induced pluripotent stem cell (iPSC)-based modeling of metabolic liver disease and biofabrication of synthetic human liver tissue while also discussing the emerging concept of synthetic biology to generate more physiologically relevant liver disease models.

RECENT FINDING

iPSC-based platforms have facilitated the study of underlying cellular mechanisms and potential therapeutic strategies for a number of metabolic liver diseases. Concurrently, rapid progress in biofabrication and gene editing technologies have led to the generation of human hepatic tissue that more closely mimic the complexity of the liver.

SUMMARY

iPSC-based liver tissue is rapidly becoming available for modeling liver physiology due to its ability to recapitulate the complex three-dimensional architecture of the liver and recapitulate interactions between the different cell types and their surroundings. These mini livers have also been used to recapitulate liver disease pathways using the tools of synthetic biology, such as gene editing, to control gene circuits. Further development in this field will undoubtedly bolster future investigations not only in disease modeling and basic research, but also in personalized medicine and autologous transplantation.

Mechanisms and disease consequences of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide. Its more advanced subtype, nonalcoholic steatohepatitis (NASH), connotes progressive liver injury that can lead to cirrhosis and hepatocellular carcinoma. Here we provide an in-depth discussion of the underlying pathogenetic mechanisms that lead to progressive liver injury, including the metabolic origins of NAFLD, the effect of NAFLD on hepatic glucose and lipid metabolism, bile acid toxicity, macrophage dysfunction, and hepatic stellate cell activation, and consider the role of genetic, epigenetic, and environmental factors that promote fibrosis progression and risk of hepatocellular carcinoma in NASH.

Human biomimetic liver microphysiology systems in drug development and precision medicine

Microphysiology systems (MPS), also called organs-on-chips and tissue chips, are miniaturized functional units of organs constructed with multiple cell types under a variety of physical and biochemical environmental cues that complement animal models as part of a new paradigm of drug discovery and development. Biomimetic human liver MPS have evolved from simpler 2D cell models, spheroids and organoids to address the increasing need to understand patient-specific mechanisms of complex and rare diseases, the response to therapeutic treatments, and the absorption, distribution, metabolism, excretion and toxicity of potential therapeutics. The parallel development and application of transdisciplinary technologies, including microfluidic devices, bioprinting, engineered matrix materials, defined physiological and pathophysiological media, patient-derived primary cells, and pluripotent stem cells as well as synthetic biology to engineer cell genes and functions, have created the potential to produce patient-specific, biomimetic MPS for detailed mechanistic studies. It is projected that success in the development and maturation of patient-derived MPS with known genotypes and fully matured adult phenotypes will lead to advanced applications in precision medicine. In this Review, we examine human biomimetic liver MPS that are designed to recapitulate the liver acinus structure and functions to enhance our knowledge of the mechanisms of disease progression and of the absorption, distribution, metabolism, excretion and toxicity of therapeutic candidates and drugs as well as to evaluate their mechanisms of action and their application in precision medicine and preclinical trials.

Human liver model systems in a dish

The human adult liver has a multi-cellular structure consisting of large lobes subdivided into lobules containing portal triads and hepatic cords lined by specialized blood vessels. Vital hepatic functions include filtering blood, metabolizing drugs, and production of bile and blood plasma proteins like albumin, among many other functions, which are generally dependent on the location or zone in which the hepatocyte resides in the liver. Due to the liver's intricate structure, there are many challenges to design differentiation protocols to generate more mature functional hepatocytes from human stem cells and maintain the long-term viability and functionality of primary hepatocytes. To this end, recent advancements in three-dimensional (3D) stem cell culture have accelerated the generation of a human miniature liver system, also known as liver organoids, with polarized epithelial cells, supportive cell types and extra-cellular matrix deposition by translating knowledge gained in studies of animal organogenesis and regeneration. To facilitate the efforts to study human development and disease using in vitro hepatic models, a thorough understanding of state-of-art protocols and underlying rationales is essential. Here, we review rapidly evolving 3D liver models, mainly focusing on organoid models differentiated from human cells.

A Perfusion Bioreactor for Longitudinal Monitoring of Bioengineered Liver Constructs

In the field of in vitro liver disease models, decellularised organ scaffolds maintain the original biomechanical and biological properties of the extracellular matrix and are established supports for in vitro cell culture. However, tissue engineering approaches based on whole organ decellularized scaffolds are hampered by the scarcity of appropriate bioreactors that provide controlled 3D culture conditions. Novel specific bioreactors are needed to support long-term culture of bioengineered constructs allowing non-invasive longitudinal monitoring. Here, we designed and validated a specific bioreactor for long-term 3D culture of whole liver constructs. Whole liver scaffolds were generated by perfusion decellularisation of rat livers. Scaffolds were seeded with Luc⁺HepG2 and primary human hepatocytes and cultured in static or dynamic conditions using the custom-made bioreactor. The bioreactor included a syringe pump, for continuous unidirectional flow, and a circuit built to allow non-invasive monitoring of culture parameters and media sampling. The bioreactor allowed non-invasive analysis of cell viability, distribution, and function of Luc⁺HepG2-bioengineered livers cultured for up to 11 days. Constructs cultured in dynamic conditions in the bioreactor showed significantly higher cell viability, measured with bioluminescence, distribution, and functionality (determined by albumin production and expression of CYP enzymes) in comparison to static culture conditions. Finally, our bioreactor supports primary human hepatocyte viability and function for up to 30 days, when seeded in the whole liver scaffolds. Overall, our novel bioreactor is capable of supporting cell survival and metabolism and is suitable for liver tissue engineering for the development of 3D liver disease models.

Nanoparticle-Mediated Lipid Metabolic Reprogramming of T Cells in Tumor Microenvironments for Immunometabolic Therapy

aCD3/F/AN, anti-CD3e f(ab')2 fragment-modified and fenofibrate-encapsulated amphiphilic nanoparticle, reprogrammed mitochondrial lipid metabolism of T cells. aCD3/F/AN specifically activated T cells in glucose-deficient conditions mimicking tumor microenvironment, and exerted an effector killing effect against tumor cells. In vivo treatment with aCD3/F/AN increased T cell infiltration, cytokine production, and prevented tumor growth. We report the activation of anticancer effector functions of T cells through nanoparticle-induced lipid metabolic reprogramming. Fenofibrate was encapsulated in amphiphilic polygamma glutamic acid-based nanoparticles (F/ANs), and the surfaces of F/ANs were modified with an anti-CD3e f(ab')2 fragment, yielding aCD3/F/ANs. An in vitro study reveals enhanced delivery of aCD3/F/ANs to T cells compared with plain F/ANs. aCD3/F/AN-treated T cells exhibited clear mitochondrial cristae, a higher membrane potential, and a greater mitochondrial oxygen consumption rate under glucose-deficient conditions compared with T cells treated with other nanoparticle preparations. Peroxisome proliferator-activated receptor-α and downstream fatty acid metabolism-related genes are expressed to a greater extent in aCD3/F/AN-treated T cells. Activation of fatty acid metabolism by aCD3/F/ANs supports the proliferation of T cells in a glucose-deficient environment mimicking the tumor microenvironment. Real-time video recordings show that aCD3/F/AN-treated T cells exerted an effector killing effect against B16F10 melanoma cells. In vivo administration of aCD3/F/ANs can increase infiltration of T cells into tumor tissues. The treatment of tumor-bearing mice with aCD3/F/ANs enhances production of various cytokines in tumor tissues and prevented tumor growth. Our findings suggest the potential of nanotechnology-enabled reprogramming of lipid metabolism in T cells as a new modality of immunometabolic therapy.