A 3D Human Liver Model of Nonalcoholic Steatohepatitis

Bioinspired Bioinks for the Fabrication of Chemomechanically Relevant Standalone Disease Models of Hepatic Steatosis

Hepatotoxicity-related issues are poorly predicted during preclinical experimentation, as its relevance is limited by the inadequacy to screen all the non-physiological subclasses of the population. These pitfalls can be solved by implementing complex in vitro models of hepatic physiology and pathologies in the preclinical phase. To produce these platforms, extrusion-based bioprinting is focused on, since it allows to manufacture tridimensional cell-laden constructs with controlled geometries, in a high-throughput manner. Different bioinks, whose formulation is tailored to mimic the chemomechanical environment of hepatic steatosis, the most prevalent hepatic disorder worldwide, are proposed. Internally crosslinked alginate hydrogels are chosen as structural components of the inks. Their viscoelastic properties (G' = 512-730 Pa and G″ = 94-276 Pa, depending on frequency) are tuned to mimic those of steatotic liver tissue. Porcine hepatic ECM is introduced as a relevant biochemical cue. Sodium oleate is added to recall the accumulation of lipids in the tissue. Downstream analyses on 14-layered bioprinted structures cultured for 10 days reveal the establishment of steatotic-like features (intracellular lipid vesicles, viability decrease up to ≈50%) without needing external conditionings. The presented bioinks are thus suitable to fabricate complex models of hepatic steatosis to be implemented in a high-throughput experimental frame.

Hepatic organoids move from adolescence to maturity

Since organoids were developed 15 years ago, they are now in their adolescence as a research tool. The ability to generate 'tissue in a dish' has created enormous opportunities for biomedical research. We examine the contributions that hepatic organoids have made to three areas of liver research: as a source of cells and tissue for basic research, for drug discovery and drug safety testing, and for understanding disease pathobiology. We discuss the features that enable hepatic organoids to provide useful models for human liver diseases and identify four types of advances that will enable them to become a mature (i.e., adult) research tool over the next 5 years. During this period, advances in single-cell RNA sequencing and CRISPR technologies coupled with improved hepatic organoid methodology, which enables them to have a wider range of cell types that are present in liver and to be grown in microwells, will generate discoveries that will dramatically advance our understanding of liver development and the pathogenesis of liver diseases. It will generate also new approaches for treating liver fibrosis, which remains a major public health problem with few treatment options.

A comprehensive review on 3D tissue models: Biofabrication technologies and preclinical applications

The limitations of traditional two-dimensional (2D) cultures and animal testing, when it comes to precisely foreseeing the toxicity and clinical effectiveness of potential drug candidates, have resulted in a notable increase in the rate of failure during the process of drug discovery and development. Three-dimensional (3D) in-vitro models have arisen as substitute platforms with the capacity to accurately depict in-vivo conditions and increasing the predictivity of clinical effects and toxicity of drug candidates. It has been found that 3D models can accurately represent complex tissue structure of human body and can be used for a wide range of disease modeling purposes. Recently, substantial progress in biomedicine, materials and engineering have been made to fabricate various 3D in-vitro models, which have been exhibited better disease progression predictivity and drug effects than convention models, suggesting a promising direction in pharmaceutics. This comprehensive review highlights the recent developments in 3D in-vitro tissue models for preclinical applications including drug screening and disease modeling targeting multiple organs and tissues, like liver, bone, gastrointestinal tract, kidney, heart, brain, and cartilage. We discuss current strategies for fabricating 3D models for specific organs with their strengths and pitfalls. We expand future considerations for establishing a physiologically-relevant microenvironment for growing 3D models and also provide readers with a perspective on intellectual property, industry, and regulatory landscape.

The Material World of 3D-Bioprinted and Microfluidic-Chip Models of Human Liver Fibrosis

Biomaterials are extensively used to mimic cell-matrix interactions, which are essential for cell growth, function, and differentiation. This is particularly relevant when developing in vitro disease models of organs rich in extracellular matrix, like the liver. Liver disease involves a chronic wound-healing response with formation of scar tissue known as fibrosis. At early stages, liver disease can be reverted, but as disease progresses, reversion is no longer possible, and there is no cure. Research for new therapies is hampered by the lack of adequate models that replicate the mechanical properties and biochemical stimuli present in the fibrotic liver. Fibrosis is associated with changes in the composition of the extracellular matrix that directly influence cell behavior. Biomaterials could play an essential role in better emulating the disease microenvironment. In this paper, the recent and cutting-edge biomaterials used for creating in vitro models of human liver fibrosis are revised, in combination with cells, bioprinting, and/or microfluidics. These technologies have been instrumental to replicate the intricate structure of the unhealthy tissue and promote medium perfusion that improves cell growth and function, respectively. A comprehensive analysis of the impact of material hints and cell-material interactions in a tridimensional context is provided.

Emerging novel targets for nonalcoholic fatty liver disease treatment: Evidence from recent basic studies

Nonalcoholic fatty liver disease (NAFLD), a leading chronic disease worldwide, affects approximately a quarter of the global population. Nonalcoholic steatohepatitis (NASH) is an advanced form of NAFLD and is more likely to progress to liver fibrosis than simple steatosis. NASH is also identified as the most rapidly growing cause of hepatocellular carcinoma. Although in the past decade, several phase II/III clinical trials have shown promising results in the use of novel drugs targeting lipid synthase, farnesoid X receptor signaling, peroxisome proliferator-activated receptor signaling, hepatocellular injury, and inflammatory signaling, proven pharmaceutical agents to treat NASH are still lacking. Thus, continuous exploration of the mechanism underlying the pathogenesis of NAFLD and the identification of novel therapeutic targets remain urgent tasks in the field. In the current review, we summarize studies reported in recent years that not only provide new insights into the mechanisms of NAFLD development but also explore the possibility of treating NAFLD by targeting newly identified signaling pathways. We also discuss evidence focusing on the intrahepatic targets involved in the pathogenesis of NAFLD as well as extrahepatic targets affecting liver metabolism and function.

Multimodal NASH prognosis using 3D imaging flow cytometry and artificial intelligence to characterize liver cells

To improve the understanding of the complex biological process underlying the development of non-alcoholic steatohepatitis (NASH), 3D imaging flow cytometry (3D-IFC) with transmission and side-scattered images were used to characterize hepatic stellate cell (HSC) and liver endothelial cell (LEC) morphology at single-cell resolution. In this study, HSC and LEC were obtained from biopsy-proven NASH subjects with early-stage NASH (F2-F3) and healthy controls. Here, we applied single-cell imaging and 3D digital reconstructions of healthy and diseased cells to analyze a spatially resolved set of morphometric cellular and texture parameters that showed regression with disease progression. By developing a customized autoencoder convolutional neural network (CNN) based on label-free cell transmission and side scattering images obtained from a 3D imaging flow cytometer, we demonstrated key regulated cell types involved in the development of NASH and cell classification performance superior to conventional machine learning methods.

Bioengineered Cystinotic Kidney Tubules Recapitulate a Nephropathic Phenotype

Nephropathic cystinosis is a rare and severe disease caused by disruptions in the CTNS gene. Cystinosis is characterized by lysosomal cystine accumulation, vesicle trafficking impairment, oxidative stress, and apoptosis. Additionally, cystinotic patients exhibit weakening and leakage of the proximal tubular segment of the nephrons, leading to renal Fanconi syndrome and kidney failure early in life. Current in vitro cystinotic models cannot recapitulate all clinical features of the disease which limits their translational value. Therefore, the development of novel, complex in vitro models that better mimic the disease and exhibit characteristics not compatible with 2-dimensional cell culture is of crucial importance for novel therapies development. In this study, we developed a 3-dimensional bioengineered model of nephropathic cystinosis by culturing conditionally immortalized proximal tubule epithelial cells (ciPTECs) on hollow fiber membranes (HFM). Cystinotic kidney tubules showed lysosomal cystine accumulation, increased autophagy and vesicle trafficking deterioration, the impairment of several metabolic pathways, and the disruption of the epithelial monolayer tightness as compared to control kidney tubules. In particular, the loss of monolayer organization and leakage could be mimicked with the use of the cystinotic kidney tubules, which has not been possible before, using the standard 2-dimensional cell culture. Overall, bioengineered cystinotic kidney tubules recapitulate better the nephropathic phenotype at a molecular, structural, and functional proximal tubule level compared to 2-dimensional cell cultures.

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.

A 3D primary human cell-based in vitro model of non-alcoholic steatohepatitis for efficacy testing of clinical drug candidates

Non-alcoholic steatohepatitis (NASH) is a progressive and severe liver disease, characterized by lipid accumulation, inflammation, and downstream fibrosis. Despite its increasing prevalence, there is no approved treatment yet available for patients. This has been at least partially due to the lack of predictive preclinical models for studying this complex disease. Here, we present a 3D in vitro microtissue model that uses spheroidal, scaffold free co-culture of primary human hepatocytes, Kupffer cells, liver endothelial cells and hepatic stellate cells. Upon exposure to defined and clinically relevant lipotoxic and inflammatory stimuli, these microtissues develop key pathophysiological features of NASH within 10 days, including an increase of intracellular triglyceride content and lipids, and release of pro-inflammatory cytokines. Furthermore, fibrosis was evident through release of procollagen type I, and increased deposition of extracellular collagen fibers. Whole transcriptome analysis revealed changes in the regulation of pathways associated with NASH, such as lipid metabolism, inflammation and collagen processing. Importantly, treatment with anti-NASH drug candidates (Selonsertib and Firsocostat) decreased the measured specific disease parameter, in accordance with clinical observations. These drug treatments also significantly changed the gene expression patterns of the microtissues, thus providing mechanisms of action and revealing therapeutic potential. In summary, this human NASH model represents a promising drug discovery tool for understanding the underlying complex mechanisms in NASH, evaluating efficacy of anti-NASH drug candidates and identifying new approaches for therapeutic interventions.